this is what ive learned about bandpasses.. theres no magical formula for getting them correct..the ratio is more of a starting point and you tweak the box from there..its also very woofer dependent as to how the subs will react given the environment in the 4th order.. singer knows what american bass, dc, his LMS ultras (and a few others) how they will react given the environment they are placed.. basically it boils down to test,test,test..the ports the hardest thing to get right from what ive gathered