The first speakers in the world. History of musical acoustics. How does a speaker work?
Today we can no longer imagine our life without sounds, music, headphones, inexpensive speakers and branded speaker systems of several hundred watts that plunge neighbors into horror. Let's plunge into almost two centuries history of the development of acoustic systems and we will trace the difficult path of evolution of this integral attribute of our life.
The silence became louder.
Terry Pratchett
Electricity and sound: first experiments
IN 1831 year, the world was awaited by one of the greatest discoveries of our time: an English experimental physicist Michael Faraday observes such a phenomenon as electromagnetic induction. In three years the concept will appear electric and magnetic fields, electromagnetism, and a little later piezoelectricity. Man is gradually entering the era of electricity. Life at that time may seem somewhat boring to us: the absence of television, radio, and electric lighting. For entertainment - balls and theaters, for the soul - live music, for work - manual power, water wheels, windmills and mechanical devices.
More than a dozen years will pass before the appearance of devices even remotely resembling modern speaker systems, but for now the Italian Antonio Meucci is developing "talking telegraph". IN 1849 In the year Meuchi constructs a fully working prototype of the progenitor of the modern telephone, but lack of funds does not allow him to pay the sum of $250 for obtaining a patent. After 11 years, the inventor demonstrates how using a telegraph you can transmit a singer’s voice over a distance of several miles, and already within 1861 year joins research Johann Philipp Reis.
Having published a report “On telephony through electric current,” Johann Reis demonstrates to the public a device that can deservedly be called first loudspeaker. However, Reis prefers the name "music phone". As membranes Reis chose pork intestine submerged in mercury. Copper coil receiver under the influence of current coming from galvanic battery, forced the steel rod of the receiver to be magnetized and demagnetized. Flight Speaker could be heard at a distance of up to 100 meters and its appearance laid a solid foundation on the path of construction electrodynamic acoustic systems.
Alas, the imperfection of the design and the specificity of the materials made it possible to reproduce only very loud sounds. The loudspeaker was not suitable for human speech. A couple of months later, Johann Reis’s invention would be called a “funny toy,” and a German mechanic Albert will personally organize the production of this “useless invention.” One of these devices gets to Alexander Graham Bell. Having studied the principle of operation of the Race speaker, Bell began to develop his own “know-how” - a device for deaf people that converts sound into a light signal. For the next 16 years, Bell developed the telephone and 1876 On February 14, he finally patents his device.
Having completed hundreds of experiments in transmitting telegraph messages and developed dozens of various designs, Bell came to the creation of his next invention. Bell's phone was represented by a tube with a stretched leather membrane, connected to magnetic system and inductor. A “speaker” similar in design was used as a microphone, and therefore the electrical vibrations caused by the human voice were too small to overcome the resistance of long wires. The maximum range of sound transmission via Bell's telephone was only 500-600 meters.
The era of horn speakers
Despite the fact that the foundations of sound amplification were laid back in 3rd century BC and were associated with the emergence of such a musical instrument as organ(received the name in Alexandria "hydravlosa"), the use of a horn similar to wind musical instruments in the field of acoustics began only in the second half of the 19th century.
IN 1877 American inventor Thomas Edison is finishing work on the first device capable of recording and playing back sound. Phonograph became a revolutionary invention, thanks to which in the next thirty years the world would see gramophone, gramophone, records and will encounter such a concept as sound recording(more details in the article: “”). And although Edison was always attracted by electricity, in his acoustic experiments he nevertheless decided to build on the exclusively mechanical capabilities of his invention.
The principle of sound reproduction by a phonograph was sliding needle-cutter along the indentations and irregularities (sound track) formed during recording on foil-covered roller. Mechanical vibrations of the needle were transmitted to emitter membrane, equipped mouthpiece. The physics of sound made it possible, using the simplest acoustic device, to significantly enhance the tiny vibrations of the needle. However, such a purely mechanical acoustic system had a number of disadvantages. The volume level and gain were insufficient, and the sound quality left much to be desired. In addition, horn speakers were too bulky and mobility was out of the question. Their peak in popularity occurred between 1880 and 1920, just at the time when inquisitive minds from all over the world were inventing and mastering electrodynamic acoustic systems.
Manufacturers will return to the horn design of speakers in the future, and already in the 21st century it is this type of emitters, but operating according to the laws of electrodynamics, that will be considered one of the benchmarks for sound quality.
From telegraph and coil to electrodynamic loudspeakers
The operating principle of the speaker, laid down by Alexander Bell, has remained unchanged for almost half a century. IN 1874 year Ernst Siemens receives a patent for use “magnetoelectric apparatus for obtaining mechanical movement of an electric coil under the influence of current”. A coil with special support placed in a magnetic field, according to the author of the patent, was supposed to reproduce sound. Alas, Siemens was unable to confirm the patent in practice. Only in 1898 English physicist and inventor Oliver Lodge patents the design first electrodynamic loudspeaker.
Having laid down the principle of converting input AC signals to produce sound, Siemens actually invented the bicycle frame before the advent of wheels: the German inventor did not have a solution that would allow him to amplify the sound wave, and swinging the loudspeaker head to obtain a sufficient volume level was never imagined at the end of the 19th century possible.
Over the next 25 years, the “electric sound” industry practically stands still, and Edison’s analog phonograph reaches the peak of its popularity. Research by leading physicists and experimenters ultimately allows us to find solutions to provide the loudspeaker coil and head with sufficient power.
Having carried out a series of experiments within the company's laboratory General Electric, inventors Chester Rice And Edward Kellogg V 1924 year they patent operating principle of an electrodynamic emitter. It is based on simple physics: acoustic power increases in proportion to the square of the input signal frequency. Using oscillations of the diaphragm in the frequency range with the maximum excess of the resonance of the moving system, it is possible to obtain slightly distorted sound reproduction. Tying both principles together, Rice and Kellogg received an emitter equipped diaphragm And voice coil.
1926 the year became a turning point in the further evolution of speaker systems. The first industrial radio model enters the market Radiola Model 104 with built-in amplifier with power up to 1 W. Its cost in 1926 was $260 , the amount equivalent $3000 in 2015.
A radio receiver also becomes available to the consumer Radiola 28. The response from the USSR was loudspeaker "Record" for wired broadcasting (“radio point”) and its horn analogue for broadcasting in public areas "TM", developed at the Central Radio Laboratory of Petrograd.
The design of the first electrodynamic loudspeakers included high-impedance coils, which essentially performed role of magnet, driving paper or tissue membrane. At that time, powerful magnets were already actively used in industry and 1927 year Harold Hartley suggests replacing the bulky coil with permanent magnet.
Due to the stability of the magnetic field in the gap, a permanent magnet could provide low distortion (within the evolutionary period of loudspeakers of the first half of the 20th century) of sound. For such “high fidelity” (English “fidelity” - fidelity), the generation of electrodynamic loudspeakers using a permanent magnet is classified as a new class - Hi-Fi(High Fidelity – English “high fidelity”), the standard for which was approved in the 60s of the last century.
"Closed Box"
Surprisingly, the operating principle of electrodynamic emitters, laid down by Oliver Lodge and refined by Rice and Kellogg, has remained unchanged to this day. The speakers that you see on your desk, and those that stand in the room or gather dust on your parents’ closet - they all work on the same principle as the speakers installed in the radio that was released almost 90 years ago. Radiola Model 104. The principle remains the same, but here they are acoustic design has changed dramatically.
If in the evolution of acoustic systems there had not appeared a brilliant inventor named Edgar Vilchur, it would not be easy to answer unequivocally what exactly you would listen to today and what modern speakers would look like. But Vilchur was not only born back in 1917, he managed to make a real revolution in the world of electric acoustics.
Until the mid-50s of the 20th century, engineers were concerned with the issue of improving the sound quality of electrodynamic loudspeakers. For this purpose, research was carried out to find the “holy grail”: experiments with membrane materials, voltage, and coils. Alas, the sound still remained harsh, and the presence of “deep bass” was out of the question. The back side of the speaker housing remained open, which led to a “short circuit” at low frequencies. Another design option for the loudspeaker was using a bass reflex, which, however, also had little effect on the resonant frequency of the head, but made it possible to expand the characteristic into the low-frequency region.
IN 1954 year, American inventor Edgar Vilchur files a patent application to register a device called "closed box". After 2.5 years, the Patent Office satisfies the application and the author receives a license for his invention, which will very soon revolutionize the entire acoustic world.
In order to facilitate the design of the elastic suspension in electrodynamic loudspeakers and reduce the loads acting on it (causing significant sound distortion), Vilchur proposes to include in the work air. The idea may seem incredibly simple, but the secret of genius always lies in simplicity. To implement his idea, Vilchur suggests using closed wooden box, into which to place an electrodynamic loudspeaker.
Just as Archimedes once shouted “Eureka” in ancient times, so the whole world should have shouted: “Found”! The use of a closed housing made it possible not only to significantly enrich the sound of the loudspeaker, but also to saturate it low frequencies and add “meatiness”, but also downsize speaker systems from huge heavy cabinets to small bedside tables.
Another no less brilliant invention of Edgar Vilchur is rightfully considered to be the use dome tweeter(RF emitter or tweeter). The first use of a separate tweeter can be found in the legendary speaker system AR3, which has become a logical evolutionary continuation of the systems AR1 And AR2, released by the company Acoustic Research.
Today, the AR3 column occupies a place of honor in the Smithsonian Museum in Washington. You can find it among the exhibits of the “Information Age”, between Morse telegraph key and Steve Jobs's first PC Apple I.
And away we go...
The basic principles of operation of electrodynamic emitters were laid down back in 1924, the closed box design proposed by Vilchur was registered in 1956. The time has come for experiments, improving the existing design of the acoustic system and taking sound to a qualitatively new level. The most rapid period in the development of acoustic systems occurred in 1970 – 1985 the year when leading manufacturers organize a real technology competition.
IN 1972 year company Sansui represents the first column SF1 with 360-degree sound emission. The Japanese manufacturer immediately gives its answer Pioneer, presenting the model CS-3000 using dome speakers.
Thanks to a horn with an unusual design and radiation capture from the rear side of the diffuser, a small speaker Victor FB-5-2 allows you to sound a standard living space, consuming only 1 W.
First column with really impressive bass(lower playback frequency starts from 20 Hz) goes to 1973 year. Technics SB-1000: 22cm magnets, 10cm coils and weighs 52kg.
A year later, one of the most popular speakers in the history of the industry hits the market. IN 1974 year company Yamaha presents the acoustic system NS 1000. Using beryllium in the production of diffusers, Japanese engineers managed to surpass the heads on the market in almost all characteristics.
Having begun to study the issue of sound reliability of acoustic systems, Technics is again making a technological breakthrough in this area. In March 1975 year at a press conference in Tokyo she demonstrates a three-way speaker Technics SB-7000- bestseller of its time.
In the USSR, they decided to please consumers with powerful sound only towards the end of the 70s. A series of columns came to the attention of Soviet citizens 35 AS-1 And 35 AC 212, known as "loud and booming" S-90».
While Western manufacturers are promoting large and powerful speaker systems designed for concert halls, Japanese companies are choosing to develop “home speaker systems” as a priority.
It is not possible to list all the abundance of acoustic systems that flooded the market from the early 70s to the mid-80s. Manufacturers are experimenting with everything they can: from the placement of speakers, their shape and sound insulation, to the use of the most extraordinary materials in the manufacture of heads. IN 1976 English company Bowers & Wilkins for the first time undertakes the manufacture of a mid-range speaker cone from Kevlar. This is how the model enters the market B&W DM6.
Further searches by manufacturers of acoustic systems are already aimed at obtaining maximum immersion of the listener into the atmosphere of music. But experiments in the field of sound can continue indefinitely, but only precise equipment, the necessary technical equipment and an understanding of what all speaker manufacturers are really striving for could bear fruit. In 1981, the co-founder of the company Bowers & Wilkins John Bowers decides to open a separate research laboratory in a small English town Steyninge.
A few years later, Bowers’ brainchild will become famous far beyond the borders of Great Britain, and "University of Sound" will make an impressive list of discoveries that will take speakers to a completely new level of sound.
After the generally accepted stereo format 2.0 Speaker systems consisting of 3, 5, 7 and even 9 speakers are entering the market, allowing the listener to enjoy multi-channel sound and a 3D surround sound experience.
Appearance in 1994 year of technology Bluetooth for wireless data transmission could not but affect the field of speaker systems. In October 2009 company of the year Creative introduced the first speaker system in the format 2.1 technology that uses technology to transmit an audio signal from a sound source Bluetooth.
One year later, September 1 2010 , as part of a presentation in San Francisco, Apple will present its own technology for wireless streaming data between devices - AirPlay. Following AirPlay, a new page begins in the history of electroacoustics - the era of wireless speaker systems that combine amazing design, excellent sound and amazing functionality. But this is a topic for a separate article.
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Acoustic systems today represent high-tech devices capable of reproducing sound of a wide variety of types. And you can connect modern speakers to almost anything - to any device capable of transmitting sound information: a computer, telephone, TV, stereo system. A separate topic is car audio systems, which also have a wide variety and are often used to modernize factory versions of cars.
But the speakers did not immediately become what we know them now. Just a couple of decades ago, people could not imagine a multi-channel digital speaker system that creates a full-fledged surround sound environment. What were columns like at the beginning of their history and how did they change over time?
Column history
The first prototypes of speakers appeared back in the 19th century. This was, of course, connected with one of the greatest discoveries in the history of mankind - the discovery in 1831 of the phenomenon of electromagnetic induction by Michael Faraday. Soon after, inventors began using electricity in their research, and three decades later, the first telephone prototype was created, using a device such as a loudspeaker to produce sound.
This moment is considered the birth of what has now become a speaker. It became possible to create speakers, but in those days there was simply nothing to connect them to. In addition, at that time there were no amplifiers that were necessary to obtain sufficiently powerful and high-quality sound. All this led to the fact that immediately after their invention, speakers did not gain popularity and widespread use.
However, the technology was not forgotten, and it began its real life after the first tube amplifier was created. From here came the first division of acoustic devices into active ones - using a built-in electrical signal converter, and passive ones - requiring the connection of a separate sound amplifier. The first amplifiers were tube amplifiers - they used ordinary incandescent lamps, which were able to amplify the electrical signal to a power sufficient to reproduce sound.
After the advent of technology for sound amplification, speakers began to develop rapidly. The first device that used an amplifier together with a dynamic driver appeared in 1926 - it was the Radiola 104, which made it possible to produce sound with a power of 1 W. Speakers improved throughout the 20th century, and the 70-80s saw the most active period of acoustic systems. Despite the emergence of ever new technologies, the general principles of speaker design have remained virtually unchanged - both in the past and now they consist of a soundproof housing, an amplifier and a dynamic driver. Only electrical parts improve over time due to the emergence of new materials that can be used in the production of microcircuits and some speaker parts. So, for example, today complex polymer films are appearing, designed to replace paper at the diffuser membrane post.
Speakers acquired their modern appearance in the mid-1950s, when the closed design of acoustic devices was patented in America. The closeness of the speaker from the surrounding air made it possible not only to significantly increase the quality of the sound produced by the speaker, but also to significantly reduce the size of the device. Around the same time, the production of high-frequency speakers - tweeters - was started, which, unlike mid- and low-frequency emitters, have a dome design.
In the mid-1970s, Yamaha made a real breakthrough in the production of acoustic systems - it released the first speakers that used a material that was experimental at that time - beryllium. Sprayed in a vacuum chamber, it was used to construct mid- and high-frequency dynamic emitters. The difficulty of using beryllium was that it is very fragile and easily destroyed under dynamic load. Yamaha engineers have learned to process it in such a way that the integrity of the material is maintained in any conditions.
Why was beryllium so important? The fact is that products made from it have the highest rigidity, which is one of the main parameters of the diffuser membrane, since it is this that determines the stability of the film during vibration. Accordingly, the continuity and purity of sound depends on it. This characteristic somehow needs to be combined with density, which determines how much the material of the diffuser itself influences the sound, and the low weight of the device.
In 1973, the first high-quality subwoofer appeared, reproducing sound with a frequency of 20 Hz. Its design used 22 cm magnets, and the entire device weighed just over 50 kg.
In the USSR, unlike Western countries and Japan, the development of high-quality acoustic systems proceeded at a slow pace. When, like the last top-class speakers, the NS 1000 monitor, which are still considered perhaps the best acoustic devices in history, appeared in 1974, in our country the process of active development and production of Hi-Fi devices only began in the late 70s. x years. The Soviet technical genius was able to create speakers of sufficient quality to meet all international requirements, but they could not be called very good. Despite all the efforts of domestic engineers, Soviet technology could never catch up, much less surpass the quality of the products of Western companies.
Development of computer speakers
After mass production of personal computers began, trends in the development and manufacture of speaker systems also changed. It was necessary to make the speakers not only of sufficient quality, but also compact, and also able to connect to the computer’s sound card.
Before the invention of more or less perfect sound cards, computer speakers were not capable of producing any high-quality sound. It was comparable to the sound of bad tape recorders - while music could still be listened to, human speech, such as song lyrics, was reproduced with terrible interference.
With the advent of sound cards, two-channel sound became possible. This design is still widely used today - it uses a pair of speakers that, using a chip in the computer, are supplied with two separate electrical signals encoding two different channels - usually the front channels, which create the bulk of the sound environment. Such systems are marked with the index 2.0 - that is, they use two full-range speakers and not a single subwoofer.
The sound had already become of sufficient quality - all that remained was to expand its capabilities. To achieve this, the 2.0 system was supplemented with two more speakers – rear ones. With such a 4.0 system, the era of surround sound began. The first such models were not yet what is now a full-fledged multi-channel environment, but they already made it possible to get an idea of the location of sound sources in space. To make the sound even more complete, a subwoofer was added to the wideband speakers, and the system received a 4.1 index.
And finally, one of the final stages in the development of speakers is the emergence of the Dolby Surround system, which is implemented thanks to another, fifth, speaker. This speaker is central and adds the final touch to the sound environment, making the reproduced speech of the highest quality. In addition, the center speaker allows you to combine signals from different channels to amplify them simultaneously.
Thus, the history of speakers is very voluminous and spans almost two centuries. It began with the discovery of electricity, and since then acoustic systems have inextricably followed the development of technology, being an integral part of scientific and technological progress. What will happen to the speakers next is unknown. It seems that it is no longer possible to make the sound even better, but who knows - maybe tomorrow scientists will discover a new material that, when used in speakers, will take the sound to previously unheard of heights.
Ilya 2506
When considering such a concept as a sound perception path, it is necessary to understand that acoustic systems represent the final element. This means that acoustic systems influence the final result, what a person hears. By correctly selecting and optimally configuring your computer's speaker systems, you will be able to fully enjoy all the capabilities of your computer's audio system.
The invention of acoustic systems dates back to the 19th century, but due to the fact that this invention was far ahead of its time, it remained unclaimed for many years. And only in the twenties of the twentieth century, with the advent of tube amplifiers, which were able to provide a powerful signal output, attention was paid to speaker systems. Loudspeaker systems have been continually improved over the past century, with major advances in this direction occurring in the 70s and 80s, but, oddly enough, the basic design of a loudspeaker system has changed little.
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The world-famous company Yamaha introduced the NS 1000 monitor system to consumers already in 1974, which over time became a popular high-end speaker system. By the mid-70s, this company began experiments with a complex material - beryllium. Subsequently, it was Yamaha specialists who were the first to use beryllium for the production of mid-frequency and high-frequency speakers. The innovation was that beryllium was sputtered in a special chamber using vacuum deposition.
In the Soviet Union, unlike the USA, Europe and Japan, the HI-FI industry began its rapid development only in the late 70s. It was during these years that an acoustic system was invented and put into industrial production, which fully met international requirements. But still, until the end of the twentieth century, the domestic industry was not able to even come close to the quality of speaker systems that were produced in the West.
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Today, the consumer market offers a wide range of computer speaker systems that vary in price and quality. Initially, there were two types of computer acoustic speakers - active speakers and passive ones. Active computer speakers had separate power and a built-in amplifier, which allowed them to produce high-quality sound; passive computer speakers did not have their own power and were powered from the computer, and therefore their sound was much worse.
It is safe to say that computer speaker systems originate from an ordinary speaker that was built into the body of a computer system unit. Significant changes occurred when the sound card was invented, which could produce two-channel sound. Today, this system has acquired the name 2.0, where the number two indicates the number of speakers used, and the second - the subwoofer.
Subsequently, a 4.0 acoustic system was developed, which included four speakers. Two speakers were used as front speakers, the other two as rear speakers. This speaker system allows you to reproduce good three-dimensional sound effects. Later, a 4.1 speaker system appeared, which included a subwoofer. This speaker system is four-channel due to the fact that low-frequency signals are separated using a crossover.
The inventors did not stop there, and soon a new 5.1 speaker system was invented and put into production. This system includes two speakers each, used as front and rear, one center speaker and a subwoofer. It is this speaker system that is qualitatively different from the previous 4.1 system due to the appearance of a central speaker, without which it is impossible to recreate the Dolby Digital format. It is the central speaker in 5.1 speaker systems that reproduces the dialogues of movie characters, which makes the Dolby Digital format unique. Today, a 5.1 computer speaker system can be complemented by a DTS decoder or a Dolby Pro Logic decoder, using which the home theater sound acquires new acoustic effects.
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The most important design elements of loudspeakers have remained unchanged since their invention at the beginning of the last century. Modern electroacoustics came onto the market with the invention of the telephone by A. G. Bell and T. Watson in 1876. And although since then the improvement of electroacoustic transducers (that is, loudspeakers) has been the topic of an endless series of scientific research and articles, much more than those devoted to any other element of the sound amplification path, there are practically no fundamental changes.
Speaker history began back in the 19th century. The first patent application for an electrodynamic moving-coil design was filed in 1877, and for an electrodynamic loudspeaker in 1898. However, these inventions did not receive practical application at that time - there was not yet a sufficiently powerful source that would allow the head of a loudspeaker with a moving coil to be driven.
Commercial models did not appear until the 1920s, when tube amplifiers became available. The first electrodynamic loudspeakers had high-impedance coils, fabric suspension, and DC-powered electromagnets. Some technology historians point out that the first electrodynamic head, as close as possible to its modern design, was patented in 1925 by the company General Electric.
Externally, the designs of dynamic heads for reproducing low and high frequencies differ, but contain the same components. The LF head has a metal (less often plastic) frame, which is also called a basket for its shape or a diffuser holder - this is its purpose. The diffuser holder windows provide free air movement at the rear side of the diffuser. In the absence of windows, air could act on the moving system as an additional acoustic load, reducing the output in the low frequency region. The manufacturing technology of the diffuser holder is determined by the power and size of the head. The main requirement is to ensure a rigid structure, free from vibrations that can cause overtones. From this point of view, it is better to use cast structures made of metals or composite materials. A conical diffuser is fixed to the frame, usually made of paper (actually from shredded wood), pure or filled plastic, and less commonly, metal or ceramic. A sleeve (impregnated paper or metal) is attached to the rear (narrower) part of the cone, onto which the voice coil is wound.
The voice coil is usually wound in two (less often - four) layers with copper or aluminum wire in enamel insulation on a frame (sleeve) and secured to it with varnish. Typically, a standard round wire is used, but for very powerful heads, a wire with a rectangular cross-section is used, providing almost 100% filling of the gap. Modern materials are widely used when assembling the moving part of the head. For example, UV-curing polymer adhesives are used to bond the voice coil frame to a ceramic or metal dome cone. The coil terminals are connected to contacts on the connection board using special, very flexible wires.
Despite continuous research in the field of materials science, most LF and MF drivers, which have a similar design but differ in size, use cone diffusers made of paper pulp. In addition, materials such as polypropylene, bextren, and, more recently, light metals (aluminum, titanium, magnesium) are used. Firms with a name and history, having their own research centers or ordering development, are actively experimenting with various fillers and composite materials, creating combined diffusers. Here, the most famous example is the B&W midrange drivers with a diffuser made of woven Kevlar with impregnation. Straight-line cones were used in low-frequency drivers only in the very first drivers. The rigidity of such a design is not enough for the entire operating frequency range, and above a certain frequency the radiation acquires a bending character: only its central part actually works. The diffuser is too heavy and too soft to accurately follow the movement of the coil. It simply does not have time to completely deflect and return, and bending vibrations give rise to overtones and additional coloration of the sound.
The simplest and most ancient way to combat this phenomenon is to form a series of concentric grooves on the surface of the cone during the manufacturing process. Modern loudspeakers use a whole range of measures to suppress parametric resonances. Firstly, almost all diffusers have a curvilinear generatrix. Secondly, more and more of them are made of materials that effectively dampen longitudinal vibrations and, in addition, they have a variable cross-section: the coil has a larger cross-section, and the suspension has a smaller cross-section. Of course, it all depends on the chosen material. For a paper diffuser, a special impregnation is suitable, and for a layered or composite structure, the combination of physical and mechanical properties of its constituent materials is important. Since the range of reproduced frequencies of a loudspeaker head is determined by the area of piston movement of its diffuser, it is important that it be as rigid as possible, but at the same time have a minimum mass.
The external suspension of the diffuser, which ensures its translational movement during operation, can be made as a single unit with the diffuser (in the form of a corrugation with one or several grooves) or as an autonomous ring made of rubber, rubber, polyurethane and other materials with similar properties, which is then glued to the outer edge of the diffuser. The suspension, especially the low-frequency head, must have great flexibility: this ensures a low self-resonance frequency. Almost immediately below this frequency, the efficiency of the head drops sharply, that is, its own resonance determines the limit of bass reproduction.
The second main requirement for a suspension is that the elastic properties must maintain linearity over the entire range of movement of the moving loudspeaker system.
For quite a long time, high-frequency heads had the same conical diffuser, only smaller. However, today the most common type of HF head is the dome diffuser. It can be soft (made of textiles, such as impregnated silk) or hard - made of metal or ceramics. The design of a typical tweeter differs not only in the size of the cone. Typically, a dome cone with suspension is manufactured as a single unit, to which a sleeve with a voice coil is glued. At the same time, the design does not have a flexible centering washer. The magnetic system, like the diffuser, is fixed to the front flange plate.
Dome diffusers, which can be convex or, less commonly, concave, are made by pressing from natural or synthetic fabrics with mandatory subsequent impregnation. HF diffusers - heads made of synthetic polymer films or metal foil - are becoming increasingly common. To increase rigidity, diffusers are made by vapor deposition of various materials: boron, beryllium, gold and even diamond. There are numerous examples of dome diffusers made from ceramic, which is essentially an oxide of metals such as aluminum.
The centering washer is an indispensable part of the woofer or midrange head; its task is to ensure the correct position of the sleeve with the voice coil in the air gap of the magnetic system. The requirements for the washer are the same as for the suspension - maximum flexibility in the axial direction and preservation of linearity throughout the entire range of movement, complemented by the requirement of maximum rigidity in the radial direction. To increase the efficiency of the head, the gap must be minimal, and the slightest displacement in the radial direction will inevitably lead to jamming of the voice coil. Throughout the process of improving heads, the centering washer was made from different materials (cardboard, paper, textolite, fabric). Today, almost all heads have a centering washer with concentric grooves, pressed from fabric and then impregnated.
The most important element of design and dynamics, which largely determines its electroacoustic characteristics, is the magnetic system. It is formed by a ring magnet located between two annular flanges and a cylindrical core, which forms an air gap with the front flange. The design of a magnetic system with a core magnet, widespread in the middle of the last century, is now practically not used in heads designed for multi-way speaker systems. The magnetic system creates a constant magnetic field in the gap. When a signal is applied to the coil, its magnetic field interacts with the field of the magnetic system, causing it to move back and forth depending on the direction of the current and move the diffuser attached to it. The gap should be as small as possible: this increases the efficiency of interaction between the coil and the permanent magnet.
The magnetic field of a system with a ring magnet is not completely closed in the magnetic circuits. This design has an external leakage field that can affect other devices, such as a color TV picture tube. Therefore, in the case of using such speakers in home theater speaker systems, an additional magnetic screen is required, which is a glass of soft magnetic material that covers the entire magnetic system from the outside.
The shape of the pole pieces (the holes in the upper flange) and the core determines the magnitude of the magnetic induction in the air gap and the uniformity of the magnetic flux distribution in it. The degree of heating of the voice coil and, consequently, its heat resistance depend on the size of the elements of the magnetic system and the width of the air gap. There are conflicting demands here. To improve ventilation, you need to increase the gap, but this reduces the sensitivity of the head and requires a larger magnet. Here there is a field of activity for finding a compromise engineering solution. Therefore, for example, in powerful LF heads the coil diameter is larger, and two ring magnets are often used.
As you know, for the woofer to work effectively, it is necessary that the sound waves from the front and rear sides of the diffuser be isolated (see “Acoustic design”, S&V, 4/2004). Therefore, the central hole of the conical diffuser is closed with a cap, which, due to its additional function, is called a dustproof cap. In some designs, a hole is made in the central core of the magnetic system, closed with a sound absorber, and dense fabric or non-woven material with high acoustic resistance is used as the cap material. Piston movement of the diffuser over a wide frequency band is possible only with its ideal rigidity. For real diffusers, due to the occurrence of longitudinal vibrations of the diffuser, the effective band narrows significantly. Note that for an ideal diffuser, the band is limited by its physical dimensions, but for a different reason. The speed of sound in air has a final value of about 340 m/s at room temperature. At a certain frequency, the sound wavelength becomes comparable to the size of the diffuser and even smaller. In practice, this manifests itself as a narrowing of the directional pattern of the dynamic head with increasing frequency. That is, the higher the frequency, the closer to the axis of the head the listener must be in order to hear high frequencies. Thus, for a diffuser with a diameter of 10 inches (250 cm), the theoretical maximum frequency at which the acoustic radiation pattern is compressed into a narrow beam is 1335 Hz.
For the most commonly used size of 8 inches (200 mm) it will be already 2015 Hz, for a driver with a 5 inch (125 mm) cone - 3316 Hz, and for a typical tweeter with a diameter of 1 inch (25 mm) - 13680 Hz. At low and medium frequencies, designers try not to force the heads to work above these frequencies. For HF heads you have to resort to technical tricks. As a rule, a divider of one shape or another is installed in front of the diffuser, depending on the plane in which the radiation pattern needs to be expanded. In our example of the HF head design, the six-beam splitter provides optimal dispersion in both vertical and horizontal planes. In midrange heads, splitters in the form of cones with a complex generatrix are also used to expand the diagram.
A very important parameter of speakers is the linearity of its amplitude characteristics. This is the dependence of sound pressure on the amplitude of vibration of the diffuser. In a certain range of average values everything works fine. However, at small values of the input signal, the interaction force between the field of the coil and the permanent magnet is not enough to overcome the elastic forces of the suspension. This manifests itself audibly as a deterioration in the reproduction of low frequencies at low signal levels. At large amplitudes, the coil goes beyond the limits of the magnet field in the gap, which sharply increases the level of nonlinear distortion. The amplitude of movement of the diffuser, within which the amplitude response of the head remains linear, is very small. For LF heads it rarely exceeds 6 mm, and for HF heads it is 0.3 mm. Due to such a small stroke, to improve heat transfer in the RF heads, the gap of the magnetic system is filled with magnetic fluid, which is a mixture of silicone grease and the finest powder of ferromagnetic material. However, their use limits the service life of the head due to a significant increase in lubricant viscosity over time.
Speaker selection remains the most important among other system components for the final sound you want to achieve in your listening room. On top of everything else, speaker systems have a very wide price range: from less than $100 to more than $70,000 per pair. The question arises what is inside if the price is so high. The answer is as simple as with expensive amplifiers. More expensive loudspeaker systems are produced in small quantities, they feature custom-made drivers (and, in addition, carefully selected parameters) and high-quality cabinets, most often handmade. In general, you see what you pay for, but the tonal characteristics of speaker systems are individual: the differences from sample to sample are perhaps greater than those of all other components of the sound reproduction system. You need to listen and listen to different systems to finally find the one whose sound is most pleasing to your ear. One speaker produces a bright sound in the highs, another produces a harsh sound in the mids, and the third produces very deep bass. Although, of course, there are systems with a more neutral (tonally correct) sound, there is no loudspeaker that correctly reproduces the entire sound range (the one that the human ear hears). They all color the sound to varying degrees, which depends on their price. Sometimes tonal coloring is specifically added to suit the taste of the speaker's creator. Finding speakers that suit your taste takes effort and time.
Alexey Grudinin (Stereo&Video)
Today we can no longer imagine our life without sounds, music, headphones, inexpensive speakers and branded speaker systems of several hundred watts that plunge neighbors into horror. Let's plunge into the almost two-century history of the development of acoustic systems and trace the difficult path of evolution of this integral attribute of our lives. The silence became louder. Terry Pratchett Electricity and sound: first experiments In 1831, the world was waiting for one of the greatest discoveries of our time: the English experimental physicist Michael Faraday observed such a phenomenon as electromagnetic induction. In three years, the concept of electric and magnetic fields, electromagnetism, and a little later piezoelectricity will appear. Man is gradually entering the era of electricity. Life at that time may seem somewhat boring to us: the absence of television, radio, and electric lighting. For entertainment - balls and theaters, for the soul - live music, for work - manual power, water wheels, windmills and mechanical devices. It will be decades before the appearance of devices even remotely resembling modern speaker systems, but for now the Italian Antonio Meucci is developing a “talking telegraph”. In 1849, Meuchi constructed a fully working prototype of the progenitor of the modern telephone, but lack of funds prevented him from paying the $250 fee to obtain a patent. 11 years later, the inventor demonstrates how using a telegraph it is possible to transmit a singer’s voice over a distance of several miles, and already in 1861 Johann Philipp Reis joined the research. Having published a report “On telephony through electric current,” Johann Reis demonstrates to the public a device that can deservedly be called the first loudspeaker. However, Reis prefers the name “music phone”. Reis chose pig intestine immersed in mercury as the membrane. The copper coil of the receiver, under the influence of the current coming from the galvanic battery, caused the steel rod of the receiver to be magnetized and demagnetized. Reis's speaker could be heard at a distance of up to 100 meters and its appearance laid a solid foundation on the path to building electrodynamic acoustic systems. Alas, the imperfection of the design and the specificity of the materials made it possible to reproduce only very loud sounds. The loudspeaker was not suitable for human speech. A couple of months later, the invention of Johann Reis will be called a “funny toy”, and the German mechanic Albert will personally organize the production of this “useless invention”. One of these devices ends up in the hands of Alexander Graham Bell. Having studied the principle of operation of the Race speaker, Bell began to develop his own “know-how” - a device for deaf people that converts sound into a light signal. For the next 16 years, Bell was developing a telephone and in 1876, on February 14, he finally patented his device. Having completed hundreds of experiments in transmitting telegraph messages and developed dozens of various designs, Bell came to the creation of his next invention. Bell's telephone was represented by a tube with a stretched leather membrane connected to a magnetic system and an inductor. A “speaker” similar in design was used as a microphone, and therefore the electrical vibrations caused by the human voice were too small to overcome the resistance of long wires. The maximum range of sound transmission via Bell's telephone was only 500-600 meters. The era of horn speakers Despite the fact that the foundations of sound amplification were laid back in the 3rd century BC and were associated with the advent of such a musical instrument as the organ (received the name “hydraulosa” in Alexandria), the use of a horn, similar to wind musical instruments in the field of acoustics began only in the second half of the 19th century. In 1877, American inventor Thomas Edison completed work on the first device capable of recording and reproducing sound. The phonograph became a revolutionary invention, thanks to which in the next thirty years the world would see the gramophone, gramophone, records and encounter the concept of sound recording (for more details, see the article: “History of Sound Recording”). And although Edison was always attracted by electricity, in his acoustic experiments he nevertheless decided to build on the exclusively mechanical capabilities of his invention. The principle of sound reproduction by a phonograph was to slide a needle-cutter along the indentations and irregularities (sound track) formed during recording on a foil-covered roller. Mechanical vibrations of the needle were transmitted to the emitter membrane equipped with a horn. The physics of sound made it possible, using the simplest acoustic device, to significantly enhance the tiny vibrations of the needle. However, such a purely mechanical acoustic system had a number of disadvantages. The volume level and gain were insufficient, and the sound quality left much to be desired. In addition, horn speakers were too bulky and mobility was out of the question. Their peak in popularity occurred between 1880 and 1920, just at the time when inquisitive minds from all over the world were inventing and mastering electrodynamic acoustic systems. Manufacturers will return to the horn design of speakers in the future, and already in the 21st century it is this type of emitters, but operating according to the laws of electrodynamics, that will be considered one of the benchmarks for sound quality. From the telegraph and coil to electrodynamic loudspeakers The principle of operation of the speaker, laid down by Alexander Bell, has remained unchanged for almost half a century. In 1874, Ernst Siemens received a patent for the use of a “magnetoelectric apparatus for obtaining mechanical movement of an electric coil under the influence of current.” A coil with special support placed in a magnetic field, according to the author of the patent, was supposed to reproduce sound. Alas, Siemens was unable to confirm the patent in practice. Only in 1898, the English physicist and inventor Oliver Lodge patented the design of the first electrodynamic loudspeaker. Having laid down the principle of converting input AC signals to produce sound, Siemens actually invented the bicycle frame before the advent of wheels: the German inventor did not have a solution that would allow him to amplify the sound wave, and swinging the loudspeaker head to obtain a sufficient volume level was never imagined at the end of the 19th century possible. Over the next 25 years, the “electric sound” industry practically stands still, and Edison’s analog phonograph reaches the peak of its popularity. Research by leading physicists and experimenters ultimately allows us to find solutions to provide the loudspeaker coil and head with sufficient power. After conducting a series of experiments within the General Electric laboratory, inventors Chester Rice and Edward Kellogg patented the operating principle of an electrodynamic emitter in 1924. It is based on simple physics: acoustic power increases in proportion to the square of the input signal frequency. Using oscillations of the diaphragm in the frequency range with the maximum excess of the resonance of the moving system, it is possible to obtain slightly distorted sound reproduction. Tying both principles together, Rice and Kellogg obtained a transducer equipped with a voice coil diaphragm. The year 1926 was a turning point in the further evolution of acoustic systems. The first industrial radio model, Radiola Model 104, with a built-in 1 W amplifier, is entering the market. Its value in 1926 was $260, an amount equivalent to $3,000 in 2015. The Radiola 28 radio receiver also becomes available to the consumer. The response from the USSR was the “Record” loudspeaker for wired broadcasting (“radio point”) and its horn analogue for broadcasting in “TM” squares, developed at the Central Radio Laboratory of Petrograd. The design of the first electrodynamic loudspeakers included high-resistance coils, which essentially acted as a magnet driving a paper or fabric membrane. At that time, powerful magnets were already actively used in industry, and in 1927, Harold Hartley proposed replacing the bulky coil with a permanent magnet. Due to the stability of the magnetic field in the gap, a permanent magnet could provide low distortion (within the evolutionary period of loudspeakers of the first half of the 20th century) of sound. For such “high fidelity” (English “fidelity” - fidelity), the generation of electrodynamic loudspeakers using a permanent magnet is classified as a new class - Hi-Fi (High Fidelity - English “high fidelity”), the standard for which was approved in 60 -s of the last century. “Closed Box” Surprisingly, the principle of operation of electrodynamic emitters laid down by Oliver Lodge and refined by Rice and Kellogg has remained unchanged to this day. The speakers that you see on your desk, and those that stand in the room or gather dust on your parents' closet - they all work on the same principle as the installed speakers in the Radiola Model 104 radio, which was released almost 90 years ago. The principle remains the same, but their acoustic design has changed dramatically. If a brilliant inventor named Edgar Vilchur had not appeared in the evolution of acoustic systems, it would not be easy to answer unequivocally what exactly you would listen to today and what modern speakers would look like. But Vilchur was not only born back in 1917, he managed to make a real revolution in the world of electric acoustics. Until the mid-50s of the 20th century, engineers were concerned with the issue of improving the sound quality of electrodynamic loudspeakers. For this purpose, research was carried out to find the “holy grail”: experiments with membrane materials, voltage, and coils. Alas, the sound still remained harsh, and the presence of “deep bass” was out of the question. The back side of the speaker cabinet remained open, which led to a “short circuit” at low frequencies. Another design option for the loudspeaker was the use of a bass reflex, which, however, also had little effect on the resonant frequency of the head, but made it possible to expand the characteristic into the low-frequency region. In 1954, American inventor Edgar Vilchur filed a patent application to register a device referred to as a “closed box.” After 2.5 years, the Patent Office satisfies the application and the author receives a license for his invention, which will very soon revolutionize the entire acoustic world. In order to facilitate the design of the elastic suspension in electrodynamic loudspeakers and reduce the loads acting on it (causing significant sound distortion), Vilchur proposes to include air in the work. The idea may seem incredibly simple, but the secret of genius always lies in simplicity. To implement his idea, Vilchur suggests using a closed wooden box in which to place an electrodynamic loudspeaker. Just as Archimedes once shouted “Eureka” in ancient times, so the whole world should have shouted: “Found”! The use of a closed enclosure made it possible not only to significantly enrich the sound of the loudspeaker, saturate it with low frequencies and add “meatiness,” but also to reduce the size of the speaker systems from huge, heavy cabinets to small bedside tables. Another equally ingenious invention of Edgar Vilchur is rightfully considered the use of a dome tweeter (HF emitter or tweeter). The first use of a separate speaker for high-frequency reproduction can be found in the legendary AR3 speaker system, which became a logical evolutionary continuation of the AR1 and AR2 systems released by Acoustic Research. Today, the AR3 column occupies a place of honor in the Smithsonian Museum in Washington. You can find it among the exhibits of the “Information Age”, between the Morse telegraph key and Steve Jobs's first PC Apple I. And away we go... The basic principles of operation of electrodynamic emitters were laid down back in 1924, the design of a closed box proposed by Vilchur was registered in 1956. It has arrived a time for experimentation, improving the existing design of the speaker system and taking sound to a whole new level. The most rapid period in the development of acoustic systems occurred between 1970 and 1985, when leading manufacturers organized a real technology competition. In 1972, Sansui introduced the first SF1 speaker with 360-degree sound emission. The Japanese manufacturer Pioneer immediately gives its answer, presenting the CS-3000 model using dome speakers. Thanks to a horn with an extraordinary design and radiation capture from the rear side of the diffuser, the small Victor FB-5-2 speaker allows you to sound a standard living room, consuming only 1 W. The first speaker with truly impressive bass (the lower playback frequency starts at 20 Hz) was released in 1973. Technics SB-1000: 22cm magnets, 10cm coils and 52kg weight. A year later, one of the most popular speakers in the history of the industry hits the market. In 1974, Yamaha presented the NS 1000 acoustic system. Using beryllium in the production of diffusers, Japanese engineers managed to surpass the heads on the market in almost all characteristics. Having begun to study the issue of sound reliability of acoustic systems, Technics is once again making a technological breakthrough in this area. In March 1975, at a press conference in Tokyo, she demonstrates the Technics SB-7000 three-way speaker, the best seller of its time. In the USSR, they decided to please consumers with powerful sound only towards the end of the 70s. A series of speakers 35 AC-1 and 35 AC 212, known as the “loud and booming S-90,” came to the attention of Soviet citizens. While Western manufacturers are promoting large and powerful speaker systems designed for concert halls, Japanese companies are choosing to develop “home speaker systems” as a priority. It is not possible to list all the abundance of acoustic systems that poured onto the market from the early 70s to the mid-80s. Manufacturers are experimenting with everything they can: from the placement of speakers, their shape and sound insulation, to the use of the most extraordinary materials in the manufacture of heads. In 1976, the English company Bowers & Wilkins for the first time began manufacturing a mid-range speaker cone from Kevlar. This is how the B&W DM6 model enters the market. Further searches by manufacturers of acoustic systems are already aimed at obtaining maximum immersion of the listener into the atmosphere of music. But experiments in the field of sound can continue indefinitely, but only precise equipment, the necessary technical equipment and an understanding of what all speaker manufacturers are really striving for could bear fruit. In 1981, Bowers & Wilkins co-founder John Bowers decided to open a separate research laboratory in the small English town of Steyning. A few years later, Bowers’ brainchild will become known far beyond the UK, and the “University of Sound” will make an impressive list of discoveries that will take speakers to a completely new level of sound. After the generally accepted 2.0 stereo format, speaker systems consisting of 3, 5, 7 and even 9 speakers are entering the market, allowing the listener to enjoy multi-channel sound and a sense of 3D spatial sound. The advent of Bluetooth technology for wireless data transmission in 1994 could not but affect the field of speaker systems. In October 2009, Creative introduced the first 2.1 speaker system using Bluetooth technology to transmit audio from a sound source. A year later, on September 1, 2010, as part of a presentation in San Francisco, Apple will introduce its own technology for wireless streaming data between devices - AirPlay. Following AirPlay, a new page begins in the history of electroacoustics - the era of wireless speaker systems that combine amazing design, excellent sound and amazing functionality. But this is a topic for a separate article. http://iphones.ru