Xterra Under Seat Subwoofer

I wanted to find a solution for getting a sub woofer into my Xterra with out sacrificing cargo space.   I found some plans for an under seat sub on a Frontier forum.  I converted his drawing into a simple Google Sketch Up file, and built it.  The under seat area seems to be the same between the Frontier and Xterra.

Here are the drawings I came up with based on the above URL:

I used 7/16" birch ply and carefully cut out the pieces on the table saw.  It was rather tricky coming up with a cut list.  The overall height of the box cannot be any bigger than the above listed height (even a 1/4" would make it too big!)

Once all of the pieces were cut out, I used wood glue and brad nails to hold it together.  Once the wood glue dried I sealed the box up with silicone.

Here is a picture of the finished box:

A picture of it installed (excuse the install mess):

It sounded great for what it was.  I felt that it lacked low end bass.  Before bolting the seat down make sure you do something to sound deaden the underside.  I didn't and the seat rattled on certain notes.