Omnidirectional speakers. The future?

While the Shahinian's are nice speakers, they really aren't "Omni's" so much as they are multiple radiators arrayed to produce a diffuse pattern. Any time you use multiple drivers, you run into lobing problems due to cancellation, etc... While i hate to bring up a bad word and make yet another comparison to this company, Bose 901's are as much "Omni's" as Shahinians are. This is NOT to compare Shahinian's to Bose, as i have a lot of respect for the Shahinian's and very little for Bose.

Having said that, "true" Omni's* that radiate from a point source ( single driver ) have some very specific problems with them. Most all are spl limited and lack dynamic range. If you can live with that, they can do some truly incredible things at low to medium listening levels. On top of this, their placement will be different from what is optimal for most front firing designs, so this should be factored in before shelling out the cash.

The only "point source Omni's" that i know of are the speakers from Ohm Acoustics. I'm specifically referring to the Ohm A, Ohm F, Ohm G with the G kind of "half in / half out" of that category. This is due to using a passive radiator to reinforce the low frequency response, producing two distinct points of radiation. Since it is not an active driver though and primarily only contributing sounds at low frequencies as it is passively excited, we'll let it "slip by".

The other "Walsh series" speakers that Ohm uses do not use "real" Walsh drivers in the classic sense and are not really omni-directional in nature. These would fall more into the "diffuse radiator" category like the Shahinians. Having said that, they use a very different approach from both the Shahinian's and their namesakes, the A, F and G.

The others that i would consider "Omni's" are the MBL Radialstrahler's, the German Physik's speakers and the Huff's, which use German Physik's drivers in their own proprietary designs. The difference between these "Omni's" and the Ohm's are that the Ohm's are a point source ( single source of sound radiation ) and cover the full frequency range by themselves. The others mentioned above make use of some type of active assistance ( woofers, sub-woofers, etc.. ) in conjunction with the Omni drivers being used for the mids and treble. As such, they have two very distinct and different types of radiation with the associated differences in presentation taking place. Obviously, this is only my opinion, so take it for what it is worth.

As i mentioned in another thread, i really like my F's. I liked the first pair enough after becoming familiar with them to drive to Boston to pick up a second pair. Part of the problem with these and / or any other "esoteric" driver is the lack of support for them and the potential for damage when shipping. Due to the exposed radiating surfaces of these drivers, any type of puncture to the shipping carton can be fatal. On top of that, when the Ohm's ( in specific ) suffer from foam rot due to age, the mass of the cone is hanging strictly from the spider ( the corrugated orange, yellow , tan looking thing behind the cone and in front of the magnet ). Since it is unlikely that you'll find someone locally to repair these ( unless you live in a big city ), you'll have to ship them. With the lack of support from the foam being eaten away, the driver is now slapping the voice coil around inside the magnet as it is moved, producing further possible damage. On top of this, the spider becomes even more stretched out, causing a reduced amount of control of the driver due to a weaker suspension. As such, if you are planning on buying something like this ( or any other exotic speaker ), you better make sure that you can transport them safely AND know where to go should you need to have them repaired.

I could go on and on here, but i've already got one thread where i've said too much going right now : ) Sean
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*Omni's are not really "Omni's" in the fact that most all of them suffer from limited vertical dispersion characteristics. Obviously, "omni" means sound distribution to all directions in an even manner, but due to the limited vertical and horizontal radiation of most other designs, even these "limited vertical radiators" are FAR more "Omni" than most. Omni's should not be confused with Dipole's ( E'stat's, Planar's, Ribbon's ) or Bipole's ( speakers with extra drivers firing out of the rear of the cabinet ) as they are quite different in radiation characteristics. The rear wave coming out of a dipole is out of phase with the front wave whereas a speaker like those mentioned above radiate the signal in all directions horizontally in phase. Bipolar speakers, i.e. those with rear mounted tweeters, mids, woofers, etc... have the front wave and rear wave in phase with each other, but because there is nothing joining the signal as it wraps around the box, these too will produce cancellation when the waves "collide". Due to the continuous radiation of an "omni" driver on all sides, the sound from the driver itself is produced in phase, so there is no cancellation. The only cancellations that do take place are from room reflections, which become even more of a problem. Since you have sound going in EVERY direction in a rather uniform manner, you've got a lot more points to reflect off of. That is why i mentioned different placement within rooms, etc...

Drubin: The design that B&O has is severely flawed, regardless of what you read about it in "Hi-Fi glossies". It is similar in concept to what BIC did 20 years ago and Mirage is trying to do today but with a lot more research and technology involved. It will still suffer from nearfield reflections and the associated standing waves that come with such designs. If you want this to work "right", you have to use a single point source driver. If you don't, you'll run into multiple arrival times from each driver due to the different path lengths that each driver has to take to get to your ears. Not only will you hear the sound directly radiated horizontally out of the driver, but also the sound reflected off of the driver above it. If you look at what they are trying to do with these, you'll be able to see that it is nothing more than a way to duplicate the Ohm A and Ohm F that make use of Walsh drivers with multiple conventional drivers instead. In this aspect, Walsh took the various arrival times into account in this one driver, hence the taper of the cone and what German Physik's calls "bending wave theory". As the top of the speaker is closer to ear height, it is further away from your ear. As the bottom of the cone is physically closer to your ear due to diameter, it is further away from the ear in terms height. Both arrival times should be near identical if the taper of the cone were designed correctly and your seated listening height is taken into account.

El: I have both "panel" type speakers and Omni's. If i could combine the speed and low mass of the planar design with the radiation characteristics of the Omni's and then add SPL capacity to all of that, i would have it all.

As it is, the wavefront from a point source Omni is FAR more natural with a deeper, wider and more spacious presentation than any planar ( or speaker for that matter ) that i've ever heard. None the less, Omni's have their problems too. Since i like specific attributes of each design, i have dedicated systems set-up to run both : )

El: I commented that most "omni's" like the Ohm's are not true Omni's due to the limited vertical dispersion. Other than that, until you can do a side by side and listen to the differences in presentation between a panel and an "omni", it is all "theory".

Holzhauer: There are speakers that have tried to do the "pulsating sphere" thing. The first one that comes to mind is the Design Acoustics D-12. This was a dodecahedron ( 12 sided ) cabinet with a driver on every panel. In effect, you kind of had a wooden "disco ball" with speakers in it. The thing here was that these used conventional woofers, mids, tweeters, etc... and the sound was crossed over and "sprayed" at random. Never heard these in person or read any "real" test reports on them, but i bet it was a disaster both sonically and electrically. Once again, another example in speakers of "good in theory, horrible in implimentation".

As to Stuart Hegemann, there are some articles about his theories and speaker designs in a recent Audio Xpress. From what i can recall, i think that there will be a follow up article. If you're not familiar with Audio Xpress, it is a DIY type magazine that covers everything from electronics to speakers, both SS and tube. I can get you the info on the specific issue(s) if you want.

As to why i said what i did about 901's and the Shahinian's, the 901's effectively radiate in every direction horizontally due to the layout of their drivers on the front and angled rear panels and the purposely designed amount of reflections that they encounter. In effect, they are "spraying & bouncing" everywhere. In the same respect, the Shahinian's ( specifically the Obelisk ) "spray & bounce" the upper frequencies all over due to the use of multiple drivers and the use of angled panels. Having said that, the Shahinian's have far more vertical dispersion, make use of far better quality drivers and actually have a LOT more thought and research put into them. As such, they are similar yet VERY different designs and that is all that i was implying. Once again, i'll point out that i consider the Shahinian's to be a "good" speaker even though there are things about them that i would do differently. With that in mind, i have recommended these speakers to others and have gotten emails from Agon members that are very happy with them after purchasing them based on my recommendations. One should bare in mind that most of these are not designed to "crank" ( much like my Ohm's ) but at "reasonable" volume levels, they produce "magic".

For that matter, i don't know of any speaker made that i think does everything as well as it should and believe that most designs could be easily improved upon. That is why i've modified most everything that i have. Then again, it is quite easy to pass judgment / criticize / "talk shit" in public if one is strictly a spectator and not really in the game "professionally" so to speak : )

Matchstikman: I could give you a LOT of background of how the "radials" came to be and none of it is very supportive. Let's just say that Steve Deckert had a set of my Ohm's and very nearly destroyed them. After playing with them and experiencing what these could do, even though they weren't working correctly due to his "repairs", Steve started working on the "Radials". For that matter, if one can't look at the "Radials" and then Ohm's "Sound Cylinders" and see an amazing amount of resemblance, there's something wrong with their vision. Sean
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PS... While the Decware site and information that is provided looks impressive, believe me, things are NOTHING like that in the real world. Either at their shop or in the services provided. Obviously, some folks know their way around a computer and can create wonderful websites. How close the information presented compares to reality is another matter. Personally, i've "been there, done that, won't EVER go back".

DB: Making such a post would both be useless and deceiving. I've haven't heard 10% of all the speakers out there, so my comments would be quite limited in scope and a dis-service to many manufacturers and readers of this forum. Suffice it to say that there are very few commercially designed speakers in stock form that i think are built as well as they should be or perform as well as they could. The fact that not one pair of speakers that i own ( and i have over a dozen pairs ) are stock should tell you something. Sean
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The "Walsh Series" of Ohm loudspeakers are not omni-directional in any aspect of operation. This is specifically covered on their website. They simply present a diffuse presentation, which may confuse some folks into thinking that they are omni's due to the lack of focus. Sean
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Opalchip: A microphone picks up whatever is fed into it, both direct and reflected energy. It can't discern if the primary or reflected signal should should dominate as it can't differentiate between arrival times and their individual intensities. In effect, it becomes a recorder of acoustic activity at that specific point in time and space based on the specific pick-up patterns of the mic being used.

The Walsh driver simply re-radiates the energy that was captured at the mic as a point source and re-radiates it into the listening environment as a point source. The fact that the original ambient sounds heard during the recording could be heard at every point in the room, and are pretty much preserved and reproduced due to the pseudo-omni radiation characteristics of the Walsh design, is one of the most endearing properties of these speakers. The fact that there is only one driver acting as a point source for each channel reduces time / phase distortions to a minimum, hence the preservation of natural harmonic structure. This too is a very endearing quality of this speaker design. The effects of binaural recordings as heard on these speakers is pretty amazing.

Other than that, each musical note has a primary frequency and multiple harmonic frequencies. These harmonics vary in spectrum and intensity. Any device that tries to separate the audio spectrum into different segments will introduce distortions into each note reproduced. That's because the time, phase & amplitude of the primary note vs that of the harmonics will not remain cohesive in presentation.

As a case in point, the specific device that you mention is capable of expanding multiple different frequency regions at different rates. When doing this, it means that a harmonically rich instrument ( like a Cello ) that is centered in one specific frequency section may be expanded at a different rate than the harmonics, which might fall into one or two different frequency spectrums. As such, each spectrum is / can be expanded at different rates, which in turn varies the amplitude of the harmonics in respect to the amplitude of the primary notes.

The reverse of that is also true. That is, an instrument that covers a very wide range of the audio spectrum ( like a piano ) can have different levels of expansion applied to it across the entire band due to the spectrum segmentation that the device does as part normal processing. This would take place on both the primary note and the harmonics.

As such, expanding a compressed recording could only be done optimally if the algorythms used during recording and playback were exactly the same. Given that this is next to impossible given the differences in recording, mixing and processing techniques, the end results of attempting to expand a compressed recording can be very "interesting" to say the least. I will agree that "expanded" music sounds noticeably more dynamic and "punchy", but at the same time, it also has a certain "artificiallity" to it. On top of that, quite a bit of electronically generated music IS compressed, even when played live. Electric guitars, bass guitars, electronic keyboards, etc... are often processed in a certain manner with the musician specifically desiring certain sonic attributes that compression / clipping bring along with them. Trying to "undo" what was meant to be, both live and on the recording is nothing more than a distortion. These distortions may be pleasant on certain recordings, but it all boils down to a matter of personal preference vs articulate preservation of what is on the recording. Sean
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Opalchip: your comment of "the sound that I enjoy, which is very precise imaging with very minimal coloration" pretty much sums things up. That is, omni's / bipolar's / dipolar's, etc... are all going to produce an image that is more vague than a focused field type of speaker radiation pattern. As far as colouration goes, individual speaker placements, individual room acoustics and individual sonic preferences are going to dictate what is or isn't acceptable to us as individuals.

Personally, i've got multiple different types of speakers in various systems and enjoy them all. Time aligned mini-monitors with dual down-firing subs in the bedroom, large 5 driver 4 way towers as the mains and surrounds in my HT system, a line array of electrostatic tweeters / stacked electrostatic mid panels / multiple dipolar push-pull dynamic woofers in my main system, very large horns in my basement system and omni's in my office system. They all have their good and bad points, but that's what makes them all "special". As i've posted in another thread and if i had to choose between them all, the one set that i would keep would be my Ohm F's. As such, we are obviously on opposite sides of the coin in terms of what we find to be "important" to us in terms of the type of presentation that we enjoy. That doesn't mean that we can't be friends or share a love of music though : ) Sean
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Talk about a coincidence. The speakers in my bedroom system i.e. the time aligned mini-monitors, are very similar to the little Sequerra Pyramids. As mentioned, these are supplemented by two down-firing subs. That system is actively crossed and multi-amped. Sean
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Hassel: i've heard both brands of speakers, but never with anything remotely resembling similar electronics or in the same room. As such, i'm no help there. Sean
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Bose 901's are based on 11% direct vs 89% reflected sound. Unless one is standing completely off axis and slightly around a corner from where the performance is taking place, those ratios are highly unlikely to be anywhere near accurate during a live listening session. The fact that Bose based most of his findings on measurements taken while sitting underneath the overhang of balcony seats may explain at least a portion of his findings. Why someone would use that specific seating location to conduct those types of tests is beyond me though.

As far as binaural recordings go, i mentioned this type of presentation working phenomenally well with Omni's much earlier in this thread. I've commented on this type of recording technique over at AA in the Pro Asylum quite some time ago. When Alan Kafton of Audio Excellence / Audio Dharma cable cooking asked about various methods that could be used to record small ensembles in a nightclub, that was the first technique i told him to try. It is minimally intrusive in terms of set-up and operation and can provide a very natural presentation, both in terms of spatial cues and tonal balance.

As a side note, i used to use this technique when recording bands for "demo's". Not only is the sound "live" i.e. not nearly as manipulated as is done with dozens of mics and processing, it is also lower in distortion ( less microphone overload ) and much closer to what one would actually hear at a show. If a band can sound good on stage without a bunch of multi-track gimmicks, the talent scouts working for record companies know that they can be made to sound "even better" in a studio. The reason for that? They have all the knobs and gadgets required to "make magic happen". At least, so they think. A high quality binaural recording is pretty hard to match in terms of natural sonic qualities. The one major drawback is that it will not sound as "detailed" or "image specific" as an electronically manipulated presentation using dozens of up-close mic's and tons of bells and whistles in the recording chain.

As far as using the "true" Walsh type Ohm's in a huge room, i've never tried it. Their bass output may be up to the task, but they simply can't move enough air to fill the room with sound. That is, they are SPL challenged due to "warbling" i.e. highly audible amounts of Doppler distortion once you hit a certain volume level. With this type of design, there's no way around that problem. Sean
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El: As sound travels further, it loses intensity. This is true whether it is a directly radiated signal or that of a reflected signal. The only time that one encounters increased intensity at a greater distance from the originating source would be in the following situation. The first is when one is stationed in an area where a node occurs in the listening environment. The other example is at the far end of some type of acoustic coupler i.e. the increased output at the far end of a horn throat. Otherwise, the shortest, most direct path will have the greatest acoustic intensity possible, especially at mid to high frequencies. Sean
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El: I don't doubt your observation. The one point that i would make would be in question form to you. That is, "Is just one or both of the principles stated above coming into play in the last row?". Sean
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