Speaker unit quality characteristic surface view

The speaker unit determines the ultimate potential of the entire speaker, and plays a leading role in the performance of the whole HIFI system. In the present technology conditions are still not perfect, the target is still a few decades later, because it requires the unit with the same density of the air, in all the frequency is completely uniform motion, without any kind of distortion.

　　 In front of us is a long way, but it should be full of confidence. At this point in the field of material science is undergoing major progress, the past ten years has been a lot of results. I'm sure it will be a new breakthrough after two or three years.

　　We benefit from the great progress in computer simulation of mechanical behavior research, as well as a large number of studies conducted by the aviation, automotive and sports leisure industry for the use of lightweight high performance materials instead of expensive and heavy traditional materials. We now have the KEVLAR, carbon fiber composite material and aluminum diaphragm, not far from the future will have artificial diamond, ultra low density of silicon glass, new metal single crystal and carbon single crystals and new composite materials.

　　Why do speakers have their own different sounds?

　　The biggest challenge for the designers is how to ensure the uniformity of the motion, and eliminate the resonance in the middle and high frequency. This is a compromise that has to be made in a variety of speaker systems (except for the quality of the speakers). Other problems also have the nonlinearity of the cavity resonance and the magnetic field.

　　Uniform motion

　　Rigid means from the acceleration of a voice coil is precisely into the top over the entire surface of the acceleration in the cone or ball; it will be get a flat frequency response, rapid pulse rise, low intermodulation distortion and sound clarity.

　　Enthusiasts often this type of sound described as & quot; fast & quot; that make those to objective measurement for the engineers feel surprised Schrodinger, & quot; the bass unit how as soon as possible? Because the divider limits the pulse rise time, equivalent to one-fifth of the treble unit or 1 / 10, as the diplomats often say a sentence rhetoric & quot; comprehensive and frank exchange views & quot; or, the mutual exchange of misunderstanding.

　　It can be said that both sides are right, and they are wrong. They're actually talking about different contents. Fans have heard of the uniform cone motion; this phenomenon in the test performance in: no intermodulation distortion and flat frequency response, neat impulse response.

　　 Good, so why not put the cone basin or the ball to the top of the stiffness as much as possible? Like this metal. Its strength is good, and can almost be processed into any shape. The clock is made of bronze. But the problem lies in the resonance, which is the echo of tens of thousands of weeks.

　　There are two points, first, the metal rigidity; second, the only way to release the mechanical energy is through the air, because the air and the density of bronze is a great difference, resulting in poor coupling, air load damping is small, it is bound to take a long time. So we expect another performance of the speaker unit:

　　Self damping

　　We also hope that the sound circle can stop the vibration film in time, so that they can not make a sound. Unfortunately, most rigid materials (such as metals) have little self damping, leading to their long vibration. Control one solution to this problem is to heavy rubber folding ring stretching to cone below, and pay great attention to the centering support piece and a folding ring material damping behavior.

　　But the present situation is that, even though the best KEVLAR, carbon fiber or aluminum film is also at least one of the upper part of the working area of a high Q value, must be corrected with a frequency divider or filter. The worst is that the peak is generally between 3~5kHz, which is the most sensitive to the tone of the human ear.

　　Self damping can be eliminated by staining, and the acoustic characteristics of the relaxed, natural, and not easy to fatigue. A lot of fans and commentators for the special sound of unit material resonant completely unaware of, but due to the sensitivity of the amplifier or room.

　　Some magazines are recommended by 2 speakers using a 7 KEVLAR and a metal ball top. From a technical point of view, the loudspeaker unit of each work area in uniform motion, but actually it eliminate the Kevlar for 3 to 5 kHz energy vibration region segmentation, the divider is reluctant.

　　A review article on this type of 2 speakers is presented in a large amount of space and selecting a amplifier that is capable of full play of the speaker's quality. In fact, the sound commentator is forced to choose a low distortion amplifier that happens at the frequency of the split of the KEVLAR unit. Because most enthusiasts and commentator for the speaker unit of the direct sound very familiar with, they can not evaluate how many & quot; Kevlar sound & quot; or & quot; aluminum film sound & quot; be retained in the final design of the system.

　　There is also a problem plagued by all 2 KEVLAR, metal and carbon fiber speakers. At the present technology level, the 6.5 or 7 unit has to be played at the edge of its working range, so that the distortion is not too large to engage with the high frequency unit.

　　If you reduce the crossover point, the treble unit intermodulation distortion will surge, leading to listen to the sound frequency deterioration in medium and large volume. If you increase the frequency points, and the segmentation of the KEVLAR vibration, resulting in a lower volume of the sound before the rush, loud pressure is completely broken.

　　This allows the designer to face difficult choices: either in the entire high pitched sound; or the typical KEVLAR forward, and it is possible to bring the speaker system to the wild sound. Now the best way is to use the 4 order (24dB/Oct) frequency divider to correct the resonance of KEVLAR.

　　By the way, I'm very fond of KEVLAR and carbon fiber units. But they are very difficult to deal with, and must be used in the acoustic and electrical means to control their strong resonance.

　　As mentioned before, the rigid cone basin has some advantages, but the damping is very difficult. Another way is the use of high loss materials, the traditional plastic coated paper pots, but in modern times, they are gradually replaced by the PP. This type of cone basin can be damped by itself, and the impulse of the ring is gradually losing its energy when the film surface is spread. The requirements of the centering support chip and folding ring is not very strict.

　　The frequency response of such materials in the test is fairly flat, allowing the use of simple 6dB/Oct frequency divider. I have little interest in most of the polypropylene unit, they are in the middle of the sound of some vague. Although there is no use of B& K intermodulation distortion analyzer, but I assume that because they are very soft and has considerable intermodulation distortion. In addition, it is extremely difficult to produce a material that has a perfect linear mechanical decay. In fact, in the process of decay, there is always an inevitable distortion.

　　I think all the similar phenomenon also appeared in the soft ball top high unit; cone basin in fact in the whole frequency band vibration, the instrument is not measured because there is a strong damping cover, but people can distinguish. In order to overcome this subjective effect, the best units are made of composite materials, in the plastic of silica, mica or metal powder, both can significantly improve the stiffness and can keep the sound characteristics of polypropylene.

　　Cavity resonance

　　The top of the middle and low unit of the dust cap or the top of the upper unit of the unit is not harmful, but the dust cap is formed in a small cavity with the space between the magnet poles. One of the typical examples of this is the B110 Bextrene KEF (LS3/5a BBC), which was developed in the early 70's..

　　This unit may be the earliest a commercialization of high quality mediant unit, but it also has a lot of problems, such as low efficiency power under force is insufficient, 1.5khz is the width of the center of an octave response peak (by the divider correct), 4.5khz as the center of three high Q value peak (BBC design of three order frequency divider can only be slightly attenuated). Acoustic commentators attributed these peaks to the high - point unit, which has a strong directivity, which should be caused by the dust cap resonance.

　　1970s pop some tweeter, including audax and peerless 1" soft dome, also between the 9~16kHz has similar resonance peak, through the ball top and pole block is filled between the felt washer can be partially Damping off. Because the soft dome of the internal friction is much stronger than the B110 dust cap, the resonance is much wider, and the range is only system, but still exists, sensitive listeners will detect that a fatigue characteristics of.

　　It is not difficult to imagine, when FAQ speakers used phenolic plastics, glass fiber and cardboard on top of the ball is very bad. (hey, who remember the BIC Venturis? Cerwin-Vega? Rectilinear? JBL L100? I young had sales over the terrible products, waiting for customer with their audition Pink Floyd the dark side of the moon.

　　Return now, quality in the bass and treble unit with two kinds of methods to avoid the problem: Nordic manufacturers Dynaudio, scan speak, VIFA and seas with open pole piece assembly; bullet pole block expansion by a French manufacturer audax and focal completely replaced the dust cap.

　　Esotec D-260 Esotec, T-330D Scan-Speak, D2905/9000, Dynaudio, are used for the most famous products of the back wave of the open type pole block in transmission line. Their use on Faber Extrema (Sonus) ProAc and (noble) Response 3 speakers proved successful.

　　On the contrary, T120 T120K and Focal are used in the non damping cavity to use rigid glass fiber or KEVLAR inner concave spherical top, the high frequency of its working range is a series of high Q values, which is generated by the first division of the resonant cavity and the rigid ball. I am puzzled by the general praise of these units, I don't like their sound, and there is no special place to test the data.

　　However, from the various aspects, T120Ti and titanium oxide spheres model focal titanium ball top top T120Ti-O2 are very good recently I in the audition by speakers of the unit when it feels good.

　　Nonlinearity of magnetic field

　　Most know fancier speaker unit is inductive load, and it is wrapped around the pole coil magnetic iron block. But not many people know how to produce a lot of problems.

　　If the inductance value is kept constant, like the air core inductance, there will be no problem. Just use the R-C network to adjust the frequency divider. Unfortunately, it is an iron core inductor, and the inductance value is changed with the change of the position of the voice coil.

　　The change of inductance value is a serious consequence, because the inductance value is an important factor to determine the frequency of the upper end of the unit and the acoustic delay. Changing the inductance value, the frequency of falling down and the acoustic delay is also changed. When the unit moves to a considerable proportion of the sound cycle linear stroke occurs. With excellent 8 P21W0-12-08 Vifa as an example, linear stroke is only 8mm (+-4mm). Most 8 linear stroke unit is generally 6mm, midrange is generally 1~3mm.

　　Play some ultra low frequency modulation effect of inductance will let out, namely the intermodulation distortion in the whole spectrum and FM. This is a big problem for the 2 Road and 3 Road low frequency audio system. That is to say when you see the unit movement, has been the emergence of a large number of FM and intermodulation distortion. What's the sense of hearing? You will find that the low frequency resolution is lost, but it may be covered by the problems of the amplifier (such as the saturation of the output transformer, power supply).

　　What are the solutions? SD Dynaudio system and DTL Scan-Speak system with copper clad pole block will be the voice coil of the eddy current. Careful analysis of the sound coil inductance parameters can be found in this secret.

　　As one of the best 8 in the world, the 21W/8555 Scan-Speak, whose inductance is 0.1mH, is much lower than that of P21W0-20-08 0.9mH. These two units are very good, but if you want to send out at the same time and low frequency, Scan-Speak, of course, can give a more transparent sound.

　　The inductance value and a layer of meaning, high frequency unit drop by voice coil inductance and mechanical drop joint decision. If you use voice coil inductance value and DC resistance to calculate the fall frequency, the value of the measurement unit is often much higher than the measured acoustic drop. While others are calculated to be lower than the measured value. The reason is that the voice coil inductance to cover the peak of mechanical system. This is not a good phenomenon, any change in the mechanical system or electrical system will strongly affect the frequency response and transient response.

　　Incidentally, the same problem also appears in the old moving magnetic cartridge. Not surprisingly, this kind of cartridge than high dynamic cartridge is much worse in transparency.

　　Here are enthusiasts how to find your favorite speaker and draw their own conclusions, even the guesswork out of manufacturers, commentator and your friends' sound preferences.。

Speaker unit quality characteristic surface view [2]

Unit type

　　Familiarity and mastery of the basic characteristics of the unit is helpful for listening and contrast, and you can conclude that it is a good thing in the same unit. By listening carefully and studying all the relevant parameters, you can find out what the designers do when they are solving the problem.

1 Paper basin unit

　　The earliest in the end of the 20's Rice and Kellog's patent application documents. Paper quality can be said to have the difference, the worst may be in cheap radio find good such as the scan speak 5 speakers mediant for Thiel, seas 6.5 bass for Wilson watt. This ancient material is actually a composite structure, which can be changed significantly when using a suitable plastic coating (the choice of the coating is the business secret of the manufacturer's manufacturer). Because of the characteristics of the paper with the humidity and time and the occurrence of a significant change, the coating is indispensable, both stability of the material, but also to improve the self damping.

　　Advantages: good or even excellent self damping, excellent analytical and detail, flat response, gradually began to split the vibration. Relatively easy to match with the low order linear phase frequency divider. The sound of the paper is better than that of the measured data.

　　 Disadvantages: stiffness is not as good as KEVLAR, carbon fiber and metal film, so the lack of electrostatic type of detail. Sound pressure level is not as good as other materials.

　　The consistency of the paper is not good, so the pair is not very accurate, which may affect the performance of the knot, and of course the accuracy and quality of the product. Even after the coating treatment, with the passage of time, the performance is still possible to change.

2 BEXTENE Cone

　　This is a kind of plastic that is made of wood pulp, always used to control the first time in 15kHz. It was first developed by BBC in 1967 as a material to replace paper with better consistency and predictability in order to adapt to the use of listening. In the early 70's were widely used, then the typical fever speakers are often a 8 KEF or BEXTENE Audax in the with Audax 1.

　　From the design of BBC is always used to balance the BEXTENE unit in the middle frequency band to remain flat, the most famous unit is probably used for LS3/5a monitor B110 KEF. Now BEXTENE has been developed by the BBC to replace the polypropylene unit frequency response is more flat, no longer need to coat, and because the quality is reduced, the efficiency of 3~4dB. BEXTENE has retired from the stage of history.

　　Advantages: good knot like, more analytical than the majority of paper pots.

　　 Disadvantages: low efficiency (85dB/m), strong staining, in the not too large sound pressure burst vibration.

3 Soft dome

　　After the beginning of the 70's Peerless 1 "soft ball, gradually began to spread. Subsequently, Audax 1 "in the 70's and the early 80's by the United States and the United States, many of the designers used.

　　When the 1980s mid titanium and aluminum dome and focal glass fiber concave dome appears, these design fell out of favor, audax soft dome unit was extruded enthusiast market.

　　In the past few years, to Dynaudio and scan speak as the representative soft ball top treble again resurgent, they use the new ball forming top, new coating material and new design, its performance worthy comparable with any metal dome. Voice of the resolution and detail and best metal dome comparable, but no metal dome kind of typical 22kHz~27kHz resonant.

　　Advantages: inherent self damping and extremely flat response, first class impulse response. The natural, open, and no sense of fatigue is the most valuable quality of hearing the digital recording.。

　　Faults: soft ball old top sound dull. The power carrying capacity is limited, need 18dB/Oct frequency divider to reduce intermodulation distortion. Compared with the top of the metal ball, the high frequency divergence is even worse. In addition to the divergence of this aspect, the latest design has no other defects.

4 Soft ball mediant unit

　　Audition AR-3, AR LST, ads, audax 2 ", Dynaudio d-52 soft ball mediant after found they make a mess of the speaker system. It's flat, but it sounds like the sound is opaque, stained, and it is very tired.

　　Problem of is soft dome midrange unit linear displacement of the very limited (generally 1 to 2 mm). As a result, the bandwidth is limited, and even 500Hz frequency can well fit, just 800~3200 Hz range work best.

　　The second problem is they are prone to lateral offset, because there is no centering support chip to assist in the folding ring to maintain linear before and after exercise.

　　The third problem is that the stiffness of the wire is not enough to complete the high frequency band of the power conversion task.

　　The new generation of the cone basin, such as 5, 13M/8636 13M/8640, Dynaudio, 15W-75 Scan-Speak, is completely different. The three unit is actually high precision cone, rather than the Alto ball. They are similar to the top of the soft ball is a large dust cap, can play a role in the high frequency of the ball.

　　They clearly have a greater stroke, lower distortion, and a wider frequency response. Such units are capable of obtaining real and transparent sound. Because they are using KEVLAR, paper and polypropylene, the following will be introduced in detail.

　　Another example is the professional level ATC 3" the top of the ball (with cornet drum). It uses a dual damper, significantly reduces the intermodulation distortion. The performance is the best, but it is very expensive (about 300 dollars), and the need for manual selection in order to make the left and right channel resonance frequency match.

Advantages. Perhaps the metal ball mediant has potential, but they require the divider is very harsh. Note: the ATC unit as well as the cone basin - the ball is not included in this column.

Disadvantages: distortion, noise, high frequency, high frequency band and power are limited. Only laser holographic measurements can be found out of their defects.

5 Polypropylene unit

　　1976 BBC developed this material to replace BEXTRENE. Because it has a very strong self damping, the design of appropriate polypropylene unit without any equilibrium can be obtained in the working area of flat response. In addition, its efficiency is generally reached 88~91dB, but also a great progress.

　　Polypropylene has become a universal material, because in a loudspeaker it to manual processing of the minimum requirements, the only difficulty is to find a suitable adhesive, the problem in the early 1980s is solved.

　　Now, the Response ProAc 3 and System Hales 2 signature version of a variety of speakers are using polypropylene unit. The final quality of the unit depends on the shape of the cone basin and the addition of the polypropylene.

　　Advantages: if the design is correct, it can get a flat response, very low sound staining, good pulse response, frequency divider can be very simple, high efficiency, segmentation vibration appear slow. Good quality products can be done with the best paper pot is quite transparent.

　　Disadvantages: it is not up to the standard set by the rigid cone basin unit and electrostatic unit. Due to the difference in the analytical force, many of the polypropylene in the bass can not match with the popular metal ball. Not suitable for a 10 inch or larger bass unit, the carbon fiber should be more competent.

6 Metal dome

　　 In the mid-1980s, Germany in the metallurgical technology progress (ELAC and MB company) makes the thin titanium, aluminum dome was born now Germany, Norway and France have multiple vendors can supply this kind of element. Their voice can be very transparent, if properly designed and the performance of electrostatic loudspeaker be roughly the same.

　　The disadvantage is that the lack of self damping, but the performance of aluminum film on the ultrasonic frequency than be a stroke above titanium film. At this stage, all of the metal dome and the high - range of the high - and - high - range of the metal ball has a significant ultrasonic wave peak, its range from 3dB (excellent) to 12dB (general) range.

　　However the peak does not seem to affect large, because & quot; resourceful & quot; SONY/PHILIPS already in the CD to the Redbook standards ensures that the CD will not contain any above 20kHz music information. Perhaps when the concept of HI-FI for the super CD to achieve commercialization, we can get the upper frequency limit of at least 32kHz, parsing power to achieve the real 20~24 bit of the recording.

　　Advantages: uniform movement of the piston, the design of the right can produce a very high resolution of the transparent sound. The divergence is very good, because the curvature radius of the metal ball is larger than that of the soft ball.

　　Disadvantages: it may be due to the interaction between the ultra high frequency and the sound of the audible frequency band, which is generated by the interaction between the &quot and the metal &quot. Some early product power limited. In the whole frequency band, the vibration distortion is apparent when the strong overload is over.

　　7 Rigid element

　　Aluminum cone. First for Hi-Fi speaker of the rigid element is jordan 4 watts "aluminum cone, which is the manual production, high price, low efficiency, can not be universal, in the United States market almost can not see. Now some British speakers using 5 and 7 aluminum pot in the bass unit, its sensitivity is very low, but also to filter the frequency divider.

　　Foam basin. Another class of B139 KEF as the representative of the bubble bass unit, but its efficiency and power are very low, if there is a serious high Q resonance. The peak of B139 in 12dB is 1100Hz. They were widely used in the 3's and 4's transmission line speakers in the 70.

　　Carbon fiber. The next generation is the Japanese development of carbon fiber, the earliest is a professional recording studio 12 TAD, the efficiency is high, the price is very expensive (in 1980, a about 300 dollars). Now, the price of carbon fiber has been reduced, Vifa and Audax have a very good product. Of course, Japan's output is much greater..

　　Carbon fiber unit has a real piston movement, the low-frequency and middle frequency response is very outstanding, but in the frequency of the segmentation of the vibration is very annoying, must be modified by the complex frequency divider.

　　Although I don't like to complex filter unit, it must be admitted that, VIFA 8 "and 10" carbon fiber element is only makes me really feel low frequency of direct radiator.

　　KEVLAR。KEVLAR unit in the 80's in the middle of France Focal and Germany's Eton product line, Eton unit due to the middle of the two layer KEVLAR added a high loss honeycomb structure and has excellent damping characteristics. The Scan-Speak KEVLAR unit of Eton and update shared the world most outstanding high technology of speaker unit name.

　　 In the new KEVLAR Scan-Speak unit can be found a unique and we are eager for the characteristics, that is, the smooth fall. All other KEVLAR units will be in chaos, and the Scan-Speak is the only way to get a good control, so it is obviously improved in terms of smoothness and transparency.

　　Complex basin. Audax re entering the High-End market with a special composite material technology HD-A. It is made of a certain proportion of mixed granular carbon fibers and KEVLAR fibers in acrylic acid. Factory test results show that it combines a good piston motion with a minimum of high frequency peaks, as well as a smooth high frequency drop.

　　Recently, Russian scientists have realized the low cost of diamond vapor phase coating, which can be used on computer disks. Hope Scan-Speak and other manufacturers can quickly use this technology.

　　The advantages and disadvantages of rigid unit

　　Advantages: the best transparency, and the sound of the sound field, and the design of a well - designed, or even beyond the level of an electrostatic speaker. High efficiency, high sound pressure level, low intermodulation distortion. This type of unit is regarded as the most advanced by many designers, and with the development of material technology, there may be rapid progress.

　　Faults: the old design has a severe peak in the upper end of the working frequency band, and almost all of the units are not controlled by the high frequency peaks. This will lead to a long time to listen to the fatigue as well as the compression of the sound field.

　　Because the high frequency of KEVLAR and carbon fiber can not be corrected by ordinary low pass filter, the speakers of these elements must be properly designed for the appropriate frequency divider.

　　Because the high frequency peaks of KEVLAR and carbon fiber can not be corrected by ordinary low pass filter, these single, although they can have a lot of sound pressure level, but often in a split vibration, and the cutting of the amplifier is very similar to the. Some Kevlar and carbon fiber unit needs a long  a burn-in  time (more than 100 h), in order to make cone basin in the fiber softening; this is a drawback, indicating that the instability of the mechanical properties of the materials.

　　Method of evaluating unit

　　I choose the method seems to be the original speaker, I put the unit on the IEC boards audition. Without frequency divider, also do not have the box body. Listen to pink noise to evaluate how much of the potential analysis of the FFT and the sine wave and the peak of the peak in the measurement of the waterfall is how much it is to listen to the music. This does require your ears to be trained, and the process of listening can make you realize how complex the frequency divider is.

　　Then, I will carefully analysis mlssa computer testing system the results (using the same IEC baffle) and investigates the following contents: the impulse response; with respect to the frequency response of the group delay; cumulative attenuation spectrum waterfall; within the working frequency of the frequency response flatness.

　　Listening and testing can be said to be equally important, the two can only reveal part of the real characteristics of the unit. Even today, the best sound system of fever, in 5 years, may be found to have serious flaws. Through the test can find out the problem of the sound, and it is now the audio equipment can not be exposed. MLSSA system helps you solve these problems.

　　A thoughtful designer should be as famous craftsman that treat their works and even treat from the outside can not see the hidden part, also didn't hesitate to pour all thoughts.