Home theater audio debugging full analysis of the two-line crossover

table of Contents:

The first chapter of the home theater audio debugging full analysis of the speaker wiring debugging

The second chapter of the home theater audio debugging full analysis of the subwoofer settings

Chapter III Use of Sound Analyzer for Full Analysis of Home Theater Audio Commissioning

The fourth chapter of the home theater audio debugging full analysis of the power amplifier configuration

The fifth chapter of the home theater audio debugging full analysis of the impact of the power supply

The sixth chapter of the home theater audio debugging full analysis of the two-line crossover

The seventh chapter of the home theater audio debugging full analysis of the top ten lies in the audio industry

The sixth chapter of the home theater audio debugging full analysis of the two-line crossover

I have always used a single-line approach to listening, fever is always not satisfied with the current situation, a little improvement is the most exciting thing! We inevitably think of the two-line voice-playing game. First make sure that your speaker has 4 binding posts, remove the shorting tabs or wires of the two or two binding posts, use a multimeter to measure whether the two negative poles have resistance, and infinity to judge the internal high and low woofer, double-line crossover It makes sense. If the two negative poles are connected, you don't have to be discouraged. On the two systems, watch a movie and listen to music. AV movie amplifier is connected, you can also pick up the pure CD amplifier, haha!

First, what is the 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.

Second, double line crossover

At present, advanced speakers use a two-line crossover design. If you want to use this function, you need to prepare a pair of speaker cables and remove the shorting between the two pairs of terminals. Otherwise, you will not be able to get two wires. The role of the sound. If the amplifier has only one pair of outputs, it is necessary to connect two pairs of speaker lines in each channel in parallel, that is, two "+" lines are connected to the "+" output of the power amplifier, and two "-" lines are connected to the "-" output of the power amplifier. end. If the amplifier has two pairs of outputs, it is much more convenient to use two-line split. Just connect each pair of terminals to a pair of wires, but remember to twist the speaker selector switch on the amplifier to A+B.

However, the speaker cable is best to buy a 4-core cable that supports two-line crossover. Generally speaking, the color is exquisite, and the light-colored tweeter is connected to the bass. This kind of wire is designed for the sound distribution, the effect is much better than the simple use of the same wire or casually with two sets of wire.

The length of the speaker cable required in the home is usually two to three meters. There is no obvious difference between being longer or shorter in this range. However, be careful not to wrap the extra speaker wire into a circle when wiring, which will increase the inductance and damage the replay quality. If you buy a longer speaker cable and don't want to cut it short, the correct way is to bend the wire to avoid winding. Another point to note is that the lengths of the speaker cables on both sides must be as identical as possible. If the difference is too much, the left and right tones will be unbalanced.

Also be sure to use the two ends of the same pole line to connect the \\"+\\" output of the amplifier and the \\"+\\" input of the speaker, and the other pole to connect the \\"-\\ of the amplifier. "Output and speaker \\"-\\" input. If you make a mistake in the phase, the two-line crossover may be to burn the equipment! The connection direction of the speaker cable is also very important. In general, each wire has an arrow or text on the body. When using, just follow the direction of the arrow or the text, use the amplifier as the starting point to end the speaker, and connect the two with the speaker cable.

The effect? ​​You listen to it yourself. I think there is a clear improvement in the system. If the speaker supports bi-wiring, then the effect of buying the four-core wire that has been used is definitely much better than that of a pair of two-core wire. In addition, the best public housing also has two sets of output such as Accuphase E 530 or Maijin 6850 and so on.

If you are not satisfied, you can try the "double amplifier" connection method, which is to use the four-way amplifier to push the tweeter and woofer of the two-channel speaker separately. There is a friend who uses Mark's front and rear (4th level) to split the line. I feel that the effect is limited.

Third, double line crossover

In the case of a bi-wiring connection, two (two pairs) of speaker cables are used between the power amplifier and the speaker. Usually, after connecting by two-line crossover, it will always be better than the normal sound connection.

Most High-End speakers have two pairs of terminals dedicated to two-wire crossover connections. One pair of posts is used to connect to the high frequency circuit of the crossover network; the other pair is used to connect to the low frequency circuit of the crossover network. When making a two-line crossover connection, you should also remove the short-circuited wire that was originally spanned on the two pairs of terminals on the rear panel of the speaker.

In a sound system connected by a two-line sound split, at a low frequency, the speaker line connected to the tweeter seen by the power amplifier exhibits a high impedance, and at a high frequency, what is seen is Low impedance; for two-wire splits connected to the woofer and speaker cable, the opposite is true, that is, low impedance at low frequencies and high impedance at high frequencies.

Therefore, the signal has been split into two parts. Most of the high frequency leads to the circuit connected to the tweeter, while the lower frequency part leads to the circuit connected to the woofer.

Since the frequency is divided, the mutual magnetic field interference in the speaker line is reduced, and the sound quality of the playback is improved. The strong magnetic field generated by the low-frequency energy in the wire will not affect the transmission of high-frequency energy. Although no one knows how the two-line crossover works, it is true that almost all the sounds connected by the two-line sound split can make the sound quality of the playback quite improve. Therefore, as long as the terminal is equipped with a terminal that can be connected in a two-line split mode, it should be connected as much as possible by means of a two-line crossover. Even if it is temporarily restricted by conditions and only two sets of ordinary speaker cables that are relatively inexpensive, they are still connected in a double-line sound.

The two-line split can be connected using two identical sets of speaker cables, or a specially prepared two-wire split speaker cable. The speaker cable for the two-wire crossover connection has a pair of inputs (positive and negative) at the end connected to the power amplifier and two pairs of outputs at the other end connected to the speaker. Therefore, not only is the connection convenient, but the sound quality of the playback is also better.

There is also a single speaker cable for two-wire crossover connection, that is, a multi-core cable is installed in the cable of the root. There is a pair of solder tabs at one end and two pairs of solder tabs at the other end. Although this method can make the production cost lower, it is less in terms of high frequency and low frequency magnetic isolation. The speaker cables for the two dedicated two-wire crossovers are shown in the figure. In most speaker cables for two-wire crossover connections, the same speaker cable is used for both the high and low frequencies. However, if you use a hybrid approach, you can also get some benefits. If the low-priced part uses a low-frequency performance speaker cable and the high-frequency part uses a sound-sounding speaker cable, you can get better sound quality with less cost.

If you use a cheaper speaker cable in the low frequency and spend more money on a higher frequency to choose a better speaker cable, the treble will be more pleasant when the length of the two pairs of speakers is the same. If different speaker cables are used in the two-wire crossover connection, the same speaker cable manufacturer's products should be used as much as possible, and the physical structure should be the same. Because in the speaker line of the two-line crossover connection, if the distributed capacitance and inductance are different, the characteristics of the crossover network of the speaker will change.

However, some people do not agree with bi-wiring. For example, the British Naim Audio company believes that as long as the crossover network in the speaker is well designed, there is no need to connect in a bi-wiring manner. Because it is simpler and safer to connect with a single set of audio and video lines, and still get a buzzing sound; the American Thiel speaker manufacturing company is opposed to both bi-wiring and bi-amping.

They think that instead of using a common speaker cable to connect or use two general power amplifiers to push, it is better to use a set of better speaker cables to connect or use a good performance amplifier to push. The reason is that when using two sets of speaker cables or two amplifiers, it will not be able to achieve a seamless connection in frequency. Moreover, in order to allow the speakers to be connected in a bi-wiring manner, special wiring and special wiring are required in the speakers. Add a set of terminals to the output and use a special shorting pad. The speakers made by Thiel and Naim Audio do not have bi-wiring and bi-amping connections. In addition, the American Avalon speaker manufacturing company also holds the views and practices of the class.

Fourth, the double amplifier thinking and actual combat!

The play of the bi-amplifier has been popular for many times many years ago. I also experienced the benefits of playing the Zhuo Li Hiper1MKII, but it was not promoted in the market for various reasons, and some famous brand speakers did not. Bi-amps are also limited by providing a two-wire split speaker post. While some friends are playing a double-line speaker, they also use the form of a jumper. Of course, there is no bi-amp drive. Because to play Bi-amp, you must have the premise that the speaker can play Bi-wire, so before entering the theme of Bi-amp, I would like to talk about Bi-wire two-line crossover.

Speaker double line crossover (Bi-Wire) is the premise

Closely connected to Bi-wire is the design of the speaker in the speaker. In a single-wire connection type splitter that only provides a set of speaker posts, we can see that the reference ground potential of the high and low-speaker unit is on the negative side of the interconnected short-circuit piece, passing the 2.5-meter to 3-meter-long speaker. Line, then to the negative end of the amplifier output terminal, here is usually the reference point for the amplifier to obtain a negative feedback signal. Since the distance is relatively long and the speaker line is unlikely to have zero impedance, the two reference points actually differ, that is, there is a relative potential difference. In addition, the treble and woofer use this as a reference point at the common ground point on the horn terminal, but the flow in this ground line contains the reflow of various filter currents, that is, the tweeter will be from the reference point. The components of the high-frequency signal filtered by the woofer are picked up, and the woofer picks up the low-frequency signal filtered by the tweeter, which has a negative impact on the sound. The Bi-wire design solves the problem of inconsistency of this reference point to a considerable extent. We establish the reference point on the negative end of the output of the power amplifier by separating the independent ground lines. In theory, this method should bring A considerable improvement in sound quality, and this is the starting point for the two-line crossover design.

However, in actual use, some friends feel that the improvement is not big, which is closely related to the design of the crossover. If the quality of the crossover is not good, the internal electromagnetic interference is very serious, of course, only by setting the double of the independent ground. The line method cannot be solved. As the heartbeat of the speaker and the control center of each unit, the crossover function is not only the frequency division, but also the perfect connection of two or more speakers is completed by it, so the design is exquisite and has high completion degree. The sound is also very rare, and it also contains the designer's school sound experience, and the Know How to learn. High-level crossovers are hard to come by, and often only on the flagship products of the speaker manufacturers, we can see the most complete crossovers, like the top boxes like Thiel, Jmlab, etc. Speaker terminal, but in the middle-level products, most of them now also have a two-wire crossover connection. I think it is actually limited to R&D, cost factors and compromise on the crossover, allowing users to pass Bi-wire and Bi-. The opportunity of amp further develops the potential of the speaker.

Three ways of playing double power amplifier

Under the premise that Bi-wire enhances the sound effect, the relationship between the unit and the power amplifier is simplified by using Bi-amp. In the world of bi-amp drive, the high and low sound units each have a separate power amplifier drive, which means the power supply of the power amplifier. The supply has more sufficient guarantees, the interference between the sound paths after the frequency division is less, and the composition of the negative feedback signal is relatively simple, which will have an important impact on the improvement of the sound effect. Bi-amp's gameplay can be divided into three types, except for models that can be bridged to mono. The first is to output two sets of signals to two rear stages with one preamp, one second treble of a pair of speakers, and the other two subwoofers of the second stage. This is also the most common. In the following text, I want to introduce you to your bi-amp configuration. This is the gameplay. The second gameplay is developed on the basis of the first one. We know that in the first gameplay, the signals of the two rear-end outputs are still full-range signals, and then split by the crossover. Consumption, amplifying the full-frequency signal is still a burden for the power amplifier. Under the premise of retaining the speaker's crossover, some people have come up with a high-pass filtering device that is designed in advance to match the high-pitched power amplifier, and the low-powered booster amplifier. Through the filtering device, the signal sent from the previous stage is divided firstly, and then sent to the subsequent stage for amplification, and finally the speaker is pushed, and the sound separator in the speaker still plays the frequency division function, then for the latter stage, the amplification is divided. After the frequency signal, the frequency range is much narrower, the burden of the power amplifier is further reduced, and the efficiency is improved. However, this game method has higher requirements for the player's hands-on ability and listening experience, which is considered to be between the electronic sound and the Bi-amp. a form of compromise between the two. The last one is purely active electronic crossover, which requires the user to open the box to remove the original crossover, and requires a high level of electronic crossovers, and the characteristics of the speaker unit used in the speaker are quite Familiar, in theory, this Bi-amp method is the most thorough and efficient, and the sound effect is more obvious, but it is actually the most difficult to use, unless you use pre-consideration of electronic soundtracking like Linn. The speaker of the interface, if there is no dedicated audio test instrument in hand, the difficulty of trying the general box is quite large, and it is not easy to promote.

Three problems that should be paid attention to in traditional bi-amp play mode

Therefore, from the three Bi-amp gameplays described above, the most practical and easiest to use is the first traditional dual-amplifier configuration. Of course, although this gameplay is the simplest, there is a certain amount of equipment used. Claim. First of all, the pre-stage used must have two sets of outputs, or use a merger with pre-stage output and a pure post-stage. As Arcam et al. presupposes this way, the merger pushes the treble, after Push the bass, but this method is only suitable for the merger and the rear of the same brand, because the use of two amplifiers to push the high and low sound will involve the problem of balance and phase shift. The manufacturer's configuration has already been the preamp. The output impedance of the two groups is consistent with the input impedance and gain of the two subsequent stages. Generally, the imbalance of the range is not generated, but if you want to change another pure final stage, the input impedance of this latter stage is assumed. Too high or too low, if the difference is too large with another power amplifier, the range may be unbalanced and needs to be adjusted by another means. Therefore, using a combined machine as a pre-stage to play Bi-amp, without using the rear stage of the same brand, you must use the rear stage with the volume control function to match, so that you can achieve a balanced listening sense. Generally, the input impedance of the transistor machine is 47KΩ, and the input impedance of the amplifier is 100KΩ or higher. As long as it is not too low (less than 10KΩ or 5KΩ), the volume adjustment can be used to achieve the balance of the range with the merger.

The similarity is to adjust the relative sense of the high and low sounds, so that the sound range has a balanced and harmonious sense of hearing. Actually, it is not too troublesome to do, because the output voltage of the front stage of the combined machine is also controlled by the volume knob. When the volume of the combined machine is increased or decreased, the volume of the external amplifier will also change accordingly, that is, when you After using the test record to find the balance point of another amplifier, you don't have to move it anymore. Just listen to the volume of the two amplifiers while listening to the volume of the amplifier. The range of the range is balanced. In the future, only the volume of the combined machine will be rotated. The * is also very simple.

The last thing to note is the output phase of the two amplifiers. This actually refers to the gain amplification stage inside the amplifier. If one gain stage is an even multiple and the other is an odd multiple, then the usual speaker wiring method is used. There will be a situation where the treble and the bass signal are inverted. If there are conditions, it is best to use an oscilloscope to observe, or use some discs with normal phase or reverse phase test signals to judge. If there is a reverse phase, the speaker will be wired. The negative side is reversed.

My actual experience

Some time ago, I conducted a variety of bi-amplifier experiments for my current music tour ECI-2 push Castle Inversion 15 speaker combination. The music tour ECI-2 is 2X50W when 8Ω is loaded, and the power output is 150W when 2Ω. The maximum current can reach 45A, a typical high current design. The level of the front part is not bad, so consider using it to push the 6-inch carbon fiber woofer on the castle Inversion 15, and find another amplifier to push the treble. So the actual combination of a variety of power amplifiers, the transistor machine has the original QED A270, as well as Onkyo's 9911, the amplifier has single-ended design 300B and 2A3, and 6V6 and other models, from the results of the actual audition, Transistor treble is not in line with my taste, although it is better than the ECI-2 push for music alone, but the transistor machine looks a bit harder and harder than the soft and delicate high-frequency features of the amp. There is a certain gap with the amplifier. Among the several amplifiers, the best performance is 300B, the sound of 6V6 is not loose enough, and the power of 2A3 is too small. The output of 3W is perfect for the horn of 95dB or more and the full-range speaker, but Pushing the ordinary crossover box is still difficult, even if it only pushes the top of the ball, it is powerful, and the 300W of the 7W output is much more comfortable. It promotes the high-pitched sound of Inversion 15 easily, and it is a kind of elegant and moist, delicate feeling. The rich taste and complementary experience with the music tour ECI-2 have become the main force of my current Bi-amp match.

Compared with the music tour ECI-2 to promote Inversion 15 alone, Bi-amp's promotion can be described as comprehensive. There are many friends who come to listen after playing the double-amplifier. After the comparison on the spot, everyone's impression is still very consistent. I think that the improvement in the performance of my system is very positive. Overall, the improvement brought by Bi-amp is mainly reflected in these aspects. Firstly, the control power of the low frequency is obviously enhanced, and the low frequency is solid and clean. At this time, the image of the instrument such as the drum is clear and the details are richer. What is obtained is a low-frequency performance that is flexible, strong and has both analytical and quantitative feelings. 300B pushes the high frequency, the kind of moisture that is reflected, the warm and mellow sound is also unmatched by the crystal machine, especially the replay of the high frequency overtone, each note is like a dragging a small tail, making music The expression is more and more attractive. In the middle frequency band, the details reflected at this time are more rounded and the appeal is greatly enhanced.

Many people have expressed doubts about whether Bi-amp can use different power amplifiers to integrate sound and speed. From my experiment, it is basically which power amplifier pushes the high sound, and the whole amplifier reflects which power amplifier. The tone, so the tone should be more determined by the treble amplifier, indicating that the lower the frequency, the smaller the effect on the tone, but the mid-low range plays an important role in the rich and heavy sound of the sound. It also provides us with the choice of different amplifiers, and it is convenient to call up your favorite system sounds. As for the compatibility of the styles of the two amplifiers, the players really have to use the heart to match. The key is to choose the amplifier that pushes the high and low sounds. Generally speaking, the transistor with strong innate control of the low frequency pushes the bass, the amplifier or the tone is delicate and feminine. If the crystal model pushes the treble, it is easy to get a harmonious balance of hearing. In some mismatched combinations, people will notice the imbalance of the range, but as long as they match the method, they use different brands of amplifiers and even amplifiers and crystals. The hybrid double-amp play game, I believe it will not bring obvious negative effects.

Five, the basic idea of ​​the double-line crossover speaker bridge selection---subtraction equalization

(1) Tighten the low-frequency main line to the high-pitched sound, and select a medium-diameter copper wire for the bridge connection. The general wire diameter is between 19-21, the count is between 2-6, and the length is selected between 8-12cm.

(2) The main line of high-frequency analysis force is connected to the bass, and the bridge wiring is selected from small and medium-diameter pure copper or pure silver wire. The general wire diameter is between 21-23, the number is between 1-4 and the length is 10-15cm. Selected between trials.

(3) The high-frequency over-bright main line is connected to the bass, and the bridge wiring is selected from a single-diameter pure copper wire. The general wire diameter is between 17-19, the number is between 1-4, and the length is between 10-20 cm. Ding. If multiple strands of thin-diameter stranded copper wire are used, it is more compliant.

(4) Increase the low-frequency thickness, slow down the main line to connect the high-pitched sound, and select the single-diameter pure copper wire with the diameter of the bridge. The general diameter is between 17-21, the number is between 4-16, and the length is 15-50cm. The test is selected between the two. If the thicker and more stranded thin-diameter stranded copper wire is thicker than the (3), the speed is slower.

(5) Improve the medium and high fine lubrication or beautify the medium and high main line to connect the bass. The bridge wiring selects the medium or small diameter pure copper or pure silver wire or pure copper mixed sterling silver. The general wire diameter is between 19-23, the number is 1 Between -4, the length is selected between 10-20cm.

(6) Other factors to consider are whether the terminal is close to the bass or high pitch. The much shorter available bridge length can be longer, which can complement the length and adjust the tone. Otherwise, it may cause the phase problem to increase. .

(7) Note: The characteristics of the sound of various brands of wire, the number of stocks, thickness, length, material, purity, structure, and the effect of mutual matching can produce countless changes. For example, to improve the medium and high fine lubrication or to beautify the high wire Try to use high-end brand-name 6N or more pure copper or 5N or more pure silver wire effect is obvious. Others also try to select high-grade, preferably not lower than the main line. Because the wire is very short, the production process, the type of plug, solder The advantages and disadvantages, etc. are also very sensitive to the sound quality. In addition, the bridge wiring products are not many, and most of the domestic JS workers do more than: XLO ultra6, kimber 8TC, etc., the process grade is very general.

(8) Remember: Do not put the cart before the horse! The first improvement is your main line, then the bridge wiring, otherwise the subtraction equilibrium condition is not established, the effect is not ideal.

Six, double expansion machine conditioning skills

Whether "Double Expanding Machine Therapy" can really bring your sound system back to life, I believe many readers have been eager to try after reading this report by Liu, perhaps you can't help Liu's temptation to edit the three-inch tongue. After the "double enlargement therapy", and to appreciate another scene of the village of Liu Huaming, but some readers may still have many questions in their minds, or encounter various problems during execution, feel frustrated while sitting in the city, and even suspect Liu Whether the compilation is overstated. The author hereby endorses Liu's editor, "Double Expanding Machine Therapy" not only can make the poorly performing audio system come back to life, but also make the original sound system that has performed well to a higher level. How to achieve it depends on your conditioning wonderful. In this paper, the author will analyze the benefits of “Double Expanding Machine Therapy” from a technical point of view, how to use the amplifier, and what kind of auxiliary measures should be used when the two gains (magnifications) are different, the phase is different, or the input impedance is different. Explain that the readers can use it flexibly, making the double-expansion therapy a civilian treatment that everyone can enjoy, rather than the exclusive products of a few royal aristocrats.

The basic connection method of "Double Expanding Machine Therapy": a high-level and medium-range single-frequency crossover network that drives the horns by a pre-amplifier with two sets of output signals, coupled with the two-stage rear-end amplifiers. And the woofer crossover network (the picture shows the high-end crossover network driven by the vacuum tube, and the transistor amplifier drives the woofer crossover network).

Double enlargement therapy is an advanced means of tuning

Replacing the power cord, signal cable or padding of various shapes/materials to improve the sound effect is an indispensable tuning method for modern audio fans. If you have considerable experience and achievements in this respect, I suggest you to One step should be to try Bi-amping's tuning advanced method. As long as you read the report before the editor-in-chief of Liu, and then refer to the instructions in this article, you will find that the double-expansion therapy is actually replacing the power cord. The signal line is as simple as that. After you have learned the dual-enlargement conditioning skills and get a better sound with Bi-amping, you will realize that the original Bi-amping has far more benefits than replacing a whole set of wires. A set of wire money, but the improvement of sound quality is comprehensive), because the wire is a passive original, and Bi-Amping's expansion machine is the active original, replacing the wire is like replacing the car's tire and suspension suspension system The replacement of the amplifier is like the turbocharger of the car and the cylinder of the modified engine. The replacement of the tire and the suspension suspension system makes you feel more comfortable; the cylinder with the supercharger and the modified engine is added. (including the combustion system) makes you feel that the power of the car is more powerful (Powerfull) and acceleration, and the engine is running more smoothly due to the improved combustion efficiency, so it is more comfortable. The two feelings are completely different. Replacing the wire is throttling (reducing the loss of signal transmission), Bi-amping is open source (the two divisions expand the division of labor to directly deliver energy to each speaker unit), it is not enough to only consider the throttling, but also actively open source, The smartest way to do this is to find a suitable expansion machine instead of the most expensive one, to drive different speaker units in a division of labor, because finding a decathlon (excellent from low frequency to high frequency) must be It's quite expensive, and it doesn't solve all the problems.

Bi-amping can reduce the distortion of the amplifier

The speaker contains a voice coil and a crossover, and the components of the resistor, capacitor and inductor are assembled in the sound separator. Therefore, the load characteristics of the speaker are extremely complicated, and different impedance characteristics are exhibited at different frequencies, especially in the lower frequency band. Due to the relatively large amplitude of the paper cone, the voice coil causes a large back electromotive force after cutting the magnetic field. Generally, when the latter stage amplifier encounters extremely low impedance, capacitive effect and strong back electromotive force, the lighter causes the distortion of the machine waveform and the distortion such as ringing, and the unstable operation of the amplifier circuit causes high frequency oscillation. More serious people directly lead to the expansion of the machine; this is why many difficult high-end speakers with inappropriate rear-end amplifiers will make people feel that the high-frequency noise is sharp and harsh, and the sound is too dry and not full and full. There are a lot of advanced speakers to make the frequency response straight and accurate, the splitter circuit is designed into a very complicated structure, and even multi-cell drive, which is bound to impose a heavy burden on the amplifier, must be matched with the choice of high current, low output impedance And the low-level feedback of the post-stage expansion machine is sufficient, the price of such an amplifier must be expensive, and the implementation of Bi-amping will yield great economic benefits.

Why is it possible to achieve this effect by using two post-stages? Because the complex horn load is divided into two and is shared by the two post-stages, the difficulty of each drive is naturally reduced, especially the most difficult to drive woofer. It has been driven by another post-stage. Since the high/mid-range and low-frequency crossover networks are completely separated, even if the amplifier produces distortions such as waveform distortion and vibration, it will not interfere with high/middle sounds. Unpleasant (the most sensitive frequency band of the human ear is in the high/mid frequency band). The post-amplifier is subject to distortion caused by the horn load. The high-frequency component is mostly present. The woofer has a low-pass crossover network before, so that most of the distorted signal is blocked outside the crossover network and not in the bass. On the unit, the distortion signal received by the woofer will be negligible. Therefore, the use of the two-stage division of labor can maintain a pure and illegible high/intermediate frequency, and a full and stable low frequency band can be obtained. Compared with the woofer, the high/midrange unit is usually better driven. If Bi-amping is implemented, the push/higher amplifier can have more choices, and many small wattages have a good texture. It is the best choice, such as the recently popular 300B tube machine after-stage amplifier. Open the audio magazine advertisement, any post-level expansion machine with better quality performance, the price is more than 400,000 yuan, and there is an increasingly expensive trend. I believe that it is not affordable for the general public or young audio fans. Can afford, so learning DlY is a way to save money and fun. For most audio fans who don't understand electronics, it may be a bit difficult to enter the DlY ranks. If you tell you that there are two rear-end amplifiers on hand and the speakers have Bi-wiring terminals (the high/mid-range and low speakers) The band crossover network is completely separate and separate. With the simple adjustment techniques described in this article, you can enjoy the enjoyment of Bi-amping. I believe you will definitely try it.

Bi-amping of the same model with the same brand

If there are two rear-ends of the same model and the same model, and the pre-amplifier has two sets of output, just use the two sets of signal lines to send the signals of the previous stage to the second stage; if the front stage only A set of outputs, you can buy a set of two RCA adapters from the electronic material line, but be careful at this time, because the inside of the two adapters are directly connected in parallel, there are very few rear stages or different brands. After the second stage, if the input is directly connected in parallel, it may cause oscillation. How to judge whether there is oscillation? If there is oscillation, it should normally hear abnormal noise from the speaker. In severe cases, the fuse of the rear stage amplifier will be burned. . In case of such a situation, there is still a solution. You can put a 10-100 on the input of one of the rear stages (remove the rear cover, after inputting the RCA terminal and between the signal lines). E-resistance can be used as damping to avoid similar situations (Figure 1-1). If you do not want to modify the post-stage, you can also add a string resistor to one of the signal lines, that is, the RCA plug is on the welding signal line. Before stringing a 10 to 100 ohm resistor (Figure 1-2). Although some preamplifiers already have two sets of output terminals, they are directly connected in parallel. This may also cause oscillation. In addition to modifying the post or signal line according to the above method, it can also be used at the output of the preamplifier. Add a string resistor (must remove the front cover, add a series resistor between the output signal line and the RCA terminal, as shown in Figure 1-3), the same can be achieved to eliminate the shock.

Gain adjustment

If the gains are different in the second stage, there are the following three solutions: First, install a passive preamp, and then attenuate the input signal strength to make the output of the two subsequent stages before the gain amplifier with a relatively large gain. The levels are the same. The so-called passive preamplifier uses only a variable resistor (VR) device in the metal case to form an attenuating circuit, and the resistance value must be equal to or slightly lower than the input impedance of the latter stage (see Figure 2-1). 2. Add a variable resistor to the internal input of the rear stage amplifier (after the RCA socket) to attenuate the input signal strength. The purpose is the same as the former, except that the VR is in the rear stage chassis (Figure 2-2). Third, modify the feedback circuit inside the machine to make the gain of the second stage of the machine consistent. This method is a little more difficult for the general audio fans, but it should be a very simple method for the DlY family who knows the electronic circuit (such as Figure 3-3). As for the gain of one of the latter stages, or the gain of the other stage, it depends on the characteristics of the latter stages. When reducing the amount of feedback to increase the gain of the amplifier, the following conditions usually occur: the sound speed is slowed down, the low frequency tail is longer, the low frequency feeling is slightly increased, but the feeling of condensation is lowered, making the entire sound field wider, but High frequency extension and fineness will deteriorate

On the other hand, if the feedback amount is increased to reduce the gain of the amplifier, the direction of the sound is reversed, and you can adjust it according to the above rule of thumb to obtain the best result.

Impedance matching

Does the difference in input impedance of a post-stage affect Bi-amping? Theoretically, the input impedance of the two post-stages is the most perfect. However, it is necessary to select the favorite timbre and consider the input impedance is the same. There will be a lot less, so it is proposed to provide some assistance here. Generally, the input impedance of the crystal post-amplifier is about 10K ohms to 100K ohms, but the input impedance of a few rare organic species is designed to be 10K ohms or less or 100K ohms or more. Most models are designed to be 50K ohms. Left and right, as long as you avoid the maximal and minimum values, it should not have much impact.但是一般真空管後级扩大机的输入阻抗却高达100K欧以上，因此若要将真空管後级与晶体後级互相搭配Bi-amping，则要特别注意输入阻抗的匹配问题，否则可能无法调整出平衡的声音，甚至导致真空管後级变成哑吧(发不出声音来)。许多音响迷偏爱管机那种迷人的高/中频，若要Bi-amping，高/中频段当然非选用管机不可，而先天上晶体後级扩大机的低频驱动控制能力比一般真空管後级强得多，可以说它与管机最适配了!笔者一位同事於数年前曾经尝试此种搭配方式，但始终未尝成功而耿耿於怀，最近又再度兴起这种念头，希望笔者能提供协助以达成多年的心愿。那位同事原来所用的晶体後级为Linear Acoustic LA l20，经查阅设计电路图，其输入阻抗篇4.7K欧，增益为48倍(一般後级之增益为20～30倍)，因此之前他以低输入阻抗高增益的後级，欲与高输入阻抗低增益的真空管後级搭配Bi-amping，虽然当时已另装了一部被动式前级藉以衰减Linear Acoustic後级的增益，但还是无法如愿，据他表示，只听到低频而不闻高/中频。为了解决上述问题，笔者提出下列解决方案：一、修改晶体後级的输入阻抗与增益，使与管机後级一致。由於上述修改会改变扩大机整体的音色，我那位同事希望能保持Linear Acoustic之原味以备不时之需，例如，当管机故障时仍然可以单机驱动喇叭而不影响原有音色，故采取下一个办法处理(如图3-1)。二、另装一部主动式缓冲放大器(Buffer Amp.)藉以驱动并调整晶体後级的输出电平(如图3-2)。

首先由我设计电路及零件布置图，那位同事自行动手组装，完成之後再由我检查、测试，并协助最後的Bi-amping平衡调整，一切都进行得非常顺利成功。完成之後，使得中/低频更饱满，音场更开阔而深邃，高频更柔顺耐听，那位同事也感到非常满意，终于一偿宿愿，最近他正尝试著更换不同厂牌的真空管，享受不同管味的高/中频音色。Bi-amping虽然花费不多，但在玩音响的生涯中又迈进一大步，好像增添了调色盘，让音乐的色彩丰富了起来。缓冲放大器的增益一般设定为一，也可以依实际需要调整，使其增益小於一或大於一，主要在于提供输入及输出阻抗的匹配功能，若在其输入端加装可变电阻器，即兼具调整增益的功能，您若没有能力DlY自己装缓冲放大器，也可另找一部前级取代前述缓冲放大器的功用，不过在还没有充分把握之前，建议最好先向同好借用前级试用一下，待成功满意之後再购买，以免造成不必要的损失，寻找较便宜的二手货也是不错的选择。

相位测试兴调整

二部後级若相位不一致应如何处理?执行Bi-amping之第一个步骤就是先确认二部後级的相位是否一致，一般扩大机可分为正相放大及反相放大两种，大多数扩大机都是设计成正相放大，除非厂家说明书有特别申明，但为了慎重起见最好还是先确认相位，利用示波器与讯号产生器是既简单又精确的测试方法，有此设备者都应该知道如何测试，故不在此多做说明，若同好或朋友中有此设备者可以委托他们代为测试。另唱片行可以找到许多CD测试唱片，上面录有左右声道、正反相及各种频率等测试讯号，您可以依据唱片上的说明进行相位测试。如果二部後级扩大机中，已知其中一部是正相放大，则可利用下述方法加以判定，首先将左右声道喇叭面对面摆放(注：距离拉近一点效果会比较明显)，由二部後级扩大机分别驱动左、右声道喇叭，已知相位之後级驱动左喇叭，另一部则驱动右喇叭，二部後级的输入讯号必须同时从前级的左声道或右声道接过去，也就是说二部後级是输入完全一模一样的讯号，然後选一张最熟悉、低频量比较多的CD唱片播放，如果低音量感正常，表示另一部後级也是正相放大，为慎重起见可以把右喇叭的接线(靠喇叭端)正负反接，反接之後若低音量感变少了，证明刚刚的判断是正确的。相位测试时请记住喇叭正相发声的接线方式(注：反相扩大机的喇叭接线其中一端之极性要反接，通常靠扩大机端的接线固定不变，仅於喇叭端正负对调反接)，Bi- amping时就依该接线方式分别接高/中音与低音喇叭就行了。这是不需增加任何装置的最方便接法，您也可以在反相後级扩大机之前加一部反相Buffer Amp.或反相前级，使该反相後级扩大机改变为正相输出，此时所有喇叭线即可照正常方式接线。

平衡调整

选择大电流、驱动力强的後级推低音喇叭，高/中频比较柔顺、失真比较低的後级推高/中音喇叭，完成Bi-amping接线之後接下来即可进行平衡调整，需准备的工具包括：数位三用电表及CD测试唱片，另外有示波器与讯号产生器的读者更方便，而且可调出更精准的平衡性。前面已经提到过，因为二部後级增益不同所以需加以适当的调整，而调整过程，後级扩大机需有适当的负载，因为轻负载与重负载情况下扩大机的增益略有差异，此时最佳的负载就是所要驱动的喇叭。由于比较耗功率的者就在低音喇叭，而一般低音的分频点都设在500Hz以下，三音路较大型喇叭都设在400Hz以下，所以测试讯号建议选择300Hz左右或更低频率的正弦波。为安全起见，测试前最好将前级关到最小音量，选定测试讯源之後再慢慢提高音量，一面提高音量一面利用数位三用表(交流档)或示波器量测高/中频与低频喇叭端子的电压值。若以测试CD片为讯源，当前级音量旋扭转到正常聆听位置时，测得电压疽大约在1~3伏持之间(4欧姆喇叭)，8欧姆喇叭大约在3~6伏特之间，视环境与喇叭的效率而定。若以讯号产生器为讯源，则宜特别小心，刚开始勿将讯号产生器之输出调得太大，以免导致喇叭损伤。调整工作最好能再请一个人帮忙，当前级旋扭调至适当音量之後即固定不变，其中一人调後级的输出电平，另一人则在喇叭端测量电压值。为什麽要在喇叭端测量而不是在後级输出端测量?因为喇叭线具有电阻值，大电流通过时会产生压降而影响调整平衡的准确度，又测量时要交互量测比较高/中音与低音喇叭端子的电压值直到完全一致为止。後级选择兴功率分配

解决了扩大机的增益、阻抗与相位匹配问题，音响迷最关心的大概是扩大机的功率选择问题，即驱动高/中频与低频喇叭的後级扩大机，其功率如何比率分配?在此不妨先看看ATC l00A喇叭内部电子分音扩大机之功率分配，ATC 100A系采三音路电子分音，其音箱内部设50、100及200瓦等三组後级扩大机，分别推高、中及低音单体。ATC的中音单体是出了名的难推，甚至比一般低音单体都还难推，因此ATC设计制造时才用100瓦驱动，换成其他单体大概只要50瓦就可椎得很好，故一般Bi-amping假设低音单体用200瓦推，则高/中音单体只要60瓦(真空管机30瓦)就够了;如果遇上比较难推的中音单体或是采用双中音单体者，我想以100瓦(真空管机60瓦)来推应该已经很足够了，以笔者过去的经验，推高/中频的後级“质”比“量”更重要。笔者十几年前曾分别装过Ne1son Pass先生设计的A40(A类40瓦)後级扩大机及Marsha11 Leach先生设计的250瓦双快枪後级扩大机，前者高/中频音色柔美但推力却不足;後者低频驱动力比较好，但高/中频的延伸却不够柔美飘逸，因此分开单机使用都有缺陷。经进一步研究发现两者的输入阻抗与增益几乎相同(前者输入阻抗为40k，後者为43k;前者增益为24.3倍，後者为24.25倍)，于是将此二部後级Bi-amping推Duntech的Crown Prince喇叭，截长补短的结果相当今人满意，遂以此搭配聆赏音乐达好几年之久。A40与双快枪虽然是DIY经典之作，但离笔者理想还是有一段距离，经过数年的研究设计，加上无数次的实验，终于完成另一部220瓦之大电流後级扩大机，以单机驱动Duntech所得到整体音乐性与音响性的表现足以取代A40与双快枪Bi-amping的效果，虽然维持使用了好几年，但此其间还是念念不忘当时采用Bi-amping让丑小鸭变天鹅的美好经验，于是又试著另外设计一部120瓦大电流低失真後级扩大机，这次特别针对高/中频段的音质进行设计与实验，以便用来推Duntech的高/中频单体，因为高/中频段是人耳最敏感的部分，故深信只要依预设的高标准完成这部後级，要把“天鹅”再蜕变成“天使”的梦想一定可以实现。为了实现此种理念因而耗费了许多不眠不休的日子，又为了一一突破诸多技术瓶颈，而翻遍了各类技术手册，绞尽了脑汁，幸好皇天不负苦心人，终于赐给我天使的歌声，让我的美梦成真!

Bi-amping VS.Alloy&Hybrid

编写本文期间，一直苦思是否有日常生活上的例子可与Bi-amping之妙相提并论者，以便加深读者的印象，就在本文快完成之际，终于想到“合金”与“混血儿”的现象，特在文未引喻如下。

不同金属元素混合制成合金(Alloy)之後，其硬度与机械强度均会超越个别金属元素原有的特性，例如：“黄铜”是铜与锌的合金、“青铜”是铜与锡的合金，锌与锡都是非常软的金属材料，但制成合金之後，硬度与强度均超越纯铜许多;“K金”是金与铜的合金，市面上钻戒的台架一定是用K金而不采用纯金，因为纯金太软了，纯金虽如此高贵还是需要铜的辅助才能更坚强而且能散发出光芒来!各位家中的菜刀与水果刀也是由合金制成的才不致於用不到几下就钝了;工业界更少不了合金材料，如大家最熟悉的不锈钢是镍与铬的合金，而航空用铝合金、钛合金等均是选用一定比例的不同材料相辅相成制成的合金，才能有如此优异的表现。不同民族通婚所生的混血儿(Hybrid)都比父母更聪明漂亮，此从众所周知的许多演艺界漂亮宝贝与国际间闻人即可获得证实。同理Bi-amping也具有类似功效，即可以隐藏缺陷彰显优点，化腐朽为神奇，明白此理并起而行之，经过细心调理定可同时拥有最喜爱的高/中频与低频，鱼与熊(注：不同厂牌、机种与不同增益、相位的扩大机混合搭配)，管石共融(注：真管机与电晶体扩大机混合搭配)的太平盛世，定能缔造音响的桃花源!

如果您拥有一流的喇叭、一流的听音环境，但始终唱不出美妙的乐声;当您玩遍了所有发烧线材;还是找不到您所喜爱的声音，建议您在换喇叭前一定得试试双扩大机疗法，说不定能带给您全新不一样的惊喜。战场上请求地形地物利用随机应变，玩音响也要能就地取材灵活运用，但愿本文所提Bi-amping调理技巧能帮助您在音响的领域里有更宽广的挥洒空间，您将发现原来可以只花很少的钱，甚或不花一文钱也能让音响系统注入新的生命力，更重要的是，美好的成果有您贡献的一份心力(Effort)，此种喜悦是花再多钱也买不到的。

二、CD测试唱片内所录之粉红噪音讯号(Pink Noise)不适用于本文Bi-amplng扩大机输出电平之调整测试用，因为一般三用电表或数位三用电表之性能无法正确量测粉红噪音之电压价，粉红噪音讯号主要功用是作为频谱分析仪量测调整喇叭摆位与环境特性之用。

七、反思误区篇

Bi-Wired的迷思

许多消费者在购买扬声器时，除了价格、音质与外观之外，通常关切的问题还包括了是否配备有Bi-Wired(双线输入)或Tri-Wired(三线输入)端子。其实会使用双线接驳的消费者并不多，大多数的音响迷多半使用厂家随机附上的跳线(铜片或是粗铜线)，而店家在介绍扬声器时，也会特别强调它的Bi-Wired端子配备(所以卖你贵一点是应该的)。我想，可能有些店家都搞不清楚Bi-Wired的好处为何?但是一想到可以多卖一对喇叭线，当然就会特别强调Bi-Wired装置。

如果扬声器是以Tri-Wired设计，强调多线输入优点的音压肯定超过96dB(注1)。问题是，高级扬声器是否就一定要具备Bi-Wired或Tri -Wired端子?具有多线输入的扬声器，音质就一定比单线输入(Single-Wired)来得好吗?笔者也常被问到这个问题。现在，就让我们来探讨一下Bi-Wired设计方式的优缺点为何，以及我们使否能藉此发挥扬声器的特性与潜能。

多线接驳

Bi-Wired的定义是什么?它的中文解释为：双线接驳(也可称为『双线分音』或『双线输入』)。如果我们查看扬声器背板的接线处，会发现二组接线端子配置其上，同时标示着「Hi-Pass」、「Low Pass」，或是「Hi-Frequency」和「Low-Frequency」的字样。这种设计代表的意义，就是分音器高通及低通线路是完全分开的;如果是Tri-Wired设计，那么高音、中音和低音的分音器部分就各自独立。

就分音器来说，Bi-Wired和大多数的Single-Wired最大不同处，在于地线的连结设计。一般而言，Single-Wired的地线接驳是各音域共享的，但是这样的接法却很容易产生串音(试想，工程师千方百计用高级零件且精密的计算零件数值，就是要让单体在设定的音频内工作，如果产生串音，那不是很冤枉吗?)。某些扬声器的设计，是将高音单体的正极接到分音器的负极去，若是如此，那真的是提到肉粽头-一大串了：当二个单体除了分音器区隔的频率以外，再混入串音所造成的另外一只单体负责之频率，此时单体本身已有频率加倍或抵销等电能转换为声能后，又和另一只单体互相干扰进而造成音质的渲染。

音质的无形杀手

反过来看，多线输入的高音和低音分音器是完全分开的，各自拥有专属的地线，分层负责。从输入端以后就独立分频，其中并无任何零件相连，所以可以大幅降低串音干扰，音质也会相对的提升。但是这样的设计，王子和公主就可以各自独立快乐的生活吗?让我们更进一步的观察。一般的分音器(无论是Bi-Wired或Tri-Wired)，都建构于同一块电路板上，或多或少都还是会产生电气性串音。举个例子来说，当我们检视一只具有Bi-Wired的扬声器时(高通和低通电路共享一片电路板)，假若我们将高音单体与分音器间的接线、Bi-Wired的跳线或短路棒通通拿掉，再从背板上的高音端子输入讯号，这时因为高音已断路，理论上是不会发出声音的;但是我们却可以从低音单体听到相当轻微的声响，这就是所谓的「电气性串音」。那么，这种「电气性串音」要如何排除呢?其实很简单，只要我们把电路板切开成二半，再将二片电路板分隔10公分以上，如此一来就可以大幅降低「电器性串音」。但是，不管你用什么方法处理(切、锯、剪、割、雷射、水刀……)，当你动手修改或是「升级」以后(注2)，你就自动放弃原厂保固的权利。唯一可靠的办法，是先把原厂的分音器取出，画下原设计之线路图并标示零件数值，另外制作一个分音器，而原厂的分音器千万要保留起来，假使扬声器不慎故障，还可加以还原。

电磁性串音

好了，现在王子和公主终于可以各自独立生活了吗?还早呢!为什么?因为我们磁场大哥，不时还会施以干扰，因为当感应电流运行时，会生成磁场(同时电容器和电阻也会有磁场发生，但可以用零件材料来解决)(注3)，进而影响旁边的电感，我们称之为「电磁性串音」。要解决这个问题也不难，只要把零件相距15公分以上，就可以将电磁性串音大幅降低。虽说有些扬声器的内部空间不大，实行上会遇到困难，可是也有解决的办法，只要记得把零件相互以90度错开就行了。

另外，分音器的位置对电磁性串音也有相当程度的影响，最好尽量将其远离喇叭单体，因为单体的磁场也会影响分音器正常工作。如果您是使用书架型扬声器，尽量不要将分音器安置于底板上，因为市面上的脚架都是使用铁为材质，虽然分音器位置远离了喇叭单体，但是铁脚架却会被喇叭单体感磁。这时候，如果分音器放置在底部，就会因为脚架的感磁现象而对分音器产生不同程度的干扰。当然，若是使用木制脚架，或将喇叭直接摆放在书架上，就可避免这个问题。

High End?

Bi-Wired对声音表现真的能有所提升吗?就理论上来说，Bi-Wired的确能有效的降低串音的生成，相互干扰的程度上也能有效地抑制，所以声音是会比较好听的(注4)。但是，若要达到High End级的水准，单单具备Bi-Wired或Tri-Wired是不够的，以上的串音及干扰因素，都必须排除才能称为名副其实的High End。很可惜的是，一般扬声器都不会花费太多成本在分音器上，因为分音器放在音箱内，消费者无法一眼就看见，绝大多数的厂商宁愿多花一些成本在音箱的制作。

至此，我的结论是：喇叭内在的分音器设计，远比外在来得重要的多。

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