A detailed story about the best speakers and how to choose the right one for your needs
In order to properly understand the processes taking place in a box on the wall of which one or more speakers are mounted, you need to carefully read a couple of books, each of which contains more formulas than everything school course physics. I will not get into such a jungle, so this material is not worth it as an exhaustive analysis or guide to building audiophile speakers. However, I really hope that it will help novice music lovers (and some chronic ones too) to properly navigate the variety of acoustic solutions, each of which, of course, its developers call the only correct one.
Some time after the invention in 1924 of an electrodynamic radiator with a conical diffuser (okay, just a speaker), its wooden frame performed primarily decorative and protective functions. It is understandable after for long years listening to records through mica membranes and bells of gramophones, the sound of the new device and without any acoustic refinement seemed just the apotheosis of euphony.
Gramophone membranes were most often made of aluminum or mica.
However, recording technologies were rapidly improving and it became clear that it was extremely problematic to reproduce the audible range more or less plausibly with a speaker simply mounted on some kind of stand. The fact is that the dynamic head left to itself is in a state of acoustic short circuit. That is, the waves from the front and rear surfaces of the diffuser, radiated, of course, in antiphase, freely overlap each other, which most sadly affects the efficiency of work, and especially the bass transmission.
By the way, in the process this story I will most often talk about low frequencies, since their reproduction is a key moment in the operation of any speaker cabinet. RF drivers, due to the small length of the emitted waves, do not need to interact with the internal volume of the column at all, and most often are completely isolated from it.
Soul wide open
The easiest way to separate the speaker's front and rear radiation is to mount it on a shield as large as possible. From this simple idea, the first acoustic systems were actually born, which were a box with an open back wall, since for compactness the edges of the shield were simply taken and bent at a right angle. However, in terms of bass reproduction, the success of such designs was not too impressive. In addition to the imperfection of the body, the problem was also in a very small diffuser suspension course, according to modern concepts. In order to somehow get out of the situation, the speakers were used as large as possible, capable of developing an acceptable sound pressure with a small amplitude of oscillation.
PureAudioProject Trio 15TB with 15" woofers on 3-layer bamboo panels
Despite the apparent primitiveness of such structures, they also had some advantages, and so specific and interesting that the adherents of open speakers have not died out so far.
To begin with, the absence of any obstacles in the path of sound waves is the best way to increase sensitivity. This moment is especially valuable for audiophile tube amplifiers, especially single-ended or devoid of feedback. Paper cones of large diameter, even at a power of about four or five watts, can create a rather impressive, and at the same time surprisingly open and free sound.
With a height of 1.2 m in the world of open acoustics, Jamo R907 are considered almost compact
As for the rear radiation, in order not to introduce distortions into the direct sound, it should arrive at the listener with a noticeable delay (over 12-15 ms) - in this case, its effect is felt as a slight reverberation, which only adds air to the sound and expands the musical space . The subtlety is that in order to create this very “noticeable delay”, the speakers, of course, must be located at a fair distance from the walls. In addition, the large area of the front panel and the impressive size of the bass drivers have a corresponding effect on the overall dimensions of the speakers. In a word, owners of small and even medium-sized living rooms, please do not worry.
By the way, special case open systems- acoustics built on electrostatic emitters. Only due to the almost weightless diaphragm of a large area, in addition to all the advantages described above, electrostats have the ability to delicately transmit even the sharpest dynamic contrasts, and due to the lack of signal separation in the midrange and treble zones, they also have an enviable timbre accuracy.
open decoration
Pros: High-end open speakers are a great way to get a real buzz from listening to purist single-ended tubes.
Cons: It is better to forget about fat compression basses right away. The entire sound path must be subordinated to the idea of open acoustics, and the speakers themselves will have to be chosen from an extremely limited number of proposals.
locked in a box
With the growth of power and the improvement of the parameters of amplifiers, the ultra-high sensitivity of acoustics has ceased to be the main stumbling block, but the problems of uneven frequency response, and especially the correct reproduction of bass, have become even more relevant.
A giant step towards progress in this direction was made in 1954 by the American engineer Edgar Vilchur. He patented a closed-type speaker system, and it was by no means a gimmick in the style of the current patent trolls.
Patent application of Edgar Vilchur for AU in a closed format
By that time, a phase inverter had already been invented and, of course, the speaker was also repeatedly tried on to a box with a bottom, but nothing good came of it. Due to the elasticity of the closed volume of air, it was necessary either to lose a significant part of the energy of the diffuser, or to make the housing prohibitively large in order to reduce the pressure gradient. Vilchur decided to turn evil into good. He greatly reduced the elasticity of the suspension, thus shifting control over the movement of the diffuser to the volume of air - a spring much more linear and stable than a corrugation or a rubber ring.
In a closed box, the movements of the diffuser are controlled by air - unlike paper or rubber, it does not age or wear out
So it was possible not only to completely get rid of the acoustic short circuit and increase the output at low frequencies, but also significantly smooth out the frequency response throughout its entire length. However, there was also a minor moment. It turned out that damping by a closed volume of air leads to an increase in the resonant frequency of the moving system and a sharp deterioration in the reproduction of frequencies below this threshold. To combat such a nuisance, it was necessary to increase the mass of the diffuser, which logically led to a decrease in sensitivity. Plus, the absorption inside the "black box" of almost half of the acoustic energy could not help but contribute to the reduction of sound pressure. In a word, a new type of speaker required amplifiers of quite serious power. Fortunately, at that time they already existed.
Subwoofer SVS SB13-Ultra with closed acoustic design
Today, the closed design is used mostly in subwoofers, especially those that claim serious musical performance. The fact is that for home theaters, the energetic development of the lowest bass is often more important than dynamic and phase accuracy throughout the low-frequency range. But by combining a relatively compact closed sub with decent satellites, you can achieve much more right sound- albeit not filled with ultra-deep basses, but extremely fast, collected and clear. All of the above can also be attributed to full-range speakers, "closed" models of which occasionally appear on the market.
closed box
Pros: Exemplary attack speed and low frequency resolution. Relative compact design.
Cons: Requires a fairly powerful amplifier. Super-deep bass on the verge of infrasound is very difficult to achieve.
Case - pipe
Another way to curb the anti-phase rear radiation was the phase inverter, in Russian literally “phase unfolder”. Most often, it is a hollow tube mounted on the front or rear surface of the case. The principle of operation is clear from the name and is straightforward: once you get rid of radiation reverse side diffuser is difficult and irrational, so you need to synchronize it in phase with the frontal waves and use it for the benefit of the listeners.
The amplitude and phase of air movement in the phase inverter change depending on the frequency of the diffuser oscillations
In fact, an air pipe is an independent oscillatory system that receives an impulse from the movement of air inside the housing. Possessing a completely defined resonance frequency, the phase inverter works the more efficiently, the closer the cone oscillations are to its tuning frequency. Sound waves of higher frequencies simply do not have time to move the air in the pipe, and lower ones, although they have time, but the lower they are, the more the phase inverter phase shifts, and, accordingly, its efficiency. When the phase rotation reaches 180 degrees, the tunnel begins to frankly and very effectively muffle the sound of the bass driver. This explains the very steep drop in speaker sound pressure below the bass reflex tuning frequency - 24 dB / oct.
In the fight against turbulent overtones, phase inverter designers are constantly experimenting
In a closed box, by the way, at frequencies below the resonant frequency response, the frequency response decay is much smoother - 12 dB / oct. However, unlike a blank box, a box with a pipe in the side wall does not force designers to go to any tricks in order to minimize the resonant frequency of the speaker itself, which is rather troublesome and expensive. It is much easier to set up a phase inverter tunnel - just select its internal volume. This is true in theory. In practice, as always, unforeseen difficulties begin, for example, at high volume levels, the air leaving the hole can make noise almost like wind in a stove chimney. In addition, the inertia of the system often causes a drop in attack speed and poor articulation in the bass. In a word, the space for experiments and optimization before the designers of phase inverter systems is simply incredible.
Phase inverter
Pros: Vigorous response to low frequencies, the ability to reproduce the deepest basses, relative simplicity and low cost of manufacture (with a fair amount of calculation complexity).
Cons: In most implementations, it loses to a closed box in terms of attack speed and clarity of articulation.
Let's go without a coil
Attempts to get rid of the genetic problems of the phase inverter, and at the same time save on the volume of the case without compromising the depth of the bass, prompted the developers to replace the hollow pipe with a membrane driven by vibrations of the same working volume of air. Simply put, another low-frequency driver was installed in a closed box, only without a magnet and a voice coil.
A passive radiator can double the effective surface of the diffuser, or even triple it if they are installed in pairs in one column.
The design was called "passive radiator" (Passive radiator), which is often not too well translated from English as "passive radiator". Unlike a subwoofer tube, a passive cone takes up much less space in the cabinet, is not as critical to location, and besides, like the air inside a closed box, it dampens the main driver, smoothing its frequency response.
Subwoofer passive radiator REL S/5. The main driver is directed to the floor
Another plus is that with an increase in the area of \u200b\u200bthe radiating surface, a smaller oscillation amplitude is required to achieve the desired sound pressure, which means that the consequences of the non-linear operation of the suspension are reduced. Both diffusers oscillate in phase, and the resonant frequency of the free membrane is tuned by precise adjustment of the mass - a weight is simply glued to it.
Passive radiator
Pros: Compact body with impressive bass depth. The absence of phase inverter overtones.
Cons: An increase in the mass of the radiating elements leads to an increase in transient distortion and a slowdown in the impulse response.
exit from the labyrinth
Acoustics, armed with phase inverters and passive radiators, reproduce deep basses thanks to resonators working with the mediation of air inside the speakers. However, who said that the volume of the column cannot play the role of a low-frequency radiator by itself? Of course it can, and the corresponding design is called an acoustic labyrinth. In fact, it is a waveguide, with a length of half or a quarter of the wavelength, at which it is planned to achieve system resonance. In other words, the design is tuned to the lower boundary of the speaker frequency range. Of course, using a full wavelength waveguide would be even more efficient, but then for a frequency of, say, 30 Hz, it would have to be made 11 meters.
The acoustic labyrinth is a favorite design of DIY acousticians. But if desired, the case of the most cunning form can be ordered ready-made
In order to accommodate even a twice as compact structure in a column of reasonable dimensions, baffles are installed in the case, forming the most compact curved waveguide, with a cross section of approximately equal to the area diffuser.
The labyrinth differs from the phase inverter in the first place by its less “resonant” (that is, not accentuated at a certain frequency) sound. The relatively low speed and laminar nature of air movement in a wide waveguide prevents the occurrence of turbulence, which, as we remember, generates unwanted overtones. In addition, in this case, the driver is free from compression, which increases the resonant frequency, because its rear radiation encounters practically no obstacles.
Schematic for case calculation at dbdynamixaudio.com
There is an opinion that acoustic labyrinths create less problems with standing waves in the room. However, with the slightest miscalculation in design or manufacture, standing waves can occur in the waveguide itself, which, unlike a phase inverter, has a much more complex resonance structure.
In general, it must be said that the competent calculation and fine tuning of the acoustic labyrinth are very difficult and time-consuming processes. Exactly because of this reason given type cases are rare, and only in speakers of a very serious price level.
acoustic maze
Pros: Not only good response, but also high tonal bass accuracy.
Cons: Big size, very high complexity(read - cost) of creating a properly working structure.
Hey, on the ferry!
The horn is the oldest and, perhaps, the most provocative type of acoustic design. It looks cool, if not outrageous, it sounds bright, but at times ... In old films, the characters sometimes shout something to each other, and the characteristic coloring of such a sound has long become a meme in both the music and cinema worlds.
Avantgarde Acoustics Trio with 2.25 m Basshorn XD low frequency horn array
Of course, the current acoustics have gone very far from a tin funnel with a handle, but the principle of operation is still the same - the horn increases the resistance of the air to better match the relatively high mechanical resistance of the moving speaker system. Thus, its efficiency increases, and at the same time a clear directionality of radiation is formed. Unlike all the structures described earlier, the horn is most often used in high-frequency speaker units. The reason is simple - its cross section increases exponentially, and the lower the reproducible frequency, the larger the size of the output hole should be - already at 60 Hz a bell with a diameter of 1.8 m is required. It is clear that such monstrous structures are more suitable for stadium concerts, where they really can be found periodically.
The main trump card of horn playback adherents is that acoustic amplification allows, for a given sound output, to reduce the membrane travel, which means to increase sensitivity and improve musical resolution. Yes, yes, again a nod to the owners of tube single-cycles. In addition, with proper calculation, bells can play the role of acoustic filters, sharply cutting off sound outside their band and allowing you to limit yourself to the simplest, and therefore minimally distorting electric crossovers, and sometimes even do without them.
Realhorns systems - special acoustics for special occasions
Skeptics do not get tired of reminding about the characteristic horn coloring, especially noticeable on vocals, and giving it a characteristic nasality. It is really not easy to overcome this trouble, although judging by the way the best examples of High-End horns play, it is quite real.
Pros: High acoustic efficiency, which means excellent sensitivity and good musical resolution of the system.
Cons: Characteristic hard-to-remove sound coloration, unchildish sizes of mid- and especially low-frequency structures.
Circles on the water
It is by this analogy that the easiest way to describe the nature of the radiation of counter-aperture acoustic systems, first developed in the Soviet Union in the 80s of the last century. The principle of operation is not trivial: a pair of identical speakers are mounted so that their diffusers are located opposite each other in a horizontal plane and move symmetrically, either compressing or expanding the air gap. As a result, circular air waves are created that radiate evenly in all directions. Moreover, the characteristics of these waves during their propagation are minimally distorted, and their energy decays slowly - in proportion to the distance, and not to its square, as in the case of conventional speakers.
Duevel Sirius combines elements of horn and contra-aperture designs
In addition to the range and circular orientation, counter-aperture systems are interesting for their surprisingly wide vertical dispersion (about 30 degrees versus the standard 4-8 degrees), as well as the absence of the Doppler effect. For speakers, it manifests itself in signal beats caused by a constant change in the distance from the sound source to the listener due to the oscillation of the cone. True, the real audibility of these distortions still causes a lot of controversy.
The mutual penetration of the concentric sound fields of the right and left speakers creates a very extensive and uniform zone of surround perception, that is, in fact, the issue of precise positioning of the speakers relative to the listener becomes irrelevant.
Italian-Russian counter-aperture acoustics Bolzano Villetri
A characteristic feature of counter-aperture is that the sound coming to the listener from virtually all directions, although it creates an impressive presence effect, cannot fully convey information about the sound stage. Hence the stories of listeners about the feeling of a piano flying around the room and other wonders of virtual spaces.
Contraperture
Pros: A wide zone of spectacular surround perception, naturalistic timbres due to the non-trivial use of wave acoustic effects.
Cons: Acoustic space is noticeably different from the sound stage, conceived when recording a phonogram.
And others...
If you think that this list of speaker design options is exhausted, then you greatly underestimate the design enthusiasm of electroacoustics. I have described only the most popular solutions, leaving behind the scenes a close relative of the labyrinth - a transmission line, a bandpass resonator, a case with an acoustic impedance panel, load pipes ...
Nautilus from Bowers & Wilkins is one of the most unusual, expensive and authoritative speakers in terms of sound. Design type - loading pipes
Such exoticism is quite rare, but sometimes it materializes in a design with a truly unique sound. And sometimes not. The main thing is not to forget that masterpieces, like mediocrity, are found in all designs, no matter what the ideologists of a particular brand say.
Hi all.
Finished the project of experimental acoustic systems, layout contra-aperture (omnipolar), that is, all directional. So the task was:
1. bookshelf acoustics
2. two-strip
3. 8 inch full range speaker + tweeter
4. counteropening
5. appearance- steampunk
6. surround sound
7. a flat frequency response is desirable, but not necessary at this stage
8. to fit on a rack
As a result, I did not find anything on the Internet that even closely resembles the declared parameters, which is not surprising. These are very unusual requirements. I had to come up with my own design, divide one volume into two parts and connect them with a channel (transmission line), and make more precise settings with a phase inverter in the second volume, between them a reflector for VLF-HF. The 8-inch broadband speaker was chosen by Asalab (as it turned out, not the best option) Sh-2000. The VISATON G20SC tweeter (a chic speaker, well, it’s not the worst for sure) plays quietly up to 20 kHz and, judging by the graphs, it reaches 30 kHz. As a filter, only one capacitor per tweeter. I will say right away it turned out to realize not all ideas, but first things first.
I cut the material with a plunge-cut saw.
I assemble blanks into assemblies and prepare for gluing.
I am gluing the assembly into a finished case.
I am milling details for the tunnel.
I glue the tunnel into a single structure.
I turn to gluing the cylinder, it creates additional volume and performs decorative functions.
I paste over the hull with American Walnut veneers.
Body parts are ready for assembly.
We collect everything to the end and look at the result.
According to the measurement results, it becomes clear that the frequency response is far from ideal, which confirmed listening.
1 The failure in the middle is due to an undeveloped reflector and defects in the Asalab broadband speaker. In general, it leads to coloration in the sound.
2 Boosting to 600 hertz for the same reasons, altering the speaker and reflector will most likely correct this situation. Coloring is also available.
3 The non-uniformity of the frequency response in the low-frequency range is correctable due to more precise tuning of the phase inverter and reworking the channel connecting the two cases.
4 The volume of sound in non-competition, the locality of the image in the stereo panorama strongly depends on the location of the acoustic systems relative to the walls. The further the better.
5 The sound pressure decreases strongly with increasing distance from the speakers to the listener, near-field speakers. The comfort zone starts right from the speakers and beyond.
6 Objective measurements showed a rolloff at high frequencies, but subjectively no rolloff is felt. Apparently, our ears perceive ambient sound, including from walls, and the microphone captures directional radiation. Due to inefficient reflection on the straight axis, a decline in HF occurs. Feelings are not affected in any way. In general, we can say this, if it were not for the coloring of the sound in the region of 600 and 2500 hertz, the sound can be called large and detailed. But the sound from such systems is highly dependent on the room. The volume and naturalness of the sound is guaranteed in any case, the distance from the walls only affects the localization of images in space.
Bottom line: The potential of the system is very high, but there are also a lot of improvements. But this will be implemented in other projects. Looking ahead, I’ll say that I have already redone the broadband speaker, the result is encouraging, although it was not possible to remove all the shortcomings. But more on that next time.
Contraperture acoustics in Hi-Fi, Hi-End and home theater systems.
No matter how the process of sound reproduction develops, from mono to stereo and multi-channel sound, the most important thing remains the same. This is receiving High Quality the sound of the audio system while maintaining all genre features, impeccable accuracy of musical reproduction. As long as Hi-End has existed, so many audiophiles have been trying to find different ways to recreate natural concert sound at home. There are no minor or unimportant things in this matter, even interconnect cables can play a decisive role in sound reproduction. There are no identical systems, just as there are no identical people. No less important is the genre of music that they prefer to listen to. And it turns out that classical and classic rock or jazz sound natural when played on different audio components. And when using one system to listen to music of different genres, the subtle nuances of sound are often lost for some reason. A great-sounding piano does not mount with electronic instruments at all, and the saxophone ceases to take the soul ...
With the advent of DVD - a new digital source, the carrier of an audio signal encoded in DTS and Dolby Digital 5.1, the situation has become much more complicated. Despite the fact that many audiophiles recognize only a two-channel sound reproduction system, and strongly disapprove of multi-channel sound reproduction, especially home theater, the new principle allows you to fully increase the naturalness and naturalness of the surround sound and sound perception.
Of course, the history of Hi-End is much longer than home cinema, which is only about 5 years old, but it is becoming more widespread every year. I received a visual confirmation of this when I was at the exhibition "Hi-Fi show 2001 & home theater", held at the Sofitel Hotel. How to choose a system so that you can listen to music of different genres with the same pleasure? It is clear that in the conditions of the exhibition it was possible to listen to the sound only approximately. But my attention was attracted by the stand of the company "Valancon", widely known in audiophile circles. Home theater with elegant hourglass acoustics sounded very natural, retaining all the surround sound effects even in the inappropriate acoustic conditions of small hotel rooms. That is why I decided to get to know this acoustics better.
Firm "Valancon" uses acoustics company "Errol Lab". To get a more accurate idea of the sound, I went directly to the laboratory where counter-aperture (with opposing radiators) acoustic systems are produced by Alexei Vladimirovich Vinogradov, a man who endlessly loves sound and is devoted to it throughout his life. He received two specialties at the Moscow Conservatory, works for the Errol Lab and simultaneously conducts a symphony orchestra.
It was here that I learned that ten years ago A.V. Vinogradov, through MEIS (now it is MTUCI), tried to fully realize the hard-to-understand effect of the attractiveness of sound with counter-radiation from the heads. B. Gladkov from VNIIRPEA im. A.S. Popov. Then A.V. became interested in him. Vinogradov. Having passed through the whole chain of theoreticians, practitioners, metrologists (B. Gladkov - A.V. Vinogradov - Shorov V.I. - Zhagirnovsky M.S.), this principle gave certain results. For further research, Zhagirnovsky M.S. advised to contact A.S. Gaidarov, as the Chief Designer of the MEP for Acoustics. Thus, A.V. Vinogradov was the bearer of a new idea, which later received theoretical justification from A.S. Gaidarov. Formalizer, theorist and technical expert, A.S. Gaidarov is trying to build new concept electroacoustics, find vulnerabilities in the existing concept. A fundamentally new technical solution was patented here and abroad. This helped to conduct specialized Scientific research and start commercial production of acoustic systems using a new method.
The principle of counter-opening allows you to achieve a distinct effect of presence and involvement of the listener in the process of sound perception, whether it be music or cinema sound. The unusual uniformity of the sound field and the clear articulation that occur during sound reproduction make it possible to sound also large rooms. This article discusses the use of loudspeakers for domestic purposes only, excluding the use of loudspeakers in the process of sound recording (sound production) or in the production of shows and film shows (stage use).
Errol Lab's range of audio systems represents 15 different models, from desktop, cabinet systems, for example, Sx - 3.7 (65 - 20,000 Hz), Sx - 6 (50 - 20,000 Hz), Sx - 9 (47 - 20,000 Hz), which can also be used in multimedia paths, up to medium-sized systems for home theater with multi-channel sound and club cinemas, for example, Sx - 20 (30 - 20,000 Hz) Sx - 40 (27 - 20 000 Hz). The principle of counter-opening itself allows solving such problems. Some models, such as Sx - 3.7, Sx - 6, Sx - 9 and Sx - 24, are built on a new semi-contra-aperture principle (separate patent), characterized by simplified manufacturability, size and, in the end, price.
If we talk about the semi-counter-aperture principle, then it is interesting to recall the system of V.I. Shorov. He developed 2 basic models of acoustic systems (two- and three-way), patented and mastered their production at the Yantar plant. What these systems have in common is the coaxial arrangement of heads with a vertical axis, with each head directed towards a cone reflector coaxial with it, which evenly distributes radiation in all directions. Outwardly, this construction is very reminiscent of semi-contra-aperture acoustic systems, but Shorov V.I. the task of creating a counterflow that would increase the radiation efficiency was not set.
All semi-contra-aperture and contra-aperture audio systems are created directly at Errol Lab. Selection of speakers for each system is carried out individually. Each speaker system is debugged by hand and constantly listened to during the creation process. Since all work is carried out manually, this is precisely what achieves a high level of sound comfort and exclusivity of each product from 15 models of counter-aperture acoustics. Audio systems correspond to modern ideas about design. Designers engaged by Errol Lab developed several basic design options for counter-aperture systems. These are "Tower" in fabric, "Hourglass" open (painted in any color or finished with veneer), or draped in fabric.
The process of creating acoustic systems at Errol Lab is a closed cycle. The laboratory operates on the metrological basis of the Acoustic Institute named after Acad. N.N. Andreeva. For measurement accuracy specifications components of acoustic systems, the company uses one of the largest sound-measuring anechoic chambers in the world. I managed to visit it myself. Imagine a 9m x 12m x 12m room formed by blanking the walls, ceiling and floor with meter-long wedges of staple fiberglass impregnated with non-combustible resins. You move inside it on a specialized hanging metal trampoline, which gently springs under your feet. And the wedges that muffled the floor, you can observe far below, through the trampoline grate.
The dimensions of the chamber allow reliable measurements to be made at lower frequencies than in smaller chambers, so a free sound field is created here from 25 Hz. In this chamber, measurements of characteristics that comply with international standards are carried out. There is no light inside the chamber, a special supply ventilation is made, since a special climate is necessary to carry out all measurements. There are special tables at certified places. The product is placed on a table or placed on a trampoline, a microphone is located on the coordinate device. All signals pass through the signal cables to the control room, or the sound level meter is installed in the chamber.
Having familiarized myself with all the stages of production, I proceeded to listening to the finished SX - 20 systems. CDs were chosen for listening: "Symphonie Fantastique" by Berlioz, "Golden Baroque", "Clocks and Signs" Time Machine, "More Gold" by Boney M. , "Louis And The Good Book" Louis Armstrong, "Storm" Vanessa-Mae, "Coyote Ugly" soundtrack. This system has an unusually light sound, striking in its transparency, volume, and intelligibility. The soundstage is very natural, imaginative and multifaceted. We can even make out whether the musician is moving around the stage, approaching or moving away from the microphone, hear how tense vocal cords the singer, even a clear, quiet sound of the musician's bow touching the instrument is heard. A symphony orchestra gives us a feeling of unprecedented power and strength of sound, and individual groups of instruments do not merge into a "mess", but are clearly distinguishable even at high volume. High frequencies are rich, full, juicy.
The systems are two-way, but even the absence of a separate ultra-low-frequency band (subwoofer) allows you to reproduce low frequencies with absolute articulation, which is almost not achievable in a system with a separate subwoofer. This is a special pride of the authors. I must admit that the acoustics of "Errol Lab" amazes from the first listening. Acoustics dissolves in sound (not localized), and creates a uniform spatial sound field. Music of any genre (opera, jazz, sacred music, movie soundtracks with special effects, symphony orchestra, classic rock) sounds in its own way, but exactly in accordance with the traditions of the genre. Naturally, Valancon tube amplifiers with their neutral and dynamic path play an important role here.
"Fantastic Symphony" by Berlioz (Deutsche Grammophon. Berlios. Symphonie Fantastique (op.14). A Polygram company) sounded unusually figurative and powerful. The sound is so clear that when listening to an audio system with eyes closed we can "see" the stage, the musicians, feeling the acoustic space of the concert hall in front of us. The bass is elastic, localized at the level of the diaphragm and evokes a feeling of admiration in the listener. Absolutely stunning articulation, detail on different levels volume. The width and depth of the sound stage allows the listener to feel their "involvement" in the musical process. The sound is formed from individual musical instruments that exist in space, just as it would be at a real concert in a conservatory. The musical attack is clearly expressed, not only individual, but also groups of musical instruments are very clearly distinguishable. This recording is above the direct presence at the concert, not all artists and not every concert hall can give a similar effect.
In addition to high-quality sound reproduction, Errol Lab speaker systems are perfect for creating a home theater. Unfortunately, in this regard, it is impossible to evaluate the advantages of acoustics directly in the laboratory, but on the other hand, the Valancon company, which has been cooperating with Errol Lab for many years, provided its specially equipped room for experiments for listening to and watching films on DVDs.
This is a darkened cozy room with a high sloping ceiling, muffled from the inside, with certain acoustic characteristics. The listening room is an important part of the sound reproduction path, since the acoustic conditions of the room can distort the sound of even a high-quality system beyond recognition. It contains a complete set of home theater equipment. Amplifiers "Valancon" and counter-aperture acoustics "Errol Lab" SX - 40 were connected to the path.
Sitting comfortably in soft armchairs with fragrant coffee in your hands, you want to listen to music and watch DVD for a very long time. The acoustics are practically not localized, and the sound effects envelop the listener, leaving the feeling of being directly involved in the film. The sound stage surrounds the listeners, forming many virtual sound sources. Acoustic nuances stand out clearly, but, unfortunately, the sounds of shots and explosions sound without their inherent dryness and harshness. This is the result of tube amplifiers that elevate DVD digital compression, giving digital recordings the richness and naturalness of analog recordings. However, this is compensated by a large surround sound area, which can accommodate many viewers at once and takes up almost the entire room.
The home theater equipment should be carried out individually, front and rear audio components can be combined from various model ranges of counter-aperture systems. In this way, it is easier to fit into the interior, you can choose a unique system designed exclusively for an existing room, or calculate the acoustic space in which you are just planning to install a home theater. Although, in the interior, these speakers cannot be located close to furniture and close to the wall. But this does not detract from the merits of counter-aperture acoustics and its excellent sound.
It is no coincidence that at the last April exhibition of the Russian Hi-End`a in MTUCI, counter-aperture acoustic systems attracted increased attention. Thus, the manufacturers of tube amplifiers Stas Namin and Valancon demonstrated their products using this acoustics. Prices for exclusive Russian acoustics, upon closer examination, turned out to be much more affordable for the buyer than for imported ones of the corresponding class. And this despite the fact that the sound quality of imported acoustics does not always correspond to the price category declared by the manufacturer.
28.09.2001
Attempts to improve acoustic systems have been made since their inception. New technologies, engineering solutions, other concepts have been created for 85 years, but still fundamental science, as such, had little to do with this area. Perhaps this is due to the lack of interest among the military (if it doesn’t shoot, then it’s not necessary) and large corporations (after all, the manufacture of speakers is not the most profitable and voluminous business), sponsoring science as a last resort. Be that as it may, but the Hi-Fi standards adopted at the time were taken by manufacturers as a basis, since they fully correspond to the ideas about the resolution of human hearing (reproducible frequency range and a measure of non-linear distortion), and to make any attempts to further improve - meaningless.
But, as a practical consequence of the introduction of Hi-Fi standards, the Hi-End category suddenly appeared. Amateurs and professionals are constantly trying to create acoustics that sound "as it should", albeit with a violation of the accepted position that "a person will not hear more." Surely, reading magazines and the Internet, you have met with constant disputes about sound among audiophiles and just music lovers. “These columns are like this, and these are like that” - no objectivity. Agree, this is strange for a long-established science. Imagine how the argument would look like that in an isosceles triangle, the right thigh is still shorter? Today we invite you to take a look at acoustics as a science and its practical use but from the other side.
The word "contra-aperture" itself literally means opposing radiating holes (from Latin apertura - hole). The concept of aperture is often used in optics, but in our case, it is better to understand the term as "opposing sources of sound excitation". Such is the architecture of columns built on the counter-aperture principle. Two identical speakers are coaxially located opposite each other, and are switched on in phase. That is, they work synchronously, without any delays, phase and frequency differences. It would seem that such a design can sound right, because the speakers do not look at the listener and interfere with each other? It's time to remember the physical foundations.
Sound should not be understood as oscillatory air currents propagating around the room. A sound wave is a pressure wave. Remember the circles on the water after a drop hits it. The water itself does not flow anywhere, it remains in place, but waves propagate through it, which are the consequences of the displacement of the volume of that very drop. And this movement is reciprocating. So in the air, the molecules themselves do not move anywhere, but only slightly shift, either towards each other, or vice versa, changing the density of the medium in waves.
With a standard speaker design that is familiar to us, the discharged / compressed air zone is located in front of the speaker. Note that it is not the speaker itself that is the source of the sound, but the change in the concentration of air molecules in front of it. Such a solution has one significant disadvantage - the so-called "zone of predominance of the reactive component of radiation", due to the large length of the low-frequency wave compared to the size of the emitter and the low inertia of the air. From which it follows that in order to fully listen to the bass, you need to be at some distance from the speakers, which is sometimes impossible. Therefore, we usually hear low frequencies reflected from the walls, to some extent even formed there, which naturally does not have a positive effect on subjective sensations. Although objectively the wave is present, however, in a somewhat distorted form.
And what happens if we apply the counter-aperture principle? Pressure is created in the air column between the speakers, and the emission point is also between them. A so-called "pressure monopole" is created, a point source of sound. And it is not distributed in frequency at a variable distance from the speakers, but is located between them, radiating evenly in all directions. This is how the problem of the "far zone" was simply solved. But another one appeared, which, as our study will show, in general, does not exist.
Contra-aperture acoustics creates sound pressure, which is always physically a non-directional (scalar) product, which often frightens connoisseurs. “What about the stereo, and the reflections from the walls of the room will multiply at times,” they say. First, it certainly can't be a problem. In the case of a stereo set, we have two monopoles, and nature (the "Huygens" principle) and your brain do the job of converting the differences of the two channels. When two channels are turned on, no special pressure area is formed in which two points are located. All the source localization work is done by our hearing aid, and it is the job of sound engineers to “deceive” the ears by applying phase shifts, delays, and changes in the volume ratio to get the necessary images. And with reflections, the situation is even simpler. The fact is that directional speakers are by no means free from the problem of reflected sound, they also radiate waves in all directions, but already unevenly. And in the so-called "VIP zone", we hear a normal signal, plus a strongly distorted reflected, but attenuated. However, its weakening is so insignificant, despite all the efforts of manufacturers, that it does not play a special role. As a result, it turns out that even in a room that is not very good in terms of acoustic parameters, speakers with a circular directivity (or omnidirectional) can sound obviously better. Another thing is that they still will not sound good, since the room itself will not allow this, creating resonances and other unpleasant effects due to their architectural, structural or other features. This problem is still treated by changing the parameters of the room, and the speakers have nothing to do with it. By the way, contra-aperture acoustics increase the “VIP zone”, because the listener does not need to tensely sit exactly at the top of the triangle created by the stereo pair, being afraid to hear distorted signals coming from the walls. The uniform field of the “clean” sound is wider, and the criticality of the reflected waves is less, because at least to the wall they went the same way as towards you, unlike the speakers of the classical directional design. But surprisingly, the counter-aperture principle allows you to get rid of another misfortune that is inherent in conventional systems, and was previously considered practically insoluble.
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The fact is that the human ear is especially sensitive to the effect of Doppler intermodulation. This term, despite its wording, which frightens a person who is not savvy in physics, means a rather simple effect: phase and frequency shifts or oscillations of a sound wave due to the movement of a sound source. Musicians and sound engineers know it under the name "flanger". And we can just listen to a car or train passing by, and note how the perceived sound of, for example, an engine changes. This effect is well known to fans of model flying aircraft. When you stand next to the circle that the model is flying in, the sound of the motor constantly changes depending on the position of the aircraft, but if you stand in the center and turn it yourself, then the sound for you will be the same. A heightened sensitivity human ear to the effect of Doppler intermodulation can be explained by the response to danger in environment. We must distinguish not only a change in volume, especially since it will not be significant for a distance of several meters (and a few centimeters can solve the issue of life), but also something else, for the sake of an instant reaction. It turns out that the slightest change in the sound of the source is instantly processed by our brain.
Now imagine a speaker. Its membrane moves very quickly relative to you. Back and forth. Consequently, the sound is constantly subjected to frequency and phase distortions. By the way, the outcome is so bad that there is even a harmonic detuning of the note. It would seem that the speaker moves to a minimum distance, and this effect should not be noticeable. But, unfortunately, the human ear, as mentioned above, is so sensitive that even the slightest changes play a noticeable role.
Attention, question! So in what way contra-aperture acoustics can get rid of this effect, does it use the same moving speakers? Curiously, the solution to this problem lay on the surface. Doppler modulation occurs when the sound source approaches or moves away from the listener, and in the case of a vertical (or horizontal) setting, the speaker membrane does not make any movement relative to our ears. Just like a “pilot” holding a string leading to an aircraft model in his hand, like a person sitting in a train, plane or car does not hear any changes in the sound of the engine. The sound source is at the same constant distance relative to it. Additionally, two identical but oppositely directed movements cancel each other out. Another positive effect follows from this.
Listen counter-aperture acoustics more comfortable. Our brain does not have to constantly process the incoming sound as a sound, the source of which is an object moving back and forth (a priori - inherently dangerous). The sound becomes, as it is now fashionable to say "environmentally friendly", comparable to the sounds of wildlife. Of course, this does not eliminate the problem of fatigue from high level volume, but no longer burdens the brain extra work. Moreover, our consciousness, to some extent, rests when listening to natural sounds. It is not for nothing that every second (well, third, for sure) can find discs with the names "Sound of the Sea", "Evening Forest", etc. Such "compositions" allow people to relax, rest, feel safe.
And now, a bit of fly in the ointment, however, not only for counter-aperture acoustics. It may have disadvantages common to all other systems. Unevenness of the amplitude-frequency characteristics of the speakers, cabinet resonances, inconsistency with the amplifier, and the like. But at least a few, and very pressing problems, can be solved with its help. And then, it's a matter of progress, he's not used to standing still.
To top it off, a little practice for those who are interested. A counter-aperture structure can be created without resorting to the installation of two oppositely installed speakers (here, precise installation accuracy and complete identity of these are required). Less effective, but still reflecting the essence, the method is simple. If instead of the second speaker, in the middle of the counter-aperture gap, we place a reflective surface (quite rigid, which does not create additional resonances), then we will get the same effect. Let's give an example tested by the author of this article on ordinary multimedia speakers, standing, as in most homes and offices, next to the computer. We do not recommend taking a floor system for such an experiment, the dimensions will not allow you to manage with small forces. So, the speakers were placed on the rear panel (their speakers look at the ceiling), packs of cigarettes were placed on top of the free places of the case, on which a couple of books were carefully placed. Since then, the speakers have been standing there, producing an indelible effect on people who see this structure, and surprises with a sound unexpected for a $30 system. Of course, it should be noted that in this case you will have to choose the distance from the speaker to the reflective surface that best suits your conditions (speaker size, etc.), and also, experience will not give much results if the system has more than one speaker, since this already implies a more complex design.
And under the curtain. Many people know the famous Zen koan: what does one hand clap sound like? Isn't it true, there is a feeling that the classical design of the speakers also implements an initially logically impossible task. And if Tibetan philosophers train the mind in this way, then we, each in our own house, simply listen to the clapping of one palm ...
