Box size is 37.5x17x20.5 tuned to 32hz. The car isn't the issue (I know not the best), but the last two sets of subs moved sound pretty well inside the car. Maybe it could be the break in or bigger amp..... We went pretty close to the specs that sundown recommends on there site. All I know is right now I should've stuck with the 2 Skar ddx 15s in the way to small box lol.... Money wise, not saying Skar is a better brand, just thought with the sundown in the correct box would've been instantly louder. Now I'm lookin at spending more money either on a amp or box, but I don't see it being the box if its built to sundowns specs.