Collecting the information circulating in the market, we can find that in the decades since the publication of BBC LS 3 / 5A, only some articles have reported on the way to change the speaker, and the in-depth and extensive design discussion, then It is still rare. The reason for this phenomenon is nothing more than the rich musicality of these speakers when they replay the music, which makes most listeners stunned and appreciated by the insightful. Since there are many predecessors who have done extensive and in-depth research on the sound performance of the LS 3 / 5A and the way to change the machine, we may wish to look at this pair of generations from another perspective.
LS 3 / 5A that does not follow the rules
Do you know the development process of speakers? From a commercial point of view, most of the design of the speakers is the first step from the "market price", because this element will involve the necessary components such as cabinets, monomers, crossovers, etc. Parts, so this step is arguably the most important part of speaker design. After deciding the good price, it is equivalent to announcing the market positioning of this new product. The next step is the selection of the monomer, the design of the speaker and the composition of the crossover. After these heavy steps, if there are no surprises, of course, there will be products on the market.
Is LS 3 / 5A produced through this process? Sorry, maybe not! Readers who are familiar with the history of this pair of speakers must know that the original functional design of this pair of speakers was used in radio vehicles as radio monitoring. Therefore, in order to accommodate the narrow cabin space, there are many detailed designs, which is the premise Make many changes, such as: sound-absorbing felt around the tweeter to prevent excessive diffusion, mini volume, more emphasized mid-frequency, etc., and use it as mono! In other words, only one speaker at a time is used for monitoring and playback.
Because it was not originally intended for commercial use (open sales), its design steps may deviate from the design routine. Of course, some product design steps are not as I have explained, but that is only Only a few. We only explore the following points to explore why this pair of speakers is fascinating! And Rogers, Harbeth and Spendor three companies, used to compare with the LS 3 / 5A three different types of speakers between the differences.
Crossover
In addition to the monomer and cabinet, the main component of the speaker also has an important component that is often overlooked-the "crossover". The reason why it is easily overlooked is because it is usually placed inside the cabinet, unless you remove the speaker unit, otherwise it will not be seen. However, when you see the crossover, you will find it very strange, why its appearance and components, like the circuit board of the equipment, are printed circuit boards, capacitors, inductors, resistors and Other Parts? What role do these parts play on the crossover?
The various functions of the various components on the crossover have different functions. For example, the Capacitor only allows high-frequency signals to pass, so it is called a high-pass filter; the inductor only allows low-frequency signals to pass, so it is also called a low-pass filter; the resistance is used to prevent Or reduce the amount of current flow, so the main function of the crossover is to reduce the amount of sense, and it is usually used at the positive electrode of the tweeter. If the resistance is connected in parallel with the monomer, it is not used to reduce the sense of quantity! It is used for impedance matching, because the series resistance in front of the monomer positive electrode reduces the amount of sense, and the monomer will reduce the efficiency because the impedance is increased in series with the resistor. In this case, a resistor must be connected in parallel to the monomer. The impedance of this part returns to the original impedance value, which is the role of impedance matching.
After the above brief explanation, we can clearly know the reason why these components are used in the crossover, and the functions of these components. Next, let's briefly introduce the crossover circuit for you. Let's take the low-pass filter as an example: the first-order crossover is to connect an inductor in series with the positive pole of the monomer; the second-order crossover is the first-order crossover A capacitor is added to the sound line, but it is not in series! It is in parallel with the monomer; the third-order crossover is of course also built on the second-order crossover circuit. It is too troublesome to explain in text, so please look directly at the picture! The fourth-order crossover is like two sets of second-order crossovers added together, of course, please see the picture for clarity. What about the high-pass filter circuit? Simple, you just need to swap the components of the low-pass filter just now! That is to say, the position of the inductor is replaced by a capacitor, and the capacitor is replaced by an inductor.
After briefly introducing the crossover, let's go back and look at the crossover design of BBC LS 3 / 5A! The crossover line configuration developed by BBC Company shows that LS 3 / 5A is a standard second-order crossover. At the same time, it uses many seemingly simple but actually very cumbersome lines to divide the frequency: Like the inductance in the high-frequency line, it is used as a circuit shunt and autotransformer; the frequency response of the high-frequency section is adjusted by resistance and capacitance; the frequency characteristics and response curve of the bass unit are raised, and another Group RL lines are used for equalization.
Since all manufacturers have to use the same crossover circuit, where does the difference in sound come from? Leaving aside other factors, the part of the crossover is good. The reason lies in the "parts". Spendor uses self-made parts, and is authorized by BBC company, instead of using E & I winding inductors, but using iron powder inductors; Rogers company uses iron powder core inductors.
The three speakers used to replace the LS 3 / 5A are based on exclusive technology in the design of the crossover. Although the configuration of the parts has many similarities with the LS 3 / 5A, but from the perspective of equipment design Seeing that there is already a great division. Like the use of parts, there are many differences. Roger need not use pure iron / iron core inductors that the company has long insisted on; Harbeth is also an iron core inductor. Of course, not only the inductance is changed, but other things like metal film resistors and PP capacitors have also emerged.
The setting of the crossover point has a huge impact on the sound performance, so it must match the characteristics of the monomer.
Crossover point
In short, the function of the crossover point is to separate the working range of the two horns. Its action is like using a construction worker to screen fine sand and stones with a mesh screen. Fine sand smaller than the mesh size of the mesh will fall to the floor through the mesh screen. Stones larger than the mesh size will stay on the mesh screen. At this time, we can compare the fine sand to a high-frequency signal and the stone to Low-frequency signals, what about mesh screens? Yes, it can be regarded as a crossover point, and the size of the mesh can determine the size of the fine sand particles, of course, the level of the crossover point! As for the number of crossover points of a pair of speakers, it depends on the design situation. The two-way speaker has only two monomers, so as long as a crossover point is set between the high and low units; the three-way speaker uses high, medium and low units, so there must be two Frequency division points, the audio signal is divided into high, medium and low frequency bands, and then each is provided for the sound of the monomer; four-way speaker? ! rare! According to the above method, there are of course three frequency division points.
When you see this, you must ask: What is the basis for setting the crossover point? How to set it? The first question is not difficult to answer. As long as you have purchased imported monomers or browsed the website of the monomer factory, you will see some test information about the monomer. The designer is based on the original monomer factory. Characteristic data, to formulate the roll-off slope of high and low monomers. As for the setting of the crossover point, it is calculated according to a precise formula, and then a value is estimated, and then the inductance and the selected capacitor are made according to this value. For a detailed explanation, please refer to the "Splitter" section.
After understanding the significance of the crossover point, we can further explore the design of the LS 3 / 5A; generally two-way bookshelf speakers, because only two high and low range monomers are used, so the setting of the crossover point You must pay extra attention, otherwise, the problem will be big! Because the most sensitive sound frequency of the human ear is about 2KHz-3KHz, if the crossover point is set within this range, the human ear will be easy to distinguish, and will feel that the sound emitted is like being divided into two individual The horn sounded the same. If the crossover point is set too low, it will affect the performance of the intermediate frequency, because the tweeter must be responsible for the sound of the intermediate frequency. Do you think this will sound good? If the crossover point is set too high, the bass unit must also emit a higher range of sound, which is very likely to exceed the LS 3 / 5A crossover point with its original design. It is very cleverly set at 3KHz, Its focus is on the integrity of the pronunciation of the two monomers.
The three speakers that replace LS 3 / 5A have different set points because of the different monomers, speaker volume, speaker materials, sound absorption materials, etc. used by various manufacturers, but the focus and considerations are still the same Must follow the above method.
In order to obtain a better sense of low-frequency volume, the small horn with a closed design uses a closed chamber to control the amplitude of the piston movement with a high Q value. If there is an air leak, it must be overcome, otherwise the sound performance will be greatly distorted.
Damping coefficient
This term refers to the characteristics of the monomer, and the so-called damping coefficient is also commonly known as the "Q value." This part can be divided into two types: mechanical Q value and electrical Q value. The mechanical Q value refers to the parts with no magnetic field and electricity such as elastic wave, suspension, cone. The electrical Q value refers to the voice coil and the magnet part. The higher the Q value of the monomer, the greater the sense of low-frequency volume. As for the value of the Q value, it depends on the preferences of the speaker designer or the needs of the product. The Q value of general speakers is about 0.7-1.0, and the LS 3 / 5A is set at 1.2. Of course, this is to make the subwoofer's small caliber 3 / 5A give a better sense of low-frequency volume.
In addition, it must be mentioned that high-Q monomers have larger amplitudes of piston movements before and after. In order to avoid that the piston movement of the previous signal has not stopped, the next signal is transmitted into the monomer to cause distortion (overlapping distortion). Therefore, the closed box is often used to control the quantity and energy of the piston movement. At this time, you must ask: How does the closed box control the movement of the single piston?
To answer this question, we should first talk about the design of the reflective cabinet. Because the amplitude of the low-Q monomer is smaller before and after the piston movement, the speed is fast and the number of times is small, and the overlapping distortion of the signal is less likely to occur. At this time, the designer can apply it to the reflective cabinet in response to such characteristics. In the design, the back wave generated by the reciprocating motion of the monomer is used to increase the sense of low frequency, because the low frequency must be generated by the cone pushing the air. Of course, the reciprocating motion will push the air forward, and the back Of course, there will be another back wave in the movement. Of course, this back wave is also a kind of low frequency wave. These back waves pass through the opening of the box, and of course they can enhance the sense of quantity of low frequency! At this time, the designer can also control the intensity of these back waves by increasing or decreasing the size of the reflection aperture and the length of the pipe according to personal preference for low frequency.
Since the reflective speakers are designed using the characteristics of low-Q monomers, then turning back to the closed design like BBC LS 3 / 5A, we have to pay attention to the Q-value characteristics of the monomers! Since the amplitude of the reciprocating motion of the piston of the high-Q monomer is larger than that of the low-Q monomer, the movement of the monomer must be controlled by a closed box to avoid the previously mentioned overlapping distortion.
(The dark black part is the asphalt glue that suppresses the co-vibration.)
Cabinet material
The common speaker box material in modern times is, of course, compressed dense board, so-called MDF. The Discovery channel used to produce high-pressure dense board a while ago. It consists of squeezing fine wood debris through high-pound pressure After formation. These MDF boards will have different resonance frequencies due to the particle size, composition material, and density of the materials used. Of course, these MDF boards will have a certain impact on the sound generation after they are used as speaker boxes!
At that time, the material of the LS 3 / 5A cabinet specified by the BBC company was a material called Plywood. You must be curious about what material Plywood is? Do you know the clever? Hey Plywood is the so-called plywood. The reason why the BBC company used plywood at that time was purely because of the material science at that time. It was not as advanced as modern times. Therefore, the most easily available material was used as the box material. Do n’t mistake it for the BBC company "cutting the labor" or what is there Secret technology exists. Is plywood good or MDF good? From the perspective of modern science, of course MDF is good, but as long as the sound of LS 3 / 5A is good, would you care about the cabinet material? ! Now that the stuffing on the inside is over, let's talk to you about the skin! You must have heard that rose veneer sounds better than walnut veneer! why? The reason is bound to be divergent, it is okay to provide some information here for your reference, maybe you can solve this mystery!
Why the difference in wood veneer will cause the difference in sound, this should be similar to the application of asphalt glue inside the box, because everyone knows that different stickers will affect the harmonic frequency and therefore will cause changes in timbre. In this case, the veneer on the outside of the cabinet will of course also affect the sound performance. Take rosewood and spruce, which are commonly used in musical instruments, for example. The density of Rosewood is 0.777, and the coefficient of dynamic elasticity is 1.40. The internal friction coefficient is 7.4, the longitudinal sound velocity is 4243, the density of spruce is 0.427, the dynamic elastic coefficient is 1.25, the internal friction coefficient is 6.4, and the longitudinal sound velocity is 5392.
These data show that spruce has a low specific gravity, a large coefficient of dynamic elasticity, a small internal friction coefficient, and a high longitudinal sound wave velocity. Therefore, it is very suitable for use as a piano castanets. The rosewood has a large specific gravity, a large dynamic elastic coefficient, a large internal friction, and a low longitudinal sound wave speed, so the acoustic characteristics are not very good, but its material is tough, strong, and the surface texture is beautiful, so it is often used as a musical instrument. Backplane use.
From the above two examples, it should be easy to see the correspondence between the outer skin of the cabinet and the sound performance. Of course, these two examples are not enough to prove the difference in sound between the appearance of LS 3 / 5a of rosewood and walnut wood. The reason for these two examples is because they want to make it easier for readers to understand. If the cabinet has any influence on the horn, if there are any mistakes in proof, please readers do not hesitate to correct them.
The three speakers are intended to replace the LS 3 / 5A. The box material is the new favorite "MDF board" of modern speakers. The intention is of course to take advantage of its compact texture, easy processing, less resonance and less sound ... etc. The exterior is then covered with original wood veneer, so the degree of beauty is naturally of course.
Box structure
The internal structure of each brand LS 3 / 5a is manufactured according to the BBC specifications. As for sound absorbing materials, each manufacturer uses polyurethane foam as the sound absorbing material, and these sound absorbing foams are filled with The inside of the box is used to absorb the back wave generated by the movement of the monomer. The material that suppresses harmonic vibration is like the black asphalt patch used by the Harbeth company in the speaker box body. The companies that authorized the production of LS 3 / 5A at that time made holes in the asphalt patch and applied it to the box. The side plates inside the body are used to increase the damping, and the top and bottom plates are also covered with asphalt patches, but they are covered with two layers.
In addition to these sound-absorbing and harmonic-damping materials, the foam gasket of the single frame cannot be missed! Guess what, what is the role of this circle of gaskets? You must have guessed that smart, yes, the main purpose of this circle of soft foam gasket is to seal it. In the state of high-pressure sound, if there is air leakage in the cabinet, there will be "sizzling" noise. This noise is not only annoying, but also affects the performance of the sound, so this ring is important for sealing gasket Sex cannot be ignored!
After reading the inside of the cabinet, let's turn the visual focus to the appearance of the cabinet! First of all, of course, talking about the tweeter. Do n’t be surprised when you see the hemispherical iron mesh. Since the pair of speakers were mainly used for outdoor listening, there was always a movement and disassembly. In order to I am afraid that the handling process will cause damage to the raised tweeter, so the design team added a protective iron mesh to this tweeter to avoid unnecessary damage. There is no secret technology in it, so do n’t get me wrong. !
The wool felt on the edge of the monomer is different from the iron mesh just mentioned, but it does not have any protective effect, mainly because the diaphragm of the tweeter is small and the diffusion angle is close to non-directional, so in order to prevent it from being protruded when it sounds Because of the interference of the box board, the wool felt is added around the tweeter to reduce the edge interference of the box board.
The speaker design of the other three speakers has changed greatly from the front baffle. The LS 3 / 5A has a small protruding box board on the front baffle. The new generation of speakers does not have this design, so it is attached to the tweeter The felt around the body is gone; and because there is no need to consider the problem of handling, the metal protective cover of the tweeter is completely eliminated; the speaker terminals on the back, not only the terminal materials are different, but also the connection method is closer Modern designs all use Bi-Wire terminals (a special statement, the commercial Spendor LS 3 / 5A, the terminals behind are also Bi-Wire designs).
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Design and specifications of the new generation of speakers
Next, we sorted out some basic information of LS 3 / 5A and three new generation speakers, and made these data into a table for interested readers to compare.
The outer box material is the last generation LS 3 / 5A: plywood box, except for the barrier plate and the back plate surface, the rest are pasted with black asphalt glue to suppress resonance.
Rogers Studio 3: MDF board, the exterior and interior are covered with wood veneer at the same time, the inside of the box is removed from the barrier surface, and the rest are all pasted with black asphalt glue to suppress resonance. The left and right side boards are added with sticker fiberboard and the box is 10mm thick.
Harbeth HL-P3ES: MDF board, both the exterior and the interior are covered with original wood veneer, the inside of the box is removed from the barrier surface, and the rest are pasted with black asphalt glue to suppress resonance. The left and right side boards are added with sticker fiberboard, and the box thickness is 10mm.
Spendor S3 / 5: MDF board, the exterior and interior are covered with wood veneer at the same time, the center of the box is reinforced with columns, the inside of the box is removed from the barrier surface, and the rest are nailed with black plates to suppress resonance. The thickness of the box is 15mm.
The baffle constitutes the last generation LS 3 / 5A: concave design
Rogers Studio 3, like LS3 / 5a, uses a concave design.
Harbeth HL-P3ES: Graphic design, using the company's no-winding mesh design.
Spendor S3 / 5: Graphic design, plus a black dust cover.
The last LS 3 / 5A of the tweeter: KEF T27 27mm Mylar diaphragm.
Rogers Studio 3: Use Seas monomer.
Harbeth HL-P3ES: Use Seas 19 TAFD / GB monomer, impedance 8 ohms.
Spendor S3 / 5: Use Vifa TC20SD05-06 monomer, impedance 6 ohms.
The last bass unit LS 3 / 5A: KEF B110 SP1228 110mm Bextrene cone.
Rogers Studio 3: Use Rogers DU-125-ST3 monomer, the cone is made of translucent plastic material, rubber overhanging edge, no anti-magnetic design.
Harbeth HL-P3ES: using Seas E14RC / TV-HB monomer, cone is made of plastic material, rubber hanging edge, with anti-magnetic design.
Spendor S3 / 5: Bass monomer: Spendor company designs and manufactures its own monomer, the cone is made of plastic material, rubber hanging edge, with anti-magnetic design.
The original LS 3 / 5A of the original specifications: frequency response 70Hz-20KHz, efficiency 83dB, average impedance 11Ω, weight 5Kg, withstand power 30W.
Rogers Studio 3: Frequency response 80Hz-21KHz, efficiency 85dB, average impedance 8Ω, weight 5Kg, withstand power: 45W.
Harbeth HL-P3ES: frequency response 78Hz-20KHz, efficiency 83dB, average impedance 6Ω, weight 5.9Kg, withstand power: 50 watts.
Spendor S3 / 5: frequency response 70Hz-20KHz, efficiency 83dB, average impedance 8Ω, weight 4.7Kg, withstand power: 70 watts.
Speaker input terminal last LS 3 / 5A: Large gold-plated speaker terminal, using Bi-Wire design.
Rogers Studio 3: Bi-Wire design.
Harbeth HL-P3ES: Large gold-plated speaker terminals, using Bi-Wire design.
Spendor S3 / 5: Large gold-plated speaker terminals, using Bi-Wire design written in the last analysis of the frequency division point, damping coefficient, cabinet material and volume and other factors, will affect the overall sound quality, tone presentation, and is As soon as the overall situation is launched, as long as any one of the items changes, the overall sound performance will change. Of course, the factors just mentioned are not enough to represent all the good sound conditions of the LS 3 / 5A. In fact, the speaker monomer is also an extremely important key, but in recent years, various audio magazines have introduced the monomer Mostly, we do n’t want to get the axe in the door and continue the mink, so we will pass the introduction of the monomer here. Friends who are interested can refer to the introduction of other magazines. This chapter only discusses the design differences of each pair of speakers. The sound performance will be introduced by the following chapters.
The world-recognized small reference speaker, LS3 / 5a shows precise results. Especially designed for listening to small broadcasts, each one is carefully selected by BBC specifications. In the home environment, LS3 / 5a is more pure and flawless, especially suitable for the playback of classical music.
specification:
Category: Two-way infinite baffle type Sensitivity: 83 decibels (1 watt 1 meter)
Frequency response: 70 Hz-20,000 Hz (+/- 3 dB)
Medium and low range: B110 computer optional unit tweeter: 19 mm diameter phase correction unit crossover network: two-wire, BBC FL 6/38, crossover frequency 3000 Hz;
Impedance: 11 ohms Recommended power amplifier power: 25-80 watts Sound box: 12 mm thick birch multilayer board Exterior decoration: rosewood, black wood, walnut surface net: black volume (mm): 304 (height) x 190 (width) x160 (deep) 
Related pictures on this topic are as follows: 
The Q value of general speakers is about 0.7-1.0, and the Q value of LS 3 / 5A is set at 1.2. This of course is to make the bass of the subwoofer 3 / 5A small, giving a better sense of low-frequency volume.
The LS 3 / 5A cabinet material is made of plywood. Why the difference in veneer will cause a difference in sound? This is similar to the asphalt glue applied inside the cabinet, because everyone knows that different stickers are used. Will affect the harmonic frequency and therefore will cause changes in timbre.
The material that suppresses harmonic vibration is like the black asphalt patch used by the Harbeth company in the speaker box body. The companies that authorized the production of LS 3 / 5A at that time made holes in the asphalt patch and applied it to the box. The side plates inside the body are used to increase the damping, and the top and bottom plates are also covered with asphalt patches, but they are covered with two layers.
As far as sound-absorbing materials are concerned, every manufacturer uses polyurethane foam materials as sound-absorbing materials. These sound-absorbing foams fill the interior of the box to absorb the back waves generated when the monomer moves.
In addition to these sound-absorbing and harmonic-damping materials, the foam gasket of the single frame cannot be missed! Guess what, what is the role of this circle of gaskets? You must have guessed that smart, yes, the main purpose of this circle of soft foam gasket is to seal it.
The wool felt on the edge of the monomer is different from the iron mesh just mentioned, but it does not have any protective effect, mainly because the diaphragm of the tweeter is small and the diffusion angle is close to non-directional, so in order to prevent it from being protruded when it sounds Because of the interference of the box board, the wool felt is added around the tweeter to reduce the edge interference of the box board. Related pictures on this topic are as follows: 
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