In 1978, S90 speakers and the famous 35AC-1 acoustics came from the Baltic Riga to all cities and villages of the USSR, after which this series developed and improved. This legend was constructed at the Riga Production Association "Radio Engineering", in the design bureau "Orbita".

Appearance

Externally, the S90 speakers were impressive at first glance. Such a beautiful case has not been made even abroad, not to mention modern Chinese lines of electronics. It was literally made to last. No chipboards! Only natural wood of valuable species, heavy and expensive. The front wall was made of plywood, but aircraft grade, multi-layered.

Both S90 speakers weighed more than 45 kilograms. The Soviet people fell in love with the new acoustic system immediately and very much. By the way, even today restoration methods are discussed on special forums, and the S90 speakers have received many, many thousands of admiring reviews. And every day these delights increase. Many hundreds of acoustic systems in this series serve faithfully at the present time, which cannot be said about the fly-by-night electronics that are now being produced in the world.

Purpose

A lot can be said regarding the scope of application. The Radiotekhnika S90 speakers were supposed to reproduce high-quality music and speech programs in a residential hospital setting. Of course, they were not in every family, and those who lived in a house where they were not probably were happy. Where they were, on any floor and in any entrance of the apartment building, chandeliers swayed, and crystal tinkled in the sideboards.

One such acoustic system was enough, where the Radiotekhnika S90 speakers did not even work at full volume. The entire five-story building was familiar with the musical tastes of the lucky owner. Life was especially good for his neighbors if he used a Corvette-type amplifier. Soviet S90 speakers were quite expensive - 300 rubles for two pieces, so most often they were bought gradually, one at a time. Even so, they had to pay a little more than the engineer earned in a month. Despite many shortcomings, the ultimate dream of every music lover of the late 70s of the last century was the S90 speakers.

Characteristics

All people who listen to music wanted this speaker system because it was truly a breakthrough in real sound. In those days, literally only a few had imported equipment, and almost no one was satisfied with the sound quality of Soviet tape recorders.

And here the Riga manufacturer produces three-way speakers with a frequency range of up to 20 kilohertz, with a rated power of up to 90 watts (nominally, however, 35, but that’s great). While Soviet sound reproduction equipment was single-way and had a maximum power of five watts, the S90 speakers had excellent characteristics and made a simply stunning impression.

Quality

The demand for them was enormous, more than mass production was established, and therefore all sorts of complaints arose regarding the quality (except, perhaps, for the appearance). Due to the fact that people bought speakers gradually - one at a time, it turned out that they sounded completely different. However, even those who bought two at once often encountered the same problem. Since 1982, they began to be produced and put on sale purely in pairs - left and right, the arrangement of controls and speakers became mirrored, then this problem was slightly smoothed out.

In any case, the S90 loudspeakers became the first system made in the USSR that met the requirements of international documents for Hi-Fi equipment. Moreover, over time, the acoustic systems of this line have been improved. For example, the S-90B and S-90D significantly expanded the frequency range, an electrical overload indication was introduced, and the appearance became even more stylish and expensive.

Details

Three-way floor-standing speaker system, equipped with a bass reflex, with a reproducible frequency range from 25 to 25,000 hertz. The S90 speaker amplifier is available with a recommended output of 50 to 150 hertz. The rated power of the speaker system is 35 watts, the maximum power is 90, the short-term power is 600. The dimensions of the S90 speakers are 710 x 360 x 285 millimeters. The weight of one column is 23 kilograms.

Speakers in the S90 speakers: low-frequency 75 GDN-1-4 with a diffuser diameter of 220 millimeters, mid-frequency 20 GDS-1-8 - 105 millimeters, and high-frequency 6 GDV-6-16 with a membrane of 26 millimeters. The body is rectangular, non-separable, finished with veneer. The wall thickness is 16 mm, on the front panel there is 22 mm plywood. The joints on the walls are rigidly reinforced. The heads have decorative black linings on four fasteners, and inside they are protected by a plastic cone-shaped casing. On the front side the heads are protected by a convex mesh made of black metal. Inside, to suppress resonances and sound pressure, there is a mat made of technical cotton wool and gauze.

Inside

Electrical filters are placed on one of the internal boards to separate the bands of the speaker system. Now lovers of retro acoustics claim that restoration of S90 speakers is not only possible, but will also significantly increase all the capabilities provided by the manufacturer. All the wires located inside are thin and unreliable; restorers replace them with modern copper ones.

The scheme is being revised, the speakers are changing. But much of what was done back in the 70s remains in place. Radio equipment, like many other things, was manufactured in those days with a large margin of safety and was far ahead of its time. Filters and display unit in a design with resistors such as BC, PPB, S5-35I, SP3-38B and MLT, capacitors K75-11, K50-12, MBGO-2, inductors on cast frames.

Included

It should be noted that speakers standing directly on the floor gave lower quality sound than those standing on a pedestal about half a meter high. The manufacturer apparently knew this well, and therefore the kit included plastic legs, four for each column. They could be attached to the base of the body. The kit also included a decorative removable frame, which also had a purely practical meaning.

The thin knitted fabric with which it was covered significantly improved the sound passing through it, having excellent acoustic transparency. The speakers went well with any type of household radio equipment that existed at that time. The author of the development is Roland Paulovich Kerno, about whom there are still legends among people close to acoustics. He began working at this enterprise in the late forties, and literally everything that Radiotekhnika produced was developed by him.

Comparative characteristics

The S90 speaker system is certainly very powerful and modern, but even then it had a long series of shortcomings. However, lovers of good sound repaired the S90 speakers, and then the hum at low frequencies, which certainly arose at high volumes, went away, and the unpleasant clicking noise that is inherent in the high-frequency head 6GDV-1-16 was eliminated (it was replaced in subsequent modifications).

The playback quality may be inferior to some modern speaker systems, but the depth of sound at low frequencies is simply unique. It is very rare to find, say, Chinese subwoofers that provide approximately the same deep bass. For example, in the home theater speaker system Xoro HSD 6040. But the price of these products is not comparable. However, now the S90 speakers are also not cheap, but still significantly less.

For repair: weak points

After so many years, it makes sense to replace the high-frequency and mid-frequency speakers. The low-frequency one can simply be rewound; this not too labor-intensive procedure is described in detail on the Internet. And immediately set the volume knob on the amplifier so that the speaker does not throw the coil out of the magnet, that is, you cannot go to full volume, there is a danger of completely breaking the woofer speaker. The bass reflexes can be covered. And, of course, raise the speakers from the floor - on legs or, in order not to scratch the parquet, on a pedestal, which you will have to make yourself.

Many music lovers from the cohort who were born with a soldering iron modify and improve their favorite speaker systems of the Radiotekhnika brand. The most interesting thing is that once is enough - the speakers will work for another thirty years and even better than before. They remove the cotton-gauze mattress, replacing it with good sound insulation made from two layers of high-quality but inexpensive batting, cover the necessary places with felt, and even restore the case if it has undergone many moves over its long life and is damaged or bent (the wire grilles on the speakers are convex, so it’s no wonder ). Skilled music lovers remade and soldered almost everything, and as a result they received an excellent acoustic system.

Audio cables and diffuser hangers

You can buy a ready-made cable, but many solder the wires themselves. A twisted pair audio cable works well for connecting to a computer, TV or tape recorder, and a copper power cable has proven itself to be excellent for connecting an amplifier to speakers. The cross-section must be chosen at least one and a half square millimeters, and the further the speakers are from the amplifier, the thicker the wire should be.

You need to pay very close attention to the suspensions on the speaker diffusers - mid-frequency and low-frequency. This is rubber along its edge, onto which the diffuser is glued. This rubber must be “original”, from the manufacturer. Otherwise, the diffuser will not attach tightly. The good old suspension is coated with silicone grease, which is sold in special radio stores.

Accessories

First of all, this is an amplifier. The Soviet ones have already exhausted all their expiration dates, but if you have the skills to use a soldering iron, this is not a big deal. An imported amplifier will increase the cost of the already expensive S90 equipment, which still needs to be repaired. An amplifier that is too modern and expensive will not do anything for these speakers, since the sound quality does not depend on it, but on the speaker system.

Nothing will sound noticeably better. It doesn’t matter what kind of amplifier, even a tube “Priboy-50-UM”, will do. You need to look not at the date of manufacture, but at the power. There is no need for anything stronger than 50 watts per channel, as the walls will dance and the floor will shake. But if you don’t feel sorry for your neighbors, it’s the owner’s business.

Result after repair

If you make a detailed repair of S90 speakers and test their performance carefully, you can achieve results that are almost unsurpassed. Even the JBL floor-standing speaker systems of this year's model, for which you need to pay almost 50,000 rubles, and even together with a Yamaha amplifier, do not provide such beautiful sound.

Refinement inside and outside

When the owner of a 1981 Radiotekhnika has the idea of ​​“finishing” the old speakers with a file, he is unlikely to expect such a result. True, almost everything will have to be redone. Modify the housing, remove all the resulting cracks using epoxy resin, replace the cotton wool and gauze with batting, and completely resolder the wiring in the speakers.

Dismantle the speakers, replace two in any case, and the third can simply be rewound. Covering with batting can be done using a furniture stapler. Glue the bass reflex pipe onto the sealant and cover it with batting. The switches that are on the board are not useful in this speaker system; you can simply turn them off or remove all unnecessary elements from this board altogether.

Sound refinement

All this restoration will definitely make the sound better. But it will become ideal only after a long setup. The bass acquires the missing clarity, the highs become airier and more transparent. But with mid frequencies you will have to fight with persistence. In the center we most often hear vocals. So he clearly lacks sonority. Having tried several other, “non-native” speakers, sooner or later one will turn out to be successful.

There is no need to master the main method of modifying mid-frequency speakers - magic: they say that if you soak the suspension with a magic sealant consisting of two parts of the conductor's blood and one part of acetone, then you can not change the speaker. However, in construction stores they usually shrug their shoulders.

Total financial costs for a complete repair of S90 speakers: very worn acoustics (and still need to change everything except the housing) can be purchased for about a thousand rubles; high-frequency speakers - 500 rubles; mid-frequency speakers - 110 rubles; batting - 150 rubles; glue, stapler staples (you can ask your neighbor for the stapler itself), screws and other small things - it’s difficult to count exactly, but these are trifles. This means that this excellent acoustics will cost a resourceful and skillful music lover less than two thousand rubles.

I have long had a dream - to buy the legendary S90 and modify them with a file, in order to make a budget solution that will be the envy of everyone. After monitoring various flea markets for a long time, I finally bought a 35AC-212 “Radio Engineering” S90 from 1981 on one speaker (my peers;)).
The condition on the outside is a solid 4, no one has tampered with the inside with crooked paws. There was only one minus - the bass driver from one speaker was killed, which was honestly reported to me, and I really didn’t like the fact that both woofers were painted silver (it’s good that the paint is not deep paint, i.e. the mass of the diffuser has not increased much).
For 1000 rub. I bought a set for creativity.
We will improve it.
Oh, I feel strong polemics between supporters of improvements to Soviet acoustics and supporters of burying it completely and without turning.
I immediately apologize for the quality of the photos, because at the time of revision, and even now I do not have a digital camera other than a phone.

Let's climb inside

After listening, I decided to disassemble each speaker to see if the insides matched the speakers' passports. As it turned out, the HF quality is 10GD-35, MF 15GD-11A, and LF 35GD (something) I don’t remember, but with a rubber suspension that hasn’t dried out.
The first thing I did was rewind the woofer.
Restoring the speaker was no problem for me, since I did this very often in my youth for little money. Unfortunately, I didn’t have a mandrel of a suitable diameter, but I have a need for invention and I went to the nearest construction store with a caliper in my pocket. As a mandrel, I bought some kind of plumbing pipe for what seemed like 20 rubles. I sawed it lengthwise (this is necessary since after winding it would be practically impossible to remove the coil from the mandrel).
Let's add another 20 minutes for winding and centering and a day to dry the speaker. That's it, the speaker started playing without any extraneous sounds and as if untouched.

Let's start with the tweeters

After listening to the result and reading the great Internet, I began to think further about how to make the sound even better. Basically, all types of modifications come down to replacing the HF, replacing the midrange and damping the body.
The highs really don't sound very good. There are unpleasant overtones in the high frequencies and a lack of ringing in the midrange. The HF section uses speakers with domes made of some kind of plastic/polyethylene. For comparison, I installed 10 W speakers with silk domes, the high-frequency sound became much more transparent and the overtones that simply grated the ear disappeared. As a result, these rootless speakers for about 500 rubles per pair remained in them. I bought them a long time ago and the markings on them are unreadable, and I don’t remember what was written on the price tag. You can also use 10GDV speakers with silk domes.

I note that I first made one speaker and compared the sound from the test discs with the sound of the original speaker. After listening, I decide to leave the rework or return everything back. Everything was done according to my favorite ear, which never seemed to let me down.

Refinement of the body

Next I decided to work on the low frequencies, i.e. modification of the body. Batting was bought for ridiculous money - 38 rubles per meter of length and 2-something meters wide. Having also looked at the manufactured filters, I heeded the advice to change all the wiring in the speakers.
I removed all the speakers from the speakers. I took out the filter and switches. The wires can be safely cut since they will need to be replaced anyway.
Next, I cut out the required piece of batting, borrowed a furniture stapler from a friend, and began sheathing them inside in 2 layers.

We put the bass reflex pipe on the sealant and also cover it with batting.

The next thing you need to do is modify the filter.

The filter circuit is simple

I turned off the switches completely, since they are completely unnecessary. We remove unnecessary elements from the filter board.
We replace all the thin conductors in the filter with normal copper wire.
Here is the filter before modification.

And this is a copper wire about 4 squares used for almost all connections

As a result, rebuilt with removed dividers and regulators


Next we install it in the body and cover it with batting.
We also cover the entire midrange box from the outside with batting.

midrange link

In principle, after such modifications, the sound changed for the better, the bass became clearer, the upper frequencies became “more transparent” and “lighter”, but I still didn’t like the mids, the upper mids were not enough. There was not enough ringing in the vocals.
After rummaging through my supplies I found two 4GD-8Es in excellent condition. I installed one speaker and spent a long time comparing the results. I liked the result. In one blues recording I heard brushes hitting the main drum. Before that I didn't distinguish them.
But these speakers did not last long in acoustics.
After listening to the modified speakers for a week, I came to the conclusion that the sound began to tire me.
Probably all this is caused by the fact that the 4GD-8E dynamic heads have a very high quality factor and, in a closed box, have a very jagged frequency response. Unfortunately, there is no normal microphone to take measurements. Yes, the midrange speakers were equipped with a foam pad covering the rear holes in the speakers. The midrange box itself is filled with fluffy “eye” cotton.

On the Internet they often wrote about 5GDSH-5-4 and 6-GDSH-5, about the fact that after installing the PAS they produce excellent midrange frequencies. Walking through neighboring radio stores, I bought a pair of 6-GDSH-5 4 Ohms for 110 rubles. As far as I understand, they are installed in household electronic equipment. I sealed the windows in the diffuser holder basket with thin batting and installed them instead of 15GD-11A, fortunately their installation dimensions are completely the same. There is another way to refine the midrange speakers - impregnating the suspension with mystical guerlain mixed with the blood of the orchestra conductor with acetone and applying a thin layer to the back side of the diffuser. But as far as I understand, this is quite rare and in construction stores they just shrug their shoulders. It would be worth taking for an experiment, because 110 rubles for a pair of new speakers is not a pity.

After all operations, we completely assemble the acoustics and enjoy the new sound. I tested the sound on Sukhoi’s homemade high-fidelity amplifier (I’m afraid that true Hi-Fi connoisseurs will spew rays of diarrhea in my direction). By the way, I also assembled the amplifier myself, with minor modifications to the power supply, and it has been playing for exactly more than a decade, but that’s how it works in the same form as an engineering sample. I connected it all to Sb Live! Playing flac of special discs such as audio doctor. And just wav and flac discs that are specifically recommended for testing the audio path.

Bottom line

Costs 1000 rub. the acoustics themselves
500 RUR HF speakers
110 RUR Midrange speakers
RUB 150 batting, glue, staples, screws and other small items
Total 1760 rub.
What did we get?

Such nice acoustics

What follows is only my opinion and the opinion of my friends who have experienced it.
A friend who owns jbl floorstanding speakers, I don’t remember the model, but they cost about 20,000 for one and a Yamaha receiver, he definitely agreed that after the S90 modifications, his set is being replayed.
I'm completely satisfied with the sound. Walking around different salons with acoustics and listening to them, I understand that such sound is cheaper than 15,000 rubles. You can't buy one speaker.

PS Now they are playing together with Gumel's Simple amplifier and Sukhoi's BB pre-amplifier. Everything is connected to the same sound system SB Live! and works as a front to 4.0 sound for watching movies on a 37" LCD panel. There is more than enough realism in disaster films. I don’t even think about adding a subwoofer.

11-01-2009

Modification of acoustic systems Radiotehnika 35AC-012 (S-90)

Radiotehnika 35AS-012, Radiotehnika S-90, Radiotehnika 35AS-012, Radiotehnika S-90

Currently I am the proud owner of Radiotehnika S-90 speakers.

Consideration of acoustics in normal condition

First, you should specify the full name of the acoustics - 35AC-012. From their number it immediately becomes clear that we are dealing with top-class acoustics, by Soviet standards, that is, with acoustics that have very high characteristics. It should be noted right away that by Soviet standards this was not the best acoustics, but an ordinary ordinary workhorse. There were acoustics that had a more balanced sound, for example the same Cleaver/Corvette 35AC-008.

But as they say, we have what we have. Let's go back a little to the moment of their purchase. I bought them from a friend of mine for $50, when I came to him, when I saw the decorative grilles protecting the sound-emitting heads, I wanted to cry, they were dented and, at that, very cruelly (mainly the grilles of the high-frequency and mid-frequency speakers were damaged). But this didn’t scare me, since what was sold on our market cost at least $100, and the quality of the speakers deserved no more than 3, and in these speakers the speakers looked like 5. In general, I took these speakers to my home. When connecting them to an amplifier the sound was quite decent. But nevertheless, two drawbacks should be noted, 1 of which is inherent in all 35AC-012, and as it turned out, in all its 35AC clones, to one degree or another.

The first of the shortcomings that simply killed me on the spot was an incomprehensible overtone when the woofer was working, very similar to the fact that something was stuck to the speaker from behind, and now it was vibrating, as it turned out later it was a drop of solder that stuck to diffuser from the reverse side. The second drawback was precisely in the mid-frequency dynamics 15GD-11A - according to the old standard and 20GDS-1-8 according to the new one (these speakers came in a large number of modifications, for this reason it is extremely difficult to track which one you have). And again, a small digression in which I will say that the differences in the standards lie in the designation of power, that is, according to the old standard, the rated power of the speaker was indicated, and according to the new standard, the rated power is indicated (from the audio engineering course:

1. The rated power of the speaker is the power of the speaker, when supplied, it operates with harmonic distortion levels not exceeding the permissible
2. Nameplate power (often also called noise): this is the level of power supplied to the speaker at which the level of harmonic distortion is equal to ten times the level at rated power).

An additional division into the frequency ranges of the heads was also introduced, which was now indicated in the name of the speaker, in particular this is the third letter.

So the disadvantage of this speaker is that it often begins to resonate at high volumes and thereby spoils the sound picture, and as you know, the mid-frequency speaker is crucial in the formation of the sound picture.

Let us now consider in order all the speakers that we have in stock:

1)Low frequency - 30GD2, also known as 75GDN-1-4(8):

Purpose - use in closed and phase-inverted remote acoustic systems of household radio equipment of the highest complexity group as a low-frequency link when working indoors. The loudspeaker head is of electrodynamic type, low-frequency, round, with an unshielded magnetic circuit. The diffuser holder is made by injection molding from aluminum alloy. The cone diffuser is made of impregnated paper pulp. The suspension is toroidal-shaped and made of rubber. The centering washer is made of impregnated fabric.

I would also like to add that the speakers have a relatively heavy dome and a rubber surround, which spoils the quality of the bass; it becomes less continuous and booming than speakers with a lighter moving part and a foam surround. But it should be borne in mind that the bass is influenced not only by the design, but also by the acoustic design itself; for this reason, these problems can be eliminated a little and the speaker will play decently. On the other hand, due to the rubber suspension, the speaker turned out to be very reliable and practically indestructible, while the foam suspension soon crumbles due to the presence of sulfur in the air and the speaker requires repair.

Purpose - use in closed and phase-inverted remote acoustic systems of household radio equipment of the 1st and 2nd complexity groups as a mid-frequency link when working indoors. The loudspeaker head is of electrodynamic type, mid-frequency, round, with an unshielded magnetic circuit. The diffuser holder is made by injection molding from aluminum alloy. The conical diffuser and spherical cap are made of impregnated paper pulp. The toroidal-shaped suspension is made of polyurethane foam. The centering washer is made of impregnated fabric.

Here is actually a photo of this miracle of technology:

It is worth saying that at a good volume it significantly distorts the sound, but as practice has shown, this problem is very easily solved and, at that, quite simply.

Purpose - use in closed acoustic systems of household radio equipment of the highest complexity group as a high-frequency link when working indoors. The loudspeaker head is of electrodynamic type, high-frequency, round, with an unshielded magnetic circuit. The mounting flange and acoustic lens are made of plastic. The dome-shaped diaphragm with suspension is made on the basis of polyethylene terephthalate.

In general, they sound good, but the filters are tuned close to the resonant frequencies.

Upon closer examination of the acoustics (especially from the inside), you begin to be horrified by the build quality, for this reason we will begin to refine it. We will refine it according to the simplest possible scheme, without interfering with the filters, since without specialized equipment there is nothing to do there. For anyone interested, here is the acoustics diagram:

Revision 35AS-012

I will describe in order all the stages of improvement that my speakers went through:
1. Disassembly:

• First of all, we take them to a secluded place (meaning a room) in which our experimental subjects will not be accessible to children (if any) and other family members. We lay the speaker system on its back and begin to disassemble it.
• Now remove the decorative covers from all the speakers and put them aside.

Here they are:

Then we take out the speakers. ATTENTION: when unscrewing the bass speaker (the treble and midrange speakers are secured with the same screws as the decorative trim, and the woofer is mounted separately from the trim), be extremely careful, because if the screwdriver comes off, you will disfigure it. Then we use a soldering iron to unsolder the wires connecting the filter and the speakers, and safely hide the speakers in a secluded place.

• We remove the bass reflex cover and take out the bass reflex itself, and this must be done as carefully as possible, since we are working with plastic, and it can easily break. Then we hide these details in a secluded place.
• Now let's take on the regulator/controllers of the HF/MF sections. To dismantle them, you need to remove the decorative plug in the center of the regulator, then unscrew the exposed screw and remove the regulator handle. After this, carefully pry up the remaining plastic lining using two chisels and carefully remove it, then unscrew the 4 screws securing the attenuator itself and now it can be pushed inside the case. We push it out and unsolder it from the filter. We put it aside, in the future you will need to work a little magic on it. By the way, the joint between the attenuator body and the speaker body is generously covered with a viscous sealing substance; I personally reused it when putting it back into place, but you can use sealant or plasticine.
• We take out the cotton wool bags that are supposed to be in your speaker system and set them aside.
• We dismantle the panel with filters; it is screwed to the body with screws, having previously unsoldered the wires from the output at the back of the speaker system. We put it aside, since we will spend a lot of time working with them.
• Finally, remove the terminal panel from the back cover of the speaker and set it aside.

It seems like a lot of work has been done, but in reality it is just a drop in the ocean. More interesting and time-consuming work lies ahead.

2. Restoration of appearance:

For this purpose, we take the grilles and covers from the speakers that we removed earlier, level them, carefully sand them, degrease them and paint them in several layers with car paint (which is in spray cans) several times and leave them to dry. I’ll make a reservation right away that I restored the grilles only for the reason that I have a small child who can damage the speakers, otherwise the simplest solution would be to abandon the grilles as such, since they only introduce disadvantages into the sound, think for yourself.

3. Refinement of the speaker system housing:

Here everything is actually very simple, and is carried out in several stages:

• If desired, the body can be strengthened. What will this give us? Clearer and smoother bass, since the cabinet panels will vibrate less and, accordingly, will introduce less overtones into the bass component of the sound. How to do it? This is purely a matter for everyone, since as many people there are as many decisions. In general, it all consists of installing spacers, installing additional corners at the joints of the walls of the speaker system, and installing stiffeners on the walls of the speaker. Personally, I limited myself to gluing in additional corners at the joints. You can also tightly glue all joints. Unfortunately, I can’t show you a photo since the entire speaker system is already damped with foam rubber.
• Sealing all joints and seams. It is done very simply using various materials. For example, I used plumbing sealant. The procedure is simple: cover the joints with sealant and carefully smear it with your finger, thereby tightly sealing any cracks.
• At a hardware store we buy foam rubber 10mm thick (personally, I chose this thickness, don’t take too much as it will suffocate the body) and glue it to all the walls except the front. In this way we dampen the body, thereby increasing its virtual volume.

To do this, we buy terminal blocks with gold-plated universal-type connectors in the store. Since the S-90 terminal block itself is large, and the new ones are small, we remove the connectors from the terminal blocks and install them on the body of the S-90 terminal block. Then we lubricate the installation area with sealant (don’t be sorry, wipe off the excess later) and put it all in place, tighten the screws. Here's a photo of what you should get:

5. Let’s move on to reworking and replacing the filter:

• First of all, carefully examine the filter, pay attention to the fastening of the parts, since often the inductors were fastened with metal screws, which immediately disrupts the filter settings.
• If there were problems with the fastener, complete it by eliminating metal parts from the fastener. There are also cases of assembling the filter on a metal plate, then transfer the filter to a plywood panel.
• We pick up a piece of paper, a pen, and carefully redraw all the elements of the circuit, restoring, so to speak, the filter circuit itself, because the parameters of the speakers were wrong and for this reason the filter circuit could have been changed at the factory. By the way, we exclude the attenuator from the circuit, it simply spoils the sound.
• Now we take a soldering iron (preferably 100 watts) and disassemble the filter, or rather, simply remove all the jumpers that were installed from the factory.
• Now we are assembling the filter, instead of jumpers we will now use a cable made of oxygen-free copper with a cross-section of 4 mm 2, the cable can be bought at any car audio store. It should also be noted that you should not buy a very expensive cable, as the changes in sound quality will be insignificant, but the costs are simply colossal.
• After assembling the filter, we solder the wires that will go to the speakers based on: for the low-frequency link 4 mm 2, for the mid-frequency link 2.5 mm 2, for the high-frequency link 2 mm 2.
• We put the filter in place, and then solder the terminal blocks to it (observe the polarity, otherwise you will lose the sound picture).
• The very last step is to run the wires to the speakers, secure them and cover the filter with foam.

You'll end up with something similar to these photos:

6. Attenuator installation:

• We remove all resistance from it.
• Let's put it in its place.
• We carefully seal it.
• Additionally, we cover it with foam rubber (I only covered it on the front wall)
• We install all the decorative panels completely.

7. Installation of the bass reflex:

Everything is simple here, we put it back on the sealant, carefully make sure that it is not pinched anywhere by the foam rubber, as this will throw off its setting.

8. Reinstall the bass reflex cover:

We install it the same way as we removed it, just install it with sealant and new screws, since the panel itself often rattles in the bass. Seal the joint between the panel and the bass reflex well.

9. We proceed to installing the dynamic heads in place:

• A) Install the HF head:

1) We remove the travesty of the seal that is on it (some kind of rubber or cardboard at the back).
2) Cut out a new seal; a mouse pad, in particular a black porous base, is perfect.
3) Solder the wires to the speaker and install it in place.
4) Put the decorative trim (grid if desired) in place and tighten it tightly with the screws.

• B) Install the midrange head:

1) We make a cylinder from foam rubber, such a size that our box will fit into it. We place this cylinder inside the speaker and pass a cable through it, which we take out.

2) Pass the wire through the box (most likely you will have to widen the hole), then put the box in place, adjust the length of the wire and seal the hole into which the wire is passed.
3) Solder the wires to the speaker.
4) Now the crucial stage is damping the mid-frequency head. To do this, we sew a cylinder of foam rubber, such a size that it fits tightly onto the speaker frame and covers all the windows.

5) Fill the box with cotton wool, having previously fluffed it.
6) Put the dynamic head, grille (optional) and frame in place and tighten it.

1) First, put back the bags of cotton wool that were removed during disassembly of the speakers. Solder the wires to the head. I tied the wires that are soldered to the head to the frame so that they do not hit the diffuser, because there is a possibility that when you put the speaker in place, the wires will bend and fall into the window of the diffuser holder.

2) We make a gasket from a porous material, for example
Apply window seal and carefully place the speaker in place.
3) Tighten the mounting screws. Do not apply much force, then the speaker will be spring-loaded by the gasket and this will reduce the energy of vibrations transmitted to the body.
4) Put the grille (optional) and decorative trim in place. If you do install a grille, then I advise you to cut out small triangles from foam rubber and place them on the speaker at the place where it is attached; this will eliminate the vibrations of the grille, and therefore eliminate overtones at high volumes.

I came up with this solution a long time ago, look at the photos for more details:

Conclusion:

After the modification, all the listeners (there were not many of them, about five people, but I asked for the most honest information from them) noted more delicate and soft bass, a much cleaner middle, the highs remained practically unchanged (it seemed to me that they became a little cleaner). Also, the acoustics began to calmly reach higher volumes.

In conclusion, I would like to say that the proposed method is the cheapest, simplest and most accessible. All components, of course, can be modified or changed several times. For example, instead of foam rubber, you can use felt (natural), this, in theory, will give better results than foam rubber; it is also a good idea to use vibrating mastics. Many people advise replacing the 15GD-11A with a 5GDSH broadband receiver; in my opinion this is a bad idea, but that’s everyone’s business. 10GD-35 - it is recommended to treat it with a notch filter, 15GD-11A should be modified based on halves of a tennis ball (by the way, the idea is quite interesting, I haven’t done it myself since I don’t have such speakers in stock).

At the moment, there are two 6GD-13 speakers available (considered the best in Soviet times), so perhaps I’ll write about what happened sooner rather than later.

And perhaps lastly, I’ll say that if you’re a fan of MP3 music and you have inexpensive source equipment, then maybe you shouldn’t bother so much, although I heard differences when extracting sound from a Creative Sound blaster 24 bit sound card. It should also be noted that the room in which you listen to music has a huge impact on the sound.

Good luck to everyone in your improvements and implementation of your ideas!

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They are distinguished by an expanded range of reproduced frequencies, the introduction of an indication of electrical overload of loudspeakers and a new appearance. The recommended power of a high-quality household amplifier is 20-90 W. The preferred installation option is floor-mounted.

A distinctive feature of the acoustic system is the use of a loudspeaker with magnetic fluid “MANGO” as a mid-frequency link, which made it possible to increase the rated power of the loudspeaker and the speaker as a whole.

Specifications:Сг3.843.050 TU.

Shape of the frequency response of sound pressure measured along the acoustic axis: a) , b) ,

Specifications:

Specifications	Meaning
Reproducible frequency range in free field conditions, Hz:
	25...25000
,	25...25000
Uneven frequency response of sound pressure, dB, at the lower limit frequency of the reproduced frequency range relative to the average sound pressure level:
	-15
,	-14
Uneven frequency response of sound pressure, dB, in the frequency range 100...8000 Hz relative to the average sound pressure level:
	±4
,	±4
Level of characteristic sensitivity (characteristic sensitivity), dB, not less:
	85 (0,338)
,	89 (0,56)
Directional characteristics of the speaker, dB, determined by the deviation of the frequency response of sound pressure, measured at angles of 25 ± 5° in the horizontal plane and vertical plane, from the frequency response measured along the acoustic axis of the speaker (0°):
:
in the vertical plane	±8
in the horizontal plane	±6
, :
in the vertical plane	+ 2
	-4
in the horizontal plane	+4
	-3
Harmonic distortion of speakers, %, determined by the total characteristic harmonic coefficient at an average sound pressure level of 90 dB at frequencies, Hz, no more than:
250…1000	2
1000...2000	1,5
2000...6300	1
Nominal electrical resistance (nominal value of total electrical resistance), Ohm:
	4/8
,	8
	8
Minimum value of total electrical resistance, Ohm:
	3,2/7,6
,	7,6
	7,0
Maximum noise (nameplate) power, W:
,	90
	100
Maximum short-term power, W:
,	600
Type of low-frequency acoustic design	bass reflex
Weight, kg	23
Dimensions, mm	360x710x285

Design Features:

The enclosures of all modifications of the speakers are made in the form of a rectangular non-dismountable box made of chipboard veneered with valuable wood veneer. The thickness of the case walls is 16 mm, the front panel is plywood 22 mm thick. At the joints of the housing walls, elements are installed on the inside that increase the strength and rigidity of the housing.

The following sets of heads are used in acoustic systems:

• : ; ; ;
• ; : ; ; ;
• : ; ; .

The heads are produced by Radiotekhnika software.

The heads that make up the speakers are each framed with decorative blackened overlays, made by stamping from aluminum sheet, with four mounting holes. The midrange head is isolated on the inside from the total volume of the housing by a special plastic casing in the shape of a truncated cone. The LF head is located on the front panel along a vertical axis, and the MF and HF heads are shifted relative to this axis to the left or right. On the front panel there are also knobs for the midrange and treble level controls, and in the lower part there is a plastic overlay panel with a nameplate and a rectangular hole (100x80 mm), which is the bass reflex output. The nameplate shows frequency response curves corresponding to various positions of the level controls, as well as the name of the speaker and the manufacturer's logo. In addition, the front panel has special plastic bushings for attaching a decorative frame with fabric.

Crossover frequencies provided by filters: between low- and mid-frequency heads - 750±50 Hz, between mid- and high-frequency heads - 5000±500 Hz.

The design of the filters and the overload indication unit uses resistors such as BC, MLT, SPZ-38B, S5-35V, PPB, capacitors such as MBGO-2, K50-12, K75-I and inductors on plastic cast frames.

The removable decorative frame included in the kit is covered with knitted fabric with high acoustic transparency.

The delivery set includes four plastic feet, which can be attached to the base of the case if necessary.