Speaker Placement Is King!
I'm in the process of once more proving this to be the case. I've been working on this big dip, no - not my buddy, a really deep dip between 60-70Hz that only shows up when both Large Fronts are playing the same signal. I go through the process of tweaking with no correction, then only after running Dirac does the dip show up. Dirac is only correcting "each" speaker, not multiples, so there's cancellation going on here.
I've played around with some absorption panels and some extra bales of rock wool and have gotten mostly minor improvements, but nothing that would indicate any "a-ha" moment. Today I did discover a half a-ha with placing one panel inboard of the Right speaker that is close to a corner, but then decided I needed to move the speakers first, something I have not wanted to do! But I did it anyway. So after a half hour I started getting some remarkable improvement!! The speakers are closer together - something I DON'T want but form follows function, and 7" farther from the front wall. I did no tweaking other than moving the speakers, then ran Dirac, and viola! (voila') the dip is less wide and a lot less deep!
Again, no tweaks to the subs or speakers, no room treatments, just moving the speakers. If Dirac is happy, then so am I. I use the Curtains in Dirac to keep the correction to below the crossover of the 13A's. I have yet to be happier with using Dirac on the stat panels, it's just not quite as "lively" sounding, but I'll take all the help I can get in the bass region.
I'm not finished, just taking a break, but wanted to post some good news.