[Voiceray]

What does it mean when said it flattens all room modes?  Looks like it heightens all of them.

[Duke]

Briefly, the idea with the Swarm is to distribute the four little subs asymmetrically, as this way each one will excite the room's modes differently.  The sum of these multiple dissimilar responses is smoother than any one of them would have been alone.  This principle can be applied with other subs - in fact, doing so with a quartet of GR Research servo subs would be killer.

[Voiceray]

I'm probably way off base, but I though we were doing that with the four drivers already being used.

[Duke]

I'm probably way off base, but I though we were doing that with the four drivers already being used.

I'm sorry but I don't understand your question.  Which four drivers are you talking about?

Open baffle subs have smoother room-interaction than monopole subs, and many subs have smoother room-interaction than just one or two subs, so since I'm doing monopoles I use many (four). 

[Brucemck]

I'm probably way off base, but I though we were doing that with the four drivers already being used.

The two drivers per side are essentially "in the same place" on each side, so you've really got "two subs" working.  Typically you end up having response problems as a function of length, width, and height.  In a typical stereo setup the left and right are symmetrical with respect to the length (the same distance from the rear wall), and width (the same distance from the side walls), and height (both located the same distance from the floor.)  If you take the tangential nodes you have the same symmetry.  Thus, your left and right subs create more or less exactly the same problems at the listening location, and don't really complement each other all that much.

To get multiple subs to "cancel out" their problem frequencies requires that they be asymmetrical.  In my case I have one at the front of the room and a second midway along a side wall, and the peaks/dips tend to be pretty complementary.

Duke's solution is to place four at different enough locations

[Voiceray]

The two drivers per side are essentially "in the same place" on each side, so you've really got "two subs" working.  Typically you end up having response problems as a function of length, width, and height.  In a typical stereo setup the left and right are symmetrical with respect to the length (the same distance from the rear wall), and width (the same distance from the side walls), and height (both located the same distance from the floor.)  If you take the tangential nodes you have the same symmetry.  Thus, your left and right subs create more or less exactly the same problems at the listening location, and don't really complement each other all that much.

To get multiple subs to "cancel out" their problem frequencies requires that they be asymmetrical.  In my case I have one at the front of the room and a second midway along a side wall, and the peaks/dips tend to be pretty complementary.

Duke's solution is to place four at different enough locations

All I saw was the graph of the Swarm.  It's not fair to make a comment on something you haven't listen to.  All I know is both want to cancel room effects.  If Duke's is as successful as Danny's, then how they do it shouldn't matter.  I do like that Danny's Sub being able to crossover up to 300 Hz.

[Brucemck]

It's not fair to make a comment on something you haven't listen to.  All I know is both want to cancel room effects.

I've heard both approaches, multiple times in multiple venues.  Even so, it's basic physics: yes Danny's (terrific value and performance) subs load the room a bit differently than Duke's swarms (or any other basic box sub), but the physics of being "in a place" still applies.  Similarly, the physics of multiple subs spread across multiple locations has been well documented (Harmon's site has some good white papers and modeling of the physics in theory and in practice.)

Personally, I'm headed towards a hybrid solution: stereo left and right subs up front adjacent to the main left and right speakers, with additional sidewall left and right subs to cancel/complement each of those (one on the left wall wired in the same chain as the left front sub, and a second on the right wall for the front right sub), with a fifth mono fill sub somewhere in the room to "balance" all of the foregoing. 

[Turk]

Quite right.  Link to Harmon modeling for multiple subs to smooth in room response.

http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/Scientific%20Publications/13680.pdf

[Duke]

All I saw was the graph of the Swarm. 

If you don't mind my asking, where did you see a graph of the Swarm?  I don't think I've ever posted one.

Thanks,

Duke

[Danny Richie]

I do like that Danny's Sub being able to crossover up to 300 Hz.

Of coarse playing up that high makes them no longer just subs. It is then covering the mid-bass and lower vocal harmonics as well. I like to keep them at or under the 200Hz range just to keep from splitting a critical vocal range up into several different drivers.

Playing subs up to that range also requires that they be next to or part of the main speakers as distance from them gets real critical regarding integration.

As for what approach to use can come down to room size as much as anything.

I wouldn't want to play the subs in a swarm configuration up real high either. Keep in mind that as frequency increases the directionality also increases. If the main speakers can play down into the 40 ro 45hz range pretty solidly then integrating them to a sub gets much easier. 

I LOVE the open baffle servo subs. They do EVERYTHING well. But they also have to be placed well out into the room. I have my Super-V's a good 5 feet or more out into the room. Some rooms just won't allow that, and the Swarm is a good alternative.

What does it mean when said it flattens all room modes?  Looks like it heightens all of them.

Think of it as dropping four golf balls in the water about 16 feet apart verses all of them in one spot. All spread out evens out the waves and some even cancel each other out. All in one spot makes one big wave. Now imagine putting a box around all of them.

Plus you can run the back subs out of phase from the front subs and really even out the way they load the room. By moving them around a little you can actually get them to cancel out each others output to some degree in areas where you might have a peak in the room.

Another thing to keep in mind is that if you can use multiple subs verses a single monster, the amount of movement needed to create the same SPL levels are much less for a group verses a single. So what you get is much less moving mass (typically) and MUCH less stored energy. The subs return to rest more quickly.

Plus those long exertions can cause flexing of the cone and a real increase in distortion. So the multiples REALLY have an advantage. Now throw the additional control of a servo system on top of that and you'll hear resolutions levels in low frequency ranges that you didn't realize ware there.

[jtwrace]

I LOVE the open baffle servo subs. They do EVERYTHING well. But they also have to be placed well out into the room. I have my Super-V's a good 5 feet or more out into the room. Some rooms just won't allow that, and the Swarm is a good alternative.

Why wouldn't you say that the standard Rythmik servo subs in a sealed box are also a good alternative?  I have them and really like them.  Just curious.

Think of it as dropping four golf balls in the water about 16 feet apart verses all of them in one spot.

Do you play golf?  Seriously.

[drphoto]

I dunno if this will add anything or not. I believe in both the OB/servo and the multiple sub approach. In fact I'm running it now. I've got a dual pair of the OBs (still in the flat baffle test mules, as I've not had time to build the H-frames) along w/ a Mirage BPS-150i in a corner playing at a low level. I've got clean, tight, fast bass. I can clearly hear bass guitar lines against the bass drum. On Genesis records w/ the dual drums, I can hear each drum kit. At some point, I may add a cheap sealed sub, like the Dayton for the lowest notes, but I'll have to see what happens when I get the H-frame baffles completed.

I think both of these approaches go a long way to solving room issues. I don't have any bass trapping, only 6 GIK 242 panels to control slap echo in my very lively room. The quality of the bass I get is more than satisfactory.

[Danny Richie]

Why wouldn't you say that the standard Rythmik servo subs in a sealed box are also a good alternative?  I have them and really like them.  Just curious.

I guess because the discussion was more centered around ways to not load the room but still get great bass response. Clearly from a sound quality perspective they are the pinnacle. Plus, Duke already mentioned the use of four of them in the Swarm configuration, and that would be really killer.

At some point, I may add a cheap sealed sub, like the Dayton for the lowest notes

Funny thing though is those Dayton woofers in a sealed box won't play down very low, and your servo subs will play flat to 20Hz.

[jtwrace]

I guess because the discussion was more centered around ways to not load the room but still get great bass response. Clearly from a sound quality perspective they are the pinnacle. Plus, Duke already mentioned the use of four of them in the Swarm configuration, and that would be really killer.

No doubt that it would be awesome.  I must point out though that with two properly setup it's pretty bad-ass I must say.  I'm a firm beliver that no matter what you pick, room acoustics is key.  Bass traps. Bass Traps....

Again, two from a financial standpoint and space standpoint properly done is VERY good.  I just think it's important for others that may read this thread not to think that four is an absolute.  That's all!   

[Danny Richie]

Again, two from a financial standpoint and space standpoint properly done is VERY good.  I just think it's important for others that may read this thread not to think that four is an absolute.  That's all!   

That's true. My pair of N2X's and a single servo sub with the levels matched is a scary good combo. I am sure that many other speakers will match with them well too.

[dBe]

I dunno if this will add anything or not. I believe in both the OB/servo and the multiple sub approach. In fact I'm running it now. I've got a dual pair of the OBs (still in the flat baffle test mules, as I've not had time to build the H-frames) along w/ a Mirage BPS-150i in a corner playing at a low level. I've got clean, tight, fast bass. I can clearly hear bass guitar lines against the bass drum. On Genesis records w/ the dual drums, I can hear each drum kit. At some point, I may add a cheap sealed sub, like the Dayton for the lowest notes, but I'll have to see what happens when I get the H-frame baffles completed.

I think both of these approaches go a long way to solving room issues. I don't have any bass trapping, only 6 GIK 242 panels to control slap echo in my very lively room. The quality of the bass I get is more than satisfactory.

Here are some great toys for the audiophool in all of us.  Great visualization of what happens in closed spaces.  It is geeky so of course I like it.   

http://www.falstad.com/mathphysics.html

Dave

[Voiceray]

If you don't mind my asking, where did you see a graph of the Swarm?  I don't think I've ever posted one.

Thanks,

Duke

I've been looking through my searches, since your post.  I haven't found it yet.  My guess is it was not from your area, but from a user being home grown.  I did find comments stating that placement of the subs was a tweaker's paradise, probably referring to so many great choices. 

[JoshK]

No doubt that it would be awesome.  I must point out though that with two properly setup it's pretty bad-ass I must say.  I'm a firm beliver that no matter what you pick, room acoustics is key.  Bass traps. Bass Traps....

In principal, that is what I love about the multi-sub approach.  It lessens the burden on bass traps, because it doesn't excite any one mode as much instead exciting most all of them to a lesser degree.  Still bass traps will help with the decay. 

[Voiceray]

Here is URL that help me understand more about the two different principles through our discussion.

http://www.diyaudio.com/forums/multi-way/145876-measured-monopole-dipole-room-responses.html