So, I finally got around to installing twin 8" subs in the rear deck (free-air). I used a couple of Audiobahn 8s, and the installation took the better part of a day. I had two appropriately sized holes in the rear deck cut at the body shop (next to each other on the passenger side of the car). I made a baffle out of 3/4" MDF and bottom-mounted the subs to it. I used lots and lots and lots of sound deadening material including poly-backed roofing material and carpet padding.
Overall, I'm pleased with the performance. The bass extension is surprisingly deep for 8s. The sound bumps a bit more than rear fill now (like the previous single 8 in the rear deck) and it's pretty tight. I'd equate overall performance to an average 10 mounted in a sealed box in the trunk. But, I lose no trunk space and have very little trunk rattle.
Curiously, the bass seems a bit like a bandpass enclosure. You can tell when the sub is playing in its sweet spot. I was expecting a flatter response, but I like the little extra bump.
I'll post some pics of the install from start to finish for anyone interested when I get back home from Detroit tomorrow.
Edit:
Here's a link to the pics -
Dual Rear Deck Sub Pics
