Distributed Bass Array configuration

I have two twin-18” subs; run in stereo. 

MAPMAN -
It definitely does not get better because there is more. These guys you see on YouTube ( some considered influencers ) with multiple subs primarily in their theater systems are going for more bass and sound pressure. I guess if you just want to impress people by making their bowels move and shock the crap out of them ( pun 👍 ) go ahead and get your kicks that way.
You’re not getting more  bass if you have set things correctly. You can get more if you don't mind it being out of balance with the upper end but that’s not the way I listen to music or movies for that matter.
What has happened for me ( doesn’t mean it’s going to be exactly the same for anyone else in their room/configuration ) is that with two subs there was better blending ( horizontally ) without the perceived location issue derived from one sub. But, then the bass ( especially kick drums ) were overly emphasized and got just so centered that it was almost the only spot many of the lower frequencies were being placed. Unfortunately I have to set my front subs to the inside of my mains ( no choice ) so that influences the issue.
But when I added a third sub, wow!! Game changer and now I’m elated. The low frequencies are completely balanced in every way with the rest of the music ( frequencies ). There is absolutely no sensation that there are subwoofers ( external speakers from the mains ) and the bass is just part of the music ( heavenly ). The bass is still centered ( that’s the way it was mixed by the engineer ) but it spreads further horizontally and very naturally ( as I would perceive natural ). It fills the listening area ( I’m not saying there is bass all over the room ), making  it smooth with no overemphasis anywhere. I feel the subharmonics without it feeling like they are ”hitting” me ( even with movies ). Not that it’s due to multiple subs but I’m relaying that you don’t get that type of issue because you have added multiple subs. I think there can be that perception from the hype of the bass centric crowd.
What amazes me is that the third sub is less than six feet ( behind me ) from my listening position and I don’t “feel” it even at higher volumes, it blends sonically invisible.
None of this would be possible to achieve setting up by ear ( well maybe with a couple of years of trial and error ). It’s only been possible with the implementation of the MiniDSP HD 2x4 and REW.  The full use of REW with its eq section ( room correction with parametric eq that is similar to Dirac ). Beyond that the MiniDSP offers delay options so after the REW eq you can make tone sweeps and see which delays ( or lack thereof ) on each sub is most beneficial ( or not ). This is the best $315 I’ve ever spent!! Sometimes technology truly is your friend.
Now there is quite a learning curve and definitely trial and error but it is more than worth it!! Some may consider themselves to already have achieved this but I’m confident that if you implemented the MiniDSP you would achieve even further benefits and results.

Thanks for that explanation.  Minidsp is the way I would  go for that as well. 

mapman: " What measurements establish the “improved bass”?  Improved in what way?

Just  wondering.  Is it just more? More  extended?  Flatter response ?  Different frequency curve?    What exactly is different than prior?"

Hello mapman,

     I agree with soundspectacular, that the bass in a room or system does not qualify as improved just because it's louder or there's more of it.  I consider more bass an improvement in an audio system only if it manifests itself in the capacity to accurately reproduce large and natural bass dynamics contained on the source material, whether the source material is music or LFE channel information for HT. 
     My goal for my combo system has always been improved bass quality, which I define as bass that is accurate and natural in tone, pitch and intensity as well as powerful, detailed and textured without any exaggeration.  
     I believe a flatter in-room bass response curve and deeper bass frequency extension capacity definitely represent improved system bass performance.  However, I've never utilized any in-room bass frequency response measurement equipment, tools or room correction hardware/software.  I do believe such gear and tools are generally very convenient and helpful once competent skill at their usage has been attained.
    Since I bought and installed my AK Debra 4-sub DBA system about a decade ago, my criteria for evaluating and gauging its effectiveness in my room and system has been purely done by ear and subjectively.  I'd be interested in measuring its in-room bass performance but, unfortunately, I currently lack the gear and skills to do so
    But I'm not very concerned about attaining the gear and skills for accurate room measurement since I know without any doubt, based on how it subjectively sounds and feels, that it represents the best bass system I've yet to experience in my room and system.  I honestly believe my system, formerly with the AK Debra 4-sub DBA and 2.7 mains and currently with 3.7i mains,  has performed so well that I consider it a somewhat miniature version of Magnepan's $30K, 30.7 4-Panel Dipolar Planar Loudspeaker System, click the link attached below for a description and review:

http://www.hifiplus.com/articles/magnepan-307-four-panel-dipolar-planar-loudspeaker-system-revisited...

     About 3-4 years ago or perhaps more, I attended an in-person, Wendell Davis led demonstration of the 30.7 system at Ovation Audio in Indianapolis.  Of course, the 30.7 was very impressive being auditioned in about a 30'x20' room with 8' ceilings and being driven by a single, very large ss Anthem amp (I forgot the model).  The overall system was very impressive.  Natural and powerful sounding with full range and powerful dynamics, very much like how acoustic music played live and unattenuated, sounds and feels when experienced live and in-person.
     But the most surprising and disappointing impression I heard and felt from the 30.7 demo came from its two very large, 6.5'h x 2.5'w each, what they call bass/ mid bass panels.  To be clear, the bass and mid-bass reproduced by these very large dipole speaker panels sounded and felt very powerful, dynamic, natural and seamlessly integrated with the system's two equally large midrange and treble panels.  But I could clearly notice that the 4 modestly sized, 2'hx1'wx1'd, subs of my AK Debra DBA system inconspicuously positioned around my 23'x16' living room,  roughly equaled the 30.7 system's performance in sounding and feeling powerful, dynamic, natural and seamlessly integrated with my system's two more moderately sized, 6'hx2'w, 3-way and full range 2.7 dipole panels, had a bit deeper and more realistic bass extension. This is proven accurate by the difference in the rated bass extension between the two systems: 20 Hz  rated bass extension for the AK Debra system vs 24 Hz rated bass extension for the Magnepan 30.7 system.  
     Not a huge difference but it was obvious to me the AK Debra DBA system. overall, outperformed the 30.7.  After the demo during a Q&A session, I described this difference I perceived and asked Wendell if he ever considered just paying a royalty fee per unit sold to Audio Kinesis for adopting their much less obtrusive, and more effective, bass array concept using 4 small subs instead of the two very large and dipole bass/mid-bass panels. 
     Too blunt and pointed a question? Perhaps, but he's a big boy so no big deal, right?  He responded with a confused look. a hesitant look around the 20 person audience and a rather quick point for the next question.  I like and respect Wendell but everyone could tell he was awkwardly avoiding the question.  I still wonder why?

Tim

Interesting. I have no doubt more subs set up well is better.  I have 1 Klipsch  sw308 I set up manually with kef ls50 metas using  a sound meter app and white noise to initially set things up to extend the bass to be roughly in  line with all the rest then fine tuned including phase by ear.   Simple and effective. Would never have arrived at the right settings by ear alone.  The bass is just right.