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Why are there so few omnidirectional speakers?

Webninja

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Aren’t HomePods omnidirectional?

Not saying they are great for critical listening, but for the $ good for background.
 

Newman

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It should be very suitable for classical and especially orchestral music, which is a huge genre.
...and...
Most instruments radiate sound on many directions. In an orchestra, sound is omnidirectional though not evenly so.
Not so.

The summation of many directional instruments may well produce omnidirectional sound. Strings will be more omnidirectional.
Dr Floyd Toole, probably the preeminent living authority on sound reproduction and listener preference, is far from admiring of omnidirectional loudspeakers. Link. He is also a big listener to classical music.

cheers
 

DanielT

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But here among these DIYs at this year's show there were many dipoles and omnis::)

 

Head_Unit

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Much sound gets reflected anyway even with conventional speakers. Who listens in an an anechoic chamber?
I though that Toole et al‘s research showed that speakers with an even off-axis response were preferred. Surely it doesn’t get more even than an omni?
Ah by definition I suppose so, if they are truly evenly omnidirectional. However in that case a LOT more reflected sound will be present than with typical speakers which are already beaming by the midrange. So as others noted here this can work with such speakers well out in a large room-the reflections will come later than the initial sound which can be pleasing. Close to walls will give a lot of early reflections generally regarded as degrading to the sound. Toole's research can't be extrapolated to Omnis because AFAIK they did not test those kind of speakers.
- I'd also note that a famous omnidirectional, the Ohm Walsh, is not actually omnidirectional at upper frequencies. They actually block off the sound.
 

Recluse-Animator

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Or amazing room correction, which is essential for any room and any speaker without amazing room treatment anyway.


Much sound gets reflected anyway even with conventional speakers. Who listens in an an anechoic chamber?
Normal speakers don't send high and mid frequencies 360 degrees.
They only send it from the front and how wide a dispersion they have depends on if the they have a horn / wavequide or not.
Dipole speakers sends sound to the back, but they're not normal speakers.
 

Recluse-Animator

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There are many highly regarded top end Omni or Bipole/Dipole speakers.

Contrary to popular belief (by the Monopole majority) - they can and do sound great, and can do superb imaging - some of them have a narrow sweetspot, others a sweet spot you can walk around in.

They key with these designs is always the room - you have to consider the reflections as integral to your setup - they are desirable as long as they are sufficiently delayed so they don't interfere with the imaging... which means the speakers have to be located far enough from the closest walls to ensure that delay - if that cannot be achieved, then absorbers/diffusers need to be placed on the walls that are too close.

Omni/Di/Bipoles energise the room very differently from monopoles - at one stage I ran a 4.1 all electrostatic surround setup - all speakers were well out into the room, it took a LOT of space - but it sounded fantastic... - the space and the sense of being overwhelmed by large monoliths, ended up getting them replaced with more traditional speakers... but in terms of the sound, I miss them.
Sanders dipole electrostatic speakers can be placed closed to walls, but they're active and has room correction.
Ohm omnidirectional speakers are designed with close to wall positioning in mind. They are passive, but have a switch for different placement.
 

dlaloum

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Sanders dipole electrostatic speakers can be placed closed to walls, but they're active and has room correction.
Ohm omnidirectional speakers are designed with close to wall positioning in mind. They are passive, but have a switch for different placement.

The problem with getting good imaging remains - the placement of designs like the Sanders and Ohm close to a wall is intended to provide a desired overall room voicing - a room Target Curve....

But what is not corrected in these approaches is the smearing of the imaging caused by the reflections from a nearby wall, arriving almost simultaneously with the initial speaker signal ... which confuses our psychoacoustic sense of direction on which we depend for imaging.

The only way to resolve that problem is to either absorb/diffuse the reflection (wall treatment) - or delay it (by moving the speaker further from the wall).
 

dlaloum

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Normal speakers don't send high and mid frequencies 360 degrees.
They only send it from the front and how wide a dispersion they have depends on if the they have a horn / wavequide or not.
Dipole speakers sends sound to the back, but they're not normal speakers.
"Normal"..... such an interestingly loaded word...
 

Duke

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The problem with getting good imaging remains - the placement of designs like the Sanders and Ohm close to a wall is intended to provide a desired overall room voicing - a room Target Curve....

But what is not corrected in these approaches is the smearing of the imaging caused by the reflections from a nearby wall, arriving almost simultaneously with the initial speaker signal ...

The Sanders Sound flat electrostatic panels are highly directional both forwards and backwards, with the typical dipole null to either side. So it's often feasible to set them up such that the backwave energy's first bounce misses the "sweet spot", resulting in an abnormally long (and imo highly desirable) time delay before arriving at the ears.
 

dlaloum

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The Sanders Sound flat electrostatic panels are highly directional both forwards and backwards, with the typical dipole null to either side. So it's often feasible to set them up such that the backwave energy's first bounce misses the "sweet spot", resulting in an abnormally long (and imo highly desirable) time delay before arriving at the ears.
Similar strategy works well with Quad ESL's - the simple process of angling them in towards the listening position, redirects the rear sound, and with some care, can allow placement closer to the rear wall... putting them flat up against a rear wall is a massive no-no! (Ideally, your rear sound then bounces off the rear, then off the side wall before reaching your ears - giving it more time/distance.

But the Quads (ESL63 and later) are not a "Beamy" design - they have quite a decent spread both front and back - which means they are likely to need a bit more distance (from the rear wall) than a "beamy" design, even given the angling approach...
 

Duke

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Similar strategy works well with Quad ESL's - the simple process of angling them in towards the listening position, redirects the rear sound, and with some care, can allow placement closer to the rear wall... putting them flat up against a rear wall is a massive no-no! (Ideally, your rear sound then bounces off the rear, then off the side wall before reaching your ears - giving it more time/distance.

Yes!!

Another variation on the theme is placing dipoles very close to the side walls, but not close to the "front" wall, then toeing them in fairly aggressively. This works well with SoundLabs, which have unusually uniform radiation patterns so that probably helps. With this set-up geometry the backwave bounces off the side wall and then off the "front" wall before reaching the listening area.
 

Dennis Murphy

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I'm not sure there is any "correct" radiation pattern. Dr. Bose thought he provided it with the 901's, which were sort of omnidirectional. His calculated the ratio of direct to reflected sound in a typical concert hall (which--I know--doesn't exist) and tried to replicate that ratio with the placement of the many small drivers he used. The fallacy is that any recording of an orchestra will already have reflected sound in the mix. So you're reflecting reflections. And, of course, the arrival times won't be the same as in a concert hall. I've tried to reach a compromise with my speakers, which have close to 180 degree radiation over most of the frequency range. I personally think that sounds best for the kind of music I listen to, but I'm certainly not claiming it's "correct."
 

test1223

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Do you account the Huygens-Fresnel principle in your reasoning of reflections?
https://en.m.wikipedia.org/wiki/Huygens–Fresnel_principle
IMHO you have to take into account a pretty big surface area around the first ray model reflection point. Otherwise you don't prevent such a reflection in the real world. And second reflections are much more complicated to predict if the first reflection path is different from the ray model.
 

dlaloum

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I'm not sure there is any "correct" radiation pattern. Dr. Bose thought he provided it with the 901's, which were sort of omnidirectional. His calculated the ratio of direct to reflected sound in a typical concert hall (which--I know--doesn't exist) and tried to replicate that ratio with the placement of the many small drivers he used. The fallacy is that any recording of an orchestra will already have reflected sound in the mix. So you're reflecting reflections. And, of course, the arrival times won't be the same as in a concert hall. I've tried to reach a compromise with my speakers, which have close to 180 degree radiation over most of the frequency range. I personally think that sounds best for the kind of music I listen to, but I'm certainly not claiming it's "correct."
Interestingly - both Peter Walker of Quad and Amar Bose (of Bose) - came to a similar conclusion, that the ideal transducer/speaker, should behave as an approximation of a "Ball emitter"... a pulsing ball of sound.

Quad achieved it via delay lines in the ESL panels of the ESL63 and subsequent models, Bose achieved it via an array of speaker drivers facing different directions - but with most of them focused on reflections.

Ultimately the Quad approach seems to have been more successful in the market... and seems to works better in an Audiophile, High Fidelity sense...
 

restorer-john

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If I recall correctly... That research included almost no omni's dipoles or bipoles (I think a single lonesome electrostatic panel among around 70 different monopole boxes!)

The room was set up / designed for monopole speakers - so no surprise that the lone bipole didn't perform very well.

And yeah omni's are wide and even dispersion (by definition) - but to get the imaging / pinpoint location that you want for both music and movies, you have to use the reflections properly... and that is far more complicated with an omni than with a monopole.

If you don't include any omnis, nobody could 'prefer' them- which is a good thing because manufacturers like flat panels, not curves or spheres.
 

dlaloum

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which is a good thing because manufacturers like flat panels, not curves or spheres.
Sure but Quad worked out a way to build a flat panel, where via delay lines, the soundwave emitted behave like it is coming from a sphere / point source

So the key thing is yes the panel is flat (easier to manufacture) - but the soundwave behaves like a point source, some distance behind the speaker.

(P.S.: Peter Walker was always brilliant at providing relatively simple, elegant solutions to thorny problems!)
 

Blockader

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omni speakers have higher sound power in high frequencies than forward firing speakers. Omnis can radiate directional high frequencies with as much output as omnidirectional frequencies like 100hz in a room, as a result an omni speaker with flat on-axis response can theoretically form flat response reflections. That is not the case for conventional speakers. An omni speaker with flat on-axis response sounds significantly brighter than a forward firing speaker. Higher sound power of omni speakers can be balanced with rolling off the direct sound with same magnitude and slope where sound power of forward firing speakers start rolling off however direct sound is perceptually dominant in human perception. If direct sound is recessed, reflections can't make it sound balanced. (or if the direct sound is bright, reflections with recessed treble tonality can't make it sound right) Basically there is no way to make recordings sound balanced on omni speakers with recordings that was mixed and mastered on forward firing speakers. Especially treble is doomed to sound wrong on omni speakers.
 
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