I figured I'd post this here instead of the BS section. Built version 2 of my console sub. The old one had one rear firing 12. This one has 2 downfiring 12s. Finished it tonight and will put in tomorrow. This is for a crew cab Duramax.

Built box and braced it.
http://img408.imageshack.us/img408/8213/pb200087.jpg (http://imageshack.us/photo/my-images/408/pb200087.jpg/)

Painted bottom black and upholstered.
http://img841.imageshack.us/img841/3764/pb260094.jpg (http://imageshack.us/photo/my-images/841/pb260094.jpg/)

Put in T-nuts to hold woofers tight and wired with 14ga. Sealed holes with silicone. All the stuff in the box is, you guessed it, Liquid Nails.
http://img838.imageshack.us/img838/1061/pc010107.jpg (http://imageshack.us/photo/my-images/838/pc010107.jpg/)

Broke out 2 Dayton Audio 12" 4ohm DVC subs optimized for small sealed enclosures.
http://img94.imageshack.us/img94/3485/pc010108.jpg (http://imageshack.us/photo/my-images/94/pc010108.jpg/)
Aluminum cones and big magnets.
http://img823.imageshack.us/img823/3867/pc010109.jpg (http://imageshack.us/photo/my-images/823/pc010109.jpg/)

Loaded box and braced the bottom with 1/8" X 2" angled aluminum where it contacts the floor. Used single side sticky foam rubber tape to seal woofer to box. Completely airtight.
http://img840.imageshack.us/img840/7554/pc020111.jpg (http://imageshack.us/photo/my-images/840/pc020111.jpg/)

T-nuts should have been installed before upholstery but, did not plan that far ahead. They will be on the floor between the seats for the most part.
http://img27.imageshack.us/img27/3597/pc020113.jpg (http://imageshack.us/photo/my-images/27/pc020113.jpg/)

Side venting to let sound out. The rear is open and it vents to front as well.
http://img141.imageshack.us/img141/5861/pc020118.jpg (http://imageshack.us/photo/my-images/141/pc020118.jpg/)

Should make some super tight clean bass.

Box:
.85cuft per sub.
Q of roughly 0.8

Subs:
Wired in series at each sub and parallel at amp.
(2 coils 4ohm in series=8ohm, paralleled at amp=4ohm nominal)
700watts RMS each/1200watts max

Best thing is I lost no legroom or seating capacity.

nice!
should hit real nice and super tight!

What wood is best for one of these and where to you find the upholstery? I need to make one for my truck

What wood is best for one of these and where to you find the upholstery? I need to make one for my truck

I find you cannot go wrong with 3/4" MDF. You can get it at Lowes, Home Depot and probably Menards (do not have them here in AZ).
Birch plywood is recommended by box builders as well but, a 5'X5' sheet is like $75. Expensive stuff.
A 4'X8' sheet of MDF is like $40.

I got the upholstery from a fabric store but, stores like Michaels, Jo Ann and other fabric stores carry vinyl as well. Just make sure you use the Marine Grade vinyl. It is thicker and tougher. I wrapped the top box in 1" high density foam tacked on with spray adhesive then I wrapped the whole thing in 1/8" closed cell foam tacked on with a spray adhesive. Foam keeps the surface of the vinyl appearing more smooth.