these guys are right, but if you have no other choice, i would at least try to add length to the port to bring the tuning down, the box in my truck for a single 12 is slot ported, i built it with a 15x2 port cant remember the length but i got it down to around 35-36hz, low as i could go due to the port too close to the magnent on the sub, but in your case what i did to my buddys box was fairly simple, just pull front plate semi carefully and make the port and port length the desire... works great..