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 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 still produced in the times of the USSR, which could not leave any of its owners indifferent. 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 to mention isthe real and full name of the speaker model is 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 seen.
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 that encloses the S90 speakers is, in fact, a non-separable rectangular box made of chipboard. Facing is veneered veneer of precious wood. 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.
When viewed from the front, the speakers are arranged in the following order (from top to bottom): tweeter, midrange speaker and woofer. Also on the front of the S90 speakeryou can see the graph of the frequency response (amplitude-frequency response) and the opening of the phase inverter. 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).
The speaker system is 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 crossover signal, 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 diagram and connection to 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 beginner 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 a sound source with an amplifier of at least 20 watts (in this case, most likely, the sound will not be loud enough for large rooms), but not more than 90 watts. If the permissible power of the amplifier is exceeded, 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.
Revision 35AC-012
As it becomes clear from the description above, the acoustic system itself 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. BUTall because the acoustic systems of the Radiotekhnika company, assembled more than twenty (or even thirty) years ago, already in those years did not have high build quality and the materials used.
Parse
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 appearance. To do this, you need to disassemble the speakers S90, after putting them on the "back".
When removing the speakers, please note that the treble and midrange heads are attached to the body using the same screws as the decorative nets and trims. The woofer is attached separately, and you need to be as careful as possible not to damage it when unscrewing it.
Next, you should pull out the phase inverter, after removing the cover from it. Since the part is plastic, it is worth applying maximum care so as not to accidentally break off the fasteners.
The treble/midrange controls are much easier to remove 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, the attenuator can be pushed inside the S90 column, remembering to unsolder it from the filter.
The cotton bags inside the case need to 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, pre-sanding and degreasing 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 terminals for connecting acoustics to terminals of a universal type with gold-plated connectors. The installation place must be lubricated with sealant and put the panel with 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 scheme of the filter itself could be changed at the factory -manufacturer due to the different parameters of the speakers, so you should make sure that everything is assembled in accordance with 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 mm2, for midrange speakers - with an area of 2.5 mm2, for The tweeters are 2 mm square2. After such simple actions, the filter must be returned to its place and closed with foam rubber.
Speakers and other "little things"
Cut out new seals for the speakers. This can be done with the help of cheap or simply obsolete mouse pads. This is the easiest option. After that, you should return them to their seats and put decorative overlays and nets.
Before installing the regulators, you will have to solder all the resistances out of them. When installing them in place, it is imperative to apply sealant, 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 Radio Engineering S90. If it so happened thatonly 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.
