Re: QSC KW181 stacking (placement) - NEED ADVICE!
Putting the 2 subs together will maximize the amount of noise they can make. If they are right next to each other, they will acoustically couple (effectively become 1 radiating surface) and will be around 3dB louder than when they are spread apart. It doesn't matter if they are on one side or the other, or right in the middle.
The crossover will help. Right now your tops are trying to reproduce those low frequencies along with the subs. 2 different types of speakers playing the same thing will cause all kinds of problems. There may be cancellations happening that would cause a suckout at the frequencies you"re most interested in.
At the very least, you will be able to drive the tops a little harder with the crossover in place since they won't have to play the low notes. It will sound cleaner too.
Don't mistake a cleaner sound for "less loud". Distorted, nasty speakers sound louder too our ears. Even when they're not that loud....
