Budget subwoofer 'swarm'?

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neekomax

Budget subwoofer 'swarm'?
« on: 14 Jan 2018, 08:56 pm »
If this belongs in a different circle, break out the forklift and move it where it goes, of course. (Didn't there used to be a bass circle, btw?)

I use three subs in my modest system, along with a DSPeaker Dual Core unit, to try and get smooth bass in my room, per Toole, Geddes, LeJeune etc. I'm always tweaking crossovers, placements, gain levels, DSP on, DSP off, etc. etc. forever and ever. At least I'm not spending cash endlessly, although the endless fussing is kind of the same thing, only cheaper.  :lol:

I wonder if there is a way of re-creating the sub swarm concept for cheap. http://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/. Like unloading all my present subs and the DSpeaker, and building passive subs, or buying good-enough off the shelf subs, and then using a Behringher DCX2496 or Mini DSP or something to control all the subs as a system. Right I'm just sort of guessing at levels and placement, and the Dual Core is more optimized in general for a .1 or dual mono system.

How could it be configured? How inexpensive could it be and still improve on the standard single or dual (or no) sub setup in a music system?

Letitroll98

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Re: Budget subwoofer 'swarm'?
« Reply #1 on: 14 Jan 2018, 10:30 pm »
You have three subs now, the swarm uses four I believe, why not just buy one more sub?  (The last specs for Duke's swarm I saw were for four subs)

The bass circle was melded into Enclosures some time ago.


Early B.

Re: Budget subwoofer 'swarm'?
« Reply #2 on: 14 Jan 2018, 11:41 pm »
Seems like you've already re-created the swarm concept for cheap by using three subs instead of four.

Are all three of your subs identical?

I also use three subs (2 are identical) and it sounds fantastic. I attempted a 4th sub that I borrowed from my second system and it didn't work out very well. I believe it was due to the differences in sound quality of the subs. That 4th sub is low-fi and it could only contribute some muddy bass.

Of course, I'm no expert on swarms, but I would imagine that you should start with a single high quality sub and build from there by adding three more identical subs as your budget permits. I'm sure it's more complicated than that, but the point is to start with good quality. IMO, the majority of commercially available subs suck at being subs. You gotta spend around $700 for a decent sub, and if you look at it that way, then the Audiokinesis swarm system is a bargain.   

TomS

Re: Budget subwoofer 'swarm'?
« Reply #3 on: 15 Jan 2018, 12:28 am »
Duke's a really smart fellow and his Swarm is a bit more than dropping 4 subs with a mono amp into a room. It was carefully designed to perform the way it does, using a room's gain. That said, there are certainly ways to take advantage of multiple subs as many here have done successfully.

FWIW, I have 3 DIY raw MDF Geddes subs and a DCX2496 just sitting in storage that would be a bargain for someone if not for shipping  8)

When multiple subs are set up properly, you really shouldn't be able to "hear" them. The upper bass/lower midrange will free up and there will be more subtle foundation to the music. If you're hearing stuff in the 50-200hz range it's likely the unevenness of room modes, which multi-subs can help mitigate. The first sub is usually furthest away and plays at the highest level, so you want to get that one optimized on its own first. The other 2-4 are usually closer to the listener's position and are set much lower in level. I could barely hear mine with my ear close to them, but turn one off and you'd definitely know it.

I mixed in Rythmik/GR subs, both sealed and OB in at times, as well as a couple ACI Titans, and it didn't really didn't change matters much. The 3 Geddes bandpass subs worked very well by themselves. I've heard another AC member's setup with 3 sealed Rythmiks/DCX2496 several times and it was also very good. Mixing different subs just makes it more complex and harder to learn the effects of their individual placement, settings, tuning, etc. I could see where it could actually make it sound worse. Even with 3 identical very high quality ones, it did take MANY hours with REQ Wizard to the point of exhaustion to get it right. Very much worth it though.

If I were to do anything differently I might add a VERY different sub, like one ULF monster only to do the deepest bass, which is something Dr. Geddes mentioned a few times.

neekomax

Re: Budget subwoofer 'swarm'?
« Reply #4 on: 15 Jan 2018, 01:09 am »
Interesting, lots to respond to.

But I'm just curious. What exactly is the design of the Geddes sub? A cursory googling yielded little.

TomS

Re: Budget subwoofer 'swarm'?
« Reply #5 on: 15 Jan 2018, 01:24 am »
Interesting, lots to respond to.

But I'm just curious. What exactly is the design of the Geddes sub? A cursory googling yielded little.
That's because it's proprietary ;-)

It is a unique bandpass design where the driver is inside the cabinet with either multiple small ports or, in my case, a large passive radiator on the outside. The driver is a B&C 12TBX100 which is incredibly robust.

neekomax

Re: Budget subwoofer 'swarm'?
« Reply #6 on: 15 Jan 2018, 01:33 am »
That's because it's proprietary ;-)

It is a unique bandpass design where the driver is inside the cabinet with either multiple small ports or, in my case, a large passive radiator on the outside. The driver is a B&C 12TBX100 which is incredibly robust.

Hmmm. I guess I don't understand how a bandpass sub works. Is this the driver you mean? With a vented F3 of 83 Hz? https://www.parts-express.com/bc-12tbx100-12-high-power-woofer-8-ohm--294-569

That doesn't seem like a proper sub woofer. What am I missing?  :scratch:

poseidonsvoice

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Re: Budget subwoofer 'swarm'?
« Reply #7 on: 15 Jan 2018, 01:56 am »
Hmmm. I guess I don't understand how a bandpass sub works. Is this the driver you mean? With a vented F3 of 83 Hz? https://www.parts-express.com/bc-12tbx100-12-high-power-woofer-8-ohm--294-569

That doesn't seem like a proper sub woofer. What am I missing?  :scratch:

Nico (my brother-in-law's French and that's what we call him as well),

You can't use cookie cutter formulas and the Parts Express suggestion is only a suggestion (It's actually a suggestion for vented enclosure, not bandpass design). Probably a small port that is tuned high. Hence the F3 is high. The 12TBX100 is an exceptional driver but it really shines in the mid bass.

A 4th order bandpass subwoofer design basically has its own acoustic filter built into the design. The Geddes version is an application of that, and it rolls off at 24dB/octave (4th order) over 100 Hz. It rolls off about 12dB/octave below 50 Hz or so. The overall useable bandwidth is around 45Hz to 150 Hz in room (At least I know that to be a fact in my system as I have measured it numerous times.). The advantage here is the astonishingly high efficiency. It's about 95dB/watt/meter over that useable bandwidth. That's a very, very, big deal. Dynamics and detail galore, all with a 60watt/channel amplifier, and very little thermal compression to speak of especially at higher spls  :wink:.

Years ago, I built a pair of Geddes' bandpass passive radiator design and still use them today. I should've built three but I built only two. Multiples of them (like any sub) will help in minimizing the peaks and valleys we all see in small rooms' low frequency response as you already know. Then add a big honkin' ULF subwoofer for the area below 50Hz and voila, you have nirvana.

Here is a pic of my subs. The outer driver (shown) is the passive radiator. The inner driver (not visible) is the B&C 12TBX100:



My third sub is a Funk Audio 21.0LX which has a 4th order crossover set at 55Hz.

My response is +/- 3dB without any smoothing from 15Hz to 400Hz overall. I use a Behringer DCX 2496 as well. Interestingly enough, due to proper placement of my Geddes subs, I have NO EQ on them at all. And no electronic crossover point as well. They just blend right into the mains in the high end, and blend right into the Funk sub on the low end. My only EQ is on the Funk sub which can easily handle it and is needed in the lowest modal area (1st mode) around 20-30Hz.

As if that wasn't enough, I'm currently building a dual opposed sealed design as my 4th sub consisting of a pair of B&C 15BG100's  :thumb:.

My best piece of advice is to get used to measuring with REW before you embark/invest in multiple subs. And if you are going in that direction, why not invest in a Minidsp or DCX2496 first (get them used), and use your existing subs and optimize them as well as you can while mastering your measurement skills with REW if that is an issue. Like Tom said, even with multiple subs (of very high quality), I spent several long nights, before getting to where I am today.

Best,
Anand.
« Last Edit: 15 Jan 2018, 03:32 am by poseidonsvoice »

TomS

Re: Budget subwoofer 'swarm'?
« Reply #8 on: 15 Jan 2018, 01:57 am »
Bandpass means it has a natural acoustic cutoff on both the low end and high end. It makes for a smoother response in the portion between those 2 points (the pass band), and exhibits very low distortion. In this design/application it is very much a proper driver as part of a great performing bass system.

artur9

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Re: Budget subwoofer 'swarm'?
« Reply #9 on: 15 Jan 2018, 02:51 am »
Interesting, lots to respond to.

But I'm just curious. What exactly is the design of the Geddes sub? A cursory googling yielded little.

I came across this summary and links to Geddes papers recently.  It's a nice explanation.
http://seriousaudioblog.blogspot.com/2012/05/two-great-articles-on-multiple.html

artur9

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Re: Budget subwoofer 'swarm'?
« Reply #10 on: 15 Jan 2018, 03:14 am »
I have a swarm of subwoofers as well.  AIUI, no need for identical subs if you follow Geddes, which works well in my situation.

But it is a LOT of measuring with REW and finding proper relative levels, phase, and high and low cutoff frequencies.  I think it was something like 2 years of fiddling on weekends to get things to measure well and sound great.  I don't think one has heard good bass until one has heard multiple subwoofers properly configured with minimum EQ.  With this set up I can never really hear an individual sub.

The link I posted above explains why there's so much fiddling.  There is a program called MSO that can help but I don't think it uses Geddes method.

One example of something I had to tweak.  With my 4 subs, when I folded in the 3rd one it "conflicted" with my main LFE sub and caused poor frequency response.  Was a hell of a thing.  Finally, I set the hi/lo frequencies of the 3rd subwoofer (I think, effectively, turning it into a bandpass sub?), and boom! flat response from 40-100Hz.  That took 3-4 hours all by itself.

Here's the before and after, no smoothing.  The green trace is with a high pass filter @ 50Hz on my third sub.  The gold trace is what the response was before I did the high pass.  The peak @ approx. 30Hz is my main room mode.  I later used PEQ to bring that down.


@poseidonsvoice I love that subwoofer you made.  How big is it?   Can you make me a couple? ;-)

poseidonsvoice

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Re: Budget subwoofer 'swarm'?
« Reply #11 on: 15 Jan 2018, 03:38 am »
Very nice example artur9.

If you think the Tsunamis (my Geddes BP PR) look nice then you should hear them! They sound way nicer than they look! They are about a 17 inch cube as the front facing driver (the passive radiator) is 15 inches in diameter.  I am hoping the Tsunami 2 (the dual opposed sealed design) will compare well to them. We’ll see soon enough I hope.

Nico, I apologize, much of what I posted isn’t cheap nor cheerful unless it counts cause it is diy.

Best,
Anand.

TomS

Re: Budget subwoofer 'swarm'?
« Reply #12 on: 15 Jan 2018, 03:56 am »
Oops I totally missed the cheap and cheerful part, sorry guys  :oops:

Russell Dawkins

Re: Budget subwoofer 'swarm'?
« Reply #13 on: 15 Jan 2018, 09:56 am »
I've been reading glowing reports on this Dayton Audio driver for subs. Does anyone have experience with it? 18" with an Fs of 18 Hz and an efficiency of 93 dB, $245-$260.
https://www.parts-express.com/dayton-audio-rss460ho-4-18-reference-ho-subwoofer-4-ohm--295-472

poseidonsvoice

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Re: Budget subwoofer 'swarm'?
« Reply #14 on: 15 Jan 2018, 10:25 am »
I've been reading glowing reports on this Dayton Audio driver for subs. Does anyone have experience with it? 18" with an Fs of 18 Hz and an efficiency of 93 dB, $245-$260.
https://www.parts-express.com/dayton-audio-rss460ho-4-18-reference-ho-subwoofer-4-ohm--295-472

It’s a very good driver for the money along with it’s sister, the UM 18-22. They differ in that the UM18 has a bit deeper extension at the expense of a small difference in efficiency (see the measurements below, not just what Dayton advertises as a “spec.”)

The best place to read about these drivers is Josh Ricci’s Data-Bass site (my personal reference). He runs them through brutal testing (which they ALL should go through).

Here are the links. First read the system overview, then go to the next page called measurements.

RSS460HO: http://data-bass.com/data?page=system&id=89

UM18-22: http://data-bass.com/data?page=system&id=116

For what it’s worth Josh measures some of the finest drivers and sub systems in the world and that includes some of the popular Rythmik models.

Regarding multi-bass, I have my own opinions on the strategies that work, pm me if you want to discuss.

Best,
Anand.

JLM

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Re: Budget subwoofer 'swarm'?
« Reply #15 on: 15 Jan 2018, 11:46 am »
Was intending on getting a swarm, based on Gedde, LeJeune, and Toole readings but got sidetracked.  A friend needed to sell a nice DIY sub that uses a 10 inch XBR driver from CSS.  With my DSPeaker Anti-Mode 2.0 Dual Core it makes a very nice addition to my near-field system, to the point that spending more to possibly muck up the sound doesn't interest me.

Auditioned the sub at my friends before buying it and it was much more powerful at his place (his 'great' room being perhaps 50% larger than my Cardas Golden Cuboid listening room.  Note that the DSPeaker is probably filtering down the sub to get it to blend with my mains.  So wonder if you're losing sub output for the same reason.

So why are you unsatisfied?  As I understand the theory a swarm attempts to provide uniform bass response across the room, is that your goal?  The more subs the better to achieve uniformity, but three should provide a good start.  Seems like you may simply be lost in confusion.

Your up against the laws of physics, with bass there is no (cheap) shortcuts.  I asked recently on AC for suggestions of an inexpensive/quality sub with low F3 for my seldom used AV system and fortunately a nearby ACer sold his oldie but goodie ARS500 that more than fills the bill.  So adding another sub of decent quality, good output, and fairly low F3 would no doubt be well beyond C&C guidelines unless you too can stumble across a used deal.

Seems to me your issue is one of defining your wants and learning how to set up the swarm.

brother love

Re: Budget subwoofer 'swarm'?
« Reply #16 on: 15 Jan 2018, 11:50 am »
neekomax,

You might need to assign a preliminary budget price range to your swarm plans in order to get better recommendations. Based on your question: "How inexpensive could it be and still improve on the standard single or dual (or no) sub setup in a music system?":

I tried a true "cheap & cheerful (3) multi-sub arrangement" at one time. Results are here: http://www.audiocircle.com/index.php?topic=136983.0

The bucket sub is a good cheap & cheerful option that I strongly considered, but never tried:
http://thehornshoppeforum.com/index.php?topic=406.0

AC's Poultrygeist built a pair of bucket subs: http://www.audiocircle.com/index.php?topic=138469.msg1474191#msg1474191

Early B.

Re: Budget subwoofer 'swarm'?
« Reply #17 on: 15 Jan 2018, 02:47 pm »
Your up against the laws of physics, with bass there is no (cheap) shortcuts. 

Yep. Forget about doing it cheaply. You can't use multiple cheap & cheerful subs in order to get superior bass sound.

neekomax

Re: Budget subwoofer 'swarm'?
« Reply #18 on: 15 Jan 2018, 03:15 pm »
Great responses everyone. I have to rush off to work now, but hopefully I'll get some time to re-read everything and give it all some consideration.

What's great is the thread from 2015 by Brother Love is exactly the kind of thing I was bringing up, only I was thinking that more attention might be paid to signal processing as a group, with a DCX2496 or something similar. But it seems like he managed improvement in bass smoothness essentially just with placement and gain/x-over settings on each sub. Also, it seems like his experiment relied on too-cheap subwoofers. That's exactly the kind of thing I'm hoping to parse.



artur9

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Re: Budget subwoofer 'swarm'?
« Reply #19 on: 15 Jan 2018, 10:57 pm »
The killer (IMO) for this being cheap and cheerful is to find a good subwoofer management device (e.g. the Behringer or miniDSP) that fits in the budget.

I got an old Xilica that works great (3 in, 6 out) with good flexibility after having no end of trouble with a miniDSP 2x4.  But even used the Xilica isn't all that cheap.