【 Weak current College 】 quality characteristics of loudspeaker unit

Speaker unit determines the ultimate potential of the speakers, but in the HIFI system voice played the leading role in the performance. Under the present technical conditions still making a perfect unit, the target is still decades later, because it requires a cell has the air of the same density, fully in all frequencies evenly, without any kind of distortion.
We have before us is a long road, but should also be full of confidence. At this moment in material science is undergoing significant progress over the past 10 years has been a lot of results. I'm sure will be a couple of years have made new breakthroughs.
We benefit from computer simulation of the mechanical behavior of significant progress, as well as aerospace, automotive and sports-and leisure industry to adopt the light quality of high-performance materials instead of expensive and heavy burden of traditional materials by a lot of research. We now have a KEVLAR, carbon fiber composites and aluminum diaphragm, the not-too-distant future, also with synthetic diamond, ultra-low density Silicon single crystal glass, the type of metal and carbon single crystal as well as new composite materials.
Why speaker units have their own different voices?
Designers face the biggest challenge is how to ensure the uniformity of the movement, and eliminate resonance in high frequency. This is the variety of speaker systems had to make compromises (non-quality speaker excluded). Other problems have cavity resonance and nonlinear magnetic field.
Uniform motion
Rigidity means from the voice coil acceleration be accurately converted into the cone or dome the acceleration of the entire surface; this makes it possible to obtain flat frequency response, rapid Pulse rise, low intermodulation distortion and sense of sound.
Enthusiasts usually take this type of voice described as "speed", which is the basis of objective measurement-based engineers is stunning, "How may in bass unit for fast? divider limits the pulse rise time, equivalent to treble unit 1/5 or 1/10, such as diplomats often say one sentence, a phrase" full and frank exchange of views ", or mutual exchange of misunderstanding.
You can say both sides are right or wrong. They actually talk about different contents. Enthusiasts hear is even cone movement; this phenomenon in the testing problems: no intermodulation distortion, frequency response is flat, clean and impulse response.
Very good, so why not put the cone or dome stiffness as much as possible to make some? like bronze metal. Its strength is good, and almost any shape can be processed into. The clock is made of bronze. But the problem is the echo of the resonance, which up to tens of thousands of weeks.
Answer there are two points: firstly, metal stiffness; second, the clock is the only way to release the mechanical energy is through the air, because of the density of air and bronze, lead coupled vastly, air load damping the inevitable micro, it takes a long time. We look forward to a speaker unit of another performance:
Since the damping
We also hope that the voice coil in a timely manner to stop diaphragm before they issue their own tones. Unfortunately, most rigid materials (e.g. metals) almost no self damping, causing its long vibrations. Control of this approach is the heavy rubber-ring extend into the cone, and pay great attention to centering force tablets and fold the ring material damping behavior.
But now, even the best of KEVLAR, carbon-fiber or aluminum diaphragm or at least in the upper section of the workspace, a high Q value, you must use the divider or filter to be inserted. Worse, the peak General falls between the 3 ~ 5kHz, this is precisely the ear on the bass frequencies of the most sensitive.
Since the damping can eliminate dyeing and given a relaxed, natural and less fatigue characteristics of sound. Many enthusiasts and even some commentator for unit materials resonance indicates, special sound,but due to the sensitivity of the amplifier or room.
Some magazine recommended 2-way loudspeaker with 7 "KEVLAR and metal ball treble. From a technical standpoint, the speakers in their work area uniform movement, but in fact to eliminate KEVLAR3 ~ 5kHz split vibration regional energy, for the purposes of the divider is to bite.
For this type 2-way speaker reviews to a substantial part, through trial and error to select a position to fully play the speaker quality amplifier. In fact, sound commentator was forced to choose a unit just KEVLAR vibration frequency occurs segmentation paragraph on extremely low distortion amplifier. Because most of the fever and commentator for the direct sound loudspeaker unit is not familiar, they were not able to evaluate how many sound "KEVLAR" or "aluminum film sound" are retained in the final design of the system.
There is also a problem plaguing all 2 road, KEVLAR, metal and carbon fiber speakers. In the current level of technology, 6.5 "or 7" unit had to play to the edge of their range of work, so that the distortion is not too big a frequency and treble unit.
If you lower the crossover point, treble unit intermodulation distortion will proliferate, cause in a medium and large volume of listening time-frequency deterioration. If you upgrade crossover points, and KEVLAR split vibration, resulting in the sound at lower volume, shouting impulsive pressure when you full hair out.
This makes designers face difficult choices: either a treble in the whole area of rough sound; or typical KEVLAR front flush, and has the potential to bring the wild loudspeaker system. Now the best way is to use 4-order (24dB/Oct) divider to correct KEVLAR resonance.
By the way, I like KEVLAR and carbon fiber units. But they are very hard to deal with, you must use a means of acoustic and electrical control their strong resonance.
As mentioned earlier, there are some rigid Cone, but damped very difficult. Another way is to use high lossmaterial, traditionally is plastic-coated paper Cone, but in modern speakers they gradually superseded by polypropylene. This type of cone can rely on its damping, pulse from the voice coil in diaphragm surface diffusion is gradually lost energy. ThusCentering force tablets and folded loop requirements are not very stringent.
This type of material of the test in the frequency response is flat, allowing the use of simple divider 6dB/Oct. I am most interested in polypropylene unit, which in middle and low volume of sound some fuzzy. Although not using B & K intermodulation distortion Analyzer, but I guess they are soft and have considerable intermodulation distortion. In addition, to create a perfect linear mechanical ability of material attenuation is extremely difficult. In fact in the decay process always inevitably accompanied distortion.
I think all similar phenomena also occur in the soft ball Treble Cone cell; in fact the entire band split vibration, the instrument measuring out because there was a strong damping obscure, but are able to distinguish the human ear. In order to overcome this kind of subjective effects, the best unit (Dynaudio, Scan-Speak, Vifa) are made of composite materials, plastics joins silica, mica, or metal powders, which can significantly increase the stiffness and keep the sound characteristics of polypropylene compliant.
Cavity resonance
Bass unit of dust cap or treble unit ball while on the surface without any harm, but dust cap and magnet pole block the formation of space between a small resonant cavity. The typical example is the development of the early 1970s KEFB110Bextrene bass unit (for BBCLS3/5a).
This unit may be the earliest a commercialization of high-quality audio units, but it also has a lot of problems such as inefficient and inadequate power endurance to 1.5kHz-centred width a octaves of response peaks (the divider correction) to 4.5kHz-3 high Q value peak (BBC design of 3-order divider can only be slightly attenuation). Audio commentators put these peak incorrectly attributed to treble unit, which has strong links to sex, it is dust-proof Cap resonance.
Some of the 1970s pop soprano voice modules, including Audax and Peerless1 "soft ball, also at 9 ~ 16kHz have similar formant, ball and a block between filling felt washer can partially damping off. Because the internal friction of the soft ball than the dust cap strong B110 much resonance is much wider, and the range is also only 1-3dB, but still exist, sensitive listening will detect that the fatigue properties.
It is not difficult to imagine that the articles in the speakers of phenol used in plastic, glass and cardboard ball is very terrible. (Hey, does anyone remember the Rectilinear BICVenturis? Cerwin-Vega?? JBLL100? when I was young, I had been sold these terrible product, waiting for customers to use their audition Spink Floyd's "dark side" of the moon. ）
Return now, high-quality in the bass and treble unit with two ways to avoid this problem: Nordic manufacturers Dynaudio, Scan-Speak Vifa and Seas introduction, mouth-pole block components; France manufacturers Audax and Focal use bullets head of block extensions, completely replaced the dust cap.
Use open-a block in the transmission line in the back of the damping ball-the most famous products include: DynaudioEsotecD-260, EsotecT-330D, Scan-SpeakD2905/9000 treble unit. They SonusFaber (SE PA) Extrema and ProAc (nobles) Response3 speaker applications in support of this technology is very successful.
On the contrary, the T120K FocalT120 and uncontrolled damping cavity using rigid fibreglass or KEVLAR inner hollow ball, its scope of work of the high-frequency end renders a range of high Q value, this is the resonance Chamber and rigid dome first split vibration generated by the mutual coupling. I started with these cells are universal praise confused, I do not like their sound, the test data is not special.
However, from various new Focal titanium ball T120Ti and titanium ball T120Ti-O2 are excellent, recently I hear the unit when you feel good speakers.
Nonlinear magnetic field
Most enthusiasts know speaker unit is inductive load, while the voice coil is wrapped around the magnetic pole block. But not many people know so many problems arising.
If the inductance values remain constant, like air core inductor, there would be no problem. Just use the R-C network tuning frequency divider. Unfortunately, it is an iron core inductor inductance value, but also with the voice coil position changes.
Change the value of inductance causing serious consequences because the inductance value is lowered down top frequency unit and sound delay. Change the inductance value, frequency drop-down and delay also will change. Whenever the unit reached considerable voice coil linear stroke ratio can occur. Outstanding 8 cell VifaP21W0-12-08, for example, linear stroke only 8mm (+-4mm). Most of the 8 "unit of linear stroke usually 6mm, baritone unit 1 ~ 3mm.
Play some low frequency would have the role of inductance modulation appeared, that is, the entire spectrum of mutual harmony on FM distortion. This 2-channel and audio frequency low 3-way systems is a big problem. In other words whenever you see the unit movement, already appeared a large number of mutual harmonic distortion FM. The sound of auditory sense? you will find the low-frequency resolution loss, but this may be the amplifier problems covered (for example output transformer less saturated, power supply).
Solutions? Scan-Speak SD system and system of DTL Dynaudio with bronze package packing of a piece of the voice coil induced eddy current of short circuit. Careful analysis of the voice coil inductance can discover the secret.
As the world's best 8 "unitOne of the Scan-Speak21W/8554, the inductance value is 0.1mH, far below the VifaP21W0-20-08 0.9mH. Both units are excellent, but if you want to also issued medium-frequency and low frequency, Scan-Speak can certainly give more transparent sound.
Inductance value there is a caveat, unit high-end frequency falls drop by self-inductance of the coil and machinery fell down the common decision. If you use the voice coil inductance and DC resistance to calculate the frequency drop down, its value in certain cells often than measured acoustic fell down. While other multiple units is calculated value is less than the measured value. Because of the voice coil of perceived cloak of mechanical systems with peak. This is not a good sign, mechanical system or electrical system for any change will strongly affect the frequency response and transient response.
Incidentally, the same problem also appears in old-fashioned perturbed magnetic changtou. Not surprisingly, this class changtou in transparency than advanced dynamic changtou much less.
The following will explain how to find enthusiasts like speakers, draw their own conclusions, and speculated that manufacturers, commentators and your friends ' audio preferences.
Unit type
Familiar with and to master the basic properties for cells in listening and contrast is very helpful, you can determine whether it falls within the same unit of a good thing. Through careful listening and of all relevant parameters, you can find designers in resolving issues doing what is good or not.
1 cone unit
First appeared in the late 1920s, and piccolo of the patent application document. The quality of the paper can have a world of difference, the worst you can find on the radio in cheap, excellent as Scan-Speak5 "baritone for Thiel's speaker, SEAS6.5" bass for WilsonWATT. This ancient material is actually a composite structure, when using a suitable plastic coating performance when significant changes occur (coating choice is unit manufacturers of commercial secret). Because of the characteristics with the humidity of paper and time change significantly, the coating is indispensable, as the stability of the material, but also improve self damping.
Advantages:
Good or even excellent self damping, excellent analytical ability and details, flat response, gradually began to split vibration. Easier to cope with the low order linear-phase frequency divider. Paper diaphragm sound than its measurement data predicts better.
Disadvantages:

Stiffness than KEVLAR, carbon fiber and metal films, so the lack of static type details. Sound pressure level as other materials.
Paper synthesis of consistency no matter good pairing is not very accurate, this may affect the knot like force, of course, also depend on the production of precision and quality. Even after the coating process, over time, the performance may still be changed.
High-quality products:

Scan-Speak86405 "cone/dome baritone, linear response up to 13kHz, distortion is very small, impulse response, rich in detail.
SEAS6.5 "bass (for Wilson's WATT, but may have been modified).
AudaxPR170M06.5 "high efficiency (100dB/m) the baritone.
It is said that Kurt Mueller production of paper and fold the ring of the best quality, is Scan-Speak, SEAS, such as manufacturers adopt. Vifa
2BEXTENE Cone

This is a synthesis of plastic wood pulp, always with a coating of damping material to control its 15kHz first resonance. It was in 1967 by the BBC, as a better consistency and predictability of material instead of paper, to adapt the monitoring purposes. In the early 1970s, when the widespread use of typical fever speakers are often a 8 "KEF or Audax bass mix of BEXTENE Audax1" soft ball treble.
From the BBC's design is always using proportional to BEXTENE element in maintaining a flat in the band, the most famous unit is probably for the LS3/5a monitor box KEFB110.
Now BEXTENE has been developed by the BBC first replaced the polypropylene, polypropylene unit more flat frequency response, eliminating the need for coating, but also because of the quality and efficiency increases 3 ~ 4dB. BEXTENE has exited the stage of history.
Advantages:

Good knot like, resolution number cone libido.
Disadvantages: inefficient (85dB/m), strong staining, without too much sudden split vibration sound pressure.
High-quality products:

.
3 soft ball top treble
In the early 1970s Peerless1 "soft ball gradually began to appear after. Subsequently, Audax1 "treble in the 1970s and early 1980s was in Britain and many other designers.
When in the mid-1980s ball titanium, aluminum and fiberglass concave Focal Dome, the design of the doghouse, Audax soft ball unit being squeezed out fever-level market.
Over the past few years to Dynaudio and Scan-Speak represented soft ball treble resurgence, they again adopts the new ball shape, new coating materials and new design, its performance comparable to any metal ball. Sound analytical and detail and the best metal ball counterparts but no metal ball that typical 22kHz ~ 27kHz resonance.
Advantages:

Inherent self damping and extremely flat response, excellent impulse response. Natural, open, no fatigue, listen to digital voice recording this is undoubtedly the most valuable quality.
Disadvantages:

Old-fashioned soft ball sound dull. Power tolerance is rather limited, 18dB/Oct divider to reduce intermodulation distortion. Compared with the metal ball, high frequency divergence even worse.
In addition to the divergentIn this context, the latest design has no other such defects.
High-quality products:

DynaudioEsotecD-260，EsotecT-330D，Scan-SpeakD2905/9000。
4 soft ball baritone unit

Audition too AR-3, ARLST, ADS, Audax2 ", DynaudioD-52 soft ball baritone, found the speaker system is a mess. Measuring time is very flat, but the sounds sound opaque, severe staining, tiring.
One is the soft ball baritone unit linear displacement is limited (generally 1 ~ 2mm) bandwidth is limited, and neither 500Hz frequency is very good, only 800 ~ 3200Hz range between work best.
>The second problem is that they easily produce lateral offset, because no centering force tablets to help break loop so that it remains linear movement before and after.
The third problem is the silk film ball of stiffness is insufficient to complete the band's strong power conversion tasks.
The new generation of cone-ball, for example 5 "Scan-Speak13M/8636, 13M/8640, Dynaudio15W-75 is completely different. These three units are actually cone of high precision, rather misses the ball. They are the only soft ball is similar to the place has a huge dust cap, in the high-frequency can also be played ball.
They obviously has greater stroke, lower distortion, much wider frequency response. This type of unit to obtain truthful and transparent sound. Because they are using KEVLAR, paper and polypropylene, the following details.
Another special case is the professional-grade ATC3 "ball (with short number tube). It uses a double-centering-Gage, significantly reducing the intermodulation distortion. Its performance is best, but very expensive (about 300 dollars only), and the need to manually select to enable the resonant frequency matches left and right channels.
Advantages;

Lol Maybe metal ball baritone has potential, but they are on the divider is very demanding. Note: ATC unit and cone-ball.

Disadvantages:

Distorted sound great, tiring, crossover point high frequency bands and power endurance are limited. Only laser holographic measurement to discover their individually.
High-quality products:

ATC3 "professional series, and is distinct from the General soft ball, but the price is about 4 times more expensive. Some people think the Dynaudio D54 is the best baritone.

5 polypropylene unit
1976 BBC developed this material used as a substitute for BEXTRENE. Because it has a very strong self damping, design appropriate polypropylene unit shall not be liable for any balance can be obtained at the workspace level of response. In addition, its efficiency generally reaches 88 ~ 91dB, is also a great improvement.

PP has become a world-ready materials, because when assembling a speaker on the manual processing of requirements for minimum--the only difficulty is to find a suitable binders, the problem is in the early 1980s.
Now, from the cheap phonograph to first-class ProAcResponse3 and HalesSystem2 Signature Edition of various speakers are using polypropylene unit. This type of unit of the final quality depends primarily on the cone shape and add in polypropylene formulations.
Advantages:

If properly designed, you can get a flat response, very low acoustic colouring, good pulse response, can be very simple, efficient, split vibration occurs slowly. High-quality products can be done and the best paper trough is transparency.
Disadvantages:

Has not yet reached by rigid cone cells and electrostatic unit of transparency standards. Due to the resolution of differences, many pp bass doesn't work with popular metal ball treble well matched. Not suitable for 10-inch or larger bass unit, this should be more carbon fiber.
High-quality products:

Scan-Speak18W/85437 "in bass (for ProAcResponse3), may be the world best polypropylene unit.
Dynaudio17W-75EXT7 "in bass (for HalesSystem2 Signature Edition).
VifaP13WH-00-085.5 "unit is another winner, particularly suitable for Alto or mini monitor box. It is extremely flat frequency and smooth 2-order drop-down is unique.
6 metal balls top treble
In the mid-1980s Germany in metallurgical technical progress (ELAC and MB company) makes thin titanium, aluminium ball was born, now Germany, Norway and France have more manufacturers can supply such a unit. Their sound can be very transparent, if properly its features and design of electrostatic speakers.
Its disadvantage lies in the lack of self damping, aluminium membrane in ultrasonic frequency band performance modestly better than titanium coating. At this stage, all metal ball treble unit has significant peak, the ultrasonic wave period ranges from 3dB (excellent) to 12dB (General).
However these peak impact does not seem as "resourceful" SONY/PHILIPS CD red book already standards ensures that the CD does not contain any more than music information 20kHz. Maybe when the idea of Super HI-FI CD for commercialization, we can receive the frequency cap at the very least, to the analytic power of real 32kHz, 20 ~ 24-bit recording.
Advantages:

Uniform design of piston movement, the right to produce extremely high resolution power of transparent sound. Divergence is very good, because metal ball RADIUS than the soft ball.
Disadvantages:

May be due to the high frequency of peak and audible band voice of interactive modulation and generate the "metal". Some early products limited power endurance. When strong overload, throughout the band appears obvious split vibration distortion.
High-quality products:

VifaD25AG-35-061 "aluminium ball, uses the open-a-block, power endurance is so strong that even out of phase with, the UHF only 3dB peak. New T122Ti-O2 Focal is also very good.
7 rigid unit
Aluminium cone. The first batch used for HI-FI speakers of rigid unit is JordanWatts4 "Aluminum Cone, which is the manual production of, high efficiency, low prices, not universal, in the United States market almost do not see. Now some United Kingdom 5 "and introduced the speakers 7" aluminum pot bass unit, its sensitivity is low, but also be filtering divider.
Bubble basin. Another class to KEFB139 represented bubble bass unit, but its efficiency and power of endurance are very low, if there are serious high Q resonator. B139 peak in 1100Hz have 12dB. They are in the 70 's of the 3 rd and 4-way transmission lines are widely used in the speakers.
Carbon fiber. Next generation is Japan's development of carbon fiber, first appeared in the professional recording studio listening on cartons of 12"TAD, the efficiency is high, prices are expensive (1980, when only about 300 dollars). Now, the price of carbon fiber has been reduced and Vifa and Audax has very good this type of product. Of course, Japan's output.
Carbon fiber units have real piston movement, low-frequency and low frequency response is great, but in the top division of the vibration frequency is very annoying, must be determined by the complex modulus will be amended.
Although I don't like require sophisticated filter unit, but have to admit, Vifa8 "and 10" carbon fiber unit is the only makes me really feel the low frequency of direct radiator.
KEVLAR。 KEVLAR units in the mid-1980s appear in France and Germany Eton Focal's product line, the cell because the Eton two layer KEVLAR joined the high loss between honeycomb structure with excellent damping characteristic. Eton and updated Scan-SpeakKEVLAR units sharing the world's most outstanding high technology speaker units.
In the type of unit you can find on Scan-SpeakKEVLAR a unique and what we desire, that is, smooth down. All other KEVLAR unit occurs chaos split vibration, Scan-Speak is the only get good control, so the ride and transparency for significant improvements.
Compound cone. Audax by virtue of a special kind of composites technology HD-A re-entering the High-End market. This is the acrylic gel inside by a certain percentage of mixed and granular carbon fiber and KEVLAR fibres. Factory test results show that combines good piston movement and the lowest peak, high frequency and high frequency drop down smooth.
Recently, Russian scientists achieving a low-cost diamond gas coating that can be used on a computer disk. Hope Scan-Speak and other manufacturers can quickly adopt this technology.
Advantages and disadvantages of rigid unit total
Advantages: optimal transparency, like force and acoustic field rendering, carefully designed so you can meet or even exceed the level of electrostatic speakers. High efficiency,sound pressure level, low intermodulation distortion. This type of unit is many designers as the most advanced, and with the materials technology progresses, there may be a quick progress.
Disadvantage: the old design in operating frequency than the top of the peak there is a serious, but almost all units in the high-frequency peaks above appear uncontrollable shaking district of segmentation. This results in a long time listening fatigue and sound field analysis of compression.
Because KEVLAR and carbon fiber for high frequency peaks cannot be used with a normal low-pass filter correction, using these units of speakers must be properly designed appropriate divider.
Although they can have a great sound pressure level, but often occurs in a sudden and split vibration, amplifier clipping is very similar. Some KEVLAR and carbon fiber unit takes a long time "pot machine" (100 hours), so that the cone of fiber softening; this is a drawback, the mechanical properties of materials.
High-quality products: Scan-Speak13M/86365 "baritone, 18W/85447" in bass, bass 21W/85548 ". KEVLAR unit only their performance in high-frequency peaks above falls down for good. These units are rigid cell technology's top locations.
AudaxHD-A series HM130Z05.25 "baritone, bass, HM170Z06.5" HM210Z08 "bass is good.
Germany Eton also deserves close attention, the factory has been committed to maintaining the cone of stiffness, improved self study on damping characteristics.
Evaluation unit method
I select the speaker would seem to be some of the original, I put the unit on the IEC baffle for audition. Without divider or box. Listening to pink noise to assess in a sine wave and FFT waterfall diagram measurement of peak their severity, listen to music to feel the unit of potential analysis of how many. This really need your ears trained, the listening process can make you aware of how complex prescaler needs.
Then, I will carefully analyse MLSSA computer testing system results (using the same IEC baffle), visit the following: impulse response; relative to the frequency response of group delay; cumulative spectral decay waterfall; working band of frequency response flatness.
Listen and testing can be said to be of equal importance, both can only reveal the true performance of part of the unit. Even today the best Hi-FiSystem, in 5 years may also be found serious flaws. You can find out by testing the staining of the problem, but it's exactly what today's audio equipment cannot be exposed. MLSSA system helps you address these issues. To learn more about my design concepts and related technical data.
A thoughtful designers should be as famous as good days of his work, even if they're treated from appearance simply will not see the hidden part all without stint to pour.