I built a box and went the aero port route. I bought what i thought was 4 inch pvc until i got home and measured it. turns out its 3 1/2 inch outer and 3 inch inner diameter. When I first inquired about aero ports, someone told me i would need 3 4 inch ports 18 inches long. i have 3 3 inch aero ports instead. Box dimensions and 12' high, 29' wide and 36' deep. Anyone know what im tuned to? The sub is an AQ HDC3 18.