Which is better for a DBA (Swarm); powered subs or unpowered?

While we’re awaiting a presumed response to lewinski01’s questions about 4-sub DBAs from The owner of Audio Kinesis, Duke Lejeune, I just wanted to add a quick comment:

I mostly agree with cleeds comments on his previous post. Based on the comments on this thread thus far from posters questioning the efficacy of 4-sub DBA systems, it is quite obvious that these individuals have never experienced the extremely high quality bass response performance this concept provides in practice in typical home rooms.
There is no smearing, booming or localization. If you can perceive the bass as originating from one of the subs, the system has not been setup properly or the crossover frequency control is set too high-usually above 80 Hz. What you will perceive is powerful bass down to 20 Hz, realistic and natural bass dynamics. The bass will be detailed, accurate in tone and timber and integrate seamlessly with your main speakers regardless of their brand and type.
Even though all 4 subs are run in mono, the bass will still be perceived as stereo. I can explain in detail how this is possible on a future post if anyone would like to know. Individuals have the choice of either buying a complete 4-sub DBA system kit or creating their own custom 4-sub DBA system utilizing their choice of subs. Parametric equalization, room treatments, DSP and auto room correction hardware and software are definitely not required but can be used optionally if preferred.
I’ve been using my AK Debra 4-sub DBA in my system for more than 5 years now for both stereo music and 5.1 surround for HT. I honestly can’t think of how this excellent bass system solution could be improved except with even higher quality, and much more expensive, subs being used.      From my perspective, the only other criticism of a 4-sub DBA I consider valid is that you do need to have, or make, the space for 4 subs in one’s room. I had no trouble accommodating the 4 relatively small, 12”x14.5”x28”and 40#, AK Debra subs in my 21’x14’ room but I realize others may have difficulty.      However,Duke has stated that only 1 of the 4 subs needs to be positioned on the room’s floor, the other 3 subs can be wall mounted on shelves even within a few inches of the ceiling. I know another Audiogon member, named Hans, just successfully and recently installed an AK Swarm DBA in his small office using this method.

Tim

"it is quite obvious that these individuals have never experienced the extremely high quality bass response performance this concept provides in practice in typical home rooms. noble100 Tim"

This and all the individuals personal variables of room, system, experience, and personal taste seems to have created a circumstance with the home audio hobby that lacks a general acceptance similar to what's in the pro audio tool box.  

Despite the obvious differences between home and pro audio there are some important common parameters at play.

Tim, good sticky post. 

cleeds-The price for that smooth, even, neutral bass is that your bass will be monophonic. 

noble100-Even though all 4 subs are run in mono, the bass will still be perceived as stereo.

Right. And thank you, Tim.

The issue of is the bass stereo or not is beside the point. The simple fact of the matter is DBA bass is exactly as focused and localized and 3D as anything and everything else. This from a guy who will put his system up against anyone's in the area of imaging. Any time. No problem.

Recording after recording I'm hearing bass that is never once anything less than seamlessly integrated with the sound field. Each awesome deep drum whack on Jennifer Warnes Bird on a Wire has its own unique location, reverberation and resonance. Its felt exactly as a drum that size would be, as coming from one spot then energizing the whole acoustic space.

Please note I say "acoustic space" not room. Because if I say room people will think I mean my room. Wrong. I'm talking the acoustic space where the recording was made. My system and in particular the DBA part of it effectively take my room out of the equation. My room for all intents and purposes is not there. You for all your ears are telling you are not in my room. You are in acoustic space. 

Duke explains the tech better than anyone. I can only relate what I'm hearing. What others have heard. You cannot be more wrong than to say DBA sounds like mono. It may very well be mono. But it does not in any way shape or form sound mono. So maybe that is hard to understand. Oh well. It is what it is.

I will say this though. This will be a whole lot easier for people to understand if the ones who haven't ever experienced it and therefore really have no idea what they're talking about would wait to comment until they can correct such a glaring weakness in their approach.

In my listening experience with my DBA system after adding the fifth sub it was like my room disappeared and only the music was left with at ambiance of the place it was recorded . I would call DBA active room treatment . Must be heard to understand its effect 

@cleeds wrote: "The price for that smooth, even, neutral bass is that your bass will be monophonic."

This is a misconception probably arising from the fact that the "regular" configuration for my price-conscious Swarm system only uses a single channel of amplification, and from my statements that true stereo bass is quite rare (which is controversial and has been disputed). For a few hundred dollars more, some Swarm users have added a second amplifier, though imo the most significant advantage of the second amplifier is that it gives you the option of introducing a 90 degree phase difference between the subs on the left-hand-ish side of the room and the subs on the right-hand-ish-side of the room. This can be done whether the signals going to the left and right amps are mono or stereo.

As others have noted, even if you do have mono bass, you never hear it as "mono bass". The localization cues are essentially all north of the subwoofer region, though spatial (hall size / envelopment / immersion) cues can be present in true stereo bass. The left-right 90-degree-phase-difference thing is a technique for synthesizing this sense of immersion in a large acoustic space; credit to David Griesinger for the idea, which does not depend on the recording having stereo information down in the subwoofer region. Nor in my experience does it result in a same-for-all-recordings acoustic signature; if anything, imo it unmasks more of the differences in spatial "feel" from one recording to the next.

@lewinskih01 wrote: "Would the ability to time-adjust each of the 4 subs improve sound? Like Toole described in his Sound Reproduction?"

My recollection is that Toole was referring to a Harmon subwoofer integrator processor which optimized the gain, frequency response, lowpass filter, phase, delay, and equalization based on in-room measurements. I assume it does what they claim.

Earl Geddes used to offer essentially the same services to his customers. He had them make measurements of each of their subs and then used a proprietary algorithm to calculate the settings for a Behringer processor. My understanding is that he could get in-room smoothness from three thusly equalized subs comparable to what he could get from four conventional subs. Since I’m no Earl Geddes, I still use four subs. (I have never claimed and hopefully never implied that the Swarm is "the ultimate" way to do the distributed multisub thing.)

If I had the choice between having the ability to time-adjust each sub and not, I’d choose to have it just to maximize my options... but wouldn’t want to trade off anything else that matters to get it. The arrival time differences in a normal size listening room are small enough that they are below the ear’s detection threshold at low frequencies, but it still might be beneficial.

I don’t have any experience with time alignment of subs, but do have some indirect experience with time mis-alignment:

One of my most-experienced-in-very-high-end customers has three of his Swarm subs spread around the room (with one in a front corner) and the fourth is right smack behind his listening chair (on an isolation pad). This essentially maximizes the arrival time differences, yet he finds it to be the best-sounding configuration.

So based on the information I have at this time, I would prioritize good in-room smoothness over arrival-time-alignment, but it would be interesting to try having both.

Duke