i put a single 10 polk in a box. it is mounted directly below the rear deck. I put spaces made of MDF and then used a 3/4 MDF sheet to make a large flat surface. i mounted the driver off th the side and then made a frame out of some scrap wood and fiberglassed all that. its a sealed enclosure about .88 cu ft. it has a small 250w/rms amp and a little .5 farad cap. i cut a little sheet metal to allow the sound to travel easier into the cabin. its not loud and boomy but it makes the factory system sound alot better.
