bazooka sub

I used to build those out of thick wall PVC pipe sized to whatever speaker I had available. Typically 6" to 12", cut the tube to resonate at whatever frequency is near and dear to you and voila'!

Here's a good article on the Bazooka bass tube.

http://www.carsubs.net/boxesdesign/tubesubwoofer/subwoofer-tube-enclosures-explained