basic question

[wafsman 0]

what would be the minimum amount of space i need in between the back of the sub and the back of the box in a sealed enclosure?

[altoncustomtech 773]

Generally that depends on whether or not the sub has a vented pole piece. If it's not got a vented pole piece then all you need is enough space to keep it from bumping or rattling against the back of the enclosure should things flex a little. If it has a vented pole then you'll want about the same amount of space as the diameter of the vent. If the pole has a vent that is 1" in diameter you should have about an inch of clearence so that the vent will breath.