because its over 7" deep and it moves over an inch outward(the cone) and the motor is a huge size in diameter. figure 8" out using a build too box (using 3/4" front mounting board) then u need at least an inch free in front so doing a dramatic install u need at least 9-9.5 inches. have you looked azt pictures of these subs? the d2 and the brahma are pretty huge to show u what i mean would look like this l