omnidirectional loudspeakers = best design available

[DanielT]

Two Mirage Omni speakers have been measured in the anechoic chamber of Canadas NRC:

SoundStage! Measurements - Mirage OMNI 60 Loudspeakers (6/2003)

SoundStage! Measurements - Mirage Omnisat v2 FS Loudspeakers (6/2005)

Aha, well if Mirage Omni 350 had the same FR as Mirage OMNI 60, then okay. I could live with that or rather lower it from 700 Hz and below and lower the FR from 5 kHz and above. The sensitivity of the speakers would most likely not be that high, but I don't intend to play them at that high volume anyway so they probably wouldn't run out of steam with such FR fixing.

Mirage Omnisat v2 FS on the other hand. That FR is too much of a wacko roller coaster so if Mirage Omni 350's FR is similar to them they are not interesting to me.

I'll have to think about it a bit. Thanks for the links anyway.

 

[Hear Here]

ASR does not bar people reporting their experience owning or hearing gear.
In fact, it’s clear that many members appreciate not only having measurements available for gear, but user reports as well.
And we do have after all a section of the forum for people reporting their experience and impressions at audio shows. Nobody’s demanded to carry around measuring equipment when they do that.

There’s measurements available for the MBL speakers. If that’s all you need, you can make your decision as to what you think of them based on that.

Unfortunately, there aren’t blind listening test results for MBLs. So we have what we have.

Somebody who has owned them can offer their impressions of how they actually worked out in practice in their own room, which is what I have done. You are free to take it or leave it. But again other people appreciate reading somebody’s experience with such exotic loudspeakers (or other loudspeakers, they might be interested in).

I'd suggest that measurements for speakers in particular are of little value to a potential purchaser.

They need to read subjective unbiased reviews from respected reviewers and perhaps (though they won't be unbiased) opinions from owners and to listen to them at dealers or at audio shows is far more important. Even then, this should never prompt a purchase but a home demo, as speakers will sound very different depending on the room they will be working in, and to a much lesser extent to the electronics feeding them.

For what it’s worth (admittedly virtually nothing), my own opinions of the MBLs I heard at a dealer showroom were ambiguous. I liked and appreciated the principle selling point of omnis – their ability to allow good listening over a very large listening area, but I didn’t like (compared with my own speakers) their relatively poor imaging, even when sat in the prime listening position. By definition toe-in of omnis cannot help with this feature, while it is of imperative importance with most other TYPES, in particular my own chosen type – horn speakers.

Also, for what it’s worth, I found exactly the same disappointment regarding imaging when I auditioned MBL’s main rival, the German Physics omnis. A real shame as I rate imaging highly (probably higher than I should), but my room, speaker positioning and furniture layout all point to omnis as the obvious ideal.

 

[Lekha]

Just turn your speaker box to face upwards, and you'll have an omni-directional system.

 

[Vladimir Filevski]

Just turn your speaker box to face upwards, and you'll have an omni-directional system.

No, you will have not.

 

[Hear Here]

Just turn your speaker box to face upwards, and you'll have an omni-directional system.

Sadly, not that simple. Treble would be almost completely lost.

My first speaker (from mono days when omnis were common) consisted of a 10" full-range driver mounted upwards-facing in a 12" internal diameter concrete drain pipe, as per Wharfedale’s Gilbert Briggs' drawings in one of his excellent books. To achieve any decent treble, an inverted cone had to be placed above the driver to reflect the sound sideways.

 

[dlaloum]

I am far from a subjectivist, but when I first heard omnis I had to throw nearly everything I thought I understood about stereo imaging out the window. They are exactly as @MattHooper describes - somehow both spacious with well defined centre imaging. I looked earlier in this thread to get some answers, but alas there were none, only the same subjective observations that I made. Much as I would love to convince you with some psychoacoustic studies or come up with some kind of explanation why they work, I have to wave the white flag on this one. You'll just have to find someone with an omni system and go and listen.

It is also worth keeping in mind, that our ears/brain do seperate out reflections from direct sound... it requires only a small amount of time (in ms) to seperate the two, and as far as our "imaging"/positioning senses are concerned the reflections are then irrelevant.

So if you have sufficient distance between the speaker and various reflection points, the reflections then add to the sense of space, without in any way reducing the imaging.

Basically, Omni's (and their near relatives) - love SPACE.... give them room and they will do their magic.

Try and use omni's in a small constrained space, and there will be tears!

 

[MattHooper]

If there is any plausible theory, controlled A/B tests or measurements backing up your claim that omnis can deliver excellent localization stability and minimum phantom source width, I would be very interested.

I’m afraid not. At least not from me. I’m not tech-geek enough to give you what you’d like. So I presume you won’t be satisfied with the following, but FWIW..,

It is something that I have never remotely experienced, and this is in line with every theory we have about imaging and phantom source localization.

This is always interesting to me because when people say something like that, I feel like I’m living in the twilight zone. Because I’ve had so many experiences of excellent imaging with Omnis - well from MBL speakers anyway, which are the Omni I’m most familiar with.

Somewhere around 2000 I listened to the MBL 101D speakers at the home of a reviewer for the absolute sound. They were in a very small heavily treated room with close seating. Especially with the lights down it was simply the most realistic sound I’ve ever heard. If the imaging had been as vague as you seem to suggest, there’s no way it would’ve sounded realistic to me, since image palpability is quite important to me.

And that experience carries over to my having owned my MBL 121 stand mount speakers .

The problem when it comes to talking about imaging is that it’s such a subjective mental phenomenon it’s hard to get truly precise.
It’s not like we can map out in the air in front of us to how big an image is within the inch or something. So if you’re thinking in precise and I’m thinking precise, it’s hard to know for sure if our mental model is matching exactly.

I can tell you this though: what I look for in imaging is precision and Sonic density, so that a sonic images seems to be in a precise place, and a solid object moving air, not something phasey and see-through.

But I also don’t like imaging that is “ too” focussed and tight. I find a lot of systems, especially those that employ lots of toe-in to the speakers, can focus Sonic images down so tight they become artificially squeezed smaller than life, and with the sense of a harder edge than I hear in life.

So I typically have my speakers never towed directly in and often, if not facing forward, then towed in just a bit to the listening position. I’m trying to keep enough focus and precision and density, but I also want to slightly expand and soften the very edges so it sounds to me more relaxed, and natural and less mechanical.

So I don’t know if somewhere in there is to be found our difference of opinion.

Still, I kind of doubt it because again I value image precision intensity so much, and I own Thiel speakers that are known for their precision in imaging.

And then there’s my room in which I listened to the MBLs, which as I mentioned before, was redesigned with the help of an acoustician, so there’s acoustic treatment hidden in parts of the room, such as the ceiling bulkhead, the wall behind the speakers, etc. Plus, I have two different sets of two different type of curtains running on tracks around the entire room. I can therefore pull for instance, thick velvet curtains to any point in the wall or even literally cover every inch of the walls in the room. So I can go for a live sound or a dead sound or anything in between.

a couple of these photos might give you an idea of what I’m talking about in my room

With the MBL’s often and went for a a bit more control of the wall reflections. The room was a bit more on the dead side. Though sometimes I opened it up and had it more life sounding.

While I had the MBLs I had something like seven or eight other pairs of speakers cycled through my room (including audio physic, Thiels, Harbeth, Waveform, Hales and others) so I could compare all of them.

All I can say is that to my ear the MBLs placed images the same way those other speakers did, and with similar precision.
Again, I wouldn’t be satisfied with diffuse Sonic images which gets away from what I want in terms of Sonic realism. And when I compared the sound of the live guitar to the recorded version, the MBL’s imaged like the real guitar. Not to mention I had quite a number of visitors feel practically spooked by the realism of the sound from the MBL’s, including the human voice “ it sounds like somebody’s speaking right in front of me” … and I think that an unrealistically diffuse image would’ve worked against that. Instead of the MBL’s could produce a human voice very much like a real person in front of me.

Another thing that arises doubts in me, is people claiming that they enjoyed classical music on such a setup. The deterioration of localization stability, localization blur, contradictive room reverb patterns (like ´musicians are playing in my room ´sort of reverb), overly distant presentation lacking proximity and attack, would make me feel that no-one who is listening to classical music live or recording such concerts, would be really satisfied with the presentation I know from several omnis.

OK, well at least it seems I’m in good company with Floyd Toole in finding classical music well served by omnidirectional loudspeakers.

The MBL speakers reacted essentially to my manipulation of room acoustics the way all my other speakers do. If I open up reflections and make the room more reflective there could be more of a “ live” sound. Though as tool points out, recorded reverb characteristics, still dominate.

But if I carefully closed down some of the reflectivity of the room, then I would reach a point where it would feel like the space of the room I’m in merged beautifully with the recorded space. So it no longer sounded like two separate spaces the room I’m in and some porthole opening up to a recorded space, but like I’m sharing one big space.
And that space would be the one depicted on the recording, much less in my room.
And so I could feel transported to the space of the recording quite convincingly.
And that worked absolutely beautifully for the sense of hearing a symphony Orchestra with a sensation of hearing into the space they were playing.

(I’d also mentioned that I occasionally tried the MBL’s for L/R duty in my home theatre set up, and in movies like Jurassic Park night scenes full of ambiance and insects, etc. The sense of a large acoustic space - the forest - was absolutely amazing. It was better than just my regular surround. There was a hair raising on arms sensation like the air in front of me had changed to that of the forest in the movie.

My I ask which kind of recording venue was involved and how you captured its natural reverb?

Some of the recordings, eg the recording of my acoustic guitar, were done in the very same listening room. I got close enough to the guitar for a natural sound balance, not too close, but also picked up a little bit of the room as well. But ultimately that didn’t matter, because in playback is still sounded just like a guitar playing in the same room (I brought that up to Floyd and he said that would be predictable).

Cheers.

 

[MattHooper]

Try and use omni's in a small constrained space, and there will be tears!

Certainly no tears for me. My Omni performed in my 15’ x 13 ‘ room as well as I’ve ever heard Omnis.

I found when I got the speaker position and listener position dialled in as as well as the reflectivity of the room, I got all the astonishing performance characteristic of an Omni.

 

[Newman]

I'd suggest that measurements for speakers in particular are of little value to a potential purchaser.

They need to read subjective unbiased reviews from respected reviewers and perhaps (though they won't be unbiased) opinions from owners and to listen to them at dealers or at audio shows is far more important. Even then, this should never prompt a purchase but a home demo, as speakers will sound very different depending on the room they will be working in, and to a much lesser extent to the electronics feeding them.
…

The above statements from beginning to end represent the very antithesis of reality and are part of the reason for ASR existing.

The sooner you start to unlearn every component of your above statements, the better.

 

[Newman]

Sounds great to many other people. Your experience is not more important, nor truer than others.

Or to be more precise, his experience is of no importance, and has no truth, just like the others. At least, as far as communicating it to readers on a forum is concerned.

 

[Lekha]

Sadly, not that simple. Treble would be almost completely lost.

That depends on the type of tweeters you have and, primarily, on your own hearing. Additionally, the type of soffit you have plays a role. If your room height is just 8 feet, that could also pose a problem.

 

[Arindal]

The problem when it comes to talking about imaging is that it’s such a subjective mental phenomenon it’s hard to get truly precise.

I agree that imaging quality, particularly localization width/precision, is hard to describe and evaluate without a reference.

The usual method is to provide a reference in direct comparison, either by the help of a true center channel helping to evaluate the phantom center properties, or with the help of an optimum localization nearfield setup as a reference.

If you could perform such a comparison with a reliable reference for an optimum of localization precision and describe the differences, it would be already all an estimation.

But I also don’t like imaging that is “ too” focussed and tight. I find a lot of systems, especially those that employ lots of toe-in to the speakers, can focus Sonic images down so tight they become artificially squeezed smaller than life, and with the sense of a harder edge than I hear in life.

In this case we have a problem with general definition of sound quality. I very well understand what you mean by phantom sources appearing as ´too focused and tight´, but from a perspective of recording and monitoring sound, this is simply what was intended by the mixing engineers. That is particularly the case with recordings employing intensity-panned, de facto monaural sources, adding just artificial or decorrelated reverb. No matter the reproduction system, if it is anywhere near accurate imaging, it will always reveal the aforementioned properties of mono/close-mic´ed sources, which you might find annoying.

The attempt to change this by adding a certain degree of blur and additional reverb in the listening room is understandable, and in a way legitimate. My experience is, though, that this comes at a steep price, the moment any natural reverb is contained in the recording. To my ears, it will always make the latter unlistenable and highly annoying, no matter what. If you listen to recordings which contain natural reverb on a proper system, there is never such thing like ´too narrow/tight phantom sources´.

The best compromise I have heard so far was a far-field setup with speakers which were specifically designed for greater listening distances while retaining both localization stability and reduced proximity of ´dry´ sources. These are rare, but it might be worth a try.

Some of the recordings, eg the recording of my acoustic guitar, were done in the very same listening room. I got close enough to the guitar for a natural sound balance, not too close, but also picked up a little bit of the room as well. But ultimately that didn’t matter, because in playback is still sounded just like a guitar playing in the same room

That is to be expected as the reverb patterns our ears are getting from the recording and those created in the listening room, are the same. While this is an interesting experiment and might subjectively help with very dry recordings, it almost always leads to significant contradictions with recordings containing a natural reverb pattern.

As mentioned, I prefer to check that in a listening test using either recordings from concert venues I know well, or such with very distinct or dominant reverb characteristics. Try one of the Jordi Savall recordings made by AliaVox in Cardona.

 

[dlaloum]

Certainly no tears for me. My Omni performed in my 15’ x 13 ‘ room as well as I’ve ever heard Omnis.

I found when I got the speaker position and listener position dialled in as as well as the reflectivity of the room, I got all the astonishing performance characteristic of an Omni.

Sure - but that was a heavily treated room... It might have been more awkward without the treatment?

 

[ShadowFiend]

While this is an interesting experiment and might subjectively help with very dry recordings, it almost always leads to significant contradictions with recordings containing a natural reverb pattern.

Problem is that the majority of recordings, at least in my favorite classical music, are dry or they contain mostly non-natural reverb pattern. That is due to multi-miked technique and perspective of mixing/mastering engineer. With those kind of recordings, if I listen on normal box speaker, even with high quality one, I never experience the density of sound in 3D space like the one in concert, while the high quality omni speakers can do that. Of course, like you said, the omnidirectional one does not produce the pin-point imaging, but that kind of pin-point imaging is only existed when you sit in or very near stage in the concert hall, which is not something we normally like and sit in the concert hall.

Of course, for recording with very natural reverb like AliaVox then the omni is possibly too much for some people, but as a one who heard thousand of recordings, they are minority with a tiny number.

The cycle of confusion is there, and it will not go away. So I don't think any kind of one-side-fit-all approach will work to all recordings unless you don't care about soundstage. My approach is multiple system, one high reverb system (omni/dipole) and high directivity monopole (big horn or cardioid)

 

[Hear Here]

I can tell you this though: what I look for in imaging is precision and Sonic density, so that a sonic images seems to be in a precise place, and a solid object moving air, not something phasey and see-through.

But I also don’t like imaging that is “ too” focussed and tight. I find a lot of systems, especially those that employ lots of toe-in to the speakers, can focus Sonic images down so tight they become artificially squeezed smaller than life, and with the sense of a harder edge than I hear in life.

So I typically have my speakers never towed directly in and often, if not facing forward, then towed in just a bit to the listening position. I’m trying to keep enough focus and precision and density, but I also want to slightly expand and soften the very edges so it sounds to me more relaxed, and natural and less mechanical.

I agree with you about the importance of accurate imaging. It's possibly the biggest contribution to the impressiion of a live performance. But the last paragraph in the clip I've quoted confuses me. You talk about how much toe-in you apply, but surely with omnis, toe-in is ineffective in terms of imaging? You could fully rotate an omni and the sound should be idential at the listening position. Or were you talking about other types of speakers - your Theils perhaps? My own speakers require a very accurate toe-in setting to achieve their incredible imaging and it was this factor that I couldn't replicate with either of the omni systems I listened to at dealer showrooms. It would be good to get a pair on loan in my room, as I'm sure they'd be better at imaging here than the showroom.

 

[Arindal]

Problem is that the majority of recordings, at least in my favorite classical music, are dry or they contain mostly non-natural reverb pattern. That is due to multi-miked technique and perspective of mixing/mastering engineer.

That would be very unusual and I doubt it exists in mass quantities. A majority of classical recordings is done with a main microphone arrangement capturing an overall sonic picture of the reverb in the room, which automatically leads to a natural reverb pattern. Adding signals of several spot microphones does improve other aspects of the mix, such as clarity, balance between instruments and localization stability, but does not change the general picture of natural reverb.

Could you name a few popular examples of classical recordings containing no natural reverb please? And I do not mean recordings specifically done for TV broadcast or cinema.

I never experience the density of sound in 3D space like the one in concert, while the high quality omni speakers can do that.

You cannot experience the ´density of 3D space´, because such cannot be captured with two-channel stereo nor can it be reproduced with omnis. If you want a more realistic three-dimensional ambience, go for immersive recordings.

but that kind of pin-point imaging is only existed when you sit in or very near stage in the concert hall, which is not something we normally like and sit in the concert hall.

I do like that. And I know several concert halls, particularly opera houses and more modern concert venues, which deliver an accurate localization for a considerable number of seats even beyond row #10.

The other question is what the mixing engineer had in mind when composing the mix. It is a subjective decision, naturally, but I would guess the majority of recording engineers aim for a balance between localization and ambience with a tendency to highlight the former. Something you would usually find on a central seat in 4th to 6th row in average concert hall. The ´perspective of the conductor´ in Karajan-style or dry ambience aesthetics, like preferred by Carl Orff and his contemporaries, are seriously out of fashion, me thinks.

for recording with very natural reverb like AliaVox then the omni is possibly too much for some people, but as a one who heard thousand of recordings, they are minority with a tiny number.

Having heard tens of thousands and participated in the recording and production of a significant number of classical productions, I have to disagree.

So I don't think any kind of one-side-fit-all approach will work to all recordings unless you don't care about soundstage.

It requires a bit more than just setting up flat-measuring speakers and dampening the room, but it is doable. You have to take early reflections into account and opt for constant directivity speakers, preferably coaxial ones suitable for far-field operation, and carefully set them up at a greater listening distance. The result can work with both very dry pop and electronic recordings and a vast variety of recordings containing natural reverb, keeping reasonable proximity, localization stability and depth-of-field for all.

I do care for soundstage a lot, localization, ambience and proximity alike, it is my priority when choosing or setting up speakers. I can tell you: an excellent balance is achieveable. Maybe not as diffuse and ambient as with omnis, maybe intensity-panned monaural signals sounding to a certain degree, well monaural, narrow and direct, but not annoying.

 

[DanielT]

Those of you who have experience with omnis and home theater. What is the difference between two-channel stereo with two Omni speakers vs. let's say a five or more channel setup. I mean if you run the music through a setup like this:

What's the difference from omnis? With that home theater system, there should be omni dispersion sound,.... or not? Or am I thinking wrong now? Am I missing something?

 

[dlaloum]

Those of you who have experience with omnis and home theater. What is the difference between two-channel stereo with two Omni speakers vs. let's say a five or more channel setup. I mean if you run the music through a setup like this:
View attachment 461943
What's the difference from omnis? With that home theater system, there should be omni dispersion sound,.... or not? Or am I thinking wrong now? Am I missing something?

You need to visualise what happens to the reflected sound that is coming off any of those speakers that are Omnis - if the resulting reflection is within around 1 to 10ms of the direct sound, it will affect localisation (ie: degrade it) - if the reflection arrives more than 10ms after the direct sound, it adds to the sense of space / ambiance (our own minds automatic filter cuts in!)

So wherever a speaker is close enough to the wall, for the reflected soundwave to arrive within that time... it becomes a problem (unless absorbed or dispersed... "treated")

You need it to travel approximately 1.7m or so (2m is usually pretty safe) to the reflecting surface (so the total path from speaker to reflective surface and back to speaker should be more than 3.5m... ie: 10ms)

That means that without treatment, the room needs to be substantially bigger to allow that space.

Alternatives include angled panels/walls to ensure that the soundwave is reflected at an angle away from the listening seat, by the time it hits another surface and bounces back into the listening area, the path will then have increased to beyond the critical 10ms.

Think of all hard surfaces as sonic mirrors....

Bookshelves full of books, will absorb some frequencies, and reflect a lot in various directions due to the books ... often an excellent (and WAF friendly!) treatment.... the eggcarton style waffle treatment, break the sound up and reflect it in various directions - so not much is left to reflect back directly to the listening area.... Curtains can work very well at the key midrange and higher frequencies, but tend to be transparent in the bass...

A multi channel system, vs a stereo omni system, are not really comparable - the multi channel setup will attempt to emulate ambiance and space via various algorhythms.... software - and results will vary depending on the software.

Omni's will achieve a sense of space/ambiance, mechanically / acoustically (so to speak) - in a fixed manner, but one that is "natural" - and often sounds that way to our ears.

Software solutions - surround - range from good, to horrible.... Omni's due to the naturalness of the way they broadcast sound, tend to start off from a higher base than artificial setups.

Yamaha spent buckets of money researching the acoustics of many of the worlds top performing spaces - and then incorporated that into various surround modes for their processors. First came out in the mid 1980's (so been around a while!)

Others incorporated their own versions of such effects, and most AVR/AVP's have various such affects available. (mine has "Orchestra" and "unplugged" - the first emulating a large orchestral hall, and the latter a small Jazz space - purportedly)

 

[ShadowFiend]

That would be very unusual and I doubt it exists in mass quantities. A majority of classical recordings is done with a main microphone arrangement capturing an overall sonic picture of the reverb in the room, which automatically leads to a natural reverb pattern. Adding signals of several spot microphones does improve other aspects of the mix, such as clarity, balance between instruments and localization stability, but does not change the general picture of natural reverb.

I know this technique, but from my experience, it does not translate well in the recordings. It will either too little to my taste or too too much (in case of LSO Live). Of course, the multi-miked technique is better for clarity and SNR, but the coherent of sound is in the mercy of sound engineer.

You cannot experience the ´density of 3D space´, because such cannot be captured with two-channel stereo nor can it be reproduced with omnis. If you want a more realistic three-dimensional ambience, go for immersive recordings.

Yes, stereo in general can not fully captured the density of 3D space, but omni/dipole is the closest method to achieve this goal with stereo/mono source.
I have many immersive recordings, and while I like the sound of them, only a few of them are interested in terms of music quality. My music collection ranges from 1930 until now, and I rather listen to those mono/stereo recordings than the immersive recordings with inferior music quality, according to my taste of course. So, my goal is to get the best and most realistic sound from those source, not sonic perfection only.

I do like that. And I know several concert halls, particularly opera houses and more modern concert venues, which deliver an accurate localization for a considerable number of seats even beyond row #10.

Yes accurate but not pin-point accurate like in recordings where you hear oboe is very separated from flutes, or sound from violin section is only from a very small area in the sound field.

The other question is what the mixing engineer had in mind when composing the mix. It is a subjective decision, naturally, but I would guess the majority of recording engineers aim for a balance between localization and ambience with a tendency to highlight the former.

yes, that is my observation too. But for me, they put too much effort on the former, it make the result unnatural for me. And omni is a good fix for that with stereo source.

It requires a bit more than just setting up flat-measuring speakers and dampening the room, but it is doable. You have to take early reflections into account and opt for constant directivity speakers, preferably coaxial ones suitable for far-field operation, and carefully set them up at a greater listening distance. The result can work with both very dry pop and electronic recordings and a vast variety of recordings containing natural reverb, keeping reasonable proximity, localization stability and depth-of-field for all.

I do care for soundstage a lot, localization, ambience and proximity alike, it is my priority when choosing or setting up speakers. I can tell you: an excellent balance is achieveable. Maybe not as diffuse and ambient as with omnis, maybe intensity-panned monaural signals sounding to a certain degree, well monaural, narrow and direct, but not annoying.

In many point, I agree with you about early reflection and constant directivity speakers. But good omni speakers like the MBL ones in big room are exactly like that. And coax speakers are not constant directivity, they are omni until 150Hz, then the transient region between 150Hz-500Hz and only constant directivity again at 500Hz up, and narrow down gain past 10kHz.

I tried the one side fit all approach with my old Revel and Audio Physic Virgo for quite sometimes but never feel satisfied. As an electronics engineer with embedded background, in my opinion, the specific tools are better than the universal tools for a specific task.

 

[DanielT]

You need to visualise what happens to the reflected sound that is coming off any of those speakers that are Omnis - if the resulting reflection is within around 1 to 10ms of the direct sound, it will affect localisation (ie: degrade it) - if the reflection arrives more than 10ms after the direct sound, it adds to the sense of space / ambiance (our own minds automatic filter cuts in!)

So wherever a speaker is close enough to the wall, for the reflected soundwave to arrive within that time... it becomes a problem (unless absorbed or dispersed... "treated")

You need it to travel approximately 1.7m or so (2m is usually pretty safe) to the reflecting surface (so the total path from speaker to reflective surface and back to speaker should be more than 3.5m... ie: 10ms)

That means that without treatment, the room needs to be substantially bigger to allow that space.

Alternatives include angled panels/walls to ensure that the soundwave is reflected at an angle away from the listening seat, by the time it hits another surface and bounces back into the listening area, the path will then have increased to beyond the critical 10ms.

Think of all hard surfaces as sonic mirrors....

Bookshelves full of books, will absorb some frequencies, and reflect a lot in various directions due to the books ... often an excellent (and WAF friendly!) treatment.... the eggcarton style waffle treatment, break the sound up and reflect it in various directions - so not much is left to reflect back directly to the listening area.... Curtains can work very well at the key midrange and higher frequencies, but tend to be transparent in the bass...

A multi channel system, vs a stereo omni system, are not really comparable - the multi channel setup will attempt to emulate ambiance and space via various algorhythms.... software - and results will vary depending on the software.

Omni's will achieve a sense of space/ambiance, mechanically / acoustically (so to speak) - in a fixed manner, but one that is "natural" - and often sounds that way to our ears.

Software solutions - surround - range from good, to horrible.... Omni's due to the naturalness of the way they broadcast sound, tend to start off from a higher base than artificial setups.

Yamaha spent buckets of money researching the acoustics of many of the worlds top performing spaces - and then incorporated that into various surround modes for their processors. First came out in the mid 1980's (so been around a while!)

Others incorporated their own versions of such effects, and most AVR/AVP's have various such affects available. (mine has "Orchestra" and "unplugged" - the first emulating a large orchestral hall, and the latter a small Jazz space - purportedly)

Okay, but don't home theater amplifiers have the ability to set time delay for each channel? I don't know about that because I'm not a home theater guy.

Besides that, omnis have hardly any, or very little, sound directed directly at the listener. Isn't that the whole point of omnis? With that, the largest amount of sound will bounce around the room with the largest energy from the first reflex that reaches the listener? Then at different arrival times. In this way, if my assumption is correct, omnis should be much more room-dependent than "traditional" speakers. I mean the difference between two different rooms, with the same amount of furniture and carpeting and so on, where one room is square and the other rectangular.Then a bigger difference in sound with omnis compared to a narrow dispersion speaker with more energy directed straight ahead (without reflections) at the listener.
Which is preferable I guess is mostly a matter of taste and preference.

When I think about it, I've had omni-like speakers. Carlsson speakers, Sonab OA-5 type2. Sweden's best-selling speakers of all time. In any case, a rather pointless listening experience because the old Philips 9710 bass driver was worn out after fifty years of listening. The crossover and the tweeters had probably seen their best days too. If they had been in new condition, who knows. I might have liked them/the sound.

Sonab OA-5 Type 2 - CarlssonPlanet

Sonab OA-5 is, without competition, the most widespread speaker in Sweden, ever. In the end of the sixties everybody in Sweden wanted a pair of the strange and wellsounding speakers. The standing matchbox design struck well with the pure design trends and the omnidirectional sound suited the...

carlssonplanet.com

The white ones in the video are OA-5. By the way the Marantz receiver in the video is placed on two OA-5 speakers. There you can see their downward-facing port. In front of the ports, he has placed the speaker grilles that are normally located on top of the speakers.