DIY Supra Subwoofer System

Welcome to the "How to build your own high quality sounding Supra subwoofer system" Webpage!!!

Materials Cost: About $40.00 (USD)

Why I made this: Ehh, I didn't want something so simple as making a box to cost me an arm and a leg. Local stereo shops were quoting me $500+ just to build the box (fiberglass most likely) w/o the subwoofers! INSANE!

Materials:
Top/baffle: Medium Density Fiberboard (MDF), about $20 for a 4'x 8' 3/4" thick sheet.
Sides: 3/4" MDF
Bottom: Bottom of hatch/trunk sealed with lots of silicone and DAP brand expanding foam. It's the economic way of sealing it and easier than working with fiberglass since you're only closing off small uneven gaps in the hatch floor. The expanding foam is working out great and has been since January, 2000. The box is secured via a small metric bolt (with big silicone'd sealed washers) through the top baffle into the threaded spare tire holder.

Dimensions:
Width: 26"
Length: 23"
Depth: 7 1/2" (Including 3/4" top piece/speaker baffle)

Quick Specs:
You will want these following pieces of wood cut:

(2) 6 3/4" x 26" x 3/4"
(2) 6 3/4" x 21.5" x 3/4"
(1) 23" X 26" X 3/4"
<--Click the picture!

Internal volume: The dimensions call up about 2.5ft^3, but subtract the spare "hump" and subwoofer displacement...it's closer to about an even 2ft^3.

Brian - brianb@briansbackyard.com

The Rockford Fosgate 250a2 (rated at 250x1wrms into 4 ohms) is sending at least 250 watts continuous to 2 JL Audio 10W0s ([wired up into 2 ohms] each seeing at least 125 watts continuous)...SQ is superb for this setup...say 85% SQ and 15% SPL capabilities...it'll get LOUD and play decently low, depending on the music, but SQ is compromised greatly.

Installation pictures: Reread what I wrote above and correlate them with my install pictures below and you'll get the general idea of how the installation goes.

Steps:
1. Create 4 sided box.
2. Create baffle that will sit flush on 4 sided box.
3. Lay 4 sided box into the hatch and even it out so it doesn't end up crooked ass.
4. Optional: Place baffle on top of 4 sided box and measure where the stock spare holder/threaded tie down is to help secure the box in the hatch.
5. Apply generous of silicone [I like clear] to the small uneven gaps under the 4 sided box and hatch floor.
6. Let this dry for a few hours.
7. Make sure everything is evened up. Go to step 8.
8. Apply expanding foam at the bottom of the 4 sided box, I used the DAP brand that I found at my local hardware store...it was something like $4.99 for one bottle-which is all I used for this box.
9. Let this dry...I let mine dry over night with the hatch popped open.
10. Once again, make sure everything is even and then go to step 11.
11. Trace your holes with the the subwoofer cardboard cutouts that came wrapped around your sub onto the top piece/baffle. The circle cardboard cutout is the exact size of the hole your subwoofer will fit into. If your sub(s) DID NOT come with a circle cutout...it's usually the main piece that's folded over to secure the sub...then you're ass'd out, my friend. :) Time to break out the compass or some string and a nail.
12. Cut out your subwoofer holes....make sure they're even and there aren't any big gaps.
13. Using Elmer's glue and some silicone, attach the baffle to the 4 sided, now 5 sided box, 6 including the hatch floor. See step 14.
14. Using a nice counter-sink, counter-sink holes about 4-5" apart. Make sure you've used GENEROUS amounts of Wood Glue and Silicone. You can always clean it up later, which isn't too difficult.
15. Using 1 1/2" coarse woodscrews, secure the baffle down and let dry for at least a day.
16. Install your subwoofer(s) and follow the break in period. Usually 2-3 weeks of low volume listening if it's in your daily driver; otherwise about 10 hours of low volume playtime.
17. Step back and enjoy! You just saved yourself a good $200-$300 with one weekends worth of work (well, it can be done all in one day, it's the drying time that adds length to the install.)
18. Optional: Choose how you'd like to 'present' the sub(s). Some people just leave the stock carpet on top. I cut the hatch carpet to show off these babies. Here's a suggestion: Go to your local fabrics store and buy some carpet color matched to your stock carpet. Take your stock carpet and trace it onto 1/4" hardboard. Glue the carpet down, with some rubber cement, to the traced 1/4" hardboard. Fit it back in, cut circles for the subs, and from here you can install grilles on the 1/4" hardboard to protect your subs. Getting to the hatch area, if you've stored tools back there, is easy. Just remove the 1/4" carpeted hardboard and voila!
19. Once again, Enjoy!

EDIT: You can use a tube of silicone to create a gasket between the bottom of the MDF enclosure and the trunk instead of using the expanding foam. This is the fastest, and most economical way of sealing everything up, and it'll create a much better seal than the expanding foam. This way is recommended with this subwoofer system!