Each different driver will have a spec for its ideal box volume, an the manufacturer will have that spec for you. In most cases, that number is bigger than the .52 cubic feet my box has. For example, my JL sub called for a box of .65, if I recall correctly. You can add fiberfill to the box to increase its effective volume, and in my case JL recommended that I add about 1 pound.

MDF or plywood is available in various thicknesses, but 3/4" is easy to work with and makes a good, sturdy box in this size range. You might be able to get away with 1/2", but the difference in increased box volume is fairly small, and I'd rather have a more sturdy box. With the FatMat applied, my box is acoustically "dead" as far as I can tell. If I rap my knuckles on it, it makes a sound like a solid block of concrete. You don't want the box to resonate and absorb any of the audio frequencies from its sub. My box is also lined inside with a layer of fiberglass resin, to assure that it's airtight, and both the sub and speaker terminals are sealed with caulking.

FWIW, this sub type isn't for everyone's tastes. It's not going to rattle your hatch or win any sound level contests. I was looking for a system with clean, tight bass at reasonable listening levels, and I also wanted my system to appear as OEM as possible. Both of the JL amps and other 4 Boston speakers/crossovers are also hidden. The only visible give-away that my system is not OEM is the Kenwood HU.

 

I will contact Alpine to see what they recommend.

Materials:
-3/4 MDF
-silicon caulk
-sound deadener

Anything else? Do I need to use screws or braces?

I agree 100% with your last paragraph. I am just looking for a clean sounding system that is better than OEM but still is visually the same. I don't care for outrageous bass, don't listen to my music all that loud. I already have 4 speakers and the 2 amps hidden in the glove box - one for sub and one for the speakers.

 

Yes, you want to use screws to screw the boards together. What I did was I cut the boards to make the box the same size as Dean. Screwed them together (MAKE SURE YOU PRE-DRILL!!!!) Also used wood glue in between the boards and then used Silicone to seal the box and the terminal plate.

 

You beat me to it - lots of screws, at least one every 2 - 3". I prefer latex caulk to silicone, though, as it's easier to work with, but either will work fine. You can buy a bag of fiberfill at any Walmart for a few $, as pillow stuffing material. When I bought the FatMat, they had a good deal going for 40 square feet (with a knife, roller, etc.), for something like $45 shipped.

 

Okay thank you for all the help so far! I am going to start collecting materials and attempt to make this sometime in the next few weeks.