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Help me understand "the swarm" in the broader audiophile world

I'm still fairly new out here and am curious about this Swarm thing. I've never owned a subwoofer but I find reading about them--placement, room treatments, nodes, the crawl, etc--fascinating. I'm interested in the concept of the Swarm and the DEBRA systems, and I have a very specific question. The few times I've been in high-end, audiophile stores and asked about the concept of the Swarm, I've tended to get some eye-rolling. They're selling single or paired subwoofers that individually often cost more and sometimes much more than a quartet of inexpensive, modest subs. The same thing can be said for many speaker companies that make both speakers and subs; it's not like I see Vandersteen embracing the use of four Sub 3's. 

My question is this: do in fact high-end stores embrace the concept of multiple, inexpensive subs? If not, cynicism aside, why not? Or why doesn't Vandersteen or JL or REL and so on design their own swarm? For those out here who love multiple subs, is it a niche thing? Is it a certain kind of sound that is appealing to certain ears? The true believers proselytize with such zeal that I find it intriguing and even convincing, and yet it's obviously a minority of listeners who do it, even those who have dedicated listening rooms. (I'm talking about the concept of four+ subs, mixed and matched, etc. I know plenty of folks who embrace two subs. And I may be wrong about all my assumptions here--really.)

Now, one favor, respectfully: I understand the concept and don't need to be convinced of why it's great. That's all over literally every post on this forum that mentions the word "sub." I'm really interested in why, as far as I can tell, stores and speaker companies (and maybe most audiophile review sites?) mostly don't go for it--and why, for that matter, many audiophiles don't either (putting aside the obvious reason of room limits). Other than room limitations, why would anyone buy a single JL or REL or Vandy sub when you could spend less and get ... the swarm? 


northman

Showing 6 responses by mijostyn

mijostyn's avatar
mijostyn
8,570 posts
 
It is very hard to overkill subwoofers. The larger the driver the lower the distortion all other parameters being equal. Certainly with more subwoofers you can get away with smaller drivers but still. The larger drivers require larger enclosures which may be a cosmetic problem. As Ralph implied the best place to put subwoofers is in a corner or against a wall for a number of reasons. The problem becomes timing them so that they are in phase with the satellites and the wavefront from the subs and satellites reaches you at the same time. This is not so easy. In trying to match satellites without a high pass filter ridiculously low cross out points are being used. It is easier to integrate a subwoofer with higher crossover points 100 to 125 Hz. It is much easier to hear when the drivers are in phase. This requires at least two subs and a 2 way crossover. I have not used random placement around the room so I really can not comment on that type of setup. My 4 subs are arranged symmetrically around the satellites. I use digital bass management and can change crossover points and delay on the run so I can hear the differences immediately which is a big help with setup. There are several units available now that do this. The result is that you can not tell there are subs in the system until a real low note comes along and I am matching subs to dipole ESLs
As several people have mentioned on this forum, rolling off the satellites lowers distortion in them and increases head room by as much as 10 dB. 
mijostyn's avatar
mijostyn
8,570 posts
 
Right. If we are talking about a 2 channel high fidelity system one sub never works well for a multitude of reasons. When you get to two subs crawling around on all fours is an evolutionary step backwards and totally unnecessary. Sub placement has to consider the placement of the satellites. Whether or not you add more subs in addition and where you place them depends on what type of satellites you have, point source or line source, size of drivers, how high you intend on crossing over and how loud you want to go. Subs should always be against a wall or in corners. There is a large increase in efficiency which lowers distortion and the amount of power needed to drive the sub. It also decreases unfavorable room interactions. 

By far the most difficult problem is matching the subs to the satellites. If set up correctly you should not be able to tell there is a sub in the system.
There are three issues that have to be dealt with to get the job done right. The crossover point and slopes, the phase and time relationship between the subs and the satellites and the relative volume of the subs to the satellites. Subwoofers have a bad reputation in many quarters because getting all this right is not easy and I have not seen a single powered subwoofer that comes with the onboard flexibility to do this well. It becomes a trial and error ordeal. Passive subwoofers with outboard amplifiers and digital crossover systems have the power to do this very effectively in less than a human life span. Now I just pissed off everyone with a powered sub  🥺 Not to worry! You can use the amplifier in the subwoofer you just have to add an outboard crossover with the necessary flexibility. You have to get one anyway as very few subs come with a high pass section for the satellites and you will absolutely never get the best performance without one. 

mijostyn's avatar
mijostyn
8,570 posts
 
Rix, the stiffest enclosure would be a sphere. But that is difficult to produce. Next is a cylinder or tube as you suggest. This is a much easier design to deal with and perfect for a balanced force system. Just put a driver in both ends. I'm building 4 of them with 12" Morel drivers. Two in each cabinet.

For point source systems crossed over below 80 Hz it really does not matter where you place the subs as long as they are spread out always against a wall or in a corner.

For line source systems crossed over above 100 Hz you have to consider the affects on image and the increased power projection a line source has. The best way to do this is by creating  subwoofer line source along the front wall. It is still a "swarm" system of sorts just with a more specific radiation pattern. 
mijostyn's avatar
mijostyn
8,570 posts
 
Rix, I would forget about open baffle subwoofers. Hold on to your opposed driver balanced force design. Work on creating a very stiff, heavy enclosure design of the right size to support the two drivers. What is the stiffest enclosure shape you could use? If you have more or less advanced woodworking capabilities give me a shout and we can discuss it:)
mijostyn's avatar
mijostyn
8,570 posts
 
Proving the superiority of a multi subwoofer setup is easy. All you have to do is impulse test the system at three set positions in the room using one then four sub woofers. What you will see with one sub is wide changes in volume between 0 and 100 Hz  up to 10 dB or so between the positions. With all four subwoofers these variations will reduce to less than 3 dB. Even with room control you will have trouble. Trying to correct a 10 dB deficit will cost you 8 times the power and force the woofer into the non linear part of it's excursion creating distortion. Correcting a 3 dB deficit requires just twice the power and a much smaller increase in woofer excursion. Put all this together and the ultimate subwoofer system requires 4 large subwoofers with at least 2000 watts of power each and room control.
mijostyn's avatar
mijostyn
8,570 posts
 
Subwoofers are a hard sell to begin with never mind four. WAF, cost, wiring, etc. Hi Fi people have a bad impression of subwoofer because most setups are not great. The theater people don't care, They just want to feel their seat shaking.

 bdp24, dipole subwoofers are a bad joke. You are right that sound travels at about 1 foot/msec. If you place the subwoofer a certain distance from a wall the reflected sound will only be exactly in phase at one frequency. Everywhere else will be out of phase creating even more interference patterns. It is just a cheap easy way to make a defective subwoofer.

For point source systems the swarm concept is ideal as long as the crossover point is below 100 Hz preferably 80 Hz. The swarm limits room interaction giving you the same volume throughout the room. With a single subwoofer the volume can change 10 db in only 3 feet! Here great bass, there nothing.

For linear arrays or line sources the situation changes and depends on the type of driver used. In order to radiate power the way a line source does you have to create a subwoofer linear array which involves placing subwoofers at intervals across a wall into corners. ESLs do better with higher cross over points 120-125 Hz. This stops the diaphragm from taking long excursions and limits distortion. For other Line sources a lower crossover between 80 and 100 Hz will do fine.

In all cases digital bass management is handily the best way to integrate a subwoofer system.   

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