Distributed Bass Array configuration

Hey Millercarbon, just copy that and paste that from now on.  Most straightforward, no bs explanation I’ve heard to date.

And for the record, I still hate subwoofers as much as I love them

REW measurements definitely show a difference. I guess it's up to each person if it matters or not.
Here's some example of in-phase vs out-phase graphs. Scroll down in the link to view all 5 screen captures.

First graph is comparing dual subs in and out of phase.

Next 2 down include the phase graph for dual subs in and out of phase.

Last 2 dual subs for the Group Delay for in and out of phase.

https://imgur.com/a/RSQiBMi

From REW author.

The vertical lines for the phase graphs are called Wrapped Phase:

" Phase is cyclic, due to the periodicity of the sine function. When it is increasing and reaches 180 degrees it wraps around to -180 and continues with -179, -178 etc. When it is decreasing and reaches -180 degrees it wraps around to 180. The vertical lines show those wrap points. If you look in the graph controls you will see a button to "unwrap" the phase, which allows it to go to 181, 182 etc rather than wrapping, but you can end up with extremely large value ranges in unwrapped phase, partly because any time delays create a frequency-dependent phase shift that gets ever larger as frequency increases.

All that changes at the wrap points is the way the graph is drawn. Think of it more like reading the second hand of a clock, after 59 secs it starts again at 0 and counts up again, but time has not jumped or done anything other than progress as usual. The part of phase that gets plotted when wrapping is used is like showing only the seconds of a time."

Group Delay
" The Group Delay at a frequency is the slope of the phase at that frequency. It provides an indication of how the envelope of signals at that frequency is delayed in the course of passing through the audio chain - if everything is delayed by the same amount the shape of the signal is not changed, it simply arrives later, but delays that vary change the shape of the signal.

Anything that affects the phase will also affect the group delay, which includes crossovers, the response of drivers, the low and high frequency roll-offs of the various parts of the audio chain, any time delays in the system and the filtering effect of the room, its modal response and the frequency-dependent absorptions of its surfaces and furnishings".

OP, I have this inquiry happening now, too. Here is a very informative discussion that moves past some top level opinions, one way or the other. 

https://youtu.be/1X_n6kG9FOc

"We take a look at stereo vs mono bass in a multi-sub 2CH and home theater environment. Does Stereo bass have merit and is it worth going through the potential complications of configuring your system to accommodate stereo bass? Watch our Youtube discussion to find out."

Thanks b_limo it is very clear, yet evidently still not clear enough on one point: there is no such thing as stereo subs! Because, there is no such thing as stereo bass, at least not below 80.

This will be like, I don’t know how many times clarifying I am losing count. And apologies in advance for shouting. But when everything is done right it SOUNDS AS IF the bass is stereo, BUT IT IS NOT!

If I have one weakness it is not bothering to keep track and being able to reference every tiny little thing. So times like this I forget where it comes from. But some big engineer paid a lot of money did an in-depth study of a wide range of recordings and found none of them had stereo bass, and anyone interested can look it up.

Another good one to look up is my mega DBA review. Mine uses two Dayton amps partly because at the time I wasn’t sure and thought two might be better. Just in case. Once I had them though some of the first things I did was to try running my new DBA in all possible configurations. I went through the gamut. 4, 8, 16 ohms. One amp mono. One amp stereo. Two amps mono. Two amps stereo. Played with phase. Tried all the time waster put the sub in a chair while you crawl around on the floor. About the only thing I did not try is the even worse stuff that requires a microphone. When the day comes a mic is better than my ears, take me out and put a bullet in the head, I’m already dead.

BUT, and this is a very big important BUT, it sounds as if it is. Why? The answer can only be that information above the low bass is somehow integrated into one seamless whole. This happens in the brain. Not in the ears, but between them. For proof look no further than the Supertweeter thread where everyone who tries them says two things: 1. they can’t hear them- too high frequency- and 2. they improve the bass. So how does ultrasonic 60kHz improve bass way down below 60Hz? You tell me. But it does.