A ‘swarm’ has arrived at Audio Resurgence, well kinda. Many of you audiophiles will have heard of the ‘Swarm’ subwoofer configuration, and if not, you’ve almost certainly heard of a Distributed Bass Array (DBA). I’m not going to get too technical in describing this setup, if you want that you can just google ‘swarm distributed bass’ and there’s plenty of info floating around.

Let’s start by giving credit to a fellow who goes by the name Duke LeJune or ‘Audio Kinesis’ on various online forums; since he has brought

swarm subwoofer system

Image Credits: Audiokinesis.com

the DBA into modern times and coined the ‘Swarm’ vernacular. Inspired largely by the work of Earl Geddes, Duke LeJune has created his own ‘package’ of four subwoofers, the necessary power amplification and crossovers, and the technical knowhow of implementation. For more background into LeJune a good place to start is with this interview, conducted by Laurence Borden at Stereo Times [An Interview with Duke LeJeune of AudioKinesis]

Picking pertinent comments from the interview, LeJune describes the effect of Swarm thusly: “…scattering multiple subs asymmetrically around the room resulted in a net smoothing of the in-room bass, as each sub would interact with the room differently so that the sum would be smoother than any one along.”

Smooth bass is associated with tuneful and impactful bass, taught, fast and deep are common adjectives necessary to complete the audiophile checklist.

I’ve had more than enough experience with subs over the years. If I had to sum all of my various experiences and create a single action statement, it would be a resounding ‘don’t bother’. Subwoofers are widely used in dedicated 2-channel audio systems nowadays, compared with a decade ago when sub users were in a minority. In my opinion it’s rare to hear a well integrated subwoofer in 2-channel audio that provides more than it takes away. In most cases they’re easily detectable audibly, and that’s just another listening distraction I can do without. In many cases, subwoofers are run with the low-pass crossover set too high (by the user). This creates a more impactful mid and upper bass but generally encroaches on the lower midrange of the main speakers. When this happens, IMHO, we’re changing the character of the mains into something they were not designed to be. If you prefer your main speakers to sound differently than that intended by their designer, why did you buy them in the first place?

That’s not to say that all subwoofer implementations end up bad.

Audio Resurgence Listening Room for 2 Channel stereo

Efforts At Placing A Pair Of Subs In My Two-Channel Only Room.

In my main music room I’ve been enjoying the naturalness and sonic purity of my Dunlavy SC-III full range speakers. I understand from comments made by people with broad experience of Dunlavy Audio loudspeakers that the SC-III may occupy something close to the sweet-spot in the range of John Dunlavy designs; provided your room is of a suitable size and you’re not driven by the need to have deep bass.

Bass from the Dunlavy is different from what you’ll hear in most modern speaker designs. Being a sealed box and incorporating only two relatively modest 8″ bass drivers per box, the bass is accurate, taught, tuneful, but not deep. It’s more than satisfactory down to around 45hz in my room but then it starts to drop sharply. One can squeeze out another half octave and add more solidity to the lower frequencies by placing the speakers closer to the front wall to add more boundary reinforcement, but for me, that defeats the objective of these wonderful speakers.

When properly placed out into the room, these tall monolithic boxes just disappear from the musical soundscape. They cease to be discernible as the source of sound and sit just slightly forward of a large 3-dimensional soundstage comprised of the clearly formed images of the musicians and their instruments. Of course this is all an illusion, but they do a better job in their ability to help you suspend disbelief than most other speakers that I’ve heard. This doesn’t happen often in my experience and it certainly wasn’t a ‘plug-and-play’ scenario with the Dunlavy’s. They need careful placement, obviously. They need to be spiked through any carpet and into the floor.

Dunlavy SC-3 speakers for saleI built custom stands for my pair using two sets of Audiopoints per side, one set into the floor and another set into the speaker base, with a hardwood slab carrying the eight Audiopoints. This made an improvement over other stands and coupling devices that I’ve tried. Symmetry is also important when setting up any speaker. Not just matching the distance carefully from side walls and front walls but the position of doors, windows and furnishings in the room also impact on ‘acoustic symmetry’. In my case, room symmetry is heavily compromised due to real world constraints, but keeping the speakers well away from boundaries and using carefully placed room treatments have helped ameliorate soundstage and imaging deficiencies caused by the poor room symmetry.

What I found when attempting to introduce subs into my current system is that it was impossible, initially, to place one or two subwoofers into the room without negatively impacting the tight and focused imaging abilities of the speakers. Rightly or wrongly I concluded that the subwoofers were interfering with the phase and/or time arrival of soundwaves from the mains and causing focused images to become slightly diffuse. Well integrated subwoofers are known to improve the soundstage in the areas of depth, width, height and focus. In my system I have never been able to achieve these improvements when using one or two subwoofers. Having a crossover and speaker designed primarily for time and phase coherence has its downside when it comes to subwoofer integration.

Dunlavy SC-3 speakers for saleOf course this situation is neither black nor white, but largely gray. I could decrease the negative impact on image stability and focus by moving the subs, and generally a position alongside the mains about two inches back from their front baffle worked best. But that didn’t work optimally for producing smooth bass at the listening seat.

Moving subs around and using the phase switch at certain points produced a variety of effects on the sound, but no position worked in a way that I wanted to live with. This experience relates to using a pair of modified HSU subs, a VTF-3 and VTF-2, both ported designs and both accustomed to having their ports stuffed. Clearly it was time to try something of better quality.

 

Researching The Best Subs And The Best Configuration For Two Channel Listening.

I won’t trust equipment reviewers like myself and you shouldn’t either. There’s no point in talking with a local dealer, he’s going to push what he has and nothing else. So as I’m sure you do I generally hit the forums and look for trends in user opinion. I haven’t had much involvement with the so called Audiophile Forums for the last decade and boy have they changed. Whatever happened to forums being a home for like-minded individuals to share ideas and opinions freely in an environment of mutual respect and civility? OK, that was never the case with forums, but boy have they gotten worse over the years!

I read through a number of posts on Audiogon, and noted that generally it took between three and five posts before things started to turn sour and hostility broke out. I tried Audiocircle but that place is the polar opposite of Audiogon, it’s way too polite. And Audioasylum? Meh. I can’t tolerate the layout of their forum and most of the clear thinkers who strutted their stuff there a decade ago appear to have gone off to that great gig in the sky.

Dunlavy SC-III

I eventually put my toe in the Audiogon forum waters with a gently worded post and was immediately lambasted by someone I’d never met for my apparent stupidity. At least that’s what I took away from his quoting my comments one by one followed by his repeated interjection of the word “DUH”. But then things took a turn for the better and some useful information began to emerge. It was in this thread that I was reminded once again of the Swarm principal. I’d communicated with Mr. LeJune via email a few years back and he was very forthcoming with useful information on his Swarm theory. So I was pleasantly surprised when he made an appearance in my thread and provided a raft of excellent information. Of course there were several anti-Swarm protagonists along with advocates for DSP, EQ, room treatments and a host of other approaches to bass addendum. Consensus seemed to lean toward using some combination of DSP/EQ, with bass traps and multiple subwoofers along with a means for acoustic measurement. So armed with this newly acquired knowledge and the clock ticking down on my being able to recall any of it, I set about deciding on the manufacturer for my four new subs.

I contacted REL USA initially, gaining direct access to an inside contact via a chat initiation at their website. A long love letter ensued asking for help and recommendations from their product line….no response. After a few days of waiting I shifted my attentions to SVS with a similar strategy…..no response. A few days later I knocked firmly on REL’s front door via the form on their ‘Contact Us’ page, basically saying I want to buy four of your subs, can you help me decide what might work best in my application??!! Again, no reply. [REL Sales Support and Customer service sucks]

So I made the decision to support my local dealer again and take a drive up to Audio Exchange in Richmond, VA. I’ve bought a lot of gearfrom Audio Exchange in the last 12 months, they’ve really fueled my ‘resurgence’ from a defunct audio equipment reviewer, to the CEO and Editor in Chief of the reviewing empire that you see before you today. (add smiley face). Donny quoted me a good price for the JL Audio E110 subwoofer, and I almost pulled the trigger on a four-pack there and then, on the spot. Maybe it was Karma that intervened, I’m not sure, but something made me walk out the door empty handed. There were several things standing between me and the JL Audio E110. These included:

  • It was far smaller than I imagined was possible for an effective subwoofer, even JL Audio E110 subwhen the surface area of 4 active and 4 passive drivers was taken into consideration. How was that little box going to get my pant leg a flappin’?
  • I’d read up on the F series of JL Audio and even had an aborted purchase attempt on a pair of F112’s, but I’d read nothing about the E series and I do like to perform due diligence before every wallet-flush. The E series does have the speaker level input, which I want, but the F series does not. Other than that piece of trivia I was clueless.
  • It was 10 minutes away from the store closing and I could sense Donny was looking for a quick getaway.
  • Store owner Dave was starting to shut down operations and I doubted he’d want to help Donny fish 4 heavy boxes out of the storeroom. I tried to engage him with my witty repartee to gauge his mood but he completely blanked me. I’ve come to believe the bloke has a stick up his arse over something when it comes to moi, I can’t imagine what it could be.

So I left the store with the intent to do some research then return on Monday to collect four new subs. I never made it.

Thor Amps Pre and PowerAfter several weeks of fruitless enterprise I was presented with an opportunity to purchase not one but three Aerial Acoustics SW-12 subwoofers from the same source; used, and at a fair market price. I have a friend who had a single SW-12 in his system and the heavy bugger (subwoofer not friend) spent time in my basement listening room a few years ago. He has since acquired a second subwoofer and waxes lyrical about them daily via texts sent from his new home in Santa Fe, NM. Aerial certainly hadn’t been on my radar. Why? well, they’re big, way too big. And heavy, way too heavy. And expensive. They show up on the used marketplaces at around $2000 plus shipping costs and I wasn’t prepared to sink $10K into something that I didn’t know would work. But this was a fair deal and it was relatively local, so shipping cost wasn’t a factor. So I just hit the ‘Buy It Now’ button and entered the world of Aerial Acoustics.

A Funny Thing Happened On The Way To…..

I swear I’m victim to the strangest coincidences. My partner Lisa claims it’s all premeditated and carefully orchestrated by moi, but I swear that it isn’t.

On the way to collecting my new subwoofers from the seller in Raleigh, NC, I decided to stop at a home-theatre store on the outskirts of town to check out their wares. It’s rare that I get to Raleigh since it’s a two hour drive from my home in the Virginia countryside. When I need a big city fix I generally head to Richmond VA, which is a half-hour closer.

Anyway, it came as a complete surprise to me to find that ‘Audio Advice’ in Raleigh, NC, are bona fide dealers for Aerial Acoustics! How strange is that? I’m on my way to collect three Aerial subs and I find an Aerial dealer in the same town by complete accident!

There was no way I could fit my new pair of Aerial Acoustics 7b’s in the same car as three SW-12’s, so I paid for them and arranged to drive to Raleigh again the following day to pick them up.

Collecting the SW-12’s later in the day provided me with a well needed reality check. I need to get my personal affairs in order, get my last Will and Testament finalized to assign full ownership of my various Corporations to my partner, and to bump up my life insurance policy. Simply put, I’m a physical wreck. Helping to box then carry three subwoofers up two flights of stairs and out to the car almost killed me. I couldn’t breath. My lungs hurt. I was sweating profusely. I almost died without getting to hear a Swarm.

The following day was spent unboxing the subs then driving back to Raleigh to pick up the Aerial 7b speakers.

Aerial SW-12 Subwoofers and Aerial 7b loudspeakers arranged in a Swarm DBA

What Gives With The New Speakers, You Said You Loved Your Precious Dunlavy SC-III??

Fair questions. Somewhere in the dark recesses of my fractured mind it had made complete sense to remove my Dunlavy speakers from the equation whilst working on setting up my new Swarm. The idea had presented itself to me in a flash as I’d stood at the dealers the day before admiring the 7b’s.

And faced with the clear and obvious karmic relationship formed between me, a soon to be Aerial sub owner, and Audio Advice, a bona fide Aerial dealer, it had made complete sense to whip out a debit card and snaffle up a pair of nice Aerial speakers to go with my subs.

Had I ever heard Aerial speakers before? No. Did I get a demo before purchasing? No. Had Aerial loudspeakers been on my radar at any point in the near or distant past? No, not really. I’d lusted for a while over a set of 20T’s, reviewed by one of the big two rags if memory serves me correctly, but that was a long, long time ago.

Whatever.

FOR THOSE WHO’VE LOST THE PLOT – A QUICK SUMMARY FOLLOWS:

  • I decided, driven by a yearning for the exploration of hitherto unexplored frontiers, to throw my hat in the Swarm ring.
  • Let down by REL and SVS, and poised to invest in a quad of baby JL Audio E-subs, my radar detected a trio of Aerial SW-12 subwoofers and a deal was struck.
  • En Route to collect the subs, good karma, for which I’ve worked so hard to attract, presented me with a deal on a nice pair of Aerial 7b speakers.

And so…..

  • My first eyeball of the SW-12’s in the audio classifieds was on Friday morning, the listing was an hour old when I got onto it.
  • By 8pm the same day all three subs were in the music room and acclimating to the change in ambient conditions.
  • By 8pm the following evening my new Aerial Acoustics 7b’s were making music with me in the sweet-spot.
  • And by 10am on Sunday morning, the Swarm setup had begun.

 

Getting Ready To Swarm.

The more astute of you will have noticed that it takes four to Swarm and I only had three SW-12 subs. It’s generally considered a poor idea to mix and match subs when going down the Swarm path, but on this occasion I would have to borrow from my HSU stash to make up for the one missing leg.

Aerial SW-12 Subwoofers and Aerial 7b loudspeakers arranged in a Swarm DBAI decided to get a better handle on my new Aerial 7’s before introducing a sub or two. I’d worked on placement the previous night and part of Sunday morning, and figured that I had them dialled-in to perhaps 95% of their capability.

Their final resting position came pretty close to where I’d had the Dunlavy setup for many weeks. Rear of speaker from front wall 72″, driver centers to side-walls 38″, which had them spread around 10′ apart and the chair approximately 11 feet from the front plane of the speakers. So far so good.

 

The Sound of Aerial Acoustics’ 7b Loudspeakers

This isn’t a review of the Aerial 7b’s, I’ll deal with that later.

Suffice to say that I really like the way they present themselves, but they’re no Dunlavy SC-III. Actually, I can imagine many people preferringAerial 7b loudspeakers reviewed the sound of the Aerial 7b over the Dunlavy. The Dunlavy presentation has less meat on the bones, less weight from the lower midrange on down but with a bigger, deeper soundstage and more focused images. The Dunlavy is more 3-dimensional and also has greater clarity and detail and provides a clearer insight to the recording.

The Aerials are warmer, more forgiving of less than stellar source material and generally a pleasure to listen to for long periods without onset of listener fatigue. An argument could be made for running the Aerials without a sub, whereas that’s a tougher proposition with the leaner and less extended Dunlavy (less extended in the bass, not the HF).

So I really like the Aerial speakers a lot. They’re not really a reviewers’ tool, the Dunlavy are more open and more transparent and thus are able to provide more insight when assessing other components in the playback chain.

Half A Swarm

I started out by adding a pair of SW-12’s on the outside of each 7b, set back a few inches so as not to extend the width of the front baffle on the 7’s. I just wanted to play around and get a handle on settings and using the remote etc. I’d already established via use of the two HSU subs and the Dunlavy’s that this position wasn’t going to work, but I wanted a point of reference back to the Dunlavy/HSU setup and this was the easiest way to get it.

I ran from the preamp to the input on each sub, rather than attempt to utilize speaker level inputs, which would require making up a custom set of wires terminated with a small 5 pin DIN.

I played with the low pass XO settings and settled at 60hz (but later backed that off to 50hz when the other two subs were introduced). I had both subs up and running fairly quickly, and with volume matching made simple by their symetrical positioning and the handy remote, I was able to do some critiquing by early Sunday afternoon. I lived with this configuration until late the following day, whereupon I went ahead and introduced the second pair of subs into the equation.

Again, this isn’t my first encounter with an Aerial subwoofer so the initiation period was pretty short.

 

A Swarm

I’d come across a rough sketch showing a possible starting point for positioning 4 subwoofers in the Swarm configuration. The sketch is below:

Swarm subwoofer setup

I’m not sure to whom credit should be issued for the above sketch as it was something I found on a forum without a clear path back to its source.

Note – if your room is more stretched-out in one direction, you can see the Swarm dimensions for your room layout here.

You can see that it’s fairly straightforward to place the four subs, impeded only by the possibility of obstructions in the listening room. (doors, furniture etc). In my room it works out well enough. The one sub placed directly into the corner is over my right shoulder a few feet from my chair. I chose the HSU sub for the one corner position as theoretically it receives the most boundary reinforcement and therefore should have the least amount of work to do. I chose the VTF-3 over the VTF-2, but I need to revisit this choice soon as I’m not certain of it being the correct one.

It takes time and patience to get the volume levels set on all four subs. I’ve gone with the same 50 hz low pass filter point on all 4 subs, for now. The two SW-12’s closest to the front wall and equipment rack are the daisy-chain source for the two subs higher up the room. The SW-12’s have throughput capability with both single ended and balanced outputs for daisy-chaining a theoretically unlimited number of subs, and it worked fine with the HSU being the endpoint off one of the Aerial subs.

A quick and dirty procedure for setting volume on 4 subs in a smaller, almost square room is to set them up one at a time with the other three muted. So with 4,3,2 muted, get 1 working so you can just hear its contribution to the bass foundation of the mains, from your listening chair, then mute it and go to sub #2, and so on. Once I had all four subs set this way there was clearly too much bass, so I dropped all of the gain settings by one point on each sub then listened again. I repeated this until as a combined ‘system’ it appeared to be at a satisfactory level. This isn’t a scientific or even a reliable way of setting the sub’s volume as each is sat within a different room mode with potentially different amplitudes, so the way to do it properly is with a mic and suitable measurement software. As I do not presently have access to such equipment, my ‘handballed’ method will have to suffice for now.

Audio Resurgence Listening Room for 2 Channel stereo

With volume set it’s time to take stock of where things are at. In my case I can offer up the following initial observations, note that these are not conclusions, far from it:

  • The sound with Swarm ‘engaged’ is less appealing than without.
  • Using the Aerial 7 speakers with Swarm, I could NOT detect the same phase anomalies affecting image definition as I’d found with the Dunlavy/HSU setup. Clearly this tells us nothing until I put the Dunlavy’s back into the system, assuming the Aerials are transitory.
  • The sound at this point is far from ideal. There’s a little ‘muddiness’ in the lower bass that needs to be resolved and generally the notes appear a little too thick, voices a little too chesty. The bass with four subs running isn’t tight and well defined, as I’d expected it to be.
  • Using synthesized bass tracks there’s a notable presence of more extended bass.
  • Using acoustic bass tracks the extension is there but the definition and timbral quality of notes is quite poor.
  • Using a familiar acoustic bass track that has previously spotlighted a serious dip somewhere around the 70-100hz range, the dip is gone, or at least I was no longer able to detect missing notes.

During initial volume setting it was interesting to note the sound of the system with one subwoofer running at a time, from each of the four different locations. The best overall sound in terms of listenability and bass tonality was with three subs muted and the sub directly over my left shoulder operating. To be clear, one sub sounds better at this early stage of adjustment than two, three or four subs, and the one preferred sub is the one to my left side at the rear end of the room.

The above observations are with the four subs’ phase toggles set to 0 degrees, or ‘Normal’. Later on, trying different combinations/permutations of the phase toggles (0/180) yielded changes but not any real improvements.

Aerial SW-12 Sub installation and Swarm Distributed Bass Array

[Image shows SW-12 to rear left of room and unused HSU VTF-2 under table]

 

Here’s a room layout. Ratio is a little screwed up but it’s close enough.

room layout with acoustic treatments

 

What Next?

The collective wisdom passed down via the many forum posts I’ve read over the past weeks would have me believe that the next stage is to HSU VTF-3 Right Rear cornerfine-tune the sub locations by ear, or preferably using measurement software, for improved performance. Easier said than done. The SW-12’s are heavy and a pig to move. Also, they’re so large that they occupy space with limited room for movement without repositioning furniture, media racks etc. The process of fine-tuning this ‘system’ is quite daunting. Where does one start? which sub isn’t contributing in the way that it should? If you think about it, this is a reasonable concern. The subs interact with each other and it’s only the product of all subs working together that we can judge. So switch one off and making adjustments to any of the remaining three subs is pointless. So we with four subs running and all of them interacting, where’s a good starting point for making adjustments?

In my situation, the easiest place is with the corner sub which happens to be the HSU VTF-3. I’ve tried adjusting phase and volume, plugging/unplugging the two ports, now I can start to pull it out a little from its corner placement, I suppose.

New Allnic L5000 DHT preamp

[Some may notice that the Thor Preamp was replaced by a new Allnic L5000 DHT – preamp arrived on Monday]

And then what? The SW-12 in the left part of the room off the front wall has no place else to go as it’s tight between the equipment rack and my bass traps. In fact it’s too close to the equipment rack for my liking but in a room 16′ wide, the golden ratio sketch above would have it in no other place.

Aerial SW-12 Sub installation and Swarm Distributed Bass Array

[Front Left Sub]

The sub on the front right is up against one of my vinyl media racks and I can’t move that up the room without affecting the HSU which sits in the opposite corner on the other end of the rack. There’s room for maybe two inches of adjustment in any direction but no more. The sub over my left shoulder has more options, but in its present location it works great, so long as the other three are switched off!

SW-12 Subwoofer

[front right subwoofer]

So I think the only way to make forward progress from this point is to go out and purchase measurement software/hardware and start to map things out more scientifically.

Conclusion? Not Yet.

Obviously this is a work in progress, and a slow laborious one at that. We’re all used to shoving around our main speakers trying to find their optimal position. But for that task we are essentially treating the pair as one ‘locked’ unit. If we move one speaker an inch from the front wall then we need to move the other speaker the same distance before we sit down to evaluate the change. Not so with the Swarm, they’re all coupled together acoustically via the room and movement of one subwoofer can and should change the entire interaction.

Maybe I’m making things sound more complicated than they are. So let me put it in simple terms: at this point, the Swarm setup does not work satisfactorily in my room.

The last changes to the Swarm were made on Wednesday 5th February 2020, day four of their introduction to my room. I will continue to log any progress and any other notes in this post.

I’d welcome any comments or input. Have at it below.