ok so i bought a ford ranger and wanna put 4 XL 15s D1s on 2 Cresendo strapped , what would be the air space on a ported box to hit really good, dont kno if im going with a blo through or i might just get a topper and build a wall , but for now i need to kno the specs so i can get to figuring out shit ,,, this is totally gonna be a new build from scratch so if i can get any help i can start the process thanx