At my venue, I have a pair of QSC K10s mounted on the wall, behind the head table. I've had the subs at either end of the table, about 12 feet apart. Just experimenting, I shifted the subs back against the wall, behind the table and facing each other, about 6 feet between them. I'm completely amazed at the difference in sound. I had the subs at 75% but had to pull them back to 50% and they still pound hard. Actually sounds like they're hitting deeper, more like 18s. Better definition and overall much more bottom end going on with this setup. Just thought I'd share the results and invite discussion.