my sub needs a port thats 4 inches in diameter and 10.75 in long. i cannot find a port this long can i use two 4 x 5 in ports to get the same effect? if not is there a web site that sells ports this length?
No you cant use two ports. That'll actually raise the tuning, tuning depends on the friction of the ports surface area, obviously w/ two ports and less length, friction will be much less. Anyway, you have to get PVC pipe and cut it to the length you want.