Detailed explanation of full-band speakers

Why talk about the speaker unit? Simple, because what you hear is from the unit. No matter how powerful speakers (or no speakers) are used, and how perfect the crossover, if there is no good unit, everything is still in vain. Therefore, the unit is very important, this point should be beyond doubt.

So, what's so great about a mid-range unit that doesn't go up and down? But there are many people who say that the midrange is the most important frequency band for audio sound. If you have been so bored like me, try to listen to Cai Qin singing with a single tweeter, or Paganini's violin song with a single bass unit, you will deeply appreciate the cuteness of the midrange unit. I think you will also agree that if you are forced to listen to music with only one unit, you will definitely choose something that looks like a midrange unit. There is no other reason, because you know (or guess) that it will emit a mid-range frequency band, and the hearing of our people is mainly within this range, and the main body of music is here.

Design of midrange unit

The concept of the "one-finger Jiang" treble last time can be extended to the midrange range, because any sound-generating unit can be deconstructed into a sound-generating diaphragm, diaphragm suspension, and drive system. Only because of the different working frequency bands, these components have gradually evolved to a certain range of size after so many years of evolution. However, there are many changes in its shape and material, especially the diaphragm material, which can be said to be full of variety in recent years. Let ’s take a look at them one by one:

Paper cone diaphragm

This should be considered the oldest material. Simply put, the pulp suspension flows into the pre-designed pot-shaped network mold, the pulp is deposited on it, the pulp deposited to an appropriate thickness is copied out, and then subsequent processing such as drying is performed, which becomes a paper bowl vibration. membrane. The composition of the pulp, such as the type, length and filler of the fiber, and the papermaking process and post-processing method (such as air drying or hot pressing), will affect the characteristics of the final product and also directly affect the sound characteristics. These are, of course, business secrets that have not been circulated (Note 1) ...

(Note 1: I read an article about the making of paper basins written by Mr. Hong Huaigong's appearance many years ago. In addition to the profound and profound knowledge contained in paper basins, I deeply admire the research spirit of Senior Hong. In this article, I have lightly described a few sentences, but I ca n’t tell the essence of the blood and sweat accumulated by the sages and martyrs over the years.)

Generally speaking, the sound characteristics of paper cones are smooth and natural, bright and clear without nervousness. Because there are countless fibers intertwined with each other, the energy transmitted in it can be quickly absorbed and form a good damping, so the resonance of the basin split caused by the high end of the sound frequency domain is not obvious, and the roll-off cut-off band Very smooth. This can be said to be a very good feature, because it allows you to use a very simple crossover, without additional cutting, the system integration is also very healthy. In addition, the rigidity of the paper cone is quite good, and it has a good performance on the details of the transient response and hearing. Don't look at the papers that are common at hand are soft. Under the proper shape and thickness, the rigidity of the paper can be done very well. Furthermore, if designed and made properly, the paper cone can be made very light, more than 15% lighter than the lightest plastic diaphragm. Although the paper is a bit heavier than the latest high-tech synthetic fiber materials, it is actually not much different, so the sound efficiency is high. Audax's 6.5-inch paper cone midrange PR170 series has an efficiency of up to 100dB / W. The possible weakness of the paper basin is that its characteristics will change with the ambient humidity. Since the paper absorbs moisture, its density will become higher (heavier) and the rigidity will become worse (softer), so the characteristics of sound will also be affected. It is difficult to say whether such a change is good or bad. Members of the Lowther Club in the United Kingdom declared that the lowther speakers at home were particularly nice when it rained. What is more worrying is that after more dry and wet cycles, it may cause fatigue of the material itself, and then change its original characteristics. But you can see that many antique paper basin units still sing well after working for decades, so this situation should be slightly and gradually, a bit like it enters another steady state stage after aging, and it is for our users. It should not be a problem. A large part of the paper cone units produced in recent years have various improvements in this regard, so that the characteristics of the paper cone can be more stable. It is common to have a surface coating film or to make an article on a paper formula. Some manufacturers claim that their paper basin is waterproof. From the perspective of some outdoor PA speakers, it should be quite reliable. Of course, as mentioned earlier, for these kinds of things, we generally look at the liveliness at most, and it is not so easy to see the doorway. In addition, don't equate the long history of paper cones with "outdated". Viewed from the perspective of the overall audio industry, the proportion of paper cone speaker units steadily ranks first among various units. Do not believe look at your home TV, portable radio recorder, bedside stereo, computer ... etc., are most of the small speakers using paper cone units? You say, hi! How can these things compare with my high-tech High-End speakers! But from another perspective, if these "secondary products" are replaced with non-paper cone units, it is guaranteed to be more unpleasant and more expensive. This is because the material of paper cones can be said to be quite mature, so it can achieve a good cost-effective ratio. In addition, there are many legendary old speakers that have stood the test of time and super-produced new generation overlords with paper cones: WE / Altec 755A full range, Goodman Axiom 80 full range, Altec A5 / A7, AR 3a, Lowther's full range, TAD ... and many other races can't be prepared. Some senior players who love this are even more straightforward: "Give me a paper cone, the rest is free!" Many people also think that it is better to say that the production of paper cones is an art, which is fascinating. Charm.

Plastic diaphragm

Due to the development of the petrochemical industry, plastic products can be found everywhere in our daily life environment. Low-cost raw materials and simple and natural processing procedures have won the favor of various industries, including of course the audio industry. The plastic diaphragm mentioned here refers to an integrally formed cone made of plastic injection molding or other methods, and the most commonly used material should be polypropylene (Polypropylene, referred to as PP). This kind of PP material should be the most commonly used products such as microwave oven containers and crispers, which are injection molded. In addition, it is often used for reinforcement of various types of cartons. The yellow or gray packing belt is also made of polypropylene fiber. From this we can realize one thing, this material is really very tough. The physical characteristics of most high-molecular polymers are extremely tough, because the molecular structure is huge and the arrangement is irregular, so the mechanical energy will be quickly absorbed and consumed when it is transmitted, and the damping characteristics are very good. This advantage is similar to a paper cone, except that the high-end slide is very smooth. In addition to being soft and natural in hearing, it is also a benefit to use a low-end, simple crossover. We can feel these good characteristics from many European two-way small speakers. The 6.5-inch transparent PP diaphragm Scan mid-bass unit used by ProAc can be called the best example of this type of unit. However, compared with other diaphragm materials, PP has poor rigidity and heavier quality. Although it is very painful to use the fresh-keeping box to go down the forehead, it does not mean that it has good rigidity under microscopic high-speed and small-range movement, and this working condition is what we care about when selecting the unit diaphragm. . The weak rigidity of the PP material causes high-speed micro-action (when working in a high frequency band), and the kinetic energy emitted by the voice coil cannot be completely and uniformly transmitted to the entire diaphragm, that is, the "basin split phenomenon" occurs. Although there is good damping to stop the basin splitting resonance, after all, it is no longer possible to make perfect piston movements. The distortion rate is relatively improved, and the sense of hearing is more supple, but the resolution and dynamics are not enough. Some 8-inch PP diaphragms The two-way speaker based on the woofer will be prone to symptoms of sluggishness in the mid-range to mid-high range, which is the cause. If you don't want to be too greedy in the bass part, choose a unit with a smaller diameter to alleviate this problem to some extent. Because what is worse in the snow is that the thickness required to be sufficiently rigid in a large area is relatively large, and the overall quality will increase. So, on the other hand, you can't find high-efficiency speakers that use PP diaphragms. Although it does not have the problem of water absorption like paper cones, PP diaphragms tend to change their characteristics with temperature. Fortunately, this should not bother us, because just like the problem of paper basins and humidity, such changes should be slow and gradual, don't worry too much! Looking at the above, it seems that PP is not suitable for making diaphragms because of the relationship between poor rigidity and high quality. In fact, it should be said that we have to make choices under many compromises. Like the Scan unit mentioned earlier, although using the PP diaphragm that I have criticized badly, it can still make a very successful product, and the overall performance is also very good. Or, a more active approach is to improve this material, that is, based on PP, and then add some additives to strengthen its rigidity. This action can indeed bring a certain degree of improvement, so that the produced unit has different degrees of progress in dynamics, distortion rate, detail performance, and vocal efficiency. For example, Dynaudio and Infinity / Genesis have units that use this type of processing. Although the additives and production methods mixed are not the same, the results are quite obvious. In addition, since petrochemical raw materials and injection molding are so convenient, of course some people will develop new materials that are different from PP, such as Bextrene, TPX, or Neoflex. The chemical composition is unknown. Although they look very similar to PP, these The better rigidity and lower quality of the materials can bring better dynamics and resolution. You should be able to see the above materials from the advertisements and catalogs of various speakers. You may wish to verify them when you have the opportunity.

Metal diaphragm

Since the weak rigidity will lead to the lack of dynamic and analytical force, the use of high-rigidity metal materials to make the diaphragm should get good results. If you do n’t talk about the compression driver for horn speakers, you can generally see the metal material used for the midrange or woofer used for direct radiation. It should be aluminum metal or its alloy products. The biggest advantage is the strong rigidity. It will not deform under a certain range of working conditions, and the result is very low distortion and good detail resolution. But the other side of strong rigidity is the low internal loss. Just like the "One Finger Jiang" treble I mentioned last time, the energy will not be absorbed by the diaphragm material itself, so there will be a clear formant when the basin split Appears at the high end of the frequency response, if not properly handled, it is easy to appear "metallic sound". The so-called proper treatment can first suppress this formant in the design of the crossover, that is, arrange the formant at or outside the cut-off band of the filter, so that the signal entering the unit does not contain frequencies that will stimulate high-frequency resonance , So the formants will be "hidden" by the crossover, and we will not hear the metallic sound. In order to achieve this goal, it is usually necessary to adopt a frequency division slope of at least second order or above to effectively filter; if the first order is used, the slope is too slow to effectively suppress. If you move the crossover point to the lower end, you will sacrifice the available bandwidth, which is not very healthy. Therefore, high-order frequency division and careful selection of frequency division points must be paid special attention to when using metal diaphragm units. Or, compared with passive avoidance, it can also positively improve the shortcomings, that is to strengthen the damping of the diaphragm: sandwich sandwich structure, coating damping material are all good ways. There are more and more products of this type on the market, and there are also quite a few successful examples, such as the Elac introduced in the last thorough study, or the Swiss Ensemble, whose sound and price are very expensive. In addition to the high frequency resonance is not easy to deal with, the weight of the diaphragm is another disadvantage. Because of the cost, I have not seen a midrange unit made of titanium. Therefore, although the midrange or woofer of the metal basin can perform excellent dynamics under strong driving, the overall sound efficiency is actually low, and generally requires a large amount of power to serve.

Synthetic fiber materials always seem to be the most advanced materials used in murderous weapons first. It is really the greatest sorrow of combative humanity. If it is used on audio to let everyone listen to music, is it not peaceful? Many years after boron carbon fiber and honeycomb sandwich structures were applied to fighter planes to achieve excellent results, some people used such materials for audio. Since it is an aviation-grade material, of course, it has the dual advantages of light weight and high strength. It can be lighter than paper, stronger than metal, and not only stronger than aluminum, but even higher than steel (Note 2 ), The diaphragm used to make the speaker unit should be ideal! Therefore, various manufacturers that manufacture Kevlar or carbon fiber units have touted their high rigidity, low mass, and high damping characteristics. The first two advantages are valid, but the self-damping term depends on the conditions, and is not necessarily better.

(Note 2: This refers to the best results that can be obtained by other forming methods. It does not mean that the thin unit diaphragm can make your kitchen knife still hard, at least not currently.) If it is not properly handled, This kind of high-rigidity man-made fiber will face a similar problem with metal basins, that is, high-frequency basin split resonance. Although it is not as serious as a metal diaphragm, this basin splitting resonance does exist and easily reaches the level of annoyingness. Without proper treatment, it is easy to cause hard upper mid-range and high-frequency lower sections, and it will start to be harsher. I read a review of equipment a few years ago, and the main pen was a bit cryptic about Kevlar's performance. Under the conditions of enhanced damping treatment (such as sandwich sandwich or coating film), plus appropriate frequency division, such units can show very good detail resolution, instantaneous response to stop, excellent large dynamic and micro Dynamic, and these good performance only needs a little power. For example, Focal ’s Audiom 7K, which is coated with Kevlar and polymer foam sandwich sandwich diaphragms and latex, can achieve an efficiency of 98dB / W. Even if it is slightly inferior to the 100dB / W of Audax paper cones, the performance is quite outstanding (Note 3).

(Note 3: Comparing the data of these two units, it is found that the magnet of Focal Audiom 7K is significantly larger (1132g Vs. 880g), and the quality of the vibration part is also lower (7.3g Vs. 9.1g). Audax with a smaller "firepower" is lower. It can be seen that other links such as suspension compliance, magnetic circuit system design, voice coil, diaphragm shape, etc. still have a lot of knowledge and compromise.) In the more common Carbon and Kevlar Fiber unit products In addition, a special man-made fiber diaphragm came out a few years ago-HAD (High DefiniTIon Aerogel), launched by Audax, using acrylic polymer gel and a variety of synthetic fibers (including Carbon and Kevlar) Cheng (Note 4), the performance is very good. From the measurement, it can be seen that the transient response is very good, the distortion is extremely low, and at the same time, the smooth high-frequency slip characteristic can be obtained. There is no high-frequency resonance peak at all. Although the product is not as good as the paper cone or Kevlar in sound efficiency, it should be the difference caused by the design intention of the magnetic circuit system, and the strength of other projects can not be underestimated. SWANS invited Stereophile's famous author MarTIn Colloms to design the Sanyin Allure, which uses this type of unit. My own short listening experience is easy and natural. The paper cone unit is as good as above, and the resolution and dynamic performance are more modern. Listen Without any bad insularity, it can be called a very successful unit design (of course, the system should also be credited for proper integration).

(Note 4: The mixing process of this gel and fiber is very special. From the beginning to the completion of the process, the volume of the gel will be reduced to one-tenth of the original. Even better, in this process, the polymer bonding The long-shaped molecules will grow along the fibers added in advance, so the molecular arrangement direction is controllable, and the excellent rigidity and self-damping are derived from this.) Other materials In fact, in addition to the above four categories of materials , There are many other lightweight and strong materials that can be made into speaker diaphragms, such as glass fiber, celluloid fiber, graphite fiber, bakelite, silk fiber, expanded polystyrene, various foamed plastics, And vacuum sintered precision ceramics ... etc., Many of these materials are promising, some are suitable for treble, some are suitable for midrange, some are suitable for bass, and some are suitable for high and low bass. I even heard someone in Japan develop a kind of special plant (that is, mold) and follow the designed mold to "grow" a cone! It is said that its natural sound is beyond any material. However, I think it is difficult to import such a product into mass production because the cost is too high (time cost). (One thing to remind here is that the diaphragms of many units will be made so that you can't see what the material is; or conversely, they are made "much like" a certain material. Basically, this is almost counterfeit Behavior, as helpless consumers, we can only be careful)

Magnetic circuit system

Having seen all kinds of diaphragms, let's take a look at the magnetic circuit system again. In the first two issues, Mr. Chen Yunshuang has introduced a lot of magnet materials, which will be skipped here, and the discussion will focus on the overall design of the magnetic circuit system. Strictly speaking, the magnetic circuit system should include the voice coil part, instead of only the magnet and magnetic pole structure, because they act together, they should also be considered in the design. Simply put, the reason why the sound cone can move is by the voice coil, and the action of the voice coil is based on the interaction of the magnetic force generated by the change in current and the fixed magnetic field generated by the magnet and the magnetic pole. This principle should be familiar to everyone. . Among them, the design of the voice coil and the width and length of the magnetic gap have many places worth discussing. The voice coil design, as the name implies, is a coil used for vocalization. It is made of enameled wire and a special adhesive tightly and neatly wound on the voice coil tube. The material of the enameled wire is copper, aluminum, silver or other alloys, and the shape of the cross section is mostly made into a rectangle or a hexagon, in order to achieve the maximum winding density, that is, it can be wound under a certain voice coil length (Note 5) More turns, and more turns means greater magnetic force, better driving force, and higher acceleration coefficient of the cone. The result is the ability to have high efficiency and large dynamics. In the case of a flat wire voice coil, if the cross-sectional shape is a flat rectangle with a length to width ratio of 1: 5, the short side will be placed against the voice coil tube when winding. The voice coil is 30% higher than the acceleration coefficient, efficiency and dynamics.

(Note 5: The length of the voice coil refers to the length of the wound voice coil in the axial direction, not the length of the winding.) The total pressure of the voice coil wound on the voice coil tube is very considerable. You can do a simple experiment: use a piece of string (sewing cotton thread, nylon fishing line or dental floss) to make the third force tightly wrap around your finger, just wrap it ten times, see if there is What result? I believe you will rush to release it in a few seconds. The voice coils of some units are wound under high tension, and the total pressure exerted on the voice coil cylinder can reach tons! Therefore, the voice coil tube must be very strong. At the same time, in order to resist the heat of the voice coil, the voice coil tube must also be quite heat-resistant. Generally, the cylinder is made of aluminum (alloy), Kapton, or other lightweight, high-strength, and heat-resistant materials. Some more sophisticated manufacturers will perform multiple heat treatments on the wound voice coil combination to achieve better stability. Klipsh ’s Jim Hunter mentioned in an interview with “Speaker Builder” that they had received a speaker sent by a customer for repair, in which the treble horn driver had fallen from the fused plastic horn throat. It can be seen that the entire driver was really It's so hot, but the voice coil group is still good after it's disassembled! There are two dilemmas in determining the size of the voice coil. If you need driving force to achieve high efficiency and large dynamics, a long voice coil with a large diameter should be able to take on the big responsibility; And high frequency response. The long voice coil means that only part of the voice coil is covered by the magnetic gap, so that the magnetic field in the magnetic gap has a weak control force on the voice coil, and it is easier to be modulated by the magnetic field generated by the voice coil, resulting in higher distortion. If the voice coil is made very small, although it is very light, but the driving force is too weak, it can not achieve the ideal sound efficiency and control force, and the power is also limited. Therefore, factors such as the size of the voice coil, the area and shape of the diaphragm, and the magnetic force of the magnet should have an optimal compromise. Magnet and magnetic system Let's take a look at the structure of magnet and magnetic pole. Traditionally, the magnet in the speaker unit is axially polarized, that is, the direction of the two poles of the magnet is parallel to the direction of the central axis of the hollow cylindrical magnet, and then the magnetic pole made of the magnetic conductive material is used to guide the magnetic force lines into the magnetic gap Loop. What is needed for the voice coil movement is the radial magnetic field in the magnetic gap, that is, the direction of the magnetic field is parallel to the radial direction, and is concentrically convergent or centrifugal. The total magnetic strength and magnetic flux density in the magnetic gap are derived from the magnetic force of the magnet, and this is related to the type and size of the magnet. The magnets used in most of the units are ferrite ceramic magnets (iron oxide), because this material has a good resistance to temperature changes, has a strong resistance to demagnetization, and has good mechanical strength and corrosion resistance. The most important thing is the low cost. But the disadvantage is that the volume and weight of the unit magnetic force are very large, so in order to achieve high efficiency, you will always see a huge magnetic circuit structure.

Needless to say the tweeter or horn driver, the diameter of the magnet must be much larger than the diaphragm. For some mid-range units from 6 inches to 7 inches, the magnet diameter can also be as large as the diaphragm. Even some professional 10 to 12-inch mid-bass, the magnet diameter is as large as the diaphragm! High magnetic force is what we want, because it can bring high efficiency, high dynamics, high control force and other benefits. However, in addition to the seemingly more majestic and powerful, large-sized magnets may not have any advantages, and even have some adverse effects on the propagation of sound waves. Because the large-diameter magnet is directly behind the diaphragm, the sound wave on the back has to be squeezed out from the surrounding sides, and some of it will be directly reflected back to the diaphragm. If this unit is fixed on a very thick baffle, the situation will be even worse, because the distance between the diaphragm and the magnet may be about the same as the thickness of the baffle. If there is no additional processing, then the back wave will be left over "Squirting" between a circle of narrow slits. At this time, the back of the diaphragm is faced with very strong short-range reflected waves and dramatic pressure changes, which have a serious adverse effect on the overall frequency response and distortion. Therefore, if a unit with a large magnet structure is used, the inner surface of the baffle must be properly processed to cut out the channel so that the back wave can be smoothly exported, such as Theil's speakers. Or use a high-strength and thin metal baffle to avoid this problem.

In fact, looking further, the frame design of the unit will also face similar difficulties. Like the old frame stamped from iron plate, it has a wider support part. If it is close to the cone itself at the same time, it will increase. The reflection of the back wave causes sound stains. The new aluminum casting frame can make a more ideal shape, while taking into account the strength, beauty, and practicality of bass dyeing. Or, use high-magnetism and small-volume magnets to make the unit back wave fully stretch. About five years ago, the mid-range unit used in the three-way speaker introduced by Vendersteen (Note 6) was specially customized to Vifa, using a small Neodymium magnet. The Bishop of Wilson Benesch's flag, because of the special face-to-face Isobaric bass design, the magnet of the unit is directly facing outward, so in addition to the use of newer strong magnetic miniaturized nickel iron boron magnets, the magnetic poles are also made into arc streamlines, even The frame also achieves the smallest orthographic projection area under the high-strength pre-problem, which solves all the problems mentioned earlier. And the legendary full-range unit Lowther I mentioned many times, although it has been around for decades, has also paid close attention to this problem. Although the magnet used by Lowther is large, it has been streamlined as much as possible in shape, cleverly making room behind the cone, and the frame support part is also designed to face the direction of sound with narrow sides to reduce back wave obstruction Efforts can be said to do everything. In addition to the above problems, there is another factor that affects the performance of the unit, that is, the action of the voice coil in the magnetic gap and the interaction with the magnet. Strictly speaking, the action of the voice coil and the magnetic system is actually pushing or pulling each other, only because the magnetic system is fixed by the frame and the baffle, so it seems that the magnet is driving the voice coil.

(Note 6: The design concept of the Vendersteen speaker factory is quite correct and healthy. The cost is always spent in invisible places. The appearance and packaging are extremely simple and economical. The sound performance is quite satisfactory and the music is also good. It should be a good companion for lovers. It is a pity that the body shape is less pleasing, and it must not be favored by local agents and consumers)

After recognizing this fact, the resulting problems are: First, the magnetic force generated by the voice coil itself will demagnetize the magnet, so the magnet must be able to stand up, the dynamics, driving force and efficiency will not be compromised. The ability and characteristics of magnets to resist demagnetization will also affect the characteristics of vocalization. Speakers using Alnico magnets have attractive sounds in the mid-to-high range. I believe this is related to this factor. Second, the magnetic force generated by the voice coil itself will disturb the originally constant magnetic field in the magnetic gap, causing distortion. This problem can be solved by using copper-plated magnetic poles or inserting copper short-circuit rings to eliminate the modulation of the magnetic field, thereby greatly reducing distortion. This technology is especially obvious for the improvement of intermodulation distortion of the mid-bass unit. Because the low-range sound requires a long stroke and a short and fast mid-range, it will increase the complexity of the magnetic field modulation. The dilemma of the magnetic system Vs. Innovative polarization direction and magnetic pole structure When I first talked about the magnetic system, I mentioned that traditionally the magnets in the speaker unit are axially polarized, but in any case the final voice coil needs It is a radial magnetic field. So why not make the magnetic field of the magnet radial in the first place? Because it is difficult and expensive to manufacture, it was not until about four or five years ago that it was proposed to use radial polarization to manufacture the speaker unit. First, what are the disadvantages of the traditional axial polarization structure? 1. Large volume; 2. Difficult to achieve high magnetic flux density and deep magnetic gap. The problem of bulkiness has been discussed before, let's talk about what is wrong with the magnetic gap. The magnetic gap length of the traditional magnetic system can be said to be equal to the thickness of the upper pole plate at the magnetic gap end. Under the same magnet condition, to achieve a higher magnetic flux density, the magnetic gap width can be reduced first, but this will make the sound The combination of the coils is difficult and increases the cost; in addition, the magnetic flux in the polar plates cannot be saturated, so the material and thickness of the polar plates must be considered. In addition, if you want to achieve a combination of long magnetic gap and short voice coil, you will inevitably face the dilemma of reduced magnetic flux density. With a shorter voice coil, the overall sound efficiency will be reduced to very low. Although such a configuration can obtain better power linearity, but to simultaneously achieve high efficiency, it is necessary to overcome many dilemmas.

For example, Altec 515 series and TAD 160X series adopt the structure of short voice coil and long magnetic gap, which achieves excellent power linearity and at the same time has super high efficiency. It is really not easy. It can only be said that this is another An illustration of people fixing the sky. If a radially polarized magnet is used, a magnetic system with a high magnetic flux density and a long magnetic gap can be easily achieved (the cost is still not low, but the physical dilemma is less), and the magnetic flux density of the magnetic gap length can exceed the traditional structure Several times, means that the linear stroke of the unit is also several times more! The distortion under high sound pressure operation is also very low. This looks very suitable for the reproduction of bass. There is now a product that is an 18-inch bass (7) for professional use. It is said that its maximum linear sound pressure is unbearable. The distortion is still very low!

(Note 7: Aura Sound 1808, please note that this is not B & W's sub-brand Aura, but another company.) Unfortunately, so far, I have not heard of a midrange unit made in this way. Although the midrange does not require long-stroke movements, such a structure can achieve a small size and strong magnetic force, which are two major benefits for midrange sound. I believe that there is such a thing in the laboratory of a speaker factory, and soon there will be a number of products coming out, we will wait and see. Step into the full range? Isn't this article talking about the full-range unit? No wonder, no wonder! It is because there are too many problems facing the whole range of sounds, which cannot be explained at once, so I want to cut in from the midrange and extend it to the two ends, so that the overall concept will be clearer.

Because the conditions for an ideal speaker unit (regardless of high, medium and low) should be: one, low distortion; two, good power linearity; three, high efficiency; four, the wider the effective operating frequency band, the better. If we take the fourth term to the extreme, it is a full-range unit. In the next issue, I will introduce how to use the midrange unit as the basis to extend the sound to the full range. Among them, the many dilemmas that will be encountered and the ingenious solutions of various brands are also very exciting. Please wait and see. At first glance, it seems that it is not very complicated. As long as a midrange unit emits more treble and bass, will it become a full range unit? Look at those car stereos, computer speakers, portable tape recorders, and bedside stereos. Isn't that kind of unknown "full-range" unit everywhere? It doesn't seem to be too great, shouting! Things are not so simple, do you know how wide the frequency bands of these unknown units can be? I do n’t think you can easily hear it without providing the measured data. It ’s already a good work if those speakers can make clear vocals. Drums and cymbals are often just for identification. Bass sounds and treble percussion instruments are more common. In the void of nothingness. Pipe organ? Overtones for stringed instruments? Piano reverb? no kidding! As for how to call it full-range sound, please refer to the description in the sidebar. The next thing we want to discuss is what problems and dilemmas will be faced in designing a unit to cover all the audio ranges. Low-end extension problem. In terms of appearance, if the size is similar, as if it is about 6 inches or 7 inches, the difference between the cone midrange and the woofer is really limited. At most, the woofer has more The wide and soft overhanging edge, the other parts seem to "look" the same. But this is only a general rule, and it is not necessarily universal.

So, if you are given a 6-inch to 7-inch midrange unit, is there a way to change it to produce bass? If you only want to get bass without regard to sound pressure and distortion, it should be possible. In general, the lower limit of the operating frequency of a unit can be roughly seen from its free resonance frequency (Note 1), which is generally habitually marked as "fs". So, how to lower this frequency? Acoustic (acoustic) impedance (Note 2), mass of the vibration part, magnetic strength, and suspension compliance should be the key elements. Among them, the acoustic impedance (or simply referred to as "acoustic resistance") is directly related to the sounding area and the operating frequency. If direct sounding with the same size and the same frequency band work, this factor can be regarded as equal and need not be considered (sound resistance concept For the reproduction of bass is closely related to the sound efficiency of the whole frequency band, I will talk about this topic again next time). So, let's discuss several other elements first. Let's look back at the behavior of the unit diaphragm when working in the low frequency band. In fact, shallowly speaking, the low-frequency action is a "slow" reciprocating motion, and the number of round trips per unit time is small, which is the low frequency. So, in terms of basic physics concepts, under a certain amount of force, the acceleration of an object is inversely proportional to its mass. Therefore, under the same or similar conditions, the larger the vibration mass of the unit, the lower the free resonance frequency. Therefore, if you take a closer look and compare the data of the various units, you will find that this factor is inseparable. If the free resonant frequency of a woofer above 15 inches is below 25 Hz, the mass of the vibration part is often as high as 100 grams or more.

To lower the free resonance frequency of a unit, the simplest thing is to increase the quality of the cone. However, this is really not a good idea, because a heavy cone is bound to bring inefficiency and poor high-frequency extension. Therefore, it seems that this road does not work. So, next we can reduce the external damping of the cone-there are mainly two factors, mechanical damping and electrical damping. No matter what kind of damping, it is to apply braking force to the movement of the cone to prevent its original movement. In this regard, we can use the car's suspension system as an analogy: traditional American cars often adjust the suspension to be very soft for comfort. To do this, simply use low-coefficient springs and Flexible shock absorbers (shock absorbers), this combination has a very low system tuning frequency (Note 3), so you can absorb most of the pits and bumps without any traces because of these external forces都是短暂时间内的脉冲响应，转换成频率领域就是中高频，所以能够有效的被吸收而不会激起系统的共振。但遇上波长很长（也就是频率很低）的脉冲，如桥面的起伏，就常会产生二到三周期的缓慢上下晃动，这便是整套系统的共振频率被外力激发而引起的共振。同样的，在喇叭单元上，要调低系统的共振频率也可以从悬挂的顺服性上面着手。将阻尼减弱，共振频率就降低了，直接了当。

但采用此法还是会面临一些问题，我们再细看下去： 机械性阻尼方面：指的就是音盆悬边及音盆和音圈筒相接处附近黏附的波状折纹悬挂所施予音盆之制动力。这套悬挂系统除了对音盆整体的运动产生阻尼之外，另外对音盆的盆分裂共振也有抑制的作用，尤其是外围悬边。所以一个单元若换用不同的悬边，将会大幅改变其音色，因为整体的共振控制及音染的模式和程度都已不同。若为了调低系统共振频率而贸然大幅减低悬挂阻尼将会带来音染程度的增加，尤其是中音域部分。所以，调整机械阻尼须小心从事，适可而止。 电气性阻尼方面：指的其实是单元磁力对音圈的控制力。当然，单元的磁力愈大，驱动音圈的动力就愈大，同时制动力也愈大。强大的驱动力是我们所希望的，因为可以带来高效率低失真，但是如影相随的高阻尼却使得系统共振频率无法降低；这里，进退两难的态势便明明白白摆在眼前，因此我们只能取一个妥协。若再加入高端延伸的问题，这个妥协就更是不易取舍了。

高端延伸问题影响一个单元高端工作状况的主要因素和低端一样是“电气因素”和“机械因素”，只是情形不尽相同。所谓电气因素指的就是音圈所造成之电感性负载，我在先前的文章就曾提过这件事，现在让我们来看得更深入些。 顾名思义，音圈就是一个电感线圈，若音圈单独存在，便是一个空心电感，此时，这个电感的电感量不高，而且很线性。不幸的是，音圈要在磁路结构内才能工作。没有例外的，音圈内就是中心磁极，这种结构就成了名符其实的铁心电感，这么一来电感量大幅提高，而且根据电感先天的低通特性，高频信号在这里就直接被大量衰减。更糟的是，随着音乐信号起舞的音圈与中心磁极的相对位置又不断改变，电感值和磁隙中的磁场便起了复杂的互动，严重的互相调变着，这种情况在大音量、宽频域发声时尤甚。此时，各种失真就直线上升，听感上便是模糊、粗糙、声音的纹理细节被抹平、立体音像溃散、音场扁平压缩。解决的方法是，在磁极上镀铜或插入铜片环，以使磁场短路，大幅减少相互调变，音圈的电感值也可大大的减低。此举可同时增加高频的延伸和降低失真。 另外，所谓机械性因素就可以从物理学的基本原理来讨论：施力的大小等于质量和加速度的乘积(F=ma)，其中加速度也就是速率的改变率。想象一下，一片振膜要在往前推的过程中减速，最后在冲程的终点停住，然后再加速往另一个方向后退，若是在20KHz，这全部的过程要在四万分之一秒完成！有兴趣的读者不妨自设一个冲程值，然后算算这样一个半周期简谐运动的顶点加速度值有多大。我想，不用去算就可以想见在四万分之一秒当中作180度方向改变的运动是有很大的加速度值！

所以，要做到这等高频响应，就要使振膜达到这么高的加速度。从上述简单的定律，途径只有二：减轻振膜质量和加大驱动力。但这么一来，许多的两难和矛盾也随之而来。难解的两难和矛盾振膜质量先前提到，要降低系统共振频率最简单的就是增加振膜质量；当然，这是很容易做到的。但是，为了高频响应和发声效率，这样又算不上是好方法。那么，我们不要硬碰硬，让单体在低频时“看到”较重的音盆，而在高频时就只看到较轻的音盆。听起来有点诡异？ 这是全音域单体的设计中非常巧妙的一招，也就是“机械性”分频。实际操作时的情况是，低音时，整个音盆一起动作，渐往高频时，利用盆分裂特性使得音盆较重且声阻较大的外围“来不及”跟着一起动。此时，真正随着音圈动的只剩下较内圈部分，相对上这个“局部”区域的音盆比起整个面积当然就轻得多了。所以，这样一来，随着频率的不同，音盆“实际有效”的运动质量就不同。如此，高频到低频的响应就可以同时达到。 刚刚提到的“盆分裂”，说来轻描淡写，但稍微想想就可以体会到其中的重重困难。如何在某个频率以上使得一部分的振膜“来不及”跟着音圈动就很难控制了，再者，要让这些部分“既然跟不上就干脆别动”也不简单，因为，最怕的是跟不上音圈的驱动而自己乱动，徒然增加音染。而且要注意的是，单体实际在播放音乐时其中包含的频率很广，且时时刻刻在变。所以一旦这样的盆分裂不在控制之内就可以想见其失真之恐怖！

驱动力先前有提到，若要让高频延伸，势必要有很强的驱动力来使音盆的加速度达到高频的需要。而驱动力的来源有二：音圈及磁力系统。把音圈的圈数绕多些就能产生较大的磁力，以便和磁力系统相互作用而产生较大的驱动力，但圈数多就意味着电感量的提高和质量的增加，这二者又都不利于高频，所以此路不通，音圈的设计仍要取一妥协。在此，“小而美”显然比“大而不当”要好得多。 再来，我们只好增加磁力了。虽然先前提过，强大的磁路系统会造成很强的阻尼而使得自由共振频率不易降低，但是为了要达到高频发声所需的振膜加速度，磁力的强度还是要比一般单体强上许多，才有办法将“不轻”的音盆（注4）推出那种级数的加速度值，否则就和一般的中音单体没多大分别了。至于阻尼过度的问题，只好由放松机械性阻尼来做补偿了。

系统整合问题不就只有一只单体，何来的“系统”整合？这里的系统整合指二方面：一是音域平衡的微调，二是装箱调谐的设计。此二者常相互牵动彼此。 理论上，一个理想的全音域单体应该是在装箱后或固定在适当的障板上就可以直接连上后级，没有任何阻隔的发出天籁。但想想先前提过的种种进退两难的窘境，在设计者绞尽脑汁、呕心沥血，好不容易做出一只能够全音域发声的单体后，你还希望它能“全面性”毫无妥协的发出你想要的一切？请记住，在各种的进退两难中，绝大多数的出路便是“妥协”。 若你对Stereophile熟悉的话，应该对他们刊出的各种器材测试图谱有些印象。一般来说，扩大机的频率响应图在20Hz─20KHz之间几乎就像是尺画的一样平直，若是管机，顶多在频域二端有些微的滚降；而喇叭的频率响应图谱就崎岖得多，用坏掉的锯子来画还比它规则些。若再看衰减瀑布图和离轴响应，那就更糟糕了，各种奇形怪状的高山深谷遍布全频段。

为什么喇叭的频率响应没办法作到像扩大机一样的平直？因为喇叭是机械性动作的组件，一动起来各个部分的能量传递、释放和储存会非常复杂，且相互关联。如此，免不了会存在许多的能量堆积或相互抵消的状况─ 能量堆积处形成共振峰；相互抵消处形成凹陷，这么一来崎岖的频率响应就不足为奇了。较佳的情况是崎岖的形态较缓和且均匀，如此可避免集中在一个特定的范围而形成明显的音染。若起伏很大或集中在一处就不妙了，强烈的音染不但扭曲了音域平衡，其共振峰处的能量不但较强，而且久久不散（常可在瀑布图上看出），所以会严重掩盖其本身和临近频段的解析力和微动态表现，就算用高Q值陷波器来加以衰减还是无法解决不干净的残余共振。 另外，单体的阻尼状况也常会表现在频率响应曲线的走势上。若高端上扬，则是中低音域的阻尼相对上有些过度，听感上便是紧瘦结实，稍偏明亮；若是反过来低端上扬，则是中低音域的阻尼相对上有些不足，听感上就较为肥胖宽松而昏暗。 说了这么多喇叭单体的“黑暗面”，不外是要提醒大家，就算历年来各“传奇”的全音域单体各自在不同的领域理皆有其“超级制作”之处，但在无可避免的众多妥协之下，免不了有其取舍，而很难做得面面具到。就连乐器的制作都要投注极大的心力，才能获得音色的完美和全音域响度的平均，更何况是喇叭单体这个“二线”的模仿者。 所以，一个全音域单体，虽可以做到全音域发声，但不见得一定平直。

常见的问题有：中音部分（有些是中高，有些是中低）有宽而缓的凸出，造成听感上某种程度的音染；还有部分是高端有缓和的滚降，造成听感上较为昏暗；当然还有过度阻尼造成的低端滚降，听感上自然是又瘦又紧，低音没有量感。 若是频率响应有些微的凸出，而这个音染又令人无法忍受，只好用一个陷波器来将这个凸出压平。若症状不严重，这个方式多半能有令人满意的结果。别瞧不起这样的组合，虽然这样一来后级到单体之间有了一些“阻碍”，但这算只是频率响应的修整，比起多路分音的喇叭中频率响应复杂的交叠和扭曲的相位，这还是单纯多多。而且，这类陷波器线路其实在许多喇叭的分音器上都可以找到，所以也不算什么见不得人的东西。 若是高端滚降，则多半是因为相对上磁力系统不够力所致，或者是音盆太大，用上“机械分频”的技俩还是拖累太重，如早年的12吋甚至15吋的全音域单体或多或少有这样的问题。此时，除了加个高音单体，别无他法。你会说，唉，这算是哪门子的全音域！别急着下定论，若妥善处理，将高音单体的响应从16─18KHz处（或甚至更高），以每八度-6dB的斜率缓缓切入，还是能够得到很好的结果，因为分频衔接处已避开了人耳敏感的音域，且一阶分音能保持相位一致，所以还是保有全音域的“大部分”好处。（若你手上刚好有Altec 412C，又嫌它们没高音，请赶紧通知我，我很有兴趣购买。等我弄出好声，你就别想再买回去）

最后一种情况就是低音部分的滚降，这类全音域单体具有较强的阻尼，低音的听感常紧缩而短促，好处是细节清晰。此时若能使用适当的装箱调谐或甚至用号角负载来提升低音部分的声阻而提高效率，整体响应便很理想。若制作得当，这样的组合能提供最佳的全音域发声表现。 既然提到了装箱调谐，我们就顺势谈下去。一般市售的喇叭，90％以上都是密闭音箱或开口调谐（一般俗称『低音反射式』）。只要是箱型喇叭便大致脱不了这二种设计及其衍生物，只有少数例外。对于全音域单体来说，应该要使其低音域发声时的振幅愈小愈好。因为振幅愈大，不仅低音本身的失真大增，同时中高音更大受影响。想象一下大振幅全音域发声时会是怎样的情形：中高音的小幅度快速运动“骑”在大幅度慢速的低音运动上，中高音的振动时而向你靠近；时而离你远去，可想而知会带来很高的互调失真和都卜勒失真。虽说任何单体都会面临类似的问题，但全音域单体的工作频域远大于其它单体，所以这种情况会更明显而应极力避免或减少。 在刚刚提到的二种主流装箱方式中，开口调谐应是较适合全音域单体的，因为这种方式可在系统共振频率附近（一般是30─50Hz，视设计情况而异）大幅减少音盆的冲程。如此便一举三得：失真降低、承受功率较高、发声效率也高。因为这个缘故，绝大部分的全音域单体都可以用这种装箱方式得到大致上不差的效果。 另外，有些纯粹主义者认为，这么好的单体装在箱子里会被箱体共振所玷污，所以不用箱子，直接装在开放式障板上。某些本身低音部分就足够的单体便适于如此使用，可以获得最无染纯净的声音，如WE/Altec 755C。据称，其中音瞬时快若闪电，比之静电喇叭毫不逊色，又有更佳的动态表现。但这个方式有一些缺点，首先当然是占地太大，因为系统的低音延伸取决于障板面积，为取得适当的低频响应，小则需要1公尺见方，大则没有上限，要将墙壁挖二个洞来装也可；再来是效率和承受功率都会较低，低频响应也会较弱；最后是双面发声会使得空间因素更形复杂难解，而二片大门板矗立眼前实在也不容易被大多数人接受。

最后，便是最复杂的号角负载方式了。关于号角的种种，我们择期再详谈，现在只能大略的介绍一下。简单的说，号角就是一个呈喇叭状展开的管道，宽的这边称为“号角开口”，窄的那边称为“喉部”。号角的形状会造成喉部的声阻大于开口，使得位在喉部附近的单体振膜和空气分子间有很大的压力，也就是说这之间的能量可以的耦合得很好，因此发声效率很高。 使用背载折叠号角的型式，在适当的制作下，中低音到低音部分的效率会有效的提升，刚好和之前提到的阻尼过度的单体能有几近完美的配合。单元简介历年来各厂家生产的全音域单元说来也不算少，我当然无法一一列举，以下便就我所知，举一些较著名的例子供读者参考，其中有些尚有新品产制，而其它便只能在二手古董市场才能找到。 Jordan Watts 非常特殊的设计，采用铝质音盆，在悬挂阻尼部分扬弃了一般传统的波状折纹阻尼，而使用特殊的线状悬挂，有很高的顺服性。我和Jordon Watts的结缘是由“花瓶”开始的，起初是因为商家清仓拍卖，而我又觉得这对“花瓶”的造型古朴可爱、颇有意思，所以就买了。原本还对它的声音没什么期待，没想到一听之下喜出望外，6吋铝盆发出的声音还算相当的“全音域”，在我10坪左右的房间里，低音有模有样，以中等音量听一些小编制的音乐，那种纯净和韵味真是令人感动。缺点是中低音有些音染，有一段听起来肥肥的，但我每一次听超过半小时后便不再查觉这个问题，不知是单元的Warm-Up，还是我的耳朵习惯了。另外就是效率过低，音量稍大时就明显影响整体的清晰度。 同厂另有一款2吋直径的型号，一样是铝盆，除低频受限和效率偏低外，其余的表现可称得上经典，它在脉冲响应测试上尤其结出，主观聆听也非常之清新可人。

Diatone P-610系列具有一段历史且广受好评的单元。采用6.5吋纸盆和Alnico磁铁，效率90dB/W，低频可达50Hz，对全音域单元而言已属佳作。其音盆表面的数道凸起的压纹就是用以控制盆分裂状态之用，正如先前提到的，可达到某种程度的机械分频效果。原来的P-610做到第四版，在1993年便已停产，后来少量推出纪念版，市面上的能见度极低。可惜我还无缘一听这个喇叭，但据可靠的消息来源，这个单元也许称得上是各项表现最“全面”的全音域单元，也就是说“妥协”得最巧妙，声音平顺甜美，超卓的结像力，微动态精巧清晰，且使用最容易，用一般的开口调谐音箱便可顺利工作。据称，与单端直热式三极管机是绝配，尤其是2A3，你若有兴趣，不妨一试。 “WE/Altec 755A/C传奇性”的8吋纸盆全音域单元，效率很高，755A的标称规格为70Hz─13KHz，承受功率8瓦；755C则为40Hz─15KHz/15瓦。从音盆的正面可以看到一圈凸起的压纹，形状有如窄窄的悬边，这也是作为盆分裂控制用，达到机械分频的效果。这个单元的历史久远，WE制的几已杳无踪影，Altec制品我也只看过一只，而且还不太完整。从单元的外观及结构看来，似乎看不出有什么特出之处，甚至于框架和磁铁的构成还可能会有一些背波反射的问题。但一些国外的DIY玩家非常推崇这个单元，还将它的纯净无染与Quad静电喇叭相比，且具备更佳的动态对比。一位小提琴家兼业余音响DIY爱好者，Joseph Esmilla就曾“在Sound PracTIces”杂志发表过他使用Altec 755A/C的心得，用极简单的开放式障板，搭配2A3或300B单端扩大机，能展现出无可挑剔的音乐性。 Goodmans Axiom 80另一个“传奇”！我常到好友李建德处走动，基本上，他那里就几乎就是“铭器博物馆”，经常有些又旧又怪又可爱的老东西出没，久而久之，我也见怪不怪，习惯了。大约一年多前，我无意中瞥见一个喇叭单元高高的放在架上，只露出半截墨绿色的屁股（就是磁铁和框架啦），有种似曾相识之感，可是又不是真的见过，比较像是记忆中某张图片的印象之类的。于是我问李兄那是啥，他头也没抬，轻描淡写的随着口中的一缕香烟吐出一句：“就Goodmans啊”。 GOODMANS！ ! !我一听，第一时间就冲上前去，不顾满地的WE后级，飞身扑上，一把抓住那截墨绿色的屁股，然后整个捧下来抱在怀里，虔诚而小心翼翼的细细端详，愈看愈觉得此物只应天上有，“看起来就觉得很动听”

（注5），此时耳边似乎已响起它发出的天籁。正物我两忘，神游太虚之时，忽然间手上一轻，还没回过神来，只见李兄已将Axiom 80抢回去，同时塞了一支拖把在我仍然颤抖的手里，说：“把地上的口水拖一拖吧！” 原本想先筹些钱想办法把这对宝贝买过来，没想到那次的初相见竟是最后一面。因为在那之后没多久，李建德兄竟因为一些“看不爽”的原因退还给原主人。乍闻噩耗，我简直不敢相信，当场搥胸顿足、狂咆乱吼，好久说不出话来。一直到今天，想起这件往事，还忍不住要掷笔三叹。唉…… Axiom 80是英国Goodmans在五○至六○年代时期产制的一款经典全音域单元，事实上同时期Goodmans还有一些别的高效率又好声的全音域单元上市发表，但流传至后世，还是这款Axiom 80最令人称道。 Axiom 80，最特殊的地方是框架结构和悬挂的设计，这二者可说是独一无二，磁铁小巧，但应该是Alnico。可惜我找不到当初确切的设计资料，无法确定它各项细部的设计哲学，但这个单元看起来就是有一种“很对”的感觉，一种好喇叭当如是的感觉。 厂方标示规格的频率响应为20Hz─20KHz（！），承受功率则是6W。除了在自己的白日梦里，我还无缘一聆仙乐，所以也无法告诉你它听起来如何。但据国外颇为可靠的消息来源，原厂的规格标示似乎不假！但和Lowther一样，大前题是必须要有上好的背载号角音箱才能让它发挥得淋漓尽致，扩大机最好是2A3，300B的功率有点太大！ Lowther系列鼎鼎大名的Lowther，已有超过50年的历史，若是严格追溯起来，还可以说到1920年代PGAH Voigt先生开始设计的动圈喇叭单元和三○年代的双锥盆专利。提这些只是大概交代一下Lowther的源远流长，真的要细数其历史，实在也写不完。

提到Lowther，我想你第一个就会想到那很特别的白色纸盆，和很可爱又符合结构力学的框架造型，某些高级型号还有香菇头形的中心相位锥。 就外观来说，最明显的是刚刚提到的双锥盆构造，也就是藉由这个构造，使机械分频充分发挥其功能：中低频时，整个纸盆（或说二个纸盆）一起动，渐往高频时，外音盆开始发生盆分裂，而内音盆继续挺进，此时中心相位锥能让内音盆内侧的高频音波不至互相抵消，使高频能量得以有效的幅射出来，同时也可改善扩散性。香菇头形的相位锥更进一步与内音盆内侧形成狭缝负载，使高频段效率更高，以利与前方负载式号角搭配使用。最近又推出一种全新的相位锥，其造型与子弹型或香菇头都大异其趣，我看起来觉得像不明飞行物，据称能大幅改善原有的高频响应，而且能装在所有的Lowther单元上。 在纸盆的材质和制作上，Lowther一直到人工成本大涨的今天，还是坚持采用平版纸裁切黏合的手工方式来制作音盆。理由是Lowther相信使用平版纸才能得到最佳的厚度均匀性，这是直接由纸浆一体成形的纸盆无法达到的。而厚度不均匀会造成局部的共振而引发音染，过厚的部分也增加无谓的重量。另外，Lowther的纸盆还压出了特定形状的凸纹，这不外是为了增加强度和作为盆分裂的控制之用。整体看来，这组纸盆的手工制作实在是有很高的工艺水准。 在磁路结构上，大至可分三种材质：一般的铁氧陶瓷磁铁、Alnico，和新的Neodymium。虽然每一款的Lowther喇叭比起其它大多数的喇叭都是强磁力高效率，但其中当然还是有高下之分。其中，采用陶瓷磁铁者价钱最“廉宜”，所以其规格也较不耀眼；虽然如此，并不表示它的声音不好，反而是最容易入耳，不须费心校调。而Alnico系列是最贵的，也是磁力最强的，其中PM-4A的磁束密度高达2.4Tesla，是目前人类所制造的单元中最高的，其高频可达22kHz。新的Neodymium系列是试图保持Alnico的高磁力特性同时减小体绩和降低成本，但二者最高级的型号也差不了多少钱。而这新的系列在规格和音响性上表现非常好，非常的现代感，至于音色韵味和Alnico的比较，就见仁见智了。 另外很重要的一点是，Lowther需要背载号角的音箱才能发挥得最好，因为音盆的最大冲程只有1mm，所以有号角的帮助才得以发出足够的低频。但最近，Lowther American Club竟发表了几款低音反射式音箱，声称低频可平直延伸至40Hz，且中低频段的解析力更佳。这个争论也许有待我们去研究。 在听感上，几乎所有的Lowther喇叭都有共同的特色，就是绝佳的临场感、惊人的细节和即动即停的动态。在测量上，多数都有中高音段些微凸出的倾向，而高频的离轴响应很差，聆听区很小。这样深具个性的东西常引起两极化的反应：喜爱的人终身拥戴，拒绝其它任何喇叭；不喜爱的人则认为它连Hi-Fi的边都构不着，不知道有什么好迷的。 在欧洲，有许多国家都有Lowther Club，会员们当然都是Lowther的忠实拥护者。后来，这股风潮也漫延到美国。当然，认真到近乎神经质的日本人当然早就发现了这种很合他们味口的东西。现在，你也知道了Lowther这个很特别，而且还蛮容易买到的好东西，要不要加入俱乐部，就看你自己了。

结语全音域喇叭在适当的使用下能给你绝佳的音乐性满足感，有全频段相位一致的优势，也没有讨厌的分音器来啃蚀宝贵的音乐讯号，精妙的微动态和音乐表情，更精湛的音场表现和结像力，这些都是多音路喇叭所不能给你的。但是也请务必了解，天下没有完美的事物，若你习惯听120分贝播放的重金属摇滚，或经常率领你的喇叭们在AV的枪林弹雨中冲锋陷阵，甚至三步五时呼朋引伴引吭高歌。那么，我要劝你不要把全音域喇叭用在这些地方，因为这样你和喇叭都会很痛苦。 小心珍惜的使用这些宝贝，用谦逊的音量播放简单的音乐，你才会得到心灵上最大的震撼。此时，音乐的本身就彻底将你感动，音量大小已不重要。
注1：当然，实际应用时会因为装箱调谐方式而有很大的变化，所以在这里便略过这项变量很多的因素而只看单元本身的表现。
注2：译自AcousTIc Impedance，其定义为空气粒子的压力与速度的比值。注3：在其它的地方，如LP唱盘或CD唱盘的机械悬挂，通常一样需要很低的系统调谐（低于1Hz），设计时要考虑的因素其实和汽车悬吊系统也有共通之处。
注4：就算是用上了“机械性”分频的妙招，最终高频段工作时的等效质量还是比起一般的1吋直径高音单元要重得多了。
注5：“看起来很好听”正是李建德兄的名言之一，因这个单元的因缘，特此引用。