In the sound system, the structure of the speaker is the simplest, but the role played is the most important. The speaker is the final link in the sound system and is the key part of converting electrical signals into sound signals. Due to the lack of structural components of the speaker, it leads to any lack of influence and affects the entire replay effect. The evaluation of the speaker is based on the subjective listening - the final music replay is the standard. Therefore, the following first problem arises: This is the unified problem of the technical test and subjective sound quality evaluation of the speaker. First, on the measurement and listening of the speaker Friends with certain HiFi experience will have such a consensus: this is the gap between the technical indicators of the speakers and the subjective audition. Why is this? This is going to start from the beginning, from the main technical indicators of the current speaker test. Among the technical specifications of the speaker, the most important ones are as follows: this is the frequency range, withstand power, sensitivity and phase characteristics, and transient characteristics. The frequency range, also known as the frequency response, refers to the replay range from bass to treble in the speaker. At some point, the frequency response of a pair of small civilian speakers and a pair of large monitors may be consistent; however, the perception of subjective listening is quite different. Why is this? Is it because the test is not accurate or is someone deliberately making a fake? Under normal circumstances, the above speculation is not correct, but for another reason. Reason 1: The distance between the current test standard and the actual application The current frequency response test standard still uses the standard of 1 watt-meter before many years ago. When the sound test standard was established many years ago, the speaker frequency response curve of 1 watt and 1 meter, in many cases, represents the test of full power, which is close to the actual use. The speakers of that era are basically low-power, high-sensitivity type. For the input power of 1W, it basically represents the actual working state of the small power speaker. In recent years, with the development of speaker manufacturing technology, most of the speakers have been high-power, low sensitivity. This makes the current frequency response test more and more different from the actual use. At present, most of the speakers (mainly referred to as home speakers), they are more than 50W, and some even reach 200W. The sensitivity can only reach 82~86dB. In this case, the 1 watt-meter frequency response test is still used, which will cause the test to be inconsistent with the use. Input 1W test signal, which is only 1/50~1/200 of the power of most speakers, and the actual power of these speakers is generally 15~50W, even at full power, it leads to a test itself. Deviate from the actual problem. An accurate and feasible measurement method should try to simulate the actual working state of the equipment under test. At this time, the test results are most effective. Therefore, in the frequency response test of the speaker, if a half-power frequency response test can be added, the half-power frequency response curve will have the most realistic impact on the actual operation of the speaker. For example, a small speaker, nominally 200W, will use a 100W half-power test signal to test it, and you will see a significant degradation in its low frequency and a large increase in distortion. Why is this? This is because the woofer unit is affected by the equivalent content of the speaker and by the phase-inverting tube and other factors, as well as the resonance of the box itself, which will inevitably produce the above results. Using a 1W low-power signal to test the speaker is equivalent to a whispered opera that is not professionally trained. It is not the actual working state, and the real working state is to sing loudly on the stage, so the good voice of the little scorpion and the performance on the stage are completely It is a different concept and it is two different things. Therefore, the frequency response test of adding half power to modern speakers not only has very practical guiding significance, but also has the effect of anti-counterfeiting - it can make those small speakers with a nominal 2000W completely exposed the original appearance. Reason 2: The current test standard is too loose There is another reason for the inconsistency of subjective listening and frequency response testing. This is because the current testing indicators are too loose and not strict enough. Current speaker frequency response test, based on -3 dB. In other words, the frequency at which the sound emitted from the high-frequency end and the low-frequency end is attenuated by half is used as the final frequency of the measurement. Today, with the development of tweeter production technology, a high-pitched sound of 20 kHz above mid-range has no problem. At present, the highest frequency of the world's most advanced enamel soft dome tweeter has reached 40 kHz, while the high-frequency upper limit of the metal film has reached 80 kHz. In addition, the tweeter is less affected by the speaker cabinet, so the new speaker above the mid-range will not cause problems in high frequency. For the high-frequency replay, the selection of the low-end crossover point of the tweeter, the connection with the mid-range unit is excellent, and whether there is sufficient power headroom. For a woofer, the situation is much more complicated. Although the manufacturing technology of the woofer has also been greatly developed, especially the new diaphragm material is constantly coming out, the technical specifications of the woofer are already good. However, the difference between the test indicator of the woofer and the actual indicator after it is mounted on the speaker is obvious. In some cases, an excellent woofer, mounted on a faulty speaker cabinet, will completely lose its original advantages. For example, if the design fails, the medium and low frequency resonance will be generated. This resonance will not only cause sound dyeing when the speaker is replayed, but also cause deterioration of the test curve. The test indicators of large monitor speakers are more accurate. In fact, this “quasi†word does not mean correctness here, but means that the test indicators are closer to subjective listening. Since the above mentioned the current lack of 1 watt? 1 meter test method, then in the current test standard, which speaker's technical test is the closest to the subjective listening result? The answer is as follows: This is the large-scale monitoring Speakers and large civilian speakers of better quality. The result is why it is a large speaker? There are three reasons. One is that the large speaker has a large volume inside the box, so the low frequency response in actual work is limited by the volume of the box. The second is that large-sized speakers have higher power consumption and larger power margin, and the possibility of overload distortion in operation is relatively small. Especially for large monitor speakers, the remaining power margin is very large, and there is no possibility of overload distortion. The third is that the woofer of a large speaker is relatively large in diameter. When the same bass is produced, the stroke of the unit is small and the distortion is relatively small. Second, on the specific misunderstanding of the speaker 1. The statement of the long stroke of the big voice coil is not accurate enough I often hear people mention the long stroke of the big voice circle. The so-called big voice coil means that the diameter of the voice coil is relatively large, which is well understood. But the long journey is another matter. Because long strokes are only a relative concept, under the premise of true comparability, the larger the voice coil, the shorter the stroke can be, and the longer it is impossible. Another factor in determining the woofer's travel is the fixed-core slats attached to the bottom of the speaker cone. Because the speaker cone is only fixed by two points of the folding ring and the fixed core piece, the speaker cone can be reliably moved back and forth. The fixed core piece is made of rubberized cotton fiber and synthetic material. The elastic range of the cored piece is limited. Therefore, the current limit of the woofer stroke is not a rubber folding ring, but a fixed core piece. Since the diameter of the core piece cannot be made very large, the diameter of the rubber ring will never be reached or exceeded, so the diameter of the voice coil is larger, and the diameter of the core piece is limited, leaving a given core piece The smaller the range of activities, in other words, the smaller the stroke of the speaker. Only when the voice coil is small, the range in which the fixed core piece can move is relatively large. Therefore, the large voice coil and the long stroke woofer are only a relative statement and are not accurate. 2. Long-stroke small-caliber woofer can't replace large-caliber woofer It is often said that a small-caliber long-stroke woofer can emit enough bass as long as the stroke is long enough. This is a wrong view. In theory, as long as the same unit of time, driving the same volume of air can produce the same level of sound pressure. But specific to the woofer, this is unrealistic. Excessive travel and excessive air compression ratio can cause severe distortion of the replayed sound. For a large-diameter woofer (with a diameter of 200 mm or more), when a sufficient sound pressure is achieved, the stroke of the speaker cone is large and the stroke is short, the distortion during replay is small, and the sound is good. Even in an ideal state, the current speaker sound distortion can only be 1%. When working in a small-caliber, long-stroke woofer, the distortion increases rapidly due to excessive travel, which is an illusion that quality is not guaranteed. Therefore, for most small and small-caliber speakers, even the low-power test low-frequency of the speaker can be used, but in actual use compared with large-scale large-caliber speakers, the gap is still quite large, which is the essential difference. So when there are conditions, it makes sense to choose a large speaker. 3. Low-sensitivity speakers have different sounds There was a time when there was a saying that this is a low-sensitivity speaker sound. In fact, this is just a one-sided and unscientific statement. The main factors that determine the sound quality of the speaker are frequency response, transient characteristics, damping characteristics and power handling. Independent of sensitivity. In other words, for a speaker that is also subjected to the same power, at the same replay volume, the lower the sensitivity of the speaker, the greater the input power required, the closer it is to the overload, and the distortion will increase relatively. Twenty years ago, the technical quality of the speaker unit itself had not reached a good level. When making a speaker, only a lot of attenuation correction circuits can be added to the divider. The end result is that the frequency response curve is straight, but the sensitivity is greatly reduced, only about 82dB. In this case, it is usually necessary to use a high-power amplifier to better drive low-sensitivity speakers. However, under high-power driving, low-sensitivity small speakers are prone to overload distortion and cannot even play some large dynamics. musical work. Due to the development of audio technology, there are a variety of monitors and Hi Fi-class speakers with more than 100dB sensitivity, and the highest sensitivity is close to 110dB. 4. The sound-absorbing cotton in the speaker does not represent the quality grade. “The speaker without sound-absorbing cotton is a low-end speakerâ€, this statement is not accurate. There is no sound absorbing material in the low-end speakers, which is a reality. In the set machine and the cheap finished speaker, basically no sound absorbing material is filled. Therefore, some people have come to the conclusion that there is no sound-absorbing cotton in the low-end speakers, and adding filler materials to the low-end speakers can improve the replay effect. In fact, there is no causal relationship between the above conclusions, and there is no inherent connection. The sound absorbing material plays only two roles in the speaker. One is to eliminate some resonance and dyeing of the speaker box; the other is to appropriately reduce the volume of the speaker. It doesn't matter which grade the speaker belongs to. Some people think that adding filler to the speaker is a versatile medicine, which is a big mistake and a mistake. First, as long as the cabinet design of the speaker is reasonable, there is no obvious resonance, and the box is large enough to make a high-quality speaker without adding filler material. There are many examples of such success in the field of speaker production around the world. No filler material is added to the speaker cabinet, which is good for the transient characteristics of the speaker. A carefully designed and carefully processed speaker has basically reached an ideal state at the factory. In this case, arbitrarily changing the presence or absence of the filling material in the speaker will have a lot of impact on the replay of the speaker, and most of these effects are negative. Excessive fillers can cause sounds during replay, poor transient characteristics, and lack of energy. Although the curve will improve during the test, the sound performance will deteriorate when subjectively listening. One thing must be clear, this is the speaker is listening, not watching. 5. About the speaker's crossover In the speaker's crossover, there are only three types of components: this is the inductor, capacitor and resistor. The function of the resistor is the attenuator, which is used to balance the sound ratio of each frequency band. When you choose, you only need to have enough power. High-pitched attenuation for small speakers In terms of resistance, the resistance of the metal film is better. The function of the inductor is to filter out the high notes and strobe the bass. In recent years, a large number of inductive coils wound with shaped enameled wires have been popular. Among them are stranded enameled wires, hexagonal enameled wires and ribbon enameled wires. The inductor coil of each profiled wire is said to have some kind of power. But is this really the case? Actually it is not. There are only three requirements for the inductor coil for the speaker. One is that the inductance value is accurate; one is its own DC resistance is low; one is not easy to produce saturation distortion. As far as the value is accurate, as long as it is used in the production process, it is only necessary to measure and calibrate with high-precision instruments. In order to reduce the inductance of the inductor itself, it is necessary to increase the conductivity of the enameled wire itself. The electrical conductivity of the enameled wire itself and their cross-sectional area are inextricably linked to the cross-sectional shape. When the wire has a circular, square, or hexagonal cross section, it is most efficient. Specifically, the winding of the inductor coil and the hexagonal cross-section of the enameled wire can effectively reduce the gap between the turns and improve the efficiency of the inductor. Especially for multi-layer coils with a large number of turns, the improvement effect will be very obvious. However, when a hexagonal enameled wire is used, the manufacturing cost is also greatly increased. Therefore, if it is not used in a very high-end occasion, the use of a circular oxygen-free copper enameled wire with a purity of 4N or more, the effect is already quite good. When choosing the wire diameter of the enameled wire, there is no way that the wire diameter is as thick as possible. As long as the inductance is satisfactory, the DC resistance is about one-tenth of the woofer's voice coil DC resistance. The DC resistance of the inductor is too large, which directly affects the low-frequency damping characteristics of the speaker; the DC resistance of the inductor is too small, and the manufacturing cost is unnecessarily increased. As for the choice of the divider capacitor, there will never be a capacitor that will make a fundamental change in the replay of the speaker. For those who make their own speakers or want to improve the finished speaker, you must first have a clear purpose. When making a speaker, you should choose the level of the crossover capacitor according to the investment of the speaker unit. For example, if you buy a tweeter with a few tens of dollars, you can spend 20 yuan to choose a capacitor for it. You might as well buy a high-pitched head of one hundred yuan, and choose a crossover capacitor of a few yuan to get benefits. If you have bought a tweeter of 300 yuan and spend tens of dollars to buy a crossover capacitor, this is the right thing to do. For audio capacitors, different brands and different materials have different effects on replay. However, these intrinsic and meticulous differences are better reflected in the tweeters above the mid-range. For the frequency division capacitors in the low frequency band, the main values ​​are accurate capacitance, withstand voltage and reliability. Relative to the treble crossover capacitor, the requirement can be relatively low, because the high capacitance of large capacitance is too expensive. Often in a state that is not worth the loss after use. 6. The advantages and disadvantages of NdFeB For speaker units, magnetic materials are their bones and are the basis of their power. Making a speaker unit from a material with a high magnetic energy product is a good way to increase the sensitivity of the speaker. But not the only way. An important criterion for the magnetic material of the speaker, especially the magnetic material of the high-power woofer, is that the thermal stability must be good. The magnetic energy product of the neodymium iron boron magnetic material is large. But it also has fatal injuries. First, it is easy to oxidize itself; second, its thermal stability is poor. NdFeB magnetic materials have a very low Curie temperature, and at 80 ° C, their performance will drop to 80% of the reference temperature (reference temperature is 24 ° C). This explains the problem: if it is a neodymium iron boron woofer that has not been specially heat-dissipated, it will cause a shortage of bass due to the increase in temperature during high-power operation. This variation in tone is clearly noticeable to most music lovers. Therefore, at present, most foreign speaker manufacturers basically use NdFeB materials as magnetic materials for tweeters and take more effective heat dissipation measures. NdFeB magnetic materials are rarely applied to the manufacturing process of the woofer. After years of HiFi practice, most people can basically distinguish between the small differences caused by different audio signal lines for replaying sounds. However, due to the poor thermal stability of the NdFeB magnetic material, the frequency response variation of the woofer above 10% will be a big regret. 7. Using the demagnetization method to improve the sound quality is not desirable A while ago, there was a popular saying that the demagnetization method improved the sound quality. The so-called demagnetization method refers to the adsorption of some large iron nails on the speaker unit magnet of the finished speaker. The magnetic properties of the unit itself are dispersed, which reduces the sensitivity of the speaker unit and changes the original Q value. Using the demagnetization method to adjust the replay effect of the speaker will play a certain role. However, the demagnetization method is only suitable for those speakers who have heard the sound dry and tight. It is impossible to apply to most occasions. For the speaker that can improve the broadcast by the demagnetization method, the method of adjusting the sound absorbing material in the speaker and adjusting the inverted tube of the speaker can also achieve the purpose, and the sensitivity of the speaker is not lost. 8. The frequency response curve of the ideal small speaker Since the bass replay capability of the small speaker is most restricted by the speaker cabinet, the gap between the frequency response test curve and the subjective listening is also the largest, which also presents a compromise and new requirement for the frequency response test curve of the small speaker. The requirement is that the low end of the frequency response is not the pursuit of lower digital effects. It is not desirable to pursue low-frequency extensions below 35 Hz or more, as for small bookshelves using small-diameter woofers (6.5 inches or less). The speaker, its test frequency response below 40Hz, has little meaning in practical applications. However, if the low-end frequency of the frequency response test is changed to 50 Hz, the curve becomes a curve with a small peak at the low end and a slight decrease at the high frequency end, which will greatly improve the replay when the test is not exceeded. Sound effects. There are still a lot of misunderstandings about the speakers. It is impossible to make it clear in a text. With the development of science and technology, out of the old misunderstanding, there will be new misunderstandings. Therefore, if you want to take a detour, you must truly connect with the international community and continue to learn.
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