Floor-standing 3-way speaker with bass reflex Radio equipment “S-50B” is designed for high-quality reproduction of music and speech phonograms in stationary living conditions with input power 20 - 50 W. The speaker has an overload indication, which is triggered when a signal is supplied to the speaker with a level exceeding its rated power.
Basic specifications:
Frequency range 40 (-8 dB) – 20000 Hz
Sensitivity in the range 100 – 8000 Hz at 1 W power: 85 dB
Frequency response unevenness in the frequency range 100-8000 Hz: ±4 dB
Characteristic sensitivity: 0.356 Pa/√W
Nominal electric power: 25 W
Nameplate electrical power: 50 W
Maximum short-term power: 400 W
Nominal electrical resistance: 8 ohms
Minimum full value electrical resistance: 7.5 ohm
Harmonic distortion of speakers, at a sound pressure of 90 dB at frequencies:
250 – 1000 Hz: 2%
1000 – 2000 Hz: 1.5%
2000 – 6300 Hz: 1%
Speakers used:
Size: 580x314x256 mm
Design:
The speaker body is made in the form of a rectangular non-demountable box made of chipboard, veneered with valuable wood veneer. At the joints of the housing walls on the inside there are elements installed that increase the rigidity and strength of the housing.
The heads installed on the front panel of the speakers are framed by two decorative overlays, made of plastic and painted “metal” or without painting. One cover frames the midrange and tweeter heads, as well as the upper half of the front panel of the speakers, the other frames the woofer head and the lower half of the front panel. MF, HF and LF heads are protected metal mesh. The top cover is attached with 8 screws, and the bottom with 10. The midrange head with inside isolated from the total volume of the body by a plastic casing in the shape of a truncated cone. All heads are located on the front panel symmetrically relative to the vertical axis of symmetry of the speaker. At the top of the front panel there is a nameplate with the sound pressure frequency response curve and the name of the speaker depicted on it. In the upper right corner there is an indicator of speaker overload, and in the lower part of the panel there is a rectangular bass reflex output hole, the tuning frequency of which is 37 Hz.
On the rear wall of the speaker there is a nameplate with the main technical characteristics and a block with clamps for connecting the connecting cord. The internal volume of the speaker is 27 liters. To reduce the influence of the resonances of the internal volume of the housing on the frequency response of sound pressure and the sound quality of the speaker, it is filled with a sound absorber, which is mats made of technical wool, covered with gauze. The mats are located and fixed on the inner surfaces of the housing walls.
Electrical filters are mounted inside the housing on a single board, providing electrical separation of low-, mid- and high-frequency speaker bands. Crossover frequencies provided by the filters: between the bass and midrange heads - 900 ±50 Hz; between the midrange and high frequency heads - 5000 ±500 Hz.
The design of the filters and the overload indication unit uses resistors such as BC, MLT, SPZ-386, S5-35V, capacitors such as R73-11, MBGO-2, K50-12 and inductors on plastic cast frames.
The delivery set includes four plastic feet, which can be attached to the base of the case if necessary.
So, Hello Everyone!In general, I screwed up the speakers a little. It became much better to play than in the state in which they arrived to me. Although in a good way, it was necessary to think about the crossover, the midrange has a generally small diffuser stroke, or the resistance should have been hung in parallel, or played with the frequency, or something else. In general, I’m not particularly strong in this part. And not knowing the Z-characteristic of the speakers, I didn’t point my finger at the sky. And the crosses there are quite tricky for me. I wanted to remove a bunch of coils, resistors, resistors altogether, because... I think they spoil the sound. Well, I didn’t experiment at all. So it plays more or less and more money I wouldn’t have been disappointed, and time was running out. I might get confused myself, when radio equipment turns up. So the buildings are normal. I liked it. Made of chipboard, front made of 18 mm plywood.
Now the report.
They came to me in such a deplorable state:
The resistance was kind of coarse, and the speakers had different ones. It was then that I caught up. There were different midrange frequencies. In one column 6GDV 25 Ohm 13 cm! And in appearance it seems to be the same, but the GDS is 13 cm. One is jammed, so the differential does not move even when pressed. Well, it was clear that it had been wound, the glue everywhere was not factory-made, the second middle rattled when pressed. The housing under the midrange was broken in one. As I understand it, this is what they wanted to achieve more air. Everything is covered in dust and mold. In one column there were some children's rulers, balls, and pieces of plasticine all around. I forgot there were some cheap piezo HF ones screwed on top. Such ear cancer is worse than megaphones. Because There was only one HF 6GDV or whatever it’s called “yellow” one, turned off. In general, when I turned it on, I didn’t really know what to do with them; it was easier to think about throwing them away and buying speakers and reassembling the speakers myself.
Well, once I took it on, I had to somehow get out of the situation at an inexpensive price.
I started experimenting.
I took a car 4 ohm “silk” HF Ural.I decided to break out the standard mesh, because... the grids spoil the sound, so they will be under the standard grid, and we don’t need two grids. As well as one. I didn’t want a full-time job at all. decorative plast. I wanted to install a wall of radio equipment, I wanted to putty it and cover it with film, but I didn’t have the film at hand. (Not this time.
And at the same time, I inserted food into the cups from other HFs so that they would sag and stick out and filled them with hot glue:
I started experimenting with low-frequency design, tried a round phasic longer than the standard rectangular one.
Still, there was something I didn’t particularly like.
I decided to stop at ZY. I cut out the plug.IN seat they approached like family. But into the layer. the hulls did not fit and it was impossible to bore them there. At first I tried to mill out and remove the edge with a router, but I loosened it too much, but they still didn’t fit. I had to fix a small mistake with polyester. Strengthened the flange. And I decided to cut the housings a little and put the carpentry underneath. So the midrange will be screwed onto the plywood and as a brace at the front. and rear the walls of the glass will serve.
At the same time, the walls were glued a little with vibroplast and carpet with 88 glue, the front was missed. wall liquid nails...
I assembled the column, I press on the mid, look, the midrange is moving. I took it apart five times, I thought it was siphoning from under the wire. But then, as it turned out, it came from under the carpet, despite the fact that I stuffed the glass very tightly and the surface there was flat. In general, I poured 88 glue into it mixed with synthetic foam, such a mess, and probably coated the hole and cracks with liquid nails.
In the cross, I only replaced the wires incoming to the cross and to the mid by 2.5 squares:
Well, that's all. We assemble it, measure the resistance, it turned out as it should be.
I'm pleased with the result. But one GDN, at a low volume, the decel wheezes and rustles.
I'm taking it apart and figuring out the supply wires.
I began to move them, right in the place where they enter the diffuser, so it looked like a sore spot. GDN is from the 80s.) I used a soldering iron a little, everything became fine.Well, I’m putting the front in place. cover. I glued foam rubber to the 88th.
Everything works, I’m happy with the result, it’s cheap and normal.
While I was writing the article now, this client called the person I did and said that one GDN stopped playing.)
I suspect that this wiring has finally broken off. He probably threw it properly, and this is the result.I'll try to duplicate it with a second wire and solder it a little lower, where there's a through square. Tomorrow the mid will deliver.
And so they sound very decent and the bass was not buzzing and fast. Well, not very deep. Well, the speakers have a stated range of 40 Hz. From 40k they played normally. Well, pop. Infected Mushroom played with passion.)
Not for long though.)Well, nothing. So it’s a good idea to replace one GDN for him.
Description and modification of RRR Radiotehnika S-50B acoustics. Although the acoustics are old, they are worth paying attention to. Thanks eXcTeSy for the article.
Short description.
Electrical and electroacoustic parameters of the acoustic systems (AS) "S-50B" meet the requirements technical specifications 3.843.056TU. The speakers are designed for high-quality sound reproduction as part of household electronic radio equipment. The speaker has an overload indication, which is triggered when a signal is supplied to the speaker with a level exceeding its rated power. To operate, the speakers must be connected to an amplifier that has the highest (maximum) power at the output of each channel, ranging from 50 to 100 W. If the OVERLOAD indicator starts to light up during operation of the speaker, then you should reduce the level of the input signal supplied to it (by using the volume control in the amplifier to which the speaker is connected).
Main technical characteristics.
Rated electrical power of at least 50 W
Rated electrical power 25 W
Nominal electrical resistance 8 ohms
The range of reproduced frequencies is no longer 40-20000 Hz
Characteristic sensitivity in the frequency range 100-8000 Hz, at a power of 1 W, not less than 85 dB
dimensions AC 314x580x256 mm
Speaker weight no more than 23 kg
Disassembly.
Less than two days later, I wanted to take it apart. I removed the front panel, which consists of two parts. I took out the speakers LF 35 GDN-1-5, MF 20 GDS-1-16 and HF 6 GDV-1-16. The filter was original, not altered. He pulled out the cotton wool and threw it away. The bass reflex was not touched. Removed the wire holder. There was nothing more to sort out.
Finalization.
To begin with, I went through all the joints with silicone, there were no special gaps, but just in case it wouldn’t hurt. I replaced all the wires with new ones, took oxygen-free copper with a cross-section of 1.5. The filter was assembled according to the original design. Inside, the walls and bottom were lined with padding polyester, not thick, about 2 centimeters. The body itself was sanded and painted. I also updated the speakers. When assembling the speakers, I installed them on silicone. Between anterior wall and applied padding polyester with a plastic panel. I left the old legs (I couldn’t find anything better). It didn't turn out too bad. They also sound like mom don’t worry. Well, I think I wrote everything. See photo...
P.S. Several photos are not very good. took photos from my phone.
Manufacturer: PA "Radio Engineering", Riga.
Purpose and scope: for high-quality reproduction of music and speech programs in stationary living conditions (performance category UHL 4.2 according to GOST 15150-69).
The recommended power of a high-quality household amplifier is 20...50 W. The preferred installation option is floor-mounted.
Specifications:Сг3.843.0.56 TU.
Specifications:
Specifications | Values |
Reproducible frequency range, Hz | 40...20000 |
Uneven frequency response of sound pressure, dB, at the lower limit frequency of the reproduced frequency range relative to the average sound pressure level | -8 |
Uneven frequency response of sound pressure, dB, in the frequency range 100...8000 Hz relative to the average sound pressure level | ±4 |
Level of characteristic sensitivity (characteristic sensitivity), dB | 85 (0,356) |
Directional characteristic of the speaker, dB, determined by the deviation of the frequency response of sound pressure, measured at angles of 25 ± 5° in the horizontal plane and 7° in the vertical plane, from the frequency response measured along the acoustic axis of the speaker 0°: | |
in vertical and horizontal planes | +3 |
-4 | |
Harmonic distortion of speakers, %, determined by the total characteristic harmonic coefficient three levels of average sound pressure 90 dB at frequencies, Hz, no more | |
250...1000 | 2 |
1000...2000 | 1,5 |
2000...6300 | 1 |
Nominal electrical resistance (nominal value of total electrical resistance), Ohm | 8 |
Minimum value of total electrical resistance, Ohm | 7,5 |
Maximum short-term power, W | 400 |
Maximum noise (nameplate) power, W | 50 |
Type of low-frequency acoustic design | bass reflex |
Weight, kg | 15 |
Dimensions, mm | 314x580x256 |
Sound pressure frequency response shape measured along the acoustic axis
Design Features:
- The speaker body is made in the form of a rectangular non-demountable box made of chipboard, veneered with valuable wood veneer. At the joints of the housing walls on the inside there are elements installed that increase the rigidity and strength of the housing.
- The speaker system uses a set of heads: , . The heads are produced by Radiotekhnika software.
- The heads installed on the front panel of the speaker are framed by two decorative overlays made of plastic and painted “metal-like” or without painting. One cover frames the midrange and tweeter heads, as well as the upper half of the front panel of the speakers, the other frames the woofer head and the lower half of the front panel. The midrange, tweeter and bass heads are protected by metal meshes. Each of the pads is secured with six screws. The midrange head is isolated on the inside from the total volume of the housing by a plastic casing in the shape of a truncated cone. All heads are located on the front panel symmetrically relative to the vertical axis of symmetry of the speaker. At the top of the front panel there is a nameplate with the sound pressure frequency response curve and the name of the speaker depicted on it. In the upper right corner there is an indicator of speaker overload, and in the lower part of the panel there is a rectangular bass reflex output hole, the tuning frequency of which is 37 Hz. On the back wall of the speaker there is a nameplate with the main technical characteristics, a block with clamps for connecting the connecting cord.
- The internal volume of the AC is 27 dm3. To reduce the influence on the frequency response of sound pressure and the sound quality of speakers from the resonances of the internal volume of the housing, it is filled with a sound absorber, which is a mat of technical wool covered with gauze. The mats are located and fixed on the inner surfaces of the housing walls.
- Electrical filters are mounted inside the housing on a single board, providing electrical separation of low-, mid- and high-frequency speaker bands. Crossover frequencies provided by the filters: between the bass and midrange heads - 900±50 Hz; between the midrange and high frequency heads - 5000 ±500 Hz.
- The design of the filters and the overload indication unit uses resistors such as BC, MLT, SPZ-386, S5-35V, capacitors such as K.73-11, MBGO-2, K50-12 and inductors on plastic cast frames.
- The delivery set includes four plastic feet, which can be attached to the base of the case if necessary.
The AS "Radiotekhnika S-50B" with careful operation remains operational for many years. As it turned out, the sound of this speaker can be significantly improved with simple modifications by replacing the HF heads and changes in the crossover.
The Radiotekhnika S-50B acoustic system has been produced by the Riga Radiotekhnika Production Association since the first quarter of 1982. At the time of release, the system was a fairly high-quality example of an acoustic system (AS), which was equipped with domestic radio equipment.
Schematic diagram this speaker is shown in Fig. 1. According to the diagram, the passive crossover of the speaker is made using second-order filters. Quite a lot has been written in the literature about the influence of the order of filters on the operation of dynamic heads, and most authors note the greater efficiency of using filters of a higher order. To prove this, they provide graphs of measurements of AHF columns and delightful statements about the quality of their work. However, the results of subjective expert listening to speakers using first-order filters do not always confirm this. Unfortunately, instrumental measurements of the characteristics of speakers in an anechoic chamber do not allow us to fully assess their quality. Expert listening is necessary element assessments.
Rice. 1. Schematic diagram of the speaker
The literature contains descriptions of the use of series filters in a crossover, allowing a different look at the formation of loudspeaker frequency bands. This method has a number of advantages that improve sound quality.
To test this solution, the Radiotekhnika S-50B acoustic system was modernized. For this purpose, two functional speakers were taken, the difference in sound of which was practically absent. The effectiveness of the changes made was checked by comparing the results of listening to the converted speaker with the control one. During the tests, the modernized amplifier "Radio Engineering U-7101" was used. Additionally, changes have been made to the configuration and design of some speaker elements.
The diagram of the modernized version of the speaker (indication board is not shown) is shown in Fig. 2. As can be seen from the diagram, the dynamic head 6GDV-1 was replaced with an isodynamic head 10GI-1-4. This head has more advanced technical characteristics and more power. Using a series filter allows you to combine heads with different nominal resistances in different bands. This property turned out to be very useful in this situation. Correction of the HF return is carried out by selecting resistor R1.
Rice. 2. Scheme of the modernized version of the speaker system
The 20GDS-1 mid-frequency head had many complaints about sound quality. Many authors have proposed many ways to improve it. Using tennis balls and re-gluing the dust cap to significant changes did not produce any sound. But it became obvious that the low rigidity of the cap was one of the reasons for the complaints. Therefore, the modification began with this - the dust cap was covered with two layers of celluloid dissolved in acetone. At the same time, the rigidity of the cap increased significantly; in fact, the dome was reinforced. Next, a horn of a suitable size was glued onto the dome of the cap, which somewhat improved the sound of the head at frequencies above 4 kHz.
The return of the heads is affected by the residual magnetization of the installed magnets. To test the effectiveness of introducing an additional magnet, two dynamic heads were fastened with diffusers towards each other. A signal from the AF generator was supplied to one of the heads, and the second head was connected to a millivoltmeter. By installing an additional magnet in the required polarity to the main magnet, you can see how effective the additional magnetic field will be. In the head I tested, the output increased by 2 dB. Further increasing the number of magnets had no effect, so only one magnet was glued to the main magnet. General form The modified midrange head is shown in Fig. 3. On low-frequency heads, this operation did not reveal the need for additional magnets.
Rice. 3. General view of the modified midrange head
After dismantling the unnecessary elements, the parts of the new crossover are placed on its previous board (the numbering of the elements has been changed). In accordance with the new crossover circuit (see Fig. 2), only capacitor C1 6.8 μF for a voltage of 160 V (K73-11) and coil L2 with an inductance of 0.3 mH have been added; everything else was already on the board. In addition, the values of powerful resistors (R1) were changed to equalize the output of the RF heads. In Fig. Figure 4 shows the upgraded filter board installed in the column.
Rice. 4. Upgraded filter board installed in the column
Volume sound-absorbing material increased in each case by 50%, and in the midrange head - by 70%. The count was made from the factory settings of the absorber. The sound absorber present in the housing (cotton wool in a mesh) is concentrated in the upper part of the speaker, and the additional one is rolled up into a rag mat and placed on the rear wall behind the woofer head.
The HF head is rotated 90° relative to the recommended one due to the need to fit into the image decorative panel with grate. If this is not done, then part of the slot holes of the emitter will be covered by the panel. In this case, you will have to make changes to the panel design, which is very difficult. I listened to both options for the head location and, without noticing any noticeable changes in the radiation pattern, accepted the option of a horizontal arrangement of the head slots. An additional horn in the midrange head and optimization of the location of the speakers make it possible to mitigate the contradiction, but do not exclude the use of the option recommended by the manufacturer.
Practically, the markings for installing the head were carried out as follows. From the upper point of the midrange head contour circumference, 4 mm is set aside upward and a line is drawn, which is the lower boundary of the HF head installation. Next, the remaining marking lines are drawn according to the dimensions of the head perimeter and the hole is cut out. The head is fastened using two legs, which tighten it when tightening the screws.
The tightness of the installation is ensured by a seal located around the perimeter of the rear panel of the emitter. The sealant is a rubber tube with an adhesive strip, which is used to seal doors and windows. The same seal is used when installing the remaining heads. The process of completing the installation of heads is shown in Fig. 5.
Rice. 5. Installation of HF heads
Some changes have been made to the design of the decorative panel and the grille of the MF-HF emitter group. They are necessary to hide traces from round hole the old head and the organization of the horn for the new one. back side The decorative panel with the changes made is shown in Fig. 6. The general view of the completed product is shown in Fig. 7.
Rice. 6. Reverse side of the decorative panel with changes made
Rice. 7. General view of the completed product
The results of a practical comparison of the two speakers showed a clearly visible advantage of the modernized version. The sound has become more prominent, and the impulse characteristics have improved. His great emotional detail became apparent. Joining bands, attacks in sounds musical instruments and timbres - everything has changed in better side.
Literature
1. Acoustic system"Radio engineering S-50B." - URL: http://rw6ase.narod.ru/00/as/radiotehnika_s50w.html (03.22.18).
2. Elyutin A. Sequential crossover. - URL: http://www.avtozvuk.rf/az/ 2010/01/082-krossover.htm (03/22/18).
3. Shikhatov A. Sequential filters in crossover speakers. - Radio, 2017, No. 12, p. 13-16.
4. Platonenko V. Second life of the amplifier "Radio Engineering U-7101S". - Radio, 2018, No. 1, p. 12-15.