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 : )

I have always grooved to the sound of wide-dispersion speakers. I grew up in a household where my father's final listening room speakers were a pair of classic Allison: One towers, with their V-shaped front baffles that sported a dual compliment of their ultra-wide dispersion dome midranges and nipple-shaped tweeters angled 45 degrees apart, and whose flat backs were designed for on-front-wall placement to achieve a virtual infinite-baffle loading of the speaker/room interface. Although they didn't compete with today's speakers in terms of resolution and precision, their presentation was a kind of aural widescreen that energized the whole room to a degree (and even at low volumes) which you just don't hear from most speakers. I'd love to hear the new iteration of this landmark 70's design that was brought out a couple of years ago with renewed involvement from Roy Allison...

I find the sound of dipolar panels like Maggies, Soundlabs, etc. very attractive, until you try setting them up in a realistically-sized listening room ; conventional box-style monopolar radiators are just plain easier to place and extract optimum sound from in many instances. Bipolars can be another story becaue you don't run into as many phase-related difficulties, but I've never been overly impressed with most of the designs I've heard that achieve this radiation pattern through the use of separate, opposed drivers. Maybe something more along the lines of designs like the MBL Radialstahler, Ohm Walsh, or that forthcoming B&O superspeaker, which radiate through 360 degrees from single drivers lacking vertical baffles.

BTW, although I can like the sound of bi-, di-, and omni-polar speakers, I don't necessarily agree with the 'live music' argument against monopolar speakers in theory. Yes, live music is radiated in all directions (although not equally), but I don't view this as being directly analogous to the home playback situation. I am philosophically of the 'you are there' school, as opposed to the 'they are here' school. To be 'there', it is a good idea to minimize the reverberant contribution of the listening room to the reproduced acoustic, which means controlled-dispersion speakers. I see the job of the loudspeakers as being not the inverse of the original musical instruments and performers, but as the inverse of the microphones which recorded them.

The end result is that there often seems to be a sonic dichotomy between the sense of envelopment and presence, whether 'correct' or 'artificial', that you can get from speakers which directly radiate to more than just the frontal direction, and the sense of precise focus and scaled perspective you can get from monopoles. Both have their virtues, but in my listening rooms monopoles have always been the practical dictate. My present choice of Thiel speakers represents a monopolar design having wide dispersion for the breed with very even off-axis response tapering (at least in the horizontal plane - improving the vertical plane uniformity would seem to be one advantage of Thiel's newer coaxial designs) and a low-diffraction cabinet. Actually, I'm not sure that my idealized speaker design wouldn't be a monopolar line- or point-source, the former of which is represented by the Wisdom closed-back narrow planars, and the latter by the Cabasse tri-axial 'eyeballs', neither of which I've had an opportunity to hear, to my sorrow (not that I could really afford 'em anyway). Of course, one could always try installing a pair of Quad ESL's into a wall that's been cut-out to form a simulated infinite-baffle between two relatively small listening rooms...

omnidirectional is without a doubt the best kept secret in home audio. shahinian,allison,gradient,and ohm and a handful of others are still the closest thing to the real thing from bottom to top. they will always be a cult item because they are out of step(and hard to design)with what most hi enders want.

sean...To be precise, the wavefront generated by the original Ohm speakers is cylindrical, rather than spherical.
Lack of vertical dispersion is a good thing when the speaker is used in a room with ceiling and floor to make reflections, and is a characteristic of line arrays, and of the ubiquitous MTM driver configuration. Even so called "planar" speakers resemble line arrays because (Quads excepted) they are taller than they are wide.

More on point sources...the musical instruments are not points, but the microphones that make the recording are. I regard the microphones as "sampling" the planar wavefront of the original sound. Now, when you play back the recording using a point source loudspeaker, the loudspeaker sound radiates outward again forming a spherical (planar) wavefront. However, with a point source speaker the radiation process starts over again from a point, with SPL falling off rapidly with distance, whereas a planar speaker generates the wavefront as it exists at a distance from the source where it has already expanded, and so there is only slight variation of SPL with distance from the speaker.

Speakers of all descriptions can sound good in certain situations (even horns and ported boxes). In fact I have even heard the original Bose speakers sound pretty good with the right setup and kind of music. There is more than one way to skin a cat, which we all agree is a good thing.