I purchased 2 of these PX10 subs for my nissan single cab hard body work beater. Not much space behind the seat. Since they were so cheap I figured I needed 2 to make up for the lack of quality. Well i was WRONG. I wanted just a little something to fill out the music and honestly 2 is too much. Even with less airspace than recomended they hit really hard. They recomend .6 cubic feet for sealed and 1 is in .3 cubic feet and the other is in .2 cubic feet both have polyfill. Well even with that little airspace it suprised the heck out of me. I have a planet audio VX1400D amp pushing them and wired down the amp is like 50 watts too much but i have it turned down some. Really Really Really satisifed with the sound and would recommend these speakers to anyone needing shallow mounts. Like i said 1 would sound great and 2 pretty much slam.