the 28hz would get lower and not be as sloppy.. the box for 40hz would get louder when it peaks and at higher frequencies but would not hit the lows well at all... what are you trying to do?
im about to try and build a friend of mine a ported box for his 15" kicker cvr. He's putting it in a hynidai elantra. I havent had the time to measured his trunk but it looks like a 4 cu ft box will fit. but dont know what to tune it to he likes his music loud but to have clarity to. 60% spl 40% sql.
it will get fairly low.. if you want low low you'd have to tune to 28hz but then its not going to be more SPL oriented. 35hz will do him good. how many cube inches? 64? I'd build that box to be 4 cubic foot after displacement.. bigger box will make them lows lower...
