Its okay to post your thoughts Donny, but all I was suggesting is you check audio frequencies...I would even bet your your best 15" sub will NOT produce much below 90hz, no matter WHAT the specs say
End users THINK they do because thats what the specs say, but anything below 70-80hz is usually low end rumble. Takes more than a 15 to handle that, 18" minimum with some serious amp power driving it.
I for one am quite aware the QSC's (even the 15's) do not produce anything like 50-60 hz, but the manufacturers like to put it in because on the test bench and in theory based on the speaker design they CAN. In the real world they cannot.
I tend to rely on SPL specs, but even then I am careful as a lot of times the THD is not rated alongside...I am with Diki in the THD is the most telling figure when it comes to clarity of sound for real-world gigging.
As I said in my post about the 10's a few times in bigger venues/more people I DO use a powered 15" sub with them. Small gigs the sub is totally un-necessary, in fact it only adds mud.
Cheers
Dennis