Jarery wrote: Wow lots of toys, looks awesome.

I had similar looking response as yours. www.goldenear.com/forum/Show-Off-Your-Go...f-a-work-in-progress
Actually yours looks way better other than the null at 40. I have since moved the subs on mine and achieved a much flatter starting point prior to running room correction software. I posted new graphs showing how I basically removed my null at 48hz, but its not been approved yet so isn't showing up.

I'm hardly an expert as I've just been learning this as I go and experimenting. But this site helped find better placement for my subs. www.padrick.net/LiveSound/CancellationMode.htm
Which according to it if you're having a cancellation at 40hz means the boundary condition causing it is around 7' away from the speakers. Your ceiling would be my guess. I'd recommend placing two of the wall panels that you currently have on the front wall and try them on the ceiling at the reflection points between speakers and main listening position as an experiment and see if that reduces it.

I've not used Dirac but I have used REW. The chart shows just the left and rights without the sub, and from the picture it looks like you also have LFE going to the Tritons. I assume the posted graph is Left + Right in a 10-20k sweep without sub channel? Does it flatten out when you run the fronts and the sub together? You could run them as I now currently do, without LFE, set to large so they run full range, and use your external sub to handle LFE duties. Then place the sub on its own based on where the graphs show the flattest response.

From what I've read bass traps below 100hz are not great since they need to be like 6' thick at that frequency to do anything. At that point the recommendation is to add multiple subs to cancel the nulls and EQ's like MiniDSP or Dirac to lower the peaks. You can try adding an EQ boost at 40hz to see if its an eq correctable 'dip' vs a room mode 'null'.

Good Luck

Edit: just looked at the pic again, you dont have LFE going to them.

A BASS TRAP in the ceiling at reflection point - I had not thought of that!! Definitely have not tried that placement - will explore effect and report back. Thanks!

Forgot to ask. Is your main seating position in the middle of the room?
If you move the mic back 3-4 ft does the null go away ?

An update on my 40Hz suckout issue: I had tried many speaker positions before in my squarish room, but had never gone to the rather weird Cardas recommendation for a square room listed here:

www.gearslutz.com/board/studio-building-...eaker-placement.html

The results as measured in REW were impressive, for the 1st time I was able to kick that suck-out up a bit (green line is using Cardas recommendation):

farther in speakers by Jose Sifontes , on Flickr

I tried placing a bass trap in the ceiling - it helped in other areas but not in the 40hz are. I guess you can never have too many bass traps in a large basement. Moving the seating position a few inches back (a requirement given where Cardas recommends the speakers be) also helped a little.

I have been testing stereo listening with and without Dirac on. Almost in every case it sounds better with Dirac on.