I deleted my last post but I should have left part of it.

I think the suckout on axis centered at 180hz could be due to SBIR effects. Looking at the measurements across the listening area the suckout disappears as the measurements are closer to on axis of a single speaker.

I originally posted the formula from acoustic frontiers

Sbir frequency = speed of sound/(2x(direct path-reflected path))

In my room the front wall reflection adds 38" of travel (the distance from the front baffle to the wall)

So sbir frequency = 1130/(3.2x2) = 176hz.

BUT

The vanilla formula for sbir, not taking into account the reflected path is

SBIR= speed of sound/(4xdistance to boundry) This uses the 1/4 wave distance cancellation due to phase interaction -but doesnt take into account listener angle. I think the original formula I posted is better for this instance and the 1/4 wave formula better for subwoofer modal predictions.

Since we are talking about adding absorbtion to the front wall, I'm trying to predict the best outcome and share the results with you guys. I'll try absorbtion directly behind the main speakers on the front wall. We'll see. smile