Boom Mat 6"x8" Speaker Baffles
Crutchfield Customer Review (What's this?)
I use these to make rain guards for my drivers and not for what they are actually intended for. I cut them up so that only a portion is actually use over the woofer in the door to keep the water dripping down from getting into the voice coil and ruining the driver. For an actual enclosure, I'm not so sure these things would be stiff enough to work as one.