Which subwoofer?

A coupla decades back Gradient made dedicated OB subs for both the QUAD ESL (aka "57") and the 63. They did that for a reason: QUAD owners had long been searching for a sub that would "mate with" their dipole ESL’s, to no avail. Non-dipole subs simply do not "mate with" dipole loudspeakers. Why? That information is readily accessible in the literature, including in the writing of Siegfried Linkwitz. I won’t repeat it here; those with the requisite intellectual curiosity will find it on their own. Beside, I have previously done so, and that info has been ignored for reasons at which I can only guess.

The statement "the mate with thing is a non-issue" simply reveals the ignorance (the term used in a non-pejorative spirit) of the person who uttered it in regard to the very real technical problems encountered when attempting to mate a dipole loudspeaker with a non-dipole subwoofer. It is HE who should be ignored. ;-)

The OB/Dipole Sub currently available from the collaborative team of Rythmik’s Brian Ding and GR Research’s Danny Richie is a FAR better product than that of Gradient. Again, the reason that is so may also be learned with very little effort. I’ll give you a hint: The Rythmik Audio/GR Research OB/Dipole Sub is the only sub of it’s kind in the entire history of hi-fi music reproduction, an OB/Dipole sub incorporating servo-feedback woofers. Now THERE’S a mating!

The OB Sub is the first and only sub using dynamic woofers I have found which rivals the bass panels of the Magneplanar Tympani T-IV’a (which I also own) in bass quality. It was those panels Harry Pearson mated with the m/t panel of the Infinity IRS to create his "super" speaker. The IRS includes massive woofer enclosures containing multiple servo-feedback dynamic woofers, yet Harry preferred the bass panels of the Tympani T-IV. I formerly owned the mini-IRS---the RS-1b, which also includes separate enclosures with s-f woofers. The OB/Dipole Sub easily bests the RS-1b woofers.

 lewinskih01:
" @noble101
Indeed,Earl Geddes has said that subs has been enough for him, but 4 is better. It's important to note when Geddes talks about "better" bass he's referring to seat-to-seat variations across the room. So bass is more Even across the room. He isn't talking taut, 3D-like, fast or other descriptors often used for "good" bass."

Hello lewinskih01,

     I'm not certain you're claim about Geddes's meaning, when he talks about "better" bass, is correct.  Yes, one of the main benefits of his 4-sub distributed bass array (DBA) concept is very even bass distribution performance throughout the entire room with very little seat-to-seat variations across the room.  
     But another main benefit of his 4-sub DBA concept is that this very evenly distributed bass performance is also consistently perceived as very high quality bass as described by the familiar good bass audio adjectives such as taut, fast, smooth and detailed. 

     Duke LeJeune, the owner of Audio Kinesis, is still a friend and was an associate of Earl Geddes, circa 2014-15, when he told Duke about the benefits of utilizing the 4-sub Distributed Bass Array(DBA) concept he invented/discovered and gave Duke permission to use the concept as he wished and without charge. 
     Subsequently and fairly quickly, Duke introduced the AK Swarm 4-sub DBA that was reviewed very positively in 2015 by the Absolute Sound magazine.  Here's a link to that review: 

https://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system
   
     This is just a sample from this review praising the high quality of the Swarm's 4-sub DBA system's bass performance: " Now any addition of full-range bass gives some of this effect. But the Swarm gives more of it. Not more bass than other subs—lots of them can be turned up to give plenty. Rather, there is better bass with less signature from the listening room."
     My main point is that both of these main benefits of the 4-sub DBA concept, evenly distributed bass and high quality bass, are not subtle qualities at all.  These are both very obvious qualities that were easily perceived by both the Absolute Sound reviewer and myself as a user. 
      I seriously doubt that either Earl Geddess, as the concept's inventor/discoverer as part of his PHD thesis, or Duke LeJeune, as the concept's adopter/manufacturer, are unaware of these two main benefits nor hesitant to refer to both of these as qualifying as "better" bass qualities when discussing the concept.
     After utilizing the AK Debra 4-sub DBA system for the past decade and counting, I can also state with certainty that bass power, impact and dynamics are also other main characteristics of this concept.

fwiw,
Tim

Closing this loop in case someone in the future is interested in OB subs. I exchanged with several folks, some very knowledgeable in OB.

Danny Richie used sealed boxes in the back of the rooms at some audio shows to prevent large seat-to-seat variations for the audience. He doesn't use these himself. He recommends his OB, period. And if one wants to complement up to 30Hz with sealed he's good and in fact has recommended doing so in some cases. Danny does recommend 4 feet from the front wall, which is too much for my case (maybe I could get to 3 feet...)

I learned that when using OB subs it's very important to take your room dimensions into consideration, especially your front-to-back distance between walls (since dipoles radiate little to the side walls and ceiling/floor). To properly get to 20Hz you need that dimension to be 12 meters. My largest room dimension is 10 meters, close enough, but alas, my speakers are firing along the 5 meter axis (width) and for practical reasons I can't turn them around. 

So I'll drop the idea of adding OB subs and add another couple sealed servo subs. And a MiniDSP 2x4 to apply multi-sub optimizer to allow delaying any of them as needed and other DSP for individual subs. Then the overall DSP will treat the DBA/MiniDSP as a "unit".

As to what drove Geddes to set up distributed bass arrays, I'll pass and let people do their reading. Geddes was proposing his approach well before 2014 and his papers and videos talk about minimizing seat-to-seat variations. Surely more subs provide more, pressurize the room more, etc, but that was his main driver. He also doesn't (or didn't at the time of the videos) believe time-alignment between subs and mains mattered, yet others do.
Toole gets into it too in several places. His chapter 13 in Sound Reproduction gets particularly into distributed bass arrays with time delays among subs for optimal results. This does require measurement equipment, a learning curve, and spending significant time to achieve the results. In my view Audio Kinesis are a great solution that simplifies the approach yet retains most gains for those who aren't interested in going that far in adjusting time and other variables. A great solution indeed!
Not interested in getting into a debate about this, though. There are plenty of materials online and Earl participates in some fora for those really interested. I realize there will be one/multiple replies to this, but really not interested to debate and won't engage. 
Cheers and happy listening