I too have been thinking about building a custom sub enclosure for my rear door tire well. Since I have oversized tires on my VX now, the donut is really just taking up valuable space. With a full size spare mounted on the roof, I've got a few cubic feet of space to drive two 12" subs in the rear door.

I was considering using fiberglass, but have no experience working with it and think I could do a much better job using MDF. It wouldn't utilize the space as efficiently, but a sort of octogonal shaped box could be built fairly easily that would give me the volume I'd need. It would likely be quite heavy though, so I would have to bolt it to the two support rails that run vertically inside the door.

I haven't decided how to modify the plastic cover yet, although I was considering cutting an oval shaped hole with a carpeted panel that would stick out about half an inch or so. If I could get someone to build me a custom fiberglass panel so that I wouldn't have to cut my stock one, I'd certainly consider that option also. Any takers?

I'm a little concerned about something WormGod mentioned though:

Originally posted by WormGod
As for vehicle response with 2 12".... it isnt so good. I already attempted 2 subs and the VX simply is NOT the vehicle for 2. The bass response is good in the VX but the thump and vibration drove me insane. Even with Dynamat, it was like sitting in a cheap hotel vibrating bed.
Has anyone else had any experience, good or bad, running two subs in the VX?