Anatomy of speakers: truth and fiction about NXT emitters
Glad to welcome everyone again. We resume activity on this blog after a short break. And I will start with a post on a relatively unusual variety of sound emitters that have been used to create acoustic systems for the past 20 years. Many are also familiar with this technology for use in sounding projection screens, as well as for sound-emitting displays of smartphones and TVs.
The reason for this post was an article posted on the resource respected by me, “Popular Mechanics” , which talked about the creation by Russian developers of thin acoustic systems using the so-called NXT panels. There were also published stories by manufacturers that such speakers have unique properties and transform sound.
The author of the material did not skimp on epithets at all and claimed that he would not have distinguished the reproduced sound of the piano from a live instrument. Moreover, he clearly defined which instrument was recorded. And then I thought that this is the technology that I have undeservedly bypassed in the “Anatomy of Acoustic Systems” cycle. So, under the cut, I will talk about NXT emitters.
To be precise, the correct name for the technology in question is not NXT. Initially, it was called Distributed Mode Loudspeaker (DML), which describes the characteristic features of the radiation quite well. The widely used term NXT comes from the name New Transducers Ltd., the company that patented the technology in 1997.
The principle of creating sound waves in such emitters is the induction of uniformly distributed oscillations, a piezoelectric, electrodynamic or other “pathogen” operating in the sound range. These drivers are located on the panel taking into account its resonant characteristics, due to which not classical point sound emission is generated, but the chaotic movement of various parts of the panel surface.
This principle can be compared with an earthquake or the principle of operation of acoustic instruments. Vibrations from the installation site of the “pathogen” device propagate in the form of peculiar “seismic” waves. Such vibrations move to the edge of the panel, are reflected and summed up in separate clusters of standing waves.
Despite the well-described effect and practical developments, a full-fledged physical model of such radiation has not yet been created, which complicates the tasks for engineers creating such devices. The main difficulty facing developers is the correct location of the emitter on the panel (membrane), which must be done based on the resonant characteristics of the material used.
If we compare this emitter with classical speakers, it has such properties as dipole, diffuse radiation, omnidirectionality (and, consequently, the inability to clearly determine the source), flat dimensions. Manufacturers of acoustics with such emitters also claimed to "maintain sound pressure at a considerable distance from the emitter."
Subjectively, I personally felt something close to a similar effect, but I didn’t take any measurements, so I’m not ready to say very definitely what it is. It is interesting that in modern acoustics, studies regarding this kind of effect are not described, and the reasons why the illusion of the constancy of the long-term preservation of sound pressure are not described either.
Another effect is a very wide horizontal and vertical radiation pattern. The DML driver emits in all directions and erases the localization of the source. Thanks to this, the radiation pattern is maximized, and the stereo effect extends to almost the entire room where the acoustics are located.
Like any other solution in electroacoustics, such emitters have disadvantages. So the diffusion of radiation, the inevitable satellite of this type of loudspeakers and speakers based on them, erases the localization of the KIZ, i.e. It doesn’t form the stereo panorama that the sound engineer intended. Instead, the effect of a wall of sound arises, where there is no clear localization of either real or apparent sources. Moreover, the instruments and voices themselves are relatively well distinguishable.
The same diffusivity with increasing sound density reduces the clarity of the reproduction. This is especially noticeable when playing symphonic and choral works, which may indicate a pronounced harmonic and intermodulation component.
Low frequencies are also becoming a significant problem. It is known that to obtain sufficient amplitude in the low-frequency range, without the use of compromise solutions, such as buzzing phase inverters and sniffing passive emitters, a large diffuser area is needed. For DML emitters, an area of 1.5 square meters is sufficient for tolerable low reproduction.
Another negative feature of NXT panel radiation is the frequency range. So an average panel area of 0.6 square meters. m. is capable of reproducing sound in the frequency range from 100 to 18000 Hz.
In addition to DML emitters, NXT also produces a combined type of BMR driver. This hybrid technology allows you to combine DML with a classic speaker, in an attempt to get effects that are characteristic of both one and the second type. NXT claim that the resulting drivers have the amplitude-frequency response of dynamic speakers, while having a smaller profile and a wider vertical and horizontal radiation pattern.
Comparison of the principles of classic piston, DML and BMR emitters.
The mid and high frequencies that such a driver is capable of emitting are closer to the DML specifications. At the moment, two types of such speakers are available: Audio Full Range (AFR) - broadband with a circular aperture and High aspect ratio panel (HARP), emitters of long and thin form, which are applicable in space-constrained dimensions. BMR, due to the fact that they are also developed by New Transducers Ltd. often called NXT, this should also be considered when choosing.
Thus, it turns out NXT is undeniably interesting as a principle, but it is not an absolute panacea. Moreover, any statements about its ultra-high fidelity of reproduction and the “realism” of sound are most likely an overly subjective assessment. Obviously, speakers based on such drivers have both obvious advantages and tangible disadvantages. The latter can depend on both genre features, and in general, on the features of the principle of operation of emitters. Traditionally, I will be grateful for the community's views on the technology and the prospects for its application.
Jeans
We sell speakers , while in our catalog there are no speakers with NXT emitters. Moreover, the range is rich in speakers with classic electrodynamic drivers, as well as exotic electrostats. We do not exclude that NXT acoustics may appear with us in the foreseeable future.
The reason for this post was an article posted on the resource respected by me, “Popular Mechanics” , which talked about the creation by Russian developers of thin acoustic systems using the so-called NXT panels. There were also published stories by manufacturers that such speakers have unique properties and transform sound.
The author of the material did not skimp on epithets at all and claimed that he would not have distinguished the reproduced sound of the piano from a live instrument. Moreover, he clearly defined which instrument was recorded. And then I thought that this is the technology that I have undeservedly bypassed in the “Anatomy of Acoustic Systems” cycle. So, under the cut, I will talk about NXT emitters.
Actually dml
To be precise, the correct name for the technology in question is not NXT. Initially, it was called Distributed Mode Loudspeaker (DML), which describes the characteristic features of the radiation quite well. The widely used term NXT comes from the name New Transducers Ltd., the company that patented the technology in 1997.
The principle of creating sound waves in such emitters is the induction of uniformly distributed oscillations, a piezoelectric, electrodynamic or other “pathogen” operating in the sound range. These drivers are located on the panel taking into account its resonant characteristics, due to which not classical point sound emission is generated, but the chaotic movement of various parts of the panel surface.
This principle can be compared with an earthquake or the principle of operation of acoustic instruments. Vibrations from the installation site of the “pathogen” device propagate in the form of peculiar “seismic” waves. Such vibrations move to the edge of the panel, are reflected and summed up in separate clusters of standing waves.
Despite the well-described effect and practical developments, a full-fledged physical model of such radiation has not yet been created, which complicates the tasks for engineers creating such devices. The main difficulty facing developers is the correct location of the emitter on the panel (membrane), which must be done based on the resonant characteristics of the material used.
Properties and Benefits
If we compare this emitter with classical speakers, it has such properties as dipole, diffuse radiation, omnidirectionality (and, consequently, the inability to clearly determine the source), flat dimensions. Manufacturers of acoustics with such emitters also claimed to "maintain sound pressure at a considerable distance from the emitter."
Subjectively, I personally felt something close to a similar effect, but I didn’t take any measurements, so I’m not ready to say very definitely what it is. It is interesting that in modern acoustics, studies regarding this kind of effect are not described, and the reasons why the illusion of the constancy of the long-term preservation of sound pressure are not described either.
Another effect is a very wide horizontal and vertical radiation pattern. The DML driver emits in all directions and erases the localization of the source. Thanks to this, the radiation pattern is maximized, and the stereo effect extends to almost the entire room where the acoustics are located.
Imperfect Loudspeaker
Like any other solution in electroacoustics, such emitters have disadvantages. So the diffusion of radiation, the inevitable satellite of this type of loudspeakers and speakers based on them, erases the localization of the KIZ, i.e. It doesn’t form the stereo panorama that the sound engineer intended. Instead, the effect of a wall of sound arises, where there is no clear localization of either real or apparent sources. Moreover, the instruments and voices themselves are relatively well distinguishable.
The same diffusivity with increasing sound density reduces the clarity of the reproduction. This is especially noticeable when playing symphonic and choral works, which may indicate a pronounced harmonic and intermodulation component.
Low frequencies are also becoming a significant problem. It is known that to obtain sufficient amplitude in the low-frequency range, without the use of compromise solutions, such as buzzing phase inverters and sniffing passive emitters, a large diffuser area is needed. For DML emitters, an area of 1.5 square meters is sufficient for tolerable low reproduction.
Another negative feature of NXT panel radiation is the frequency range. So an average panel area of 0.6 square meters. m. is capable of reproducing sound in the frequency range from 100 to 18000 Hz.
BMR - Combined Principle
In addition to DML emitters, NXT also produces a combined type of BMR driver. This hybrid technology allows you to combine DML with a classic speaker, in an attempt to get effects that are characteristic of both one and the second type. NXT claim that the resulting drivers have the amplitude-frequency response of dynamic speakers, while having a smaller profile and a wider vertical and horizontal radiation pattern.
Comparison of the principles of classic piston, DML and BMR emitters.
The mid and high frequencies that such a driver is capable of emitting are closer to the DML specifications. At the moment, two types of such speakers are available: Audio Full Range (AFR) - broadband with a circular aperture and High aspect ratio panel (HARP), emitters of long and thin form, which are applicable in space-constrained dimensions. BMR, due to the fact that they are also developed by New Transducers Ltd. often called NXT, this should also be considered when choosing.
Total
Thus, it turns out NXT is undeniably interesting as a principle, but it is not an absolute panacea. Moreover, any statements about its ultra-high fidelity of reproduction and the “realism” of sound are most likely an overly subjective assessment. Obviously, speakers based on such drivers have both obvious advantages and tangible disadvantages. The latter can depend on both genre features, and in general, on the features of the principle of operation of emitters. Traditionally, I will be grateful for the community's views on the technology and the prospects for its application.
Jeans
We sell speakers , while in our catalog there are no speakers with NXT emitters. Moreover, the range is rich in speakers with classic electrodynamic drivers, as well as exotic electrostats. We do not exclude that NXT acoustics may appear with us in the foreseeable future.
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