The closed box was the technology invented by AR Company at the earliest. It used to be a baffle design. It was only after AR invented the so-called "air cushion" patent (that is, closed box) that it truly became a speaker. The characteristics of closed box are The low frequency has good strength, quick response and clear and powerful low frequency, but the dive depth is limited and the sense of low frequency is insufficient.
The transmission line box is based on the principle of an acoustic tube. After the backward sound wave emitted by the unit passes through a section of the sound tube, it is in phase with the forward sound wave at a certain low frequency, thereby obtaining a better low-frequency diving depth. However, the length of the acoustic tube needs to be half of the wavelength of a few tens of hertz, which is about a few meters long, so that although the phase between the backward sound wave and the front phase sound wave is in phase, there is a time delay of tens of milliseconds, so most transmission line boxes Although the sense of low frequency volume is good, the transient state is poor, and the low frequency is more turbid and weak. Looking at the current Hi-FI market in the world, transmission line design is rarely seen. My personal opinion is that the transmission line box may gradually die out. The starting point of the inverter box and the transmission line is the same. It is to make full use of backward sound waves to strengthen the low The frequency dives, but the inversion method uses the inversion method of the concentrated parameter resonance to replace the distributed parameter inversion method of the transmission line half-wavelength acoustic tube, so that although the sound wave is also inverted, the additional time delay It is only about ten milliseconds, and the inverted structure is simple, easy to process and easy to adjust. Therefore, the inverted and closed boxes have become the two major systems currently designed. Other common ones are the empty paper cone type (passive radiation type). ), The principle of which is the same as the inverted phase, and beyond the scope of this article, so it will not be introduced.
Inverted box and closed box are different. Fortunately, the closed box is strong, transient, and clear. Listening to classical music, especially chamber music, is excellent. Therefore, like the British ATC, it is special to close the box. The inverter box is good at low frequency, deep dive, sufficient sense of volume, high power consumption, high sensitivity, and more comprehensive ability to meet various occasions. The good and bad skills can only be decided by everyone.
In order to ensure the low-frequency dive depth and adaptability of the monitor No. 1 speaker design, the inverted phase design is adopted (and in fact can be completely closed), in order to ensure that no power compression or airflow sound occurs under the low-frequency loud sound pressure, The diameter of the inverter tube is not easy to be too small. In the actual design, the calculation formula is only a reference, and it is finally adjusted with the ear sounds.
After designing the size of the cabinet, we must consider the requirements for the production of the cabinet: the first is the selection of sound-absorbing materials in the cabinet. The different sound-absorbing materials can significantly change the effective volume of the cabinet. Some enthusiasts are misled by some domestic fever articles. Superstition uses glass wool or asbestos as sound absorbing material. Although the sound absorption effect of glass wool is higher and has the advantage of adiabatic expansion, in fact, unless the unit is not suitable, the design The volume of the cabinet is too large. Like some low-quality high-Q and high-equivalent volume speakers in China, glass wool is needed to reduce the actual volume of the cabinet. The use of glass wool does not have much advantages, and the use of glass wool in the speaker . Using ordinary sponge, acrylic cotton or long wool cotton, you can easily design a speaker with good sound quality. Because the design volume of the No. 1 monitor is about 18 liters, the mid-foam through-hole sponge was used in the design.
The selection and processing of cabinet plates have a huge impact on the sound quality of the cabinet. The requirements for the sheet are considerable stiffness and internal damping attenuation characteristics. At present, the preferred material is medium density fiberboard (MDF), but the quality of domestic medium density board is poor, and high density board can be used to achieve the effect of imported MDF. However, the internal damping effect of the medium-density board is still insufficient, and we use the method of attaching a specially prepared asphalt board to the inner wall to make up for it. The damping characteristics of this asphalt board are stable all year round, and the damping degree is excellent. First apply a layer of carpentry glue to the opened box board, place the asphalt board in the middle, and nail the big head nails 4-8cm apart, so that the box board and the asphalt board become an organic whole, you can basically do To the ideal of "only the horn sounds, there is no box sound".
After talking about the design of the cabinet, it is necessary to talk about the design of the frequency divider at the heart of the speaker. There is no doubt that the frequency divider is the soul of a pair of speakers. It directly determines the sound of the speaker. There is some mechanical understanding of the frequency converter. If someone once wrote an article "rebuking" the first-order frequency division (-6dB / oct), that the ideal filter with infinite attenuation is the best choice, that is, the more the filter order The higher the better, the greater the slope of the attenuation, the better. This view is only a superficial view of the effect of the "divider" of the frequency divider, and the second is the mechanical problem of the frequency divider consisting of high and low pass filters.
Regarding the frequency divider, I would like to talk about a little philosophy. In China, I once unilaterally promoted "one divided into two" and ignored "integrated into one". In fact, the author feels that "one divided into two" is a table. "Two for one" is the foundation. The sound of the tweeter is bright, which can be described as "yang", and the sound of the bass unit is low and deep, which can be described as "yin". The yin and yang have opposite sides and mutually inclusive sides, so it is the shape of the ancient Taiji black and white fish. It is not as simple as a round split in two, but the tail of the yang is the head of the yin. And the eyes of black and white fish are the yin in the yin. The so-called yin to yang of the yin in the yang. Returning to the crossover, its function is not so much to divide the yin and yang. Melting Yin and Yang in one furnace. Imagine if the sound of the woofer is below the crossover point and the sound of the tweeter is above the crossover point, will the timbre be split and the positioning of the audio image will jump up and down, it is impossible to achieve a better sound quality. On the contrary, if the quality of the unit is good, the bass unit is mainly below the crossover point, and the tweeter unit is auxiliary, and the opposite is the case above the crossover point. At the crossover point, due to the wonderful scheduling of the crossover, The two "yin" and "yang", which are different in timbre and so on, are organically integrated into one, and a better timbre can be obtained.
It can be seen from the above analysis that, under the premise that the performance of the unit is guaranteed, the lower order frequency divider is definitely superior to the higher order frequency divider, especially considering the large phase change brought by the high order filtering With a large time delay, the advantages of low-order filtering are self-evident. Of course, low-order filtering requires quite high requirements on the unit. If the crossover frequency is low and the filtering order is low, the power burden of the tweeter is greater. This is also the second order used in the tweeter filtering in the No. 1 design. One of the reasons for the first-order bass.
Deciding the order of high and low frequency filtering should also consider the problem of the phase connection of the unit itself at the crossover point. It is self-evident that the advantages of low-order filtering are to make up for the large phase change and large time delay brought by the unit filtering through the phase difference of high and low-pass filtering. Of course, low-order filtering requires quite high requirements on the unit. If the crossover frequency is low and the wave order is low, the power burden of the high unit is greater. This is also the second order used in the treble filtering in the design of monitoring. One of the reasons for the first-order bass.
Deciding the order of high and low frequency filtering should also consider the problem of the phase connection of the unit itself at the crossover point. The phase difference between the units is compensated by the phase difference of the high and low pass filters to obtain a flat phase frequency response, and the flat phase frequency response is a necessary condition for the pure and natural sound of the intermediate frequency tone. I recommend N601 and T301 here When matching, when the crossover point is within 2.5-3KHz, the high-pass filter is better than the low-pass filter by one order.
The second is impedance compensation. Since the role of bass inductance at the crossover point cannot be ignored, it is better to add an appropriate impedance compensation circuit, but the compensation must not be overdone, otherwise it will cause greater degradation of the sound color, and the compensated impedance will not The minimum impedance value that is lower than the impedance curve before compensation is good. For the adjustment of treble sensitivity, the L-type resistor attenuation network is the best. A single resistor attenuation does not save much cost, and it is not good for the tone.
Finally, I must mention that the two-line crossover is better. As for some friends, the problem of excessive treble after changing the single-line crossover box to the two-line crossover is due to the original design of single-line crossover. Due to the masking effect of bass crosstalk on the treble, the sensitivity of the treble is adjusted a little higher. After changing the two-line crossover, the treble attenuation should be increased a little. There is no such problem for the two-tone design itself. Refer to one of my articles in "Sound World".
After the sample box is designed, a series of test adjustments are required, including impedance test, amplitude frequency test, phase frequency test, distortion frequency response curve, water drop graph or transient response, etc. The professional design must be adjusted after the test has no problems, because the sound of the human ear is not adjusted, because without the foundation of science, there is no art, "there is no skin, Mao Zhiyan." For amateur production, if there is no test conditions, this can only be missed, you must seriously study the test curve provided by the factory, and thoroughly understand the original design, and spend more time on the human ear to correct the test, to make up for the test Insufficient conditions.
I have talked a lot in the previous section, but it is only the technical part of the speaker design. For advanced Hi-Fi, this may only account for 40%, while the art parts such as human ear calibration sound account for 60% of a good design. Although the technical parts discussed above are complicated, after all, there are traces to follow, as long as you make the next effort, you can grasp it thoroughly. The "Human Ear Sound" part requires not only listening more and listening more often, but also has rich experience in live music, a deep understanding of high-end well-known equipment, and more importantly, it requires a deep cultural and artistic foundation and an understanding of philosophy. Maybe not helpless. As Yu Yu said, "Kung Fu is beyond poetry", only learning to make poetry can only become a "poetry master", and only knowledgeable humanities and geography and other disciplines can cultivate the strengths of all families and create a "poetry talent" of Lei Lei. In order to deduce, we may say, "Kung Fu is outside of Hi-Fi", which only refers to the calibration and is a top-level requirement (for general Hi-Fi, as long as appropriate technical accumulation and Hi-Fi experience).
Regarding school calibration, in order to obtain the neutrality pursued by Hi-Fi, various types of music must be widely used for school calibration, because a kind of music often only covers a certain frequency or a certain number of frequencies, and uses various music to calibrate the sound. The entire frequency band can be adjusted to the best possible. In the music signal, I personally feel that the human voice may be the most complex and difficult to reproduce. The old saying that "silk is not as good as bamboo, and bamboo is not as good as meat" means that "meat" refers to human voice, and at the same time, human voice is People are the most familiar and picky. It is critical to replay the vocals. And vocals are very sensitive to the mid-band amplitude and frequency flatness, balance, phase frequency flatness, etc., so vocals are often one of the most commonly used methods for designers to calibrate.
When listening to vocal corrections, pay attention to mouth shape, positioning, and charm. The clear focus of the mouth shape and the accurate and stable positioning are all related to the straightness of the frequency response and the balance of the left and right channels. The rhythm of vocals has a great relationship with the straightness of the phase curve. Phase design is a technology that has just emerged in the world in the past ten years. The vocal of monitoring No. 1 is pure and beautiful. In addition to the contribution of the quality of the unit, phase design can not help No.
Others, such as the use of cello, cannon, drum sound to calibrate the low frequency, the violin solo to calibrate the high frequency and high frequency tones, and the percussion cymbals etc. to calibrate the ultra-high frequency overtone resolution, and large symphonies can be calibrated The width and depth of the sound field and the positioning of audio and video in large dynamic and complex scenes, while the piano has a wide sound range and rich overtones. The texture of the sound particles and the tone of the overtones have high requirements for the straight response of each frequency band.
When conditions permit, the school can use some internationally renowned speakers that have been rated for reference, such as the high and low frequencies of the ATC20 as a reference, or its balance degree as a reference, and Harbeth ’s 3 / 5A as a vocal reference. Take the reproduction of the big scenes of ATC and Alon as a reference, etc.
Here is a reminder for audiophiles. Sound calibration is an extremely complicated task. One is to repeat the calibration many times, and the second is to test in parallel with the sound calibration. Do not calibrate the speaker out of the theoretical guidance. Be sure to cross the sound and test. Carry out, to achieve a high degree of unity of art and theory.
The characteristics of the unit used for monitoring No. 1 have been introduced in many articles, and the product manual also gives the parameters and characteristics, so I won't talk more about it here.
As I write here, I want to revisit the old tune. The author believes that in the Hi-Fi audio industry, we Chinese can go to the forefront of the world, we can master some key technologies, and we can develop some of our own With advanced technology, it can be said that we must catch up with the world's advanced level in technology, as long as we work hard, it will not take too long, and our accumulation of more than 5,000 years of long culture makes our understanding of Hi-Fi have something that others cannot have. The advantages, especially the traditional Chinese cultural philosophy and modern Hi-Fi industry, are in harmony with each other.
We are determined to make the world's best Hi-Fi products, not our arrogant, but a realistic goal established after fully considering these factors. Of course, to achieve this goal, the efforts of our manufacturers are not enough. This must rely on the concern and support of the majority of enthusiasts for us, but also depends on the emergence of a batch of domestic rather than a few serious Hi-Fi manufacturers, forming a good industry atmosphere.
It is hoped that through this event, we will be able to more closely contact our enthusiasts and gain more support from the enthusiasts, so that we can take another big step on the hard way to achieve our ideals.
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