I needed a shallow mount sub for my truck and I was limited to 1 cu. foot of volume.. The box I built is ported, loosely packed with polyfill, and tuned it to 33 Hz. It's hooked up to a Kenwood 500 watt (RMS @ 2 Ohm) amp and this thing will literally make your eyeballs vibrate in your head. It sounds great and is a lot louder than a sealed box. It's great for a single sub setup with limited space.