What process did you use to integrate multiple subwoofers for 2 channel listening?

@audiokinesis 

Thank you, thank you! for your help. I'm saving this email and printing it out.

Here's the result of my work before your advice, over the course of the day. It's the top slide on my system page: https://systems.audiogon.com/systems/9064/edit

Might it be a floor-to-ceiling mode? Do you have a lower than normal ceiling?

Oh definitely. 6.5' ceilings. I told this to Dennis Foley and he said, bluntly, "Get another room." Sigh.

Thanks for the compliment on the Salks! When I did extensive speaker placement analysis (with the help of brownsfan) I found that 6'4" from front wall was optimal. Today, I've added a few inches more and had some luck with that. But the bass hump ain't moving much. A little but not enough. Nulls still painfully deep.

I'll try that overlap cancellation thing. Had not considered it. The Rythmiks use a line-in RCA so not sure how to manage that with them. The Rel seems easy enough.

I'll try stuffing some foam in those beautiful front ports.

I am a bit daunted by the idea of wiring a capicitor but it is probably easier than I imaging. I'll save this email for future reference.

Good to know that 3 gets me in the ballpark. I was under the impression that the idea was "Get 4 or go home."

I'll try to elevate one of the subs....closer to the ceiling. If you know a good orthopedist, that might come in handy.

There is one sub presently closer to me than the speakers. I'll try to roll off the top ends lower and steeper on that one.

I'm glad you mentioned deliberate phase variation between the subs; I was worried about keeping them symmetrical, but since the room is going to be different where each is, that assumption doesn't really make sense.

How high are you crossing the subs? Looks like it drops between 90hz and 500hz and another big dip between 2khz and 10khz. What does a measurement without subs look like? 

@djones51 In the image I posted yesterday -- which I didn’t label specifically enough -- the orange "morning" line is speakers only.

Improvement from "Morning scan, without subs" to "Afternoon scan, with subs" mitigates the dip significantly at various points, e.g. pulling up a null by 10 db at 129 hz, by 8 db at 241hz. At other points, the later scan makes some things worse, but overall, the subs were helping.

Morning scan, there's another big dip between 2khz and 10khz. Afternoon scan mitigates that by a very large amount (varying, but up to 7 db mitigation).

a good quality parametric equalizer or DSP would really be the simplest and most cost effective way to fix things in a problem room rather than a complex sub setup in a system that does not seem bass starved to start with.

I know, I know, more stuff in the signal path. So what? As long as its good stuff? Audiophiles get too anal about these things sometimes. THe end result is all that matters. With digital anything is possible. Them’s the facts!  Digital is your friend!  Stick some tubes upstream if you must.

Whatever works best.