The first domestic speaker system that meets the requirements for Hi-Fi equipment (the initial letters of the English words high fidelity - high quality, high fidelity of sound reproduction) was the "S-90" 35AC-012 speaker system: three-way, bass-reflex type, 30GD-1 loudspeakers are used , 15GD-11, 10GD-35. On the basis of this model, acoustic systems 35AC-016 (with a bass reflex), 35AC-018 (with a bass reflex), 35AC-008 (closed), 35AC-015 (with a passive radiator) have been created. They all have similar parameters and differ in appearance. Currently, this, to some extent, has ceased to satisfy the needs of fans of high-quality sound reproduction. Considering the fact that the current market offers a fairly wide range of expensive modern acoustic equipment, but not always of high quality, we will consider options for modifying a pair of acoustic systems "S-90" 35AS-012, produced in 1985 by the Riga Radio Plant named after A.S. Popov, equipped with newer, at that time, developments of LF, MF heads - 30GD-2 and 15GD-11A. The schematic electrical diagram and the layout of the AC filter parts are shown in Figure 1.

Fig. 1. Electric filter of the acoustic system "S - 90" 35 АС-012: a - electrical circuit diagram; b - arrangement of elements on the board

Capacitors C1, C2, C4-7 used tapa MGBO-2, C9, C8 - K73-11. The filter elements are mounted on 12 mm plywood with dimensions 210 x 160 mm. The inductors are installed in a horizontal position and, moreover, L1, L2 and L3, L4 are close to each other, respectively. The filter itself is mounted on the rear wall inside the speaker cabinet behind the woofer.

Housing

The protective grilles of the heads and the heads themselves, the filter and other elements, which will restrict access to the inner surfaces of the walls of the case, are carefully removed. Leakage prevention is carried out. The joints of the walls and the seats for the woofer, midrange speakers are coated from the inside with a silicone sealing mass. Seal with silicone (if necessary) the gaps between the rear, side, bottom and top walls from the outer side of the case, having previously cleaned them from dust, dirt and glue. In order not to stain the veneer finish of the case with sealant, it is closed around the cracks with paper construction tape. Excess sealant is removed. After it has hardened, a shallow cut is made with a sharp knife under a metal ruler along the edges of the tape, in the places of its conjugation with the sealing compound. The tape is removed. The sealant is used to match the body color or transparent.

Among many radio amateurs, the S-90 is being finalized, a common means of combating panel vibrations is to increase their rigidity by using additional "stiffeners" (strips), spacers, etc. They also additionally cover the inner walls with a sound absorber. This is not always justified, since such measures lead to a decrease in the internal volume of the case, which, in turn, reduces or even excludes the efficiency of the phase inverter.

A simple increase in the stiffness of the walls by using additional "stiffeners" or thickening of the panels only increases the resonant frequencies of the panels and changes the distribution of their vibrations and radiation, as the number of vibrating surfaces and their dimensions change. The thickening of the panels also increases the weight and cost of the decoration. Therefore, for the manufacture of decoration, it is more expedient to use materials with increased internal losses of vibrational energy during their deformation (increased "internal friction"), as well as a sufficiently high elasticity. Such materials, called vibration damping or vibration damping, can be applied to conventional panels. Vibration-absorbing materials convert some of the vibrational energy of vibrations into heat and increase the mechanical resistance of the panels, thereby reducing the amplitude of vibrations. Vibration damping is especially effective at resonant frequencies, when the amplitudes of vibrations and deformation due to bending or shear increase. The use of a vibration-absorbing coating on the panels of acoustic design leads to an increase in the overall rigidity of the panel, and therefore it seems possible to reduce the thickness of the panels by 1.5 - 2 times without fear of an increase in their vibrations. Therefore, a self-adhesive vibroplast with a thickness of 1.5 - 2 mm is applied to the inner surfaces of the walls of the modified speakers (flexible and elastic vibration-absorbing material, which is a self-adhesive polymer composition duplicated with aluminum foil, Fig. 2, is used to reduce the vibration of car body parts).

Fig. 2 Vibroplast

For a perfect fit to the surface of vibration-insulating materials, the walls of the case must be prepared from the inside. Namely, sand with medium-grain sandpaper and prime with, for example, nitro varnish or PVA glue. After that, the necessary blanks are marked and cut out from a piece of vibroplast (on some materials there is a special marking in the form of molded squares 1 x 1 cm, which makes it possible to do without a ruler and marker). Bend the corner of the protective film on the workpiece and apply it to the intended place. Attach the edge of the material to the surface and gradually, gently smoothing it, while removing the film, stick the entire piece. The material is finally rolled with a roller, having achieved maximum fit.

The sound-absorbing coating increases the sound absorption of low frequencies up to 500 ... 1000 Hz. Sound absorption should be proportional to the surface area of \u200b\u200bthe coating. If you attach it not close to the walls of the case, but at a distance of 20 - 50 mm from them, then the sound absorption at frequencies below 500 Hz increases. This condition is fulfilled by the manufacturer 35AC-012 - mats with cotton wool are located in sufficient quantities at some distance from the walls (approximately in the central part of the box). Therefore, additionally covering the walls with a sound absorber is not only useless, but also harmful. Cushions or cushions made of sound-absorbing material suspended in the geometric center of the speaker give the same results as placing it on the sides of the box.

Fig. 3. Sealing the seams of the bass reflex tunnels

The design of the port of the 35AC-012 phase inverter has the shape of a curved tunnel with an unusual cross-section. This is due to the goal of satisfying the following conditions: rigidity and lack of resonant overtones in the port material. It consists of two glued plastic parts. The places of gluing are looked around. The cracks found during inspection are poured with dichloroethane. After that, at these points, both parts of the bass reflex port are tightened with clamps and dried - Fig. 3. It will also be useful to paste over its walls with vibroplast strips. After such processing, the plastic of the port becomes hard and deaf. It is recommended to install an acoustic impedance panel (PA) at the output of the bass reflex port. This technical solution, protected by the USSR author's certificate No. 577699, makes it possible to reduce the acoustic Q-factor of the loudspeaker head several times. An acoustic system with such a PAS sounds more natural, without "mumbling".

Weakest link

The frequency response of the mid-frequency dynamic head 15A - 11A has a sharp drop above 4.5 kHz - Fig. 4, a, the acoustic Q-factor is about 11.8. And the higher the quality factor of the oscillatory system, the more it emphasizes the frequencies that coincide with the resonant ones, or close to them. That, in practice, excludes the possibility of obtaining a full-fledged undistorted sound when you turn it on through a midrange bandpass filter, if you do not take the necessary measures. To eliminate the first drawback, the following technique is used.

Fig. 4. Mid-frequency dynamic head 15GD-11A (20GDS-4-8): a - frequency response of sound pressure; b) - dimensions and installation dimensions

Soak the dust cap of the head with nail polish remover, you can use solvents 646, 647 and others. Carefully remove it with a scalpel (Fig. 5, b). Remember that due to the strong action of the field of the magnetic system on the steel instrument, careless movements can damage the speaker elements! Next, wipe the glue diffuser with a cotton swab dipped in the same nail polish remover. The lower part of the speaker and the upper part of the voice coil are coated with Moment glue. Dry for 10 - 15 minutes. Again, coat both parts and immediately connect them, slightly pressing (Fig. 5, e). Horns are installed both new and removed, in the above way, from old speakers (Fig. 5, c).

Fig. 5. Bonding a horn in 15GD-11A: a - dynamic head 15GD-11A; b - removing the dust cap; c - dynamic broadband head 10GDSH-1-4 (10GD-36K); d - high-frequency horns 10GDSH-1-4; e - stages of fitting the horn for 15GD-11A

The glued horn is designed for the dynamic head 10GDSH-1. For our case, it should be adjusted. Fitting consists in cutting it, while measuring the frequency response of the speaker. To do this, place the speaker on the same axis with a microphone (preferably a measuring one), within 40 - 50 cm, in a room no closer than 1 meter from walls, furniture, etc. The microphone is connected to the corresponding port of the computer video card, and the speaker to the amplifier computer speakers. Launch RightMark 6.2.3 software and measure the frequency response. Cut off the edge of the horn, about 1 cm. Measure the frequency response and compare it with the previous one. The operation is repeated until you get the most even frequency response in the mid-frequency aisles, thereby increasing their range to 10 kHz (Fig. 6).

Fig. 6. Frequency response of the 15GD-11A head with an additional high-frequency horn

The second and subsequent cuts should be done very carefully, cutting no more than 3 mm. As a result, the lateral surface of the horn inside was about 7 mm (from the dust cap to the edge of the trim) - Fig. 5, e. Trimming is performed with nail scissors, since they turned out to be the most acceptable tool for this type of work, they have miniature rounded cutting surfaces. The cut edge, to give rigidity, is impregnated with BF-2 glue with slightly diluted ethyl alcohol.

To eliminate the second drawback, acoustic damping of the head with the help of PAS is used. Damping the heads with sound-absorbing material is less effective and, moreover, increases the resonant frequency. In order to increase the efficiency of the PAS action on a moving system operating in the acoustic design of the head, the damping tissue should be placed as close to the diffuser as possible. It is most rational to arrange PAS in the holes of the diffuser holder. For this, eight identical elements are cut out of thick cardboard approximately 2 mm thick (Fig. 7, a). The total area of \u200b\u200bthe holes for the 15GD-11A head should be 22 ... 28 cm 2. One side of each element is lubricated with glue for a moment. After 5 minutes, glue it onto a stretched cotton fabric using an embroidery hoop. After 30 minutes, the fabric is trimmed around the elements. The PAS elements are slightly bent and glued into the windows of the diffuser holder (Fig. 7. b). The gluing points are additionally coated with glue. It is important that the fabric in the holes of the elements be stretched, otherwise there will be no effect from the use of PAS! The use of PAS, i.e. acoustic damper, allows you to slow down the natural vibrations of the diffuser, as a result, the "decay" time will be significantly reduced and the sound quality of the speaker will noticeably increase.

Fig. 7. Head 15GD-11A: a - PAS element; b - PAS in the windows of the diffuser holder

The damping effect of the PAS for the dynamic head 15 GD-11A is graphically presented in Figure 8.

Fig. 8. Damping effect of PAS for 15GD-11A head

The effectiveness of the use of PAS was checked by the employees of the Berdsk radio plant. In particular, the harmonic coefficients of the 15GD-11A mid-frequency head with PAS and without PAS were measured. The measurement results shown in Table 1 show that PAS can significantly reduce the harmonic distortion in the frequency range in which the human ear has the greatest sensitivity.

Table 1. Coefficients of harmonics of the 15GD-11A head

frequency Hz	Harmonic coefficient,%

To restore elasticity, a rubber-fabric suspension is impregnated with the "Conditioner and tensioner of drive belts" aerosol. After such a refinement, the frequency range of the head increased significantly, up to 10 kHz (!), The linearity of the frequency response of the sound pressure improved and, most importantly, the sound quality of the speaker system as a whole.

Separation filters

In passive crossover filters, their design plays an important role, as well as the choice of specific elements - capacitors, inductors, resistors, in particular, the mutual placement of inductance coils has a great influence on the characteristics of AC with filters; closely spaced coils. For this reason, it is recommended to arrange them mutually perpendicular, only this arrangement allows you to minimize their influence on each other. Inductors are one of the most important components of passive crossover filters. It is not recommended to place the coils closer than 100 mm to each other. The simplest way to modify the filter 35АС - 012 (Fig. 1, b) is to reinstall the coils L1 and L3 perpendicular to the base and to each other. For such an arrangement, plastic corners are used, cutting out of the cases of old equipment or boxes. Pay particular attention to the base material on which the filter parts are located. It must be dielectric! In some speaker systems, 35АС-1, "S-90" 35АС-212, predecessors of the "S-90" 35АС-012, the filter parts are mounted on a steel plate, the magnetic properties of which negatively affect the inductance coils and, of course, sound quality.

The high-frequency head 10GD-35 is shunted with a notch filter tuned to its fundamental resonance frequency of 3 kHz. It is a high Q serial LC circuit. The capacitance of the circuit capacitors is 6.6 μF (MBGO and MBM with a permissible deviation from the nominal value of ± 10%), the inductance of the coil is 0.43 mH, its winding contains 150 turns of 0.8 mm PEV-1 wire wound on a frame with a diameter of 22 and a length 22 mm with 44 mm cheeks diameter. The use, for these purposes, of the filter elements of the acoustic system 10АС - 401 will significantly reduce the costs and labor intensity of the work. The product of the capacitance of the capacitor in microfarads by the inductance of the choke in mH should be equal to 2.82 (http://www.radiolamp.ru/acoustics/3/). If 2.82: 6.6 \u003d 0.43 mH, then for a circuit with an inductance of 0.5 mH, it is easy to calculate the capacitance of the capacitor: 2.82: 0.5 \u003d 5.6 μF. You just need to select capacitors to the required capacity - 5.6 μF.

Another refinement option is unwinding from the inductor with a value of 0.5 mH, extra turns to the required 0.43 mH. It is convenient to use the RLC meter. In place of the resistor of the filter of the acoustic system 10AC - 401 (previously removed as unnecessary), a capacitor of 2 μF is reinstalled, and in its place, a 4 μF capacitor of the same type - MGBO - is attached. The MBM capacitors are soldered to the terminals of the capacitors to set the capacitance of the required value of 6.6 μF (Fig. 9). As a result of the described revision, they get rid of overtones, bounce and characteristic "hissing" of the 10GD-35 head.

Fig. 9. The filter of the acoustic system 10АС - 401, converted into a rejection filter for the HF head 10GD-35

Conductors

The cable between the loudspeaker and amplifier contributes to the sound of the system. Mainly due to the fact that the cable has a certain resistance. The influence of this resistance not only affects the sensitivity of the speaker, but also affects the power distribution between the emitters in the column. To eliminate this effect as much as possible, the cross-sectional area of \u200b\u200bthe wire should be as large as possible and the length as small as possible. In addition, it is necessary that the length and cross-section of the wire are the same for all speakers. Also, one cannot exclude the fact that the conductor has a certain inductance, and two closely spaced conductors form a capacitance. Therefore, the twin wire can be thought of as an LC low pass filter. That is, the longer the wire, the more high frequencies will be damped. In practice, the influence of the inductance of the wire is manifested only when the cable length is over 50 m. Also, when a high-level low-frequency audio signal flows through the acoustic wire, a strong magnetic field is formed around the cable conductors. This field affects the mid and high frequency audio currents flowing through these conductors, making the sound of the loudspeaker less clear and transparent. The solution to these problems is to ensure the flow of currents of low-frequency components of the signal and currents of its medium-, high-frequency parts along physically separated conductors. To do this, an additional pair of sockets (screw clamps) is installed in the speaker system, to which the input of the filters of the mid-range and high-frequency speakers is connected. Thus, the input of the low-frequency loudspeaker filter is connected to a separate pair of input terminals. This connection is called bi-wiring, i.e. in two pairs of wires to one speaker. The use of two- and three-pair communication cables with a load can significantly reduce the overall cross-section of the conductors without increasing the mutual influence of the loudspeakers. Such acoustics with a double set of terminals can also be connected to separate amplifiers, which will already be called "bi-amping", i.e. two amplifiers per channel. In the latter case, they also get rid of the electrical interaction of the sections of the emitters. Instrument screw terminals are used as screw terminals. Stud material - brass, thread - M6 x 0.5, lamb is covered with ABC plastic.

The most important criterion for choosing a conductor for a speaker is its electrical power. The electric power P supplied to the loudspeaker is understood as the power dissipated at a resistance equal in value to the nominal electrical resistance R n, with a voltage equal to U at the loudspeaker terminals: P \u003d U2 / R n. In the practice of designing domestic speakers, two types of power were usually used - nominal (electrical power limited by the occurrence of distortions exceeding a given value) and passport (the highest electrical power at which a loudspeaker can satisfactorily operate for a long time on a real sound signal without thermal and mechanical damage, usually 1.5 ... 2 times higher than the rated power). According to the technical documentation "S-90" 35AS-012, rated power R nom. \u003d 35 W, passport R passport. \u003d 90 W. The manufacturer of these types of dynamic heads allows their operation with a voltage not exceeding 11 volts. In this case, the current I flowing in the voice coil of the low-frequency head will be 2.8 A, and in the voice coil of the midrange of the loudspeaker - 1.4 A. To calculate the cross-section of the conductor, it is necessary to proceed from the indicated current values.

Note. The calculation is carried out in a simplified form, provided that there is only an active resistance in the circuit, at which the cosine of the phase shift angle of the current and voltage φ is equal to zero. In a real electrical circuit of a loudspeaker, there are always inductive and capacitive resistances, called reactances, which introduce temporary changes in the values \u200b\u200bof current and voltage.

Musical works have a variable character, both in signal level and in frequency, therefore, a current of 2.8 A can theoretically occur, but not constantly and in very short sections of the musical path, for example, when a bass drum is "thumping". Internal installation "S-90" 35АС - 012 is made of tinned copper stranded wire in PVC insulation with a cross section of 1 mm 2, which corresponds to the calculated data, since the current density in the copper conductor becomes 6 - 10 amperes per square millimeter. Note that the voice coils of the loudspeakers are wound with a much smaller wire: 30GD-1 - 0.1 mm 2, 15GD-11A - 0.02 mm 2, 10GD-35 - 0.005 mm 2. The total cross-section of all the coils is 0.125 mm 2, eight times thinner than the inner AC hooking wire! In the power supply circuits of power amplifiers of the "S-90" era, with a rated power of 25 to 50 W per channel, fuse links (fuses) for a current of 2 to 3 A were provided, and this, first of all, for powering the circuit and then the load.

The real sound signal is impulsive in nature. On a signal with steep edges, even at frequencies of the audio range, the skin effect (from the English skin - outer layer, sheath) is largely manifested - the effect of displacing current to the surface of the conductor, which leads to an increase in the effective resistance of the connecting cables. ...

Low-frequency signals propagate practically throughout the entire volume of the conductor, while high-frequency signals propagate mainly in a thin near-surface layer. This skin effect dramatically increases the resistance of the conductor and slightly decreases its inductance. Figure 10 shows the frequency dependence of the impedance of copper conductors of various diameters with a length of 1 m.At f 100 kHz, inductance plays the dominant role. Copper wire with a diameter of 0.16 mm up to a frequency of 20 kHz does not change its resistance, but has a relatively large value, almost 1 Ohm. The use of several insulations of conductors with a diameter of no more than 0.16 mm will allow the use of several insulations of conductors with a diameter of no more than 0.16 mm to significantly reduce the resistance of the conductor and leave it unchanged in the entire audio frequency band. A bundle of enameled wires intertwined in a special way (from it. Litzen - strands and Draht - wire) is called litz wire.

Fig. 10. Frequency dependence of the impedance of copper conductors of circular cross-section with a length of 1 m

Thus, speaker cables should not only have minimal resistance and inductance, but also have minimal skin effect. Connecting loudspeakers, especially MF - HF, is best done with litz wire or copper wire covered with a thin layer of silver. Silver has the highest conductivity among all metals, and its thin layer, in which, due to the skin effect, and most of the current flows, has a strong effect on the resistance of the conductor.

When choosing a mounting wire, it is also necessary to take into account the principle of connecting acoustics through 2 pairs of contacts, which, of course, proportionally distributes the power between the LF and MF - HF channels. With equal head sensitivity, the maximum noise (passport) power at the crossover frequency, in our case, 500 Hz for the LF channel is 56% of the total power, and for MF-HF - 44%. Between the midrange and high-frequency heads, the power at a cutoff frequency of 5000 Hz is distributed by 41.5% and 2.5%, respectively. Such division of power cannot be considered unconditional, but gross errors in calculations can be avoided. The speaker heads differ both in sensitivity and in the value of the nominal electrical resistance (Table 2). The difference in each of these parameters leads to the need for an appropriate selection of the voltage supplied to the head in order to obtain a uniform frequency response with respect to pressure. And the voltage supplied to the head is one of the dominant indicators affecting the power.

Table 2. The main parameters of the heads used in the acoustic systems "S - 90" 35АС - 012

Head name according to GOST 9010-78

According to OST 4.383.001-85. Modern counterpart

Limiting noise (passport) / limiting long-term / limiting short-term power, W

Rated power, W

Nominal resistance, Ohm

Frequency range, Hz

Frequency response unevenness, dB

Standard sound pressure, Pa

Main resonance frequency, Hz

Typical sensitivity level, dB / mW

Overall dimensions (in plan), mm

Height, mm

Weight, kg

Note. The information about the parameters is taken from many sources, not always exhaustive, and sometimes contradictory (indicated in brackets).

It should be noted that, in home acoustics, the effect of conductors on sound quality is negligible compared to other factors. Attention should be paid to more important elements, the acoustic properties of the room, the correct placement of the equipment. Information about the exclusivity of cables made of oxygen-free copper, from wires with the "orientation" of the surface layer of the conductor, which affects the passage of a sound signal in one direction or another, is nothing more than advertising.

Electrical part of the modified system

The schematic diagram is shown in Figure 11, a. The filter uses capacitors with a maximum operating voltage of 160 V: K73-11 (C1, C10, C11); K73-16 (C2-4); MBGO-2 (С5 - 9); parallel connected MGBO-2 and MBM (S13). Installation is carried out with a single-core copper wire with a cross-section of 1 mm 2 (extracted from the communication cable with air insulation of each core) and MGSHV wire (flexible stranded, conductive conductors of tinned copper wire, wrapped in insulating silk with PVC insulation, for intra- and inter-unit installation of various electronic equipment and devices for rated voltage up to 1000 V AC, frequency up to 10 000 Hz), with cross-sections of 1.5 mm 2 (for the low-frequency link) and 0.5 mm 2 (only in the filter of the MF - HF link). The connection between the terminals, the divider, the filter and the high-frequency head is carried out with a wire LEPShD 500 x 0.05 (a round wire of 0.98 mm 2 with a core twisted from 500 copper wires with a diameter of 0.05 mm, insulated with a polyurethane varnish, with a two-layer a winding made of natural silk, recommended for the frequency range 250 ... 500 kHz, with a specific electrical resistance, at 20˚C, 0.0158 ... 0.018 Ohm / m). The playback level control does not have to be connected.

Fig. 11. Electric filter of the acoustic system "S - 90" 35 АС-012 after revision: a - electrical circuit diagram; b - arrangement of elements on the board

All elements are placed on the plywood of the native filter "S - 90" 35 AC - 012, (Fig. 11, b). Particular attention should be paid to the relative position of the inductors. Parts must be rigidly secured. The connections are made with wires as short as possible, without allowing them to sag. The filter elements must not touch. If necessary, for tight installation, use a sealant, screeds, insulating tape, etc. Otherwise, as a result of vibrations of the housing and air vibrations inside the speaker, the filter parts will rattle and emit unpleasant sounds. The filter is attached to the bottom wall inside the case, thereby minimizing the effect on the inductance coils of the magnetic field of the woofer.

Installing the speakers

Before installation, first of all, the bass and treble heads (the midrange head is already normalized) are inspected for the integrity of the structures, especially in the places of gluing, the absence of mechanical damage to the parts, the integrity of the suspensions of the woofer. It can be rubber or polyurethane (35AC - 018). The suspension, made of not very high quality rubber, hardens over time. Polyurethane is destroyed by sulfur impurities in the air. The problem of suspensions is eliminated by replacing them. An alternative solution for an intact rubber suspension is to soak it with conditioner and belt tensioner. Replacing suspensions is a very laborious job that requires some knowledge and skills. Places of peeling of the centering washer or suspension from the diffuser holder are coated with glue with the simple name 88, after which the surfaces to be glued are pressed. It is also necessary to make sure that there is no contact with the voice coil of the elements of the magnetic system. The diffuser's appearance is restored by simply staining it with a black marker filled with alcohol ink (it says "alkohol"). Some "refiners" use printer ink. This is not the right decision, since it has the properties of quick burnout and flushing with ordinary water. The acoustic lens is removed from the tweeter head to release the domed voice coil cone. Remove it carefully and make sure that the voice coil is intact. Very often, its turns are separated from the frame during operation. If this defect is found, the voice coil diffuser is replaced with a new one. For prophylaxis, the voice coil is coated with BF-2 glue, slightly diluted with ethyl alcohol. It is advisable to test the heads with the measurement of the frequency response of the sound pressure. Loudspeakers that cannot be repaired are replaced with new ones.

Another effective way to reduce vibrations, and therefore unwanted overtones, is to "soft" mount the heads. They are mounted on rubber gaskets. It is necessary that the fastening elements do not come into contact with the diffuser holder. To do this, select a tube of the required diameter, for example, PVC, with a snug fit to the walls of the speaker mounting holes, while ensuring free entry of the screws. If necessary, the holes are reamed to the required size. Rubber washers are also placed under the nets with decorative rims in the places of the holes. It should be noted that the bass and midrange heads are mounted in recesses. Therefore, it is necessary to put rubber bands in four places around each speaker, for example from a bicycle tube, to prevent the side parts of the diffuser holders from touching the case.

Facing and decorative elements have a significant impact on the frequency response of the loudspeaker. The decorative material that closes the bass reflex opening, especially the passage, can have a significant impact due to the high oscillatory air velocities. Grilles and louvers can sometimes cause resonance phenomena and additional peaks and dips will appear in the loudspeaker's frequency response. The front part of the 10GD-35 head, around the acoustic lens, is pasted over with felt or dense cloth. This will ensure both its soft attachment and minimization of diffraction, the manifestation of the effect of reverberation of sound waves, which, in turn, will weaken the resonance phenomena between the head and the grating. The 35AC-1 speaker system has a removable decorative panel. In the technical documentation specified by the speaker, it is recommended to remove the panel when listening to high-quality programs, when working at the maximum permissible power. Figure 12 shows the graphs of the frequency response of the sound pressure of the 15GD-11A and 10GD-35 loudspeakers in the open version (white curve) and closed with decorative nets (green curve) provided by the design of the "S-90" 35AC-012 speaker system. There are no significant differences. Conclusion: in this device, there is no special need to remove protective decorative grids, since their presence does not affect the frequency response of the heads in the operating frequency range. You should be guided by subjective assessments after listening to a real sound signal through a speaker system with or without decorative nets.

Fig. 12. AFC of the sound pressure of the loudspeakers: a - 15GD-11A; b - 10GD-35

The described method of finalizing the sound speakers "S - 90" 35 АС - 012 will be useful for altering speakers and other models, as well as making speaker systems with your own hands.

Literature

1. Aldoshina I. High-quality acoustic systems and emitters, Moscow: Radio and communication, 1985.
2. Ephrussi MM Loudspeakers and their application - M .: Energiya, 1976. - 64 - 66 p.
3. Young N. Acoustic damping of loudspeakers. Radio, No. 4, 1969.
4. Sysoev N. Improving the sound 35AC-012 (S-90). Radio, No. 10.1989.
5. Burko V. Household acoustic systems. Operation, repair - Minsk: "Belarus", 1986.
6. Maslov A. Once again about the alteration of the loudspeaker 35AC-212 (S-90). - Radio, 1985. No. 1, p. 59.
7. Popov P. improving the sound quality of loudspeakers - Radio, No. 6, 1983.
8. Shorov V. Improving the sound of the loudspeaker 25AS-309 - Radio, No. 4, 1985.
9. Gorshenin D. Comparison of capacitors in the AC crossover. Radio, Nos. 8, 9, 10, 2009.
10. Kunafin R. And again 35AS ... - Radio, 1995, 5, p. 19, 20.
11. Afonin S. Creation of acoustic systems at home - M .: Eksmo, 2008.
12. Bystrushkin K. Acoustics with which we live. "Stereo & Video" N 11 1997.
13. Petrov A. Sound circuitry for radio amateurs, St. Petersburg: Science and Technology, 2003.
14. Brans J. Electronic design: methods of dealing with interference, M .: "Mir", 1990.
15. Sapozhkov M. A. Acoustics: a reference book - M .: Radio and communication, 1989.

Date of publication:05.02.2015

Readers' opinions

• Vladimir / 12/14/2018 - 01:17
  Good day everyone! Today, luck smiled at me! I stumbled upon your article and realized, I went on a quick path. I have never, professionally, been engaged in radio electronics, but it was useful to improve. I used articles which are full in the net and are not backed up by deep knowledge. Vladimir, I have a not very modest request for you. I will leave my phone number (0675202057), please drop an SMS with info that will give you the opportunity to communicate with you. If, of course, you have the opportunity and desire. It is easier for me, an amateur, to explain the essence of the problem. Thank.
• [email protected] / 10.09.2018 - 07:31
  Dear author, hello friends! I have had an S90 since 1982 and only now realized that they are buggy, medium and high. I spent the evening, it was found that 2 technological errors were made during the assembly of the speaker: The first one is the most intricate, the 15GD-11A is placed in a cap, its rear is sealed and it does not breathe, hence there are so many complaints about this speaker, everyone changes it to something else. IT'S SIMPLE! under the midrange speaker from the back, place 4 bushings with a height of 5 mm (you can use 4 nuts per 10). Glue the nuts on the plate and then install the midrange speaker and it will sing perfectly and will not interfere with the tweeter head. Remove ALL props from the HF head on the front side, the grid is for some reason made of steel and attracts the HF speaker magnet (this is not correct). Eliminate these 2 technological mistakes of manufacturers and YOU will tell. What wonderful designers have come up with S90 !!!
• Author / 25.07.2018 - 18:35
  Sorry, part 4 at the following link: http: //www..html Part 5 is under construction, coming soon.
• Andrey / 07/23/2018 - 23:33
  And where does the 5th part come from? If there are only 3 parts of the revision 35ac-12. Maybe I missed something, post a link about part 5.
• Author / 07/23/2018 - 19:19
  Follow the recommendations from the 5th part of the article on replacing elements and their interposition. A notch filter can be installed in the high-frequency part of the filter. If you will not modify the midrange head, then perhaps that's all.
• Andrey / 07/22/2018 - 23:57
  Good day. I have this question. There are Orbit 35as-016 columns with regulators. I can send photos as located inside the filter. How and what can I improve. I can hold a soldering iron. And a bit to read the diagrams. Can someone tell me what to do and according to what scheme. Thank.
• Rush / 05/26/2018 - 02:42
  Fine! Only pasting the case with a 3mm vibration isolator has already made the sound cleaner and more pleasant. What's good is that the S-90f has already removed everything that can be in the filter. It remains to make a PAS for the counter .. I pasted this thing https://www.ulmart.ru/goods/3774803. The result is very noticeable and pleasing. Thanks you!
• Alexander B. / 05/22/2018 - 15:44
  Thank you for your reply.
• Author / 05/22/2018 - 15:17
  Aldoshina I. in her book noted that additional stiffening ribs and struts do not eliminate resonances, but distribute them over new surfaces of the same stiffeners and struts. But the application to the surface of the walls of a material with increased internal friction allows you to use the material for walls of smaller thickness. In fact, the vibroplast virtually thickens the walls, thereby reducing unwanted resonances. Making a PAS for the midrange head is the first thing to do. The game is worth it.
• Alexander B. / 05/21/2018 - 15:48
  Vladimir, good afternoon. Thank you for your article. I would like to consult with you and ask a few questions. I have an S-90F (91g.) After reading your article, I decided to also improve the system, but since I am not an electronic, to a minimum. 1. Paste with vibroplast, seal the slots 2. Saturate the speaker suspensions with air conditioning 3. Make PAS on the midrange 4. Replace the capacitors to newer ones with the same rating (without changing the filter circuit) 5. Replace the acoustic terminal 6. Put on spikes. In this regard, the question 1. Should you put a spacer between the rear and front walls? 2. Is it possible to make a PAS on the midrange and not change the filter circuit (I am not friends with this)? Is the game worth such a minimal improvement?
• Author / 05/16/2018 - 20:52
  Two native cotton mats are enough.
• Victor / 05/16/2018 - 20:11
  Greetings, Vladimir. In the process of working on the columns, a question arose. Maybe it is worth covering over the vibroplast with a thin felt (1-1.5 mm) or batting in 1 layer? And then something confuses the "aluminum" inner surface of the box.
• Author / 04/01/2018 - 13:46
  Probably to weaken the resonance phenomena in the oscillatory circuit, the coil-capacitor and equalize the frequency response. There is a whole article on the use of resistors in a filter in conjunction with coils and capacitors.
• Anton / 03/31/2018 - 18:35
  Hello! Please tell me why you need a 75 Ohm resistor R1 (in some circuits 100 Ohm), which is parallel to the L2 coil in the high-frequency head filter? Do I have to put it?
• Author / 03/29/2018 - 09:09
  It is enough to cover the suspension on one side, evenly, avoiding drips. The diffuser, of course, needs to be closed. Find coils from 35AC-212 (012) and wind to a tedious size - it will be easier, better and more reliable.
• Yuri B. / 03/29/2018 - 08:33
  As for the coil, I am working on the options from what I have: there are two sound speakers from the tube TV, but the cross section "w" of the core is more than about 5-6 cm2. Wire from the OS of the same body. but it seems to be thinner. Alternatively, is it possible to connect two coils in series 2.5 + 0.25 \u003d 2.75 if I find the same crossovers? And the question about the air conditioner is to handle suspensions on both sides and you probably need to cover the diffuser (cut out a circular template from paper or cardboard)?
• Author / 03/28/2018 - 15:46
  Resistors can be connected in series or in parallel. In this case, the total power is equal to the sum of the powers of the resistors used. If you decide to modify your speaker system according to the methodology from the article of the magazine Radio No. 4 for 1985, then in the diagram in fig. 3, it is necessary to install a resistor R3 with a nominal value of 15 Ohm - this is to attenuate the signal of the 6GDV-4-8 head twice (i.e., by 3 dB). I wonder where you will get the L3 Coil?
• Yuri B. / 28.03.2018 - 10:53
  Dear Vladimir, many thanks again! You probably confused me with another Yuri, who stands before me in correspondence with you. About the failure of the frequency response, you probably had a conversation with him. To clarify, I added the letter "B". I have a question, can I add a resistor in series, or else I don't have a 10 ohm type PEV? And the second question is whether the filter should be upgraded in the future according to your recommended article by J.Radio 1985 # 4 (you have a misprint not for 1984). I really liked it - the cutoff border of the low-frequency device goes down. Of course, I will carry out the modernization in stages, comparing it with another column (I put music of different genres and the balance alternately left and right). And the question for the future - on Arcturus 004 there are a couple of second outputs for the AC - never used. How would you advise to use it? Maybe you can make a separate entrance for the same 25AC309? Best regards, Yuri B.
• Author / 03/27/2018 - 19:59
  In the 25AC-309, the filter for the midrange head has a cutoff frequency of only a low frequency. There are no restrictions on the upper frequency range. What do you want to promote? The sensitivity of the 6GDV-4-8 head is two times higher (by 3 dB) than that of the 5GDV-1. Therefore, the signal must be attenuated by half. To do this, the resistor R3 (5.1 ohms) is replaced with a 12 ohm resistor or close to it. If your circuit has a resistor R3 of 3.3 ohms, then replace it with 10 ohms. That's the whole revision. Observe the polarity of the connection of the heads. You wrote about a 3000 Hz dip. If you measure two heads at once, MF and HF, then a failure occurs when they are incorrectly connected. Reverse the polarity of the RF head connection.
• Yuri / 03/27/2018 - 17:40
  Vladimir, thank you so much! Tell me about the modernization of the filter. Do you need to increase the cutoff band of the midrange? What changes should be made based on the details of the old filter is desirable. And how to tie a new tweeter? Maybe it's convenient for you to drop it to my email. -I will write. Regards, Yuri.

1

1. Small enclosure volume for woofer. The consequence is the bubbling of low frequencies.
2. The phase inverter is designed for a frequency of 20 Hz. Consequence - large distortion of low frequencies.
3. Useless midrange speaker. Consequences - disgusting midrange, overtones.
4. Low tweeter resonance. Consequences - "quacking", hissing.
5. The filter is designed taking into account the previous disadvantages. Consequence - when modifying any node, the filter must be changed.
6. The body is not rigid enough and is not "damped". Consequences - vibrations, overtones, "barrel".
7. Etc. etc. ...

We study and dare

Drinking beer, we come to three truths. There are three ways:

1. Lightweight and efficient.
2. Medium difficulty. More shamanism and snobbery. Some sound improvements over item 1.
3. Super complex, time consuming and super efficient. In reality, you are trying to make new speakers. It all depends on the quality of workmanship and musical flair. If nothing works out, then no one promised you anything.

Attention! Attention! Attention!

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

The first way. Lightweight and efficient.

1. Mids are the main focus. By altering the speaker, we will achieve its operation in the piston mode, increase the upper cutoff frequency, remove overtones, increase the sensitivity, improve directivity, and damp.
2. Let's translate the column into the range from 31.5 Hz, instead of 20 Hz. Mumble less.
3. Let's set the resonance of the high-frequency head.
4. Calm down the overtones of the body

We buy a Soviet tennis ball in the store. Chinese and others are not suitable. They have different material. The ball should be exactly the same as in the distant 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 started. We saw the ball in half along the seam. The seam is visible in the light. It is made with an overlap and is 1 - 2 mm wide. You need to cut in the middle of the seam. I sawed with the blade of the Neva, having previously made notches on it with a sharpening bar. After sawing, align the cutting line on sandpaper, and sand the outer surface of the ball with fine sandpaper. If there are large nodules inside in the seam area, then they must also be removed. When working, the ball must be fixed with plasticine on a Mars battery (a case from photographic film, jars of food for fish, etc., according to your imagination) at three points. It's enough. Plasticine is removed by sweat or a dry cloth or wiping with gasoline. After the surface of the ball has been processed, it should not be touched by hands. Rub pencil leads on sandpaper.

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

Putting together a 3 KHz filter. 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 clog your head with unnecessary formulas, the simplest thing is that the product of the capacitance of the capacitor in microfarads by the inductance of the inductor in mH should be 2.82. Suppose the capacitance of the filter capacitor is 6.6 μF (MBGO and MBM with a permissible deviation from the nominal value ± 10%), then the coil inductance is 2.82: 6.6 \u003d 0.43 mH, (the winding contains 150 turns of wire PEV-1 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 this 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 fasten the capacitor and the choke on a piece of fiberboard and solder one lead of the coil to the lead of the capacitor. We solder wires 40-50 cm long to the free terminals.

We disassemble the column. We remove the low-frequency speaker, mid-frequency one, take out the glass from it, remove the high-frequency speaker, remove the decorative cover, remove the phase inverter (on some speakers, the filter will have to be unscrewed). 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. Care must be taken to ensure that there is no non-glued 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 screw the homemade filter onto the back of the speaker (inside) opposite the tweeter. We solder the wires from the filter to the output of the tweeter. Which where - does not matter. We remove the connectors from the back of the speakers and solder the wire from the amplifier directly to the filter. Saw off the phase inverter pipe with a hacksaw for metal 10 cm along the middle line. We wrap the phase inverter pipe and the glass of the mid-range speaker with a layer of gauze and bandage. 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 not enough to complete. Damping the mid-range speakers. To do this, we additionally tighten their diffuser holders with foam rubber rings made from blanks 10x27x355 mm. the ends of which are glued with "Moment" glue butt-to-toe. 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, wrapping it around the wire. It is convenient to fix the bandage with threads. We collect the column. We coat all the perimeters of all speakers with plasticine. It is not worth putting on protective nets, but only on the condition that there are no small children, the wife does not come in with a mop or a vacuum cleaner, and that the speakers will not be transported. We turn on the speakers. We do not know the right. We call our acquaintances. Please drive up with your favorite recordings. Let's listen. We soothe our friends with beer. With a mockery, we notice how the bucks spent on the purchase of foreign trash would be useful to them.

The second way. Medium difficulty.

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

1. Let's improve the properties of the body and kill the overtones and "barrel"
2. Get the best signal flow
3. Enclosure sealing. We remove the influence of the body

So let's go. Strengthen the back wall of the case by placing two strips with a cross section of 3x2cm. 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 point with epoxy. It is necessary to take into account the possibility of installing a phase inverter later. Between the rear and front walls, we install a spacer bar 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 of the "Bison" type or sanitary silicone putties. We glue the entire body inside with felt (batting, padding polyester, 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 the 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 35AS - 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 Ohm. Also, the appearance of the column is changing. Well, if you really want to, then you can. Further. Removing the tone switches. Remove unnecessary resistors R (1, 2, 4, 5, 7, 8, 9, 11, 12). We replace the wires on the installation of the filter with a copper wire with a diameter of 1.2 mm. We replace the wires going from the speakers to the filter, with more track ones. On the low-frequency speaker - stranded - with a cross section of 2.5 - 3 mm2, for the mid-range - 2.5 mm2. For high-frequency - 2 mm square. - single core. All wires are soldered directly to the filter instead of passing through the previous speakers. The filter is installed at the bottom of the column. All wires are placed under the felt layer. 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 into epoxy and grind them. We cover the front panel with self-adhesive wood-like film to match the speaker veneer. We install the speakers. Low-frequency and mid-frequency through rubber grommets. Rubber from window insulation, thin rubber medical hoses, silicone hoses (worse) will do. We process the installed speakers around the perimeter with plasticine or non-hardening window putty (it resembles a bar of laundry soap and is cheap). Checking the sound. We are simply bastard. Moving away all sorts of "Pioner", "Technics", JAMO and ...

The third way. Super complex, time consuming and super efficient.

It is a good idea 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, this is not all, but there is a way out - to go to the workshop and ask to try on what you need to take with you filters, heads, etc. If they ask for a fee for this, it is purely symbolic. You can even order a filter. This, of course, will be more expensive. We take 35AS-212 as a basis with dimensions 710x360x285. It is desirable to have a plywood case, a woofer with a rubber surround, a tweeter with a glass cloth dome. We disassemble everything. We no longer need a mid-range speaker. The enclosure needs to be extended for the rubber-suspended woofer 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:

1. Remove the front panel from the case, so that it can then be used for the matrix for speaker holes in the newly manufactured 100-liter case. From the remains of the buildings, good boxes are obtained for potatoes and a stamp in the cellar.
2. You can try to build on 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 abuse and quibbles about quality. We will consider the second way. So, you can try to get by with a little blood. We make it ourselves, or we order two boxes with tight-fitting walls and lids made of double 10-ply plywood with external dimensions - 380x360x285. In the bottom of the column and in the lid of the box, cut out the same holes approximately 270x210. We glue the box inside with felt. After assembly, this will be unrealistic. 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 bolt heads should sink into the sweat. To fall asleep a little - 10 kilograms of shot will not hurt, we throw a gauze bag with cotton on top. Pre-spill the compound with epoxy with a normal hardener content. Paste the junction with felt. The rest of the body movements with the body, as in paths 1 and 2. Take the mid-frequency head 30 GDS-1. You just need to check them - there is a lot of marriage. Purely mechanical properties. Further. We measure the f resonance of all speakers. You can sign with a felt-tip pen directly on the magnets so as not to get confused and not measure everything again.

It would be nice if the resonance frequency of the paired speakers did not differ much. If the speaker emits extraneous sounds at any of the sound frequencies, then it must either be cleaned or changed if cleaning failed to achieve normal operation. We calculate and make filters for our case. The less inductances, the better. We continue to work with the body. Remove excess resin at the junction. We grind it down. We make two wooden filter boxes. We will fix them on the outside of the back wall. We will solder the wires from the amplifier directly to the filters. And we will pull the wires to the speakers through the speaker connectors. All wires are branded audiophile. Choose the price category yourself. It's just very expensive to take - it makes no sense. It is better to remake the phase inverter for a frequency of 31.5 - 40 Hz. If the dome of the high-frequency head is made of lavsan, then, after removing the cross, it is necessary to coat the suspension and the outer third of the dome with perchlorovinyl. We glue the entire body with self-adhesive foil. For the rest, see path 1 and path 2. With mandatory step-by-step verification - better - worse. The best method, if there is no clear result, is blind listening.

Literature

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

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 former believe that it is worth shelling out a tidy sum for the purchase of 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 savings for expensive acoustics (instead of the required car or apartment), therefore 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 Soviet era, which could not leave indifferent any of its owners. The S90 speakers, the technical characteristics of which 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 ones are the S90 and S90B. There were also the S90i, S90D and S90f models, but they were not widely used and are almost never found today.

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 the speaker electrical overload indicator. The recommended power rating for a high quality amplifier for these speakers is between 20 and 90 watts. It is also worth noting that the "Radiotekhnika" S90, S90B (and other modifications) were the first models of acoustic systems that met international requirements for Hi-Fi equipment.

Design

The casing, in which the S90 speakers are enclosed, is, in fact, a non-separable rectangular box made of precious wood veneer. The walls of the speakers 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 with special elements that increase the rigidity and strength of the structure, but do not interfere with high-quality sound.

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

S90 speakers: specifications

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

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

The rated power of the S90 speakers is 90 watts, while the nominal power is 35 watts. The nominal electrical resistance in this speaker system is at around 4 Ohms, and the range of frequencies available for reproduction 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 weight of the entire system reaches 30 kg.

Speaker layout and connection to a sound source

In order to understand whether it is worthwhile to modify 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 understand it, 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 need to be a pro to figure out how to connect S90 speakers. The main thing is to have at least 20 watts with the amplifier (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 acoustics wires, which must be connected to the terminals on each speaker and on the amplifier. The main condition for the connection is to observe the polarity.

Modification 35АС-012

As it becomes clear from the description above, it 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 modify the S90 speakers with their own hands. And all because the acoustic systems of the "Radiotekhnika" company, assembled more than twenty (or even thirty) years ago, already in those years did not have a high quality of assembly and materials used.

Parsing

In the event that the acoustics were purchased in a second-hand condition and at the moment are well worn by life, it is worth attaching importance to the appearance. To do this, you need to disassemble the S90 speakers, first placing them on their "back".

When removing the speakers, you need to take into account that the tweeter and midrange heads are attached to the body using the same screws as the overlays. The woofer is attached separately, and you need to be very careful not to damage it when unscrewing it.

HF / MF controls are much easier to dismantle than you might think. All you need to do is carefully remove the decorative caps located in the center of each control. After that, using a screwdriver, it is necessary to unscrew the screw that is open to the eye, and remove the regulator handle itself. The plastic lining must be carefully lifted from both sides with flat objects and taken out, and the four remaining screws underneath must be unscrewed. Then you can push the S90 inside the column, not forgetting to unsolder it from the filter.

The cotton pouches 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 must first unsolder the panel with filters from the outlet on the back of the speaker, after that 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 grilles and decorative lining of the speakers are "tired", then it is worth straightening and painting them, having previously sanded and degreased. This will give the speakers a fresh look. The S90 speaker cabinet looses over time and can be reinforced as desired. This will result in a better sound for the woofer.

This can be done 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. In addition, you can glue the inner walls of the case with foam rubber (except for the front one), which will increase the volume of the latter.

Terminals and filter

Knowledgeable radio amateurs advise replacing the standard acoustics connection terminals with universal terminals with gold-plated connectors. The installation place must be lubricated with sealant and the panel with the terminals must be replaced.

Considerable attention should be paid to the sound filter as well. If it was attached to the body with metal screws, then the filter setting will get lost. There are cases when the filter was assembled on a metal plate. This should be corrected by transferring all the nodes to the plywood panel. The circuit of the filter itself could have been changed at the factory 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 evaporated 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 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 midrange speakers - an area of \u200b\u200b2.5 mm 2, for tweeters - an area of \u200b\u200b2 mm 2. 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 computer mouse pads. This is the easiest option. After that, it is worth returning them to their seats and putting decorative overlays and nets.

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

With these simple manipulations, the S90 takes on a new lease of life. The sound quality becomes an order of magnitude higher, despite the low cost. As a result, we can say that if there is no money for expensive acoustics of the 2.0 format, you can use this option and become the proud owner of the time-tested speaker “Radiotekhnika” S90. If it so happens that only half of the speakers are available, do not be upset. After all, it is noteworthy that the S90 speaker, a photo of which can be found on almost any site of acoustics lovers of the USSR times, can work alone and give a good result.

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Modernization of S-90 speakers by replacing standard cases with a labyrinthine design of bass dynamics

Upgrade of the labyrinth design S-90 stuffing squares with cotton wool and sticking on the inner surface of a woolen blanket
At first, only the frontal knees of the labyrinth were pasted over with wool, then the side surfaces too
Ready-made maze 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 the know-how of how to translate the S-90 Radiotechnics speakers, most known to most Russian-speaking people, into labyrinthine buildings. The article is devoted to the most widespread acoustics of the Soviet period that was considered the standard for more than 20 years, which in its first generation was called 35AS-1. And Rogozhin proposes to make speakers with the name "Cheap, Loud and Super Bass" out of 35AS-1 (Radio Engineering S-90)!

Ode to speakers Radio engineering S-90 (35AS-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 Radiotechnika S-90, or did not have one of their modifications made in the mezzanine, in the closet, at home or on the hacienda. 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 vastness of the former USSR. They still work in tens of thousands in the systems of music lovers who feel sorry for throwing them away. in comparison with 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 the S-90 Radio Engineering, they have practically no competitors, and before they were even less so. In the late USSR, in addition to the S-90 speakers, of course, there appeared "clones" ripped off from the best foreign samples, for example - Electronics 100AC063 or 75AC-063. But they were very expensive and not widely used, they could not compete in popularity with the S-90 acoustics. It was almost impossible to get three full-fledged bands from any other speakers with the same power as the S-90, a 10-inch woofer and almost nothing. Now it is even more relevant.

Tens of thousands of these speakers still work in the rooms of young and not so people who are unable to carry out complex projects on expensive imported speaker heads. For obvious reasons, many of our compatriots are in no hurry to abandon the acoustics of Radio Engineering S-90. 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.

And nevertheless we all love to listen to music, we all have a good mood when we want to turn it on "to the fullest." Everyone loves high-quality bass, without which almost any music loses its foundation and most of its emotions. Many styles of music are impossible to listen to without bass. without it, the lion's share of important musical information disappears. The soul asks OOUH! And the low frequencies are actually quite thin thing, in order to adequately sound and make an impression, they ask for large speakers, enclosures and powers. But even with all this (in large speakers like S-90), the bass often turns out to be buzzing, drawn out and indistinct, and does not give us the "buzz" that it should give us. We quickly get tired of such a bass and begin to turn the tone control knobs or switch the equalizer modes on the receiver. And instead of getting pleasure - to get irritated 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.

Bass problems S-90

The reason that over the past 30 years the owners of the S-90 radio engineering acoustics and its numerous modifications are not satisfied with its sound and somehow they are 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 in the design of the low-frequency design of the 30GD-2 speaker. Having gone into the series, the error led to the fact that the potential of high-quality low frequency reproduction, originally laid down 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 S-90 owners, almost from the moment they appeared on sale in the 80s and up to the present day, are trying to improve the low frequencies of these speakers by magic with filters, reworking 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 body with a volume of only 45 liters - NOT corresponding to the optimal operating mode of the 30GD-2, 75GDN1-4 speaker installed in it. You can trim it at least with the root of rare rocks and glue it over with porous rubber on all sides - it will NOT work correctly anyway.

That is, the question of drastically improving the performance of these speakers at low frequencies, it is regrettable as it may be - 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 35AS-1 speakers with 30GD2 / 75GDN1-4 woofers (8), having a wide range of parameters, have been produced. In the new enclosures, this problem has been largely addressed and allows speakers from the earliest to the latest to feel right. The tuning of new enclosures is "stretched" and allows NOT to engage in the selection of subwoofers on purpose.

Mid-frequency problemsS-90

Almost all owners of the s-90 speakers note disgusting overtones and a large uneven response at midrange 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 sticking half of a tennis ball, etc. to the midrange cone. fail.

The main reason for the unsatisfactory sounding at medium frequencies is not the 15GD-11 speaker at all, but its acoustic design. This "glass", covering the midrange head from behind, has a scanty volume and is the second mistake made by the engineers who designed the S-90 speakers. At the "glass" of the mid-frequency head 15GD-11 (20GDS ...) everything is wrong, from the volume and configuration to the interior design. When replacing the casing of the s90 speakers with the correct one from the point of design of the woofer, the mid-range speaker should also be designed accordingly.

Of course, replacing a "scanty" standard glass with an acoustic design that is optimal in terms of volume and shape will not make the 15GD11 head another speaker, but it 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 mid frequencies. There are a large number of attempts on the Internet to alter the S-90 speakers in order to "fool everyone" and turn them into studio monitors. Attempts concern everything, just not replacing the main "weak point" - the case, and most often they turn out to be a failure. While keeping the S-90 speaker enclosures unchanged, in order 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 suggest leaving the original set of S-90 speakers intact. Their value is in the minimum budget and no matter how clever you may be, proven by decades of operation in the most severe conditions - performance.

In these columns there is something that can be improved in principle, this is to "get the maximum possible" from its speakers. To do this, you need to make an acoustically correct case for the original set of speakers and filters. As a result, you can reach a fundamentally new level of sound quality of these speakers without spoiling anything.

As a bonus, the old cases can not be thrown away and, if necessary, the "stock" S-90s can be assembled back and sold to any lover of authentic speakers made in the USSR.

Problems of native boxesS-90

• The wrong volume of low-frequency design does not give the required level of pressure on the bass;
• Suboptimal bass reflex tuning frequency leads to uneven bass response and poor bass quality;
• The type of low-frequency design "bass reflex" 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 unevenness of sound pressure at low frequencies in the room, and makes demands on obtaining high power from the amplifier;
• Weak walls of the S-90 speaker boxes lead to a loss of efficiency at low frequencies and give noticeable overtones when working at high volumes;
• Poor sealing of the boxes does not allow even the low-frequency design that the S-90 speakers in the stock version have;
• The extremely small volume of the cap of the mid-frequency head 15GD11 (20GDS-) leads to a "jamming" of the mid-frequency dynamics;
• Suboptimal damping of a small boxing midrange leads to noticeable overtones and "nasal" in the midrange;
• The shape and dimensions of the S-90 speaker cabinets in the stock version require their installation on furniture, which leads to a “wobbly position” of the speakers, furniture resonance at high volume and, as a result, to a deterioration in the sound of low frequencies;
• The “low-profile” shape of the speaker enclosures requires them to be mounted on specialized speaker stands, which ultimately increases the cost of the system. Placing 35AC-1 speakers on the floor leads to a lack of high frequencies and an incorrect scene.

Benefits of new enclosures

• The design of the low-frequency head is a quarter-wave labyrinth with its radical advantages at low frequencies over a bass reflex (detailed description here);
• The optimally calculated frequency and Q-factor of the quarter-wave resonator give a wide bandwidth and an optimal level of low frequencies;
• The highest rigidity of the box gives the highest possible efficiency, clean, resilient and biting sound at low frequencies;
• Rigid boxing of a large volume of the midrange head gives a lively and open mids and clear vocals;
• The location of the mid and tweeters on the front panel with respect to the distances to the walls of the cabinet according to the principle of "golden ratio" reduces diffraction phenomena on vocals and high frequencies and makes the sound much more comfortable;
• With the new enclosures, the acoustics is transformed into a classic floor-standing design with optimally positioned midrange and tweeter speakers;
• The speakers have narrower and taller front bezels than the standard S-90 and do not require any stands. The appearance of the speakers is improved many times over.

11-01-2009

Modification of acoustic systems Radiotehnika 35АС-012 (S-90)

Radiotehnika 35AS-012, Radiotehnika S-90, Radiotekhnika 35AS-012, Radiotekhnika S-90

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

Consideration of acoustics in a normal state

To begin with, you should specify the full name of the acoustics - 35AC-012. From their number it immediately becomes clear that we are dealing with acoustics of the highest class, by Soviet standards, that is, with acoustics having 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 bit to the time of their purchase. I took them from my friend for $ 50, when I came to him, when I saw the decorative grilles protecting the sound-emitting heads, I wanted to cry, they were dented and, moreover, very severely (mostly the treble and mid-range speaker grilles were damaged). But this did not scare me, since what was sold in 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 pretty decent. But nevertheless, two drawbacks should be noted, 1 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 simply killed me on the spot was an incomprehensible sound when the woofer was working, very similar to the fact that something was stuck to the speaker behind, and now something vibrates, as it turned out later it was a drop of solder that stuck to diffuser on the back. The second drawback was precisely the dynamics of the mid-frequency 15GD-11A - according to the old standard and 20GDS-1-8 according to the new (these speakers came in a large number of modifications for this reason, which is extremely difficult to track with you). And again, a small digression, in which I will say that the differences in the standards lie in the designation of the power, that is, according to the old standard, the nominal power of the speaker was indicated, and according to the new standard, the passport power is indicated (from the sound engineering course:

1. The nominal power of the speaker is such a power of the speaker, when summed up, it works with harmonic distortion levels not exceeding the permissible
2. 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 the 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 begins to resonate at high volume and thereby spoil the sound picture, and as you know, the mid-range speaker is crucial in the formation of the sound picture.

Let us now consider in order all the speakers that we have in stock:

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. The loudspeaker head is of an electrodynamic type, low frequency, round, with an unshielded magnetic circuit. The diffuser holder is made of die-cast aluminum alloy. The cone diffuser is made of impregnated paper pulp. Suspension - toroidal 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 suspension is used, which spoils the quality of the bass, it becomes more solid and boomy than in speakers with a lighter mass of the moving part and a foam suspension. But it should be borne in mind that the bass is influenced 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 with dignity. On the other hand, due to the rubber suspension, the speaker turned out to be very reliable and practically indestructible, and the foam suspension soon disintegrates 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 groups of complexity as a mid-frequency link when working indoors. The loudspeaker head is of an electrodynamic type, mid-range, round, with an 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. The toroidal suspension is made of polyurethane foam. The centering washer is made of impregnated fabric.

Here is a photo of this miracle of technology:

It is worth saying that at a good volume, it distorts the sound decently, but as practice has shown, this problem is very easy to solve and, at the same time, very simple.

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

In general, they sound good, except that the filters are tuned close to the resonant frequencies.

On 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 it. We will refine it according to the simplest possible scheme, without interfering with the filters, since there is nothing to do there without specialized equipment. Who will be interested in the acoustics diagram:

Modification 35АС-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 test subjects will not be available to children (if any) and other family members. We put the speaker system on our back and begin to disassemble it.
• Now we remove the decorative covers from all the speakers and set them aside.

Here they are:

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

• We remove the bass reflex cover and take out the phase inverter itself, and this must be done as carefully as possible, since we work 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 the remaining plastic lining with two chisels and carefully remove it, then unscrew the 4 screws that secure the attenuator itself and now it can be pushed out into the case. We push it out and unsolder 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 case and the column case is abundantly covered with a sealing viscous substance, I personally used it again when I put it back in place, but you can use a sealant or plasticine.
• We take out the bags of cotton wool, which, in theory, lie in your speaker system and put it aside.
• We dismantle the panel with filters, it is screwed to the body with screws, after having previously unsoldered the wires from the outlet on the back of the speaker system. We put it aside, since a lot of time will be spent with them at work.
• Finally, remove the terminal panel from the back of the speaker and set it aside.

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

2. Restoration of appearance:

For this purpose, we take the previously removed grilles and pads from the speakers, level them, carefully sand them, degrease and paint in several layers with automotive paint (which is in cans) several times and leave to dry. Immediately I will make a reservation that I restored the grilles only for the reason that I have a small child who can damage the speakers, otherwise the simplest solution would be to abandon the grilles as such, since they bring only disadvantages to the sound, then think for yourself.

3. Modification of the speaker case:

Here, in fact, everything is very simple, and it is carried out in several stages:

• The body can be reinforced if desired. What will it give us? Clearer and more even bass, since the cabinet panels will vibrate less and therefore will introduce less noise into the bass component of the sound. How to do it? Here it is purely everyone's business, since there are as many decisions as there are people. In general, everything consists in installing spacers, installing additional corners at the joints of the walls of the speaker system, installing stiffeners on the walls of the speaker. Personally, I limited myself to pasting in additional corners at the joints. You can also glue all joints tightly. Unfortunately, I cannot show a photo, since the entire speaker system is already damped with foam rubber.
• Sealing all joints and seams. It is carried out very simply with the help of various materials. For example, I used a plumbing sealant. The procedure is simple: cover the joints with sealant and gently smear it with your finger, thereby tightly sealing up any gaps.
• In a hardware store we buy foam rubber with a thickness of 10 mm (I personally chose this thickness, do not take too large as you will strangle the body) and glue it to all walls except the front with glue. Thus, we dampen the body, thereby increasing its virtual volume.

To do this, we buy terminal blocks with gilded universal connectors in the store. Since the S-90 has a large terminal block by itself, and the new ones are small, we dismantle the connectors from the terminal blocks and install them on the case from the S-90 terminal block. Then we lubricate the installation place on the sealant (do not regret it, then wipe off the excess) and put it all in place, tighten the screws. Here is a photo of what you are supposed to get:

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

• First of all, carefully consider the filter, pay attention to the fastening of the parts, since often the inductors were fastened with metal screws, which immediately knocks down the filter setting.
• If there were problems in the fasteners, complete it to the end by excluding the metal parts from the fasteners. There are also cases of assembling the filter on a metal plate, then transfer the filter to the 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 were walking and for this reason the factory could change the filter circuit. By the way, we exclude the attenuator from the circuit, it just spoils the sound.
• Now we take a soldering iron in our hands (preferably 100 watts) and disassemble the filter, or rather, we simply remove all the jumpers that were 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, since the changes in sound quality will be insignificant, but the costs are simply colossal.
• After assembling the filter, we solder the wires that will go to the speakers based on: for the low-frequency link 4 mm 2, for the mid-range link 2.5 mm 2, for the high-frequency 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 routing the speaker wires, securing them, and covering the filter with foam rubber.

You will get something similar to these photos:

6. Installing the attenuator:

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

7. Installation of the bass reflex:

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

8. Reinstall the bass reflex cover:

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

9. We proceed to install the speaker drivers in place:

• A) Install the HF head:

1) We remove that parody of the seal that stands on it (behind it, some kind of gum or cardboard).
2) Cut out a new seal, a mouse mat 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 the decorative cover (the grill is optional) and tighten it tightly with the screws.

• B) Install the midrange head:

1) We make a cylinder of foam rubber, of such a size that our box would fit 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 it will be necessary to widen 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) We 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, such that it fits tightly on the speaker frame and closes all the windows.

5) We fill the box with cotton wool, having previously fluffed it up.
6) Put the dynamic head, grill (optional) and frame in place and tighten.

1) First, put back the bags of cotton that were removed during the disassembly of the speakers. We 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 window of the diffuser holder.

2) We make a pad of porous material, for example
apply the window seal and carefully put the speaker in place.
3) We tighten the mounting screws. Do not exert great effort, then the speaker will be spring-loaded by the gasket and this will reduce the vibration energy transmitted to the case.
4) We put in place the lattice (optional) and the decorative overlay. If you did install the grill, then I advise you to cut out small triangles from the foam rubber and put them on the speaker in the place of its attachment, this will exclude the vibrations of the grill, and therefore will remove overtones at high volume.

I came up with this solution a long time ago, see the photos for more details:

Conclusion:

After revision, all the listeners (there were few of them, about five people, but I asked for the most honest information from them) noted softer and softer basses, a much cleaner mids, the top 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 affordable. All components, of course, can still be modified or changed several times. For example, instead of foam rubber, you can use felt (natural), this, in theory, will give better results than foam rubber, it is also good to use vibromastics. Many people advise replacing the 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 should be modified based on the halves of a tennis ball (by the way, the idea is quite interesting, I did not do it myself, since I do not have such speakers in stock).

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