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Omnidirectional loudspeakers ?

Purité Audio

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#1
Omni’s, I have heard MBLs,Audio Physiks at Munich, Beolab 90 has an omni mode which I found a little disorientating, Shahinians of various hues, although they aren’t true omni’s , are they just toys or do they have any merit.
Did Toole/Olive/Harman measure any omni’s?
Keith
 

sergeauckland

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#3
I would too. A few years ago, I built a pair of omnis and demonstrated them at the UK's Scalford show.

Subjectively, they lacked precise stereo imaging, but equally, didn't have the stereo 'sweet spot' that conventional forward-facing loudspeakers have.

The frequency response measurements I took were pretty awful, but that may have had something to do with the drive units I used, which were a nominally full-range driver with whizzer cone. Used conventionally, that driver was very coloured, as are pretty much all drivers with a whizzer cone that I've seen, but possibly by virtue of the reflector cone that converted the upwards firing driver to horizontal omni, it sounded less coloured as an omni.

I think that omnis have the benefit of driving the room more evenly, so provided the driver(s) used are very good, results should also be as good as the room allows, but, with the proviso that stereo imaging is less precise.....much like real life really...... Ideal for naturally recorded classical music where the audience normally sit in the reverberant field of a concert hall, possibly less good for rock/pop etc which is assembled from bits and pieces recorded at different times in different places.

At a classical concert, if one listens with eyes open, one can normally identify where each instrument is playing from, but with eyes closed, it is much more diffuse, and lacks precise positioning. At home with stereo, lacking the visual clues of musicians' positions, I find the precise imaging I get from stereo to be helpful.



S.
 

Blumlein 88

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#4
I think we should ask. @Floyd Toole did Harman test omni speakers against others?

My guess is the omni is wrong for the model of what makes a good sounding speaker in Harman's testing. But maybe they've tested them all the same. I do seem to remember mention of testing the Mirage bipolar M1 and M3. I think over much of the frequency range those were pretty much omnidirectional.

Of course I'm still trying to figure out why panel speakers do so poorly at Harman, but sound so good to me.
 

Ron Texas

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#5
I think we should ask. @Floyd Toole did Harman test omni speakers against others?

My guess is the omni is wrong for the model of what makes a good sounding speaker in Harman's testing. But maybe they've tested them all the same. I do seem to remember mention of testing the Mirage bipolar M1 and M3. I think over much of the frequency range those were pretty much omnidirectional.

Of course I'm still trying to figure out why panel speakers do so poorly at Harman, but sound so good to me.
Perhaps the answer is there is no accounting for taste. One of the most memorable in store listening experiences I ever had was with the old Magnepan 8 panel setup.
 

Blumlein 88

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#6
Perhaps the answer is there is no accounting for taste. One of the most memorable in store listening experiences I ever had was with the old Magnepan 8 panel setup.
A friend with those once told me, "the 2nd happiest day of my life was getting these Magnepan speakers. I wanted them so bad for so long. The happiest day of my life will be when I sale them." He had them for sale at the time.
 

Ron Texas

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#7
A friend with those once told me, "the 2nd happiest day of my life was getting these Magnepan speakers. I wanted them so bad for so long. The happiest day of my life will be when I sale them." He had them for sale at the time.
Sounds like what they say about boats. People love Maggies. For whatever reason there are ML electrostatics in every Magnolia Design store making them the most available panel speaker in the USA. However, Harman has done some great research and their products show it.

Just because there is a statistically significant preference does not mean everyone has that preference.
 

Blumlein 88

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#9
My understanding (perhaps incorrect) is that Harman’s testing showed that people preferred speakers with an even off-axis frequency response.
Omni would be the best for this wouldn’t it?
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.
1549236576096.png


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.

1549236677362.png
 

MattHooper

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#10
I've seen Floyd Tool mention testing some Mirage speakers that were "effectively omnis" and they blind tested very well.

Anecdotally: I've always loved the sound of MBL speakers and at one point managed to pick up a pair of their stand mounted version, the 121, which use the same omni mid and tweeter as the large 101 speakers. I still own them (as well as other speakers).

They are really something. The imaging really is like no other speaker in my experience in terms of creating a 3 dimensional sensation and just "entering" the recording. I didn't find it hard at all to set them up to get quite good precise imaging (then again, I have a fairly well damped room).
It's not as precise as my Thiel speakers, but in no way do I find them "imprecise" relative to many other speakers.

I also find the tonality of these speakers - that is the realism of their timbral reproduction - constantly amazing. To my ears, most reproduced sound is homogonized, especially through most systems. Once I hear drum cymbals, or a sax or whatever played through a speaker a few times I pretty much know what those instruments will sound like from then on. The MBLs give more "surprising" variety to the timbre of instruments than almost any speaker I've listened to. The upper frequencies are more natural than any cone/box speaker I've ever heard: sounding less like "tweeters" and more like the real instruments, especially drum cymbals and tiny details.

I have recordings I made of familiar instruments and voices - e.g. my acoustic guitar, my wife and son's speaking voice, my sons practicing sax and trombone etc. The MBLs can produce a fairly amazing sensation of those instruments being played in the room. And from just outside the listening room the illusion is even greater. It really does sound *almost* exactly like someone is playing an acoustic guitar, or a sax in the room.
I've actually fooled a couple of people who thought my son was practicing in the room. How much of this is due to the omnidirectionality vs other aspects of the design I don't know, but it sure is fun!
 

RayDunzl

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#11

jhaider

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#12
Some time ago, inspired by an enthusiastic Peter Azcel review of an Xbox brand speaker with a coaxial driver firing at an upwards angle as nearfield speakers, I bought a pair of Mirage OMD-5 speakers of the same design but larger and much nicer looking. I use them at work right now, powered by an ELAC integrated DAC-amp and with a small subwoofer. They sound pretty good playing NPR talk, podcasts, and audiobooks. They look even better. They've veneered with a unique burled birch and finished with a high gloss. I've attached a CEA-2034 listening window response from when I measured these in 2017. The measurements were taken indoors, so not as clean as chamber or outdoor measurements.
Screen Shot 2019-02-03 at 11.49.15 PM.png
 

Theo

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#13
The response of the omni speakers is very dependent on the room itself. Obviously, as Dr. Toole said, the brain is able to process through room reflections. I suppose that the owner of the room + speakers learn how to "process" his system, then gets used to the sound and is very comfortable with it (as long as the speaker response is ok).:cool:
I'm wondering if someone used to another room acoustics/directional speakers would feel the same when listening to the owner's system?
 

amirm

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#15
One good content the MBLs sound really good. The issue I have is that everything played through them has the same signature, diffused soundstage. Not every piece of content should sound that way.
 

sergeauckland

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#19
Conventional wisdom, which I think makes sense, is that omnis best suit music recorded in a natural acoustic environment e.g. orchestral music - basically stuff that isn’t close-mic’d, pan-potted, etc.
Based on my limited experience of omnis, just the ones I built as an experiment, I agree that the main benefit of omnis is where a sharp detailed stereo image is either undesired, or impractical, as listeners can't be seated in the 'sweet spot', or listeners like to move around rather than be fixed in one place. Classical music lends itself best to an omni presentation where the more diffused stereo image is not necessarily a bad thing.

One issue that affects omnis more than conventional 'speakers is that listeners are then in the reverberant field and consequently the local acoustics of the listening room makes a bigger difference to the perceived sound. It does have the advantage that the power response and anechoic frequency response are pretty much the same, although in the case of omnis, the anechoic response is a bit of a nonsense.

I would really like to hear a pair of omnis with a flat frequency response, as mine had anything but a flat response, and even the expensive MBLs seem to have a somewhat ragged HF response, and if they can't manage flat at that price, I question what it would take to better it.

S.
 

MattHooper

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#20
One good content the MBLs sound really good. The issue I have is that everything played through them has the same signature, diffused soundstage. Not every piece of content should sound that way.
Though I don't discount what you actually heard when you listend to MBLs, that doesn't really match my experience in owning them.

If you let room reflections go wild, then yes I can see the "diffuse soundstage" criticism. But my room is a good sounding room with a nice balance of reflective and absorptive material (designed with an acoustician), and I can modulate the absorption to some degree (additional moveable curtains).

I tend to like a fairly close seating position, 6 feet or so, sometimes 7, from the MBL monitors, so I'm getting somewhat more direct sound than probably many other set ups.

I find they image wonderfully and with a great sense of "surprise" from one track to the next. One track can have close, direct, dry sound hanging right there, well focused in front of me, the next can just expand outside the apparent boundaries of my room.

I'll never forget the first time, almost 2 decades ago, I heard the bigger MBl 101 speakers in a nearfield set up at someone's home, in a dubiously small room. It remains the single most realistic reproduced sound I've ever heard.

As I mentioned earlier: it's not that I'm unfamiliar with other speaker designs. I've owned many and usually have a handful around (currently: Thiel, Spendor, MBL, Hales, Waveform...all of which have their virtues...and I bet a good number of memters here own multiple sets of speakers).
 
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