35 hertz 2.5-3.0 cb ft.
for most 12's, i agree. there are 12's that go in 3 cubes though. kicker L7 is an example. old rockford hx2's needed quite a large box also, so there are some 12's that do need that large of a box.That's too big for a single 12" Only reason you'd go that big is if you were building a EBS box, and you'd need a tune to match, like 25-30Hz.