I have a 12" JL W1 which requires 1.25 of air space in a sealed box...
The only 04-08 under seat boxes I can find for a single 12 only take up the driver side and center space, which doesnt give me enough air space.. only about .68 tops.

If I buy a dual 12" sub box which fills under the entire back seat of my Scab, and has mounting holes under the left and right sides of the bench, this will allow for enough air space for my 1 sub BUT theres an extra 12" hole in it...

SO my question is... if i can some how manage to seal the 2nd sub hole will my 1 sub use both chambers of the box allowing it to have enough air space?

 

Put about 1 pound of polyfill in the single 12" box even though the box is undersized. With cabin gain, this will give you great response with the w1. I used 2 JL 10w1s for a while with half the recommended airspace with the polyfill and it was perfectly fine.

 

whats polyfill??

 

Walmart in the pillow section. Helps the sub to perform as if it is in a larger box.
http://www.audiojunkies.com/blog/134...osure-resource