I have no clue about ported boxes. I would like to build a ported box for my 15" thumpers for spl, but need advice on size and stuff. If somebody has time... Thanks!
Sorry I don't have any advice, but you gotta tell me your score when you get everything setup. My 1 Crystal 15" in a vented box tuned to 35hz is UNBAREABLE at full blast. I can't imagine 2 15's vented tuned to 35hz.
35hz seems to be a decent SQ tunning with awesome SPL.
Don't be surprised if your riding one day blasting your music and you look in your rearview and see a trunk-lid lying in the street that looks like yours,lol. Bcuz it WILL be yours,lol.