Here is the basic breakdown for each size sub, in cubic feet: 6.5"(.4-.6), 8"(.7-1.0), 10"(1.2-1.5), 12"(1.7-2.5), 15"(3.0-4.5), 17"(4.5-6.0). The port formula is 15-16 sqin of port area for each cubic foot of box volume, port 16 inches long. Remember, the port is tuned to the box volume, not the sub(s). and they tune all subs it looks like 40hz
4.5-5 CUBES