Speakers S90: specifications, diagram. Do-it-yourself speakers

In 1978, the S90 speakers, 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 designed at the Riga Radio Engineering Production Association, at the Orbita Design Bureau.

Appearance

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

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

Purpose

Much can be said about the scope of application. Speakers "Radio engineering S90" had to reproduce high-quality music and speech programs in a domestic hospital. Of course, they were not in every family, and those who lived in a house where they were not were probably happy. Where they were, on any floor and in any entrance of the apartment building, chandeliers swayed, and crystal rang in sideboards.

One such speaker system was enough, where the Radio Engineering S90 speakers did not even work at full volume. The entire five-story building was familiar with the musical tastes of the happy owner. The neighbors lived especially well if he used a Corvette-type amplifier. The Soviet S90 speakers were quite expensive - 300 rubles for two pieces, so they were most often 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 is the S90 speakers.

Characteristics

All people listening to music wanted to buy this speaker system, because it really was a breakthrough in real sound. In those days, literally a few had imported equipment, and the sound quality of Soviet tape recorders did not suit almost anyone.

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

Quality

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

In any case, the S90 loudspeakers were the first system made in the USSR that met the requirements of international documents for Hi-Fi category 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 floorstanding speaker system equipped with a phase inverter, 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 acoustic 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.

The speakers in the S90 speakers: low-frequency 75 GDN-1-4 with a diffuser diameter of 220 mm, mid-frequency 20 GDS-1-8 - 105 mm, and high-frequency 6 GDV-6-16 with a membrane of 26 mm. The case is rectangular, non-separable, finishing - veneer. The wall thickness is 16 mm, on the front panel - plywood 22 mm. The joints on the walls are rigidly reinforced. On the heads there are 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 black metal mesh. Inside to suppress resonances and sound pressure - a mat of technical cotton wool and gauze.

Inside

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

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

Included

It should be noted that the speakers standing directly on the floor gave a 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 speaker. They could be attached to the base of the case. 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 were perfectly combined with any kind of household radio equipment that existed at that time. The author of the development is Roland Paulovich Kerno, who is still legendary among people close to acoustics. He began to work at this enterprise from the end of the 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 made repairs to the S90 speakers, and then the rumble at low frequencies, which certainly arose at high volume, was removed, the unpleasant clatter, which is inherent in the high-frequency head 6GDV-1-16, was removed (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 give approximately the same deep bass. For example, in the Xoro HSD 6040 home theater speaker system. But the price of these products is incomparable. However, now the S90 speakers are also expensive, but still much less.

For repair: weak points

After so many years, it makes sense to replace the high-frequency and mid-frequency speakers. You can simply rewind the low-frequency one; this procedure, which is not too time-consuming, 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 can’t turn it up to full volume, there is a danger of breaking the woofer altogether. Phase inverters 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 that you have to make yourself.

Many music lovers from the cohort that were born with a soldering iron modify and improve their favorite acoustic systems of the Radio Engineering 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 from two layers of high-quality, but inexpensive batting, glue the necessary places with felt, even restore the case if it has undergone many moves over a long life and has been beaten or bent (the wire grilles on the speakers are convex, so it’s no wonder ). Skilled music lovers reworked and soldered almost everything, as a result they got 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 power copper wire has proven itself to connect the amplifier to speakers. The cross section must be chosen at least one and a half square millimeters, and the farther the speakers are from the amplifier, the thicker the wire should be.

Very carefully you need to consider the suspensions on the speaker cones - mid-range and low-frequency. This is rubber along its edge, on which the diffuser is glued. This rubber should be "native", from the manufacturer. Otherwise, the diffuser will not attach tightly. The old and good suspension is covered with silicone grease, which is sold in special radio stores.

Accessories

First of all, it is an amplifier. The Soviet ones have already worked out all their expiration dates, but if you have the skills to own a soldering iron, this is not scary. An imported amplifier will greatly increase the cost of the already expensive S90 equipment, which has yet to be repaired. A too modern and expensive amplifier will not give anything to these speakers, since the sound quality does not depend on it, but on the speaker system.

Nothing will sound much better. It doesn't matter what amplifier, even the tube "Surf-50-UM", will do. You need to look not at the date of manufacture, but at the power. Stronger than 50 watts per channel is useless, and without that the walls will dance, and the floor will shake. But if you don't feel sorry for the neighbors, it's the master's business.

Result after repair

If you make a detailed repair of the S90 speakers and test their performance carefully, you can achieve results that are almost unsurpassed. Even the jbl floorstanding speakers of this year's model, for which you have to pay almost 50,000 rubles, and even together with the Yamaha amplifier, do not give such a beautiful sound.

Refinement inside and out

When the owner of "Radio engineering" of 1981 release has the idea to "finish with a file" the old speakers, he is unlikely to expect such a result. True, almost everything will have to be redone. Modify the body, remove all the gaps with epoxy, change the cotton wool and gauze to batting, and also completely solder the wiring in the columns.

Dismantle the speakers, replace two in any case, and the third can simply be rewound. Sheathing with batting can be done using a furniture stapler. Glue the phase inverter pipe to 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 certainly make the sound better. But it will become ideal only after a long setup. The bass acquires the missing clarity, the tops become more airy, more transparent. But with medium frequencies you will have to fight with perseverance. In the center we hear most often the vocals. So he clearly lacks voice. Having tried several other, "non-native" speakers, one will still be successful sooner or later.

You won't need to master the main way to refine mid-range speakers - magic: they say that if you impregnate the suspension with a magical sealant, consisting of two parts of the conductor's blood and one part of acetone, then you can not change the speaker. However, in hardware stores they usually shrug their hands.

In total, the financial costs of a complete repair of the S90 speakers: badly worn acoustics (but still change everything, except for the case) can be purchased for about a thousand rubles; tweeters - 500 rubles; midrange speakers - 110 rubles; batting - 150 rubles; glue, stapler staples (you can ask a neighbor for a stapler), screws and other small things - it's hard to calculate exactly, but it's nothing. This means that this excellent acoustics will cost a resourceful and skillful music lover less than two thousand rubles.

Radiotehnika 35AC-012, Radiotehnika S-90, Radio engineering 35AC-012, Radio engineering S-90

At the moment I am the happy owner of the Radiotehnika S-90 speakers.

Consideration of acoustics in normal condition

To begin with, the full name of acoustics should be specified - 35AC-012. From their issue, it immediately becomes clear that we are dealing with high-class acoustics, by Soviet standards, that is, acoustics with very high characteristics. It should be noted right away that by Soviet standards it was not the best acoustics, but an ordinary ordinary workhorse. There were acoustics that had a more balanced sound, for example, the same Cleavers / Corvettes 35AC-008.

But as they say, we have what we have. Let's go back a little to the moment of their purchase. I took them from my friend for $ 50, when I came to him, at the sight of the decorative grilles protecting the sound-emitting heads, I wanted to cry, they were dented and very cruelly at that (mainly the grilles of the tweeter and mid-range speaker suffered). But this did not frighten 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 at 5. In general, I took these speakers to my home. When connected to an amplifier, the sound was quite decent. Nevertheless, two shortcomings should be noted, one of which is inherent in all 35AC-012, and, as it turned out, all of its 35AC clones, to one degree or another.

The first of the shortcomings that just killed me on the spot is an incomprehensible overtone during the operation of the woofer, very similar to the fact that something was stuck to the speaker at the back, and now this is something vibrating, as it turned out later, it was a drop of solder that stuck to diffuser on the back. 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 for you to track which one). And again, a small digression, in which I will say that the differences in the standards are 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, nameplate power is indicated (from the sound engineering course:

The rated power of the speaker is such a power of the speaker, when summed up, it works with harmonic distortion levels not higher than the permissible
Passport power (often also called noise power): 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 starts to resonate at high volume and thereby spoils the sound picture, and as you know, the midrange speaker is crucial in shaping the sound picture.

Consider now in order all the speakers that we have available:

1)Low-frequency - 30GD2, aka 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. Loudspeaker head of electrodynamic type, low-frequency, round, with unshielded magnetic circuit. The diffuser holder is made of die-cast aluminum alloy. The conical diffuser is made of impregnated paper pulp. Suspension - torroidal shape - made of rubber. The centering washer is made of impregnated fabric.

I also want to add that the speakers have a relatively heavy dome and a rubber surround is used, which spoils the quality of the bass, it becomes more solid and booming than the speakers with a lighter mass of the moving part and foam rubber suspension. But it should be borne in mind that the bass is affected not only by the design, but also by the acoustic design itself, for this reason, these troubles can be slightly eliminated 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 unkillable, and the foam rubber suspension soon crumbles due to the presence of sulfur in the air and the speaker needs to be repaired.

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. Loudspeaker driver of electrodynamic type, midrange, round, with unshielded magnetic circuit. The diffuser holder is made of die-cast aluminum alloy. The conical diffuser and the spherical cap are made of impregnated paper pulp. Torroidal suspension - made of polyurethane foam. The centering washer is made of impregnated fabric.

Here is actually a photo of this miracle of technology:

It should be said that at a good volume it decently distorts the sound, but as practice has shown, this problem is very easily solved and, moreover, very simply.

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

In general, they sound good, only the filter tuning is close to 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. 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 those who are interested, here is the acoustics diagram:

Refinement 35AC-012

I will describe in order all the stages of improvement that my columns 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 available to children (if any) and other family members. We lay the speaker system on our back and begin to disassemble it.
Now remove the decorative trims from all the speakers and put them aside.

Here they are:

Then we get the speakers. ATTENTION When unscrewing the bass speaker (the tweeter and midrange speaker are attached with the same screws as the decorative trim, and the woofer is attached separately from the trim), be extremely careful, because if a screwdriver comes off, you will disfigure it. Then we solder the wires connecting the filter and the speakers with a soldering iron, and boldly hide the speakers in a secluded place.

We remove the cover of the phase inverter and pull out the phase inverter 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 we take on the regulator / regulators of the HF / MF links. To dismantle them, it is necessary to remove the decorative plug in the center of the regulator, then unscrew the opened screw and remove the regulator knob. After that, carefully pry off the remaining plastic lining with the help of two chisels and carefully remove it, then unscrew the 4 screws securing the attenuator itself and now it can be pushed out into the case. We push it out and solder it from the filter. We put it aside, in the future it will be necessary to conjure a little over it. By the way, the junction of the attenuator housing and the speaker housing is abundantly covered with a sealing viscous substance, I personally used it again when I assembled it in place, but you can use sealant or plasticine.
We take out the bags of cotton wool, which, in theory, lie in your speaker system and set aside.
We dismantle the panel with filters, it is screwed to the body, having previously unsoldered the wires from the output at the back of the speaker system. Putting it aside, as we will spend a lot of time working with them.
Finally, remove the panel with terminals from the rear cover of the speaker and set it aside.

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

2. Restore appearance:

For this purpose, we take the gratings and speaker covers we removed earlier, level them, carefully sand, degrease and paint several layers of automotive paint (which is in spray cans) several times and leave 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 easiest solution would be to abandon the grilles as such, since they only bring minuses to the sound, think for yourself.

3. Refinement of the speaker cabinet:

It's actually very simple, and is carried out in several stages:

If desired, the body can be strengthened. What will it give us? More precise and even bass, since the body panels will vibrate less and, accordingly, will introduce less overtones into the bass component of the sound. How to do it? This is purely everyone's business, because as many people as there are so many decisions. In general, everything consists in installing spacers, installing additional corners at the joints of the acoustic system walls, installing stiffeners on the speaker walls. Personally, I limited myself to pasting additional corners at the joints. You can also glue all the joints tightly. Unfortunately, I can’t show a photo, since the entire acoustic system is already dampened with foam rubber.
Sealing all joints and seams. It is carried out very simply with the help of various materials. For example, I used plumbing sealant. The procedure is simple: we cover the joints with sealant and gently smear it with your finger, thereby tightly sealing possible gaps.
In a hardware store we buy foam rubber 10 mm thick (I personally chose this thickness, do not take too much as you will strangle the case) and glue it to all walls except the front one with glue. Thus, we dampen the body, thereby increasing its virtual volume.

To do this, we buy terminal blocks with gold-plated connectors of a universal type in the store. Since the S-90 terminal block itself is large, and the new ones are small, we dismantle the connectors from the terminal blocks and install them on the body from the S-90 terminal block. After that, we lubricate the installation place with sealant (do not be sorry, then wipe off the excess) and put it all in place, tighten the screws. Here is a photo of what you should have:

5. We proceed to the alteration and installation of the filter in place:

First of all, carefully examine the filter, pay attention to the fasteners of parts, since inductors were often fastened with metal screws, which immediately knocks down the filter setting.
If there were problems in fasteners, bring it to the end by excluding metal parts from fasteners. There are also cases of assembling the filter on a metal plate, then transfer the filter to a plywood panel.
We take a leaf, a pen in our hands and carefully redraw all the elements of the circuit, restoring the filter circuit itself, so to speak, because the parameters of the speakers varied and for this reason the filter circuit could be changed at the factory. By the way, we exclude the attenuator from the circuit, it just spoils the sound.
Now we pick up 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 an oxygen-free copper cable 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 take a very expensive cable, as changes in sound quality will be insignificant, but the costs are simply enormous.
After assembling the filter, we solder the wires that will go to the speakers based on: for the LF link 4 mm 2, for the MF link 2.5 mm 2, for the HF link 2 mm 2.
We put the filter in place, after which we 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, fix them and cover the filter with foam rubber.

You will get something similar to these photos:

6. Attenuator setting:

We remove all resistance from it.
We put it in its place.
We seal carefully.
Additionally, we close it with foam rubber (I closed it only on the front wall)
We install all the decorative panels to the end.

7. Installation of a phase inverter:

Everything is simple here, we put it back on the sealant, we carefully monitor that it is not pinched anywhere with foam rubber, as this will knock down its setting.

8. Install the overlay on the phase inverter:

We put it in the same way as it was removed, just put it on the sealant and on new screws, since the panel itself often rattles on the bass. Seal well the joint between the panel and the phase inverter.

9. Let's start installing the dynamic heads in place:

A) Install the HF head:

1) We remove that parody of the sealant that stands on it (some kind of felting gum, felting cardboard, is behind it).
2) We cut out a new seal, a mouse pad is perfect, in particular a black porous base.
3) Solder the wires to the speaker and install it in place.
4) We put in place a decorative overlay (grille if desired) and tighten it tightly with screws.

B) Install the midrange head:

1) We make a cylinder from foam rubber, of such a size that our box fits into it. We put this cylinder inside the column and pass a cable through it, which we bring out.

2) We pass the wire through the box (most likely we will have to expand the hole), after which we 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 the damping of the mid-frequency head. To do this, we sew a cylinder of foam rubber, of such a size that it fits tightly on the speaker frame and closes all the windows.

5) We fill the box with cotton wool, after fluffing it up.
6) We put the dynamic head, grille (optional) and frame in place and twist.

1) First, put back the bags with cotton wool that were removed during the 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 diffuser holder window.

2) We make a gasket from a porous material, for example
apply window sealant and carefully place the speaker in place.
3) Tighten the fixing screws. Do not apply great efforts, then the speaker will be spring-loaded with a gasket and this will reduce the energy of vibrations transmitted to the case.
4) We put in place the grate (optional) and the decorative trim. If you nevertheless put a grate, then I advise you to cut out small triangles from the foam rubber and put it on the speaker at the place of its attachment, this will eliminate the vibration of the grate, and therefore remove the overtones at high volume.

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

Conclusion:

After the revision, all the listeners (there were not many of them, five people, but I asked for the most honest information from them) noted more gentle and soft basses, a much cleaner middle, the tops remained practically unchanged (it seemed to me that they became a little cleaner). Also, the acoustics began to quietly take 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 still be repeatedly modified or changed. For example, instead of foam rubber, you can use felt (natural), which, in theory, will give better results than foam rubber, it is also a good idea to use vibromastics. Many advise replacing 15GD-11A with a 5GDSH broadband, for me this is a bad idea, but this is everyone's business. 10GD-35 - it is advised to treat with a notch filter, 15GD-11A to modify on the basis of halves from a tennis ball (by the way, the idea is quite interesting, I didn’t do it myself because I don’t have such speakers in stock).

At the moment, there are two 6GD-13 speakers available (they were considered the best in Soviet times), so maybe I’ll unsubscribe as soon as possible what happened.

And perhaps in the end I’ll say that if you are 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 the music is listened to is of great importance to the sound.

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Modernization of the S-90 speakers by replacing standard cases with a labyrinth design of woofers

Labyrinth design upgrade S-90 by filling the squares with cotton wool and sticker on the inner surface of the woolen blanket
At first, only the frontal knees of the labyrinth were covered with wool, then the side surfaces too.
Finished labyrinth S-90 with wool-pasted inner surfaces

Alteration of the most famous speakers of the USSR Radio engineering S-90

Alexander Rogozhin came up with a know-how on how to translate the most well-known to most Russian-speaking people the speakers of Radio Engineering S-90 into labyrinth cases. The article is devoted to the most massive and for more than 20 years considered the standard acoustics of the Soviet period, which in its first generation was called 35AC-1. And Rogozhin proposes to make columns with the name "Cheap, loud and super-bass" out of 35AS-1 (Radio engineering S-90)!

Ode to speakers Radio engineering S-90 (35AC-1)

There is no such person who speaks Russian, Ukrainian, Belarusian, who at least once in his life did not hear the famous Soviet speakers Radiotekhnika S-90, or did not have on the mezzanine, in the closet, at home or on the hacienda one of their modifications produced in over 30 years. You can think anything about their sound, appearance, rubber speakers, but in fact these are the MOST common "People's" speakers in the expanses of the former USSR. They still work in tens of thousands in the systems of music lovers, who feel sorry for throwing them away. compared to the branded "remake" they play very, very worthy.

If a person has a choice on which speakers to listen to music: with bass, loudly, and for ridiculous money, then despite all the disadvantages of Radio Engineering S-90, they have practically no competitors, and before they were even more so. In the late USSR, in addition to the S-90 speakers, of course, “clones” appeared, torn off from the best foreign samples, for example, Elektronika 100AC063 or 75AC-063. But they were very expensive and not widely used, they could not compete in popularity with the S-90 acoustics. Getting three full-fledged bands from any other speakers with the same power as the S-90, a 10-inch woofer and almost for nothing was impossible in principle. Now this is even more relevant.

Tens of thousands of these speakers are still working in the rooms of young and not very people who do not have the opportunity to carry out complex projects on expensive imported dynamic heads. For obvious reasons, many of our compatriots are in no hurry to abandon the Radio Engineering S-90 acoustics. They are not eager to run to the store and buy beautiful branded speakers, which for the most part differ from the S-90 only in appearance, which often cannot be said about their sound.

Nevertheless, we all love to listen to music, everyone is in a good mood when you want to turn it on “to its fullest”. Everyone loves high-quality bass, without which almost any music loses its foundation and most of its emotions. Many styles of music without bass are generally impossible to listen to, because. without it, the lion's share of important musical information is lost. The soul asks WOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOL! And the low frequencies are actually a very thin thing, in order to adequately sound and impress, they ask for large speakers, cabinets and capacities. But even with all this (in large speakers like the S-90), the bass often turns out to be buzzing, drawn out and indistinct, and does not give us the “buzz” that it is supposed to give. We quickly get tired of such a bass and start turning the tone control knobs or switching the equalizer modes on the receiver. And instead of getting pleasure - to get annoyed and think about the imperfection of this mortal world ... Almost all music lovers and owners of this acoustics, in particular, have found themselves in such a situation more than once.

Low frequency problems S-90

The reason that over the past 30 years the owners of the Radio Engineering S-90 acoustics and its numerous modifications have not been satisfied with its sound and are somehow trying to cope with this problem lies in several reasons. The main problem of the S-90 speakers, confirmed by repeated research by specialists, is a mistake made when designing the low-frequency design of the 30GD-2 speaker. Having gone into the series, the error led to the fact that the potential for high-quality reproduction of low frequencies, which was originally incorporated in the Radio Engineering S-90 model and its modifications, is not realized even by 20-30% of the possible ones.

A huge number of owners of the S-90, almost from the moment they appeared on sale in the 80s to the present day, have been trying to improve the low frequencies of these speakers by conjuring with filters, reworking the bass reflex pipes, strengthening their native cases and filling them with anything.

Dear music lovers! I urge you to stop doing nonsense, because. it is absolutely useless ... S-90 speakers from the factory have a case with a volume of only 45 liters - NOT corresponding to the optimal mode of operation of the 30GD-2, 75GDN1-4 speaker installed in it. You can even trim it with the root of rare breeds and glue it on all sides with porous rubber - it will NOT work correctly anyway.

That is, the question of a radical improvement in the operation of these speakers at low frequencies, regrettable as it may seem - the question of replacing the case, rises to its full height.

The task is somewhat complicated by the fact that over 30 years a huge number of modifications of the 35AC-1 speakers with low-frequency speakers 30GD2 / 75GDN1-4 (8), which have a large variation in parameters, have been produced. In the new cases, this problem is largely solved and allows speakers from the earliest releases to the latest ones to feel right. The tuning of the new cabinets is "stretched" and allows NOT to engage in the selection of low-frequency speakers on purpose.

Midrange problemsS-90

Almost all owners of s-90 speakers note nasty overtones and a large uneven return at mid frequencies, which become especially noticeable at medium and high volumes. All grandiose projects for reworking filters by installing expensive imported capacitors in them, replacing wires, resistors, etc. as well as options for gluing halves of a tennis ball onto the diffuser of mid-frequency heads, etc. fail.

The main reason for the unsatisfactory sound at medium frequencies is not the 15GD-11 speaker at all, but its acoustic design. This “glass” that covers the midrange head at the back has a meager volume and is the second mistake made by the engineers who designed the S-90 speakers. Everything is wrong with the “glass” of the mid-frequency head 15GD-11 (20GDS ...), starting from the volume and configuration, ending with the internal design. When replacing the s90 speaker cabinet with the correct one from the point of design of the woofer, the midrange speaker should also be designed accordingly.

Of course, replacing the “minor” regular glass with an acoustic design that is optimal in terms of volume and shape will not make the 15GD11 head a different speaker, but will give it the opportunity to do what it can do initially.

What can you get

As a result, the updated S-90 speakers will sound radically different not only at low, but also at medium frequencies. A large number of attempts to remake S-90 speakers are presented on the Internet in order to "deceive everyone" and turn them into studio monitors. Attempts concern everything, but not the replacement of the main "weak point" - the hull, and most often turn out to be a failure. While keeping the S-90 speaker cabinets intact, to radically change the sound, you need to change the speakers to modern ones or design three-way speakers from scratch, which most music lovers do not dare to do.

I propose to leave the native equipment of the S-90 speakers intact. Their value is in the minimum budget and no matter how clever, proven by decades of operation in the most severe conditions - performance.

There is one thing about these speakers that can be fundamentally improved, which is to “get the most out of its speakers”. To do this, to the native set of speakers and filters, you need to make an acoustically correct case. As a result, you can reach a fundamentally new level of sound quality of these speakers, without spoiling anything.

As a bonus, you can not throw away the old cases and, if necessary, collect the "stock" S-90 back and sell it to any lover of authentic speakers made in the USSR.

Problems of native boxesS-90

The wrong amount of low-frequency design does not give the desired level of pressure on the bass;
A non-optimal bass reflex tuning frequency leads to uneven bass response and poor bass quality;
The type of low-frequency design "phase inverter" in combination with a "tight" speaker on a rubber suspension leads to an extended and monotonous "buzz" at low frequencies, instead of a clear percussive bass;
Phase-inverted acoustic design leads to significant uneven sound pressure at low frequencies in the room, and makes demands on obtaining high power from the amplifier;
The weak walls of the boxes of the S-90 speakers lead to a loss of efficiency at low frequencies and give noticeable overtones when working at high volumes;
Poor sealing of the drawers does not allow even the low-frequency design that the S-90 speakers have in the stock version to work;
The extremely small volume of the cap of the mid-frequency head 15GD11 (20GDS-) leads to the “tightness” of the mid-frequency dynamics;
Suboptimal damping of a small midrange box leads to noticeable overtones and “nasal” in the midrange;
The shape and dimensions of the stock S-90 speaker cabinets require them to be mounted on furniture, which leads to “shaky position” of the speakers, resonance of the furniture at high volumes and, as a result, a deterioration in the sound of low frequencies;
The “low-profile” shape of the speaker cabinets requires them to be mounted on specialized speaker stands, which ultimately increases the cost of the system. Placing the 35AC-1s on the floor results in a lack of high frequencies and an incorrect stage.

Benefits of the new buildings

The design of the low-frequency head is a quarter-wave labyrinth with its radical advantages at low frequencies over a phase inverter (detailed description here);
Optimally calculated frequency and Q-factor tuning of the quarter-wave resonator gives a wide band and an optimal level of low frequencies;
The highest rigidity of the box gives the highest possible efficiency, clean, elastic and biting sound at low frequencies;
Rigid boxing of a large volume of the midrange head gives a lively and open middle and clear vocals;
The location of the midrange and tweeters on the front panel, respecting the distances to the walls of the case according to the "golden section" principle, reduces diffraction phenomena on vocals and high frequencies and makes the sound much more comfortable;
With the new enclosures, the acoustics turns into a classic floor-standing design with midrange and tweeters optimally located in height;
The speakers have narrower and taller fronts than standard S-90s and do not require any kind of stands. The appearance of the speakers is improved many times over.

Small cabinet volume for a woofer. The consequence is the humming of low frequencies.
The phase inverter is designed for a frequency of 20 Hz. The consequence is large bass distortion.
Worthless mid-range speaker. The consequences are disgusting midrange, overtones.
Low resonance frequency of the tweeter. Consequences - "quacking", hissing.
The filter is designed taking into account the previous shortcomings. The consequence is that when modifying any node, the filter must be changed.
The case is not rigid enough and is not "muffled". Consequences - vibrations, overtones, "barrel".
Etc. and so on. …

Learning and laughing

Drinking beer, we reach three truths. There are three ways:

Lightweight and efficient.
Medium difficulty. More shamanism and snobbery. Some sound improvements compared to point 1.
Super complex, time consuming and super efficient. You are actually trying to make new speakers. It all depends on the quality of workmanship and musical flair. If nothing happens, then no one promised you anything.

Attention! Attention! Attention!

When carrying out all work, make sure that the phasing of the speakers is correct. If you have not encountered this yourself - invite a specialist - electronics!
Alteration of the speaker 15 GD - 11A is an irreversible process. In case of inaccuracy, the speaker has one road - to the trash can, and you have another - to the market.

Way one. Lightweight and efficient.

The mids are the main focus. By altering the speaker, we will achieve its operation in piston mode, increase the upper cut-off frequency, remove overtones, increase sensitivity, improve directivity, dampen.
Let's translate the column into the range from 31.5 Hz, instead of 20 Hz. There will be less noise.
We will suppress the resonance of the high-frequency head.
Calm down the overtones of the hull

We buy a Soviet tennis ball in the store. Chinese and others do not fit. They have different material. The ball should be exactly the same as in early childhood for 8 kopecks. In extreme cases, you can take it from friends or in the sports section of tennis. We buy epoxy resin (a little, you can 1 cm cube), glue (Supercement, Mars, Argo, etc. - hard after hardening), a couple of simple pencils, any medical bandage and cotton wool.

Let's get creative. We cut the ball in half along the seam. The seam is visible through the light. It is overlapped and 1 - 2 mm wide. You need to cut in the middle of the seam. I sawed with the Neva blade, having previously made notches on it with a whetstone. After sawing, align the cut line on sandpaper, and process the outer surface of the ball with fine sandpaper. If there are large influxes inside in the area of \u200b\u200bthe seam, then they must also be removed. When working, the ball must be fixed with plasticine on the Mars battery (case from photographic film, jars of fish food, etc., by imagination) at three points. It's enough. Plasticine is removed with sweat or with a dry cloth or rubbing with gasoline. After the surface of the ball is processed, it should not be touched by hands. Grind pencil leads on sandpaper.

Dilute epoxy with double the amount of hardener. Cover the surface of the ball with the thinnest layer. If necessary, excess glue can be removed with newsprint. Sprinkle with graphite, shake off excess. It is necessary to ensure that the white plastic of the ball does not shine through the graphite. If it shines through, then the epoxy layer was small. We must add. After everything turned out, we leave to harden.

We collect the filter at 3 kHz. To do this, we take a 4.7 Mf capacitor and a 0.6 mH inductor. You can take a capacitor from 4 to 7 mF and fit a choke under it. In order not to fill your head with unnecessary formulas, the simplest thing is that the product of the capacitance of the capacitor in microfarads and the inductance of the inductor in mH should be equal to 2.82. Let's say the capacitance of the filter capacitor is 6.6 μF (MBGO and MBM with a permissible deviation from the nominal value of ± 10%), then the coil inductance is 2.82: 6.6 = 0.43 mH, (the winding contains 150 turns of PEV-1 wire 0.8 wound on a frame with a diameter of 22 and a length of 22 mm with a cheek diameter of 44 mm). Based on these data, it is possible to assemble a circuit without an LC meter, since it is not the exact value that is important, but the "capture" of the resonant frequency, which has a certain spread. We mount the capacitor and inductor on a piece of fiberboard and solder one output of the coil to the output of the capacitor. We solder wires 40-50 cm long to the free leads.

We parse the column. We remove the low-frequency speaker, mid-frequency speaker, take out the glass from it, remove the high-frequency speaker, remove the decorative overlay, remove the phase inverter (on some speakers you will have to unscrew the filter). We take half of the dried ball, polish it on the outside with suede or newsprint and glue it over the dust cap of the midrange speaker head with hard glue. It is necessary to ensure that there are no unglued lye between the edge of the ball and the cap and that the ball is glued exactly in the center. We do the same with the second midrange. We leave to dry.

We fasten a home-made filter to the back wall of the speaker (inside) opposite the tweeter. Solder the wires from the filter to the output of the tweeter. Which one does not play a role. We remove the connectors from the rear wall of the speakers and solder the wire coming from the amplifier directly to the filter. From the pipe of the phase inverter we saw off with a hacksaw for metal 10 cm along the center line. We wrap the phase inverter pipe and the glass of the midrange speaker with a layer of gauze and bandage it. It is necessary to check whether they will enter their nests after this procedure. If not included, then reduce the layer of cotton wool with gauze. We check if there is cotton wool and gauze in the glass. Add if little to complete. We dampen the midrange speakers. To do this, we additionally fit their diffuser holders with foam rings made from blanks 10x27x355 mm. the ends of which are glued together with glue "Moment" end-to-end. We glue the bottom and ceiling of the column from the inside with felt (batting, padding polyester, etc.). We wrap the wires with a bandage.

We place the bandage along the wire and twist it, clasping the wire. It is convenient to fix the bandage with threads. We collect the column. We coat with plasticine all the perimeters of all the speakers. It is not worth putting on protective nets, but only on the condition that there are no small children, the wife does not call in with a mop or vacuum cleaner, and that the speakers will not be transported. We turn on the columns. We don't know right. We call friends. Please come with your favorite entries. We listen. Comforting friends with beer. With a sneer, we notice how useful the bucks spent on the purchase of foreign rubbish would be useful to them.

Way two. Medium difficulty.

We do everything that is indicated in path 1, but do not collect the columns.

We will improve the properties of the body and kill overtones and "barrel"
Achieve better signal transmission
Hull sealing. We remove the influence of the body

So let's go. Strengthen the rear wall of the case by placing two rails with a section of 3x2 cm. vertically in full length at a distance of 15-20 cm from each other symmetrically, and attaching them with screws to the back wall. Pre-treat the attachment site with epoxy. It is necessary to take into account the possibility of installing a phase inverter later. Between the back and front walls, we install a spacer rail at the level of the midrange head, taking into account the possibility of installing a glass. We coat all the joints of the walls and corners from the inside with silicone glue such as "Bizon" or plumbing silicone putties. We paste over the entire body inside with felt (batting, synthetic winterizer, etc.). Thicker than 1.5 cm is not worth it, so as not to greatly reduce the internal volume of the case.

We reject all proposals to change 15 GD - 11A to 6 GDSH-5. Ours is already "cool", and such a replacement will lead to a loss of power, a decrease in dynamic range (very dangerous) and you will have to change the filter a lot. So when replacing 15 GD - 11A with 6 GDSH-5 for 35AC - 212, you will have to replace the following parts: L1 - 0.22mH, C2 - 1.0mF, C8 - 0.5mF, L4 - 0.1mH. New parameters are specified. When using 6 GDSH - 5 - 4, you will also have to put additional resistance in the circuit of this head at 4 ohms. Also, the appearance of the column changes. Well, if you really want to, then you can. Further. Remove tone switches. Remove unnecessary resistors R (1, 2, 4, 5, 7, 8, 9, 11, 12). We replace the wires on the filter installation with a copper wire with a diameter of 1.2 mm. We replace the wires going from the speakers to the filter with more travel ones. On a low-frequency speaker - stranded - with a cross section of 2.5 - 3 mm square, on a mid-frequency speaker - 2.5 mm square. On high-frequency - 2 mm sq. - single core. All wires are soldered to the filter directly, and not through the previous speakers. The filter is installed at the bottom of the column. All wires are laid under a layer of felt. On the side walls.

The filter controls are removable. We make wooden (chipboard, plywood) plugs in their place according to the thickness of the body. We pour them on epoxy and grind them. We cover the front panel with self-adhesive wood-like film to match the veneer of the speakers. Installing speakers. Low-frequency and mid-frequency through rubber pads. Suitable rubber from window insulation, thin rubber medical hoses, silicone hoses (worse). We process the installed speakers around the perimeter with plasticine or non-hardening window putty (it resembles a piece of laundry soap and is cheap). Checking the sound. We're just balding. Pushing back all sorts of "Pioner", "Technics", JAMO and ...

Way three. Super complex, time consuming and super efficient.

It's good to have the following instruments: an oscilloscope, an audio frequency generator, a digital multimeter, an LC meter. A person who does not repair and assemble at home - of course, does not have all this, but there is a way out - go to the workshop and ask to measure what you need, taking filters, heads, etc. with you. If they ask for a fee for this, then it is purely symbolic. You can even order filters. This, of course, will be more expensive. Let's start. We take as a basis 35AC-212 with dimensions 710x360x285. It is desirable that the case be plywood, a woofer with a rubber suspension, a tweeter with a fiberglass dome. We understand everything. We no longer need a midrange speaker. The case must be increased for a low-frequency speaker with a rubber suspension up to 100 liters. If the suspension is polyurethane foam, then up to 120-130 liters. Our body is 70 liters.

There are two options:

Remove the front wall from the case, so that later it can be used for the matrix for the holes for the speakers in the newly manufactured case for 100 liters. From the remains of the buildings, good boxes are obtained for potatoes and markoshka in the cellar.
You can try to build up the old building.

In the first case, you need to focus on the dimensions - 1100x360x350 and manufacturing in a furniture workshop according to your drawings, with swearing and nitpicking about quality. We will consider the second way. So, you can try to get by with little bloodshed. We make it ourselves, or we order two boxes with tightly fitting walls and lids made of double 10-layer plywood with external dimensions - 380x360x285. In the bottom of the column and in the lid of the box, we cut out the same holes of approximately 270x210. Cover the inside of the box with felt. After assembly, it will be unrealistic to do this. We drill holes in the lid of the box and in the bottom of the column through which we fasten them together with bolts. The heads of the bolts should sink into the potai. Falling asleep a little - 10 kilograms of shot does not hurt, we throw a gauze bag with cotton wool on top. Pre-spill the connection with epoxy with a normal hardener content. We glue the junction with felt. The rest of the movements with the body, as in paths 1 and 2. We take the mid-frequency head 30 GDS-1. You just need to check them - a lot of marriage. Purely mechanical property. Further. We measure the resonance f of all speakers. You can sign with a felt-tip pen directly on the magnets so as not to get confused and not to measure everything again.

It would be nice if the resonance frequency of the paired speakers did not differ much. If the speaker makes extraneous sounds at any of the audio frequencies, then it must either be cleaned or changed if normal operation was not achieved by cleaning. We calculate and make filters for our case. The fewer inductances, the better. We continue to deal with the body. We remove excess resin at the junction. We grind it. We make two wooden boxes for filters. We will mount them on the back wall from the outside. We solder the wires from the amplifier directly to the filters. And we will drag the wires to the speakers through the fastening of the speaker connectors. All wires are branded audiophile. Choose your price range. Just take very expensive ones - it makes no sense. It is better to convert the phase inverter to a frequency of 31.5 - 40 Hz. If the dome of the high-frequency head is made of lavsan, then, having removed the crosspiece, it is necessary to smear the suspension and the outer third of the dome with perchlorovinyl. We paste over the entire body with a self-adhesive film. For the rest, see path 1 and path 2. With mandatory step-by-step verification - better - worse. The best method, if there is no obvious result, is blind listening.

Literature

Zhagirnovsky M., Shorov 8. Improving the sound of 35AC-1 and its modifications. - Radio, 1987, No. 8, p. 29, 30.
Shorov V. Improvement of loudspeaker heads. — Radio. 1986, no. 4, p. 39-41.
Aldoshina I., Voishvillo A. High-quality acoustic systems and emitters. — M.; Radio and communication. 1985.
Zhbanov V. Mechanical damping of diffusers. - Radio, 1988, No. 5, p. 41-43.
Maslov A. Once again about the alteration of the loudspeaker 35AC-212 (S-90). - Radio, 1985. No. 1, S. 59.
Zhbanov V. On the damping of dynamic heads. - Radio, 1987, No. 8, p. 31-34.
Gennady and Karen Arzumanov. To the question of the modernization of acoustic systems. Vestnik A.R.F. №6" 2000

Music lovers are constantly arguing about which speaker system to choose for comfortable listening to music at home. And this is no accident: the entire contingent was divided into two camps. The former believe that it is worth shelling out a tidy sum for buying a cool Hi-Fi (or even better Hi-End) system in order to be happy and forget about headaches about this topic for the rest of your life. But there are those who are not ready to give up their entire life's savings for expensive acoustics (instead of a car or an apartment), which is why they consider the best option to purchase simpler equipment or to refine the good old classics to good sound.

In this article, we will talk about one of the most popular audio systems from the times of the USSR, which could not leave indifferent any of its owners. The S90 speakers, whose technical characteristics are able to excite the mind to this day, have become one of the highest achievements of the Soviet company Radiotekhnika.

Speaker models

The very first thing worth mentioning is the real and full name of the speaker model - 35AC-012. An important factor is the fact that this acoustics was produced in several variations. The most popular of them are S90 and S90B. There were also models S90i, S90D and S90f, but they were not widely used and are now almost never found.

The model with the postfix "B" differed from the usual "nineties" in a wider range of reproducible frequencies. Also a significant difference was the introduction of an indicator of electrical overload of the speakers. The recommended power rating of a high-quality amplifier for these speakers is in the range of 20 to 90 watts. It is also worth noting that Radiotekhnika S90, S90B (and other modifications) were the first models of acoustic systems that met international requirements for Hi-Fi category equipment.

Design

The case, in which the S90 speakers are enclosed, is, in fact, a non-separable rectangular box made of fine wood veneer. The walls of the speakers are 16 mm thick, the front panel is made of plywood 22 mm thick. The internal joints of the walls of the case are connected by special elements that increase the rigidity and strength of the structure, but do not interfere with high-quality sound.

Looking at the device from the front, the speakers are arranged in the following order (from top to bottom): tweeter, midrange speaker and woofer. Also on the front panel of the S90 speaker you can see the frequency response graph (amplitude-frequency response) and the phase inverter hole. While the frequency response is located above or below (depending on the acoustic model), the phase inverter is always located at the bottom. This was done for reasons of proper design for better sound and giving the speakers good bass.

S90 speakers: specifications

If we take the usual S90 as an example, then they are equipped with dynamic direct-radiation heads. More precisely, a high-frequency head 10GD-35, a mid-frequency head 15GD-11A and a low-frequency head 30GD-2 (in later models - 75GDN-1-4).

Equipped with two step playback level controls for adjusting the midrange and treble in the ranges from 500 to 5000 Hz and from 5 to 20 kHz. Each knob moves in three fixed positions. In the "0" position, there is no obstruction to the signal from the crossover filter, and it is fed directly to the corresponding head. When using the "-3 dB" and "-6 dB" positions, the signal is attenuated by 1.4 and 2 times, respectively, with respect to the "0" position. By switching the selected knob, you can make changes in the timbre of the sound.

The nominal power of the S90 speakers is 90 watts, while the nominal power is 35 watts. The indicator of the nominal electrical resistance in this speaker system is at around 4 ohms, and the frequency range available for playback ranges from 31.5 Hz to 20 kHz. The nominal sound pressure of the S90 is 1.2 Pa. I would like to note the rather impressive dimensions of one column - 71.0 x 36.0 x 28.5 cm, and the total mass of the entire system reaches 30 kg.

Speaker layout and connection to the sound source

In order to understand whether it is worth refining any speaker system, you need to study all the data and aspects of the equipment. Below is the electrical diagram of the S90 speakers. Even a novice radio amateur can figure it out, you just need to have at least basic knowledge.

Another important point is the correct connection of the speaker system. After all, if something goes wrong, even when connecting, you can, unwittingly, disable the equipment. You don't have to be a pro to figure out how to hook up your S90 speakers. The main thing is to have at least 20 watts with an amplifier (in this case, most likely, the sound will not be loud enough for large rooms), but not more than 90 watts. In case of exceeding the permissible value of the amplifier power, the user runs the risk of being left without acoustics due to its breakdown. To connect, you will need ordinary acoustic wires, which must be connected to the terminals on each speaker and on the amplifier. The main condition for connection is polarity.

Refinement 35AC-012

As it becomes clear from the description above, in itself it has good technical characteristics and is capable of “building up” even small public spaces. But for home use, the most sophisticated music lover will prefer to modify the S90 speakers with their own hands. And all because, assembled more than twenty (or even thirty) years ago, the acoustic systems of the Radiotekhnika company already in those years did not have a high build quality and materials used.

Parsing

In the event that the acoustics were purchased in a used condition and are currently well-worn by life, it is worth attaching importance to the appearance. To do this, you need to disassemble the S90 speakers, after putting them on the “back”.

When removing the speakers, you need to take into account that the treble and midrange heads are attached to the case using the same screws as the lining. The woofer is attached separately, and you need to be as careful as possible so as not to damage it when unscrewing it.

Treble/midrange controls are much easier to dismantle than you think. All you need to do is carefully remove the decorative caps that are in the center of each knob. After that, using a screwdriver, it is necessary to unscrew the screw that has opened to the eye, and remove the regulator knob itself. The plastic lining must be carefully lifted from both sides with the help of flat objects and removed, and the four screws remaining under it must be unscrewed. After that, you can push the S90 column inside, not forgetting to unsolder it from the filter.

Cotton bags inside the case must be removed. Again, if the previous owner of the speakers did not forget to return them to their place in case of parsing.

You should first unsolder the panel with filters from the output from the back of the speaker, after which it must be dismantled by unscrewing the screws. Now you can remove the panel with the terminals attached to it.

Appearance and body

If the speaker grilles and decorative trims are “tired”, then it is worth straightening and painting them, having previously sanded and degreased them. This will give a fresh look to the speakers. The body of the S90 will loosen over time and can be strengthened as desired. This will result in a better sounding woofer.

This can be done in various ways, including installing spacers and additional corners inside. It is also necessary to pay attention to sealing all joints and seams with ordinary plumbing sealant. In addition, you can glue the inner walls of the case (except the front) with foam rubber, which will increase the volume of the latter.

Terminals and filter

Knowledgeable radio amateurs are advised to replace the standard speaker terminals with universal-type terminals with gold-plated connectors. The installation place must be lubricated with sealant and put the panel with the terminals in place.

Considerable attention should be paid to the sound filter. If it was attached to the body with metal screws, then the filter setting will go astray. There are cases when the filter was assembled on a metal plate. This should be fixed by transferring all the nodes to the plywood panel. The circuit of the filter itself could be changed at the factory due to different speaker parameters, so you should make sure that everything is assembled according to GOST. If there are jumpers in the filter, then they must be removed and replaced, for example, with an oxygen-free copper cable with a cross section of 4 mm 2. It is worth removing the attenuator from the circuit, as it simply distorts the sound, and replacing the wires used to connect the speakers to the filter.

For woofers, a wire with a cross section of 4 mm 2 is suitable, for midrange speakers - with an area of 2.5 mm 2, for tweeters - with an area of 2 mm 2. After such simple actions, the filter must be returned to its place and closed with foam rubber.

Speakers and other "little things"

For speakers, new seals should be cut. This can be done with the help of cheap or simply obsolete mouse pads. This is the easiest option. After that, it is worth returning them to their seats and putting decorative trims and nets.

Before installing the regulators in place, you will have to unsolder all the resistances from them. When installing them in place, it is imperative to apply a sealant, as well as when installing a phase inverter.

Through such simple manipulations, the S90 speakers acquire a new life. The sound quality becomes an order of magnitude higher, despite the small costs. As a result, we can say that if there is no money for expensive 2.0 format acoustics, you can use this option and become the happy owner of the time-tested AS Radiotekhnika S90. If it happens that only half of the speakers are available, do not be upset. After all, it is noteworthy that the S90 column, a photo of which can be found on almost any website of acoustic lovers from the times of the USSR, can work alone and give a good result.

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