Materials and equipment used.
Veneer and polyurethane paints and varnishes are used as finishing when restoring acoustic speakers. We use natural and fine-line veneer produced by ALPI (Italy), polyurethane and PVA dispersion adhesives produced by Kleiberit (Germany). We have more than 90 veneer options in stock, allowing you to choose the color scheme to match the style of the customer’s home interior. In addition, the finishing can be done using polyurethane paints of any color. Surfaces can be matte or glossy with open and closed pores of wood (veneer). When restoring acoustics, professional hand-held equipment and tools, a veneer press and a painting booth (we have extensive experience in piano lacquer painting) are used.
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.
To accurately calculate the restoration, you must provide:
Dimensions of the 1st building (WxHxD).
Close-up photo of the damage.
Indicate what work needs to be done.
If it is necessary to replace the finish, indicate:
When using veneer, indicate the veneer used from our catalog and the surface option: matte or glossy, open or closed pore wood.
If paint is used: matte or glossy surface.
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 that 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.
Restoration of B&W ASW CDM subwoofer
A B&W ASW CDM subwoofer enclosure was received for restoration. The case had many scratches (including deep ones) and broken corners. The main goal pursued by the customer was to restore the case while maintaining the original appearance. Therefore, such design nuances as grooves and edges around the perimeter were exactly duplicated by us.
Case size (H×W×D): 393x396x420 mm Finishing: tangential mahogany veneer, oil-painted. The coating is matte, open wood pores. The cost of work for May 2022 is $230
The work we have completed: 1. Removing the paint and varnish surface. 2. Removing material around the perimeter. 3. Gluing MDF into the milled areas. 4. Puttying cracks, dents, removing corners and planes. 5. Veneer veneering of cabinets. 6. Edge milling. 7. Milling grooves around the perimeter of the body. 8. Painting the groove and edge. 9. Painting the body with oil.
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.
Restoration and repair of the Hitachi HS-30G speaker system
We received a Hitachi HS-30G speaker system (made in Japan) for restoration. As you can see in the photo, the acoustics are in very poor condition. In addition to broken corners, scratches, etc., the walls of the speakers came apart due to moisture. In these places, the chipboard delaminated and turned into dust. It was decided to completely replace the material in areas with large chips, broken corners and cracks.
The second unpleasant surprise was that the tweeter was faulty. The testing method revealed that the problem was not in the dynamics, but in the capacitors of the isolation filter circuit, so a replacement was made. After which the following problem appeared - the HF potentiometer did not work in some positions, it had to be repaired and serviced.
The next thing is that the speaker housings had rather thin walls (as for such a low-frequency link) and there were no reinforcing ribs or partitions inside. Because of this, the cabinet resonated quite strongly at high volumes. Having offered the customer a solution, he agreed to strengthen the connecting walls and the rear panel of the case with timber.
The acoustics were supplied with protective nets (grills), which also needed restoration. The decorative radio fabric was replaced.
We carried out all the necessary work on restoration and repair of the acoustic system. The coating is matte varnish with open pores of dark Wenge platinum wood (veneer). In addition to the stunning appearance, the acoustics sound has improved.
Case size (H×W×D): 666×361×287 mm Finish: varnished veneer. The coating is matte, open wood pores. The cost of work for April 2022 is $385. The work we have completed: 1. Replacement of capacitors in the isolation filter circuit. 2. Repair and maintenance of potentiometers. 3. Removing the old finish. 4. Removing material around the perimeter in problem areas. 5. Gluing plywood into milled areas. 6. Puttying cracks, dents, removing corners and planes. 7. Gluing timber inside to strengthen the connecting walls and the rear panel of the housing. 8. Reinforcement of front panels with veneer for strengthening. 9. Veneer veneering of bodies. 10. Painting of cases. 11. Mounting of all electrical components into the housing. 12. Replacement of fabric of protective nets.
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.
Restoration and veneering of the housings of the Sony APM-22ES speaker system
Case size (H×W×D): 515×310×310 mm Finish: veneer, painted with black acrylic paint. The coating is matte, open wood pores. Work we have completed: 1. Removal of old finishing. 1. Restoration of surfaces. 2. Veneer veneering of the body. 3. Covering the body with paints and varnishes. The cost of work for March 2022 is $250 (pair)
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.
Restoration and veneering of the Snell AN J3 speaker system
Case size (H×W×D): 585×330×240 mm Finishing: Mackassar ebony veneer. The coating is matte varnish, open time. Work we have completed: 1. Surface restoration. 2. Veneering of the body. 3. Coating of the body with paints and varnishes. The cost of work for December 2022 is $280 (pair)
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.
Restoration and veneering of the body of the Corvette 35AC-208 acoustic system
Case size (H×W×D): 715×395×360 mm Finishing: dark Wenge veneer. The coating is matte varnish, open time. Work we have completed: 1. Puttying and removing knocked-down corners and dents. 2. Veneering of the body. 3. Coating of the body with paints and varnishes. The cost of work for September 2015 is 150 dollars. (pair)
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 saturate 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; midrange speakers - 110 rubles; batting - 150 rubles; glue, staples of the stapler (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.
Restoration of the case of the Amfiton 25 AS-027 acoustic system
Case size (H×W×D): 600×320×270 mm Finish: paint. Covering: black matte paint. The work we have completed: 1. Dismantling of dynamic heads. 2. Puttying and removing broken corners and dents. 3. Coating of the body with paints and varnishes. 4. Painting protective nets. The cost of work for February 2015 is $140 (pair)
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.
Restoration and veneering of the acoustic system housing
Case size (H×W×D): 515×280×220 mm Finishing: Gabon Ebony veneer. The coating is matte varnish, open time. Work we have completed: 1. Dismantling of old finishing. 2. Puttying and removing broken corners and dents. 3. Veneering of the body. 4. Coating of the body with paints and varnishes. The cost of work for January 2022 is $120 (pair)
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 “native”, 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.
Veneering of the speaker system housing
Vinyl player case veneering
Case size (H×W×D): 60×469×375 mm Finishing: Karelian birch veneer. The coating is matte varnish, open time. Work we have completed: 1. Puttying and removing knocked-down corners and dents. 3. Veneering of the body. 4. Coating of the body with paints and varnishes. The cost of work for 2013 is $100
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Accessories
First of all, this is an amplifier. The Soviet ones have already expired, but if you have the skills to use a soldering iron, it’s 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, that’s the owner’s business.
