4 - Sub division

The tutorial of the boot buildout is going to be split into three different sections due to it being such a large area to cover. The first area we are going to cover is the subbox and surrounding baffle plate and trim panels.

The first thing Marty did was construct a mock-up subbox to check sizes that were first measured and to check clearances thoughtout the boot during normal operations. Seeing as the spare tire was to be retrievable, the sub box has to be moveable in order gain access to the spare, hence it must have the ability to be removed from the car. This took Marty a few goes to get the exact height and size of the box just right. As you can see from the images below, the box fits in with a mere 4mm of space between the rubbers. What was that about the tightness of a fishs bum?

After the final dimensions for the subbox are decided, the real box is constructed. Marty takes no shortcuts when constructing subwoofer boxes as internal pressures inside sealed the boxes can reach frightening high levels. The box itself is constructed from 1" MDF which is glued, biscuited and and screwed every two inches for rigidity. After this the box is internally sealed with liquid nails to make certain its airtight. The exterior of the box, even though it will never be seen, gets the same level of treatment too. Anyone who has even seen water hit MDF knows that it expands and corrodes very fast when moist so the outside of every one of our boxes gets coated with polyester resin to make them virtually waterproof.

The box design was quite complex to get the required 2.1'³ and the front was kept flat for two reasons - one was to hold the three subs on the same plane for sound quality reasons and the other was due to tight space configurations within the Slivia. Marty would have liked them angles out in a more semi circular fasion but the box would not be removeable then. "The width and depth is very limited in these cars." There is actually only 2mm bewteen the outer edge of the subbox and the boot hinges. Tight fit huh?

From the inside of the car we start to get the look and feel of how the front of the box will look when in place. With the plexiglass window in place, the front of the subs (remember they are to be facing into the box with magnets exposed in the boot). Two different red neon tubes will highlight the face of the subs and a mirrored glass panel with sandblasted Boston / Zapco logo will sit on the bottom, further adding to the effect.

The front baffle plate for the subs was made from fibreglass and is painted in the same two-pac colour as the Silvia. This will be deep sunken to protect and add visual impact to the Boston magnets when the boot is opened. Seeing as this surround is for visual impact only and doesn't hold any structural support, it is constructed only from fibreglass without the standard carbon fibre / kevlar support layers all our fibreglass subboxs have built into them.

The first thing done is the marking out of the trim ring used as a template for the three tens. Once this is cut out and deburred, the guides for the glass mat are screwed on and set-up. These guides are constucted using laminex and is bent to a certain radius before the screwing and glassing is done.

Once the fibreglass resin is mixed, you only have a small amount of time to lay the resin over the glass before it begins to harden and set chemically. This is the time when you need to make sure you have a helper to mix the resin (thanks again Little_1) while you get the glass cloth just right. Be carful about the resin though - if you don't have enough hardener it won't harden and if you have too much it will get very hot and in extreme circumstances actually catch fire.

The polyester resin drys quite quickly and it can be very messy to work with. Make sure that you have copious amounts of acetone lying around because the glass mat and the resin gets everywhere. Try not to inhale the fumes either as you'll pass out.

Here we are half finished and the baffle is starting to take shape. All up three layers of 10oz glass matting were used on the front and another two layers will be used behind once the plate is taken off the front of the box. This behind layer is just to give the baffle strenght.

This is the first shape of the entire baffle completed. This shape will be modified a little from what it is currently but this will be done once the baffle is removed from the front of the box. The baffle stays screwed to the front of the box throughout the entire glassing process to prevent bending as the fibreglass drys hard.

Once the fibreglass goes hard its time to remove it from the front of the subbox. This is done after about four layers of glass cloth have been laid down. If you try to remove it before then, the plate will warp out of shape.

Let the sanding commence. This is the biggest single hated job of installers. Marty begins the sanding process that starts at 40grit paper and continues right down to 2000grit to finish. As he holds up the baffle we get out first real idea of how it will look.

QUICK NOTE: Due to Marty's journism commitments, the Silvia was put on hold (ie the system changes every two weeks for now).

Previous Page Concept art and drawing.