actually the ports must be longer to maintain the tuning frequency when using multiple ones, and the port size i originally was going to use was 4" single the driver seems ok for a sub build looking at the thermal and excursion limit calculations i can hit 100dB at 20 hz without any problems. the extension of the design is 24hz -3dB, in a room it may go down to 20. when running different drivers calculations through the designer i actually chose this driver over a sub driver because of the extension i could get, the excursion limit and thermal limits were pretty much the same. and that box was made for that driver bandphan. also according to the calculator 2 2" ports would not reach an air velocity high enough for chuffing (if the port is too small or you use too few ports its warns you the air velocity will be too high and cause chuffing.)