How to trim the bass on a speaker

How to cut low frequencies on a speaker. Tips for mixing basic instruments

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Tweeter

Clearly, if it is difficult to reproduce the whole range with a single transducer, it makes sense to divide the range into several frequencies, each with a separate loudspeaker. The tweeter (squeaker) is responsible for the high frequencies in this case.

This driver should have a small cone (diaphragm), but it should be sufficiently stiff and as light as possible, because the tweeter’s bandwidth, in most cases, is at least 1.5 kHz. Among drive units, the dome tweeter is the most common. In a tweeter, the central body of the cone, or what in a full-size speaker is called a dust cap, occupies almost the entire radiating surface area.

The tweeter of the Apple HomePod speaker

Dome diaphragms are most commonly made from fabric proofed to increase stiffness. Stiffer materials are also used, with beryllium being widely regarded as the best.

An important tweeter parameter is the frequency of its own resonance. The designers tend to keep it below its output bandwidth. In this case, the squeaker sounds as accurate as possible. The fact is that at frequencies close to resonance the amplifier-speaker complex begins to malfunction, it goes haywire and the system becomes poorly controlled.

The result is distortion, in a frequency domain where our ears are particularly sensitive. The solution is simple: the crossover is a device which limits the tweeter’s frequency range and clips off the frequencies below the tweeter’s own resonance, which usually starts at around 2-3kHz.

Seas Excel E0100-04 Diamond Diaphragm Tweeter

The second requirement of tweeter performance is a high upper limit frequency. Optimally this should be above the upper frequency threshold of the audible range, t.е. Be over 20kHz. It would seem that why go higher when we can no longer hear anything at these frequencies??

The upward frequency range extension allows the tweeter to reproduce the so-called ‘higher harmonics’, producing the most accurate high frequency sound. To what limit a tweeter should be able to go, which is often said to be 40 or even 60 kilohertz, is a matter of some debate.

The two tweeter design requirements are mutually exclusive. To keep the resonance down, you have to make the diaphragm bigger and lighter, and vice versa, to raise the upper limit of the AFC. The answer is the maximum stiffness to weight ratio of the tweeter diaphragm, which is what the technological battle is all about.

Midrange speaker

A driver that plays midrange frequencies (also sometimes referred to as a midrange speaker, a term that comes from car audio) is usually the closest in construction to a classical speaker. Importantly, this driver reproduces the range of frequencies in which the human voice is located and where our ears are particularly sensitive to distortion.

An example of the behaviour of a drive unit measured using a laser interrogator

The Achilles’ heel of the midrange is the effect of a specific bending wave, where the peripheral area of the cone doesn’t quite keep up with the movement of the sweet spot where the voice coil is mounted. This means that the different parts of the cone (which are generally arranged in patches, not concentric as the logic of the process would dictate) vibrate out of phase, with some parts lagging behind others.

So you get a loose, imprecise sound. So the diaphragm has to be as stiff as possible. If you tackle the problem head-on, you end up with a really stiff cone, which weighs so much that it will fail to deliver. So, like a tweeter, like a full range speaker, it’s a very difficult trade off between stiffness and lightness.

Midrange driver l SCM 634 with carbon cone

With high-end speakers, cone design is really important. In exotic applications, midrange speakers (just like tweeters but much rarer) are given a beryllium cone. But it is much more common to see midrange drivers made of carbon, fiberglass, Kevlar, wood fiber or classic cellulose-based composites.

Midrange speaker

The speaker that plays midrange frequencies (sometimes called a midrange speaker. the term comes from car audio) is usually the closest in construction to a classical speaker. Importantly, this speaker reproduces the range of frequencies in which the human voice is located and where our ears are particularly sensitive to distortion.

Example speaker behavior, as measured using a laser interrogator

The Achilles’ heel of the midrange is the effect of specific torsional deformation. a kind of bending wave where the peripheral area of the diaphragm fails to keep up with the movement of the sweet spot where the voice coil is mounted. That is, the different areas of the diffuser (which, incidentally, are usually arranged in patches, rather than concentrically, as the logic of the process would suggest) do not oscillate in sync. some areas lag behind others.

trim, bass, speaker

This leads to a ‘loose’, imprecise sound. So you need to make the cone as stiff as possible. If you tackle the problem head-on, you end up with a really stiff cone, which weighs so much that it will fail to give a good sound. So, like tweeters and full-range speakers, cone design involves a difficult trade-off between stiffness and lightness.

Midrange driver l SCM 634 with carbon cone

For high-end speakers, cone design is a critical consideration. Exotic midrange drivers (along with tweeters, but much rarer) feature a beryllium cone. But it is far more common to see midrange drivers featuring a composite material such as carbon fiber, fiberglass, Kevlar, wood fiber or classical cellulose.

Woofer driver

The bass driver is often also called a woofer. In almost any class of loudspeaker, the woofer is naturally the largest transducer. Fully reciprocating operation, where the cone moves in a reciprocating motion as a unit is preferred in the bass.

Here the problem is solved even more radically than in the case of the midrange driver. Make the cone as stiff as possible, even at the cost of making it heavier. The fact is that at low frequencies, our ears are the least sensitive to distortion. When amplitude is particularly important for a woofer’s cone, extra weight is often necessary for the sake of stiffness.

24″ bass driver in a Pro Audio Technology subwoofer

Many large subwoofers can have a moving system weight of up to 200g or more. Diffusers in some cases are built like an airplane wing out of a sandwich composite and the inner cavities are filled with lightweight honeycomb or honeycomb structures.

For audiophile systems, they still tend to minimise the weight of the bass driver cone, because an untrained ear doesn’t like bass distortion as much as anyone else.

And the amplitude of the vibrations in woofers is the largest of all the listed speakers. For this purpose, they are equipped with the so-called long-throw (elongated) voice coil. Outer suspension is made of rubber. All this allows the cone to have a very large excursion. the movement of the cone away from its center point.

JBL 18″ bass woofer

The “nature” of the bass driver is especially apparent in the drivers, which are installed in subwoofers. These are heavy, powerful units with diameters ranging from 8″ to 15″ (the most common size range used in custom speakers). They have very powerful magnet systems and, as a result, a considerable overall weight. These low frequency drivers powered by high powered semiconductor amplifiers often have driver coils with as little resistance as 2 or even 1 ohm.

Klystron Amplifier

The principle of the klystron low frequency amplifier is based on modulating the signal first in speed and then in density.

A klystron is arranged as follows: the bulb has a cathode heated by a filament, and a collector (analogous to an anode). In between are the input and output resonators. The electrons emitted from the cathode are accelerated by the voltage applied to the cathode and rush to the collector.

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Some electrons will move faster, others slower. this is what the speed modulation looks like. Because of the difference in speeds, the electrons are grouped into bundles. that’s how density modulation appears. The density modulated signal travels to the output resonator where it creates a signal of the same frequency but higher power than the input resonator.

It turns out that the kinetic energy of electrons is converted into the microwave oscillation energy of the electromagnetic field of the output resonator. This is how signal amplification occurs in the klystron.

Setting up the “subsonic

After that it is necessary to engage the filter, which is called “subsonic”. In essence, it is a high-pass filter that works in the sub-bass area. Simply put, it cuts off the infralow frequencies and lets everything above it through. Not all amplifiers have subwoofers. But if your speaker works as an FI or CV loudspeaker, you should choose an amplifier which has such a filter.

Why do you need a “subsonic”?? The thing is that a subwoofer speaker will also try to reproduce frequencies outside the audible range, for example 20-25 Hz and lower. At those frequencies the move of the cone gets longer and it can cause damage to the voice coil. The subwoofer cuts off all “infra” and prevents the speaker from overshooting. Besides, the quality of reproduction of the desired bass range only improves, and the volume increases.

The subwoofer should be set about 5 Hz below the frequency of the reflex port. For example, if you tune it to 35 Hz, you would have to tune it to 30 Hz. To do this, you turn the switch on and turn the “knob” to the desired numbers.

To connect a tweeter through a capacitor

A tweeter connection consisting of just a capacitor is called a high-pass filter or passive first order crossover. It’s called a “high-pass filter,” and it works like this. The capacitor capacity determines the cutoff bandwidth. This does not mean that frequencies below the cutoff will not be reproduced by the high-pass filter.First order crossover has a sensitivity of 6 dB (decibels) per octave. An octave is half that or more. If the cutoff is 2,000 hertz, then the frequency that is an octave lower, ie 1,000 hertz will sound 6 dB lower, a cutoff of 500 hertz will be 12 dB lower and so on.

Based on the size and stiffness of the tweeter cone, we can assume that the low frequencies will not significantly affect the reproduction of the high-frequency range. There are more complicated second-order crossovers, whose circuit, in addition to the capacitor, includes a choke. They provide a power reduction of 12 decibels per octave, and third-order filters allow you to get a reduction of 18 decibels per octave.

What kind of capacitor to put on the tweeter

To get the best sound from your speakers, you need to be very careful when choosing a capacitor. What kind of capacitor is needed for a tweeter? Chinese manufacturers of inexpensive speakers put in series with the coil of the high-frequency speaker an electrolyte with a capacity of 2-10 μf.

trim, bass, speaker

Products of this type are polar and by definition intended for DC circuits. They don’t behave quite right on AC, so to connect a high-frequency speaker in a two- or three-speaker setup, you need to use film products with the appropriate capacitance. If you have an inexpensive Chinese-made speaker system, it is enough to open it and replace the electrolyte with a polypropylene or paper capacitor to feel the difference.

If the necessary capacitance is not available, the necessary capacitors for the tweeter are assembled from several products connected in parallel.Of the domestic products, you can use K73-17 and K78-34. These are lavsan and polypropylene products. The K78-34 type was specially designed for installation in filters of high quality loudspeakers. It operates correctly at frequencies up to 22 kHz for speaker outputs up to 220 Watts with 4 ohm loudspeakers.

To correctly select a capacitor for a 4 ohm tweeter you need to know its resonant frequency. High-frequency heads may have a relatively low resonance frequency of the order of 800-1,200 Hz, but most “tweeters” will resonate at 2,000-3,000 Hz. Capacitor values for different cutoff levels to the 4 Ohm speaker are as follows:

You should cut the band with the first-order filter above the resonance, otherwise the speaker will vibrate unpleasantly when reproducing the sound. It is recommended that the cut-off frequency of the filter should be approximately twice the resonance value of the high-frequency loudspeaker.

Hi there! In this post, I decided to raise an important topic for many beginners. Let’s try to understand it, look into it, make conclusions and give advice. Let’s go!

It’s about choosing capacitors for horn loudspeakers. That’s how all the newbies pose the question. We are very smart and experienced experts so let’s rephrase it more precisely. How to choose a passive high pass filter for horn loudspeakers.

First let’s remember what this stuff is, what it does, and how it works?We need crossovers to cut off unnecessary frequency ranges of sound from the speaker giving it the bandwidth it needs to work properly.There is nothing to worry about with subs in this respect. Even if you give the whole band to the sub, nothing will happen to it. But when we talk about speakers of any design, for them, the crossover will determine their life, sound and durability.

The second point that’s important to understand: any crossover does NOT cut off frequencies drastically. If your high-pass filter is set to, say, 3 kilohertz, it doesn’t mean that the speaker will stop sharply below three. The speaker will be singing at 2 and 1 kilo and 500 Hz and even 20!The question is how much power will be delivered to the speaker at those frequencies and how much and how fast will the volume drop outside of the crossover setting.This point is determined by the crossover cutoff order. 1st, order (6db/oct). 2nd (12db/oct), etc.д. What do these dB/oct. mean?Well, there’s no question about the dB. dB dB-decibels determine the volume level (or sound pressure level to be more precise, but whatever) but Octo that’s an octave. An octave is(Bellin, how can I put this in a simpler way?) An octave is a range of frequencies that is either half the frequency of the current frequency or half the frequency of the current frequency. I don’t get it. :D:D Let me explain by example: Let’s assume we have a 1st order high pass filter at 1 kilohertz (1000 Hz). Such filter skips high frequencies to the squeaker and cuts low frequencies. So the filter of the first order (6dB/oct) means that below 1 kilohertz the sound will not disappear, but the volume will go down.If we had a speaker that sings at 100 decibels at 1 kilohertz, then below the filter setting by one octave (1000Hz/2=500Hz) at 500Hz the speaker would sing 6 decibels quieter. And if you go one octave lower (500/2=250hz), it will be 12 dB quieter, 125hz will be 18 dB quieter, and 63hz will be 24 dB quieter, and so on.If we were to cut the speaker at the same frequency but by the 2nd order (12dB/oct), we would lose 12dB at 500Hz, 24dB at 250Hz, 36dB at 125Hz, and 48dB at 63Hz.You can calculate any order of the filter at different frequencies.

This example, of course, is extremely simplistic and crude. The speed and uniformity of fading will depend on 100500 more factors, but in principle the example reflects the essence we need. Precisely because a squeaker will always sing and below the cutoff frequency, it is highly discouraged to make a cutoff near their resonant frequency below which they become extremely difficult to operate. At best it will reduce its volume many times over (you just can’t get it to full volume without distortion). At worst the squeaker would die. You’ve learned this fact and move on. There everything is even more complicated and unclear :D.

The next important aspect of this case has been flattened in the minds of newbies by tables like this on the internet:

The tables are actually correct.would be if it were not for one thing. there are no speakers 4 ohms, or 2 ohms, or 8 ohms. And it never was. ))

It’s not the impedance which is printed on the loudspeaker, it’s the MINIMUM impedance the loudspeaker can have when it works.This criterion is very important for the stable operation of the amplifier without overloading. But it doesn’t mean, that the impedance can’t be higher with the speaker. I’ll tell you more, it’s almost always higher, the question is how much higher and when. (by the way you can use a multimeter to measure your 4 ohm loudspeakers. It will always be a little less than 4 ohms there. 3.7-3.(8 ohm precisely because you’re measuring impedance and you’re measuring impedance.) ). So the impedance of the speaker when you play the sound depends on a lot of factors, starting from the design of the speaker and ending with the design of the speakers (and after all a horn loudspeaker is a loudspeaker in the ROOP) and frequency. This last factor is especially interesting when we’re talking about high frequencies.If you take two 4 ohm loudspeakers and measure their impedance at 5 kilohertz, you can get a 5 ohm impedance of one loudspeaker at this frequency and a 7 ohm impedance of the other one. Then, according to the table above, trying to cut them to 5 kilohertz with a capacitor at 8 microfarads. If you do the same capacitor, the first one will be at 4 kHz, and the second one with the same capacitor will be at 3 kHz! Accordingly, the first one will just dump a shit sound, the second one will start to burn.To give you an example, here is a graph of the system impedance versus frequency (Z-score) for component speakers:

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What is frequency processing??

The process of frequency filtering consists in decreasing or, conversely, increasing the frequencies in a certain spectrum. Thanks to special tools and plugins, you can equalize as accurately as possible, removing or adding a few Hertz (the unit of measure for filtering). There are many applications of such processing: removal of conflicting frequencies, reducing the volume of unpleasant to the ear noises, forming the “body” of the sound signal, enriching the recording with harmonics, and much more.

Also, one of the main tasks of the equalizer is to “clean up” the space in the mix, i.e.е. after processing every instrument, alive or electronic, should occupy its own place and not disturb others. For example, bass sounds are usually centered and underneath, midrange instruments (guitars, snare drum, keyboards) are in the middle and vocals are better “pushed up” so they can be heard over all the tracks.

It is important to make Accent on removal of unpleasant sounds. by moving some sliders on EQ you can get rid of clang of guitar strings, noise of cymbals and singer’s sighs. However, it is important not to overdo it and not to cut out “useful” frequencies that enrich the sound and make it three-dimensional.

Types of Filters

The equalizer contains different types of curves with which you can filter frequencies. They are divided into:

Limiter filters

These curves cut off all frequencies that are behind them “firmly”. You can adjust the degree of slope by going from a vertical straight line (“brick wall”) to a small cut in the area of 1-3 dB. These include:

    Low Pass (or High Cut, on the contrary). with this filter, all frequencies above the marked point are removed from Spectra, and all the frequencies below are left.

It’s mostly used to trim the top of the bass and put it harmonically in the mix, as well as to give the instruments depth and clarity, remove ringing and rustling.

Most often used to remove bass for instruments whose fundamental frequencies are in the mid to high range, thus leaving the “bottom” of the mix directly to the bass and kick drum.

Notch filter

Or “band-limiting.”. Cuts frequencies in a narrow bandwidth only. Gets rid of all unpleasant noises. A sound engineer’s assistant for spot-processing recordings.

Shelf Filters

Have a straight shape, also available in High and Low. The first is used to compensate for the missing treble, the second, respectively, for the low frequencies. You can create a combination of these curves by raising and lowering the frequencies of a track simultaneously, in which case you get a Tilt Shelf.

Presence filter

The most popular is the bell-shaped filter. It has a rounded shape and amplifies the selected range.

So, for guitars, the most commonly used amplification is around 500 Hz to give “body” and “roundness” to the sound. And for vocals, for example, it is recommended to raise the frequency close to 5 kHz to move it forward and create a “presence” effect

There is also dynamic equalization, where the equalizer and compressor work together. In this case, the selected Spectra frequency is not cut out completely throughout the song, but is attenuated only at the right moments when it reaches a set threshold. This allows you to achieve flexibility in processing the mix because the frequency will sound at quiet moments and will not “stick out” at loud ones.

Methods of damping heads

The following damping methods can be recommended for amateur conditions.

Bypassing the midrange driver with a high-frequency series oscillating circuit tuned to the resonant frequency of the driver inside the speaker. Such a circuit would act as a jumper at resonance frequency and short-circuit the leads of the head. In the working bandwidth, however, its resistance increases so much that the shunt effect is negligible. Loop damping has an effect only when using a high-efficiency mid-range head with a small Qe. In other words, only at Rea, short-circuiting the head leads with a series circuit tuned to its resonant frequency will lead to a marked decrease in equivalent Qt, compared with Qa.

Acoustic damping of the head by means of an acoustic impedance panel (AIP) (cf. article H. Young, V. Shorova and I. Hraban “Acoustic Damping of Loudspeakers” in “Radio”, 1969, p. 27, 28). This technical solution protected by the USSR copyright certificate 77699 allows decreasing acoustic quality factor Qa of the loudspeaker head several times and making it comparable with or even lower than electric quality factor Qe.

Damping of heads with the sound-absorbing material (for example, absorbent cotton) is less effective and promotes increase of their resonance frequency.

PAS Design

In order to increase the effectiveness of the passive acoustic impedance (PAS) on the moving system of the acoustic head, the damping fabric should be placed as close as possible to the cone. The most rational solution is to install the FAS in the holes of the diffuser support, but only a production plant can afford to implement it.

In amateur radio it is easier to make FAS in the form of a separate device and put on the head of the speaker from the side of the magnet (Fig. 5а).

It consists of a cylindrical shell 4, in which the side opposite the head 1, tightly inserted FAS proper. two connected with screws plywood discs 3 with coaxial holes. A damping linen or cotton stretched cloth 2 is stretched between discs. In Fig. Figure 5b shows a sketch of FAC for 15GD-PA, 6GD-6 and 10GD-34 heads. The diameter of the FAC’s shell is larger than the diameter of the bore in the front panel, as the windows in the coneholders of these heads are oriented perpendicular to their axis. The total area of the holes in the bellows should be 0.3-0.4 times the effective area of the diffuser, in this case 22-28 cm2. In the center of the voice coil assembly there is a hole for the permanent magnet of the head and the leads from the voice coil are routed through the hole. The height of the shell must be as low as possible in order to bring the damping fabric closer to the diffuser and to prevent unwanted resonances.

The following order of FAS manufacturing is recommended. First of all from the roofing iron or other suitable sheet material make the shell, and then from plywood thickness of 6-8 mm cut two disks with a diameter equal to its inner diameter. Having fastened the discs together with small screws, mark out the necessary holes and drill them in both discs at once.

Then after marking the relative positions the discs are separated and, placing the damping cloth between them, fastened again with screws.

When all the screws have been driven in, the cloth is trimmed flush around the edges and through the center hole with a sharp knife, the pre-fabricated FAS is fitted inside the shell flush with one of its ends, and the joints are carefully sealed with clay. The PAC shell is put on the head of the loudspeaker and the joints with the head and the panel are sealed in exactly the same way.

To protect from the effects of low frequency components of the signal mid-frequency head should be covered (from the back side) sealing box, which volume should be 3,5-4 times more than the volume of the shell with the subwoofer. In this case the efficiency of the MSS will not be disturbed.

In modifying the industrial equipment, you can use the already available in the loudspeakers boxes. For example, for the medium-frequency ZGD-1 head installed in the loudspeaker of the radio “Symphony” the factory sealing box will be quite suitable. Only need to remove the absorbent cotton and peorized cardboard, which covers the head ZGD-1. For the 15GD-11A Model 35AC-1 loudspeaker head, the sealing box is elongated and therefore the MFH shroud should be an elliptical rather than circular cylinder. Holes must be drilled in the major axis of the elliptical disc.

When modifying the 35AC-213 (S-90) speaker it is possible to use the existing muffler box as the muffler for the Midrange Head End cap. For this purpose it should be cut by a hacksaw at a height of 85 mm from the open edge and in the formed round opening insert a matching size of FAS. MSS should be located at a distance of 15-20 mm from the permanent magnet of the head. The head has to be covered by new sealing box, which has to be made by oneself. The inner volume of the boxes must in all cases be filled with absorbent cotton.

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After installing the sealing box, the effectiveness of the head damping must be checked. For that purpose it is connected to the audio generator and the acoustic quality factor Qa is calculated in accordance with the above mentioned procedure. Given the operating mode of the midrange head, the equivalent quality factor for most modern heads will be Qa. The damping effect of FAS for the ZGD-1 and 15GD-11A heads is illustrated by the curves in Fig.1 and Fig.2, respectively. 6 и 7.

It is then useful to compare the sound of the damped speaker with that of the un-damped sample. For comparative listening one should choose gramophone records with symphony orchestra, choir, piano. the damping effect of the mid-frequency head is most noticeable on such pieces.

It was shown above, that the intermodulation distortions due to the high quality factor of the driving system of the loudspeaker head at the frequency of the main resonance Qt, will always be present in the reproduced signal if the value of this parameter exceeds 0.5. These distortions are especially noticeable to the ear at mid frequencies. They give a metallic appearance to the sound and make it opaque. Therefore, damping is primarily required for the mid-range heads.

For single wideband designs, the damping of the full range driver in the enclosed box will result in a minimum 6dB decay in low frequency response at the main resonance frequency of the driver in the box.

Reduction of resonant frequency of heads

The lower limit of a loudspeaker’s usable frequency range is determined by the fundamental frequency of the head. Unfortunately it is very rare to find a speaker with a fundamental frequency lower than 60-80 Hz. So in order to extend the working frequency range of the loudspeaker systems the possibility of reducing the fundamental frequency of the heads used in them seems very urgent. As we know, the moving system of the head (cone with voice coil) in the main resonance region is a simple vibrational system consisting of mass and flexibility of the suspension. The resonant frequency of such a system is defined by the formula:

where t. mass of cone, voice coil and attached air mass, g; C. Suspension flexibility, cm/din.

So, to reduce the fundamental frequency of the head, either the mass of the cone and voice coil must be increased, or the flexibility of their suspension, or both. The easiest way to increase the mass of the diaphragm is to attach an additional weight to it. Increasing the mass of the moving coil assembly, however, is not beneficial as it will reduce not only the resonant frequency but also the sound pressure produced by the head. The point is that the force F created by the current I in the voice coil of a driver head is

F=BlI, where B. magnetic induction in the gap; l. is the conductor length of the voice coil.

On the other hand, according to the laws of mechanics, this force is equal to

F=ma, where m. mass of the moving system; a. vibrational acceleration.

Since the force applied to the voice coil depends for a given head only on the amount of current, increasing the mass will reduce the vibrational acceleration of the coil and cone by the same factor; and since the sound pressure generated by the head in this frequency range is proportional to the acceleration of the cone, reducing the acceleration is the same as reducing the sound pressure. If we were to try to halve the fundamental frequency resonance of the driver, it would require quadrupling the mass of the driving unit and the same amount of sound pressure from the driver would be lost at the same coil current. So increasing the mass would also increase the Q-speaker’s moving parts and the frequency response would become disequilibrium, with the resulting deterioration in the transient response of the speaker.

Consequently, in order to reduce the resonance frequency of the head, it is more appropriate to increase the flexibility of the diaphragm and centering disc suspension, i.e. to reduce the rigidity of the mounting of the moving system. This is done as follows. First of all the driver collar is glued or cut away with a sharp scalpel or blade (aligned with the ring of the driver housing). Then solder the voice coil flex leads and unscrew the center disk ring and the gethinax

Increase the flexibility of the centering disk with chamfers by cutting three or four cone-shaped holes evenly around the circumference (see “8”). Fig. 1). The total area of these holes should be 0.4. 0.5 times the area of the centering disc corrugations. To protect the magnetic gap from dust, some gauze is glued to the holes or the whole disc with an ordinary rubber glue or BF-6 glue. If the voice coil is centered by a gethinax (textolite) “spider”, the flexibility is increased by reducing the width of its bars (by filing them with a file or carefully biting them with wire cutters). Then cut off a part of the diffuser edge corrugation so there is a gap of about 200 mm between the edge of the diffuser and the ring of the diffuser holder. If a crimp is left at the edge of the diffuser it is straightened out to a length of approx. 10 mm and the suspension is glued to it in the form of povinol or soft textvinyl shackles. If possible, the textile or knitted backing should be removed to increase the flexibility.

Very flexible and elastic shackles can be made with organosilicon glue. Elastosil” sealant from thin kapron stockings. The stocking is cut lengthways and a 24-28 cm wide cloth is marked on the resulting web (see the section about the stocking). Fig. 2). When marking, the shackles should be placed across the stocking (see the “elasto” sealer, see the “elasto” sealer). Fig. 2) because the elasticity of the stocking is greater in the longitudinal direction. Then, after laying a piece of smooth polyethylene film on a piece of board or thick cardboard, place the stocking cloth on top of it and secure it at the edges with buttons or nails. After that, use a spatula or the end of a metal ruler to apply elastosil” to the knit so that the knit threads are not visible. After 24 hours (time of “elastosil” polymerization) the knitted fabric is turned over and the other side is covered with “olastosil”.

A cardboard template should be made to cut out the temples. It is desirable to suspend the diaphragm on no more than three or four arms such that each arm extends one-third or one-quarter of the circumference of the diaphragm, respectively. On the wishbones and on the edge of the diffuser with a pencil mark the surfaces they must be glued, the width of these surfaces should be 7-10 mm. The ready temples are smeared alternately with glue and glued to the marked edge of the diffuser with Elastosil or with silicone glue KT-30 or MSN-7. Pavinol or Textvinyl mouldings are glued to the textile surface using BF-2, 88 or AB-4 glue. It is advisable to first check the suitability (suitability) of the adhesive for the material by gluing a piece of material to a piece of heavy paper.

The joints between the mandrels must also be glued so that there are no gaps. This is best done with “elastosil”, with pavinol or textovinyl shackles, it is recommended to fasten the edges with threads and glue in several steps with ordinary rubber glue.

Once the cone is fully suspended it is inserted into the voice coil support so the voice coil fits into the gap. Then strengthen the ring of the centering disk and make a preliminary alignment of the voice coil (before gluing the suspension). Next, glue one by one the diffuser hanger brackets to the ring of the diffuser support. To unbend the wishbones,

it is convenient to use crocodile clips with single pole forks inserted in them (for gravity) when gluing the ring of the diffuser. after gluing the hanger, the voice coil is finally centred and the centering disk or gethinax “spider” rings are fastened. If the centering disk does not have a metal ring and is unglued, then first glue, the diffuser surround and then the centering disk, at the same time centering the voice coil in the gap. Lastly they solder the voice coil leads and glue the support bars made of cardboard, sponge rubber or felt to the diffuser holder.