1. What is a coaxial speaker? The general speakers, tweeters and woofers are arranged flat on the panel of the speaker, so their vocal centers cannot coincide with one point, so the difference between the treble and the bass reaching the listener is different. The phase deviation thus affects the correct restoration of the sound image. The coaxial speaker uses a coaxial unit. This unit is actually a combination of a tweeter and a woofer. The treble is placed subtly at the center of the bass diaphragm, thus ensuring that the acoustic center of the high and low frequencies is the same point. , thus solving the problem of phase deviation. The two most famous commercial coaxial speakers are British products, one is Tannoy (Tianlang) using the "Tulip" coaxial unit, and the other is KEF using Uni-Q coaxial unit. 2. What is the dumbbell type unit arrangement? That is, the tweeter is clamped in the middle of two identical middle/woofer units, which is similar in form to two large and small dumbbells. The dumbbell arrangement can obtain the sound effect similar to the point source, which is good for stereo image positioning, so this design is popular recently. 3. What is a double-line sound? A conventional speaker has only one set of input terminals. The full-band signal from the amplifier is sent to the speaker with a set of speaker cables. The high and low frequencies are separated by the crossover inside the speaker. Bi-wiring uses two sets of speaker cables to connect the amplifier and the speakers, so that the high and low sounds separate the roads, and everyone does not involve each other. The two-line split requires that the crossover's treble channel be separated from the bass channel's input, so the speaker must provide two sets of posts. Of course, the speaker with double-line sound can also be used in the conventional single-wire connection. Just use the metal short-circuit piece supplied with the box to connect the two sets of terminals into one group. Similar to the two-line crossover, if you use three sets of speaker cables to transmit the treble, midrange and bass, the connection is called Tri-wiring. However, the three-line crossover is not as common as the two-line crossover. 4. Is the double-line crossover better than the regular connection? The main reason for the two-line crossover is that some speaker cables are suitable for transmitting low frequencies, and some are suitable for transmitting high frequencies. If they are transmitted separately, the corresponding wires can be selected according to different needs to achieve the most ideal effect. However, this view is only a statement. Some people think that the double-line sounds do more harm than good. For example, the famous speaker factories Dynaudio and Thiel insist on not using double-line sound. They think that the transmission characteristics of different wires are inconsistent and will destroy high. The consistency of the bass phase, if you use the same line, then why bother? 5. Why is the bass of the larger speaker usually better? The low frequency lower limit of the speaker is closely related to two factors, one is the resonant frequency of the speaker unit, and the other is the volume of the box. In the case of no boxing, the low-frequency resonant frequency of the woofer is generally considered to be the lower limit of the effective frequency response of the unit. The larger the aperture, the lower the resonant frequency is generally, so the use of a large horn is beneficial to restore a lower low frequency. In addition, the larger diaphragm area can drive more air with the same amplitude, and it is easy to get more low-frequency sense. When the speaker unit is boxed, its resonant frequency will increase due to the air stiffness in the box. The larger the volume of the box, the smaller the effect of the air on the unit, and the smaller the resonance frequency will be, which is beneficial to obtain a lower Integrated low frequency response. On the one hand, the large speaker is easy to use the large-diameter woofer, on the other hand, it has a larger cabinet volume, so the low frequency is usually better. 6. What are the main performance indicators of the speaker? There are many technical indicators for objectively measuring the performance of the speakers. We often see in the catalog or speaker manuals: frequency response, impedance, sensitivity, maximum load power and maximum output sound pressure level. The frequency response indicates the relationship between the sound pressure level of the speaker output and the frequency. If drawn, it is a function curve with the frequency as the abscissa and the output sound pressure (or the decibel of the sound pressure) as the ordinate. The overall trend of this curve in the mid-range is horizontal, and of course there may be many small fluctuations in the middle due to the imperfect system. At the low frequency end and the high frequency end, the curve shows a downward trend, and the output of the speaker is reduced. Usually, the two points of the low-frequency end and the high-frequency end output are 3 dB lower than the middle horizontal section, and the low-frequency cut-off point and the high-frequency cut-off point are obtained. The frequency band between these two points is the frequency response range of the speaker. Obviously, the wider the frequency response range, the better, so that the wider range of the music signal can be restored. For the current speaker, the high frequency end is not a problem, it has already reached the upper limit of 20 kHz of audio, and some products are far beyond. The difficulty lies in the low frequency end. Generally, the bookshelf box reaches 50-60 Hz, and the floor box reaches 30-40 Hz. Very good. In addition, the flatter the curve within the frequency response range, the smaller the fluctuation, the better, which means that the speaker can reproduce all the frequency signals in the frequency band without discrimination, and there is no distortion of the balance. The impedance is, in layman's terms, the magnitude of the resistance to the input current signal, in ohms (Ω). The most common impedance values ​​for speakers are 8Ω, 4Ω and 6Ω. Of course, there are other values ​​such as 3Ω, 5Ω, 10Ω, etc., but they are not common. Need to specify: the impedance of the speaker is only a nominal value, the actual impedance of the speaker varies with frequency, such as the nominal 8Ω speaker, the impedance is only 8Ω at some frequency points, and 10Ω at other frequencies. 20Ω, other frequencies may be as low as 6Ω or 4Ω. The impedance vs. frequency characteristics can be seen clearly on the impedance plot of the speaker, which increases the difficulty of driving the amplifier. Sensitivity is a measure of the electro-acoustic conversion efficiency of a speaker. The unit is dB/W/m. It means the sound pressure level that can be obtained 1m away from the speaker axis when inputting 1W power, such as sensitivity of 90dB/W/m. The speaker indicates that the input power of 1W can get a sound pressure level of 90dB 1m away from the front of the speaker. A speaker with high sensitivity saves the power of the amplifier and should be considered an advantage. However, sometimes sensitivity and other performance indicators are not easy to balance. On balance, it is often preferred to sacrifice a little sensitivity for better performance. This is because high-power amplifiers are common, prices are not too high, and sensitivity is low. A big problem. The maximum carrying power is the safety indicator of the speaker, indicating the input power that the speaker can withstand for a long time. The input below this value is obviously safe. If it exceeds this limit for a long time, it is easy to overheat the voice coil. The maximum carrying power indicator provides a reference for us to use the speaker safely, but we should also pay attention to the premise of “long timeâ€. It is permissible to exceed the maximum carrying power for a short time. For example, there are many short-lived peaks in the music signal, and its power intensity. More than a few times or even tens of times the average power, but the duration is very short, that is, fleeting, playing such a signal, as long as the average power does not exceed the maximum load value of the speaker, there is no problem at all. The maximum output sound pressure level It means that the maximum output capacity of the speaker in the case where the distortion does not exceed a certain standard. The popular saying is that this speaker can make a maximum sound. Generally, the maximum output sound pressure level of a home speaker is about 100dB~110dB, and a few high output speakers can reach about 120dB. Obviously, the higher the output sound pressure level, the better. If this index is too low, dynamic compression is easy. 7. What is the standard for evaluating the sound quality of a speaker? A truly outstanding speaker should have both excellent objective performance indicators and good subjective listening evaluation. Excellent performance metrics include wide and flat frequency response, low distortion, fast transient response, high sound pressure output capability, high power carrying capacity, proper impedance characteristics, and reasonable sensitivity. And what is a good subjective listening evaluation is an "art", and everyone's standards are not the same. In theory, since the speaker is a part of the sound system (and the final link that affects the quality of the sound quality), it should be absolutely faithfully restored. The speaker itself does not have any personality, and can not carry out any of the original music signals. Distortion or modification of landscaping, if it meets or approaches such a standard, it is a good speaker. This is the so-called "realism" view. However, some people think that since the speaker is used to reproduce music, then the sound is not good to listen to is the standard for checking the sound quality of the speaker. This is the so-called "Aesthetic" view. "Aesthetic" allows the speaker to properly retouch the music signal, and does not care whether the technical indicators are perfect, as long as the sound is "good". The "Aesthetic" view is more suitable for us to listen to music as a fan of entertainment, but there is no uniform standard for what is "good", and blindly pursuing good or disregarding performance is easy to fall into misunderstanding. Therefore, objectively speaking, even a good speaker approved by the “beauty†should be based on the premise of ensuring basic performance indicators. Can an 8.4Ω speaker be connected to an 8Ω amplifier? This is a very common problem and a typical problem with conceptual errors. The statement of "8 ohm power amplifier" is not correct in itself. The questioner may see that some power amplifiers are marked with the words "100W/8Ω", and they think that the output impedance of this power amplifier is 8Ω. In fact, it is a misunderstanding and correct. The explanation is: with 8Ω load as the test condition, the output power of this amplifier is 100W. Whether the transistor or the tube machine is a constant voltage output power amplifier, the output impedance is very small. The transistor machine is generally below 0.1Ω, and the tube machine is higher, but generally it is below 1Ω instead of 8Ω. Transistor amplifiers have a strong load capacity. In principle, speakers with any impedance can be used. Of course, the impedance should not be so low that the amplifier can not be used or even overloaded. For example, connect a pair of 2Ω speakers (if any). Most medium and small power amplifiers will not be able to eat. For tube amps, there is a problem of “best loadâ€, that is, the performance of the circuit is best when the load impedance is a certain value. The optimal load impedance is usually several thousand ohms to several tens of ohms, and the impedance of the speaker is only a few. Ohm, the difference is too large, so the output transformer is used for impedance transformation. The output transformer of the tube machine is usually equipped with different taps. Regardless of the impedance of the speaker, the set of taps with the same value (or proximity) on the output transformer can be “mapped†to the optimal load required by the amplifier. In summary, when the amplifier is equipped with a speaker, there is no need to worry about the impedance of the speaker. The transistor machine can be connected to any impedance speaker, and the tube machine can adapt to the various impedance speakers by selecting the tap of the output transformer. 9. Why do some speakers eat power, what is the cause? Two reasons: First, the sensitivity of the speakers may be low. For speakers with a sensitivity difference of only 3dB, to achieve the same volume (or sound pressure level), the input power is doubled, such as a 90dB/W/m box, to obtain 100dB sound pressure level at 1m. As long as you input 10W of power, it is enough, and for 87dB/W/m speakers, you need 20W of power. If the sensitivity difference of the speaker is 10dB, then the input power under the same output sound pressure condition will reach 10 times difference. For example, if the speaker with the previous 87dB/W/m is replaced with the speaker with 80dB/W/m sensitivity, or the sound pressure of 100dB is obtained at 1m, the input power required is as high as 100W, which is higher than the 90dB/W/m box. 10 times. Second, perhaps the sensitivity is not low, but the impedance characteristics are abnormal. For example, some speakers, the sensitivity is 87-90dB/W/m or more, it is not low, but look at their impedance curves, the impedance at some frequency points may be as low as 2Ω or even 1Ω, such low impedance for ordinary amplifiers Already close to the short circuit, how do you push it? Certainly, there will be a very serious overload distortion at these frequencies. To tame such a speaker, only the super-powerful amplifiers with Krell and Mark Levinson whose load impedance drops to 1 Ω can maintain linear growth. If you encounter a box with low sensitivity and strange impedance characteristics, the requirements for the amplifier are even more demanding. 10. Does anyone use a tube amp with a power of only a few watts to push a pair of large speakers, does this make sense? Some people think that the large-caliber horn used in the big speaker is very heavy, and the power amplifier is not pushed. In fact, it is a matter of course. The demand for the amplifier power is mainly related to the sensitivity of the speaker, and has nothing to do with the size of the unit. Many large speakers, especially those with large-diameter paper cone woofers, such as the American JBL, Klipsch and other companies, the sensitivity is quite high, usually above 90dB, and some even reach 95dB or more. For such speakers, A single-ended amplifier with a power output of a few watts can push them to the blast. Some enthusiasts may know that in Japan, the use of 8W single-ended 300B amplifier to push the sensitivity of JBL speakers is a very popular game. 11. The speaker is 100W. Can you push it with a 50W amplifier? If you push it with a 200W amplifier, will it burn the speaker? First of all, it should be clear that the 100W power indicated on the speaker manual or on the nameplate refers to the carrying power of the speaker, which means that as long as the power exceeds 100W for a long time, the speaker will not be damaged, instead of using a 100W amplifier. As for how many watts of power amplifiers are needed to drive, it is mainly concerned with the sensitivity of the speakers and the required output sound pressure level, which has nothing to do with the carrying power of the speakers. Generally speaking, the speakers with extremely low sensitivity are always a few, and the sound pressure level required in the ordinary home environment will not be very large. The 50W amplifier can already satisfy many speakers. Of course, the impedance characteristics of some speakers are quite special, which is a very serious test for the amplifier. At this time, a powerful power amplifier with high power and high current output is required to tame them. Look at the second question: Will you use a 200W amplifier to burn a horn? It depends on how you use this amplifier. Indeed, 200W has exceeded the maximum carrying power of the speaker. If the volume is turned to the maximum and the amplifier is always at full power output, then the pair will burn. But this kind of situation will hardly happen. No one will suddenly screw the volume of the amplifier to the end. In fact, when the volume is too close to the overload distortion (breaking), no one will continue to increase the volume. It is equal to increasing the power input to the speaker) to make the speaker completely rupture, but it will reduce the volume to make the speaker sound normal, so that the average power input to the speaker is always controlled within the safe range that it can withstand, even if The power of the amplifier is so large that it only outputs the part that the speaker can withstand. How can it burn the horn? On the contrary, the power reserve is increased by the high-power amplifier, which can avoid the overload distortion of the instantaneous large dynamic peak music signal. It is also good for ensuring the quality of playback. 12. What is the meaning of "20-200W" on the nameplate of the speaker? What is its power? This is not an indicator of the power carried by the speaker, but rather the recommended amplifier power range, which is recommended by the manufacturer to use an amplifier with a power range of 20-200W. 13. When the speaker is in use, is the net removed or worn? The mesh looks like a thin layer of yarn, which actually affects the sound radiation. If you use the instrument to measure the frequency response when there is a face mesh and a no-face mesh, you will find that there is no small difference between the two. . Most of the speakers are tested and calibrated at the factory without a mesh, so the net should also be removed when in use. Of course, there are a few speakers that are said to be tested and tuned under the conditions of wearing the upper net, and should not be taken when listening. It is said that the American Avalon speaker is like this. 14. What are the special requirements for the speaker in the home theater system? Home theater systems generally use a surround sound playback system, so the number of channels is large. The popular Dolby Digital and DTS systems use five broadband speakers to form the front and rear channels, and a subwoofer. The requirements for these speakers are no different from those for high-fidelity two-channel systems. They are still common requirements such as wide frequency response, low distortion, low sound sensitivity, and good transient response. In principle, as long as you listen to music, you can listen to music. For home theater, there is no problem, but those with weak dynamic output capabilities (such as LS3/5A) are not suitable, otherwise it will be overloaded and distorted when encountering a dynamic scene. Since the center speaker is generally used on a TV set, it should have anti-magnetic properties. In addition, the sound of the speakers of each channel should be consistent, it is best to use the same series of products from the same manufacturer. 15. Where can I find the most professional home theater related technical information? Home theater network http://, the official micro signal: cnhifi.
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