Dipole bass vs multisub monopole bass

0 Members and 1 Guest are viewing this topic. Read 3419 times.

Duke

Re: Dipole bass vs multisub monopole bass
« Reply #20 on: 14 May 2017, 10:36 pm »
They do not. There are many examples of flow resistance enclosures that generate cardioid response, ME Gethain, Music & Design (John K), http://kimmosaunisto.net/CardSub/CARDSUB.html etc.

Thank you very much for the link!  I didn't realize that flow resistance was practical down into the subwoofer range.   EQ is probably still called for, I think I saw 10 dB at 30 Hz mentioned in the article, but I haven't yet taken the time to really read it closely. 

Jonathon Janusz

  • Full Member
  • Posts: 686
Re: Dipole bass vs multisub monopole bass
« Reply #21 on: 14 May 2017, 11:04 pm »
Anand, my suggestion was in response to Duke's proposition of needing subs using a pair of drivers each, thinking that being able to reduce that to one driver per sub in handling the pattern shaping with the cabinet would reduce having to manage processing for two drivers independently and having to have two amp channels per sub (how I interpreted Duke's idea) to create the desired radiation pattern directly through manipulating driver output.  I thought this might at least make it a little easier to put together a system based on cardioid radiation pattern subs.

I'm sorry if that sounded like I was suggesting no EQ or amplification was needed at all; just a little bit less.  Of course, this might then add the complication of having to aim the subs physically as well as limit placement options for them.  Also, of course, if a system already is using a signal processor capable of handling the requisite number of channels and the number of available amp channels isn't a problem, the concern becomes a non-issue.

AJinFLA

  • Industry Participant
  • Posts: 992
  • Soundfield Audio Loudspeakers
    • Soundfield Audio
Re: Dipole bass vs multisub monopole bass
« Reply #22 on: 15 May 2017, 12:06 am »
EQ is probably still called for, I think I saw 10 dB at 30 Hz mentioned in the article, but I haven't yet taken the time to really read it closely.
Yes, unless using a high Qts driver or specialized one like from AE et al, just like many sealed subs, a bit of EQ is needed if one wants to get really deep.
However, there is really no benefit to doing so below 40 hz or so, where modes are sparse. There, monopoles still rule, as many as one would wish. Even in mono. The research I linked does not suggest otherwise.

cheers,

AJ

Duke

Re: Dipole bass vs multisub monopole bass
« Reply #23 on: 15 May 2017, 01:09 am »
Yes, unless using a high Qts driver or specialized one like from AE et al, just like many sealed subs, a bit of EQ is needed if one wants to get really deep.
However, there is really no benefit to doing so below 40 hz or so, where modes are sparse. There, monopoles still rule, as many as one would wish. Even in mono. The research I linked does not suggest otherwise.

cheers,

AJ

That's pretty much the conclusion I was coming to, i.e., that the benefits of cardioid bass started to be outweighed by the EQ requirements at very low frequencies.   

poseidonsvoice

  • Full Member
  • Posts: 3144
  • Vector - I've got Direction & Magnitude! Oh Yeah!
    • 2 channel/7 channel setup
Re: Dipole bass vs multisub monopole bass
« Reply #24 on: 15 May 2017, 01:38 am »
Jonathan,

Thanks for the clarification! The internet unfortunately isn't the best place for a sequential conversation and hence my concerning query, and my apologies if I sounded a bit obtuse.

AJ & Duke,

Below 40 Hz where you are dealing with very few modes, yes,  large psychotic monopoles are key. But as far as the area from 40 Hz to a little below the Schroeder frequency of the room, can we agree that this is the modal region and that another option (other than multiple asymmetrically placed monopole subs receiving a summed mono signal) is a pair of cardioid subs receiving a stereo signal? And that this cardioid sub pair can then maintain spatialization and minimize the FR ripple as well as multiple assymetrically placed monopole subs?

I need to download that paper AJ linked! And I need to become an AES member!

Thanks,
Anand.
« Last Edit: 15 May 2017, 06:12 am by poseidonsvoice »

Duke

Re: Dipole bass vs multisub monopole bass
« Reply #25 on: 15 May 2017, 01:47 am »
No, I think at the time no one had even thought about a swarm approach, let alone tried it. 

As you know from my RMAF reporting, I do really like the AK Swarm  :thumb:

Thank you very much, Tyson. 

I think that any enhanced sense of image size or spaciousness or whatever that any of my systems produced at RMAF were more due to the "late ceiling splash" energy than anything else. 

Mainly my point was more of a "be careful what you wish for", especially with high output low bass.  For me, room pressurization was a very real negative.

But I think a lot of people haven't had a super high output low bass system and might end up with a nasty surprise if/when they finally get one.

And you made that point very well - thank you for taking the time to do so! 

Duke

Re: Dipole bass vs multisub monopole bass
« Reply #26 on: 15 May 2017, 01:55 am »
AJ & Duke,

Below 40 Hz where you are dealing with very few modes, yes,  large psychotic monopoles are key. But as far as the area from 40 Hz to a little below the Schroeder frequency of the room, can we agree that this is the modal region and that another option (other than multiple asymmetrically placed monopole subs receiving a summed mono signal) is a pair of cardioid subs receiving a stereo signal. This cardioid sub pair can then maintain spatialization and minimize the FR ripple as well as multiple assymetrically monopole subs?

I don't know enough about cardioids to say whether two cardioid subs are better, worse, or about the same as four monopole subs in the modal region.  AJ knows more about cardioids than I do, and has read (and understood!) more research on the subject than I have, so he can probably answer that better than I can.  My inclination is to think that four monopoles will be smoother in-room that two cardioids, especially if we either reverse the polarity of one or, if it's a two-amp setup, do the Griesinger phase-quadrature-thing. 

My understanding is that two stereo cardioid subs would have better spatial resolution than the distributed monopole subs, assuming the latter are all receiving the same summed mono signal.   How far that carries over when we have left and right channel signals going to the respective left and right pairs of monopole subs, I don't know. 

G Georgopoulos

  • Restricted
  • Posts: 1255
Re: Dipole bass vs multisub monopole bass
« Reply #27 on: 15 May 2017, 02:12 am »
Which is the best Guys,dipole or multiple monopole subs,too much tech jargon ,for us with limited tech knowledge,my opinion is the bass should be at the same loud level and spatial level as the other drivers,there are some car subs that have tones of bass!(for me a no no in hifi)

Jonathon Janusz

  • Full Member
  • Posts: 686
Re: Dipole bass vs multisub monopole bass
« Reply #28 on: 15 May 2017, 02:29 am »
It seems like, based on this conversation if I'm reading it correctly, that the answer is actually a combination of the two.  Assuming we're talking about a two-channel stereo setup, the ideal appears to be a pair of stereo subs (ideally cardioid in radiation pattern, although a dipole would seem a desirable second option due to similar pattern control improving issues dealing with room modes) playing down to roughly 40Hz.  From there to as far down as one would like to go, the research AJ references suggests a distributed set of monopole subs (like Duke's swarm setup) is the way to go, as sound localization no longer stands as an issue.

This combination of subs would theoretically present the smoothest, most even response below a frequency where spatial perception fails people, while maintaining proper stereo separation and imaging between there and up to where whatever chosen main speakers are in the system take over.  The interesting wrinkle in bass management presented so far in this discussion suggests that between 130Hz and 40Hz-ish there is a great need for processing and EQ to make that range work well with the stereo pair of subs, but below that, saturation to even out room response through summed dissimilar sources is key to the exercise, with whatever little processing or EQ one chooses to do being mostly a function of calibrating the swarm of lowest frequency subs to most optimally compensate and correct for each other.

Do I have that about right?

Duke

Re: Dipole bass vs multisub monopole bass
« Reply #29 on: 15 May 2017, 04:31 am »
Which is the best Guys,dipole or multiple monopole subs,too much tech jargon ,for us with limited tech knowledge,my opinion is the bass should be at the same loud level and spatial level as the other drivers...

A well set-up multiple monopole system does a very good job of having the same loudness level across the bass region.   It also can have very good spatial level, with a little bit more cost and complexity.

But I would not try to tell someone what is "best" without knowing a lot about their situation, because what is best for them depends very much on the situation. 

It seems like, based on this conversation if I'm reading it correctly, that the answer is actually a combination of the two.  Assuming we're talking about a two-channel stereo setup, the ideal appears to be a pair of stereo subs (ideally cardioid in radiation pattern, although a dipole would seem a desirable second option due to similar pattern control improving issues dealing with room modes) playing down to roughly 40Hz.  From there to as far down as one would like to go, the research AJ references suggests a distributed set of monopole subs (like Duke's swarm setup) is the way to go, as sound localization no longer stands as an issue.

My understanding is that, among recordings, there is a continuum that extends from "pure mono bass" (below say 100 Hz or so) to "true stereo bass", and that most recordings are pretty close to the "mono" end of this continuum, with classical music recordings most likely to be the exceptions.  In other words, I think that most recordings have essentially mono bass, from a perceptual standpoint if not literally.

Now I don't think there is anything wrong with having a stereo subwoofer system, and about 1/4 to 1/3 of my Swarm customers use two amps, so they can either set them up for stereo, or use the Griesinger phase-quadrature configuration, or both.

I'm not ready to concede that a stereo pair of cardioid subs offers more than a minor spatial advantage over a stereo-configured four-piece Swarm-type system.  And if the recording has insignificant stereo separation down low, then a two-amp phase-quadrature Griesinger setup would probably tip the scales in favor of the Swarm, because it would synthesize the sort of spatial impressions we get from good stereo bass.  I believe Griesinger's word for it is "immersion". 

Now if you are going to use stereo cardioid or dipole subs, then it may very well make sense to add a monopole sub for the very low frequencies.   This may or may not correspond to the transition from the modal zone to the pressure zone - it may simply be a matter of not having the amplifier headroom and/or woofer excursion capability called for by the equalization that would be needed to extend the response low enough.

However if we are able to make the transition from dipole/cardioid to monopole in about the same frequency region as the transition from modal to pressure zone, we might be able to get away with just using a single monopole sub.

This combination of subs would theoretically present the smoothest, most even response below a frequency where spatial perception fails people, while maintaining proper stereo separation and imaging between there and up to where whatever chosen main speakers are in the system take over.

I think dipole/cardioid over most of the bass region + monopole (perhaps in multiples) down low would work very well. 

The interesting wrinkle in bass management presented so far in this discussion suggests that between 130Hz and 40Hz-ish there is a great need for processing and EQ to make that range work well with the stereo pair of subs, but below that, saturation to even out room response through summed dissimilar sources is key to the exercise, with whatever little processing or EQ one chooses to do being mostly a function of calibrating the swarm of lowest frequency subs to most optimally compensate and correct for each other.

This is an area where multiple monopole subs, with one in reverse polarity, does well:  Very good results are not limited to the few with powerful measurement and signal processing capability.    One of my Swarm customers has a very powerful Meridian processor that he had had a technician calibrate for his system previously.  When he got the Swarm, he set it up according to my guidelines, reset all the filters in the Meridian processor to "flat", and called in the technician to fine-tune the system.   The ONLY thing the technician did to the Swarm was, tweak the level - no EQ was needed!  Quoting now from his e-mail:
 
"... The other big change I made was replacing my single [competitor's sub] with your AudioKinesis Swarm asymmetric four-subwoofer array this past summer.  Results - unbelievable bass with no suckout anywhere in the room ! 

"The MRC program can insert up to 60 digital filters between ~10hz and 250 hz to eliminate the dominant room resonant nodes.  The previous calibration resulted in 16 filters distributed across 5.1 speakers, (the left and right Vandersteen Quatro Woods, VCC-5 center channel, the two VSM-1 surround speakers, and the [competitor's subwoofer].  The VCC and the two VSM's were crossed over at 80 hz, while the Quatros were set for full range.  The speakers are in a 16' wide by 22' deep symmetric room using the ITU 5.1 placement standard).  With your Swarm taking the place of the [other sub], the MRC only inserted 2 filters - one for each VSM-1 !  (I think this may due to their proximity to the ceiling corners in the back of the room.)  The Quatro Wood 11-band analog equalizers were set flat, and the Meridian processor left them that way. 

"The asymmetric Swarm array works so well that the only "calibration" really required is for level.  (We were able to get every speaker within 1/2 dB, prior to the processor burst noise sequence and resultant filter build).  It has rendered both the MRC and Vandersteen's analog equalizers unnecessary for my room [emphasis in the original].  After reading Earl Geddes and Fred Toole's papers, I knew it would force the room nodal distribution to be inherently flatter, but I had no idea how much improvement was going to occur.

"The tech., who has performed dozens of these calibrations, said he has never seen anything like this.  The room is rendered literally flat in frequency response and spatial energy distribution - sonically the room disappears.  We played one of Kal Rubinson's recommended demo discs, the 100th anniversary for the San Francisco Symphony Orchestra using the John Adams piece, "Short Ride on a Fast Machine", and you would swear you were in the hall.  You can "feel" the ripple in the tympani skins !  Very impressive."

In other words, zero equalization was needed to achieve results that the technician felt could not be improved on by using the Meridian processor's filters.  All he did was correct the gain setting on the Swarm amp.  I'm not saying that you can't get equal or better results with a more complicated cardioid/monopole hybrid system, but it's probably going to be a lot harder to get dialed in.

Returning to the spatial issue for a moment - in my opinion there is a LOT more spatial information that can be made good use of north of 100 Hz.  But that's another thread for another day.



Folsom

Re: Dipole bass vs multisub monopole bass
« Reply #30 on: 15 May 2017, 05:33 am »
I'm been looking for examples of cardioid subwoofer setups. Do they require DSP? It seems like that is a way to do it, but I get a lot of odd ball things that are just canceling phase of everything behind the subwoofers from what I can tell.

G Georgopoulos

  • Restricted
  • Posts: 1255
Re: Dipole bass vs multisub monopole bass
« Reply #31 on: 15 May 2017, 05:53 am »
A well set-up multiple monopole system does a very good job of having the same loudness level across the bass region.   It also can have very good spatial level, with a little bit more cost and complexity.

But I would not try to tell someone what is "best" without knowing a lot about their situation, because what is best for them depends very much on the situation. 



I've never listened to multiple subs,so i don't know what you're talking about,my situation is average room,i'm interested to know about the spatial of multiple subs and how they work,is it the same with surround sound?,thanks Duke...



poseidonsvoice

  • Full Member
  • Posts: 3144
  • Vector - I've got Direction & Magnitude! Oh Yeah!
    • 2 channel/7 channel setup
Re: Dipole bass vs multisub monopole bass
« Reply #32 on: 15 May 2017, 05:58 am »
I'm been looking for examples of cardioid subwoofer setups. Do they require DSP? It seems like that is a way to do it, but I get a lot of odd ball things that are just canceling phase of everything behind the subwoofers from what I can tell.

Yes, they do require EQ/DSP. Read Music and Designs primer here: http://www.musicanddesign.com/NaO-II-U-frame.html

And here: http://www.musicanddesign.com/u_frame.html

John Kreskovsy has done quite a bit of work with cardioid designs.

Best,
Anand.

poseidonsvoice

  • Full Member
  • Posts: 3144
  • Vector - I've got Direction & Magnitude! Oh Yeah!
    • 2 channel/7 channel setup
Re: Dipole bass vs multisub monopole bass
« Reply #33 on: 15 May 2017, 06:04 am »
I've never listened to multiple subs,so i don't know what you're talking about,my situation is average room,i'm interested to know about the spatial of multiple subs and how they work,is it the same with surround sound?,thanks Duke...

You need to learn how to walk before you run. We all have "average" rooms, so don't worry. It also has nothing to do with surround sound.

Theory:

Very technical: http://www.wghwoodworking.com/audio/low-frequency_optimization_using_multiple_subwoofers.pdf

Less technical: http://www.wghwoodworking.com/audio/multsubs.pdf

http://www.gedlee.com/Papers/multiple%20subs.pdf

Application:

http://www.hifizine.com/2011/06/bass-integration-guide-part-1/

http://www.hifizine.com/2011/09/bass-integration-guide-part-2/

http://www.hifizine.com/2012/06/bass-integration-guide-part-3/


Best,
Anand.

Duke

Re: Dipole bass vs multisub monopole bass
« Reply #34 on: 15 May 2017, 06:12 am »
I've never listened to multiple subs,so i don't know what you're talking about,my situation is average room,i'm interested to know about the spatial of multiple subs and how they work,is it the same with surround sound?,thanks Duke...

I will try to explain without using too much tech jargon.

The worst problem that a single subwoofer has is, what the room does to its frequency response.  As the bass energy bounces around the room, the reflections combine in a way that causes peaks at some frequencies and dips at others.  We can move the subwoofer or move the listening position and that changes the peak-and-dip pattern, but does not eliminate it. 

The main idea of multiple subs is, to solve this problem.   The peaks are the worst part if this problem. 

In the kind of multiple sub system I manufacture, the four subs are scattered around the room.  If we look at each sub all by itself, the room will cause its response to have big peaks and dips.  But the peaks and dips are at different frequencies for each sub because they are each in a different location.  All of these different peaks and dips added together actually result in much smoother response than we could get from just one sub, no matter how carefully we position it.  And no matter where you are in the room, you have the sum of four different peak-and-dip patterns, so the bass is smooth throughout the room. 

And smooth bass sounds "fast", because it is the peaks that sound slow. 

To answer your other question, multiples subs usually are not like surround sound, where each speaker gets a different signal.  Multiple subs usually all get the same signal. 

Duke

Re: Dipole bass vs multisub monopole bass
« Reply #35 on: 15 May 2017, 06:15 am »
Yes, they do require EQ/DSP. Read Music and Designs primer here: http://www.musicanddesign.com/NaO-II-U-frame.html

And here: http://www.musicanddesign.com/u_frame.html

John Kreskovsy has done quite a bit of work with cardioid designs.

Best,
Anand.

Thank you Anand!  I was hoping you would reply to Folsom because you know a lot more about cardioids than I do. 

G Georgopoulos

  • Restricted
  • Posts: 1255
Re: Dipole bass vs multisub monopole bass
« Reply #36 on: 15 May 2017, 06:21 am »
I will try to explain without using too much tech jargon.

The worst problem that a single subwoofer has is, what the room does to its frequency response.  As the bass energy bounces around the room, the reflections combine in a way that causes peaks at some frequencies and dips at others.  We can move the subwoofer or move the listening position and that changes the peak-and-dip pattern, but does not eliminate it. 

The main idea of multiple subs is, to solve this problem.   The peaks are the worst part if this problem. 

In the kind of multiple sub system I manufacture, the four subs are scattered around the room.  If we look at each sub all by itself, the room will cause its response to have big peaks and dips.  But the peaks and dips are at different frequencies for each sub because they are each in a different location.  All of these different peaks and dips added together actually result in much smoother response than we could get from just one sub, no matter how carefully we position it.  And no matter where you are in the room, you have the sum of four different peak-and-dip patterns, so the bass is smooth throughout the room. 

And smooth bass sounds "fast", because it is the peaks that sound slow. 

To answer your other question, multiples subs usually are not like surround sound, where each speaker gets a different signal.  Multiple subs usually all get the same signal.

Duke,has been tried before,thank you for your easy explanation,all the best with it.

Folsom

Re: Dipole bass vs multisub monopole bass
« Reply #37 on: 15 May 2017, 08:38 am »
Yes, they do require EQ/DSP. Read Music and Designs primer here: http://www.musicanddesign.com/NaO-II-U-frame.html

And here: http://www.musicanddesign.com/u_frame.html

John Kreskovsy has done quite a bit of work with cardioid designs.

Best,
Anand.

It drives me nuts there's no pictures of his subwoofers. And his have no DSP. As nice as they are in graphs, I'd have to hear them to know if the bass actually sounded good with all the dampening; so perhaps DSP makes more sense.

Then again the swarm is pretty easy :D


poseidonsvoice

  • Full Member
  • Posts: 3144
  • Vector - I've got Direction & Magnitude! Oh Yeah!
    • 2 channel/7 channel setup
Re: Dipole bass vs multisub monopole bass
« Reply #38 on: 15 May 2017, 10:37 am »
It drives me nuts there's no pictures of his subwoofers. And his have no DSP. As nice as they are in graphs, I'd have to hear them to know if the bass actually sounded good with all the dampening; so perhaps DSP makes more sense.

Then again the swarm is pretty easy :D

There are pictures of his subs (it's just a box with an open back). Look in my gallery under XJ-12. The U-frame sub design that he has incorporated into his dipole speakers use DSP as did mine. He recommends a MiniDSP (or equivalent) with all his current builds as well.

Best,
Anand.

AJinFLA

  • Industry Participant
  • Posts: 992
  • Soundfield Audio Loudspeakers
    • Soundfield Audio
Re: Dipole bass vs multisub monopole bass
« Reply #39 on: 15 May 2017, 12:11 pm »
Below 40 Hz where you are dealing with very few modes, yes,  large psychotic monopoles are key. But as far as the area from 40 Hz to a little below the Schroeder frequency of the room, can we agree that this is the modal region and that another option (other than multiple asymmetrically placed monopole subs receiving a summed mono signal) is a pair of cardioid subs receiving a stereo signal? And that this cardioid sub pair can then maintain spatialization and minimize the FR ripple as well as multiple assymetrically placed monopole subs?
Anand, I should be clear that there is no one size shoe that fits all. There are dipoles and cardioids than extend to below 20hz and may prove all one persons needs for bass. The fact is monopoles are simply more efficient in this area and there is no real benefit to gradient output in this region below 40-50hz, or non-mono reproduction.
But a very common misunderstanding is that gradients are less efficient than monopoles. This is false. Above F equal, they are more efficient. So it all depends on what frequency F equal is in the system.
The other issue regards both spatial reproduction and localization. Multiple subs can indeed yield smoother amplitude response, but that is limited to around an upper end of about 80-90hz, due to localization. There are lots of modal issues above this, in typical rooms, up to several hundred Hz, typically around 400hz or so.
Multiple subs are useless between 90-400hz. Most folks then resort to both EQ and/or so called "treatments", but these have there own issues.
Gradient systems can address issues in this region where monopoles by themselves, cannot.

I need to download that paper AJ linked! And I need to become an AES member!
Yes  :wink:
It's the best $125 spent in audio, if that is ones interest.

cheers,

AJ