gary808

Wall off the trunk/rear deck of your car, get a pair of beefy woofers, and give each woofer a bit of power (I would say 600+ watts per 12" minimum). Also get a good eq and a good subsonic filter.

I have a free air setup in my car... It's set it up so I could convert it to AP, but never did. Even though my baffle is almost all fiberglass, I'm not really sure it saved much weight compared to a small sealed 12". It plays deep but doesn't really crank considering how much power the woofers are getting. An AP setup would probably be even more inefficient.

NogaroGO!

subs designed specifically for free air use where as any sub (especially those with a slightly larger VAS) can be successfully used in an AP format do. Also because a freeair setup provides virtually no acoustic suspension, a sub must rely on its own suspension to control its cone movement. Whereas an AP setup does provided acoustic suspension, more power can be safely applied to a subwoofer. Though AP formats have a lower output than a conventional box, this is negated by the fact that an AP setup is firing into the cabin of the car whereas a conventional box must fire through the rear seats and rear deck (assuming the rear deck has not been ported). As in all things, there is always a tradeoff somewhere for everything.