Eggs, dodecahedrons, and counter-perfection: omnidirectional sound emission - a factor of realism and marketing manipulations

The use of omnidirectional radiation in sound-reproducing equipment is a controversial and controversial issue, which often becomes the subject of debate among music lovers and people passionate about creating their own speaker systems. Now there are 2 main approaches. According to one, omnidirectional radiation is the key to fidelity of reproduction, getting rid of harmful Doppler intermodulation, and even to a realistic arrangement of phantom sources in a stereo panorama. The second, more traditional view, omnidirectional radiation is nothing more than an interesting and peculiar effect of some types of drivers, which is sometimes used by marketers to justify the so-called. prestigious indecent cost components.



In this post, I decided to consider those omnidirectional sound emitters that I know of and to find out which of the approaches is the most honest with respect to the consumer. Under the cut, I will give examples of the omnidirectional drivers that exist today, describe their work and try to find out how each of them corresponds to the properties that are assigned to them.

Contrapertal acoustics

It is a speaker, designed in a special way, coaxially arranged speakers, directed radiating surfaces to each other. This arrangement of emitters under the condition of relative phase-linearity allows you to create a spherical sound wave, which ensures omnidirectionality. A pressure monopole is created and an omnidirectional radiation point arises, which creates a circular horizontal and wide vertical radiation pattern.



Creating a single radiation point will solve the problem of Doppler intermodulation, i.e. distortions that when using classical speakers arise as a result of changing the distance from the diffuser to the listener's ear. The peculiarity of sensitivity to these distortions is evolutionarily determined. The psychoacoustic effect of the noticeability of Doppler intermodulation arose from the need for hearing to determine the distance to the object.



Proponents of this design of emitters believe that the solution allows you to completely get rid of the limitations that inevitably arise when using speakers with a narrow radiation pattern. They also note high psychological comfort from a static point of omnidirectional radiation, eliminating the influence of Doppler intermodulation.

At the same time, counter -perture speakers have a number of obvious drawbacks, such as the difficulty of precise coaxial arrangement of the speakers, the selection of pairs of speakers with identical frequency response, the difficulty of arranging the speakers in the room to form the correct stereo panorama. All these problems deprive counter-perturbation speakers of the opportunity to become any kind of mass product. They are either created by amateur radio experimenters, or built to order not poor audiophiles. Serially practically not produced. All other criteria of high fidelity of reproduction depend on the quality of the emitters used in the system.

We wrote more about counter-aperture speakers here.

Omnidirectional Speakers MBL

Dynamic egg-shaped drivers with metallized diffusers have been used in mbl acoustics for a relatively long time and are a visiting card of the manufacturer. They use the original design, thanks to which the radiating surface of the diffusers is presented in the form of petals, which in the assembly are a spherical speaker. The speakers allow you to get a spherical wave due to the shape and design of the driver, and, accordingly, also provide omnidirectional radiation.



In this case, Doppler intermodulation does not disappear due to the fact that the diffusers are facing the listener and there is no single point of radiation in this case. Acoustics equipped with such drivers can solve the directivity problem, but cannot overcome Doppler modulation, despite the astronomical cost of the speakers created with their help.



Data on non-linear distortions and frequency response capabilities of such acoustics cannot be found in the documentation, as the manufacturer prefers not to disclose this information. For example, according to the measurements of the MBL of Radialstrahler 101E Mk.II and MBL 111B of the authors of Stereophile ( here and here ), the frequency response in the audible frequency range is quite large, which is far from the traditional idea of ​​fidelity of reproduction.


101E Mk.II

There are many stories about the fantastic qualities of these emitters, which determines their cost, meanwhile, waterfall also does not show miracles and reveals resonant problems that are quite expected for such a design.


101E Mk.II

In addition to the expensive and extremely pathos-presentable appearance, the original design of the drivers and the astronomically high cost, the mbl device demonstrates impressive power. A couple of kilowatts, with a fairly high sensitivity of 93 -97 dB, is a common story. This pleases those who love blood from golden ears and terribly upsets their neighbors in elite Moscow apartment buildings and plots on Rublevskoye Shosse. Moreover, the omnidirectionality promises that if the acoustics are marked out equidistant from the neighbors, then it will upset everyone to the same degree, not someone more, but someone less. Omnidirectionality - it is so. For what reason, these gigantic dreams of audiophiles cost 3.5 million rubles per column or more, for me it remains a mystery.

Professional dodecahedrons

In order not to have torment with the coaxial alignment of the speakers, the selection of suitable parameters and the use of fabulously expensive spherical speakers in professional acoustics, it is customary to use more trivial and utilitarian solutions. Often, omnidirectional sources must be used to measure indoors. Acoustic dodecahedrons, which form a wave resembling a spherical one due to the speakers located on each of the faces of the dodecahedron, are quite capable of this task.



For a narrow circle of professional tasks, such devices are enough. It is natural that they have a spherical radiation pattern, i.e. radiate omnidirectionally. At the same time, like MBL speakers, they do not solve the problem of Doppler intermodulation, and they are almost never positioned as a hi-fi product. The use of the dodecahedron in home acoustics is not justified due to the need for a large number of speakers and the likely absence of the expected effect.

In conclusion

At the moment, none of the applications of omnidirectional radiation has won the trust of manufacturers (due to low manufacturability) and in the market (due to the high cost of solutions). The main reason for the low popularity is not even that omnidirectional radiation does not justify the hopes placed on it and is not a certain prerequisite for high fidelity. The problem is that there are no recordings created specifically for these types of acoustics, and sound engineers in the studios work with quite traditional monitors when recording works.

In this case, we are talking more about experimental piece speakers for people who themselves create acoustics, measuring devices (dodecahedrons) and marketing manipulations that are used to form an illusion of usefulness and a significant impact on fidelity of reproduction. Omnidirectional speakers that are theoretically capable of improving sound by eliminating Doppler intermodulation are counterpertural, but they are almost never mass-produced and are difficult to produce. I intentionally did not consider electrostatic and isodynamic speakers, due to the fact that the radiation in them is not omnidirectional, but dipole, and it is not a factor that is positioned as something that positively affects the fidelity of reproduction. Photo

content used:
www.stereophile.com
ldsound.ru
www.mbl.de
www.yaplakal.com

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