Get out of the misunderstanding of speakers

In the sound system, the structure of the speaker is the simplest, but the role it plays is the most important. The sound box is the final link in the sound system, and it is the key part to convert the electrical signal into the sound signal. Because there are not many structural components of the speaker, it leads to any deficiency and affects the entire replay effect. The evaluation of the speaker is based on subjective listening-the final quality of the music replay as the standard. Therefore, the following first problem also arises: This is the unified problem of the technical testing of speakers and the evaluation of subjective sound quality.
1. Friends who have certain HiFi experience in speaker measurement and listening will have such a consensus: This is the gap between the speaker's technical indicators and subjective audition.
Why is this happening? This is to start from the beginning, from the main technical indicators of the current speaker test.
Among the technical indicators of speakers, the most important ones are the following: this is the frequency range, withstand power, sensitivity and phase characteristics, and transient characteristics.
Frequency range, also known as frequency response, refers to the range of replay from low to high in the speaker. At some times, the frequency response range marked by a pair of small civilian speakers and a pair of large monitor speakers may be the same; however, the subjective listening experience is quite different. Why is this? Is the test inaccurate or someone deliberately made a fake? Under normal circumstances, the above speculation is wrong, but there are other reasons.
Reason 1: The distance between the current test standard and the actual application. The current frequency response test standard still uses the 1 watt · meter standard many years ago. When the audio test standard was formulated many years ago, the frequency response curve of the speaker under 1 watt and 1 meter, in many cases, represents the full power test, which is close to the actual situation in use. The speakers of that era were basically of low power and high sensitivity. For the input power of 1W, it basically represents the actual working state of the low-power speaker. In recent years, with the development of speaker manufacturing technology, most speakers have become more powerful and less sensitive. This makes the gap between the current frequency response test and the actual use more and more. At present, most of the speakers, mainly referring to home speakers, their withstand power exceeds 50W, and some even reach 200W. The sensitivity can only reach 82 ~ 86dB.
In this case, the frequency response test of 1 W · m is still used, which will cause the test to be inconsistent with the use. The input of a 1W test signal is only equivalent to 1/50 to 1/200 of the power of most speakers, and the actual power of these speakers is generally 15 to 50W, and it will even reach full power at peak, which leads to a test itself. Problems that deviate from reality.
An accurate and feasible measurement method should try to simulate the actual working state of the tested equipment, and the test results are most effective.
Therefore, if a half-power frequency response test can be added during the frequency response test of a speaker, then this half-power frequency response curve will have the most realistic impact on the actual work of the speaker.
For example, a small speaker nominally 200W, when using a 100W half-power test signal to test it, you will see its serious deterioration in low frequency and a large increase in distortion.
Why is this the case? This is because the woofer unit is restricted by the equivalent volume of the speaker and the influence of factors such as the inverter tube, and the resonance of the cabinet itself increases, which will inevitably produce the above results.
Testing the speakers with a low-power signal of 1W is only equivalent to a vocal sing opera that has not been professionally trained. It is not the actual working state, and the real actual working state is to sing loudly on the stage, so the good voice of the small voice and the performance on the stage are completely It is a different concept, two different things.
Therefore, adding a half-power frequency response test to modern speakers not only has a very practical guiding significance, but also has the effect of counterfeiting-it can make those nominal 2000W small speakers completely expose their true colors.
Reason 2: The current test standards are too loose. The subjective listening and frequency response tests are not uniform. There is another reason. This is that the current test indicators are too loose and not strict enough.
The current speaker frequency response test is based on -3 dB. In other words, the final frequency is the frequency at which the sound emitted by the high-frequency end and the low-frequency end is attenuated by half.
For the production technology of the tweeter unit that is constantly developing and mature today, it is no problem for a mid-range or higher tweeter to produce a 20 kHz tweeter. At present, the world's most advanced silk film soft dome tweeter has reached a high frequency of 40 kHz and the metal film tweeter's high frequency limit has reached 80 kHz. In addition, the tweeter unit is less affected by the speaker box, so the new speakers above the mid-range will not have problems with high frequencies. The greater impact on high-frequency replay is limited to the selection of the low-end crossover point of the tweeter unit, whether the connection with the midrange unit is excellent, and whether there is sufficient power margin.
The situation is much more complicated for the woofer. Although the manufacturing technology of the woofer has also made great progress, especially the new diaphragm materials are constantly coming out, the technical indicators of the woofer are already good. However, the gap between the test index of the woofer and the actual index after it is installed on the speaker is obvious. Sometimes, an excellent woofer is installed on a sound box with a lot of problems, which will completely lose its original advantages.
For example, a poorly-designed cabinet will produce severe mid-to-low frequency resonance. This resonance will not only cause sound staining when the speaker is replayed, but also cause deterioration of the test curve.
Speaking of the pros and cons of the low-frequency test curve, I mentioned that the current test standards are too loose and not strict enough.
As shown in Figure 2a and Figure 2b, the low frequency response of the two curves can be finally measured as 30Hz, but the performance of replaying bass is very different. Why is there a clear difference on the curve and the result after the measurement and interpretation is the same, this is because the standard of -3dB as the interpretation is too loose. If the measurement standard is -2dB or -1dB, then the measurement results of the two curves are very different.
It is generally believed that an audio frequency response with an attenuation within -3dB is an effective frequency response. Too much attenuation, its role in replay is basically overwhelmed and invalid. However, a lot of practice has proved that the human ear after rigorous training can achieve a very high resolution and accuracy. The human ear can clearly distinguish the difference in replay tone caused by the difference of a few dB. Therefore, if the speaker is tested for frequency response, in addition to the standard result of -3dB, it can also provide a test result of -1dB, which will provide a more practical reference for the speaker.
The test indicators of large monitor speakers are more "quasi". In fact, the word "quasi" here does not mean correct, but means that the test indicators are closer to the subjective listening. Since the above mentioned that the current test method of 1 watt · 1 meter is inadequate, then within the scope of the current test standard, which speakers are the closest to the subjective listening results? The answer is as follows: Speakers and large civilian speakers with better quality.
Why the result is a large speaker? There are three reasons. One is that the volume of the large speaker cabinet is large, so the low frequency response in actual work is limited by the volume of the cabinet. The second is that the large speakers have a higher power capacity and a larger power margin, and the possibility of achieving overload distortion during work is relatively small. Especially for large monitor speakers, the power margin left is very large, and there is no possibility of overload distortion at all. The third is that the caliber of the woofer unit of the large speaker is relatively large. When producing the same bass, the unit's stroke is very small, and the distortion is relatively small.
Second, the specific misunderstandings about the speaker 1. The long stroke of the large voice coil is not accurate enough. I often hear people mention the long stroke of the large voice coil. The so-called large voice coil means that the diameter of the voice coil is relatively large, which is easy to understand. But long trips are a different matter. Because long travel is just a relative concept, under the pre-comparison of real comparability, the larger the voice coil, the shorter the travel can be and the longer it is impossible.
It can be seen from Fig. 3a and Fig. 3b that the large voice coil has a short stroke. There are two key factors that determine the length of the woofer's travel. One is whether the folding ring (mostly made of rubber, foam plastic and treated cloth) glued to the outer ring of the speaker cone is wide enough and has sufficient elastic range. In theory, the wider the folding ring, the stronger the elasticity, and the longer the stroke obtained. But the folding ring cannot be too large and the elasticity cannot be too strong. If the folding ring is too large, the effective driving area of ​​the unit will be reduced. If a 6.5-inch woofer is too large, it can only function as a 5-inch woofer. There is no longer a small-diameter unit with a long stroke, and it is impossible to emit a low frequency with a sufficiently low frequency and practicality.
Another factor that determines the travel of the woofer is the fixed core sticking piece attached to the bottom of the speaker cone. Because the speaker paper cone can be reliably moved back and forth only through the two points of the folding ring and the fixed core support piece. The fixed core supporting piece is made of cotton fiber and synthetic material with glue added. The elastic range of the fixed core piece is limited. Therefore, it is not the rubber folding ring that restricts the travel of the woofer, but the fixed core support piece. Since the diameter of the fixed core support piece cannot be made large, it will never reach or exceed the diameter of the rubber fold ring, so the larger the diameter of the voice coil, and the diameter of the fixed core support piece is limited, leaving the fixed core support piece The smaller the range of motion, in other words, the smaller the travel of the speaker. Only when the voice coil is small, the movable range of the fixed core support is relatively wide. Therefore, the large voice coil and long-stroke woofer are only a relatively speaking statement, and are not accurate.
2. Long-stroke small-caliber woofer cannot replace large-caliber woofer. It is often said that small-caliber long-stroke woofer can produce enough bass as long as the stroke is long enough. This is a wrong view. In theory, as long as the same volume of air is driven in the same unit time, the same level of sound pressure can be generated. But as far as the woofer is concerned, this is unrealistic. Because of excessive travel and excessive air compression ratio, the replayed sound will be seriously distorted. For a large-diameter woofer (diameter above 200mm), when sufficient sound pressure is reached, the driving area of ​​the speaker cone is large and the stroke is short, the distortion during replay is small, and the sound is good. Even in a more ideal state, the current speaker sound distortion can only achieve 1%. When working with a small-diameter, long-stroke woofer, the distortion increases rapidly due to the excessive stroke, which is an illusion that the quantity is not guaranteed. So for most small and small-caliber speakers, even the low-power test low-frequency of the speakers is OK, but in actual use compared with large-diameter speakers, the gap is still quite large, it is an essential difference. So when conditions permit, it makes sense to choose large speakers.
3. The sound of low-sensitivity speakers is different. There was a time when such a saying was popular, that is, the sound of low-sensitivity speakers is good. In fact, this is just a one-sided and unscientific statement.
The main factors that determine the sound quality of the speaker are only frequency response, transient characteristics, damping characteristics and withstand power. It has nothing to do with sensitivity. In other words, for speakers with the same power, under the same replay volume, the lower the sensitivity of the speaker, the greater the input power required, the closer to overload, the distortion will increase relatively.
Twenty years ago, due to the technical quality of the speaker unit itself has not reached a relatively good level. When making speakers, a lot of attenuation correction circuits can only be added to the crossover. The final result is that the frequency response curve is straight, but the sensitivity is greatly reduced, only reaching about 82dB. In this case, it is usually necessary to use a high-power amplifier to better drive low-sensitivity speakers, but under high-power driving, low-sensitivity small speakers are prone to overload distortion and even cannot play some large dynamics. musical work.
Due to the development of audio technology, there are currently a variety of models with monitor levels of over 100dB and Hi-Fi speakers, and the highest sensitivity is close to 110dB.
4. The sound-absorbing cotton in the speaker does not represent the quality grade. "Speakers without sound-absorbing cotton are low-end speakers." This statement is inaccurate.
There is no sound-absorbing material in the low-end speakers, which is a reality.
In packaged machines and cheap finished speakers, basically no sound-absorbing material is filled. Therefore, some people have come to the conclusion that there is no sound-absorbing cotton in low-end speakers, and adding filler materials to low-end speakers can improve the replay effect.
In fact, the above conclusion has no causality, and there is no inherent relationship.
The sound absorbing material only plays two roles in the speaker, one is to eliminate some resonance and staining 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 fillers to the speakers is a panacea, which is wrong.
First, as long as the cabinet design of the speaker is reasonable and there is no obvious resonance, and the cabinet is large enough, high-quality speakers can be made without adding filler materials. There are many examples of such success in the world of speaker production. No filler material is added to the speaker box, which is good for the transient characteristics of the speaker.
A speaker that has been carefully designed and carefully manufactured has basically reached a relatively ideal state when it leaves the factory. In this case, arbitrarily changing the presence or amount of filler material in the speaker will have many effects on the replay of the speaker, and most of these effects are negative.
Too much filler will cause the sound of the replay to be fleshy, the transient characteristics are poor, and there is weakness. Although the curve will be improved during the test, the sound performance will deteriorate when subjectively listening. One thing must be clear, this is that the speaker is listening, not watching.
5. About the frequency divider of the speaker In the frequency divider of the speaker, there are only three types of components: this is the inductance coil, capacitor and resistance.
The function of the resistor is an attenuator, which is used to balance the sound ratio of each frequency band. As long as the power is large enough. For the high-frequency attenuation resistance of small speakers, the resistance effect of the metal film will be better.
The role of the inductance is to filter out high-pitched sounds, strobe bass. In recent years, many kinds of inductive coils wound with special-shaped enameled wires have become popular. Among them are stranded enameled wire, hexagonal enameled wire and ribbon enameled wire, etc. (Figure 4). The inductance coil of each special-shaped wire is said to have a certain magical power. But is this really the case? Actually not.
There are only three requirements for inductive coils for speakers. One is that the inductance value is accurate; one is that its own DC resistance is low; one is that it is not easy to produce saturation distortion.
Regarding the accuracy of the value, as long as the high-precision instruments are used to measure and calibrate one by one during the production process.
In order to reduce the self-resistance of the inductive coil, it is necessary to improve the conductivity of the enameled wire itself. The electrical conductivity of the enameled wire itself and their cross-sectional area are closely related to the cross-sectional shape. When the cross section of the wire is round, square, or hexagonal (Figure 5a, b), the efficiency is the highest.
When it comes to winding inductor coils, hexagonal cross-section enameled wires can effectively reduce the gap between turns and improve the efficiency of the inductor. Especially for multilayer coils with a large number of turns, the improvement effect will be very obvious. However, when the hexagonal enameled wire is used, the production cost will also be greatly increased. Therefore, if it is not used in very high-end occasions, the use of round oxygen-free copper enameled wire with a purity of more than 4N will have a very good effect. When choosing the wire diameter of the enameled wire, there is no saying that the thicker the wire diameter, the better. As long as the inductance meets the requirements, its DC resistance is about one tenth of the DC resistance of the woofer voice coil. 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 it will unnecessarily increase the production cost.
As for the selection of the crossover capacitor, there will never be a capacitor that will fundamentally change the replay of the speaker. For those who make their own speakers or want to improve the finished speakers, they must first have a clear purpose. When making a speaker, the grade of the crossover capacitor should be selected according to the investment of the speaker unit.
For example, if you buy a tweeter with dozens of yuan, it would be worthless to spend another 20 yuan on matching capacitors. You might as well buy a tweeter for one hundred yuan, and choose a crossover capacitor of a few yuan for one. If you have bought a tweeter with a price of 300 yuan, and you need to buy a crossover capacitor for tens of dollars, this is the right one.
For audio capacitors, different brands and different materials have different effects on replay. But these internal and subtle differences can only be better reflected in the tweeters above the mid-range. For low-frequency frequency-dividing capacitors, it is mainly based on accurate capacitance, withstand voltage and reliability. Compared with treble crossover capacitors, the requirements can be relatively lower, because high-end capacitors with large capacitance are too expensive. Often in a state of gains and losses after use.
6. The advantages and disadvantages of neodymium iron boron For the speaker unit, the magnetic material is their skeleton and the basis of their power. Selecting materials with high magnetic energy product to manufacture the speaker unit is a good way to improve the sensitivity of the speaker. But it is not the only way.
For the magnetic material of the speaker, especially the magnetic material of the high-power woofer, there is an important criterion that the thermal stability must be good. The magnetic energy product of NdFeB magnetic material is large. But it also has fatal injuries. First, it is easy to oxidize itself; second, its thermal stability is poor. The Curie temperature of the NdFeB magnetic material is very low. At 80 ° C, its performance will drop to 80% of the reference temperature (the reference temperature is 24 ° C). This illustrates such a problem: if it is a NdFeB woofer that has not been subjected to special heat dissipation treatment, when it is working at high power, due to the effect of temperature increase, it will cause insufficient bass. This variation of timbre is clearly noticeable to most music lovers.
Therefore, at present, most foreign speaker manufacturers basically use the neodymium iron boron material as the magnetic material of the tweeter, and take more effective heat dissipation measures. NdFeB magnetic materials are rarely applied to the manufacturing process of woofer.
After many years of HiFi practice, most people can clearly distinguish the slight difference caused by different audio signal lines to the replay tone. However, due to the poor thermal stability of the neodymium iron boron magnetic material, the frequency response variation of the bass unit higher than 10% will be a big regret.
7. It is not advisable to use the demagnetization method to improve sound quality a while ago. It has been popular that the demagnetization method improves sound quality. The so-called demagnetization method refers to the adsorption of some large iron nails on the magnet of the speaker unit of the finished speaker. The magnetism of the unit itself is 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 that originally sound dry and tight. It is impossible to apply to most occasions. For speakers that use the demagnetization method to improve the broadcast, the method of adjusting the sound absorption material in the speaker and adjusting the inverter tube of the speaker can also achieve the purpose, and the sensitivity of the speaker will not be lost.
8. Frequency response curve of ideal small speakers Because the bass replay capability of small speakers is most restricted by the speaker cabinet, the gap between the frequency response test curve and the subjective listening sound is also the largest, which is proposed for the frequency response test curve of small speakers There is a compromise and new requirements. This requirement is: the low end of the frequency response should not be too low for the effect of digitalization, and the extension of the low frequency end should not be deliberately pursued below 35Hz or more, because for small bookshelves that use small-caliber woofer (6.5 inches or less) Type speaker, its test frequency response below 40Hz is of little significance in practical applications. However, if the low-end frequency of the frequency response test is changed to 50 Hz, and the curve is changed to a curve with a small peak at the low end and a slight decrease at the high-frequency end (Figure 6), it will be greatly under the previous question that does not exceed the test standard. Improve the sound effect during replay.
With the small speaker with the curve in Figure 6, when replaying music, you will feel that the bass is relatively full and powerful, and the replay sound is kind and sweet.
There are actually many misunderstandings about speakers, and it is impossible to make it clear in a text. With the development of science and technology, the old misunderstandings have come out and new ones will be encountered. Therefore, if you want to avoid detours, you have to be truly in line with international standards and keep learning. var check_allow = "/d/Api/iscantalk.html"; var add_url = '/ d / article / write /'; function CheckLogin () {now_uid = ''; var ElecfansApi_checklogin = '/ webapi / passport / checklogin'; var logout_url = "{: U ('Login / logout')}"; var logout_url = 'http://bbs.elecfans.com/member.php?mod=logging&action=logout&refer=front'; $ .get (ElecfansApi_checklogin, function (data, textStatus) {if (data! = "") {EchoLoginInfo (data); CheckEmailInfo (data); data = $ .parseJSON (data); now_uid = data.uid; / * var login_content = 'write an article