ported

exterior dimensions of 36x33x17 exterior dimensions with ports 3"x10" one per chamber. Thats using 3/4 mdf and taking into account sub displacement. You dont need anything bigger than that and that should make those subs slam. If Im not mistaken they will be tuned to about 27hz so that design is more for everyday listening. If you want to use it for spl you make want to change from round ports to slot ports and make a couple that are interchangable so you can put in ports that are tuned to a higher frequency for spl and lower for regular listening. I think I read your post right and it said you had 4 12's, if not than disregarde this post, your tag says you only have 2 so I wasnt sure what was right

No, that is total box dimensions. Just sererate it internally with 3/4 mdf. That gives you like 2.2 cubic feet per sub which should be lots. As far as the ports go, make square ports with different lenghts to get different frequenzies. I cant remember off the top of my head the dimesions for the square ports but you will have to figure it out for your own application/vehicle anyways. Hope that helps some.