Quote Originally Posted by psychos2
It may be possible depending on the model. There are ways to make the speaker think it is in a bigger box. If you add the right amount of fiberfill.
Not sure how much volume you can squeeze out with the spare IN, but if you take the spare OUT and build the back out of fiberglass you can get over 3 cubic feet (while still being able to pull the box out - if you didn't care about that you could probably get over 5 cubic feet!). A little bit of fiberfill helped my 12's (1.5 cubic feet was the minimum volume required for each sub) but I still wouldn't go below the minimum recommended volume spec of the sub.