Sound box is also called "sound box". It is a very commonly used electroacoustic transducer, which can be seen in electronic and electrical equipment that produces sound.
English name: speakers
Speaker is a kind of transducer that converts electrical signals into acoustic signals, and its performance has a great influence on sound quality. Loudspeaker is the weakest part of audio equipment and the most important part of audio effect. There are many kinds of speakers, and the prices vary greatly. Audio electric energy vibrates its paper basin or diaphragm through electromagnetic, piezoelectric or electrostatic effects, and produces * * * vibration (* * * sound) with the surrounding air to make sound.
Low-grade plastic speakers can't overcome resonance and have no sound quality because of their thin boxes (some designed plastic speakers are far better than inferior wooden speakers); Wooden speakers reduce the sound pollution caused by box resonance, and the sound quality is generally better than that of plastic speakers.
Generally, multimedia speakers are designed with two units and two frequency dividers. A smaller speaker is responsible for the output of medium and high notes, and another larger speaker is responsible for the output of medium and low notes.
The materials of these two kinds of speakers should be considered when choosing speakers: the high-pitched unit of multimedia active speakers is mainly soft dome (in addition, there are titanium domes used to simulate sound sources, etc.). ), combined with digital audio source, can reduce the stiffness of high-frequency signals, giving people a gentle, smooth and delicate feeling. Nowadays, many multimedia speakers use soft balls such as silk film with good quality and PV film with low cost.
Bass unit, which determines the sound characteristics of the speaker, is relatively important to choose. The most common ones are as follows: paper basin, gummed paper basin, paper-based wool basin, pressing basin and so on.
Ordinary loudspeaker
Paper pots have natural timbre, low price, good rigidity, light material and high sensitivity, but the disadvantage is poor moisture resistance, and it is difficult to control consistency when making. But there are paper pots everywhere in the top HiFi system, because the sound output is very uniform and the degree of reproduction is good.
Bulletproof cloth, with wide frequency response and low distortion, is the first choice for people who like heavy bass. The disadvantages are high cost, complicated production process, low sensitivity and poor light music effect.
Wool woven basin, soft in texture, performs very well in light music and light music, but the bass effect is not good, lacking strength and shock.
PP (polypropylene) basin, widely used in high-grade speakers, has good consistency, low distortion and remarkable performance in all aspects. In addition, fiber diaphragm and composite diaphragm are rarely used in public speakers because of their high prices.
The larger the speaker size, the better. Large-caliber bass units perform better at low frequencies and can be selected when purchasing. A sound box made of high-performance speakers means lower transient distortion and better sound quality. The horn of the bass speaker of ordinary multimedia speakers is mostly between 3-5 inches. A sound box made of high-performance speakers also means lower transient distortion and better sound quality.
Our most common electric cone speaker. In the past, we often called the electric cone speaker as the paper cone speaker. Although in 20 14, the paper basin was still the main diaphragm, but many polymer diaphragms and metal diaphragms appeared at the same time, so it is worthy of the name to call it a paper basin speaker. Conical cone speaker is generally composed of three parts: magnetic ring system (permanent magnet, stem, magnetic plate), vibration system (cone, voice coil) and supporting auxiliary system (centering bracket, basin frame, cushion edge).
1. Voice coil: Voice coil is the driving unit of conical cone paper cone speaker. It is made of very thin copper wire wound on a paper tube in two layers, usually with dozens of turns, also called coil, which is placed in the magnetic gap formed by the magnetic core column and the magnetic plate. The voice coil and the paper basin are fixed together. When the acoustic current signal enters the voice coil, the voice coil vibrates to drive the paper basin to vibrate.
2. Paper cone: There are many kinds of materials used in the conical diaphragm of conical paper cone speaker, generally including natural fibers and artificial fibers. Natural fibers are commonly used such as cotton, wood, wool and spun silk. , and artificial fibers use rayon, nylon, glass fiber, etc. Because the paper basin is the sounding device of the loudspeaker, which determines the sound reproduction performance of the loudspeaker to a considerable extent, no matter what kind of paper basin, it is required to be light and rigid, and it cannot be deformed due to the change of environmental temperature and humidity.
3. Folding ring: The folding ring is set to ensure that the paper cone moves along the speaker axis, limit the lateral movement, and at the same time block the empty circulation of the paper cone. In addition to the common materials of paper pots, the folding rings are made of plastics and natural rubber, which are bonded to the paper pots by hot pressing.
4. Centering bracket: The centering bracket is used to support the joint between the voice coil and the paper cone to ensure that it is vertical and not skewed. There are many concentric rings on the centering bracket, so that the voice coil can move freely up and down in the magnetic gap without moving laterally, and the voice coil will not collide with the magnetic conductive plate. The dust cover on the centering bracket is to prevent the external dust from falling into the magnetic gap and avoid the friction between the dust and the voice coil, resulting in abnormal sound of the speaker.
Speaker structure 2
A general loudspeaker consists of a magnet, a frame, a centering bracket and a laminated cone-shaped paper basin. draw
Loudspeaker structure
basic feature
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(1) The speaker has two terminals (two leads). When a single speaker is used, the two pins have no positive polarity or negative polarity, and when multiple speakers are used at the same time, the two pins have polarity.
(2) The speaker has a paper basin, which is usually black and white.
(3) Speakers are round, square and oval.
(4) The back of the paper basin of the speaker is a magnet, and the external magnetic speaker will feel the presence of magnetism when touching the magnet with a metal screwdriver; The built-in magnetic speaker does not feel this way, but there is a magnet inside the shell.
(5) The loudspeaker is installed on the machine panel or in the sound box.
Main types
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There are many kinds of speakers, which can be divided into electric (that is, moving coil type), electrostatic (that is, capacitive), electromagnetic (that is, reed type) and piezoelectric (that is, crystal type) according to their energy conversion principle, and the latter two are mostly used in rural cable broadcasting networks; According to the frequency range, it can be divided into low-frequency speakers, medium-frequency speakers and high-frequency speakers, which are often used as combined speakers in sound boxes.
According to the energy conversion mechanism and structure, the electric loudspeaker has the advantages of good electro-acoustic performance, firm structure and low cost, and is widely used.
According to acoustic radiation materials, it is divided into paper basin type, horn type and diaphragm type; According to the shape of the paper basin, it is divided into round, oval, double-layer paper basin and rubber folding ring; According to the working frequency, it is divided into bass, alto and treble, and some are also divided into special tape recorders, special TV sets, ordinary and high-fidelity speakers. According to the voice coil impedance, it is divided into low impedance and high impedance; According to the effect, it is divided into direct and ambient sound.
Speakers are divided into built-in speakers and external speakers, and external speakers are generally called speakers. The built-in speaker refers to the built-in speaker of MP4 player, so that users can hear the sound of MP4 player not only through the headphone jack, but also through the built-in speaker. MP4 player has built-in speakers, which can avoid the inconvenience caused by external speakers and wearing headphones for a long time.
(1) low-frequency speaker
For different speakers, the requirements for low-frequency speaker quality factor-Q0 value are different. For closed box and inverter box, Q0 value is generally between 0.3 and 0.6. Generally speaking, the larger the aperture, magnet and voice coil diameter of the low-frequency speaker, the better the low-frequency playback performance and transient characteristics, and the higher the sensitivity. The structural form of bass unit is mostly cone-basin type, which also
loudspeaker
A few of them are flat. There are many kinds of diaphragm for bass unit, including aluminum alloy diaphragm, aluminum-magnesium alloy diaphragm, ceramic diaphragm, carbon fiber diaphragm, bulletproof cloth diaphragm, glass fiber diaphragm, propylene diaphragm, paper diaphragm and so on. Generally, the bass units of aluminum alloy diaphragm and glass fiber diaphragm have small diameter ratio and bear large power, while the bass units of reinforced paper basin and glass fiber diaphragm have more accurate timbre and good overall balance when playing back music.
Q0: The quality factor of the loudspeaker unit is a very important parameter, which must be understood before designing and manufacturing the loudspeaker box. On the impedance characteristic curve of the loudspeaker unit, it indicates the sharpness of the impedance peak of the impedance curve at the resonance frequency, and reflects the damping state of the loudspeaker vibration system to a certain extent, which is called Q0 value. The higher the quality factor of the loudspeaker unit, the more difficult it is to control the resonant frequency. The low-frequency characteristics of a loudspeaker are usually determined by the quality factor and resonant frequency of the loudspeaker unit, in which the quality factor is related to the sound pressure output by the loudspeaker unit at the resonant frequency. When the Q0 value is too low, the output sound pressure of the loudspeaker drops rapidly before reaching F0, and the loudspeaker is in an overdamped state, resulting in excessive low-frequency attenuation. When the Q0 value is too high, the loudspeaker damping is insufficient and the low frequency is excessively strengthened. The larger the Q0 value, the steeper the peak value. Therefore, we say that the quality factor of the speaker can neither be too high nor too low. Usually, we take the critical damping value Q0 as 0. 5—0。 7 is the best range.
(2) Intermediate frequency speaker
Generally speaking, if a loudspeaker has a flat frequency response curve, its effective frequency response range is larger than its sound band width in the system, and its impedance is consistent with its sensitivity and low frequency unit. Sometimes the power capacity of the midrange is not enough, so we can choose a midrange with higher sensitivity and impedance, thus reducing the actual input power of the midrange unit. Alto units generally have two types: cone basin and dome. However, its volume and endurance are larger than that of the high-pitched unit, and it is suitable for playing medium audio. The diaphragm of the alto unit is mainly made of soft materials such as paper basin and silk membrane, and occasionally there is a small amount of alloy dome diaphragm.
(3) High frequency speaker
As the name implies, a tweeter is a speaker unit for playing high-frequency sound. Its structural forms mainly include numerical solution type, cone-basin type, spherical top type and aluminum strip type.
Develop products
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Electrostatic loudspeaker
100 years ago in February 1876, Alexander Graham Bell put forward the most important patent "telephone" in history. This invention allows human voice to travel farther than shouting. Since then, human beings have understood the conversion relationship between sound and electricity and enjoyed it.
In order to play back the recorded sound better, in 19 10, S. G. Brown separated the driving force from the diaphragm and invented the armature earphone.
Balanced earphone
19 10, Baldwin invented the balanced armature earphone. Armature earphone is a movable iron plate (armature) installed in the middle of U-shaped magnet. When current flows through the coil, the armature will be magnetized, and the magnets will repel each other and drive the diaphragm to move. This design cost is low, although the effect is not good, but it was also an epoch-making invention at that time. This technology is mostly used in telephone handsets and small headphones.
In recording technology, in 19 17, Winter and Tourasse designed a condenser microphone.
In the mid-1930s, according to the principle of condenser microphone, electrostatic speaker appeared.
loudspeaker
In the early 1950s, American C. V. Bocciarelli put forward the law of "constant charge". P. Walker independently developed the same theory in the same period and applied it to the design of the famous Quad electrostatic speaker.
The basic principle of electrostatic loudspeaker is Coulomb's law. Generally, plastic diaphragms and sensing materials such as aluminum are evaporated in a vacuum. The two diaphragms are placed face to face. When positive current and high voltage are applied to one of them, the other will induce a small current, and air can be pushed to make a sound through mutual attraction and repulsion. Because of the light weight of electrostatic monomer and small vibration dispersion, electrostatic speaker works in the middle and high frequency band, with light and meticulous sound quality and rich characteristics, and it is easy to get clear and transparent middle and high notes. However, its low efficiency, low sound pressure output, small dynamics and high cost are also its weaknesses.
electrodynamic type
At the same time as Bell, different speaker types are proposed. As an amateur, Ernst W. Siemens (Siemens &; 1874,65438)1On October 20th, the founder of Halske Company applied for a patent for a prototype of an electric loudspeaker, in which a voice coil with a supporting system was made in a magnetic field to keep the vibration system moving axially. At that time, it was mainly used in the field of relays rather than speakers. 1877 14 February 14, Siemens applied for a patent for a loudspeaker, and pasted parchment on a moving voice coil as a sound radiator. Parchment can be made into an exponential cone, which is the first full-size loudspeaker in the phonograph era.
1898, Oliver lodge applied for the first patent of practical electric loudspeaker, which moved the voice coil into the magnetic gap between the inner and outer circular plates. Like many inventions, this great invention was too advanced at that time. According to the invention, the structure of 99% of modern moving-coil loudspeakers is determined in 20 14.
Twenty-five years later, in the 1920s, radio broadcasting appeared. C. W. Rice and E. W. Kellogg published an epoch-making paper "A New Type of Non-trumpet Unit", which introduced the direct loudspeaker in detail. The Radiola 104 loudspeaker designed based on this theory costs $250 and is very popular in the United States.
In the past 50 years, the basic principle of electric speakers has not changed, but the design details and components have been improved. Compared with the old products, the frequency response range and dynamic range have made great progress. The electric loudspeaker has become the mainstream of the market in 20 14 years because of its advantages of simple structure, excellent sound quality, low cost and dynamic.
Electric speakers are widely used, which can be divided into three types: paper basin type, horn type and dome type. Only the first two are introduced here.
Various speakers
1, paper basin speaker
Paper cone speaker is also called dynamic speaker.
It consists of three parts: ① vibration system, including cone-shaped paper basin, voice coil and centering bracket; (2) Magnetic circuit system, including permanent magnet, magnetic conducting plate and exciting stem; (3) Auxiliary system, including basin frame, wiring board, blank holder and dust cover, etc. When an audio current flows through the voice coil in the magnetic field, it will generate a magnetic field that varies with the audio current. This magnetic field interacts with the magnetic field of the permanent magnet to make the voice coil vibrate in the axial direction. Because the speaker has simple structure, full bass, soft sound quality, wide frequency band and low efficiency.
2. Small speakers
The structure of loudspeaker is composed of vibration system (tweeter) and loudspeaker. The vibration system is similar to a paper basin speaker, except that its diaphragm is not a paper basin, but a dome-shaped diaphragm. The vibration of the diaphragm radiates sound waves into the air through the horn (after two reflections). High frequency, loud volume, often used for outdoor and square sound reinforcement.
Trumpet type
Trumpet speakers originated from the phonograph. 1928, Winter and Silas produced their efficient loudspeaker receiver. The principle of horn speaker is that the diaphragm pushes the air at the bottom of the horn to work. Because of the high acoustic resistance, the efficiency is very high. However, because the shape and length of the horn will affect the timbre, it is not easy to reproduce the low frequency. Nowadays, high-efficiency trumpet is mainly used in the field of professional sound reinforcement.
belt-type
In the process of the formation of the above speaker technology, people began to understand that the ideal transducer should use a thin diaphragm that can pass current, and everyone began to conceive a belt speaker.
Schottky and Gerlach of Siemens Halske applied for the first patent of belt loudspeaker in June 1923. It installs a horizontal wave-shaped pure aluminum film between the two poles of the magnet, which can reduce the longitudinal hardness and resonance frequency.
193 1 year, Olson and Massa produced tape microphones.
Belt speakers are mainly used in middle and high frequency bands. Because of its flat frequency response curve, extremely high upper frequency limit and very good transient effect, it can easily form a linear sound source.
Although the history of human electroacoustic is so tortuous and complicated, there are indeed many excellent innovative electroacoustic speakers, and in fact, the design of these innovative speakers has tortured many of the best electroacoustic scientists in the last century.
car audio
Horn (loudspeaker), commonly known as the Horn of Africa, is an indispensable equipment and sound system. Everyone in the trumpet listens to music and enjoys it. Because of entering the "acoustic energy", the quality and angle of the electrical energy of the only equipment play a decisive role in the sound and characteristics of the whole sound system.
Horn's sound system stands out in the car. In order to show a good tone and direction, some speakers and their layout are very important criteria. Speakers and effects: In the field of car audio, people have been pursuing such effects: they like to sit in front of the stage in the car because all the sounds are used on the windshield, hair and eyes, and they like the feeling of being in a concert. You can achieve the best reproduction of the sound of each instrument. This is what is commonly called professional Hi-Fi (high fidelity, high definition). The key of ideal high fidelity effect is to synchronize the amplification of sound source and signal in the same frequency band. Home stereo is not difficult. Because the high-frequency unit of household audio is in the same fixed frame, all music signals are amplified by the same amplifier, so it is easier to reduce the proportion uniformly and achieve a good sound quality balance. However, due to the limitation of different car audio installation positions, the subwoofer unit can only be installed in the luggage compartment, the bass unit can only be installed in front of the car, and the tweeter unit is usually installed near the A-pillar. This effect may only come from the contrast of high and low notes on the back of the same month, and the midrange part is relatively weak. In addition, according to the requirements of different modules and power amplification, the general car audio can only use a variety of power amplifiers to drive the speakers (many low-frequency parts of the design need multiple power amplifiers to amplify), so it is difficult to achieve a satisfactory tone balance level. The number and installation arrangement of speakers is one of the key factors to meet these challenges. Number of speakers
The speaker volume can determine the fineness of the specified sound direction, and the small one is rougher. More advanced than ordinary vehicles, car horns. The installation position of the horn is often affected by the sound effect of the car stereo, and the same horn of two companies will have different effects in different installation positions. The installation position of middle and high-grade car horns must be determined through various tests. With the correct installation experience and skills, the number of speakers can cope with the installation positions of speakers with different bandwidths, maintain a good direction, and adjust the power amplifier with compatible technologies, and finally achieve good results. From a professional point of view, the installation layout has a direct impact on the Hi-Fi effect and an excellent balance on the hi-fi sound quality. The audio-visual effects of the front sound field effect (the sound effect is pre-perceived), the sound field position (the influence of different sound sources in other places and the positioning accuracy), the sense of space (the bass response of the spatial acoustic effect), the playback effect (the restoration of high-fidelity sound effect) and (the sound, pitch and image quality results) are respectively. Good underwater acoustic positioning (segmentation) largely depends on the setting of tweeters around the cab and midrange units in front of the cab. Because the human auditory system is mainly in the audio part where sound waves reach the left and right ear rate sound sources successively. The tweeter and loudspeaker installed near the door can form a consistent and coordinated sound source only by installing the intermediate points that are frequently matched. Considering that the left and right sound angles of the audience also depend on the position of the sound horn, it is repeatedly adjusted accurately to make the car sound achieve good sound field positioning. Therefore, the layout of car speakers is very important for car acoustics.
Active orientation
At the 2nd International Expo of 20 14, scientists from Fudan University said that they had successfully invented the "forced stop artifact" of square dance noise-active directional speakers. [ 1]
The sound emitted by ordinary speakers spreads in all directions. In order to achieve orientation, the diameter of the speaker must be very large. Different from the principle of traditional speakers, active directional speakers first load low-frequency sound signals on high-frequency signals with strong directivity, and then amplify them and emit them into the air. Then, the air will quickly filter the high-frequency signals, and the audible sound signals above will naturally be filtered out, realizing directional propagation like laser. [ 1]
Active directional speakers can control sound waves in a specific area, where the sound waves are strong, and outside this area, the sound waves will be weak or even absent. If the square dancers use this horn to play music, the' embarrassment' of disturbing the people will be solved. "Ma Jianmin said. In addition to being the "forced stop artifact" of square dance noise, active directional speakers can also be used in advertising exhibitions, waiting halls, bus stops and other scenes to realize directional sound playback for specific people. [ 1]
20 14 there is no finished product in the domestic market, and the "artifact" is expected to be officially unveiled at the end of this year. Optimists believe that if it can be listed in large quantities, it may solve the problem of noise disturbing people in square dance. [ 1]
Computer loudspeaker
The speakers in win7 system are always automatically disabled.
1. Right-click the computer icon and select Properties.
2. Switch to the "Hardware" tab, select the sound card device in the device manager, right-click to delete the device, find the menu bar to operate, scan for changes, and the system will pop up a prompt that the sound card is being installed, and it will be normal after about 1 minute;
3. In addition, it is also possible that the driver is disabled. I suggest you go to the device manager to find and right-click the audio device, select uninstall, including deleting the driver, then scan the hardware and let the system install the driver by itself. [2]
performance comparison
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Phase judgment
Speaker phase refers to the connection between the positive electrode and the negative electrode when speakers are used in series or parallel: when more than two speakers are used, the audio current flowing through the speakers should be in the same direction as far as possible to keep the vibration direction of the speaker paper basin, so as not to offset the energy of air vibration and reduce the playback effect. In order to achieve this requirement, the anode of one speaker is required to be connected in series with the cathode of the other speaker. When used in parallel, the positive pole of each speaker is connected to the positive pole, and the negative pole is connected to the negative pole, which indicates that the requirements of the same phase are met.
However, the pins of some speakers are not marked with positive and negative words, which affects the use of series and parallel connection. Therefore, we need to determine the positive and negative polarity of the speaker. The method is as follows:
1) Put the multimeter at the lowest position of the DC current block, connect the two probes to the two pins of the speaker respectively, and then press the paper basin of the speaker lightly and quickly with your fingers to observe the swing direction of the multimeter pointer in time. If the pointer swings to the right, it is specified that the red probe is connected to the positive pole and the black probe is connected to the negative pole; If the pointer swings to the left, it means that the red stylus is connected to the negative pole and the black stylus is connected to the positive pole. Use the same method and polarity adjustment to test other speakers and mark them, so that the positive and negative poles can be used in series and parallel and have the same phase.
2) Use one or two batteries (connected in series) to connect the positive and negative poles of the battery to the two pins of the speaker respectively, and pay attention to observe the vibration direction of the speaker paper basin in time when the power is on. If the paper cone moves towards the magnet, the negative electrode of the battery is connected to the positive electrode pin of the speaker. Alternating batteries connect the two pins of the speaker, and the paper basin moves outward, which means that the positive electrode of the battery contacts the positive electrode of the speaker.
Types and working principles of loudspeakers
20 14 uses many kinds of speakers. According to its working principle, it can be divided into electromagnetic, electric, piezoelectric, electrostatic, ion, airflow conversion, airflow modulation and so on. However, in 20 14, the speakers used to play sound in hi-fi system mainly use electric speakers. So far, the loudspeaker is still the weakest link in the hi-fi playback system. Therefore, in order to obtain excellent playback effect, it is very important to choose speakers. If you want to choose a suitable speaker, you should pay attention to the working principle of various speakers.