4th order help please

[Brent Shade]

I built my first 4th order it sound OK but I think I tuned it wrong I have 2 t7 15s each sub is in 1.5 pur sub and the port area is 7.6668 the port is 8 high 20 long 8 deep I've thought about putting a 12 x 3.5 port in what do u think I should do

[afrakes]

This is confusing. Just to clarify, each sub is in 1.5 cubes sealed and firing into roughly 3.75 cubes ported per sub? And u currently have 200 square inches of port? What is ur ported section tuned to?

[afrakes]

I'm no 4th order expert at all but if that's ur box setup it seems to me like you have way too much port area. That's over 26 inches per cube. And remember, the lows come from the sealed section so you want your port tuned high, low 40's usually but all depends. And this not very much space for the woofers sealed. Don't know anything about your subs so maybe it's fine but just generally seems a bit too small. I wouldn't put a 15 in anything less than 2 cubes per sealed.