Let's look at these one at a time:
Originally posted by xbladr
I am wondering what are free air subs. I saw some enclosures for them and i want to do one for my civc because i like them alot.
A few things going on here...first, let's talk about free air (also called Infinite Baffle) subwoofer systems. These subs are intended to be placed in an infinitely large enclosure, meaning you can use your trunk as the enclosure, so long as you seal the trunk off from the cabin that you are firing the woofers into. The best way to show an example is to look at the 6x9's in the back shelf of a car. Notice the back wave (the sound waves coming from the rear of the speaker) play into the trunk, while the front wave plays into the cabin of the car. If the front and back wave mix, you get cancellation...and that's bad. Sealing of the trunk (in this case) is very important. There's a lot more work then just mounting the drivers on a baffle.
There are no enclosures for IB subs, and I don't see how you could like them when they don't exist...
Also is it possible to hook all 4 of my speakers to a 2 channel amp? thanks
Depends on what speakers we are talking about, and what amp...more info please.