i want my ported box to be 2 cubic feet i want it tuned to 34hz so far i have 30Wx14Hx?D I cant figure out with a box calculator what my depth is, if i put it at 13.5 i get 21 square area for the port but if i put it at 14 i get 19 square area. so my question is what should my depth be for a box that is 30 w x 14 h so i have 21 square area port sounds confusing sorry.