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omnidirectional loudspeakers = best design available

thewas

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oivavoi

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Interesting... But the imp "improved bose 901" speaker was the winner of the 3...
Indeed. The imp speaker is polydirectional, but with careful positioning (like happened during that blind test) it seems to function like an omni.

I have previously summed up here what we know about blind testing of omnis or quasi-omni designs. Very briefly, there is no evidence that people don't like omnis with a blindfold, quite the opposite actually.

https://audiosciencereview.com/forum/index.php?threads/omnidirectional-loudspeakers.6552/page-2

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. [edit 05.01.21: with positioning out from the walls]

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. [edit: it is actually rather bi-directional, not fully omni]

Choisel 2005 did a comparison of a conventional speaker with the Beolab 5, which is semi-omni [edit: or rather has very wide dispersion horizontally], 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.
I don't agree with the OP though that conventional forward-firing speakers are terrible. That's not a helpful way of aiding the omni cause, methinks. I like both omnis and conventional speakers. (and horns, dipoles, etc...) Would very much like to hear the poly- or bi-directional speakers @Duke has engineered!

I still find it a bit annoying that some people seem to discard the omni idea out of hand, wirhout much evidence. Omni speakers solve one of the biggest problems in speaker design, uneven dispersion and a difference between the direct and indirect sound. That's no small achievement. The question is then if the trade-offs are worth it. That's a question of preference. And unfortunately there are very few true omni designs out there, like was said I only know of MBL and Morrisons. Neither is easily available to the average music lover. And neither is perfect either: The dispersion of the MBLs is actually not perfect. They are also very big and must therefore be listened to from a distance (which necessitates a big room), and have passive crossovers. The Morrisons get most things right on paper, but earlier versions of them at least seem to have had some limitations when it comes to playing loud. That might be better with the most recent version which has become more expensive, equipped with drivers with more excursion and power capabilities.

But the fact that omnis are not more common is no argument as to whether it's a good idea or not. Dvorak keyboards are superior to qwerty keyboards but are not common. Esperanto is a more functional language than English, but the language of this forum is not Esperanto. Recumbent bikes have many advantages over regular bikes, but are not common and are seen as weird. On the other hand we get things like MQA which are inherently dumb, and are all over Tidal. That's the way of the world.
 
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anmpr1

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Thanks for that. What is discussed is how the drum's soundwave depends on what the paper's author call 'vibrational modes'.

To the percussionist the sound will appear different (more directional) depending upon whether the drum is radiating in monopole, dipole or quadrapole mode. Variables include drum volume, how hard the drum is struck, tension in the drumhead, etc.

But, more importantly, and for the listener (or for microphone placement?), the author's state that the drum's sound will be perceived as sonically equivalent regardless of position respective to the drum, as long as that position is 'several wavelengths' away from the source. Thus, one imagines that in a circular venue, where the audience could sit anywhere around the orchestra, the kettle drum would essentially sound omnidirectional. This would not be the case with, say, the horns, since anyone sitting 180 degrees behind the horns would not hear them like a listener in front.

Again, I appreciate you bringing this interesting paper to my attention.
 
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anmpr1

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In my home their was (and still is) a TRASH 80 III. I never used it (except to play some games of the time).
The higher end TRS models were not toys. In a way it was similar to a large programmable calculator. I worked at a chemical plant where formulations were mixed using one of the early model TRS computers. A home made Basic program. The machine was soon replaced, but at the time it worked well for what it did.

The Tandy CoCo (color computer) was their simple 'game' machine--it connected to a television.
 

anmpr1

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@Mr. Speakers I suggest that you send a Morrison Audio Omni speaker into @amirm for testing. That would lend a lot more credence to your opinions then a thread like this.
I wonder about it as I've not see a thorough breakdown of an omni. It is certainly one of many trade offs.

In the article, Interpreting Spinorama Charts (Manny LaCarrubba--Sausalito Audio, designers of the acoustical lens used by B&O and others https://www.sausalitoaudio.com/data/ ) we read:

If the loudspeaker has “good” behavior off axis, the sidewall reflections are beneficial to our perception of timbre, image width and stability. Except for some special case situations, the idea that we need to narrow the directivity of a loudspeaker to avoid room reflections is dead wrong – regardless of the speaker’s application. In a good sounding speaker, the shape of the early reflections curve will be similar to the on-axis and listening window curves.

The higher the directivity index the more directional a speaker is. That is to say that more of the speaker’s energy output is biased forward. A DI of 0dB is omni-directional. A high DI number is 10dB. As a general rule of thumb, lower DI speakers (DI’s in the 5dB to 7dB range) will be preferred in blind listening tests.

At the Speakerdata 2034 site the following is quoted from Dr. Toole's book:

The requirements for high sound output and highly controlled directivity result in physically large systems. Narrow dispersion (typically 90° horizontal by 40° to 50° vertical) ensures that the bulk of the radiated sound is delivered to the audience, which maximizes efficiency, and avoids reflections from walls and ceiling. This is logical for cinemas but it runs contrary to common practices in domestic listening rooms and home theaters in which listening to stereo music is an option. Most highly rated domestic loudspeakers have relatively wide and uniform dispersion.

As discussed in Chapter 7, this is also a matter of personal opinion, experience and taste. These cinema loudspeakers will clearly appeal to listeners who prefer being in a dominant direct sound field at middle and high frequencies, but will be disappointing to those who prefer the spatial presentation offered by loudspeakers with wide dispersion, up to and including bidirectional-in-phase (bipole) and horizontally omnidirectional designs. A factor in these preferences is the choice of musical genre."

Harman sells monitor loudspeakers to music and movie studios, and to consumers. If you look at the attached illustration in post #220 you will see that in order to minimize the influence of the "circle of confusion" and thereby have any hope of delivering the "art" as it was created, one needs similar loudspeakers everywhere. I know of no recording facility that uses multidirectional loudspeakers.

Toole seems to argue against too much direct and too much indirect. Obviously if one is looking for the 'art as it was created' (Toole's words) an omni is not going to be what one is looking for.
 

oivavoi

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Obviously if one is looking for the 'art as it was created' (Toole's words) an omni is not going to be what one is looking for.
Excellent summary in the post above!

On this though, I would say that this claim is debatable, at least. The question is whether reflections and more indirect sound gets in the way of "art is was created or intended". Some think that reflections degrade the perception of what is on the recording. The "second look hypothesis", on the other hand, posits that reflections - if they are spectrally similar to the direct sound - can actually enhance our perception of the direct sound, as it allows our senses to take it in one more time, kind of. A very imperfect analogy is that it similar to how effective public speakers repeat their claims several times in order for the message to really get through. Does our hearing function the same way when it comes to music? Perhaps.

There are some studies on this, and honestly they point in somewhat different directions. Some studies imply that more reflections degrade clarity etc. Others imply that reflections enhance perception (and it also depends on how delayed the reflections are, if they are timbrally different, etc). Personally I am not so sure whether these studies are "externally valid" concerning the actual perception of loudspeakers in rooms, as loudspeakers and rooms and listeners are so different from each other. So I think that one has to try it out for oneself, even though that's a terribly subjectivist thing to say. Loudspeaker research is a small, small field, unfortunately. We need more evil capitalist hifi companies who are willing to fund research in order to lure money from consumers! But that's probably not going to happen in the age of soundbars.

My own experience is this, fwiw: I have experienced wide dispersion loudspeakers and omnis which sound fuzzy and vague and blurry. That may have been because of the design of the speakers, or how they interacted with the rooms. I have also experienced wide dispersion speakers and/or omnis which imaged with a wonderful clarity and precision, and created a deep sense of envelopment and spatiality at the same time. The MBLs in a large room had that positive effect on me, whereas a couple of Duevel speakers - in another room - just felt like soup. The same thing applied to Anthony Gallo 3.5s, in my own room, which are semi-omni horizontally. Could never get them to create precise auditory images for my inner eye. So I sold them. I took a leap of faith and ordered the Morrisons because everybody who have heard them are adamant that they image very clearly, even in small rooms. They were also clearly designed according to rational principles, with no mumbo jumbo. So we'll see how they work out for me when I eventually get them.
 

krabapple

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My inquiring mind wants to know if one was (subjectively to you) better than the other or where both about the same. Other than "Pro Bose's on stands, I have only seen them hanging. I all cases of my experiencing BOSE, I remained un-impressed with Amar's sound but impressed with his marketing department.
I had the cool futuristic Bose stands for my 901 Series IV's, but I tried ceiling hanging as well. They sounded like...Bose 901s in both cases. I preferred stands because then you at least got some direct sound. I also had Bose's own AVR, with the built-in equalizer and some other features, in the classic wood laminate Bose case. I ditched the whole Bose thing in the late 1980s, as part of becoming an adult. ;> My next setup was actually a pair of Optimus bookshelves with Lineaum dipole ribbon tweeters, from Radio Shack. Plus a Velodyne subwoofer, my first sub. A whole different (and better) experience, though still not plain old forward-firing stereo.
 
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krabapple

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Interesting... But the imp "improved bose 901" speaker was the winner of the 3...
Thanks. I lost that link ages ago and I'm glad to have it again. Yes, Gary Eickmeier's Bose 901-like speakers 'won' that blind comparison!
 
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MattHooper

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As none of the music I listen to is mastered using omni directional methods or speaker systems. It's fool hardy for me to believe an omni speaker setup will restore the original sound of the instruments. In fact, many instruments are directional by nature such as a trumpet or sax.
I owned MBL omnis for years and I recorded my own acoustic guitar, voices of my family, my sons practicing sax and trombone etc.

The omnis did indeed "restore" or at least "produce" the sound of the instruments better than any other speaker design I've owned. While other speakers could produce large soundstages with precise image placement, it seems the microphones/placement generally used for recordings weren't so great at capturing the dimensionality of those objects in space, nor is the mostly forward directed sound from typical speakers, so there is a bit of a sense of images sort of "plastered on to" the soundstage, as if nothing exists *behind* them, losing a sense of realistic dimensionality.
Most directional conventional speakers certainly can sound great and very dimensional, but the nuances I'm mentioning tend to become more obvious when you can compare the two designs, as I did (I've always had multiple speakers on hand that I switch in and out of the system).

So for instance when I'd play the recording of my acoustic guitar on the forward radiating speakers, it could be tremendously clear and vivid and somewhat dimensional. But there was always this cue that it was a recording. On the Omnis, the clarity and timbral realism of the guitar was beautifully reproduced, but with the additional omni reflections, there was then a sense of full dimensionality, of there being a "behind and around" to the guitar as a real one radiates to some degree off all the walls, not just funneled forward. The sensation of hearing a real guitar being played, one I'm very familiar with, was simply more realistic. One can talk about what signal the microphone picked up and thus if the speaker is producing the sound "as the microphone heard it." But the omni produced the sound of the guitar "like the actual guitar in front of that microphone sounded live." So...depends on what exactly one thinks of as "accuracy," what one is going for.

The same went for the other instruments too. And as I've mentioned before, no other speaker design has given a better "sounds real from outside the room" effect either. The recorded sound of my son's sax coming through the omnis, when heard from outside the room, was just uncanny in it's realism. And I fooled a few people here and there in to thinking they were hearing my son practicing in that room without looking in because it was so fun to do that :)

So I know there have been endless debates about "how real instruments/voices radiate in a room." But actually living with omnis, and testing these things to some degree, leaves me with the impression that, even if neither omnis nor direct radiators get it perfect, the omnis are energizing a room in a way that more closely mimics live acoustic sources.
 

MattHooper

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I'm not sure about that. I've only owned (and still own) one set of omni-isn speakers, Mirage OMD-5. I originally bought them as bedroom speakers because they're really nice looking in this glossy burled birch finish. Even with subs (crossed as woofers using a miniDSP) they always sounded dark to me.
I always had that impression from the Mirage speakers too! Interesting.

(My MBLs were definitely not dark sounding. I can't put up with dark sounding speakers).
 

MattHooper

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How can you read this thread and not understand that Omnis have no possible ability to reproduce most music as it's currently recorded with any sort of accuracy to the original performance? It's mind boggling.
Yeesh. :rolleyes:
 

EJ3

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The higher end TRS models were not toys. In a way it was similar to a large programmable calculator. I worked at a chemical plant where formulations were mixed using one of the early model TRS computers. A home made Basic program. The machine was soon replaced, but at the time it worked well for what it did.
I set up some TRS II (big floppy disks) for a few companies. They did lots of things with them that were incredible at the time (and cheaper than other ways of doing it. I worked in business sales for Tandy Computer Centers at the time.
 

EJ3

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I had the cool futuristic Bose stands for my 901 Series IV's, but I tried ceiling hanging as well. They sounded like...Bose 901s in both cases. I preferred stands because then you at least got some direct sound. I also had Bose's own AVR, with the built-in equalizer and some other features, in the classic wood laminate Bose case. I ditched the whole Bose thing in the late 1980s, as part of becoming an adult. ;> My next setup was actually a pair of Optimus bookshelves with Lineaum dipole ribbon tweeters, from Radio Shack. Plus a Velodyne subwoofer, my first sub. A whole different (and better) experience, though still not plain old forward-firing stereo.
I used some of those Optimus with the Lineaum dipole ribbon tweeters as surround speakers in my only surround system (those Optimus did well for my use, I did not think much of them as stereo speakers in a smaller system that I used them in) that I ever had around 1990', a DENON that I ended up modifying to be 6.2. (I ditched most of that stuff by the late 90's) The mains were Dahlquist M-905's (which I still use today [in my 2.2 system], with a pair of the larger Radio Shack ported (supposedly tuned to 29 Hz by Radio Shack) sub CAB's with Pioneer Dual 4 ohm voice coil (running as a 2 ohm circuit each), Pioneer specs 20Hz to 80 Hz as the frequency response, I hope that means that this speaker can go lower. My NAD 2200's are triplets internally. One NAD 2200 bridged mono operates each Dahlquist M-905 (4 Ohm nominal) and one NAD 2200 (the one that AMIR tested) running stereo into the two 2 Ohm circuits of the subs. The room is rather large and convoluted. This year I hope to have some accurate measurements of the FR in the room at the listening position.
 

pozz

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@Mr. Speakers Do you have measurements of omnis? I don't of any speaker that is truly omnidirectional through the entire spectrum.
 

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