okay my box is 20"hight x 40"wide x 20 "depth according to the speaker box tunning calc. its is 7.63cubic ft. now iam trying to figure out my port on it and the lengths i have right now is 7"hirght x 9" wide x 15" depth and i get 33.81 hertz its the hertz i want my box to be tuneed to but the port area per foot is only 9.14"sqaured and Fi says the port should be 12-16"sqaured do i have to cahnge the port to be 12-16"sqaured thank you for your help