Car Stereos: sub box building & bracing, center divider, bottom depth

Question
Hello Brian,

Due to some issues with a previous dual 12" sub box somehow getting mold and moisture into the chambers, I've decided to take on a little project and build my own wedge box. I was gonna buy a pre-made box somewhere, but I wanted to be sure that it would be built specifically for the subs recommended measurements and one that I could put some kind of sealant in to keep moisture out. Now keep in mind, I have never built a sub box before.

So I have the dimensions planned out for a wedge box (using 3/4" MDF) having a height of 16", a width of 31.5", a top depth of 7-9/16", and a bottom depth of 10-9/16". If my calculations are correct, each sub chamber will have a volume of roughly 0.95 cubic feet (which is what I understand to be the recommended volume for my subs).

Now someone brought to my attention about using braces but didn't go into great detail about them. Since I have no experience in making boxes, I was wondering what he meant by braces, what they look like, what they are for, what they are made of, where they go, what size they are, et cetera. So if you could help me out with advice about them (or anything else I should know about building a box) I'd appreciate it.

Thanks Brian!
Erik

Answer
Hi Erik,

In internal brace is just a piece of wood that's placed between two walls of the sub box.  Whenever you have a large, flat piece of plywood or MDF, it will tend to resonate or flex with the changing air pressure in the box, and with the vibration of the subwoofer cones.  In your box, the largest sides will be the front and back pieces, so placing a support strut between them in the middle can help keep both of them from flexing.  However, what I'd suggest is just designing your box with a center divider piece, so that each sub has its own sealed chamber.  There are several advantages to using dual-chamber boxes, and one big advantage is that the center divider will serve as a very effective brace.  Given your box dimensions and materials, I don't think you'll need to use any additional bracing if you use a center divider piece.

Hope this helps!

Brian