I needed some low-end rumble to my system. However, I really didn't feel like having my t-top storage taken up by a pair of large woofers (I used to have 3 15"s in another car) Besides I don't listed to bass music any more, but I do appreciate the low quake of a good system occasionally. I decided that the sub box had to fit in the hatch, but still allow storage of the t-tops. So that only left one place- the storage well on the driver's side. That area is very small, so I really have to maximize the available airspace especially if I want to fit a 12" in there. So that means fiberglass to get every cubic inch I can.
Here, I just pulled the thin fiberglass form out of the car. (Sorry, i didn't get pics of the layup of the 'glass in the car- see the kickpanel v1 page to get an idea of how it's done) The fiberglass cloth was saturated with resin over layers of 3" masking tape coated in vaseline. Once the fiberglass/resin hardens- the fiberglass form is popped out of the car the next day to prevent the thin shell from warping. (If it's taken out immediately after it hardens, it is possible that it can warp as the curing process is still continuing)
The small piece is a mold taken from the top inside of the trim panel. This will be the top of the box.
The top piece has been taped to the main shell in the position in which it is to be fiberglassed in place. This was test fitted into the car a few times and will have 4 or 5 layers of fiberglass cloth and resin built up uniformly within it, making the box very strong. Remember, you dont want it to flex at all.
After the top was attached, I filled the enclosure with styrofoam peanuts, then dumped them into a square cardboard box to find the internal volume of the inside. The formula for determining volume in cubic inches is:
Length X Width X Height divided by 1728.
The total internal volume is .805 cubic feet. This isn't as much as I has hoped for, but it is within the acceptable parameters for the subwoofer.
I cut a front baffle plate out of 3/4" MDF, and after taping it in place and test-fitting it in the car, fiberglassed it to the inside of the box. I built up 3 or 4 layers of fiberglass making sure the plate was secured firmly to the box and wouldnt flex or move. The gray stuff you see on the inside is a concoction I poured in there to ensure there are no air leaks. It's called a milkshake. it is made by mixing a half & half mixture of fiberglass resin/hardener with body filler/hardener. The two mixed components are swirled around the interior of the box until it hardens, coating the entire interior making it leak proof.
I sprayed the outer face of the box with 3M Super 90 spray adhesive, and wrapped the face of the box in gray vinyl, stapling in place along the backside of the MDF face.
Here's the box finished and installed with my Elemental Desighns 12K.44 subwoofer installed. The available airspace inside the box after subtracting the mass of the speaker itself is .05 cubic feet above what the minimum requirements for this sub are. I will be feeding it 500 watts RMS from my Fosgate amps. The color of the vinyl doesn't match exactly so I'll probably re-wrap it in matching vinyl or dye the existing stuff to match.