I have two sony free air subs from a demo car that sony built in about 96. They are built into the flippin hardest meanest shelf I ever had the misfortune to have to lift. And they sound great, will never be as crisp as a box but its a good compromise. So, from this you can take away that yes, free air can sound good, but, they need to be expensive speakers, and the build needs to be VERY rigid. Looking at the shelf its not something I'd ever attempt myself! Oh, and if it comes loose in a crash, it'll kill you.
