Posted May 31, 201015 yr i have another buddy looking to get a 18 inch btl and he wants to build the box before he gets the sub....seems like a bad idea to me lol dunno why but i would like to know how much sub displacement to account for when building the box for a single 18 btl...he refuses to listin and jst gets all pissy when i tell him to get the sub first then make the box to fit it....so before he does somthing stupid i was thinking maybe this info could be found here.....