“The Swarm” by Audio Kinesis

[ahofer]

http://www.audiokinesis.com/the-swarm-subwoofer-system-1.html

I’ve seen a few intra-thread mentions of this, but any longer-form reactions to this product?
Does it offer any advantages/disadvantage over four separate subs? Can you go with smaller drive units? (E.g. Rhythmik).

 

[tuga]

Perhaps the @Duke could elaborate on its merits.

 

[Duke]

By way of background, the Swarm is an example of what might be called a "distributed multisub system", and is based on an early version of Earl Geddes' ideas on the subject, used with his permission. It consists of four 10" passive subs, driven by one (or optionally two) shelf-mounted amplifiers.

For those unfamiliar with the basic concept, it goes something like this: A subwoofer will inevitably have a nasty room-induced peak-and-dip pattern. You can move the sub or move the listening position and the pattern will change, but it will not go away. When you distribute four small subs asymmetrically around the room, each produces a significantly different peak-and-dip pattern at any listening location in the room. The sum of these four dissimilar peak-and-dip patterns is considerably smoother than any one would be, and that improved smoothness holds up throughout the room. And "smooth bass" = "fast bass", for reasons which I can explain.

Todd Welti's work on the subject of multiple subwoofers for Harman is better known on this forum. Todd examined symmetrical placement strategies, while Earl focused on asymmetrical strategies. By coincidence they were both developing their ideas at exactly the same time, but unknown to one another.

Does it offer any advantages/disadvantage over four separate subs?

No big ones.

The individual subwoofer units are "voiced" with the expectation that they will all be used together, so how they sum is taken into account. Typical "room gain" from boundary reinforcement is also taken into account. As a result, they usually don't need much if anything in the way of EQ.

The four passive subs of the Swarm are normally driven by one amplifier, and optionally by two. Each amplifier includes a single band of parametric EQ, so the EQ capability is limited. If you wanted to equalize each sub individually, you'd be much better off with four separate powered subs.

Can you go with smaller drive units? (E.g. Rhythmik).

Yes. The basic concept can be implemented many different ways. I don't really do custom sizes of my product, but you can assemble your own distributed multi-sub system using whatever subs make sense for you. They need not all be the same size; you can combine one or two big subs with smaller ones. The one caution I would offer is this: You want to roll off the top end of any subs positioned away from the mains with a fairly steep slope, and no higher than 80 Hz. You don't want these subs betraying their locations by passing audible upper bass/lower midrange energy.

I have a very high opinion of Rhythmik subs.

I’ve seen a few intra-thread mentions of this, but any longer-form reactions to this product?

Over on Audiogon there are several threads on the Swarm in particular, and/or on distributed multisub systems, or "Distributed Bass Arrays". You will also find mention of the DEBRA system, a version of the Swarm concept that I designed for James Romeyn, which is essentially the same thing but with a rectangular footprint instead of a square one. Some of the posts there are by people who have been using a distributed multisub system for more than five years. Google "audiogon swarm" and several threads should pop up. Just for the record, there are some rather absolutist statements made which I do not subscribe to. The concept has detractors as well as fans, so I encourage you to read what the detractors have to say.

Robert E. Greene of The Absolute Sound reviewed the Swarm in 2015, and his review is online. I get the impression that reviewers are looked down upon around here, so let me tell you a little bit about Robert: He turned down an offer to be head of the Mathematics department at Tulane University and chose a position at UCLA instead, so that he could work with more people who were at the top in the field. Last I heard he was working on the ninteen-dimensional mathematics which would be the theoretical foundation of whatever comes after String Theory. He is a concert violinist and instructor, and taught Russel Crowe to play the violin for his role in "Master and Commander" (that's actually Russel playing in those scenes). He also runs a Doberman Pinscer rescue.

 

[stevenswall]

Anyone know what room size "The Swarm" is targeted at when they quote their 113dB at 20hz spec?

 

[Duke]

Anyone know what room size "The Swarm" is targeted at when they quote their 113dB at 20hz spec?

Can you let me know where you saw that? It's not on my webpage. I don't remember how I calculated it, but it was a probably a while back and I probably didn't use a good method (out of ignorance at the time).

It LOOKS to me like I calculated the summed two-meter output for the four subs, assuming boundary reinforcement. That may have been an overly optimistic yardstick.

I don't have time to re-calculate it right now but will do so when I have a bit more time to do some homework on the subject.

 

[stevenswall]

Can you let me know where you saw that? It's not on my webpage.

I was reading about it from a site in Utah that licensed the Swarm system in slightly different boxes:

"Conservatively rated by designer Duke LeJeune for 113 dB clean output @ 20 Hz"

https://jamesromeyn.com/audiokinesis-speaker-models/debra/

He is quoting it from elsewhere though, so I'm not sure as to the original source.

Mostly curious because I already have Genelec 8260 monitors with 10" woofers and I'm not sure four small subs would add significantly to it. Now I'm thinking about seeing what the 4 cheapest 12" non paper Rythmik subs are that can be daisy chained. Just going to be a pain with four extension cords plus XLR in and XLR out.

 

[CDMC]

Mostly curious because I already have Genelec 8260 monitors with 10" woofers and I'm not sure four small subs would add significantly to it. Now I'm thinking about seeing what the 4 cheapest 12" non paper Rythmik subs are that can be daisy chained. Just going to be a pain with four extension cords plus XLR in and XLR out.

They will. With bass, there is no substitute for displacement. Your Genelecs offer solid bass down to about 30hz at reasonable levels, probably 95db or so at 30hz before getting significant distortion or limiting. This is plenty for most music. The question is do you want that last octave, watch movies, listen to organ music, large orchestral movements, or synthesized music, outboard subs will get you the extension and clean output that your mains cannot. Your idea of 4 12" Rythmiks will get you great low bass output.

There are additional benefits aside from the extension and output capability. You will get smoother bass response with the distributed array (which sounds tighter) than your current speakers, you will also get lower distortion from your mains, assuming you high pass them.

 

[stevenswall]

They will. With bass, there is no substitute for displacement. Your Genelecs offer solid bass down to about 30hz at reasonable levels, probably 95db or so at 30hz before getting significant distortion or limiting.

If I high pass them, then it's like I only added two 10" subwoofers, because the Genelecs won't be making low bass anymore, which is why I'm skeptical.

I think the GLM software runs around 85dB, and the 8260 goes flat to 18hz in room. Maybe I'll have to test how loud it goes, and see if REW can measure distortion.

 

[richard12511]

They will. With bass, there is no substitute for displacement. Your Genelecs offer solid bass down to about 30hz at reasonable levels, probably 95db or so at 30hz before getting significant distortion or limiting. This is plenty for most music. The question is do you want that last octave, watch movies, listen to organ music, large orchestral movements, or synthesized music, outboard subs will get you the extension and clean output that your mains cannot. Your idea of 4 12" Rythmiks will get you great low bass output.

There are additional benefits aside from the extension and output capability. You will get smoother bass response with the distributed array (which sounds tighter) than your current speakers, you will also get lower distortion from your mains, assuming you high pass them.

Not just those types of music, but also a good percentage of modern pop has content digging down to the mid 20s and below. Phoebe Bridger's "Punisher"(for a recent example I listened to) has a sweep down to 8Hz in the last minute or so of the song. Those Genelecs have great bass, but they're not what I would consider truly full range. Very few speakers are, and usually they weigh several hundred pounds.

Also, I completely agree with your last paragraph(re: it's not just about output and extension). Adding 4 subs, especially if they're well placed and integrated, should dramatically improve the sound quality of the bass.

 

[mac]

I recall REG promoting the idea that the ideal listening environment for stereo speakers would be outdoors. I haven't taken his opinion when it comes to hifi seriously since.

 

[tuga]

I recall REG promoting the idea that the ideal listening environment for stereo speakers would be outdoors. I haven't taken his opinion when it comes to hifi seriously since.

I recall him writing that early reflection zones should be treated but that a dead room would be a bad idea.

 

[mac]

Perhaps his thinking has changed over time. Ten years ago he literally wrote what I stated.

 

[stevenswall]

Adding 4 subs, especially if they're well placed and integrated, should dramatically improve the sound quality of the bass.

Sure, but the issue here is that quantity is also desirable, and effectively adding two, 10" subs seems unlikely to do much in that department.

Also, using GLM, there are no bass quality issues when I sit in the sweet spot. There is simply flat bass, and a dip at 100hz that a subwoofer crossed over at 80hz isn't going to take care of.

I wish Devialet made a set of four subwoofers. I'll bet an 8" dual opposed one from them would compete with 15" sealed subs.

Anyhow, maybe someone will be able to find measurements or the SPL levels of The Swarm in different room sizes.

 

[Duke]

I was reading about it from a site in Utah that licensed the Swarm system in slightly different boxes:

"Conservatively rated by designer Duke LeJeune for 113 dB clean output @ 20 Hz"

https://jamesromeyn.com/audiokinesis-speaker-models/debra/

Thank you for the additional information.

I have a vague recollection of my partner Jim Romeyn calling me up a few years ago and asking for a max output number, and I ran my modelling program and apparently came up with 113 dB. My recollection is that figure was the calculated in-room “one meter equivalent”. This was long before I had heard of the Data-Bass site and their protocols. For the record, I've messaged Data-Bass at least twice to inquire about possibly having the Swarm measured, and have not heard back from them.

Mostly curious because I already have Genelec 8260 monitors with 10" woofers and I'm not sure four small subs would add significantly to it.

I think the Swarm would "keep up with" your Genelecs on music in most situations.

I looked up the Genelecs and their spec sheet says “113 dB max output” at one meter, from 100 Hz to 3 kHz.

Since the Swarm has four units, let's look at how two of them compare with a single Genelec: Factoring in typical room gain and making an adjustment for estimated compression, two Swarm units combining in semi-random phase would average about 112 dB at one meter from 80 Hz to 20 Hz, and would be about 110 dB at 20 Hz. So we are close.

Now I'm thinking about seeing what the 4 cheapest 12" non paper Rythmik subs are that can be daisy chained. Just going to be a pain with four extension cords plus XLR in and XLR out.

I have a very high opinion of Rythmik subs. I can't imagine you being disappointed with four Rythmiks.

If I high pass them, then it's like I only added two 10" subwoofers, because the Genelecs won't be making low bass anymore, which is why I'm skeptical.

The advantage of a distributed multisub system is qualitative, not quantitative, and imo arises largely from having multiple bass sources in acoustically dissimilar locations. Assuming your Genelecs are positioned symmetrically in your room, they are in acoustically similar locations and will not be as smooth in the bass region as two asymmetrically-located bass sources, which in turn would not be as smooth as four asymmetrically-located bass sources.

Let me explain why this smoothing effect matters: The ear is ESPECIALLY sensitive to differences in SPL in the bass region. This is demonstrated by equal-loudness curves, which bunch up south of 100 Hz, such that a 5 dB change in SPL at 40 Hz or so SOUNDS LIKE as much of a difference as a 10 dB change at 1 kHz!!

The summation of the multiple dissimilar in-room frequency response curves results in MORE peaks and dips, which are SMALLER and CLOSER TOGETHER. This latter aspect is of psychoacoustic significance: The ear/brain system tends to "average" bass region peaks and dips which fall within 1/3 octave of one another. So the audible improvement is likely to be greater than one might guess from eyeballing the before-and-after curves, and this improvement extends throughout the room; it is not confined to a "sweet spot", which tends to be the case when EQ alone is used. (No reason why you can't do both... and maybe even add a few bass traps for good measure.)

Also, your Genelecs may be happier at high SPLs if they aren't being asked to contribute in the bass region. Their spec sheet shows your Genelecs to be flat to about 27 Hz. I calculate they probably require 6-8 dB of bass boost at 27 Hz to accomplish that. So IF they are being asked to handle the low bass region THEN that "113 dB @ 1 meter" max SPL spec cannot be met all the way down to 27 Hz, and indeed they only claim it north of 100 Hz. So you stand to gain a considerable amount of useable headroom by not asking your Genelecs to do the bottom couple of octaves.

If you do decide to go with a distributed multisub system, I suggest covering as much of the region below 80 Hz as possible with the subs, because they will do a better job in that region than your Genelecs can. I also suggest rapidly rolling off the top end of any subs which are not near your Genelecs, so that they do not pass upper bass/lower midrange energy loud enough to betray their presence.

 

[richard12511]

Also, using GLM, there are no bass quality issues when I sit in the sweet spot. There is simply flat bass, and a dip at 100hz that a subwoofer crossed over at 80hz isn't going to take care of.

Why not cross at 100hz then? Or even 120Hz? With steep slopes, I don't see any issues with a higher crossover. That’s what I do. With 4 subs, you won’t have localization problems, and the high crossover will solve your 100Hz null problem. Solving that problem should give you a great sound quality boost, as 100Hz is a very critical region. On the localization issue, someone can correct me if I'm wrong(going by memory), but the 80Hz standard was chosen simply because it was more than one full octave below the lowest note than any person was able to localize in their test. Further, that was just one person. Nobody else in the group of people they tested was able to localize anything below ~210Hz. Using 4 well distributed subs will make localization even harder than it was in that test. I've tested all the way up to 150Hz crossover in all 3 of my 4 sub systems and I can't localize any of the subs.

Another great benefit of adding subs is that it will make your mains sound even better than they already do, since they no longer have to concern themselves with producing the most difficult part of the spectrum. The 8260 is already arguably in the running for best sounding speaker for home use. My personal opinion, of course, but I'd put it in the same class as 8351b, D&D, and Kii. I've never heard the 8361a, but the measurements seemed to have regressed a bit from it's predecessor(I'm somewhat holding out for the 8361b before making my next purchase decision ).

Don’t take this last part as a slight(I'm just trying to help you get even better sound ), as I’m sure your system sounds amazing(better than mine, outside of the bass). But, my educated guess is that you “just think” you’re hearing amazing bass because you’ve never heard a system with 4 well placed and integrated subs. Most likely what you're hearing is good, but not great bass. I’ve never heard a 2.0 channel system that has what *I* would consider to be great bass, and I've heard 2.0 channel systems with 2 JTR 215RTs(100dB @13Hz anechoic). Compared to the 8260, those systems had much deeper extension(10Hz in room), more output, less distortion, and were running with Dirac(better and more advanced than GLM) and minidsp. In the past, I know you've mentioned that you like to listen to your system in multiple positions(hence why you only consider coaxial speakers). It's all but impossible to get even bass across multiple listening positions with just 2 speakers sitting up front. Four subs can not only give you more even bass, but it will no longer be confined to just the "sweet spot".

The best bass I've ever heard was at a GTG with a guy that had 8 18" DIY subs .

 

[sfdoddsy]

I posted a question about this in a seperate thread, but may as well jump in here.

I can't find the exact source, but I recall over the years either Geddes or his acolytes recommended not using bass management but instead running the mains full range so they act as additional bass sources. Obviously the more capable your mains the better.

Since the point of a multi-sub approach is not to increase output (although that is often a by-product), or to increase depth, but rather to smooth response in the mid-bass area this would seem to make sense.

My mains are flat to below 30Hz, and I don't listen loud enough to stress them.

Normally I cross them at 80Hz to my Rythmik sub, but I am experimenting with running them with no high pass, and the sub with no low pass.

The results so far are at best inconclusive. And complicated by that fact that in my standard setup I EQ the sub and the mains below the Schroeder frequency using Anthem's very good ARC.

 

[Willem]

Thanks Duke for your considered and benevolent advice. One does not often hear manufacturers praise the products of competitors. I am still in the process of considering a second sub, given budget and location constraints, but your arguments are compelling. I have one question, however. I know additional subs produce a smoother response, and will also increase spl somewhat, but will they also improve extension?

 

[Duke]

There is simply flat bass, and a dip at 100hz that a subwoofer crossed over at 80hz isn't going to take care of.

You can run the two subs up near the front of the room higher than 80 Hz if needed to integrate well with your mains. With the Swarm, this would be done by using two amps instead of the normal single amp (and you'd optionally have a bit more headroom, assuming the impedances of the woofers installed in the subs were chosen with two subs per amp in mind, rather than the normal four per amp). With individually powered subs, it's just a matter of setting the lowpass filter frequencies on each sub.

I can't find the exact source, but I recall over the years either Geddes or his acolytes recommended not using bass management but instead running the mains full range so they act as additional bass sources. Obviously the more capable your mains the better.

That idea originated with Earl, whose mains are low-Q sealed boxes using B&C prosound woofers so they can very easily handle the thermal and mechanical demands in a home audio or home theater setting. Imo it depends on the mains of course - do what works best for YOUR situation. When designing mains where subwoofers are planned for, I try to avoid "needing" a protective highpass filter for the mains to minimize what's in the primary signal path.

Thanks Duke for your considered and benevolent advice. One does not often hear manufacturers praise the products of competitors.

I'd like to think it's still a big enough pond that the fishermen can get along. And I really have been impressed by the Rythmiks.

I know additional subs produce a smoother response, and will also increase spl somewhat, but will they also improve extension?

There are two ways I can think of that additional subs can improve the extension.

One is, if the additional subs go deeper to begin with... the subs need not all be the same. Earl Geddes has one ubersub in a corner which goes deeper than all the others. It's a bandpass sub of his own design, with a cluster of long ports which exit the box and extend upwards to a height of maybe six or seven feet above the floor, such that sub's output originates from a location which is closer to the ceiling than to the floor. This way he has his bass sources distributed in the vertical plane as well as in the horizontal one, which contributes to the in-room smoothness.

The other way additional subs can extend the bottom end, or at least make it louder, is this: The distributed bass sources will tend to combine in semi-random phase near the top end of the bass region, transitioning to approximately in-phase at the bottom end of the bass region, which tilts the low-end up somewhat compared to the trend with a single sub. As we go lower in frequency and the wavelengths become long relative to the room's dimensions, we transition out of the "modal region" and into the "pressure zone". This is not true for all rooms of course - some are too big or are much open into the rest of the house. In fact this effect can increase the very low end energy enough that something has to be done about it. With the Swarm, one solution is to reverse the polarity of one of the subs (typically the one farthest from the mains), which has the added benefit of further smoothing the in-room response. Some Swarm users have two subwoofer amps, in which case we can manipulate the phase controls to address this situation and make often make additional improvements.

Note that the effect described above is also the reason why one or two deep-extension ubersubs can (in some rooms) combine well with multiple "lesser" subs. Across the upper bass region where we have multiple sources combining in semi-random phase, so the summation includes partial cancellation as well as partial reinforcement. Then down below the modal region (in the "pressure zone") where we have just the single bass source, the wavelengths are long enough relative to the room's dimension that we don't have the cancellation dips associated with room modes.

If your room is rectangular, you can use an online room mode calculator. So if the online calculator says your lowest mode is 35 Hz, you might want your multiple smaller subs to extend down to that region, and then have your ubersub(s) extend below it.

 

[richard12511]

For the record, I've messaged Data-Bass at least twice to inquire about possibly having the Swarm measured, and have not heard back from them.

Do you happen to know if they're still in business? The site is still up, and the forums are still active(someone's paying for that..), but it seems like it's been awhile since they measured anything. If they are, then that's a real bummer. I was kinda planning on sending them a Genelec 7050, and then depending on how it performed, maybe replacing the 4 JBL subs in my office.

 

[Beershaun]

maybe replacing the 4 JBL subs in my office.