Speaker design and technology

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, for an acoustic length of the conduit several tens of Hz to half the acoustic wavelength, about a few meters long, so that between the front backward crosstalk acoustic wave phase although the same phase, but there is a time delay of tens of milliseconds, so most of the transmission line box 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 frequently dive, but vented using a lumped-parameter resonance workers inverting manner, instead of distributed parameter transmission line type half wavelength of the sound conduit inverted manner, so that although the same sound wave inverted, while 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). ), which is the same principle and vented, and beyond the scope of this addition, it is not introduced.

Inverted box and closed-box comparing 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. The actual design, a reference is only calculated, the final use to adjust the ear than the sound.

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 box size is too large, such as some domestic low high Q, high volume equivalent loudspeaker as glass wool need to reduce the actual volume of the tank, the advantages of using glass wool is not much, and the glass wool used in the speaker . Ordinary sponge, acrylic cotton or cotton wool length, can easily design a good sound quality of the speaker. Because the design volume of the No. 1 monitor is about 18 liters, the mid-foam through-hole sponge was used in the design.

Influence the selection and processing of sheet metal box to box the sound quality is great. 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. But within the damping effect of secret board is still not enough, we use the inner wall attached to special asphalt board formulated a method to compensate. Bitumen damping characteristics are more stable throughout the year plate, and an excellent degree of damping. 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 "only speaker sound, no sound box board," the ideal.

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 high as possible, attenuation slope the bigger the better, this one is only a superficial view to see the effect divider "minute", the second is mechanically seen by the low-pass filter divider problem.

About the Crossover, I want to talk a little philosophy, the country has been one-sided propaganda "into two", while ignoring the "combined", and in fact I think, "one divides into two" for the table, "co the second one "based, tweeter bright timbre, can metaphor as the" Yang "woofer deep deep timbre, can metaphor as the" Yin. " Male and female have opposite side, there are mutually inclusive side, the actual occurrence of the black and white fish ancient Taiji pattern, not a circle split into two halves so simple, but is yin yang tail head, end to end, Aioi technology, and black and white fish eyes, is the yin yang, yin yang within the so-called Yinzhi Yang to return to the divider, its role is not so much divided yin and yang, it is rather the blending, Melting Yin and Yang in one furnace. Imagine if the following crossover alone pronounce woofer, tweeter crossover pronunciation is more than a single unit, then the sound would not be fragmented, and audio-visual positioning will be jumping up and down, never without possibility to achieve 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, Voice and other two are not the same, "female" and "male" for the integrated organic, better sound 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-level filtering unit requires very high, if the crossover is low, but also low filter order, then, the power, the greater the burden tweeter, which is designed to monitor One treble filter with a second order, but one reason for bass with the first order.

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.

Second impedance compensation, because the bass crossover inductance can not be ignored in the role, it is to be properly impedance compensation circuit is better, but the compensation must not be too far, or would bring greater deterioration in timbre to the impedance of the compensation is not the minimum impedance compensation value is lower than the front curve best for attenuating the treble adjustment of sensitivity to L-type resistor network preferably, a single resistor without attenuation and the amount of cost savings, while the tone nor benefit.

Finally, mention that it must be bi-wiring is better, the problem of excessive treble after some friends as to say that some cabinet changes bi-wiring-line crossover is due to its original design is a single crossover, to counteract 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 speaker box-like design to make further adjustments need to be a series of tests, including a test impedance, the amplitude-frequency test, the test frequency and phase response curve distortion, or drowning FIG transient response, found to improve the problem, as 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.

In front of a lot of talk, technology is only part of the speaker design for high-level Hi-Fi is concerned, this may account for only four percent, while other art school sound the human ear for a good part of the design but it accounted for Liu Cheng. 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 wide and deep sound image localization in large and complex scenes dynamic sound field, while the piano wide range, rich overtone, harmonic texture and tone of its grain tone of the band's flat response, with high demands.

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. with scenes of ATC and Alon reproduced as reference and so on.

Here to remind enthusiasts, school sound is an extremely complex task, one to be repeated many times school, secondary school sound to be tested in parallel with, do not sound out of the speakers away from the school guidance theory, the school must be sound, test cross 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 advanced technology, can speak technically to catch up with the world advanced level, as long as we strive to not take too long, and our five thousand years long cultural heritage makes to our understanding of Hi-Fi has some of the others can not have The advantages, especially the traditional Chinese cultural philosophy and modern Hi-Fi industry, are in harmony with each other.

We are determined to come up with a world-class Hi-Fi products, we are not arrogant, but a realistic goal after full consideration of these factors establish, of course, to achieve this goal, even with our manufacturer's efforts 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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