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omnidirectional loudspeakers = best design available

Zvu

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It is at low frequencies.

"It can be seen that the loudspeaker becomes increasingly more directional above 1kHz in the frontal hemisphere as it transitions from omni-directional through cardoid to dipole radiation."
https://www.linkwitzlab.com/IJAETv2n2a2-Linkwitz-1.pdf
"Increasingly more directional" doesn't mean it is not directional bellow 1000Hz.

In that PDF there are front and rear measurements od LXmini from which you can see that it is omni up to about 200-300Hz. It gets cardioid pattern from 700Hz up to 1000Hz, and then gets dipole radiation pattern above 1200Hz.

Every loudspeaker is omnidirectional at low frequencies. This thread is not about those loudspeakers.
 
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Zvu

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The OP explicitly mentioned LX-minis in the initial message of this thread. So yes, this thread is about them ...
They are on the list by mistake. The thread is about "Omnidirectional loudspeakers = best design available" which LXmini are not.

Or am I mistaken ???
 

bluefuzz

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Or am I mistaken ???
Well, only OP can say what he really had in mind but he seems to have disappeared from the thread. I assume he included LX-minis and Linkwitz other designs as they have many of the qualities of 'true' omnis. My LX-minis are certainly more 'omni-like' than 'box-like' ...
 

JohnBooty

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Euphonic but inaccurate sound IME.
I rather like it nevertheless but high fidelity to the recording? No.
I don't have 1% of the knowledge of the professionals on this forum, but this is my thinking too. I think "exotic" designs like omnis or even planars like Magnepans might be best for a good second or third system?

If/when I invest the money in another system, I've been thinking of going with LXMinis (yes, they're not "true" omnis) as they're relatively affordable and would be relatively easy to haul out and/or stow away. Ohm's speakers would have a similarly compact footprint, but would cost several times as much.

I'm not sure if I'll ever be ready to commit that much to a secondary system though. Hopefully I can find a way to audition some in person once we've made it through this COVID business.

Apparently some Bose speaker/s had a good reputation like that...?
The Bose 901, right? http://noaudiophile.com/Bose_901/

I've never heard them but they have a lot in common with omnis since they operate mainly by reflected, indirect sound. Their rep is similar to that of omnis. You don't get precise imaging or really what we would call "correct" sound in any objective way, but many say they can be a lot of fun.

Anecdotally these seem to hold their value really well. You can buy a pair on Craigslist and when you get tired of it... turn around and sell it for the same exact price a year later hahaha. Net cost to you... $0. :)
 
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mkawa

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i humbly add the axiom audio LFR series. these are floorstanding front/rear bipole designs with hybrid active/passive crossovers (active front/back, passive vertical). they also have a newer model that uses fully active crossovers. i have LFR1100s, which are a bipolar design based on their M100 unipolar floorstanders. the effect isn't towards surround sound but ridiculously wide sweet spot and room filling sound for larger spaces -- mine is 500sqft with lots of weird corners and doors.

available integrated with their own class D amplifier series for fewer boxes.
 

Zvu

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@bluefuzz I've never listened LXmini with some omni-speaker in the same room to be able to make a comparison of that sort. I have heard of Duevel and listened smaller MBL model. There ends my immediate experience with true omni speakers listed by the op.
 

oivavoi

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They are on the list by mistake. The thread is about "Omnidirectional loudspeakers = best design available" which LXmini are not.

Or am I mistaken ???
I'm pretty sure the OP must have meant the Linkwitz Plutos, which were in fact almost-omni. Linkwitz went in a less omni direction with the minis.
https://www.linkwitzlab.com/Pluto/Pluto-2.1.htm
 

anmpr1

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What is the optimal number of omni speakers to have in a room?
If you ask a lot of people here it would be none. If your musical taste runs from Arturo Toscanini to Wilhelm Furtwangler, you could probably get away with just one. In the middle of your listening room. Or possibly in a corner.

In fact, I'm thinking that a single omni might actually make those old mono recordings 'come alive' in a good way. But since I don't have omnis it's something I'll never know for sure.
 

Duke

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i humbly add the axiom audio LFR series. these are floorstanding front/rear bipole designs... the effect isn't towards surround sound but ridiculously wide sweet spot and room filling sound for larger spaces.
Imo bipolars are more practical than omnis for three reasons:

First, given placement several feet out into the room, the contribution of the bipolar's rear-firing energy ONLY increases the energy in the later-onset reflections. It will have no more early reflections than a conventional speaker, but will have significantly increased later-arriving reverberant energy, which imo is desirable. The reduced sidewall-directed energy (relative to an omni) allows bipolars to perform well in narrower rooms than omnis.

Second, since bipolars are somewhat directional, they can be aimed. And when they are toed-in, the rear-firing drivers are toed-out, which correspondingly increases their reflection path lengths (which is desirable).

Third, bipoles inherently have a bit higher direct-to-reflected energy ratio than omnis, and imo in most rooms bipolars are closer to "ideal" in this regard.

Bipolars share this desirable trait with omnis: Their reverberant sound is spectrally very similar to their direct sound. In fact the designer could theoretically even tweak the response of the rear-firing drivers to better accomplish this.

Out of all the loudspeakers tested at the NRC in Canada during Floyd Toole's tenure there, his first choice was the bipolar Mirage M1 for his large home listening room (a combination living room/dining room with a somewhat high reverberation time of about 1/2 second). I'd like to quote from the third edition of his book, page 190. Those of you who dismiss all subjective impressions as inherently untrustworthy, fire up your keyboards:

"Over the years, a parade of loudspeakers went through that room, and all disappointed. The room was an unforgiving critic of loudspeakers in which the direct and reflected sounds exhibited different spectra, and conventional forward-firing loudspeakers drew attention to themselves... Then, in 1989, a new loudspeaker came on the scene: The almost omnidirectional , bidirectional-in-phase "bipolar" Mirage M1. They performed well in double-blind listening tests in the small NRC room, and also in this large one. They simply "became" the orchestra. " [emphasis Duke's]

Note that dipole speakers share many of the same attributes of a good bipole, only with reduced early same-side-wall interaction (which imo is desirable).

I have been involved with bipoles, dipoles, and other polydirectionals for over thirty years, along with monopole loudspeakers. Some years ago I wrote an article for an online magazine about a bipolar design concept I was using. At the time I didn't realize how close this was to what Mirage was doing in the M-1, as I had never seen the back side of an M-1 with the grille removed... the major difference turned out to be that my patterns were narrower:

The Controlled-Pattern Offset Bipole Loudspeaker (hifizine.com)
 
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bigguyca

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There is at least one instance where a true omni will satisfy the requirements of reproducing a recording naturally. A percussion instrument recorded in an open (anechoic) space. Take the kettle drum. It radiates equal sound within a 360 degree space. With no reflections, a microphone will pick up an equal signal regardless of placement around the drum.

Reproducing the signal in a very large space (say if you lived in Biltmore or Windsor castle) a single omni in the center of the room would essentially recreate the drum's sound, and would do so regardless of listening position. You could walk around the speaker like you were walking around the actual drum, and hear the same sound. You couldn't do that with a direct radiator, because once you got off-axis the sound would change.

So, if your listening tastes run to single (or a combination of closely spaced) percussion, then the omni would be the best bet, if you liked to walk around the room while listening.

A kettle drum is far from a true omni.

The Physics of Kettledrums (purdue.edu)
 

krabapple

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The local dealer at the time.
LOL. well....

The actual owner's manual included both floor and ceiling mount diagrams for 'best results'. It didn't recommending one over the other. (I tried both.)
 

EJ3

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LOL. well....

The actual owner's manual included both floor and ceiling mount diagrams for 'best results'. It didn't recommending one over the other. (I tried both.)
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.
 

nerdoldnerdith

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What I consider to be an omnidirectional speaker is very simple: the speaker must radiate sound evenly in every direction at every frequency. This excludes bipoles, dipoles, line sources, so-called "omnis" like the Ohm Walsh that have tweeters pointed toward the listener, and speakers with multiple drivers pointed every which way like the Beolab 90. The idea is pretty simple, but engineering such a thing and its practicality are another thing. I would suspect that is why we don't see very many of them.

I would say that the Morrison Audio speakers fulfill this omnidirectional criterion the best, given that they have perfect 360° horizontal directivity and perfect 180° vertical directivity. With an active crossover they can be EQ'd +-2dB from about 34Hz to 20kHz. The drivers are saved closely together and act like a virtual point source. After it's all said and done you get a speaker that's ruler flat in every direction in half space above the speaker. It's hard to see how that's not a major achievement in speaker design.

There are a few other speakers that approximate an omni, most notably the MBL 101e. I've never heard these, but they appear to have a few problems compared to the Morrisons with their discrete drivers and distance between the woofer, midrange, and tweeter, preventing them from having good vertical directivity. They are also prohibitively expensive.

There are a few speakers that are omnidirectional horizontally but not vertically. Duevel, German Physiks, Wolcott Audio...

With so few designs out there that I would truly consider omnidirectional, it's reasonable to believe that most people won't have heard how this design when properly implemented actually sounds. A pair of them will completely disappear from the room when music is played and produce a truly holographic soundstage with precise three-dimensional imaging that must be experienced to be understood.

If anyone is in the Chicago area and would like to hear my Morrison audio speakers and compare them to Revel Salon2's, I welcome them to pay a visit.
 
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Thread Starter #139
Speakers like Bose, Dodecahedron, Shahinian etc. are NOT omnidirectional. They are polydirectional, and have a whole host of problems.

The Linkwitz LX Mini is "quasi" omnidirectional, so just partially. In it's case, up to about 800 hz as omni. If you don't believe me, just head to his website and read the plans (or see link later in this post).

The Beolab 5 is not an omnidirectional, but very wide dispersion. Fantastic speaker, "Hall of Fame" material and real progress forward in loudspeaker design. Same for the Jamo open baffles, I think the models were like 907 and 909.

Traditional forward firing box speakers are an inherently flawed concept and totally outdated. A stalled technology based on concepts from 80 years ago. But people still cling to it, because that's what they're used to, or "that's what the studios use," or whatever. The irony is that many people are so keen on using the latest tech. for their other gear, but then insist on using outdated tech on the part of the audio chain where it matters the most.

To make real progress toward realistic sound reproduction, you have to move toward omnidirectional and/or open-baffle. The sound signatures of each are in the same ballpark, neighbors if you will, and so much more realistic.


Linkwitz's journal paper on omni and open baffle:

https://www.linkwitzlab.com/IJAETv2n2a2-Linkwitz-1.pdf


Please, if you don't want to the read the whole thing, or don't want to bother with too much "audio-science", then just the Abstract.
 

Duke

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They are polydirectional, and have a whole host of problems.
I'm very interested in hearing about these problems that various polydirectionals have. Apparently you've thought about this a lot, so have I, but maybe I missed something and/or can learn something.

Also, I'd be interested in hearing your thoughts on how omnis should be set up in a room. I just have a few general ideas on the subject and would like to know more.
 
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