A friend of mine wants to put a system in an old school Volkswagon. He is going to put 6 10-inch woofers in the box. It might be a while before we get back to work on it, he is going to order the woofers Monday, and the new headliner (and Dynomat in the roof) will be put in it next week.
And it sounds really good. The 6 woofers share about 4.25 cu ft of air space. They are all 8-ohm woofers wired parallel for a final impedence of around 1.33-ohms. The amp is a Planet Audio Big Bang BB1400.1, that delivers 1400-watts at 1-ohm. The box is sealed and the bass is super tight and accurate. It sounds really good. Right now there are only two 6-1/2-inch speakers up front (the other amp) but we will be adding two more speakers. Door panels are next, but it will have to wait until school is out.