Is it true that the bigger the box the louder the sub will get, like 2 15's in a 10cuft tuned to 32hz will get louder than 2 15's in a 8cuft tuned to 32hz with both boxes giving the same power?
are you using win isd? basically the graph you view is in theorey correct but it's not so. There is a peak "loudness" to every box. If all we had to do to make a sub loud was increase boc size then we should have records way higher than what they are now. Try to stay within the manufactuers recommended box sizes unless you are going for straight spl. If those 15's are designed for large boxes like that then yes you will gain some output. or at least you should.