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Mobile Electronics Australia Specialist Dealer

Listed below are some of the more common questions that Fhrx Studio's is asked during day to day operations.

Why should I employ Fhrx Studio's to install my system?

With many people being burned by shoddy workmanship and corner cutting, we strive to produce the best install possible for any desired budget. For info about us and more reasons to come see us for your next install, Click here.

Do you mail order equipment?

Yes we certainly do! We're always more than happy to take orders via email and phone. Payment can be made by either credit card, cheque, cash or direct debit (internet transfer). Upon clearance / receipt of payment you're issued with a receipt. Items are shipped via Australia Post and are registered and insured.

We are also more than happy to ship to New Zealand. Note; due to some of our agreements with certain distributors and companies we are forbidden to ship certain brands overseas. If in doubt, please ask as these conditions constantly change.

How does your 'rewards' scheme work?

Put simply, we're more than happy to reward friends and customers that get us additional work. If you get us a job or if your name is mentioned as the referrer for a job that comes in the door, we'll rebate you 3% of that particular job total. It is as simply as that. For example; if your best mate gets $10000 worth of work done with Fhrx Studios and names you as the referrer, then you'll get $300 cash back.

Do you offer gift vouchers?

We certainly do. If you're stuck for ideas on what present to give a friend or relative how about giving them a Fhrx Studio's gift voucher? We can supply gift vouchers for any value and can even post them fully wrapped to people if that suits you better.

What's the best system I can get for XXXX dollars?

We're constantly asked what the best systems are for various budgets. The short answer is that there is no right or wrong answer to this question. Everyones ears and tastes are different so the best thing to do is audition as many products as possible and chose based on what you like the most. Listed below are various product most commonly chosen by our customers. These are also among the products that win the most competitions in Australia. However, there are a few things to remember:

  1. The prices listed are full retail and do not include labour charges at all. The more complex and intricate your system design becomes, the higher the labour costs will become.
  2. These systems are based on the posters personal aural tastes. This may radically change depending on your own tastes.
  3. This is a ROUGH guide. It is possible that your personal choices will differ from the ones listed below.
  4. We have listed 12" subwoofers for these lists. Subwoofer size choice may differ depending on your situation and desires.
  5. These systems are basic sound quality orientated systems and therefore only utilise a source unit, front speakers, subwoofer and amplifier(s). Systems often get much more intricate and can include surround sound decoders, equalisers, navigation systems, rear and center channel speakers and a myriad of other items. Add these as you so desire.
  6. There are literally thousands of products used in audio / visual systems. These are only a few.
    $500 System
  • Source Unit: Clarion CZ201A / Crystal EDB410BT / Eclipse CD1200 / Sony CDXGT290
  • Front Speakers: Boston S95.3 / DLS426 / Eclipse SE6500 / Focal 690CA / Hertz ECX 690 / Orion CO650 / Polk DB650 / Rainbow Dream Line KS165
    $1000 System
  • Source Unit: Clarion CZ201A / Crystal EDB410BT / Eclipse CD5030
  • Front Speakers: Boston S60 / Crescendo Opus 1 / DLS B6A / Eclipse SE6500 / Focal 165V1 / Hertz ESK165 / Orion CO625 / Polk DB6501 / Rainbow Sound Line SAC 265 25
  • Amplifier: ARC KS300.2 / Audison SR2 / DLS CA22 / Eclipse XA4200 / Focal SOLID2 / Genesis Profile 4 / Orion CO300.2 / Zapco Reference 350.2
  • Cable: Audison Connection / Stinger
  • Deadening: Dynamat / FhrxPaint / Stinger
    $2000 System
  • Source Unit: Clarion CZ301A / Eclipse CD5030 / JVC KD-R826BT
  • Front Speaker: Boston SR60 / Crescendo Opus 3 / DLS MS6A / Eclise SC6500 / Focal 165V2 / Hertz HSK165 / Morel Ovation 6 / Orion C2.62 / Polk DB6501 / Rainbow Sound Line SAC 265 25
  • Amplifier: ARC XDi803 / Audison SR4 / Boston GTA504 / DLS CA31 / Eclipse XA4200 / Focal SOLID4 / Genesis Profile 4 / Orion CO600.4 / Zapco Reference 360.4
  • Subwoofer: Boston G212 / Crescendo Etude1.10 / DLS RW12 / Eclipse SW6012 / Focal 30A1 / Hertx ES300 / Image Dynamics ID12 / Orion CO1248
  • Cable: Audison Connection / Stinger
  • Deadening: Dynamat / FhrxPaint / Stinger
    $3000 System
  • Source Unit: Clarion CZ501A / Becker Grand Prix / JVC KD-R926BT
  • Front Speaker: Audison Voce / Boston Pro60SE / Crescendo Opus 5 / DLS Nortica / Focal 165KP / Hertz HSK165 / Morel Ovation 6 / Orion C2.62 / Polk MMC6500 / Rainbow CS 265 Profi
  • Amplifier: ARC Audio KS300.4 / Audison SR4 / Boston GTA504 / Eclipse XA4200 / Focal FPS4.160 / Genesis Profile Ultra 4 / Zapco Reference 360.4
  • Subwoofer: Audison Voce / Boston G212 / Crescendo Etude1.10 / DLS UR12 / Eclipse SW8200 / Focal 33V1 / Hertx HX300 / Image Dynamics IDQ12 / Orion HP12
  • Cable: Audison Connection / Stinger / Furutech
  • Battery: Odyssey PC1200MJT / Optima D35 / Stinger SPV44
  • Deadening: Dynamat / FhrxPaint / Stinger
    $5000 System
  • Source Unit: Clarion CZ501A / Becker Grand Prix / JVC KD-R926BT
  • Processor: Audison BitOne
  • Front Speaker: Audison Voce / Boston Pro60SE / Crescendo Opus 8.6 / DLS Gothia 6.2 / DynAudio System 242 / Focal 165KRX2 / Hertz Mille MLK165 / Infinity Kappa Perect 6.1 / Morel Elate 6 / Orion HCCA 6.2 / Polk MMC6500 / Rainbow Vanadium CS 265 Phase Plug / Seas Performance 6
  • Front Amplifier: ARC Audio KS300.2 / Audison LRx2.9 / DLS RA20 / Focal FPS2.150 / Genesis Profile Ultra 2 / Orion HP-2400 / Polk C300.2 / Tru-Tech B-2110 / Zapco Reference 350.2
  • Subwoofer: Audison Voce / Boston G312 / Crescendo Etude2.10 / Focal 33V2 / Hertx HXS300 / Image Dynamics IDQ12 / Orion HP12 / Polk SR124 / Seas SW300.1
  • Subwoofer Amplifier: ARC Audio KS1000.1 / Audison LRx1.1k / DLS RA10 / Focal FPS1.500 / Genesis Profile Ultra 1 / Orion HCCA-D1200 / Polk C500.1 / Tru-Tech B-2110 / Zapco Reference 1100.1
  • Cable: Audison Connection / Furutech / Wireworld
  • Battery: Odyssey PC1200MJT / Optima D35 / Stinger SPV44
  • Deadening: Dynamat / FhrxPaint / Stinger
    $10000 System
  • Source Unit: Clarion NX501A / Becker Grand Prix / Pioneer AVIC F20BT
  • Processor: Audison BitOne
  • Front Speakers: Boston SPZ60 / Crescendo Opus 9.6 / Diamond Audio Hex Pro 6 / DynAudio System 242GT / DLS Scandinavia 6 / Focal Beryllium Kit 6 / Hertz Mille MK2 / Morel Supremo 6 / Rainbow Power CS 275 27 / Seas Reference 6
  • Front Amplifier: ARC Audio SE2150 / Audison Thesis Duo / DLS A2 / Genesis Dual Mono / Orion HP-2800 / Tru-Tech B-2110 / Zapco C2K-2.0X.P
  • Subwoofer: Boston G555 / Crescendo Etude2.10 / Crossfire XT212 / Diamond Hex Pro 12 / Focal 33KX / Image Dynamics IDMAX12 / Orion HCCA12.2 / Seas SW300.1
  • Subwoofer Amplifier: ARC Audio SE2150 / Audison Thesis Uno / DLS A3 / Genesis Dual Mono Extreme / Orion HCCA-D2400 / Tru-Tech B-2110 / Zapco C2K-4.0X.P
  • Cable: Audison Connection / Furutech / Wireworld
  • Battery: Odyssey PC1200MJT / Optima D35 / Stinger SPV44
  • Deadening: Dynamat / FhrxPaint / Stinger
    $20000 System
  • Source Unit: Clarion NX501A / Becker Grand Prix / Pioneer AVIC F20BT
  • Processor: Audison BitOne
  • Front Speakers: Boston SPZ60 / Crescendo Opus 9.9 / DynAudio Esotar2.3 / DLS Scandinaiva 6 / Focal Beryllium Kit 7 / Hertz Mille MK3 / Morel Supremo 9.3 / Rainbow Power CS 275 27 / Seas Reference 8/4/1
  • Front Amplifier: ARC Audio SE2300 / Audison Thesis Duo / DLS A4 / Genesis Dual Mono / Orion HP-2800 / Tru-Tech B-2200 / Zapco C2K-2.0X.P
  • Subwoofer: Boston G555 / Crescendo Etude2.10 / Diamond Hex Pro 12 / DynAudio Esotar2 E1200 / Focal 33WX2 / Image Dynamics IDMAX12 / Orion HCCA12.2 / Seas SW300.1
  • Subwoofer Amplifier: ARC Audio SE2300 / Audison Thesis Uno / DLS A3 / Genesis Dual Mono Extreme / Orion HCCA-D5000 / Tru-Tech B-2200 / Zapco C2K-4.0X.P
  • Cable: Audison Connection / Stinger
  • Battery: Odyssey PC1200MJT / Optima D35 / Stinger SPV44
  • Deadening: Dynamat / FhrxPaint / Stinger
We continually update these lists so keep an eye on them.

Should I use a capacitor on my higher frequency speakers?

Remember midranges and tweeters are not designed to play subsonic (in the case of midrange) and midrange (in the case of tweeters) frequencies. Therefore, many midranges and tweeters benefit from a capacitor wired in to prevent lower range signals travelling to them. On the larger midranges you can go without them but more often than not the midrange speaker naturally rolls off.

How can I destroy my speakers?

When asked how one can destroy speakers we reply by explaining there is only three real ways. The first is thermally and this is the most commonly occurring. Breaking the equation down further there are only two ways to thermally destroy a speaker (and crossover in the case of split systems); over powering and under powering. Over powering the speaker with way too much power will cause the voice coil wire (which is receiving more current through it then its rated too) to melt and short on the magnet. This is simple enough to understand so if you have a 200 watt subwoofer then you don't feed it 2000 watts. However much more dangerous is under powering the speaker because the end result will be the same but it happens in a slightly slower and sneakier way.

In audio systems where you hear speakers 'distorting', it's not the speaker that is causing the struggle, it's the amplifier. Speakers are quite simple devices and don't discriminate. They cannot tell the difference between harmonic sound and rough distorted noise and simply reproduce whatever wave signal is given to them regardless of what it may sound like. When you ask the amplifier to do its job (by turning the volume up) it takes a comparatively small sound wave and amplifies it before sending this bigger signal to the speakers. If you ask your amplifier to produce more than it's capable of it will attempt to achieve this request but the output sound wave becomes rough and distorted as the amplifier reaches its power output threshold. Pushing it beyond this point causes the amplifier to begin clipping. When a woofer is driven hard by a high power amplifier there is a significant amount of current flowing through the voice coil. The voice coil has resistance and therefore a voltage drop across it occurs. This means that there may be a great amount of power being dissipated in the form of heat within the voice coil. When a speaker is driven with clean power the cone moves back and forth a great deal. You'll notice many speakers have perimeter vents in the basket and pole vents in the back. The speakers movement forces air to flow in through these perimeter vents and into the magnetic gap (the area where the voice coil lives and moves) before flowing out the pole vent (and hopefully taking the heat with it). When the cone moves forward out of the basket, the area that's under the dust cap and around the voice coil increases in volume. This pulls cool air into the magnetic gap. When the woofer moves the other direction, the chamber size is reduced and the hot air is forced out of the pole vent. This air flow cools the voice coil.

Click on images to enlarge

When a relatively low powered amplifier is driven into clipping (to the point of full square wave sometimes) the voltage delivered to the voice coil no longer resembles a sine wave because the amplifier clips the top and bottom of the wave off (because it's beyond what it can do). While this output is clipped (the flat spot on the top of the wave) the voice coil in your speaker is not moving but instead remains almost stationary at this time with high current still running through it. Because the voice coil is not moving it is not being cooled sufficiently (remember the coil is driven by a linear motor therefore the more voltage applied to the voice coil, the further it moves). In the image above you see that at points A, B, D, E, F and H the voltage is changing causing the voice coil to move in the gap and therefore pull in fresh cool air. At points C and G, the voice coil is still moving a little but this is only due to momentum. This is not enough to cool efficiently and there is still full current flowing through the voice coil. Since the displacement of the voice coil (and the relating airflow around it) is no longer proportional to the heat being generated, the voice coil will overheat. This excess heat (just as with overpowering) causes the voice coil to melt its insulation and the former to physically distort. Basically the whole motor burns apart as adhesives start to fail. However before you stress too much it should be noted that many reputable manufacturers underrate speakers so generally slight clipping isn't a problem. Severe clipping is more likely to cause a problem.

The second way to destroy a speaker is physically and this can also be broken down into two facets. The first physical facet is what we call bell mouthing. This is where the voice coil and former are driven so hard they actually extend beyond their normal range of motion and impact the back plate on the bottom of the speaker. This continual impacting causes the bottom of the voice coil to bend out like the bottom of a bell and this eventually cause the coil and corner to become so physically disfigured that it rubs on the magnet surrounding it and eventually comes to a complete halt. This isn't just restricted to subwoofers either. Tweeters playing frequencies that are too low tend to suffer from this phenomenon too because they're not designed for high excursion. The second facet of physically destroying a speaker is to punch way too much power into it fast and this causes what us engineering types like to call critical structure failure. That is a technical way of saying you'll simply tear the surround and/or spider(s) and pop the cone and motor assembly right off the frame. To 'blow the guts out of the speaker' is the more Aussie way of saying it. This is commonly witnessed during sound pressure level competition because the drivers are being pushed to their absolute limits.

The third and final way to destroy a speaker is an age old enemy of technology; sunlight. Nothing breaks down and erodes foam surrounds faster than sunlight (well except bugs like moths but you shouldn't have them living in your car). After only a few months of direct sunlight your speaker surrounds will be significantly weakened and may eventually begin cracking or simply tear all together. Butyl rubber surrounds are more resistant to sunlight but eventually all materials succumb to the mighty sun. The best thing to do with shelf speakers is place some grille cloth over the factory grilles. This helps in resisting ultra-violet rays from the sun penetrating through to the speaker.

These are the three main causes of most damaged speakers. The end result is the same with all three methods but you tend to get a lot more warning with thermal or sunlight damage. Physically speaking though; if you're pushing your speaker way beyond what its rating dictates you'll get very little warning before your speakers starts to smoke or literally explodes.

What is severe clipping?

Now that you know about clipping (see above) we move to severe clipping (a.k.a square wave). It always amazes me when I hear some idiot driving down the road and the audio is clearly distorted (you know what I mean). Many people drive their amplifiers into what could be called a square wave output (white line below). When an amplifier is pushed that hard, it is actually possible to drive the speaker with twice as much power as the amplifier can cleanly produce into the speaker. As you can see below, the yellow sine wave is the maximum 'clean' output that the amp can produce. When an amplifier is pushed way too hard, the signal will eventually look like the white line. The effective voltage of the white line is ~1.414 x the yellow line. This means the total power driven into the speaker by the clipped (square wave) signal is double the power delivered by the 'clean' signal (yellow line). This means that the power is double but the cooling of the voice coil will not increase in proportion with the power increase (since the voice coil isn't moving as much as it needs to be for the given power dissipation). This will lead to the voice coil overheating. If we compared the output of a 100 watt amp (the one that's clipping) to a 200 watt amp, the 200 watt amplifier would be able to push the speaker as much as 40% farther than the 100 watt amp (depending on the frequency of the signal). This extra travel (in each direction from its point of rest) would result in added airflow around the voice coil.

Click on images to enlarge

Note: The RMS voltage of a pure sine wave is equal to the peak voltage multiplied by 0.707. The RMS voltage of a pure square wave it equal to the peak voltage. For 2 waveforms with equal amplitude (as shown above), the RMS voltage of the square wave is 1.414 times the voltage of the sine wave. If we use the example of the 100 watt amp which can produce a sine wave of 20 volts RMS, we can see that the output power at hard clipping is double the power it can produce cleanly.

What is distortion?

Well, to get a little more complicated, distortion is any departure from a true and accurate reproduction of the original waveform. It can include Noise, Clipping Distortion, Harmonic, and Intermodulation Distortion. These last two forms are fairly common in loudspeaker reproduction and can be reduced but not entirely eliminated in the existing technology. It would be fair to say that modern amplifier design fairly eliminates nearly all forms of inherent perceived distortion, leaving only that caused by inappropriate user settings and overloading.

Distortion is the name given to anything that alters a pure input signal in any way other than changing its size. The most common forms of distortion are unwanted components or artifacts added to the original signal, including random and hum-related noise. Distortion measures a system's linearity - or nonlinearity. Anything unwanted added to the input signal changes its shape (skews, flattens, spikes, alters symmetry or asymmetry). A spectral analysis of the output shows these unwanted components. If a circuit is perfect, it does not add distortion of any kind. The spectrum of the output shows only the original signal - nothing else - no added components, no added noise - nothing but the original signal.

It's rather amusing to see amplifier manufacturers making great claims about the advantage of the extra .001 % Distortion they've wrung out of their products, while most speakers are considered very good if they can keep such distortions below 5 %. It's true that the reduction of any distortion anywhere is a positive contribution to the goal of high fidelity, but the disparity between the two technologies in this regard points up the largely subjective nature of many such claimed advantages.

Here are some of the definitions:

How much power can my new speakers handle?

If you've read the FAQ above you'll already know that you're better off with too much power than not enough. That's no to say however that speakers cannot be damaged by too much power; they can!

All speakers have a rated power handling level and this comes in handy as a rough guide to know how much power to feed your speakers. A speaker's general power rating tells you how much A.C. power can be dissipated in the speaker's voice coil without damaging the speaker. The realistic way to rate a speaker is to give the rating as continuous RMS watts. Many speakers are advertised as "150watt" or "100watt" speakers and you may be forgiven for thinking that the 150watt speakers are better and will play louder than the speakers rated at 100watts. The first thing you should realise is that speaker ratings are often exaggerated for marketing reasons. Check to see if the rating is in RMS or peak watts and are the speaker ratings for maximum or continuous power. Most car audio speakers (with the exception of some subwoofers) are rated in peak power or music power. Only a few speakers (generally the higher quality speakers) are rated in RMS watts. While peak power is a legitimate way to rate speakers (as long as the manufacturer tells you that the power rating is in peak watts), it can be deceptive.

When talking peak vs RMS, you know that peak power is 2*RMS power. If a speaker is actually capable of handling 150 watts of peak power it would only be rated to handle 75 watts RMS. If a speaker is rated to handle 150 watts 'music power' it may mean that the speaker will take only very short bursts of power approaching 150 watts RMS. Even if there are two speakers from different manufacturers which have the same power ratings, one of the manufacturers may be more conservative in their ratings than the other manufacturer. The more conservatively rated speaker would be more likely to handle its rated power. The bottom line is beware of power ratings on speakers. Knowing that some manufacturers are somewhat optimistic with their power ratings will help you to make better decisions when buying speakers.

A quick word on amplifiers and speakers. Many people ask us "Can my speakers handle this amplifier or will this amplifier blow my speakers?" The simple answer is that any speaker can be driven by any amplifier. The only time that issues arise is when the person operating the system becomes careless. Sadly most people drive their amplifiers well into clipping. See above for explanations on clipping.

Do I need the biggest amp possible?

The answer to this question depends on factors such as how loud you like to listen, what speakers you're using and what your budget is. Remember we always say that the bigger the amplifier the better because the larger the amplifier, the less work it must perform to successfully drive the speakers. Larger amps keep their THD low, their efficiency and control level high and they stay cooler. It's better to have a larger amplifier doing minimal work than to wring the neck out of your smaller one. Remember though that too much power can also damage speakers so the gains MUST be set correctly.

How loud will my speakers play?

Look up the sensitivity rating of the speaker, which is expressed in dB/watt/meter. For example a speaker with a 89dB sensitivity will produce 89dB of sound 1 meter (39") from the speaker with a 1 watt input. For every doubling of power input the SPL (volume) increases by 3dB. So in this case, assuming a 100 watt power handling spec:

Power input (watts)

So, theoretically, the SPL limit of this speaker would be somewhere between 107dB and 110dB.

What brand of amplifier would you recommend?

There are literally thousands of amplifiers to choose from out there. This is where an installers experience comes in handy. Serious installers will listen to your demands and then recommend an amplifier that best suits your desires.

Beware of "bargain" amps though as cheap amplifiers are exactly that and you'll often have problems not too long down the track. Too much power for too little money generally means that corners have been cut somewhere in quality of construction or service back-up. Aim for about $2-$3 per watt for quality.

What is the optimum enclosure for my new subwoofer?

Most subwoofers come with recommended enclosure volumes in the owner's manuals. More often than not this enclosure volume is safe allowing for the most 'home user error'. Specialized shops however use complete manual's and specialised computer programs to carefully design enclosures for specific applications based on the subwoofers paramters. The following is a very basic crash course on box types (this topic gets very in depth).

Basically as far as sealed is concerned, the relationship between the characterisitics of the speaker being used and the volume of air inside the enclosure dictates the how well the sub will sound. When the enclosure is bigger, the air spring limits cone motion less and allows the system to play lower and with flatter overall response (lower Qtc) at the expense of power handling. Problem is if you go too large you start to compromise efficiency in order to gain the additional low frequency extension. On the other hand, making the enclosure smaller will cause the air spring to exert more control and limits cone motion at low frequencies which increases power handling but does not let the system play as low and produces a more peaked response (higher Qtc). For most half decent speakers there is a range of enclosure volumes that will produce high quality sound. Changing the enclosure volume within that range can fine-tune the sound to best suit the tastes of the listener. Of course other factors effect this but this is close enough.

Depending on the sound you desire, you tune a port to a certain frequency to achieve better bass response around that frequency. The tuning of the port there must be done using careful calculations which take into consideration the enclosure volume, the resonance of the port and the Thiele / Small parameters of the sub into consideration. Using these we attempt to delay the rear output wave of the speaker just enough so that when it comes out of the port it is close to being in phase with the wave being produced by the front of the sub. So with that in mind, you can see how, by altering the port length and diamter, we tuned the port to a certain frequency. The reason ported enclosures are generally considered louder is that when we utilise the work of the rear of the cone we gain double the bass, or 3dB over a broad range of frequencies. Again there are other things to consider and explain like the sub unloading below the port tuning but that is another thing...

With bandpass enclosures the woofer no longer plays directly into the listening area. Instead the entire output of the subwoofer system is produced through the port or series of ports. In a conventional sealed or ported enclosure the low-frequency extension is controlled by the interaction of the speaker and the enclosure design but the high frequency response is a result of the speaker's natural frequency response capability unless limited by a crossover. In a bandpass enclosure the front of the speaker fires into a chamber which is tuned by a port. This ported front chamber acts as a low-pass filter which acoustically limits the high frequency response of the subwoofer system. The name "bandpass" is really pretty descriptive in that it refers to the fact that the enclosure will only allow a certain frequency "band" to "pass" into the listening environment.

Obviouly the same thing be accomplished by placing a low pass crossover on the subwoofer system but a bandpass enclosure can produce significant performance benefits in terms of efficiency and/or deep bass extension that would not be possible in conventional designs of equal size. By adjusting the volumes of the front and rear chambers and the tuning of the port or ports, significant performance trade-offs can be created. When box parameters are adjusted for a narrower bandwidth the efficiency of the subwoofer system within that bandwidth increases and can reach gains of up to 8dB and sometimes even higher. As box parameters are adjusted for wider bandwidths, very impressive low-frequency extension can be produced from extremely compact enclosures at the expense of efficiency and good transient response. Intermediate bandwidths can also be designed which create a compromise between all these characteristics. As if that is not confusing enough, within each bandwidth range the designer can also manipulate box parameters to shift the range of operation up or down the sub-bass range which also has an effect on efficiency. As you can see, bandpass enclosures can have very different sound characteristics based on the designer's choice of box parameters. As such, it is not always possible to make blanket statements as to the performance benefits and drawbacks of bandpass enclosures in general.

One characteristic of bandpass enclosures which is universal is that they exert greater control over cone motion over a wider frequency band than conventional designs. Due to controlled, rapidly changing air pressure on either side of the woofer, the woofer is capable of producing high levels of acoustic output without physically moving very much. This means that the woofer is less likely to encounter excursion limits in the main part of the sub-bass range. However, just because the cone isn't moving as much doesn't mean that the speaker's motor assembly isn't still trying to drive the cone hard; it just means that the speaker cone is encountering resistance to motion. This resistance can be very hard on speakers, especially when SPL heads are playing their music. The conflict between the force generated by the motor assembly and the air pressure in the enclosure can impose extreme stress on the glue joints and suspensions of the woofers. You can literally tear a speaker apart in a bandpass enclosure if you apply too much power. Because the speaker is not moving as much and because noises are masked by the front chamber, it is also very difficult to hear when a woofer is in serious trouble. Many people have been known to crank bandpass enclosures up and blow the speaker to bits within a few minutes because they did not realize that the speaker was dying a horrible death. Choosing the right amount of power and carefully setting amplifier gains is very important in order to ensure long term reliability.

Bandpass enclosures can be divided into two basic types; single and dual reflex. In a single reflex design, the rear chamber is sealed and the front chamber is ported. In a dual reflex design, both front and rear chambers are ported into the listening area. A variation of the dual reflex and single reflex, known as "series-tuned," has a port which connects the rear and front chambers. The differences between single reflex and dual reflex bandpasses are similar to the differences between sealed and ported enclosures. A single reflex typically exhibits a shallower low-frequency roll off rate (e.g. 12dB/octave) and better transient response. A dual reflex is more efficient and controls cone motion over a wider range but typically has a sharper (e.g 18-24dB/octave) low frequency roll off. Because of the difference in low-frequency roll off rates, a dual reflex usually has to be larger in size to produce the same low frequency extension as a single reflex design.

Compared to more conventional enclosure designs, bandpass enclosures are very complex to design and build. The rules governing the performance of bandpass enclosures leave no room for error. Slight volume miscalculations or sloppy construction can turn a good design into a poor performing box. Integrating the proper size port or ports can be extremely challenging and often renders designs that looked great on paper completely impractical. The design of these boxes should definitely be left to people with extensive enclosure building experience.

Should I use sound deadening, diffusers or fibrefill inside my enclosure?

The debate on whether to use sound deadening material, diffuser panels and fibrefill inside an enclosure has been around for a long time. However, this debate needs to be broken down into two areas because you're actually addressing two separate issues when asking about these materials. The first issue is regarding standing waves and the second is regarding the delaying of sound waves and the smoothing of resonance. Well start with standing wave issue first.

Standing waves
Standing waves cause violent response fluctuations inside the enclosure but for a standing wave to exist the distance between parallel boundaries (the enclosure walls) must be half the wavelength of the frequency at which the standing wave exists. Considering that sub-bass waves vary from 17.19 meters (@ 20 Hz) to 3.44 meters (@ 100 Hz) the generation of a standing wave is going to be impossible in an enclosure designed to fit in your average sedan or hatchback. People often install sound deadening and diffuser panels unnecessarily inside their enclosures to combat these standing wave issues (this is also the reason why some people are reluctant to employ certain square enclosure shapes). As you can see above though; in reality, due to the small dimensions of most car audio subwoofer enclosures, there is little chance of generating standing waves in the enclosure.

Sound delaying and resonance smoothing
Sound delay and resonance smoothing is another matter altogether and this is where the fibrefill comes in. Fibrefill is often employed in enclosures that are a little too small (usually due to space restrictions within the vehicle). Damping material is primarily used to fool a subwoofers suspension into 'seeing' a larger enclosure than it actually lives in. The other primary use for fibrefill is to smooth over little resonances, peaks and dips inside the enclosure itself. Just as a side note; if you're planning on using fibrefill inside a ported enclosure, make sure it is not getting to close to the internal port mouth.

What is the ideal box size for my midrange speakers?

Assuming your 3" / 4" / 5.25" / 6" / 6.5" speakers are midrange drivers and not subwoofers (Focal make a 5.25" subwoofer for example), you shouldn't need to make a sealed enclosure for it. In most cases (but not all) there is no need to build sealed enclosures for these midrange drivers because their suspension (the spider and surround) is designed to operate in an infinate baffle situation such as a door or rear deck of a car. In other words, most midranges are free-air drivers. However, it's always best to consult the manual for your new speakers if you're not sure.

What crossover frequency should I use between my subwoofer and my 6" or 5" midbass drivers?

There's no quick and easy answer to this question, It all depends on the car and the overall design of the system. Generally speaking you don't want your subwoofers to go much higher than 80-100Hz. Typically when you set your subwoofer crossover point you will use that as a starting point for your high-pass on your mid/bass drivers. Sometimes you will need to increase the crossover frequency and sometimes you will need to lower it. It is basically all a matter of personal preference and the acoustics of your car. Electronic crossovers make it very easy to try a variety of crossover frequencies to see what works best for you and your car.

Should I use an active crossover or a passive crossover?

Active crossovers are ones that effect the signal before it is sent to the speaker (usually located within the head unit or separate processor). Passive crossovers are after the amplifiers output and sit near the speaker, filter out certain signals coming towards the speaker. Using either you'll achieve the same aural result but it's a lot faster to adjust an active one. Lower cost and ease of installation is usually what makes the passive crossover more attractive.

Where should I place my tweeters for best performance?

Okay, stop and think about a concert for a second. You don't sit with your back towards the band right? Rather, you want the sound in front of you. Likewise you want to be in the first row, be dead center of the band on stage and depending on your personal preference you might like to be slightly below the sound (as is an audience member) or slightly above the sound (as a conductor is). This is the image we try and capture inside cars today and tweeter positioning plays a large role in achieving this phenomenon. You cannot just simply slap tweeters in anywhere. To get a decent stage you need good width, height and depth - preferably mirror-tip to mirror-tip, floor to roof and as far down the bonnet as possible.

Where to mount them then? Kick panels, sails or elsewhere?
We often see tweeters mounted up high on the sail area on the door or down in the kick panels. Both these work well but can suffer from similar issues. The problem with the sail mounts is this; think about the position of your ears in relation to the tweeters. One speaker is belting the high pitch tunes out about one foot from your ear where as the other tweeter is triple, quadruple or quintuple that distance away. The image has no choice but to be right out the side window. Sheer laws of physics govern this fact.

If you place the tweeters down in the kick panels then the right speaker distance is about three feet and the left speaker is about four feet away. The problem is not utterly eradicated but it becomes a lot less noticeable as the distance separation is reduced (by up to half sometimes). However using the kick panel method can result in the stage being a tad low (the kicks are often used on cars with no factory tweeter location to avoid the cost of custom A-pillars or sails too). Remember tweeters cannot be placed anywhere where they fire straight into ones feet so you have to be more careful about their placement on both sides and more often than not this results in them being mounted very high up in the kick panel, quite often well out of sight and well up under the dash - this is also good for security too.

The final mounting place of your tweeters depends what you desire from your system and what your budget is. As mentioned above; when choosing a tweeter mount in order to achieve a great sound stage you're always faced with various issues. Put the tweeters up high and forward and you'll get good depth and height but the stage width can sometimes suffer. If you put them deep in the kick panels you tend to get good width and depth but the height can sometimes suffer. Seems you cannot win sometimes, especially when you factor other things on like reflection issues. Generally speaking though, mounting the tweeters in the a-pillars right at the front corner of the dash will result in the best unmanipulated (i.e. no time alignment) sound stage. If that is not an option, then experimentation is the best strategy. Remember too that tweeter location can also play a role in ambience too. If the tweeters are positioned correctly (whether in the kick panels, A-pillars or even behind the review mirrors) they will help the whole component set fill the car with high frequency sound - not just way off in front of you.

There are two other issues to consider when choosing where your tweeters will go too. Cost is one because to mount the tweeters successfully in the A-pillars there is a good chance you're going to require some custom work done and hence the price goes up. Then there is also the security issue too because people can now see your tweeters. Factor all these issues in when you are deciding.

What about time alignment?
Time alignment is an essential tool but it can also be a curse if not used correctly. One of the more common problems associated with time alignment is regarding the seperate sides of the car in relation to stage width. If you're not careful, the better you make one side sound (and you can get it absolutely perfect) the more the other will suffer. This is because you're delaying one speaker side so both signal paths reach your ears at the same time. The problem with this is that the other side has the reverse problem to your side so as yours gets better, it can get worse. However when used correctly (and we recommend you do use time alignment) it can move the stage depth forwards (you delay the fronts in relation to the subwoofer too) in addition to getting your image perfectly located in the center. With a careful blend of experimentation and measuring you will eventually get both sides sounding great.

So how does one get the stage right in real world terms?
At the end of the day you'll just have to experiment quite a bit (and sometimes it can take days) to get the tweeter placement just right to achieve the perfect stage 'width', 'height' and 'depth'. Get yourself a nice big blob of blue-tac. Stick the tweeter onto a panel somewhere, turn the time alignment off for the moment and commence playing songs performed by a powerful vocalist (ranging from baritone up to contralto as these are the frequencies at which human hearing is most sensitive and therefore is best for staging). Close your eyes and imagine you're at the concert. Now listen to where the singer is coming from. Are they singing from right in front of you? Are they slightly off to the left a tad or right? Are they a little high or a little low? Simple move the tweeter a few inches in a direction and have another listen. How is the image? Can you hear where all the band members are exactly? How is the depth? Does the drummer sound like he is behind the other musicians (stage depth)? Do the individual musicians sound like they are specifically somewhere on the stage? (stage width). Keep doing this until you get the image dead center but remember to take a rest every fifteen minutes for half an hour to let your ears normalize. Remember your ear drums are controlled by muscles and they (just like any other muscle) get tired, so make sure you give them a rest. If you attempt staging for hours on end your ears tend to 'hallucinate' and give false readings. Once you have it very close then you can activate your time alignment and do the fine tuning.

Advanced staging and imaging techniques
If you're really serious about getting your stage and image the best it can possibly be then you should also consider the manufacture of new panels altogether. That way you can physically change the location of the tweeter (in the case of a two way component set) or midrange and tweeter (in the case of a three way component set). Below are some of the options for different tweeter and midrange mounting locations.

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I've heard people recommend against 6x9's. What are the pros and cons?

It seems there are few debates in the known world larger than the one concerning the humble 6x9" speaker. Now depending on which side you're on (as there seems to be no middle ground these days), 6x9's are either a little nuisance that you'd rather have sitting far in the rear of the car or better still, on the road behind the car, or you cannot even contemplate a life without them.

Lets begin with some basics. 6x9's are oval shaped speakers aptly named because they measure 6 inches by 9 inches. There are slightly different versions measuring 7x10, 4x6 and 6x8 on the market but let us concentrate on the daddy of the group. 6x9's are more often than not three or four way drivers (that is; three or four speakers in one unit) and comprise of a 6x9 woofer, smaller mid-bass (or two) woofer and a tweeter mounted on a bridge over the main woofer. They are commonplace in many different factory audio systems right over the world.

But I have heard so many conflicting opinions…
Now you might have heard hi-fi buffs recommending against using 6x9's in high end audio systems whilst recommending them for every other type of system. There are actually numerous pro's and con's of 6x9's and there are reasons why they're avoided for high budget systems and targeted for low budget systems and factory upgrades.

Lets look at the cons first.
The first issue is the actual cone size. The large woofer cone is a different width to length so it is obviously uneven. When viewed under a microscope the woofer cone can physically distort quite dramatically and hence, disastrously so far as sound quality is concerned. They tend to distort more than round or square speakers where kinetic forces are evenly exerted across the cone surface. Another big problem faced by 6x9's is one similarly faced by co-axials. The woofer is seated directly underneath the midrange and tweeter. While this doesn't bother the average tweeter because they're sealed in most cases, it can cause great stress and problems for the midrange which is trying to play a higher frequency than the pounding a woofer underneath. More often than not midrange clarity tends to suffer and can sound blurred as the woofer underneath wins every time. Simply put, 6x9s are not dedicated drivers. They do not offer the same freedom for fine tuning nor do they faithfully reproduce sound like separate components do. They do their job competently but will never match a separate subwoofer for bass reproduction, or separate woofer for mid-bass reproduction or tweeter for high end reproduction because these drivers are dedicated to reproducing their own little part of the sound spectrum and they do it well. Components can also be mounted separately to help with staging and imaging.

But they must have some pro's.
They do. As stated above the cone on a 6x9 is exactly that, which incidentally is nearly the same surface area as an 8" subwoofer. With their relatively high power handling, the 6x9 can punch out quite a bit of bass and they can even be run in enclosures to enhance this ability. Another big bonus of the 6x9 is their power handling ability and efficiency. They can be run off the smallest internal (head unit) amplifier to the largest external units. Because of this ability they make terrific upgrades to factory systems where a little more bass is required. On that note, they will also fit into many factory locations without the need to cut anything up.

Expense. Time. Space. Money. Say it how you will, 6x9's are a hell of a lot cheaper than lashing out on a large external amplifier, sub enclosure, subwoofer and splits. And they will take up a lot less room too incidentally. At the end of the day 6x9's make an excellent addition to budget systems and make terrific factory upgrades because they do a little of everything quite acceptably. They are very good drivers for beginners and people looking for a little more of everything but lets be realistic, they won't keep the staunch audio buffs satisfied for long.

When I turn my music up, my headlights dim. How come?

Your headlights dim because your audio system has caused a drop in the available voltage level of power for your car's other, less necessary accessories (headlights, engine, etc.). Voltage drops can be caused by an accessory's large current demand, like an amp struggling to produce a loud bass note. Get your battery and alternator checked. A low battery can overload an alternator, drawing power away from your system. If everything checks out okay, you could be making such large demands on your electrical system that an upgraded alternator may be necessary. A "stiffening" capacitor can also be installed. A stiffening capacitor is like an extra power supply for your electrical system; it keeps a small reserve of 12V power. See your installer. If your car won't start after you play the stereo for a long time w ith the engine off, try paralleling another battery into your system. Another reason this happens is because the battery negative to body has not been upgraded. Remember whatever positive cables you add to your battery, the equal negative must also be upgraded.

My system "pops "when I turn it off. How do I stop it?

As you power-down, transient signals in the processor sometimes find their way into the signal path. The amp transmits them to the speakers, and POP! Add some "turn off delay" to your head unit. See your manual, or your installer. Or, read this: You can add delay by adding a 1N4004 diode in series with the processor's turn-on lead, with the striped side towards the equalizer. Then add a capacitor in parallel, the (+) side of the cap to the striped (processor) side of the diode; the (-) side of the cap to ground (not the radio or eq chassis, connect it directly to the car chassis). Fiddle with the cap value to get the amount of delay you need before the eq shuts off; not too long, just long enough to make sure the amp is off before the eq powers down (220 - 1000 uF). Make sure the cap is a polarized electrolytic, 16V or higher, and remember that the diode introduces a 0.7V drop on the remote wire, which can cause the processor to power down before the rest of the system. There will be a quiz.

What speaker pods and door trims can I get for different budgets?

We often get asked what speaker pods and door trims are available for different budgets. Below are some of the more common speaker pods and door trims we make here at Fhrx Studios. Remember many of these pods are colour matched then dyed or painted as opposed to using off-the-shelf trim. Many are also vacuum formed rather than hand formed. This often incurs extra costs.

Speaker pods

Full lower door bottom pod.
  • Bolt-on custom pod. This is the most complex bolt-on pod. Fully custom made to match the door contours. It is usual trimmed in vinyl and colour dyed or painted. Approximate price is $350-550 each.

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  • Moulded full door bottom pod. These are made to replace the entire bottom of the door and are fully moulded from fibreglass or kelvar. They are then dyed or painted to match the door trim. Trim is usually done with a vacuum forming machine. Approximate price is $550-850 each.

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    Full door trim.
  • Moulded full door. These replace the entire door trim and are custom moulded from either fibreglass or Kevlar, colour matched in vinyl dye and vacuum formed. Approximate price is $800-1500 each.

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  • All out custom full door. These are the most complex door trims we make. They are fully custom and can include moulded fibreglass, kevlar, perspex, metals, porcelain and even accuation. These pods are usually trimed using a vacuum former and often painted. Approximate price is $1500-3000 each.

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Other sizes are available of course and full custom ones are also available too. Prices for these custom items are available upon request.

How do I tell if my speakers are in or out of phase?

If your speakers are out of phase, imaging will be vague and bass output will be reduced. To ensure that your speakers are hooked up in phase, check to make sure that the positive and negative leads are connected the same way to both your speakers and your receiver or amp. Make sure red is connected to red, black to black, etc. Check for correct phasing... With a 9-volt battery. Disconnect the speaker wire from the amp. Touch the wire you think is negative to the negative battery terminal (the big one). Touch the positive wire to the positive battery terminal (the other one). If your speakers are wired in phase, the speaker cone will move "out" and stay there. If they are out of phase, the driver cone will move "in" and stay there. (This won't help you for tweeters, only midranges and woofers. So when you're wiring your tweeters, be careful. Do it right the first time.) Phasing is never absolute in car audio situations, since speakers are rarely facing the same directions. Phasing differences mostly affect bass. Is your system lacking bass? Try changing the phase on your sub system. 90% of the time, that's the key to more bass!

How do I use my faders and balance settings to make my system sound better?

Proper setting of your front-to-rear fader and left/right balance controls is important for optimum staging and imaging in your system. Too much sound in the rear of the car (sometimes called "rear fill") will often eliminate staging altogether, forcing sound away from the front of the car, while too little rear fill will sound dull. Too much sound on one side of the car or the other will add an unrealistic element to the imaging. To adjust fade and balance, play a tape or CD you are familiar with and turn the rear speakers on full with the fade control. Listen to the rear speakers, and then slowly turn the fade up in the front speakers just until you can't tell the rear speakers are playing anymore, then ease off a tad. You're probably close to optimum setting when the front staging is such that the rear speakers provide little more than ambiance and space to the sound. Test it by going full on the front speakers (without losing the position you just attained). You'll hear an immediate loss of spaciousness in the sound with the rear speakers faded all the way down. Return to your optimum setting. Setting the balance is more difficult, so it's always a good idea to leave the balance fader at the "12 o'clock" position. That's as close to equal as you're going to be able to hear with your own ears.

Can my car stereo really hurt my ears?

It most certainly can. Prolonged exposure to sound pressure levels above 85dB will cause permanent hearing damage. Professional audio competitions specify the use of hearing protection devices for their contests, especially at higher volume levels. You can test the dB level of your car stereo with a Sound Pressure Level Meter (available at electronics stores). If you're disoriented and your hearing is sort of muffled after you've been listening to your car stereo, or you hear ringing in your ears, then turn it down! If you have to shout at the person in the passenger seat, and you're not angry with them, then it's a good bet that your stereo is too loud. For the sake of your hearing, turn it down.

Is there a place I can talk to someone about this stuff?

Sure is. The gang and Marty, along with literally thousands of other car audio nuts can be found on various forums around the country, by far the largest of them being Mobile Electronics Australia.

What are the different amplifier classes all about?

All sound is a sinosoidial waveform in that it has alternating peaks and valleys. The center point of each wave is the zero, or switching point that separates the positive (top) from the negative (bottom) portion of each wave.

When a tube or transistor amplifier operates in Class A, the output tubes or transistors amplify the entire waveform without splitting it into positive and negative halves. Class A amps usually provide lower, often imperceptable distortion, but at the expense of reduced power output.

In Class AB, used in the overwhelming majority of amplifier designs, the signal is split into two halves, positive and negative, and each half is sent to a tube or transistor circuit for amplification. Both sides work in tandem, and the two halves are recombined at the output section to reconstruct the whole signal. This technique increases the amount of power that can be applied, but increases distortion.

Class D or High Current operation is essentially rapid switching, hence the term switching power amplifier. Here the output devices are rapidly switched on and off at least twice for each cycle. Theoretically, since the output devices are either completely on or completely off they do not dissipate any power. If a device is on there is a large amount of current flowing through it, but all the voltage is across the load, so the power dissipated by the device is zero; and when the device is off, the voltage is large, but the current is zero. Consequently, class D operation (often, but not always digital) is theoretically 100% efficient, but this requires zero on-impedance switches with infinitely fast switching times -- a product yet to be made; meanwhile designs do exist with efficiencies approaching 90%. Class D design is increasingly popular for driving subwoofers, where maximum power is necessary, and slightly elevated levels of distortion are easily tolerated.

What amplifier specs should I look out for?

Choosing an amplifier is about more than just watts. When speaking to anyone about achieving quality music in car audio most people simply focus on the speakers rather than the amplifier. They often speak about speaker build quality and power handling, enclosures, porting, fibrefill, loading and speaker cable. You don't really need to worry about the amplifier so long as it's powerful enough right? Just like when you're considering the purchase of a new car; the only thing you need to look at is the power output of the car alone right? Wrong.

When choosing an amplifier to power your speakers there are more stats than just power output you need to think about before you splash a couple of grand on an amp that will sound like rubbish. For those among you dreading an upcoming lecture on amplifier classes, resistors, capacitors, transistors, transformers and power supplies relax, I'll keep this to plain English for the explanation of which stats to look out for. High power output is important but quality amplifiers are not just about sheer power. Mining dump trucks have over 6000 horsepower but that doesn't make them spectacular performers. Besides power there are certain other important figures that must be taken into consideration when choosing a suitable amplifier. We'll go through a few of the more commonly found stats.

Damping Factor
Damping factor describes an amplifiers ability to control a woofer cone. It's the ratio of rated load impedance to the internal impedance of an amplifier. The higher the damping factor the more efficiently an amplifier can control unwanted movement of the speaker coil. High damping factor is crucial for subwoofers and the higher the damping factor the better. It is debatable if anything over 50 is audible. Damping factor is calculated by dividing the speaker impedance by the output impedance of the amplifier. In other words the damping factor will decrease as the speakers impedance decreases. This means an amp optimised at 4 ohms will provide tighter bass than when they're running at 2 ohms. A lower damping factor will leave bass notes sounding soft and undefined, regardless of the amplifiers power output. You can see by this that a smaller 100 watt amplifier with a high damping factor can often sound better than one twice it's size with a low damping factor.

Slew Rate
Sometimes referred to as damping factor for tweeters, the slew rate describes the amplifiers ability to accurately control fast direction changes of a speaker cone or dome. Have you even turned your stereo up to discover that your cymbals sound like someone throwing a brick through a glass window? That's because the amplifier simply wasn't fast enough to accurately reproduce the high frequency ring of the symbols. Measured in volts per microsecond, a low slew rate softens the definition of a sound signal which blurs transients and causes the sound to appear muddy. A high slew rate means the amp responses faster which ultimately results in crystal clear highs.

Total harmonic distortion
THD is the measurement of the how much the amplifier can distort the sound signal through the introduction of added harmonics or overtones. THD figures are usually given as percentages and a THD figure below 1% are generally inaudible to most people. However, distortion is a cumulative phenomenon so if your head unit, eq, crossover and amplifier are all rated at less than 1%THD each, together they could produce 5%THD which may well be noticeable to most of you.

Signal to noise ratio
Noise leaking into the sound signal is an ever present problem in car audio. The Signal to noise ratio is a measurement of noise level in the amplifier compared to the level of the signal. A higher S/N ratio signifies a greater difference which is better. Technically speaking, it's the ratio expressed in dB of signal power at a reference point in a circuit to the noise information that would exist if the signal were removed (the noise floor). The maximum signal to noise ratio of the amp can be seen as a measure of realistic fidelity. This ratio is how much absolute noise it produces compared to the highest signal voltage it can pass without distortion. Many companies combat noise by utilising balanced line systems.

Stereo separation.
Separation is not spoken about much but this refers to the amplifiers ability to maintain the separation between the right and left channels. This is essentially what allows an amplifier to reproduce an accurate sound stage. Each individual instrument is after all, are recorded in it's own location in the sound stage and you should be able to hear this in the same way when it's played in your car.

Just a final few points to remember while you're looking at specs. You'll find many are followed by the term 'A weighted'. Put very simply, 'weighting' is part of a compensation system that accounts for various factors (for example, one such factor is the human ears' natural hearing curve). However; sadly some companies are guilty of using this weighting to make its amplifiers figures appear more attractive. Loading is another issue to consider. Watch the impedance of speakers when choosing them because while most amps are stable at low impedance levels, they're not overly efficient nor performing 100% when loaded down. Your cars engine is 8000rpm stable but it's unwise to try and keep it there for long. By the same token many amps are 2 and 1 ohm stable but this is for intermittent spikes (as music is dynamic it causes the speakers resistance to continuously change during playback), not continous everyday running.

These are some of the more important figures to observe when buying amplifiers. It's not simply just a matter of buying which ever amp outputs the most power. It's a matter of taking all the figures into consideration and choosing which amplifier best suits your needs.

Can you simply explain Ohms and resistance?

Well lets see? Put simply, Ohms is the measurement of electrical resistance and system impedance. It is a measure of the degree to which electrons are limited in both velocity and quantity in passing through a circuit. In Impedance measurements, this takes into account, the mechanical resistance inherent in the motion of transducers. The standard is usually 4 ohms for car audio and 8 ohms for home and commercial audio. Some specialty woofers may be rated at 2, 6, 12 or even 16 ohms. You would have seen the 12 ohm JL's before no doubt.

Ohm's Law is the he mathematical relationship between voltage, current, and resistance. It is named after George Ohm, it's discoverer. Ohm's law states that current volume in a conductor is directly proportional to the voltage flow across it and inversely proportional to its resistance (assuming the temp remains constant). In general, this means that more voltage will produce more current, if resistance stays the same, but higher resistance will cause current to decrease if voltage stays the same. In mathmatical terms, V = I x R, where V is voltage, I is current, and R is resistance. Ohm's law is a description of electron behavior upon which virtually all understanding of electronics is based.

Just for further background information, you might have heard all this called resistance of impedance so I'll give you a little more info on those two things as well.

Regarding resistance, almost all conductors of electrons exhibit a property called resistance. Resistance impedes the flow of current. It is measured in units called Ohms. With a water hose, resistance could be regarded as friction between the water and the hose. A larger hose would create less friction and have a lower resistance than a smaller hose. It could also be a finger over the hose end. In electrical circuits, small round cylinders with wires on either end are called resistors. These typically reduce the flow of electrons to serve the specific requirements of the circuit elements, such as amplification or switching functions.

Finally, Impedance. The totality measured in Ohms of all electrical opposition to current flow: resistance, reactance, capacitance, as well as all mechanical factors inhibiting the completion of energy transfer in a contained system. In practical terms, this means that most Drivers are assigned a certain nominal impedance based on their DC voice coil resistance and mechanical stiffness. For car audio this is usually 4 ohms; for home stereo, 8 ohms is the standard. Put simply, your voice coil has a certain amount of copper winds in the voice coil(s). If you want a high resistance, triple the amount of winds and the current suddenly has to do X amount more work to travel past the coil.

Which way should I aim my subwoofer?

The aiming of subwoofers has been quite a topic of speculation for years now in car audio. Through experimenting many people have found that their subwoofers sound much better when aimed backwards. Many people realise that there seems to be much more bass with the boot open than with the boot closed. We've heard a great deal of strange and utterly incorrect theories to explain this phenomenon.

The main reason this phenomenon occurs is all about sound waves (direct and reflected) and more importantly the cancellation of these waves. The diagrams below assist in showing the sine waves and their phase relationships between the direct sound wave entering the car and the reflected wave that hits the back of the boot and reflects forward. Since the reflection is bounced into the listening area one can treat them much the same as having two sources.

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In the above picture the vertical black line at the left of the picture is the boot rear panel (the beaver panel the tail lights are mounted on). This picture is an illustration of what happens when sound comes out of the front side of the subwoofer enclosure. Sound travels forward into the car (the purple wave) and also backwards to reflect off of the back of the boot (the red wave). Both the direct wave and reflected wave get to the listener but they are slightly out of phase causing a variable amount of cancellation in the listening area. At this stage if you opened the boot the reflected wave would disappear and not reflect back into the car, thus resulting in no cancellation.

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In the picture above picture the speaker box has been aimed at the boot instead of the rear seat and you can clearly see the direct and reflected waves are not nearly as much out of phase as in the first example. This resulting in much better bass reproduction.

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This picture above represents the subwoofer enclosure being moved to the rear of the trunk with the subwoofer aiming forward. The waves are a little closer to being in phase with each other.

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In this picture (above) we're aiming the rear mounted subwoofer enclosure at the rear so the direct and reflected wave are very close to being in perfect phase from the start and hence they reinforcing each other quite well.

Note; these pictures are simulated using a 60Hz note with the rear of the box mounted approximately 3 feet from the back of the boot. Keep in mind we're only discussing the direct and rear reflected sound in an effort to try to simplify this. The reflecting sound waves in a car are much more complex than these drawings indicate but we must start simple before getting too carried away. For example, remember that placing the subwoofer cone face too close to any panel can load it (resulting in a similar effect to that achieved by a bandpass enclosure) but we'll worry about that another day. This explanation should be a nice foundation for those of you who wish to study this phenomenon further. One other thing we should mention is that before people comment that this cannot be true because the interior of cars being small in relation to bass wavelengths, the full wavelength does not have to completely develop to be in or out of phase with its own reflected sound. The pictures above are showing a 60Hz wavelength and the bounce distance to reflect back out of phase a complete 180 degrees is just over 4 foot. At higher frequencies the distance is less (120Hz is 2.3ft for example). Remember, the key is to experiment and see what works best for you and your vehicle.

What is the highest sound pressure level (SPL) we can achieve?

Ever wondered just how loud or soft sound pressure can get? Or have you got no idea what all those dB readings you keep hearing about actually compare too? Well click here to find out.

How do I set my gains?

Contrary to popular belief, the amplifier gain control is not simply a volume knob that determines the maximum volume that an amplifier can produce. As long as the head units signal (which runs down the RCA cords) has sufficient power the amplifier is able to produce its maximum power output level. It's a matter of getting the full volume range of the head unit to match the full output range of the amplifier(s). The gain controls do exactly that. They are also used to match other amplifiers in the system (in the case of a multi-amp system). Not all head units have the same maximum preamp output voltage. Some head units are capable of producing 9 volts on their preouts while others are only capable of 1.5 volts.

Please note that most head units will reach their maximum output level (and begin clipping - see above) just before the volume control reaches the upper end of its range (usually at a point of 85-90% of its maximum range).

Assuming your amplifier is the right power for the speakers (around the same as their rating), the proceedure of setting the gains is not overly difficult. First you set everything onto zero. All amplifier gains should be turned right down and all head unit boosters (like the loudness button) should be off. Then turn your deck up full volume and then back it off to about 85-90% (eg if your Alpine deck goes to 35, bring it up and then back off to 33-34). Moving to the amplifier, slowly bring the gain up until the distorting becomes audible. Once it's audible, turn it back ever so slightly and that is your gain set for that amp.

Now remember if your amplifier output is much higher than your speakers rating (e.g. running 50 watt speakers with a 500 watt amplifier) the amp will destroy the speakers long before it begins to distort at all. For this reason we strongly recommend that unless you're a pro, you purchase the correct size power amplifier for your speakers. If you do have a larger amplifier for superior control then you will need to get a pro to set the gains. It can be difficult to set the gains when there is more power available than the speakers can handle.

In plain English, what you're doing is insuring the entire volume range of the head unit (e.g. 0-35 on Alpine head units) matches the entire volume range of the amplifier. In multiple gain / mulitple amplifier situations, we usually recommend setting the midrange amplifier first as it is easiest to hear distortion through midranges (human ears are most sensitive to 1000-2000hz).

What do all the Theile / Small parameters stand for?

This listing and explanation is from the " the12volt.com" website.

  • B: Magnetic flux density in gap, in Tesla-meters (TM)
  • BL: The magnetic strength of the motor structure.
  • C: Propagation velocity of sound at STP, approx. 342 m/s
  • Cas: Acoustical equivalent of Cms
  • Cmes: The electrical capacitive equivalent of Mms, in farads
  • Cms: The driver's mechanical compliance (reciprocal of stiffness), in m/N
  • D: Effective diameter of driver, in meters
  • F3: -3 dB cutoff frequency, in Hz
  • Fb: Enclosure resonance (usually for bass reflex systems), in Hz
  • Fc: System resonance (usually for sealed box systems), in Hz
  • Fs: Driver free air resonance, in Hz. This is the point at which driver impedance is maximum.
  • L: length of wire immersed in magnetic field, in meters
  • Lces: The electrical inductive equivalent of Cms, in henries
  • L: Length of wire immersed in magnetic field, in meters
  • Ms: The total moving mass of the loudspeaker cone.
  • Mmd: Diaphram mass, in grams
  • Mms: The driver's effective mechanical mass (including air load), in kg
  • n0: The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as %
  • p: (rho) Density of air at STP 1.18 kg/m^3
  • Pa: Acoustical power
  • Pe: Electrical power
  • Q: The ratio of reactance to resistance in a series circuit, or the ratio of resistance to reactance in a parallel circuit.
  • Qa: The system's Q at Fb, due to absorption losses; dimensionless
  • Qec: The system's Q at resonance (Fc), due to electrical losses; dimensionless
  • Qes: The driver's Q at resonance (Fs), due to electrical losses; dimensionless
  • Ql: The system's Q at Fb, due to leakage losses; dimensionless
  • Qmc: The system's Q at resonance (Fc), due to mechanical losses; dimensionless
  • Qms: The driver's Q at resonance (Fs), due to mechanical losses; dimensionless
  • Qp: The system's Q at Fb, due to port losses (turbulence, viscousity, etc.); dimensionless
  • Qtc: The system's Q at resonance (Fc), due to all losses; dimensionless
  • Qts: The driver's Q at resonance (Fs), due to all losses; dimensionless
  • Q parameters: Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same.

    As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance."

  • R: Ripple, in dB
  • Ras: Acoustical equivalent of Rms
  • Res: The electrical resistive equivalent of Rms, in ohms
  • Revc: DC voice coil resistance, in ohms
  • Rg: Amplifier source resistance (includes leads, crossover, etc.), in ohms
  • Rms: The driver's mechanical losses, in kg/s
  • Sd: Effective piston radiating area of driver, in square meters
  • SPLo: Sound Pressure Level, usually measured at 1 watt, at 1 meter in front of the loudspeaker
  • Vas: "Equivalent volume of compliance", this is a volume of air whose compliance is the same as a driver's acoustical compliance Cms (q.v.), in cubic meters
  • Vd: Maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters.
  • Xmax: Maximum peak linear excursion of driver, in meters

Do I really need sound deadening?

Ever visited a cinema with no carpet on the walls? Ever wondered why most home theatre walls have curtains? Maybe you've seen a car or jet test cell without diffusers on the walls? What about a radio studio or sound recording booth without diffusers? No? Starting to notice a pattern? Sound deadening and diffusers are fundamental cornerstones (and arguably one of the most important aspects) of any sound system. They're so important in fact, that they should be budgeted for long before the speakers themselves are. However before we delve into the wonderful world of what sound deadening and diffusers actually do, let's first take a step back and look at what sound actually is.

Simply put; sound is differing frequencies of pressure waves. Expanding that concept a little; when sound is created in a medium (i.e. it cannot travel through a vacuum) it's in the form of a mechanical wave. This wave is the result of back and forth vibration of the particles that make up this medium. As sound waves move through air the particles are displaced both right and left as the energy of the sound wave passes through it. The motion of these particles is parallel to the direction of the energy origin and this phenomenon is why we characterize sound waves in air as longitudinal waves. A speaker cone is designed to create such a longitudinal wave. As the cone moves back and forth it pushes on neighbouring air particles. The forward motion of the cone pushes air molecules horizontally to the left while the backward retraction of the cone creates a low pressure area allowing the air particles to move back to the right. This movement creates regions in the air where the air particles are compressed together and other regions where the air particles are spread apart. The high pressure regions are known as compressions and the low pressure regions are known as rarefactions (note; not refractions - that's to do with light waves).

Wavelength (also known as path length or soundwave length) are common terms when talking speakers and physical sound. Wavelength is the distance the aforementioned disturbance travels along the medium in one complete wave cycle. However at this stage there is a small differentiating factor that should be explained and that's the difference between transverse and longitudinal waves. For traverse waves this pattern occurs once every wave cycle and is commonly measured from one wave peak to the next adjacent wave peak (or from one wave valley to the next adjacent wave valley). Since longitudinal waves do not contain peaks and troughs, their wavelengths must be measured differently. A longitudinal wave consists of a repeating pattern of compressions and rarefactions. Therefore the wavelength is commonly measured as the distance from one compression to the next adjacent compression or the distance from one rarefaction to the next adjacent rarefaction.

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When speakers move backwards and forwards they do so many times a second. Each time the cone does one complete movement forward then backwards then back to the zero point it's known as a cycle or one hertz (a.k.a. 1Hz). If the speaker undertakes one thousand of these cycles per second it is known to be playing 1000 hertz or 1 kilohertz (a.k.a. 1000Hz or 1kHz respectively). Music is the repeating pattern of these high and low pressure regions in various frequency orders and certain patterns of frequencies our ears interpret as harmonious. This harmony is simply the music you're listening too. The Pinna (the outer ear skin section) catches these waves and directs them into our ear canal which houses our ear drum. The ear drum then mimics these varying pressure waves and lets your brain know what its hearing.

Now you understand the basics of how sound physically works so let us move to the sound deadening itself. As speakers move in alternating directions the sound emanates from both the front and rear of the cone. The front wave is heard by you while the rear wave is what the sound deadening and diffusers deals with. With all due respect; your cars doors are glorified metal cans. They echo and reverberate inside and the skins flex easily, causing bass to become blurred and muddy and even to cancel itself out all together. I usually explain it by using the following analogy. Imagine you're seated in a boat in the middle of a crystal clear flat lake. One hundred meters away there is another boat floating idle. If you start gently rocking you boat, waves emanate from it. Pretty soon these waves reach the second boat and it also begins bobbing to mimic these waves. The problem is that as this second boat rocks it not only reflects your waves back but also creates its own. Your doors are the same in that the metal skins flex and create all matter of sound effects. These waves are only minutes or seconds out of phase (i.e. not even whole degrees) to the active wave and the result is that your ears get bombarded by literally hundreds of sound waves that are not supposed to be there. This creates an echoic effect and the end result is that the music sounds hollow and tinny. By adding sound deadening you're adding mass to the doors skins (like swapping the second boat for a cement pier in our analogy). This combats flexing its effects on internal sound waves.

Diffusers are absorbent pads that resemble foam or tiny egg cartons. These fight wave reflections and are placed directly behind the speaker. Remembering back to our boat analogy with the cement pier (deadening) now in place; while extra waves are not being created any more, the main waves will still be reflected. This is where the diffusers come in. We know from above that sound waves have a certain lengths at any given frequency. Somewhere within these frequencies is the perfect distance for sound emanating from the rear of the speaker cone to travel to the doors outer skin. This will then reflect and come flying back to impact the cone and cancel the next cycle. The diffusers catch these sound waves and trap them much the same way that the paint on stealth aircraft catches radar waves or submarines rubber skin traps sonar waves. The reason you need diffusers on top of the deadening is that most sound deadening has a smooth skin and hence still reflects sound waves.

Another vitally important aspect of achieving good midbass is to seal the speaker into the door. In nature all elements take the easiest path from origin to destination. Water is a good example of this phenomenon; you pour it out and it will run wherever the easiest path is. Air is the same. When your speaker cone moves forward, it creates a high pressure cell right in front of the speaker cone. If there is a high pressure cell in front of the cone then there will be a low pressure cell on the rear side of the speaker cone. If the door is fully sound deadened and the speaker is sealed on using sealant of foam gasket, the high pressure air will move out towards you with the end result being incredibly punchy and tight midbass from your doors. If there is no sealing (say the speaker is simply screwed down to the metal) and contains air leaks everywhere, the high pressure air simply takes the easiest path and moves around the edge of the speaker frame to behind the speaker where the low pressure cell is. In simple terms, you get no bass.

Many cars come with deadening from the factory but it is usually an insufficient amount, often only being a few inches here and there to minimise rattles during transit. Car manufacturers limit this deadening in order to keep production costs down. How much deadening you end up installing depends on your budget but both the inner and outer skin of your front doors should be fully deadened at least. You can always add more to the boot, floor and roof down the track.

In conclusion; for the serious sound enthusiast sound deadening is an absolute must. If you have a close look you'll notice the cars that sound the best in every continent (especially the ones that win the sound offs) are chock full of deadening. Sound deadening even helps factory speakers so get your self some today.

Note; wavelength image taken from A Review of the Universe - Structures, Evolutions, Observations, and Theories.

Should I upgrade the speakers in the rear of my car?

Think about a concert, opera or other similar performance; you don't sit with your back to the band or performance do you? It's the same for your car audio system; seeing as you're seated at the front of the car and your ears face forwards we recommend you leave the rear speakers factory and not bother to upgrade them. Instead, concentrate on the front speakers. The only time we bother upgrading the rear speakers is if you either:

The reason is this; the Pinna (also called the auricle) is the visible part of the outer ear. It collects pressure waves (differing frequencies of pressure that we interpret as music / sounds) that the membrane captures from in front of it and directs this sound into the outer ear canal. It's important to remember too that each pinna individually is responsible for determining height while the two ears together determine width. Sound coming from behind the pinna, unless the frequency or volume fluctuations are significant, will not be collected accurately.

Hence the upgrading of the rear speakers will not present you with much benefit. This is why we have front 'stage' and rear 'fill'. One thing to note though on the subject of rear fill is that this all comes down to personal preference. Some people actually like the sound emanating from behind them so if this describes you then by all means upgrade the rear speakers.

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From what you have read above you can now see why many demo and competition cars have their rear speakers turned down or simply don't have them at all. What we instead recommend is that you spend all your money on the front speakers where you are and get yourself some sound deadening (q.v.).

Are the expensive cables really worth it?

Now cables are one subject bound to start an argument at any audio gathering. Everybody has a different opinion on cables. To us, cables are not just cables. The reason we recommend high quality cables is two fold. One reason is that the better quality the cable, the more strands it usually has and hence more current carrying ability. Now this is not overly important at all as you can simply buy a larger (lesser quality) cable if need be so we don't try and sell high quality cables based on that argument alone. But consider this; when you think about it, you're paying just as much because you can get a better quality cable of a smaller gauge that ends up being the same price as the larger one of lesser quality.

The other main reason is that better cable tends to have a much more uniformly extruded jacket. If you get a meter of cheap cable and compare it to a meter of more expensive cable and chop it at 25mm intervals, you'll often find the cheap cables come dangerously close to breaking out of the jacket every so often due to poor extrusion dies. Again not important if you plan on having your system for three months but if those cables have to withstand literally years of abuse under carpet (water / dirt / feet impacting them) then this does become an issue.

Moving onto the oxygen free argument, this is not overly important when referring to car audio cables as it will not make an huge audible difference. However one interesting report that tends to generate quite polarised opinions is a text known as "The Genesis report". This report really delves into the realm of high end cables. The best thing to do is to read it here and make your own decision.

Do my subwoofers need separate chambers within their enclosure?

When running more than one subwoofer in an enclosure, you'll need to decide between using a common chamber (where all subwoofers run in the same airspace) or a separate chamber enclosure (where each subwoofer has its own airspace). Common chamber enclosures have no dividers between the subwoofers and the airspace inside the box is the internal volume for one subwoofer multiplied by the number of subwoofers in the enclosure. Separate chamber enclosures are built in a way that sees every subwoofer isolated inside the enclsoure in its own chamber.

Generally speaking, it's usually better to have each subwoofer running in its own isolated enclosure, especially in a sealed box. We say this because if one of the subwoofers ceases working for any reason in a common chamber enclosure, it could cause the other subwoofer(s) to unload and you could end up ruining the subwoofers that are still working. For example, if your subwoofer can only handle a 0.88cf sealed enclosure and is running flat stick when it's brother dies, then all of a sudden that remaining subwoofer is in a 1.6cf sealed enclosure.

Ported and bandpass enclosures are the only type of enclosures that we tend to recommend running with a common chamber. This is because it allows you to have a single port (either slot, round or otherwise) acting as the port for all subwoofers in the box. This will generally require less space than having separate ports in separate chambers for each subwoofers. The possibility of a good subwoofer unloading when another fails is less likely in a ported box as well.

In conclusion; if you're running with a sealed box then we suggest it should have separate chambers for each subwoofer. If you're running a ported subwoofer enclosure then it is quite okay to have either separate or common chambered enclosure. However, if you have the space it is always best to design a multi-chambered enclsoure so each subwoofer is isolated in its own airspace.

What grille can I get to protect my subwoofer?

We get asked so often about what grilles are available to protect subwoofers that we actually decided to add it to the frequently asked questions page! Below are some of the more common 12" grilles we employ here at Fhrx Studios. Other sizes vary depending on grille type but you can get most in 8", 10" and 15".

  • Aerpro steel mesh grille. RRP$18.90

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  • Aerpro chrome grille. RRP$29.95

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  • Audioline SWG12D. RRP$23.00

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  • Crossfire A-Spec alloy grille. RRP$49.00

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  • Fishman Audio grille RRP$99.00

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  • Jaycar steel mesh grille. RRP$11.50

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  • Kitchen handles. Kitchen drawer handles come in a massive variety of shapes and sizes and can be used as a single, double, triple or whatever takes your fancy. Prices vary depending on shape and size.

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  • Polk Audio grille. RRP$45.00

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Other sizes are available of course and full custom ones are also available too. Prices for these custom items are available upon request.

What are the frequencies of sound?

Ever wondered what instruments play which frequncies? Or wondered what the difference is between an alto singer and a soprano? Well look no further, below are two frequency charts that will help clear things up a little.

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These types of charts are what we more commonly use to demostrate where each frequency lies. These will also aid you in tuning your system, especially if you're using a multi-band equalizer.

Can you explain batteries, capacitors and cycles?

Just like the petrol tank at the back of your car holds the fuel for your engine, your battery holds the fuel for the electrical components within your car. A standard battery is okay for standard electrical demands but once you start adding electrical components (such as amplifiers) you'll need to bring the power storage system up to speed too by either adding a capacitor or upgrading your battery. Lets look a little further into what a battery actually is.

Batteries differ to stiffening capacitors in that they create electricity via a chemical reaction whereas caps simply store energy. Your standard run-of-the-mill lead-acid cell (i.e. factory car battery) is created using a large number of thin plates that are mounted tightly side by side (or in spiral / circular cells as is the case with Optima batteries). The material these plates are made from alternates as they sit side by side (i.e. plates 1, 3, 5, 7 and 9 are one material while plates 2, 4, 6, 8 and 10 are the other). The most commonly used of these materials are Lead Dioxide (PbO2 / the positive plates) and Sponge lead (Pb / the negative plates). These plates are immersed in electrolyte which is most commonly diluted Sulphuric Acid (H2SO4). The types of metals and the electrolyte used will determine the output of a cell. A typical fully charged lead-acid battery produces approximately 2.11 volts per cell so when you couple six of these cells together you get your twelve volt car battery. The chemical action between the metals and the electrolyte (battery acid) creates the electrical energy. Energy flows from the battery as soon as there is an electrical load (e.g. a starter motor, an amplifier, a pair of headlights, a heater and so on) that completes a circuit between the positive terminal (connected to the positive plates) and the negative terminal which is connected to the negative plates. Electrical current flows as charged portions of acid (ions) between the battery plates and as electrons through the external circuit from negative to positive. Just re-read that last sentence again too; the power flows from the negative to the positive - this is why we put so much emphasis on earthing kits and other earth upgrades when installing systems. The action of the lead-acid battery is determined by many factors, some of which include the chemicals used, state-of-charge, temperature, porosity, diffusion, and of course; load. As a side note I should also mention that while many batteries (such as Optima and Odyssey) are called dry cells, they're actually gel-cells. The electrolyte is actually a jelly like substance rather than a true dry substance.

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Moving to the actual life and home of batteries, what most people don't realize is that car batteries operate in a constant process of charge and discharge. When a battery is connected to a load that needs electricity (such as the starter motor) current flows from the battery and it begins to discharge. In the reverse process a battery becomes charged when current flows back into it. This process restores the chemical difference between the plates. This happens constantly while you're driving because the alternator puts current back into the battery. Expanding this concept and getting a little more technical; as a battery discharges the lead plates become more chemically alike. The acid becomes weaker and the voltage drops. Eventually the battery is so discharged that it can no longer deliver electricity at a useful voltage. You can recharge a discharged battery by feeding electrical current back into it. A full charge restores the chemical difference between the plates and leaves the battery ready to deliver its full power again. This unique process of discharge and charge in the lead-acid battery means that energy can be discharged and restored over and over again. This is what's known as the cycling ability in a battery. More about battery cycles later.

When the battery won't start your car people usual refer to it as "dead". However that is not technically correct. A battery that's merely discharged (from leaving your headlights on for example) can be jump-started from another fully charged battery and recharged to its full capacity. About thirty minutes of driving around should allow the alternator to fully charge the battery. However if the alternator (or another part of the cars electrical system) is damaged the battery will not recharge. So if your battery keeps discharging, have someone check the electrical system before changing the battery. Recharging can only be undertaken a certain number of times for any given battery and when once it reaches the end of its service life (when the active material in the plates can no longer sustain a discharge current) it must be replaced. Car batteries age as the active positive plate material sheds (or flakes off) due to the normal expansion and contraction that occurs during the discharge and charge cycles. This causes a loss of plate capacity and muddy sediment to build up in the bottom of the case. This can eventually lead to short between the plates of a cell and is a shore fire way to kill off the battery. In hot climates there are additional causes of failure such as positive grid growth, positive grid metal corrosion, negative grid shrinkage, buckling of plates or loss of water. The list doesn't end there though. Deep discharges, heat, vibration, fast charging, and overcharging all accelerate the "aging" process. Scarily though; approximately fifty percent of premature car battery failures are caused by water loss during normal recharging and charging (in other words; a lack of maintenance). The water simply evaporates under high temperature (either internally or under bonnet) and many people simply don't bother to top it up. And for heavens sake purchase a battery that is of the right size for the job at hand. Many intercooler kits (such as the one for the 200SX) come with Odyssey 650 battery to allow the intercooler tube to go through the battery tray. These batteries are designed for jet skis and are literally murdered when you start placing big demands on them.

Battery cycle is another important aspect to consider and if you're an audio nut you no doubt will have heard of deep-cycle batteries. A cycle is defined as one discharge and one recharge of the battery. Most normal and deep-cycle batteries are lead-acid cells and use exactly the same chemistry for their operation. The difference is in the way that the batteries optimize their design. Normal shallow cycle car batteries are designed to provide a very large amount of current for a short period of time. This surge of current is needed to turn the engine over during starting. Once the engine starts the alternator provides all the power that the car needs so a car battery may go through its entire life without ever being drained more than 20 percent of its total capacity. Used in this way a normal car battery can last a number of years. To achieve a large amount of current a normal car battery uses thin plates in order to increase its surface area.

Deep cycle batteries are designed differently. They're designed to provide a steady amount of current over a long period of time. They can still provide a surge when needed but not quite as powerful as a normal car battery can. A deep-cycle battery is also designed to be deeply discharged over and over again (such as when you're playing your stereo for long periods of time without the engine running). This is something that would ruin a car battery very quickly. To accomplish this feat, a deep-cycle battery uses thicker plates. The deep-cycle battery can withstand several thousand total discharge/recharge cycles, while a normal car battery is not designed to be totally discharged.

You would be ill-advised to purchase a battery without understanding some specs and two of the more important ones for a car battery are CCA and RC. Cold cranking amps (CCA) refers to the number of amperes the battery can produce at 0 degrees C for 30 seconds. Reserve Capacity (RC) is the number of minutes that the battery can deliver 25 amperes while keeping its voltage above 10.5 volts. Typically a deep-cycle battery will have two or three times the RC of a normal car battery but will deliver less CCA. For this reason you'll usually find deep-cycle batteries in sound quality cars and normal car batteries in sound pressure level cars. It's very important in SPL competition cars that massive amounts of current remains on tap for instant usage. The help this cause capacitors are also often employed right next to the amplifiers.

Capacitors (also known as stiffening or power capacitors) are similar to batteries but have one main difference in that they do not generate electricity. Rather; they only store it and discharge it - fast. They have a similar mechanical built to a battery, utilizing two rolled up plates of electrically conductive material separated by a dielectric insulator. Within this frame an electrical field charge is stored. The quantum (quantity) of this charge is the capacitor's value, measured in farads. It is determined via a few factors including the surface area of the plates, the effective distance between the plates and the chemical composition of the dielectric material. Audio capacitors (the ones the size of coke cans) are fast discharging energy reservoirs that store the necessary power your amplifier will need to punch those big bass notes while limiting clipping. They store power during intervals when it is not required (which is most of the time) and release it when a short term transient demand exceeds what is available from the car's power system.

If you wish to keep your factory car battery, generally you'll use a stiffening capacitor to keep your energy levels topped up. From the smallest 0.5 farad to monsters like the 35 farad one available from Stinger, you're guaranteed to find a capacitor suitable for your installation. When selecting what size cap you need there is a very general rule of thumb that states you require around 0.5 farad (500,000 microfarads) per 500 watts of continuous power output. Using more will not cause any problems other than damage to your bank account balance.

Like batteries, caps have many different specs but one important one (besides farads) is named the Equivalent Series Resistance. All caps are rated for ESR and in a perfect world they would only have one figure. However all conductors have resistance and in a cap there are many conductors such as terminal leads, foil and even the dielectric electrolyte and the resistance of these conductors all contribute to the capacitors series resistance. It's essentially the same as having a resistor in series with an ideal capacitor. Capacitors with relatively high ESR will have less ability to pass current from its plates to the load (the amplifier) so consider this aspect before purchasing.

In conclusion; aftermarket capacitors and batteries are NOT substitutes for a poor charging system. Even with an after market battery you may have to install a stronger alternator if your charging system is struggling. Remember too that while not all audio systems need a cap but they are nice if you can budget for one. In much the same way a car will stop with the factory brakes but if you can afford Brembo six pots you'll stop a lot faster!

Note; image above is taken from How Stuff Works.

Is there a website that lists all manufacturers?

The short answer is; yes there sure is. It is called Mobile audio and it can be found by clicking this link.

Should I Upgrade my Earths?

You most certainly should. But before we canvas this topic you might first want to read about how batteries work. Once you have a clearer understanding of batteries and DC current we can move onto to how to get it efficiently moving around the car.

With engineering technology in modern cars getting more and more advanced one aspect that tends to get overlooked by many manufacturers is an adequate grounding system dedicated specifically to assist the engine electrical and ignition systems. Upgrading existing earths in addition to adding numerous new key earth cables may not seem like much but when you do it the difference is certainly noticeable. Not only will you see small improvements in power and torque figures, your motor will run smoother, it will rev cleaner, your lights will be brighter and although hardly likely to impact you, earthing kits actually assist in fighting engine water corrosion caused through electrolysis. The big winner though is your sound system because like everything else in life; your amplifiers need fuel too.

So why add an earthing kit? As you know; DC current flows in a circuit from the negative battery terminal, through the car (and it's electrical devices) and back into the positive terminal of the battery. So already you can see where I'm heading in regards to this issue. When it comes to inadequate earthing systems, it's usually not the cable itself that is the problem. Rather; it's where those cables are anchored. Usually earths are attached to the side of the engine bay via a small screw located on sheet metal. So you're trying to flow all the current form the cars various electrical devices back to the battery and then you go and add a titanic amplifier. Here is where a bottleneck is then created - trying to flow enormous amounts of current across one or two bolt threads. For this reason we install earthing kits on cars. This kit runs from the battery negative terminal to various points over the car (shock towers, head, plenum chamber etc) and allows current to flow much more readily. They can be of any gauge and can have any number of cables depending on customer desires.

Click here for photos of our various earthing kits.

Finally; just a quick disclaimer to the nitpickers; these earthing kits will ONLY assist if your cars existing earthing system is inadequate for the current you're attempting to flow. If your car already has a titanic earthing system capable of handling hundreds of amperes of current flow then you'll get no value in adding additional earths.

What subwoofer enclsoure can I get for different budgets?

We often get asked what subwoofer enclosures are available for different budgets. Below are some of the more common enclosures we make here at Fhrx Studios. Remember these enclosures are constructed from MDF, multi-panel, fibreglass, Kevlar or even more exotic materials such as porcelin. The external surfaces are often carpeted, vinyl (that is colour matched and dyed) or even painted in two-pac. Vinyl and painting often incurs extra costs to those listed.

Basic enclosures
  • Level 1 square or wedge. These are built to suit the car and the subwoofer, are usually constructed from MDF or multi-panel and are usually trimmed in carpet, vinyl or painted. Approximate price is $100-400 each.

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  • Level 2 square or wedge. These are more intricate shapes (with angles and indents), are built to suit the car and the subwoofer, are usually MDF or multi-panel and are trimmed in carpet, vinyl or painted. Approximate price is $200-500 each.

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  • Level 3 square or wedge. These are enclosures that have a painted face on them for extra effect. They're built to suit the car and the subwoofer, are usually MDF or multi-panel and are trimmed in carpet, vinyl or painted. Approximate price is $300-800 each.

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  • Level 4 square or wedge. These are the most complex of the basic enlclosures (usually incorporating amp or cap racks), are built to suit the car and the subwoofer, are usually MDF or multi-panel and are trimmed in carpet, vinyl or painted. Approximate price is $400-1000 each.

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Moulded enclosures
  • Level 1 moulded. These are built to suit the car and the subwoofer, are usually constructed from half MDF or multi-panel (front face), half fibreglass / Kevlar (back end) and are usually trimmed in carpet, vinyl or painted. They usually have a simple grille on the front and simple contour matching around the edges. Approximate price is $400-700 each.

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  • Level 2 moulded. These are built to suit the car and the subwoofer, are usually constructed from full fibreglass / Kevlar (front face and back end) and are usually trimmed in carpet, vinyl or painted. They usually have a simple grille on the front and simple contour matching around the edges. Approximate price is $500-1200 each.

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  • Level 3 moulded. These are built to suit the car and the subwoofer, are usually constructed from full fibreglass / Kevlar (front face and back end) and are usually trimmed in carpet, vinyl or painted. They usually have a door built into the front face to hide the subwoofer. More complex contour matching around the edges. Approximate price is $600-1200 each.

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  • Level 4 moulded. These are built to suit the car and the subwoofer, are usually constructed from full fibreglass / Kevlar (front face and back end) and are usually trimmed in carpet, vinyl or painted. They usually have a fibreglass / kevlar surround to show off the subwoofer. Very complex contour matching around the edges. Approximate price is $800-3000 each.

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  • Level 5 moulded. These are built to suit the car and the subwoofer, are usually constructed from full fibreglass / Kevlar (front face and back end) and are usually fully painted and sometimes airbrushed. They usually have a fibreglass / kevlar surround to show off the subwoofer. Most complex contour matching around the edges. Approximate price is $1500-4000 each.

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Stealth enclosures
  • Stealth cover. You can also opt to have a stealth cover created for your enclosure.

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Other sizes are available of course and full custom ones are also available too. Prices for these custom items are available upon request.

How does 'Qtc' effect my bass?

When people are discussing sealed enclosures, you'll often hear the Qtc of the enclosure / subwoofer combination mentioned during the discussion. Qtc is the total resonance of the speaker system and basically is the relationship the enclosure will cause the subwoofer to have between smooth roll off and peaking at a particular frequency. An enclosure with a Qtc of 0.707 will give you the best of both worlds. In other words; the best peaking in conjunction with the lowest and smoothest possible roll off (also known or F3) point for your subwoofer.

If you look through the Thiele / Small specs which should come with your new subwoofer, you'll find Qts, Vas, and Fs. These are the main three electro-mechanical parameters that influence the Qtc. Using a calculator and various formulae, experienced shops can calculate your required enclosure volume.

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In the chart above, the relative efficiency of the example subwoofer is set at 90dB. So when we look at the F3 point we need to start with a realistic sound pressure level (for example 90dB - 3dB = 87 dB). These coloured lines show how the different Qtc's look when plotted.

Now getting back to the Qtc of 0.707. While in theory this is best compromise for many a subbass requirement, sound quality inclined buffs often look for what is called a critically damped enclosure. These have a Qtc lower than 0.707 and hence have the smoothest and lowest rolloff. However this can also work against you because the lower the Qtc goes the more issues you can run into such as control loss or over run. Customers wanting louder subwoofer enclosures at the expense of a lower roll off (without resorting to porting for achieveing this phenomenon) tend to construct enclosures that have a higher Qtc than 0.707. In real world terms though; if you're not too sure then it's wise to trial a few different sized enclosures in your ride before you settle on the final design.

Note; image above is taken from CarStereo.com.

Should you be buying locally?

This discussion originated as a thread on MEA but we've had so many people converse with us about it that we've now transferred it here for preservation. Before we start I’ll offer a apology and disclaimer up front. The apology is for the length while the disclaimer is that this discussion is not an angry tirade, is not a whining grovel nor is it intended as fear mongering or attempted sensationalising. It’s simply a point of view put up for consideration. I could be totally off the mark here so considered feedback on my comments below is always appreciated. Without further ado; onto the discussion point:

For years we’ve been publically avoiding a discussion regarding the elephant in the corner of the room although we seem more than happy to grumble about it in private - the issue of why you (the consumer) should be buying local rather than taking your business overseas, especially when asking stores for unrealistic install pricing. I’ll break this discussion into four separate parts. The first part will concentrate on what local stores require from you. The second part will concentrate on what stores are actually offering you, the third part concentrates on the possible negative consequences for yourself while the fourth part concentrates on the negative consequences for us (the industry) when you take your business overseas.

Part one - What your local stores require from you.
Whilst this should be palpable, it only takes mere minutes of discussion with some people to become painfully obvious that it’s not. That is the issue of how stores work – not just audio but all stores. By their very nature, retailers and wholesalers make a living by selling products for a slightly higher price than they buy it. Most people seem to understand this basic commercial phenomenon but we still get person after person asking for everything to be done for next to nothing. Bear in mind the money you pay us for work undertaken is actually how we pay our mortgages, rego, insurance, grocery, gas, water and electricity bills and what have you. This is not to say you should always pay top dollar; all shops will discount prices, do package deals, offer group buys and so on, but you shouldn’t be asking your installer to do your planned $1000 install for $75. After all; try going to work tomorrow and telling the boss you won’t be requiring payment. Sure he’ll love you but how long will you last?

Part two - What your local stores are offering you.
When you employ a store to install a system in your car you’re actually buying a service, not just a product. I know it’s easy to have the mindset to buy everything online but this action is actually makes life difficult for stores, especially when they’re offering a premium service. In the fair dinkum department; if you’re just buying a simple product (like a microwave) then by all means, visit three hundred websites and make twenty thousand phone calls. But when it comes to installation you’re moving beyond simple product shopping, despite initially starting your audio venture at this stage. There is an old saying in the industry; you can price match but you cannot service or experience match. With this in mind consider what services your store is offering. I cannot vouch for all stores but some of the services we offer include:

Now they're just the labour side of things. Then there is the material side of store service. These are the products and miscellaneous items we often provide without charge (often to members here):
  • We’ve given people replacement speakers free of charge in the past. The most recent example was when we gave Wayne a replacement Boston Z6 midrange when his amplifier died and damaged an existing one – that’s a $300 driver.
  • We gave Doug a free Audison sub controller.
  • We gave Zenafore a free dash kit because I had it sitting here taking up space.
  • There are countless numbers of people on here that we’ve given earth upgrades too, just to show them how their amplifier works better once it can get serious current.
  • We offer people free drinks when they’re here.
  • We’ve given many people many small things like fuses and terminals.
  • We’ve given people alarm items such as glass break and tilt sensors for free.
  • We’ve done free amplifier repairs for people whose product damage wasn’t their fault.
Finally there are the various aspects of the install itself. Despite stores charging you a certain amount for the labour, we quite often spend up to four times the actual man-hours to get your install just right (without charging you a dollar more). I won’t go into all the various install techniques themselves as people can
read all about them here. Alternatively, you can check out the various images contained in our section of this website.

So after reading through those lists you’ll hopefully appreciate that it can get a little despairing when people bring us boot full’s of equipment they’ve bought off online eBay stores and then ask us to put it in cheap or for free, all whilst expecting us to maintain a high standard.

Part three - What are the negative consequences for you if you’re not supporting the local industry?
When purchasing products off some online stores hosted within websites like eBay, you’re can run various risks. The most obvious is that the product you ordered in fact doesn’t turn up. However some of the less obvious ones are:

  • Some of the products sold are fakes. We constantly see people buying equipment online, only to seem upset to find their brand new $1000 speakers they only paid $100 for aren’t the real McCoy.
  • You might get evaluation, test or malfunctioning stock. If you have a look around various websites such as ARC Audio and Zapco you’ll see numerous warnings against buying online for these exact reasons. I cannot tell you how many times people have brought stuff online only to find it malfunctions when they install it.
  • Lack of warranty. Many manufactures track their products via serial number and won’t provide any warranty if they’re not in the continent they were initially distributed too. To get around this many online stores simply remove the serial number. This will net you the same result – no support at all.
  • You have no avenue for returns much of the time. If you get a new set of speakers and they don’t fit into your car, many local stores will gladly take them back. This is very rare if you’ve bought them online.

Part four - What are the negative consequences for the industry itself if you’re not supporting it?
Taking your business overseas doesn’t just impact on the local stores, but on many facets of the industry. Some of these include:

  • Stores close down due to being forced to compete with prices under their cost price. Importers close down due to shops not asking for any stock. The only winners initially appear to be you. But who will you turn to for assistance once all the decent shops are no longer around?
  • Information websites and forums like this one suffer because the funds they depend on (that come from shops and importers) cease to come in. This means less free information, advice and assistance for you.
  • The product itself suffers. As more and more people simply chuck equipment in their cars on the cheap, sadly many have very limited knowledge about how to get the best possible sound from it. This means that the entire quality level of the car audio industry goes down as a whole. There is a good reason why specialist shops are called 'specialists'.
  • Competitions suffer. Stores sponsor and run many of the sound offs we all compete at. Without stores it’s quite likely there will be limited (if any) sound offs.
  • Publications suffer. When stores and sound offs start disappearing, advertising is no longer required and feature cars are in less abundance for publications. Therefore; what direction are the rags like INCAR going to go?

In conclusion.
Now we're not fools - we appreciate completely that you can save a lot of money online and whilst we don’t like to admit it sometimes, we tend to agree that if you can legitimately save thousands off your product(s) then you probably ought. But don’t buy everything online to save yourself fifty dollars and then expect stores to bend over backwards for you. We’re all more than happy to help you regardless of where your equipment came from (i.e. we’re not ‘that’ up ourselves) but keep two things in mind. The first is; just remember you might just be shooting yourself in the foot by purchasing overseas and killing off the local stores. Secondly; keep in mind we need to make a living by charging a fair price for your install (read; fair price, not exorbitant price). Why not at least give your local store a chance to price match the prices you’ve found overseas before you send all your cash offshore?

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