You can measure the volume of the enclosure using packing peanuts. Fill the enclosure with peanuts and then, transfer the peanuts into cardboard boxes of known volume to get the actual enclosure volume. A 12"x12"x12" cardboard box = 1 cubic foot. The rest is easy.
I can't wait to see the finished box!
You can use strips of soft rubber under and behind the enclosure to decouple(isolate) it from the body of the car. I am giving up old tricks here!
133whp-126ftlbsTQ Eclipse CD8443,JBL Px300.4, JBL GTO7001, PPI 356cs, JBL p1024(Hooray!) SubThump enclosure, RAAmat BXT, Damplifier Pro
Hatch Nation #140
Caeci caecos ducentes