Building a box and need to know whether or not my box should be taller in height where speakers mount. Or should my box go further back in depth to give more space behind the woofer? Thanks.

 

All that matters is the airspace, though the GENERAL recommendation is that the sides of the speaker be no closer than 2" from any adjacent/perpendicular side of the box, and that the basket have at least 2-3" BEHIND the vent.