The speaker (speaker box for short) is the mouthpiece of the sound system, which directly affects the sound quality of the sound reproduction and is the most critical part of the sound system. It is like the voice of a singer. Only with a good singing voice can you sing beautiful songs. Therefore, how to choose a loudspeaker with loud sound, beautiful sound quality, minimal distortion and reliable operation is the common concern and pursuit of the majority of users. ***L As a pioneer in professional speaker manufacturers, we have the responsibility to introduce it to everyone.
1) How to choose a speaker?
A speaker is actually a device that passes the audio electrical power signal within the audible range through a transducer (speaker unit), converting it into a signal with sufficient Sound pressure level of audible sound. In order to correctly select a good speaker, you must first understand the properties of the sound signal, and then require the speaker to "authentically" restore the audio electrical signal into a realistic and natural sound.
The human voice and various musical sounds are random signals with very complex waveforms. The frequency range of audible sound generally reaches 20HZ-20KHZ; the spectrum range of language is about 150HZ-4KHZ; and the spectrum range of various music can reach about 40HZ-18KHZ. The energy distribution of its average spectrum is: the bass and mid-bass parts are the largest, followed by the mid-treble part, and the treble part is the smallest (about 10/1 of the energy of the mid-bass part); the energy of the human voice is mainly concentrated in the 200HZ-35KHZ frequency range . The peak amplitudes of these audible random signals are 10-15DB (or even a little higher) greater than their average values. Therefore, in order for the speaker to correctly reproduce these random signals and ensure beautiful sound quality, the speaker must have broad frequency response characteristics, sufficient sound pressure level and a large signal dynamic range. We hope to obtain a sufficiently large sound pressure level with a relatively small signal power input, which requires the speaker to have high efficiency in converting electrical power into sound sensitivity. In addition, we also require that the speaker system will not be damaged when the input signal is moderately overloaded, that is, it must have high reliability. Another point is that users hope to buy good products with "high quality and low price", that is, products with high performance-price ratio. Finally, they must also consider the supporting methods, appearance structure, hoisting method and other conditions of the product.
2) Application of the main technical characteristics of the speaker system
The speaker system has many technical characteristics that are directly related to the sound effects and usage occasions. In order to make good use of these technical characteristics, users must make full use of them. Learn something about them.
1) Two-way (two-way) and three-way (three-way) speaker systems
The spectrum range of audio signals is very wide, and a 20HZ-20KHZ signal needs to be used. This kind of speaker unit cannot satisfy the entire frequency response; because the general large-diameter speaker unit above 12 inches has good bass characteristics and low distortion, but its performance is very poor for signals exceeding 1.5HZ; 1-2 The 2-inch tweeter unit (treble compression driver) performs well in reproducing signals above 3KHZ, but cannot reproduce midrange and bass signals. So there is a speaker system composed of units with various frequency response characteristics. It is called a two-way speaker system composed of two units: bass (including mid-bass) and treble (including mid-range and high-treble). It consists of three units: bass, mid-range and treble. The combination of these units is called a three-way system.
The two-way speaker system has a simple structure and relatively low cost. In order to solve the problem of the lack of this midrange frequency, some manufacturers use a compromise method, that is, to reduce the frequency response of the woofer unit on the frequency dividing network. The characteristics move upward and the frequency characteristics of the tweeter move downward. Another problem is that the frequency crossover point frequency can only be set between 500HZ-2KHZ, and this area is an important part of the spectrum of human voice and music. This leaves a "hollow" feeling and audible distortion in the ear (of course this defect can be somewhat compensated for by the larger slope characteristics of the crossover, for example, 18DB/octave). Because of this, two-way speakers have relatively high requirements for the speaker unit. If the performance of the unit is not good, the sound of the entire speaker system will not be smooth enough, or there will be serious phase distortion.
The characteristics of each unit of the three-way loudspeaker system cannot be compromised, and their respective strengths can be fully utilized. The two crossover points can be selected at the upper and lower parts of the important parts of the mid-range vocal and musical sound spectrum. At the edge, there is no impact on the sound quality, so the three-way speaker system reduces sound distortion, improves sound clarity, improves the performance of the crossover band between bass and treble, and increases the power handling capability of the speaker system. Therefore, it is the best choice for the sound reinforcement system for theatrical performances, concert halls and opera houses.
2) Sensitivity and maximum sound pressure level (SPL MAX)
The speaker unit is a transducer between electrical signals and sounds, and it is required that it can The input power is converted into a very loud sound, which requires the speaker to have higher sound pressure sensitivity. "Sensitivity" is essentially a manifestation of "conversion efficiency". Due to differences in design technology, selected materials, and production processes, various types of speaker systems have great differences in sensitivity. Sensitivity refers to the sound pressure level measured 1 meter away from the speaker axis when 1 watt of electrical power is input into the speaker unit.
If the sensitivity of two speakers differs by 3DB, to achieve the same large sound pressure level output, the electrical input power needs to be doubled, so the speaker with higher sensitivity can emit louder sound.
The input power capability of the speaker system is generally much greater than 1 watt (generally between 100 watts and 2000 watts), so the maximum allowable electrical power can be input in actual use. With the rated maximum power input to the speaker, the sound pressure level produced at 1 meter in the axial direction of the speaker is called the maximum sound pressure level SPL MAX. For example, if a speaker with sensitivity = 100DB, 1W/1M has a maximum power handling capacity of 1000W, then SPLMAX = 100DB + 30DB = 130DB, 1M. Another question that everyone is concerned about is how much the synthetic sound pressure level of two speaker boxes with the same sound pressure level will increase when put together?
--------- "The answer is: indoors The reverberation sound field increases by approximately 3DB beyond twice the radius."
This leads to an economic calculation issue of performance/price ratio. For example, a speaker with SPL1=90DB has a unit price of 5,000 yuan, and another speaker with SPL2=99DB has a unit price of 20,000 yuan. If the system requires a sound pressure level of 99DB, then 8 speakers with a low sound pressure level will be used. (8×5000=40,000 yuan). Only one speaker with another high sound pressure level (20,000 yuan) is enough. In addition, 8 speakers need to be driven with 8 times the power, which increases the investment cost. .
3) Distortion and sound quality
It is a pity that speaker manufacturers do not declare the distortion rate of their products. In fact, it is a very important technical parameter. Sound quality is a relatively abstract evaluation, and it cannot be rated on the document. It can only be subjective listening tests. Usually, sensitivity and sound quality are in conflict, and manufacturers need to make an appropriate balance between the two. Generally speaking, mid- to low-priced products are dominated by sensitivity and pursue performance-price ratio. High-priced products focus on sound quality. The highest level is both.
4) "Personality" and "Personality"
This leads to another relatively abstract and subjective performance evaluation. The speakers used for sound reinforcement are different from the HI-FI audio equipment at home. They must have very high compatibility, because each venue may perform different types of programs, from operas to rock concerts, or they may only be based on speech signals. Lecture conference... Therefore, the sound system must be compatible with different program sources and achieve excellent "evenness", that is, it cannot be biased towards a certain purpose. The HI-FI audio equipment at home only needs to cater to the taste of one person or a small group of people, and the "personality" of the product is allowed to exist. But as professional sound reinforcement system equipment, this "personality" will become "limitations" or "flaws." Professional sound amplification equipment needs to serve a large group of the public, and the program content changes frequently. "Universality" is the basic requirement, compatibility must be strong, and programs of different natures must have "average" performance. In addition, professional sound reinforcement equipment must be "no rendering", "no exaggeration", and "faithfully" restore the sound source. This is "safety" or "usefulness".
5) Directional characteristics of the speaker system
The sound emitted by the speaker is usually non-directional in the low frequency band (below 200HZ) and spreads evenly in all directions. But in the high frequency band, the propagation of sound shows strong directionality. This directional characteristic (all types of speakers are different) is what we should apply in the system design. Excellent constant directivity characteristics can concentrate the energy of sound waves to the audience area during on-site layout, avoiding strong reflection surfaces of sound waves and mutual interference in the sound field. Let’s take an example that is easier to understand: flashlights on the market. The price of an ordinary flashlight and a flashlight with spotlight function can differ several times. Even if a general flashlight has the same power as a spotlight flashlight, the light cannot be projected very far, and the projection area cannot be controlled. The treble part of the speaker is quite similar to the light of a flashlight. If you just need sound, any grade of speakers can do it, just like any ordinary flashlight can provide lighting. However, as a large-scale project, the sound field distribution must be effectively controlled and the projectable distance must be considered. The quality of directivity can affect the success or failure of the project, so speakers with excellent directivity must be selected. The directional characteristics of the speaker cause the sound pressure level that deviates from the axis to gradually decrease as the deflection angle increases; at the same time, the sound pressure level attenuates in inverse proportion to the square of the distance as the sound wave propagation distance increases. In listening areas with different orientations, if the two attenuations are properly selected, the two attenuations can compensate each other, thereby making the sound field more uniform. Large-scale projects need to cover a relatively wide area, and a single speaker is usually not enough to cover it. Multiple speakers need to be assembled into a speaker group (array). In an array speaker system, the constant directivity characteristic prevents sound waves in the mid- and high-frequency bands between speakers from interfering with each other. Using a pair of speakers with the above constant directivity characteristics to form a figure-of-eight arrangement can cover twice the area of ??a single speaker. Otherwise, the sounds will interfere with each other in front of the speakers, seriously affecting the uniformity of the sound field and the clarity of the sound.
6) Power handling capacity of the speaker system
The power handling capacity of the speaker system (or the rated power of the speaker) is an important technical parameter, which represents the long-term continuous safety of the speaker. To understand the power input capability of the speaker, you must first understand how the speaker driver is damaged. There are two modes of driver damage: one is voice coil overheating damage (voice coil burnt, overheating deformation, inter-coil breakdown etc.), the other is that the driver's diaphragm displacement exceeds the limit value, causing damage to the speaker's cone-shaped diaphragm and/or its surrounding elastic components, which usually occurs in low-frequency signals containing many large amplitudes. The sound signal is not a pure sine wave signal, but a random one. These random signals can be expressed by three parameters: the effective value (RMS), also known as the root mean square value, is a sinusoidal signal with the same amplitude as the signal peak. A measurement, close to the average, that essentially represents the heating energy of a signal.
Peak (PEAK) is the maximum level reached by the signal. For sine waves, the peak level is 3DB greater than the effective value level. For music signals, the peak level exceeds the effective value by up to 10 DB. -15DB, the peak value is important when evaluating the displacement capability of a speaker. The crest factor is used to describe the ratio of the peak level to the effective value level. For the pink noise source according to AES2-1984, the crest factor is 6DB, that is, the peak voltage is 4 times the effective value voltage. The speaker's power handling capability is a technical parameter measured when the permanent change in its electrical and mechanical properties does not exceed 10% after the pink noise signal processed according to (AES2-1984) is continuously added for 2 hours of operation.
7) The sound pressure level decreases after loading (heating) (also known as power compression)
The nominal power in all product manuals is determined by each manufacturer, which is the performance of the speaker. The best value under test signals and conditions selected by the factory. When the speaker enters the working state (for example, after 20 seconds equal to or greater than full power), the voice coil and magnet are heated and the temperature rises. Due to their performance degradation, the original characteristics of the unit before heating are changed. At this time, the actual sound pressure output will reduce. For conventional speakers, if the temperature of the voice coil rises by 60℃-80℃, the common rated sound pressure level drops by 3DB as a tolerance. If the voice coil has excellent heat dissipation and the temperature reaches above 100℃, the actual sound pressure drop can reach 6 to 8DB. This is That's quite an astonishing drop. As mentioned in the previous article, doubling the number of speakers only increases the sound pressure level by 3DB. If the sound pressure level of the speakers drops by 6DB, to make up for such a large drop in sound pressure level, the number of speakers must be increased from one to four. It is a pity that the audio industry does not have the habit of labeling this kind of sound pressure level drop. Users can only compare various brands to choose the best one for their use. To improve this drop in sound pressure level, the heat dissipation design of the speaker unit must be better improved.
8) Impedance of speaker unit
The impedance of speaker unit includes inductance, capacitance and resistance value. Inductance and capacitance vary with frequency. Although there is a nominal impedance in the speaker system, such as 8 ohms, 4 ohms, this value will change as the frequency changes. If the impedance changes too much, it will affect the stability of the entire audio system. ***L's latest DCD dual-coil differential drive design changes the impedance into "pure resistance", which is not affected by frequency changes, allowing the entire sound system to work stably.
3) How to improve the reliability of the speaker system
In daily life, speaker unit damage may occur even when the power of the power amplifier and speaker system are matched. . The reasons are:
1. Improper operation and excessive power amplifier output
2. When the performance reaches its climax, the atmosphere in the venue is warm and the sound pressure needs to be increased. When increasing the signal , the microphone input signal is too large, causing the power amplifier to overload and clip, and the distorted waveform generates a large number of harmonics, damaging the tweeter.
3. The microphone produces strong acoustic feedback and howls, and the power amplifier is strongly overloaded, damaging the speaker system. To this end, modern new speaker systems have adopted a variety of protective measures, which can be divided into two categories:
(1) Improve the heat dissipation of the speaker unit so that it will not be damaged by overheating when overloaded.
(2) Install a limiting protection device in the speaker box. When the driving power and peak level exceed the rated value of the speaker, the limiter will use a non-linear resistor (light bulb) to reduce the exceeded power level. Block the voice coil. These measures improve the speaker's ability to withstand overload, but also affect the dynamic range of the sound, making the sound range not wide enough and the timbre feeling fuzzy and dim. Therefore, the best way is to take measures on the power amplifier to prevent its output from problems such as clipping and power overload.
4) What new technological measures have been taken by ***L speaker system?
In recent years, the American ***L company has continuously improved the various performances of the speaker system in terms of design and Many effective new technological measures have been adopted in production.
Treble unit:
. It adopts patented titanium alloy diaphragm technology that is as light as tissue paper, harder than steel, and only 0.001 inches thick with a three-dimensional diamond pattern edge. The technology not only makes the treble clearer and brighter, but it can also withstand greater impact.
.The voice coil wire uses a special square cross-section aluminum alloy wire, plus a specially formulated insulating patent leather, which makes the voice coil both light and dense, increasing the power capacity and sound pressure sensitivity.
. The use of magnetic fluid (MAGNETIC FLUID) improves the heat dissipation conditions of the voice coil and enhances the ability to withstand overload.
. The novel KAPTON material is used as the voice coil bracket. The thermal conductivity of this material is 2 times larger than conventional materials and can withstand higher temperatures, ensuring that the voice coil can still work normally at high temperatures.
"SONICGUARD" is a breakthrough invention that prevents damage to the tweeter caused by sudden high-power peak signals or long-term overloading. SONICGUARD and The difference between general limiting protection technology is that it allows many very dynamic signals in music to pass through without enough energy to burn out the voice coil; it automatically shunts overload energy and destructive peak signals. Attenuate to a safe level. This process is performed automatically and silently, achieving the best of both worlds without sacrificing sound quality (music and clarity).
Mid-range/mid-treble unit:
In order to match the new model of barrel, ***L has specially developed 2447 and other ultra-large compression drivers. The high-frequency response is flat to 18KHZ, and the mid-range sound quality is improved, making the entire The sound in the mid-to-high range is clearer and brighter without being harsh. The performance of a two-way speaker system composed of this unit is comparable to that of a three-way system.
Wolf unit:
SVG. With a transducer designed with VGC heat dissipation, the woofer unit often has to withstand a lot of power continuously. Only a small part of the film energy is converted into sound energy, and most of it is converted into harmful heat energy. After the voice coil heats up, the output starts at the beginning. The sound pressure level will decrease, and then the sound distortion will increase, and eventually the voice coil will be burned. In order to effectively increase the output, the heat dissipation conditions of the voice coil must be improved on the throat of the driver. Multiple air slots use the vibration of the diaphragm to form air convection, which can effectively dissipate heat.
The extra large 4-inch voice coil and large diaphragm not only increase the power capacity, but also extend the frequency response. , Improved distortion.
Using high-performance magnetic steel material - magnetic steel. Its magnetic field strength is more than 10 times higher than traditional magnetic materials. High-efficiency magnetic steel improves the sound pressure sensitivity of the speaker. dynamic range, and also reduces weight.
High-power, low-loss high-quality crossovers
High-power high-quality crossovers are also key components that directly affect the tone. The amplifier must accurately match the characteristics of the speaker unit to obtain flat characteristics, correct crossover points and small nonlinear distortion to obtain good sound quality. ***L successfully reduced the original crossover slope to 12DB/octave It is increased to 18DB/octave to make the sound clearer and minimize the mutual interference between units. A lot of effort has been put into the design, material selection and production of the crossover used on ***L speakers. , using special four-lead resistors, ultra-low resistance inductors and precision low-loss styrene capacitors, etc.
New concept high-tech products-EON series active speakers:
p>The EON series of active speakers adopts new concept design and advanced production technology, making it the most popular, affordable, multi-purpose portable product.
The EON series speakers use high-performance magnetic material magnets, a basin frame made of aluminum instead of steel and a cabinet made of plastic instead of wood. The special and strong integrated box frame structure makes it lightweight. Greatly lightened, easy to carry, and easy to install.
EON's treble and bass units all adopt the above-mentioned new technological measures. For the first time, they also adopt reverse series differential dual voice coil technology, which makes the speaker's impedance appear "pure resistance". , so the frequency response is particularly broad and flat, and the sound is extremely clear and beautiful.
EON's built-in power amplifier heat dissipation cleverly utilizes the air flow generated by the speaker's echo hole when the diaphragm vibrates, bringing the heat outside the box, so it can be used continuously for a long time in harsh outdoor environments. 300 hours full power load test---***L's quality assurance for you.
According to the American electrician's standard AES2-1984, the speaker unit only needs to pass the test of full power load for 2 hours to be qualified. ***L will automatically increase this test standard to 300 hours. This is** *L Guarantee of user quality.
5) What output power amplifier does the speaker system need to be equipped with?
The speaker system needs to play back various music programs with high quality, so according to the properties of the music signal, its peak factor is about is 10-15DB. From the perspective of ensuring sound quality, the power amplifier should not limit any amplitude within this dynamic range, that is, the maximum output power of the power amplifier should be 5-8 times the rated power of the speaker. Although the sound quality of such a power configuration is Very good, but its investment will be very large, so the power ratio is generally set at 1-2 times the rated power of the speaker unit.
The range of 1-2 times may be too broad, but we can give you a more specific experience.
1. In some projects with lower requirements and limited investment, the power of the power amplifier is at least equivalent to the rated power of the speaker. But be very careful to keep the sound from being distorted. It seems that too small a power configuration will not damage the speaker unit, but it is not. Too little power can easily cause overload clipping, produce a large amount of harmonics, and burn out the tweeter.
2. For general engineering projects, it is recommended that the power of the power amplifier be 1.5 times. The bass part is best to exceed 1.5 times in order to obtain a sufficient sense of power.
3. For venues with extremely high requirements, such as recording studio monitoring, concert halls, etc., the ideal power is twice the speaker power. (This is consistent with one of the recommended values ??for mating standards developed by the International Electrotechnical Commission IEC).
There is no hard standard for designing power amplifiers, it all depends on the investment budget and sound quality requirements.
Audio equipment for fixed installation
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