Ok so i plan on getting an alpine typ-x 12" subwoofer. Its recomended for a 2 ft3 box wich i can fit in my rig. I can only go depth wise 11" though. I downloaded winISD and have been playing aorund. I cant seem to calculate a decent port size with decent tuning. The optimum tuning for it is 18hz Can anyone help? I can go lsightly bigger and smaller of course. Thanks!