Music lovers constantly start debates 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 first ones think that it is worth paying a tidy sum for buying a cool Hi-Fi (or even better Hi-End) system 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 the accumulation of their whole lives for expensive acoustics (instead of a laid car or apartment), and therefore 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 by the times of the USSR, which could not leave indifferent any of its owner. S90 speakers, the technical characteristics of which are able to excite the consciousness to this day, have become one of the highest achievements of the Soviet company Radio Engineering.
Column Models
The very first thing worth mentioning is the current 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 are not widely used and are currently almost never found.
The model with the “B” postfix differed from the usual “nineties” in a wider range of reproducible frequencies. Also significant difference was the introduction of an indicator of electrical overload speakers. The recommended power value of a high-quality amplifier for these speakers is in the range of 20 to 90 watts. It is also worth noting that the "Radio Engineering" S90, S90B (and other modifications) were the first models of speaker systems that met international requirements for Hi-Fi equipment.
Design
The enclosure in which the S90 columns are enclosed is, in fact, a non-separable rectangular box made of chipboards. The veneer is veneered veneer made of fine wood. The walls of the columns are up to 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 impede the sound quality.
If you look at the device from the front, then the speakers are arranged in the following order (from top to bottom): tweeter, mid-range speaker and woofer. Also on the front panel of the S90 column you can see the graph of the frequency response (amplitude-frequency characteristic) and the hole of the bass reflex. While the frequency response is located either above or below (depending on the model of acoustics), the bass reflex is always at the bottom. This is done for reasons of proper design for better sound and give the speakers good bass.
S90 speakers: specifications
If we take the usual S90 as an example, then they have dynamic direct radiation heads installed. More precisely, the high-frequency head 10GD-35, the mid-frequency head 15GD-11A and the low-frequency head 30GD-2 (in later models - 75GDN-1-4).
The speaker system is equipped with two step reproduction 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 position "0" for the signal from the separation filter there is no obstacle, and it is fed directly to the corresponding head. When using the “-3 dB” and “-6 dB” positions, the signal is attenuated 1.4 and 2 times, respectively, with respect to the “0” position. By switching the selected control, you can make changes to the tonal color of the sound.
The rated power of the S90 speakers is 90 watts, while the rated power is 35 watts. The rated electrical resistance in this speaker system is at around 4 Ohms, and the range of frequencies 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 circuit and sound source connection
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 an electrical diagram of the S90 speakers. Every beginner radio amateur will be able to understand it, you only 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 connected, you can, without wanting to, disable the equipment. To understand how to connect the S90 speakers, you do not need to be a professional. 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 value of the amplifier power is exceeded, the user runs the risk of being left without acoustics due to its breakdown. To connect, you will need ordinary speaker wires, which must be connected to the terminals on each speaker and on the amplifier. The main connection condition is the polarity.
Finalization 35AS-012
As it becomes clear from the description above, the speaker system itself has good technical characteristics and is capable of “swinging” even small public spaces. But for home use, the most sophisticated music lover will prefer to finalize the S90 speakers with their own hands. And all because the speakers of the Radio Engineering company collected over twenty (or even thirty) years ago already in those years did not have high build quality and materials used.
Parsing
In the event that the acoustics were purchased in a used condition and are currently well-battered by life, it is worthwhile to attach importance to the appearance. To do this, you need to disassemble the S90 speakers, having previously placed them on the “back”.
When removing the speakers, you need to take into account that the tweeter and midrange heads are attached to the case using the same screws as the decorative mesh and trim . The woofer is mounted separately, and you need to be as careful as possible so as not to damage it when unscrewing.
Next, pull out the bass reflex, having previously removed the cover from it. Since the part is plastic, it is worthwhile to use maximum accuracy so that you do not accidentally break off the fasteners.
Treble / midrange controls are much easier to dismantle than they seem. All that needs to be done is to carefully remove the decorative plugs that are located 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 cladding must be carefully lifted from two sides with the help of flat objects and removed, and the four screws remaining under it should be unscrewed. After that, the attenuator can be pushed inside the S90 column, not forgetting to solder it from the filter.
The 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.
It is necessary to first unsolder the panel with filters from the outlet on the back of the speaker, after which it must be removed by unscrewing the screws. Now you can remove the panel with the terminals attached to it.
Appearance and body
If the grilles and decorative lining of the speakers are "tired", then it is worth straightening and painting them, having previously sanded and degreased them. This will add freshness to the look of the columns. The S90 speaker casing loosens over time and can be strengthened as desired. This will result in a better bass sound.
You can do this in various ways, including installing spacers and additional corners inside. It is also necessary to pay attention to the sealing of all joints and seams using conventional plumbing sealant. Everything else can be glued with foam rubber to the inner walls of the body (except the front), which will increase the volume of the latter.
Terminals and Filter
Knowledgeable hams advise replacing the standard speaker terminals with universal terminals with gold-plated connectors. The mounting location must be greased 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 casing with metal screws, the filter setting will be lost. There are cases when the filter was assembled on a metal plate. Correct this by moving all the nodes to the panel from plywood. The circuit of the filter itself could be changed at the factory in connection with various parameters of the speakers, so make sure that everything is assembled according to GOST. If jumpers are present in the filter, 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, since it simply distorts the sound, and replace 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 mid-range speakers - 2.5 mm 2 , for tweeters - 2 mm 2 . After such simple actions, the filter must be returned to its place and closed with foam rubber.
Speakers and other "trifle"
For speakers, cut new gaskets. This can be done using cheap or simply outdated computer mouse mats. This is the easiest option. After that, it is worth returning them to their seats and putting decorative pads and nets.
Before installing the regulators in place, you will have to remove all the resistance from them. When installing them in place, it is absolutely necessary to use a sealant, as when installing a bass reflex.
Through such simple manipulations, the S90 speakers gain new life. The sound quality is becoming an order of magnitude higher, despite the low costs. In the end, we can say that if there is no money for expensive 2.0-format speakers, you can use this option and become the happy owner of the time-tested Radio Engineering S90 AS. 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 site of acoustics lovers since the USSR, can work alone and give a good result.