i had 35hz on 2 12 lvl 3's, it KILLED the lows. it had 2 4" aeros (flared) 1.6 per sub. i put that box in my sebring firing foward and it wasnt low enough for me.. AND i took out both subs and put one 12 btl in ther and covered the other hole (lol) but still wasnt low enough for me.. i think i might just say fuck it and do 30hz. but i want to break 140db.