11-01-2009

Refinement of acoustic Radiotehnika systems 35AC-012 (S-90)

Radiotehnika 35AC-012, Radiotehnika S-90, Radiotechnics 35AC-012, Radiotechnics S-90

Currently I am the proud owner of Radiotehnika S-90 speakers.

Consideration of acoustics in normal condition

First, you should specify the full name of the acoustics - 35AC-012. From their number it immediately becomes clear that we are dealing with acoustics upper class, by Soviet standards, that is, with acoustics having very high characteristics. It should be noted right away that by Soviet standards this was not the most best acoustics, and an ordinary ordinary workhorse. There were acoustics that had a more balanced sound, for example the same Cleaver/Corvette 35AC-008.

But as they say, we have what we have. Let's go back a little to the moment of their purchase. I bought them from a friend of mine 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, at that, very cruelly (mainly the grilles of the high-frequency and mid-frequency speakers were damaged). But this didn’t scare me, since what was sold on our market cost at least $100, and the quality of the speakers deserved no more than 3, and in these speakers the speakers looked like 5. In general, I took these speakers to my home. When connecting them to an amplifier the sound was quite decent. But nevertheless, two drawbacks should be noted, 1 of which is inherent in all 35AC-012, and as it turned out, in all its 35AC clones, to one degree or another.

The first of the shortcomings that simply killed me on the spot was an incomprehensible overtone when the woofer was working, very similar to the fact that something was stuck to the speaker from behind, and now it was vibrating, as it turned out later it was a drop of solder that stuck to diffuser from the reverse side. The second drawback was precisely in the mid-frequency dynamics 15GD-11A - according to the old standard and 20GDS-1-8 according to the new one (these speakers came in a large number of modifications, for this reason it is extremely difficult to track which one you have). And again, a small digression in which I will say that the differences in the standards lie in the designation of power, that is, according to the old standard, the rated power of the speaker was indicated, and according to the new standard, the rated power is indicated (from the audio engineering course:

1. The rated power of the speaker is the power of the speaker, when supplied, it operates with harmonic distortion levels not exceeding the permissible
2. Nameplate power (often also called noise): 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 rated power).

An additional division has also been introduced into frequency ranges heads, 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 volumes and thereby spoils the sound picture, and as you know, the mid-frequency 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, also known as 75GDN-1-4(8):

Purpose - use in closed and phase-inverted remote speakers acoustic systems ah household radio equipment of the highest complexity group as a low-frequency link when working indoors. The loudspeaker head is of electrodynamic type, low-frequency, round, with an unshielded magnetic circuit. The diffuser holder is made by injection molding from aluminum alloy. The cone diffuser is made of impregnated paper pulp. The suspension is toroidal-shaped and made of rubber. The centering washer is made of impregnated fabric.

I would also like to add that the speakers have a relatively heavy dome and a rubber surround, which spoils the quality of the bass; it becomes less continuous and booming than speakers with a lighter moving part and a foam surround. 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 problems can be eliminated a little and the speaker will play decently. On the other hand, due to the rubber suspension, the speaker turned out to be very reliable and practically indestructible, while the foam suspension soon crumbles due to the presence of sulfur in the air and the speaker requires repair.

Purpose - use in closed and phase-inverted remote acoustic systems of household radio equipment of the 1st and 2nd complexity groups as a mid-frequency link when working indoors. The loudspeaker head is of electrodynamic type, mid-frequency, round, with an unshielded magnetic circuit. The diffuser holder is made by injection molding from aluminum alloy. The conical diffuser and spherical cap are made of impregnated paper pulp. The toroidal-shaped suspension is made of polyurethane foam. The centering washer is made of impregnated fabric.

Here is actually a photo of this miracle of technology:

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

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 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, but the filters are tuned close to the resonant frequencies.

Upon 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 without specialized equipment there is nothing to do there. For anyone interested, here is the acoustics diagram:

Revision 35AS-012

I will describe in order all the stages of improvement that my speakers went through:
1. Disassembly:

• First of all, we take them to a secluded place (meaning a room) in which our experimental subjects will not be accessible to children (if any) and other family members. We lay the speaker system on its back and begin to disassemble it.
• Now remove the decorative covers from all the speakers and put them aside.

Here they are:

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

• We remove the bass reflex cover and take out the bass reflex itself, and this must be done as carefully as possible, since we are working with plastic, and it can easily break. Then we hide these details in a secluded place.
• Now let's take on the regulator/controllers of the HF/MF sections. To dismantle them, you need to remove the decorative plug in the center of the regulator, then unscrew the exposed screw and remove the regulator handle. After this, carefully pry up the remaining plastic lining using two chisels and carefully remove it, then unscrew the 4 screws securing the attenuator itself and now it can be pushed inside the case. We push it out and unsolder it from the filter. We put it aside, in the future you will need to work a little magic on it. By the way, the joint between the attenuator body and the speaker body is generously covered with a viscous sealing substance; I personally reused it when putting it back into place, but you can use sealant or plasticine.
• We take out the cotton wool bags that are supposed to be in your speaker system and set them aside.
• We dismantle the panel with filters; it is screwed to the body with screws, having previously unsoldered the wires from the output at the back of the speaker system. We put it aside, since we will spend a lot of time working with them.
• Finally, remove the terminal panel from the back cover of the speaker and set it aside.

Looks like it's been done big job, but in reality this is just a drop in the ocean. More interesting and time-consuming work lies ahead.

2. Restoration of appearance:

For this purpose, we take the grilles and covers from the speakers that we removed earlier, level them, carefully sand them, degrease them and paint them in several layers with car paint (which is in spray cans) several times and leave them to dry. Let me make a reservation right away that I restored the grilles only for the reason that I have a small child who can damage the speakers, otherwise the most simple solution there will be a rejection of grilles as such, since they only introduce disadvantages into the sound, think for yourself.

3. Refinement of the speaker system housing:

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

• If desired, the body can be strengthened. What will this give us? Clearer and smoother bass, since the cabinet panels will vibrate less and, accordingly, will introduce less overtones into the bass component of the sound. How to do it? This is purely a matter for everyone, since as many people there are as many decisions. In general, it all consists of installing spacers, installing additional corners at the joints of the walls of the speaker system, and installing stiffeners on the walls of the speaker. Personally, I limited myself to gluing in additional corners at the joints. You can also tightly glue all joints. Unfortunately, I can’t show you a photo since the entire speaker system is already damped with foam rubber.
• Sealing all joints and seams. It is done very simply using various materials. For example, I used plumbing sealant. The procedure is simple: cover the joints with sealant and carefully smear it with your finger, thereby tightly sealing any cracks.
• At a hardware store we buy foam rubber 10mm thick (personally, I chose this thickness, don’t take too much as it will suffocate the body) and glue it to all the walls except the front. In this way we dampen the body, thereby increasing its virtual volume.

To do this, we buy terminal blocks with gold-plated connectors in the store. universal type. Since the S-90 terminal block itself is large, and the new ones are small, we remove the connectors from the terminal blocks and install them on the body of the S-90 terminal block. Then we lubricate the installation area with sealant (don’t be sorry, wipe off the excess later) and put it all in place, tighten the screws. Here's a photo of what you should get:

5. Let’s move on to reworking and replacing the filter:

• First of all, carefully examine the filter, pay attention to the fastening of the parts, since often the inductors were fastened with metal screws, which immediately disrupts the filter settings.
• If there were problems with the fastener, complete it by eliminating metal parts from the fastener. There are also cases of assembling the filter on a metal plate, then transfer the filter to a plywood panel.
• We pick up a piece of paper, a pen, and carefully redraw all the elements of the circuit, restoring, so to speak, the filter circuit itself, because the parameters of the speakers were wrong and for this reason the filter circuit could have been changed at the factory. By the way, we exclude the attenuator from the circuit, it simply spoils the sound.
• Now we take a soldering iron (preferably 100 watts) and disassemble the filter, or rather, simply remove all the jumpers that were installed from the factory.
• Now we are assembling the filter, instead of jumpers we will now use a cable made of oxygen-free copper 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 buy a very expensive cable, as 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-frequency link 2.5 mm 2, for the high-frequency link 2 mm 2.
• We put the filter in place, and then solder the terminal blocks to it (observe the polarity, otherwise you will lose the sound picture).
• The very last step is to run the wires to the speakers, secure them and cover the filter with foam.

You'll end up with something similar to these photos:

6. Attenuator installation:

• We remove all resistance from it.
• Let's put it in its place.
• We carefully seal it.
• Additionally, we cover it with foam rubber (I only covered it on the front wall)
• We install all the decorative panels completely.

7. Installation of the bass reflex:

Everything is simple here, we put it back on the sealant, carefully make sure that it is not pinched anywhere by the foam rubber, as this will throw off its setting.

8. Reinstall the bass reflex cover:

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

9. We proceed to installing the dynamic heads in place:

• A) Install the HF head:

1) We remove the travesty of the seal that is on it (some kind of rubber or cardboard at the back).
2) Cut out a new seal; a mouse pad, in particular a black porous base, is perfect.
3) Solder the wires to the speaker and install it in place.
4) Put the decorative trim (grid if desired) in place and tighten it tightly with the screws.

• B) Install the midrange head:

1) We make a cylinder from foam rubber, such a size that our box will fit into it. We place this cylinder inside the speaker and pass a cable through it, which we take out.

2) Pass the wire through the box (most likely you will have to widen the hole), then put the box in place, adjust the length of the wire and seal the hole into which the wire is passed.
3) Solder the wires to the speaker.
4) Now the crucial stage is damping the mid-frequency head. To do this, we sew a cylinder of foam rubber, such a size that it fits tightly onto the speaker frame and covers all the windows.

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

1) First, put back the bags of cotton wool that were removed during disassembly of the speakers. 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 gasket from a porous material, for example
Apply window seal and carefully place the speaker in place.
3) Tighten the mounting screws. Do not apply much force, then the speaker will be spring-loaded by the gasket and this will reduce the energy of vibrations transmitted to the body.
4) Put the grille (optional) and decorative trim in place. If you do install a grille, then I advise you to cut out small triangles from foam rubber and place them on the speaker at the place where it is attached; this will eliminate the vibrations of the grille, and therefore eliminate overtones at high volumes.

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

Conclusion:

After the modification, all the listeners (there were not many of them, about five people, but I asked for the most honest information from them) noted more delicate and soft bass, a much cleaner middle, the highs remained practically unchanged (it seemed to me that they became a little cleaner). Also, the acoustics began to calmly reach higher volumes.

In conclusion, I would like to say that the proposed method is the cheapest, simplest and most accessible. All components, of course, can 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 a good idea to use vibrating mastics. Many people advise replacing the 15GD-11A with a 5GDSH broadband, for me this is a bad idea, but it’s everyone’s business. 10GD-35 - it is recommended to treat it with a notch filter, 15GD-11A should be modified based on halves of a tennis ball (by the way, the idea is quite interesting, I haven’t done it myself since I don’t have such speakers in stock).

Register.

Hello friends.

Despite such a venerable age for speakers, they are preserved in excellent condition - as if they were bought just yesterday at the Melodiya store.
Polished without scratches or abrasions. The plastic is also intact and smooth.
All this can be seen in the photo - click on the image to enlarge.

The marking was still old-GOST, not 15AS - 404, but simply 15AS-4

I was also pleased with the filling.
The screws had factory seals and all internal components have survived untouched to this day.

The speakers and filters seemed to say with their appearance -
"Yeah... it's hard to find people like us now!"

It's always a pleasure to remodel an acoustic in such excellent condition.
I want the sound to match the condition.
And I got to work.

I didn’t want to do anything supernatural, as we know, the best is the enemy of the good.
The goal was to get rid of all the weak points and see what would come of it in the end.

The weak points in such household Soviet acoustics are as follows:

• insufficient volume of housings
• no filter on the woofer
• poor sealing
• appearance(not for all, but these ones clearly require improvement)

So I decided to eliminate them as much as possible and give these speakers a second life

The first thing I did was install the speakers on the outside of the case and glue the inside with a layer of technical wool (cotton).

For these purposes I used PVA glue.
Cotton wool comes complete with acoustics - the original “mats” that were in the speakers delaminate perfectly and you can separate pieces of the required thickness. I made it about a centimeter thick.

So with the volumes, I did everything I could in the format of the body data.

It's time to get started with acoustic filters.

These speakers have a filter installed only on the high-frequency section.
Its function is performed by the 3GD-31 speaker (more modern marking 5GDV-1-8).
It was used in many other acoustic systems, the most famous of them is perhaps the COMET 25AC-225 (aka 15AC-225).

Some people criticize this speaker, others praise it. Everyone's taste in markers is different.

I like it and when I was assembling my floor three-way acoustics(I’ll write about it in detail another time), then these speakers took pride of place in the HF section.

They had a second-order high-pass filter in the form of a capacitor and a coil.

There is no low-frequency filter at all. The speakers 25GD-26-30 (grandfather of the speaker 35GDN-1-4), which serve as low-frequency speakers here, are connected directly.

By the way, the VEGA 10MAS-1M speakers are very similar to this acoustic system.
Actually, 10MAS-1M is a steroid clone of our 15AC-404 - the only difference is in the size of the case, in 10MAS they are one and a half times larger and in resistance - 8 Ohm 10GD-30 are installed in 10MAS.

By the way, on the basis of these cases, I built myself wonderful shelf holders, I’ll also write about them someday, I have the material - the photos are stored somewhere in the bins of the hard drive.

Here's what I did with the filters: I removed the coil from the second-order high-pass filter and added a modern capacitor to it to get a second-order low-pass filter.

The remains of the high-frequency filter in the form of a resistor and capacitor were also replaced by a modern condenser, thereby making a first-order high-frequency filter - it will be enough to prevent low frequencies to a cannon shot.

cut off high frequencies on the low-frequency link it was simply necessary so as not to interfere with high-frequency vibrations in reproducing the velvety and rich bass that the 25GD-26-30 speaker is capable of.

Now that I’ve dealt with the second ailment, now it’s time to work on the tightness.

The internal seams in this acoustic are coated with some kind of Soviet wood glue.
I don’t know what kind of glue this is, but it has been preserved perfectly. My attempts to pick out a piece were unsuccessful - it is hard and durable as a stone. So let it stay.

But the foam gasket that seals the back cover has turned into a jelly-like dark red substance over time - it needs to be replaced.

If you've ever taken apart Soviet acoustics, especially the Radio Engineering speakers (S30, S50, S70 or S90), we saw that sealing was often carried out with Velcro (similar to the one that was placed in the interpanel seams of Soviet Khrushchev buildings) or plasticine.

In this matter, I did not stray far from the origins, since the method is very practical.
After all, if you sit, for example, on a sealant, then if necessary, open it and repair it - you will spend a lot of effort.

Unfortunately, I didn’t have any supplies of Velcro from my school days, and I didn’t want to use regular plasticine - it could leave behind greasy stains.
Therefore, I chose the best option - window putty. It is very plastic - like plasticine, but it softens in your hands much faster and does not leave greasy marks.
This is what I used when sealing the cases.

The last item left on the menu is appearance.

The speaker frames and front panel were painted with matte spray paint and began to look very massive and nice.
But this approach to painting speakers is categorically unacceptable - spray paint will greatly affect their sound quality, not for the better.
The Internet offers various options for how to paint the speaker diffusers themselves, but each has its own disadvantages:

• special paint for speakers - very expensive
• grated pencil lead - it smudges and crumbles over time
• with a core from a black marker - not for everyone, the color will have a brownish tint
• paint from inkjet printer- does not stain areas covered with glue

I also wondered what to paint the speakers with.
And through some logical thinking, I made an assumption about the ideal paint option and was right.
I am happy to share it with you: the paint is water-based, safe for impregnating speakers, paints over all areas with glue, and after drying gives a noble matte color.
After drying, the color perfectly matches the original color of the pendants.
This is stamp ink! The same one that is poured into print pads.

In case there are many different colors of these paints, I’m posting a photo of the one I use.
Painted with a cotton swab in one layer.

Well, that's almost all.
The final touch remains - replacing the ancient wires with normal terminals.
Well, there’s no problem with that - you can buy anything to suit your taste in every radio store, I chose these:

The lower limit of the frequency range reproduced by the loudspeaker is determined by the main resonant frequency of the head. Unfortunately, there are very rarely heads on sale that have a main resonant frequency below 60-80 Hz. Therefore, to expand the range of operating frequencies of acoustic systems, it seems very relevant to reduce the main resonant frequency of the heads used in them. As is known, the moving head system (diffuser with voice coil) in the main resonance region is a simple oscillatory system consisting of mass and flexibility of the suspension. Resonance frequency such a system is determined by the formula:

Where m is the mass of the diffuser, voice coil and attached air mass, g, C is the flexibility of the suspension, cm/din.

Improving the sound of 35AC-1 and its modifications

The three-way speaker system 35AC-1, developed about 10 years ago at the Orbita design bureau of the Riga production association Radiotekhnika, can, without exaggeration, be called the founder of a family of speakers that made high-quality sound reproduction a reality at home. At that time, 35AC-1 was the best not only among domestic household loudspeakers, it sounded better than many speakers from foreign companies.

In 1979, based on the 35AC-1 (the crossover filter and the front panel of the acoustic design were changed), the 35AC-212 (S-90) was created, which is currently produced by several enterprises under the names 35AC-012 and 35AC-016. Unfortunately, today these speakers no longer satisfy the increased demands of high-quality sound lovers.

As studies conducted at the Department of Radio Broadcasting and Electroacoustics of the Moscow Electrotechnical Institute of Communications (MEIS) have shown, the weakest link of the speaker is the mid-frequency head 15GD-11A. Frequency response This head has a sharp decline above 4.5 kHz, which practically eliminates the possibility of obtaining “bright”, “transparent” sound in the mid-frequency region. It also has another drawback - the large mass of the moving system, which can be successfully combated by introducing acoustic damping.

20GDS-4-8 as a low-frequency

It is known that low-frequency heads are extremely rare on sale. Much more often in stores you can find mid-frequency dynamic heads 20GDS-4-8 (old name 15GD-11). If necessary, they can be used as low-frequency ones by increasing the flexibility of the corrugated centering washer [L]. For this purpose, two opposite sectors of 90 degrees each are removed from it (see figure). The removed parts are carefully cut out with a thin sharp scalpel so that no paper flakes or individual threads remain on the cut. Coat the edges of the resulting holes with vibration-absorbing mastic

Nameplate power... 90 W

Rated power... 35 W

Nominal electrical resistance... 4 Ohm

Frequency range... 31.5-20000 Hz

Nominal sound pressure... 1.2 Pa

Overall dimensions of the speaker... 360x710x285 mm

Speaker weight no more than... 30 kg

S-90 is a classic of Soviet column construction. According to the manual, the S-90 speaker system is designed for high-quality reproduction of sound programs in combination with various types household radio equipment.

Well, for the early 80s these were truly outstanding speakers with high quality sound. However, foreign speaker construction is developing, and already at the beginning of the new century, the sound of the S-90 is perceived differently.

High frequencies sound disgusting, there is simply NO mids! And if we talk about bass, then a similar effect will be when placing a healthy bass player in a large kick drum... The lows drone on in black. It is impossible to listen to D&B style music; IDM also hits the ears. What can we say about classics and calm music. After an hour or two of listening, my ears begin to hurt (however, my head and stomach hurt no less). Despite these shortcomings, many people buy these speakers.

All of the following applies to Radiotechnika S-90a (AC35-212) speakers. This is one of the very first releases (and one of the best), characteristic features - 2 controls on the front panel, HF and midrange speakers shifted from the center, paired speakers, 4 Ohm impedance. However, the meaning of the modification and the modification itself can easily be applied to other S-90s (S-90b, S-90F, etc.), their analogues (Orbita, Amphiton, etc.), as well as to homemade speakers. The main criterion is the presence of 3 bands (speakers) and a bass reflex. The modification of speakers with a closed cabinet (i.e. without a bass reflex) is somewhat different, I will write about this later. And one more thing - there are many options for improvement, so in some places I will describe 2 methods. You will choose the most suitable one yourself..
I won’t write a list of necessary materials - in most cases, everyone uses what is in this moment most accessible.

1) Disassembly

We take one speaker and place it on the floor with its back wall (this is the most convenient way to remove the speakers). Using a figured screwdriver, unscrew the 6 bolts securing the decorative plastic trim from the bottom of the column. Using a flat-head screwdriver, unscrew 4 bolts and remove the decorative nameplates from the speakers and the protective grilles.

Next, you will need a heated soldering iron! Then we unscrew the 4 bolts securing the woofer and carefully lift one side of it and remove it from the housing. We unsolder the wires (you can, of course, mark which one was soldered where - but it’s better to then check the diagram and solder it 100% correctly) and put it aside. We take out the midrange speaker from the housing (it was secured with a nameplate) along with the glass in which it stands. Unsolder it and put it to the woofer. We take out the HF (tweeter) - it was also attached with a nameplate and unsolder it. If there is no mark on it at one of the terminals (+), we mark which wire was soldered where, then we look where it goes according to the diagram and find “+”. We put it with the other speakers.

Be careful with diffusers! The speakers can only be grasped by the magnet or diffuser holder supports!!!
Unscrew the 4 screws on the bass reflex and carefully remove it from the housing. It is held on by sealant, the main thing here is not to use excessive force - it may break! We take out 2 “sausages” of cotton wool from the body (if it is there). We unscrew and remove the filter from the housing (it can be either on an iron chassis or on a wooden plank). The wires going to it can be cut off with wire cutters (they still need to be replaced early). That's all with disassembly! Now we need to finalize and assemble.

2) Modification of the case - it is advisable to strengthen the back side of the case with wooden slats (attached with screws and epoxy). It is also necessary to place a wooden spacer in the center of the speaker (between the rear wall and the front) at the level of the midrange glass. (the main thing is to pay attention to the possibility of then installing a bass reflex!!!) This is necessary to reduce vibrations of the body - turn it up loud and put your hand on it - the body shakes! You also need to check the tightness of the housing at the joints and, if necessary, coat the joints with epoxy glue or sealant.

3) Refinement of the filter: You will need a diagram.

The idea is to remove switches from the circuit, replace the audio wires with oxygen-free copper, solder the speakers directly to the filter, solder the lead wire directly to the filter and shorten the signal path

In the absence of finances, you can also supply suitable copper ones from the Soviet Union. The point of selecting wires is to have a multi-core wire for the woofer, the larger the better (but not less than 2.5 mm2, and it’s bad to solder more than 4 mm2), for the midrange you can have a multi-core of at least 1.5 mm2, and for the high-frequency one you can have a single-core of at least 1 mm2 (I recommend using a twisted pair cable of the fifth category for + and -). It should be said that the selection of wires is a delicate matter. There are still fierce discussions about the choice of wire for speakers. I express my personal opinion. I advise you not to skimp and buy at least the cheapest audio cable! The sound quality greatly depends on it! Take my word for it.

I also highly recommend remounting all the filter parts on a small piece of plywood/wood, so that you can place the filter on the bottom of the speaker, next to the bass reflex. This is important (especially if the filter is mounted on an iron plate). The inductors should be attached to the new board not with iron screws, but with something plastic or mounted on epoxy. So, we replace all the wires on the filter board - we install it directly to the outputs of the capacitors, removing the contact plates from them.

I will not give the sequence for replacing the wires. As well as tips on where to solder the wires from the bass, midrange and treble. I hope you figure it out :). If you can’t cope, invite a knowledgeable person (one who can distinguish a capacitor from a resistor will do). As a last resort, write to me by e-mail [email protected]. We're done with the filter - put it aside.

4) Hull damping:

The point is to, if possible, absorb and dissipate all standing waves inside the housing. The criterion for choosing a material is that the denser and thicker it is (felt), the better it absorbs; the thinner and lighter it is (sintepon), the worse it is. The best way to make a pancake is to coat the body with sound-absorbing mastic (automotive mastic will do), then glue a layer of felt under 1 cm + the low-frequency part with another such layer and stick chaotically pieces of felt on top. They also recommend covering it with a layer of material for kitchen hoods - I don’t know, I haven’t seen it. I did this myself - everything is upholstered with 1.5 cm felt + the bottom part is another 1.5 cm + pieces. The sound absorber must be glued throughout the entire inside of the housing. After installing the first layer of felt, I recommend placing a filter board (with wires soldered to it) and a bass reflex port on the bottom of the speaker (otherwise you won’t be able to put it in later!), placing the remaining layers of sound absorber while closing the filter. and also wrap the bass reflex with a sound absorber (the main thing is not to cover the internal section of the pipe and maintain direct access from the bass diffuser to the bass reflex). It is necessary to look at the internal volume of the case - you cannot reduce it excessively - it will affect the depth of the bass! The body is finished.

By the way, I advise those who want to find household felt, about 1.5 cm thick.

5) Midrange speaker and its glass.

I highly recommend replacing the standard 15GD-11A (or its clone) with a broadband 6-GDSH-5-4 or 6-GDSH-5-8. The difference between them is that the first has a resistance of 4 ohms, and the second has 8 ohms. Accordingly, when installing 6-GDSH-5-8, the filter does not need to be changed, and when installing 6-GDSH-5-4, put a 4 Ohm large resistor (6-10 W) power. Resistor R3 (4.3 Ohm) from the midrange divider (columns 35AC212) is just suitable for this. Don't worry about losing power with this swap! You will only benefit in sound quality. The method has already been tested on many S-90s, there are no negative reviews, the power has not decreased. Moreover, competitors for the 6-GDSh-5 still need to be looked for (even among foreign analogues). And this is when the cost of a pair of these broadband speakers (new!) is $4-6. They have only one minus - appearance. Although I like it :).

For the midrange you need to make a PAS. This means covering the windows of the diffuser holder on the back of the speaker with a layer of foam rubber 0.5-0.8 cm thick. Quilted batting will also work. It is convenient to cut a strip of foam rubber 4-5 cm wide and a length equal to slightly less than the perimeter of the speaker, sew it and stretch it over the windows (for 15GD-11A). Then sew with threads to the supports. We made a PAS (be sure to do it - it degrades the quality factor, which is vital for almost all Soviet midranges used in the S-90 15GD11, and even more so!) - you can install the glass and speaker in place. Insert the glass into the body and wrap the outside in 2-3 layers of a good, dense sound absorber. It is convenient to cut off a boot boot that is suitable in height and width from a felt boot, place it in the body, and then place a glass of midrange in it. The inside of the glass also needs to be covered with a layer of sound absorber (felt is just right). The purpose of such damping is to eliminate the influence of the low-frequency head on the midrange. Then you need to put fluffy cotton wool in the glass and you can put the midrange speaker in place. First check that its phasing is correct.

When you connect a 1.5V AA battery + to + the speaker, and - to -, the diffuser moves forward. Checking phasing is important! We solder the wires to it (+ according to the diagram to + on the speaker) and place them in the housing through the rubber gasket, between the midrange and the glass. Rubber 2-3mm thick. It is convenient to use window rubber insulation made in the form of hollow tubes and with a self-adhesive side.

We install the speaker, seal it with plasticine and screw it on top with a nameplate, placing rubber gaskets on the screws between it and the speaker. It is better not to install a protective grille - it spoils the sound. Have you seen good imported speakers with grilles on the speakers? When installing 6-GDSH-5 under the nameplate, you will need to put rubber gaskets about 1 cm thick on the screws.

More about the midrange speaker. If you don’t want to install another midrange driver, you can modify the old one, for example like this. Although if you have a speaker with a rubber, rather than fabric, surround, it’s better to go for the 6GDSh!

6) Vata:

This sweet word is cotton wool... It greatly affects both the overall sound and the bass in particular! So one day I reduced its amount by half. The speakers began to emit not bass, but some kind of hum...

So, we sew a couple of gauze bags (35 cm by 35 cm) and fill them with cotton wool from the 2 sausages that were removed from the body, so that almost the entire sausage goes into the first bag, and less than half of the second into the second bag. Fluff the cotton wool. We place these bags in the upper part of the case under the slot for

HF and next to the midrange glass. We fluff the remaining half of the cotton sausage and simply throw it on the bottom of the column, on the filter wrapped in felt. In my opinion, this is the best placement of cotton wool in these columns.

7) HF head.

Solder according to the diagram. We put it into the body through a rubber gasket and screw it on top with a nameplate. We also don’t install a protective grille!
Uhh... A hell of a job has been done, but there is very little left! Let's continue.

8) woofer.

We solder it (it is advisable to check the phasing, as well as the midrange) and place it through a rubber gasket (required!), fasten it with bolts, again through rubber washers and seal it with plasticine sealant. We put a nameplate on top.

9)End of assembly.

We install the plastic front, tighten all the bolts and wipe the front panel.

Yes - a few little things (quite important!): run the wires to the HF and MF under a layer of sound absorber, and wrap them around the LF; carefully check the phasing, keep in mind that the bass and midrange in the S-90 are connected in antiphase; be sure to place the speakers on rubber pads; remove all parts from the plates of the disconnected HF and MF dividers, and cover them with a sound absorber; don't skimp on wires; remove the grilles; do not suffocate the volume; the bass reflex pipe must communicate freely with the surface of the speaker diffuser; gauze is clamped inside the bass reflex pipe - it is needed there; Place the speakers on spikes (for example like this); It is better to immediately solder the connecting cable to the filter; it is much cheaper than buying good connectors.

Listening to music on my 35AC-1, every day I became more and more tired of their sound. I have long heard about the modification of the speaker system, but for some reason I didn’t pay much attention to it before. But then I decided to try it anyway. After surfing the Internet, I found a lot of information about modifications to the 35AC-212 (S-90) and 35AC-1, and I got down to business.

1. Body.
The first thing I did was disassemble the speaker system. I unscrewed the front panel, the dynamic heads, took out the cotton wool, removed the filter and the bass reflex.

Then I strengthened the back wall of the box, installing two slats across the entire body with a thickness and width of 20 mm and a spacer (see photo), closed the holes on the front panel where there was a glass from the mid-frequency head, a high-frequency head and switches. I filled 10mm thick plywood with PVA glue. In place of the glass, I cut out new holes for the midrange and tweeter. (see photo). I placed a plastic cup (similar to the S-90) on the midrange driver, but it is usually better to use a wooden one. Inside, I covered all the walls with 18mm foam rubber (I couldn’t find any felt), but before that I needed to lay the HF and MF head wires under it (I didn’t do this, I was in a hurry). The bass reflex was shortened by 10cm by tuning it to a different frequency (mumbling less) and also covered with foam rubber on top. The box was covered with black lining fabric.

2. Filter.
I started by throwing out the tone switches and unnecessary resistors; for this you may need a circuit (it’s not hard to find on the Internet). After that, I moved all the filter parts onto a wooden board made of 8mm plywood. It is not recommended to weld inductors; they must be glued. I soldered all the connecting wires of the filter onto an audio cable (at least the cheapest one). I soldered the wires that lead to the heads directly to the filter and not through each other. For the low-frequency driver, a thick wire is no less than 2 mm?, for the mid-frequency driver, no thinner than 1.5 mm 2, and 1 mm 2 for the high-frequency head (in the photo, the wires for the midrange and high-frequency heads are thin, I wanted to try it and installed what was there, and later replaced it).

The filter was screwed onto the bottom wall of the speaker.

3. Vata.
From one sausage that I took out, I sewed a square pillow and threw it on top of the column. On the other I made a small pad (about 0.5 sausages) and placed it on the bottom on top of the filter.

4. Midrange.
I didn’t have a midrange driver at all. I installed the 10GD-34 only after finishing it (by gluing a cap made of a tennis ball, I also found an article about this modification on the net), and also closed the windows in the head diffuser holder with foam rubber. I covered the inside of the glass with felt and filled it with cotton wool.

5 . The final part.
I soldered the dynamic heads while maintaining the switching polarity. The dynamic heads were screwed through rubber gaskets. I turned on the music and began to enjoy a completely different sound. I myself didn’t believe that my 35AC-1 could play like that.
P. S. I advise you to redo one speaker first so that you can compare the sound of one and another speaker system.