Omnidirectional loudspeakers ?

[Theo]

The more omnidirectional the speaker, the better your room/treatment needs to be. Unless I had a very good room I wouldn't even consider an omni.

You're right. Omni's sound great in an anechoic room...

 

[Floyd Toole]

My ears were burning - you have been talking about me. Instead of using omni speakers to add a little bit of local spaciousness to a stereo presention, why not use multichannel upmixing that is adjustable from raw stereo to over-the-top envelopment. All recordings are not the same, even within a musical genre. I sometimes spend time listening to the same movement from the same symphony from several different recordings on Tidal. The differences are staggering, ranging from near mono to full soundstage. We need adjustable spatial enhancement not fixed.

Yes I tested the Mirage M1, and ended up owning them for use in my personal "concert hall" - a large high ceilinged, irregularly shaped room. It is described in detail in Chapter 7 in my book. I moved from that house and now use adjustable Auro3D upmixing in an immersive system that I find quite satisfying. I wish we had multichannel originals of the music I want to hear. Sadly, music videos have the potential, but it is often stupidly corrupted - like not using the center channel or using all three fronts for the featured artist. Dumb!

 

[Purité Audio]

We have been talking about you, but only saying nice things!
May I ask did you ever test onmis at any point?
I completely agree regarding multi channel , is there any music specifically recorded for multi channel, I have seen very little , Christoph Fallers processors can upmix two channel but it would be interesting to hear specifically recorded material.
Keith

 

[oivavoi]

I was debating this - the psychoacoustic "evidence" on preference for or against omnis - at another forum some time ago. When I looked into the research, I saw that omnis have fared very well in all the experiments I could find where an omni was compared to a dipole or a conventional forward-firing speaker.

Flindell 1991 and Bech 1994 were direct comparisons of omnis and other designs (but Bech doesn't discuss it himself, his data were re-analyzed by Evans et al in 2009). In Flindell's study naive listeners preferred omnis, while professional listeners found the omni and the conventional speaker equally good. In Bech's study, the omni and the dipole came out on top.

As mentioned in the thread, the almost-omni Mirage M1 scored higher than any other speaker at the NRC in Canada during the 80s, so much so that dr. Toole chose it himself.

Choisel 2005 did a comparison of a conventional speaker with the Beolab 5, which is semi-omni, with regards to imaging. Beolab 5 imaged as good as the other one. This text isn't available online, but the results are discussed in depth in dr. Toole's book.

David Clark did extensive blind testing in 2010 of three speakers, the dipole Linkwitz Orions, a pair of cheap Behringer monitors, and "The Imp", a DIY quasi-omni speaker by Gary Eickmeier. The outcome of interest was "plausibility of the auditory scene", and the DIY quasi-omni came out on top.

I'm not aware of any other blind test of omnis. As said in another thread, preference testing of loudspeaker designs is not a very big scientific field. But the studies done so far certainly don't indicate that the average listener has any aversion to omnis, when they don't know what they're listening to.

 

[andreasmaaan]

I think rather than relying on speaker to speaker listening comparisons, which are confounding due to the large number of uncontrolled variables, the better approach to this question is to look at research into simulated early reflections conducted in anechoic chambers.

I'm oversimplifying here, but in broad terms this research tends to suggest that strong lateral reflections are preferred, while front-back and top-bottom reflections are not.

This implies that broad horizontal directivity is desirable, but not complete horizontal omni-directivity. Further, it implies that omni or even wide vertical directivity is undesirable.

 

[Kal Rubinson]

I completely agree regarding multi channel , is there any music specifically recorded for multi channel, I have seen very little , Christoph Fallers processors can upmix two channel but it would be interesting to hear specifically recorded material.

Are you kidding me? I have written, so far, 96 columns based on such recordings.

Here are links to my multichannel record reviews: https://www.stereophile.com/search/node/recordings in the round "Recordings in the Round"
(There are a number of other sites but why not start with mine?)

 

[Purité Audio]

Thanks Kal ,I will!
BW Keith

 

[oivavoi]

I think rather than relying on speaker to speaker listening comparisons, which are confounding due to the large number of uncontrolled variables, the better approach to this question is to look at research into simulated early reflections conducted in anechoic chambers.

I'm oversimplifying here, but in broad terms this research tends to suggest that strong lateral reflections are preferred, while front-back and top-bottom reflections are not.

This implies that broad horizontal directivity is desirable, but not complete horizontal omni-directivity. Further, it implies that omni or even wide vertical directivity is undesirable.

Partly agree, partly disagree The benefit of doing controlled experiments with single reflections in an anechoic chamber is that the experiment becomes "internally valid" - you know that you tested for the one thing you actually wanted to test, and not other things which you don't know about. The disadvantage, though, is that you don't know whether the experiment is "externally valid" - whether it can be generalized beyond the conditions of the experiment.

When it comes to this case, my gut tells me that inducing single reflections in an anechoic chamber is so different from listening to music from loudspeakers in a small reflective room, that it really doesn't tell us that much. Do we react in the same way to a single reflection, from whatever direction, as to many reflections coming from many directions at once? Intuitively, I would think that the answer is no - a single reflection won't be perceived the same way.

Btw, I don't think it's correct that vertical reflections are generally not preferred by listeners in the anechoic studies. The latest study I saw on this said that the listeners in the study preferred vertical reflections as well: http://www.aes.org/e-lib/browse.cfm?elib=18245

I've also seen several studies which indicate that reflections from behind the listener can be experienced as beneficial: http://www.iida-lab.it-chiba.ac.jp/.../09.The.role.of.reflections.from~.AA-2001.pdf

As to reflections from behind the speakers being undesirable, this seems to be something that has been taken for granted by many psychoacoustic researchers. But I struggle to understand what this consensus is built on. I've looked into it, and haven't been able to find more than one or two quite old studies which indicated that reflections from the front were undesirable. I even opened a thread about it here, but didn't get that much in the form of qualified response: https://www.audiosciencereview.com/...c-effects-of-front-and-back-reflections.2207/

But as I said, I'm a bit skeptical as to how externally valid all of these studies are. My personal experience remains that I prefer omni directivity for acoustic music, and relatively narrow directivity for electronic studio music. This seems quite reasonable to me, in that omni directivity mimics how real instruments interact with a room, while the artificial soundstage of electronic studio music starts feeling strange when it behaves as if it consisted of acoustic instruments. I don't think that neither of these preferences is right or wrong. Other people may perceive it differently - depending on musical taste, experience with real-world acoustic music, acquired hifi habits, and more.

 

[andreasmaaan]

Partly agree, partly disagree The benefit of doing controlled experiments with single reflections in an anechoic chamber is that the experiment becomes "internally valid" - you know that you tested for the one thing you actually wanted to test, and not other things which you don't know about. The disadvantage, though, is that you don't know whether the experiment is "externally valid" - whether it can be generalized beyond the conditions of the experiment.

When it comes to this case, my gut tells me that inducing single reflections in an anechoic chamber is so different from listening to music from loudspeakers in a small reflective room, that it really doesn't tell us that much. Do we react in the same way to a single reflection, from whatever direction, as to many reflections coming from many directions at once? Intuitively, I would think that the answer is no - a single reflection won't be perceived the same way.

Btw, I don't think it's correct that vertical reflections are generally not preferred by listeners in the anechoic studies. The latest study I saw on this said that the listeners in the study preferred vertical reflections as well: http://www.aes.org/e-lib/browse.cfm?elib=18245

I've also seen several studies which indicate that reflections from behind the listener can be experienced as beneficial: http://www.iida-lab.it-chiba.ac.jp/.../09.The.role.of.reflections.from~.AA-2001.pdf

As to reflections from behind the speakers being undesirable, this seems to be something that has been taken for granted by many psychoacoustic researchers. But I struggle to understand what this consensus is built on. I've looked into it, and haven't been able to find more than one or two quite old studies which indicated that reflections from the front were undesirable. I even opened a thread about it here, but didn't get that much in the form of qualified response: https://www.audiosciencereview.com/...c-effects-of-front-and-back-reflections.2207/

But as I said, I'm a bit skeptical as to how externally valid all of these studies are. My personal experience remains that I prefer omni directivity for acoustic music, and relatively narrow directivity for electronic studio music. This seems quite reasonable to me, in that omni directivity mimics how real instruments interact with a room, while the artificial soundstage of electronic studio music starts feeling strange when it behaves as if it consisted of acoustic instruments. I don't think that neither of these preferences is right or wrong. Other people may perceive it differently - depending on musical taste, experience with real-world acoustic music, acquired hifi habits, and more.

Will be interesting to read some of those papers, thanks

 

[andreasmaaan]

This seems quite reasonable to me, in that omni directivity mimics how real instruments interact with a room, while the artificial soundstage of electronic studio music starts feeling strange when it behaves as if it consisted of acoustic instruments. I don't think that neither of these preferences is right or wrong.

Oh BTW, I'm not sure I agree with your statement about omni directivity mimicking how real instruments interact with the room. Each instrument has a fairly unique polar response. The only real trend across most instruments (including voice) is some sort of an upward-sloping DI, at least according to the studies I've looked at.

Couldn't agree more about there not being a right or wrong, however.

 

[Dogen]

I have a set of the multichannel Beethoven symphonies from Tacet I’m waiting to try. IMO multichannel done well in the new frontier in better sound reproduction, but it’s impractical for most people in most rooms.

 

[oivavoi]

Oh BTW, I'm not sure I agree with your statement about omni directivity mimicking how real instruments interact with the room. Each instrument has a fairly unique polar response. The only real trend across most instruments (including voice) is some sort of an upward-sloping DI, at least according to the studies I've looked at.

Correction taken! You are right. What I meant was rather that a musical ensemble with different instruments, seen as a whole, will have a directivity that is more omni than most forward-firing speakers.

 

[andreasmaaan]

Btw, I don't think it's correct that vertical reflections are generally not preferred by listeners in the anechoic studies. The latest study I saw on this said that the listeners in the study preferred vertical reflections as well: http://www.aes.org/e-lib/browse.cfm?elib=18245

That's an interesting study. I have a few reservations about it though. Firstly, the simulated vertical reflections added 1.5dB to the sound power at the listening position. All else equal, wouldn't you expect this to result in a clear preference for the simulated vertical reflection? Looking at the results of the "positive voting" group, all seemed to state an overall preference for the simulated reflection, while generally giving a negative rating on spatial and timbral quality. This would seem to suggest that the raised SPL was the most likely explanation for subject preferences in this case, I would have thought.

Still digesting it though, these are just initial thoughts... Interested to know what you make of it?

 

[oivavoi]

That's an interesting study. I have a few reservations about it though. Firstly, the simulated vertical reflections added 1.5dB to the sound power at the listening position. All else equal, wouldn't you expect this to result in a clear preference for the simulated vertical reflection? Looking at the results of the "positive voting" group, all seemed to state an overall preference for the simulated reflection, while generally giving a negative rating on spatial and timbral quality. This would seem to suggest that the raised SPL was the most likely explanation for subject preferences in this case, I would have thought.

View attachment 21450

Still digesting it though, these are just initial thoughts... Interested to know what you make of it?

I actually thought about the spl thing when I read it some time ago. But the authors claim that this is most similar to how a reflection will work in real-life... not sure what I think about it. You make a valid point of criticism. Interesting observation that they rated it worse when it came to timbre etc. Need to re-read O think!

 

[andreasmaaan]

I actually thought about the spl thing when I read it some time ago. But the authors claim that this is most similar to how a reflection will work in real-life... not sure what I think about it. You make a valid point of criticism. Interesting observation that they rated it worse when it came to timbre etc. Need to re-read O think!

Yeh, I read what the authors said about that. The thing is though, that IRL a listener can always control the volume to taste, it isn't dependent on the presence of the reflection. So I think the authors may have made a mistake in choosing not to compensate for it in the study...

 

[andreasmaaan]

I've also seen several studies which indicate that reflections from behind the listener can be experienced as beneficial: http://www.iida-lab.it-chiba.ac.jp/.../09.The.role.of.reflections.from~.AA-2001.pdf

My first reaction this one also comes with some reservations Not about the methodology in particular, but rather about its applicability to listening in small rooms. In this study, the authors simulated both early reflections and reverberation, using an RT of 1.5s and early reflection times of between 20ms and 65ms.

In a typical small room (home or studio), even a large-ish one, early reflections will arrive at intervals more in the 5-30ms range, and the RT is likely to be closer to 0.5s than 1.5s. So I'm not sure this study is particularly applicable to small rooms.

But again, I need to go through it in more detail a second time, and am keen to hear your thoughts...

EDIT: broadened the likely interval range for early reflections to 5-30ms to reflect a wider variety of small rooms.

 

[Ron Texas]

Harman found most preferred is a flat on axis response with a downward sloping though even off axis response. The off axis response should be smooth with very little peaking or dipping in the response. Here is the recently reviewed Revel 228be on the lateral response graph done by Stereophile.
View attachment 21342

And here is the MBL graph from Stereophile. Presumably the MBL would score lower than the Revel due to having too much upper frequency energy off axis.

View attachment 21343

For comparison here is the graph for the "unacceptably engineering", "bad, bad, bad" LS50:

JA's description:

"The LS50's horizontal and vertical dispersion, referenced to the tweeter-axis response, are shown in figs. 4 and 5, respectively. The radiation pattern in both planes is very uniform, with the usual but well-controlled narrowing of the pattern in the top octaves, though the vertical dispersion is wider than I had expected from my auditioning. "

One ASR member has a completely different interpretation of this data. It's what happens when a person with no common sense reads enough to learn the lingo, but still doesn't understand the big picture. Who do you believe, JA, many other professional reviewers or that one ASR member who is obsessed with the LS50. Perhaps his problem is he doesn't like this renowned loudspeaker and has a bad case of cognitive dissonance from being in disagreement with so many professional reviewers. He then desperately struggles to misinterpret data and research to sooth his soul. I see this as spreading misinformation.

 

[svart-hvitt]

I think @Floyd Toole asks the right question: Why not bring the right equipment to the job?

If the job is creating an immersive sound, multichannel is the tool. Choose good speakers on conventional metrics to do the job of each channel.

And as far as I understand, even an upsampling algorithm (can be expensive!) from 2 to 4 or more channels will do the trick if the goal is immersive sound.

 

[andreasmaaan]

I think @Floyd Toole asks the right question: Why not bring the right equipment to the job?

If the job is creating an immersive sound, multichannel is the tool. Choose good speakers on conventional metrics to do the job of each channel.

And as far as I understand, even an upsampling algorithm (can be expensive!) from 2 to 4 or more channels will do the trick if the goal is immersive sound.

Very much agree with you! Although given that many people will - whether owing to budget, space, or habit - have only two speakers in their room, I don't think it's fruitless to ask what the best way to do it is, within this limitation.

 

[oivavoi]

Multichannel requires a tighter sweetspot, though, unlike omni speakers. But I agree, multichannel is probably the superior alternative for those who can manage to arrange it in their homes - at least in the sweet spot.