Chapter 1

KinAp has (or existed) three types of good full-range speakers: 4A-33, 4A-32, 4A-32-6.
I have arranged them in order of preference. The last speaker has the narrowest frequency range and the greatest frequency response unevenness, but it has the only cast aluminum diffuser holder, which does not require harsh damping measures like the first two speakers.
The first speaker has the widest range of reproducible frequencies and the smallest uneven frequency response. Also, the size is one and a half times smaller than that of the last two.

That's all for now. Then I can tell you about the fine-tuning of the diffuser of broadband speakers and about the construction of the case. But absolutely seditious things will go there, so if someone doesn't like it, I can stop in time and not waste time on nonsense.
I think that the placement of this material is most convenient here in the conference threads. I will be grateful for advice and comments.

Chapter 2 about speakers.

When the speaker is new, it is better not to touch its diffuser, because the Kin Up (ovsky) speakers and the Novosibirsk 10GD-36 have already applied the necessary impregnations and refraction, which prevents the propagation of "harmful" vibrations. Another thing is when old speakers come across with traces of violence - dents on the diffuser, these dents must be covered, for example, with a liquid Guerlain solution from the outside and, if possible, from the inside. There is only one little left - to trim frequency response up and down. There is nothing new here. To smooth the frequency response from below, it is necessary to work on the corrugation of the diffuser, if this corrugation is made of paper. The corrugation is usually made with a sinus profile with two "periods". It is better to muffle using the Shorov method, that is, with guerlain, but smear not the entire corrugation, but only the first half-period closest to the center and a strip 0.5 cm wide adjacent to the corrugation. ... It should spread in an even layer. It is better to soak the remaining half-periods of the corrugation with vegetable oil to increase the flexibility of the suspension. This will lower the main resonance frequency and flatten the frequency response. For speakers with rubber or polyurethane foam, "impregnation" can only do harm. Good results in reducing the resonant frequency are obtained by installing the speakers in one housing, while the speakers must be connected in parallel. An indicative result for improving linearity is provided by connecting in parallel to each of the paired speaker resistors equal in magnitude to the active resistance of the coil.
For broadband speakers, additional radiating cones are used to increase the response at high frequencies. The frequency response of such speakers mainly in the high frequency region is determined by the geometry of the cone, but even here something can be improved. Now I saturate the cone and coat it with BF-6 glue. This increases the stiffness of the cone, which leads to wider bandwidth and smoother frequency response. So for speakers 4A-28, it is possible to expand the band to 17 ... 18 kHz. Impregnation is carried out in three layers from the outside of the cone and once the BASE of the cone is coated with glue from the inside, it is better not to touch the inside, except for a narrow strip of 2 mm along the edge of the cone. Drying time for one layer of glue is 6 hours, complete drying takes a week, at this time it is not recommended to send a signal to the speaker. BF-6 forms a special film that prevents the propagation of longitudinal waves. Some people use zapon varnish for the same purposes; the excessively rigid polymer film that it forms stops me from using it. On speakers 4A-xx, the protective cap is made of molded fabric, it is better not to cover it with glue, but if the glue gets on the edges of the cap, then nothing will be terrible.
Adhesive impregnation of the cone base for woofers and mid-range speakers will also only have a positive result.

Chapter 3, she's the last.

Of great importance for the uniformity of the frequency response is acoustic design- speaker housing. If you arrange the main types of cases in order of increasing unevenness, starting with the smallest, you get the following row, regardless of whether the speaker is open or closed:
1) Ball-shaped body (half-ball for an open speaker);
2) Trapezoid of irregular shape;
3) Cylinder with a hole on the side wall;
4) A parallelepiped with an off-center hole;
5) Cube;
6) Cylinder with a hole on the top wall - disc.

Hence, we can conclude that the most technologically advanced type of housing and the preferred frequency response in terms of shape is a trapezoid, in which the speaker is not located at the geometric center.

The most delicate aspect of the speaker design is the front soundboard on which the speakers are mounted. The speaker hole, and worse if there are two, weakens the mechanical strength of the soundboard, making it prone to resonances in the midrange. Without touching on the ways of attaching the deck, in my opinion, it should be thick and assembled from separate sheets. But if the hole for the speaker is the same for all sheets, then a local cylinder is obtained. It is necessary to compromise and make holes of different diameters on different deck sheets (usually 2, 3) with increasing diameter. Smaller diameter for the outer sheet to which the speakers will be attached. It is better not to glue the sheets together, but to twist them with screws through layers of dense fabric. When placing multiple speakers on the deck, special attention should be paid to strengthening the isthmuses between them. In some cases of especially narrow isthmuses, transverse supports must be placed under them, screwed to the side walls, to give greater rigidity to the structure. The isthmuses between the speakers should be screwed to these supports.

Side wall panels, bars for fastening, it is best not to glue together, but to screw together. Seals made of thin felt (cloth) or porous rubber should be installed between the joints. The screws holding the two parts must be rigidly connected to only one of them. The screw hole in the second part should be of such a diameter that the probability of touching the screw is minimal. It is advisable to put a washer and a felt or rubber gasket under the screw head. It is better to lay the seal under the front deck 3 ... 5 mm thicker.

Some people like the spike supports for the speakers, but I am quite satisfied with the wooden "queens" with felt pads on both ends.

About the location and direction of speakers with full-range speakers, I can say the following:
the acoustic axes should be directed towards the listener, since this type of speaker has a rather narrow radiation pattern in the frequency range above 5 kHz. This can be easily achieved by tilting the front deck and facing the speakers in the desired direction. It has been noticed that the stereo panorama in its entire width unfolds OVER the speakers, so it makes sense that the height of the floor-standing home speakers does not exceed the listener's eye level for a feeling of comfort.

A lot has already been said about the choice of sizes and damping materials, so that's it.

Chapter 4 for all "happy" owners of 4A28 from "LOMO"

An invaluable service was provided by the Lomo designers in that most of the prefabricated parts of these speakers are fastened to each other with screw and pin connections, only the dust cap has an adhesive connection (the subcontractors failed - they did not send screws of a suitable caliber). This all helps with the refinement of the speakers.

I have found that three aluminum spacers between the magnet system and the diffuser housing make the greatest contribution to the color of the sound. At frequencies close to the main resonance (60 ... 80 Hz), these gaskets emit a piercing bounce. This phenomenon can be both mechanical and electrical in nature. Without going into the details of theoretical reasoning, I removed these aluminum spacers and replaced them with rubber ones. This is not an easy business and requires fearlessness of the heart, well, and certain skills. The most unpleasant moment in disassembling the speakers, and they must be completely disassembled, is soaking the dust cap. The most effective soaking agent is acetone, but it's unhealthy, so I use 96% alcohol. Using a brush of a suitable size, rubbing alcohol onto the glued seam until the cap can be removed with a scalpel gently and without damage. I was completely unable to remove a single cap, so I treated small abrasions on the HF horn, to which this cap was glued, with BF-6 glue. Further analysis of the speakers is trivially simple: remove the brackets that secure the diffuser, unsolder the flexible leads, unscrew the brackets that secure the centering washer, and unscrew the screws from the inside of the case that secure the magnetic system. I did not separate the core and the magnet of the magnetic system. I could not find a suitable tube size for their centering, and without this, the reverse assembly of the magnetic system will not work. In my opinion, it is enough to simply coat the joints of the steel washers and the "88" magnet with glue.
Then, to make two rubber gaskets, I took an old camera from a car. Using the aluminum spacers as a template, I cut out two rubber ones that are similar in shape. One rubber gasket is glued to the magnetic system, and the other to the diffuser housing. For gluing I recommend "88" glue. Then the magnetic system is screwed into place. It makes sense to dial under the screw head: a grover, a steel washer, a rubber washer from the same tire. The screws should be tightened to the same depth, as tight as possible. After that, it is advisable to grease the joints with "88".
The disassembled speaker provides ample space for handling. You can smear the outer diameter of the diffuser with a non-drying mastic (not to be confused with a corrugation - a collar) With the same mastic, I smeared the diffuser body from the inside: stands and a larger diameter. This must be done carefully, without getting into the joints of the speaker parts.
Next, the most crucial moments are assembly and alignment. For centering, you need to prepare 8 strips of thick paper. In my case, the paper from the old envelope for a 5 '' floppy disk fits perfectly. The length of the strips should be such that they do not fall into the magnetic system, and the width should be 5 ... 6 mm.
The outer edge of the corrugation is carefully smeared with a thin layer of "88", as well as the edge of the diffuser body, to which the corrugation is glued. This is all dried for 10 ... 15 minutes. Then the entire diffuser structure is gently put into place, so that the mounting holes in the centering washer and the flexible leads fall into place. At this moment, you need to show maximum composure, so as not to glue the corrugation ahead of time, which adheres over the junction. The corrugation can be completely lowered after the speaker coil takes an axisymmetric position relative to the core of the magnetic system. There should be no obvious displacement of the axes to the eye. Then the corrugation is carefully pressed down with your fingers. It takes longer to explain than to do.
For centering, the strips of paper are carefully vertically pushed into the gap between the coil and the core of the magnetic system evenly over the entire diameter. Then the centering washer is fixed with the corresponding brackets. After fixing the strips of paper, remove and check the centering by lightly pressing with your fingers on the four points of the diffuser. When pressed, the friction of the coil against the core should not be heard and should not be felt.
After all this, it's nice to make sure that the tone from the tone generator is heard cleanly and evenly. After such a refinement, both low and high frequencies sound cleaner, not to mention the middle ones. By the way, as a viscous and non-drying mastic, I found a good remedy - putty for windows in white or tinted in pure colors. Tar putty will not work, it is too oily.

The second drawback of 4A28 is the rather high frequency of the main resonance. This is primarily due to the rigidity of the suspension - the centering washer and the corrugation of the diffuser. It is better not to touch the washer, but it makes sense to modify the corrugation. I have not found anything more effective than how to soften the corrugation with glycerin (bought at the pharmacy). But the diffuser and corrugation are impregnated at the factory with a special compound that glycerin cannot cope with; alcohol comes to its aid. All procedures are carried out with a thin brush.
I decided to soak only the grooves of the corrugation, without affecting its protruding edges. This gives the desired flexibility and retains the shape of the corrugation. So, the falling ribs of the corrugation are moistened first with alcohol, then the first layer of glycene is applied wet. Glycerin is absorbed for 0.5 ... 2 hours. On the third or even the second layer, you need to stop so as not to "overdo it", because the density of the paper in different series can be different. And then, if the corrugation is very loose, there is little good. After the third time, the frequency of the main resonance shifts to 50 ... 55 Hz. Further it is a matter of taste, but it is important to know when to stop, and remember that theoretically it will not be possible to go below 45 Hz.
The last procedure is to apply a thin layer of viscous mastic to the outer diameter of the diffuser using a 5 mm wide ribbon. and not the last rib of the corrugation.
All these procedures not only expand the low-frequency limit of the speaker's frequency range, but also smooth out the frequency response. Subjectively, side-tones also decrease.

All the work done made it possible to obtain the sound of the 4A28 "Lomo" speakers comparable to similar Hungarian speakers.
Some of the details of damping the speaker enclosures that I reported earlier are omitted here.

Chapter 5, just in case, about fine-tuning 5GDSH4

Very briefly about the revision of 5GDSH4-4.
For work you will need:
1) Window putty that does not dry out - less briquette;
2) Castor oil (sold at the pharmacy) - less vial;
3) Glue BF-6;
4) Glue "88";
5) Alcohol 96% - 10 grams (for external use);
6) A pair of stationery brushes;
7) O-ring rubber seals (5 ... 6 mm).

Any domestically produced speaker requires one or another work to improve its properties. (I want to warn you that appearance it does not improve.) Some speakers benefit from this - others, like peas against a wall. 5GDSH4 belongs to the first category. The good news is that this speaker does not require complete disassembly, you can limit yourself to cosmetic products:
1) It is necessary to peel off the dustproof cap - the main source of extraneous sounds (and never stick it again). This is done by liberally wetting the edges of the cap with alcohol. After soaking the glue, the cap is gently torn off with fine tweezers or a scalpel.
2) It is necessary to strengthen the magnetic system by carefully gluing all external connections. For this, the BF (BF-6) glue is diluted with 96% alcohol and poured into the slots and under the rivets with a soft brush. Dries up within 12 hours.
3) All paper seals are carefully cut off with a scalpel under the very spine in the place intended for attaching the speaker to the speaker case. This must be done carefully, without damaging the corrugation.
4) The top of the diffuser cone (where the diffuser is attached to the coil) is coated with three layers of BF-6 glue. It is necessary to start from the coil itself and finish, not reaching 5 mm to the connection points of the flexible conductors with the coil conductors. Drying time for each layer is 0.5 - 0.5 - 6 hours.
5) It is necessary to apply a 0.2 mm layer of a viscous mass to the corrugation of the diffuser. This mass can be prepared from non-drying window putty, softened in castor oil. Small amounts: a couple of pinches of putty and a few drops of oil. It is necessary to soften until a homogeneous mass is formed, which in consistency resembles thick sour cream. It is necessary to apply this muck in a thin layer, driving 5 mm onto the diffuser itself and not getting into place under the seal.
6) It is necessary to glue the rubber seal, regardless of how the speaker is mounted (external or internal). The seal can be made up of tightly joined pieces of plumbing, rubber, round seal (5 ... 6 mm cross-sectional diameter). The seal is glued to the glue "88". The seal should be firmly pressed against the edge of the metal diffuser housing.
7) The flexible conductors and the centering washer must be lubricated with castor oil using a thin brush.
8) Optionally, you can stick the body with the remaining putty.

Having a generator of the sound range, you can audibly control the intermediate stages of work and the final stage. To do this, it is necessary to send a signal from the generator with an amplitude of 0.5 ... 2 V, a frequency of 70 ... 80 Hz. The tone should sound clean without bounce. The loudspeaker brought to mind in its frequency properties is not inferior to the modified 4A28. For 5GDSH4, the upper cutoff frequency extends even higher than for 4A28.

I think there is no doubt that best sound can only be obtained from full-size floorstanding three-way speakers. But there are often cases when there is simply no place for them. Small speakers will usually be 2-way. The requirements for them will be slightly less, but the sound should still be good. We will discuss this option.

The first mass-produced small-sized, but high-quality Soviet speakers were 10MAS.

Acoustics 10MAS-1 from Estonia-006-stereo

The main distinguishing features were the relatively modest size with increased bass response, as well as only two speakers (to save size).

Further - more, the size of the speakers became smaller, the sound - worse. Users were glad that they could be shoved into the niche of the furniture wall, placed on the cabinet under the ceiling or on the floor. This finally killed the sound, but few people bothered, and the rattling of dishes in the cabinet with the column caused delight and pride.

What are the disadvantages of the family of such models, of which dozens have been released? In my opinion, the root of evil is in the two-band and the wrong frequency division. I believe that speakers such as 10GD-30, 25GD-26, 6GD-6, 10GD-34, 15GD-14 and the like are fundamentally incapable of sounding good up to 5 kHz, and this is the usual crossover frequency in two-way with these speakers ... By the way, about the partners of these speakers - 3GD-31, 10GD-35 and the like, you will not hear a kind word, without constructive improvements and complex filters, they do not work in the best way.

I must say that there were decent two-way speakers capable of sounding good up to 5 kHz, but they did not require small-sized enclosures, so they were not used.

Progress moved further down the road to absurdity, The speakers were getting smaller, the speakers for them too. Systems 15АС and 25АС were produced in large editions, there are still a lot of them on the secondary market at reasonable prices. It would be tempting to improve them with minimal rework and expense.

Acoustic systems 15AS-109

I think these columns are worthy of improvement. If their body is not mutilated, then it looks good, the volume is satisfactory enough for a standard speaker, there is a FI.

Photo source: vega-brz.ru

15AS-109 installed 15GD-14 (25GDN-3-4) and 10GDV-2-16. The section is at a frequency of 5 kHz and cannot be changed, since the operation of 10GDV-2-16 below is impossible. Therefore, the sound is sluggish, gray, dull due to indistinct reproduction of the middle (the most important for the general perception of sound) frequencies. And this applies not only to this model, but also to all two-stripes in which the previously mentioned woofers are installed.

The best Soviet designers knew this very well, and to modernize such two-way bands, they suggested that radio amateurs install full-fledged midrange speakers, such as 2GD-40. Alas, the insanity of miniaturization did not allow putting something extra in tiny cases, and even in boxing, because the volume was already insufficient.

Outside birdhouse towns were offered, which sounded good, but the cultured look was difficult to achieve. In addition, no matter what they say, but 2GD-40 and the like, worked, as in the passport, up to 12.5 kHz, there is a break above, and the directivity is higher, needle-like, that is, a three-strip is needed in a new case and with new filters, only one woofer remained from the old speakers.
The option is good and I made such a three-strip, in principle, only on available Soviet speakers, but today is not about that.

Refinement of speakers 25GDN-3-4

The 15AS-109 is equipped with 25GDN-3-4 speakers, these are not bad speakers, brothers 10GD-34, but much better than them due to a huge powerful magnet. As a result, they can work normally at a volume of 8 ... 12 liters, provide a return from 30 ... 40 Hz with a decline of not 15 dB, like the S-90 and the like, but 3 ... 6 dB. Of course, the volume of transported air and power are incomparable with the 75GDN.

A common misfortune of most Soviet rubber surround speakers is its choking, which causes an increase in the resonant frequency, quality factor, and this leads to a deterioration in quality. If initially (during production) the suspensions were normal, you can try to revive them. If tight suspensions have already been installed at the factory, only their replacement will help.

What can I advise from practice. Take cotton wool, good gasoline ("Galosha" or similar), cut a circle out of cardboard to fit the paper part of the diffuser and attach it so that less liquid falls on the paper. Then moisten the cotton wool and abundantly moisten the rubber suspension from the front part.

Yes, gasoline evaporates quickly, but dry rubber greedily absorbs gasoline, changes before our eyes, from dull it becomes shiny. Of course, all work, especially with flammable liquids, requires appropriate safety measures.

So, let's drink the gap from the front part until she refuses to drink gasoline. Then we put the speaker up with a magnet and pour gasoline into the groove of the corrugation, wait until it is absorbed and evaporates. Immediately after complete evaporation, it is useful to arrange the dynamics of a warm-up for an hour or two with low frequencies at the resonant frequency (easily determined by eye), achieving the maximum amplitude, but without knocking the sleeve against the magnetic system.

If the rubber was really dry, it will change, the dynamics of the dynamics will improve markedly. Of course, it is best to take measurements if possible. In my practice, there have been both cases of resonance reduction by 20 Hz and an insignificant effect of only a few Hertz.

The problem is that after a couple of days, a partial rollback of the improved parameters occurs. To consolidate the gains, you need to use a car drive belt restorer. It is sold in aerosol cans. I think they are all about the same, I bought Belt Dressing & Conditioner from Permatex.

We cover the corrugations with foam on both sides, alternately 2-3 times (this is where you need a cardboard circle, without it there will be spots and ugly streaks on the diffuser), waiting each time to dry.

The effect of such treatment is long lasting, it is clearly present for more than six months (in my experience). The rubber becomes completely different to the touch - soft and slightly sticky, to the eye - shiny. Warm-up with maximum amplitude is also desirable.
The resonance dropped from 60 ... 65 to 45 ... 50 Hz, that is, it became like the new speakers.

Replacement of speakers 10GDV2-16

Speaker 10GDV2-16 fundamentally cannot operate from 2 ... 3 kHz, therefore it is only a replacement. The main requirement is a low resonant frequency of 1 ... 2 kHz without overshoot at resonance. I think the 2GD-36 and 4GD-56 will do, but it is inconvenient to install them, so I did not use them. I put Philips AD0142 with a resonance of 1300 Hz, the result was not bad.

This is an intermediate option before the FI setting. I understand that very few people have these Phillips, and I didn't want to put them here, since there are good complete Philips low-frequency speakers for them.

Chinese tweeters Alphard TW-302

For this budget project, I did not want to use tweeters for which the cost of one piece was higher than a couple of speakers, and the size played an important role. So I bought these cheap (but not the cheapest) tweeters.

It was interesting to listen to these “silk” domes. "Silk" here is clearly synthetic, the threads of the armature are sparse, but the material is very soft elastic, it differs sharply from plastic membranes.
The body is plastic, and this is filthy - it is scratched, there is no rigidity.

The declared parameters of 8 Ohm and 95 dB turned out to be "Chinese" - the resistance is 4 Ohm (impedance in the entire frequency band, not just measured by the tester), and the sensitivity ... I can't measure it exactly, and I don't need to, according to my estimates, 88 dB. Is there a difference from 95 dB? ..
However, the resonance is 900 Hz and 1200 Hz, the sound is not bad, the membranes can be easily replaced. In general, "the third grade is not a marriage."

Modification of the body 15АС-109

I will not dwell in detail, since it has been described many times, I will focus on the most important. This is a thorough sealing, filling all joints and cracks from the outside and from the inside. Checking with the LIMP program is desirable - the gaps are very clearly visible.

It is advisable to remove epoxy drips on the front panel with a chisel, to level irregularities.

Place a spacer tight inside between the front and rear panels. I put a block with a section of 20 × 40 mm. Place the spacer between the speaker holes.

For the Alphard TW-302 tweeters, we had to make an additional panel with a hole for the magnetic system inside. The screws are screwed into this panel through the holes in the beeper, and it attracts the head to the front panel.

Faux suede pads are cut out under the speakers. I recommend replacing the screws with more modern ones.

Fill the holes for the acoustic wires with glue, install the spring clips at the back, unfortunately, it was not possible to install normal terminals with screw clips due to lack of space.

If desired, the outside of the case can be varnished or otherwise refined. Inside, the case must be tightly filled with fluffed padding polyester, but leave a passage between the hole of the FI pipe and the woofer.

Instead of a nasty standard plastic panel, I made a frame from a thin laminate and stretched a canvas-type fabric over it. Fastening the frame to the body via Velcro is simple and no need to drill holes. Out of inexperience, I put on too long pieces of Velcro and it turned out to be oh so difficult to remove the frame!

Correct AC filters

You often see how DIYers believe that filters are something tertiary, it is enough, by audiophile standards, to put one capacitor and one coil at most.

It is my deep conviction that everything is quite the opposite - filters are the most important element of the speaker, incorrect filters can spoil the sound of any speakers. First-order filters can work with well-matched speaker pairs that have a natural roll-off at crossover frequencies without humps or overshoots. In the vast majority of cases, it is difficult for us to find such pairs.

And I am also convinced that it is impossible to quickly and correctly debug filters without acoustic measurements.
The benefits of any calculator are gulkin's, since they use resistors as models, although speakers are complex electromechanical systems with resonances and other features.

An exception is LSP CAD, and only if you feed it the results of, again, microphone measurements.

It was possible to achieve a very simple filter circuit, with a minimum of standard ratings (this was a special emphasis).

Condensers K73-16, for convenience, all details are placed on the plywood of the old filter. The installation was done with an acoustic cable with a cross section of 1.5 squares.

Here's what happened in LSP CAD

And here is the result of measurements with a microphone. Compare.

Here is the impedance graph, it never goes below 4 ohms, so the speakers will work fine with any 4 ohm amplifier.

And here is what LIMP showed in the box, where there seemed to be no obvious cracks ...

Measurements below 300 Hz in a normal room are difficult to measure due to reflections, so they are point-blank.

Measured at point-blank range of the modified speaker 25GDN-3-4, the FI port is plugged. It can be seen that at the level of -3 dB the lower frequency is 45 Hz. Find the frequency of -15 dB, as is customary for industrial speakers, from the graph yourself. After turning on and adjusting the FI, it was possible to lower the frequency, but it is difficult to bring the measurement graph due to the remoteness of the FI hole from the speaker.

I repeat, despite the low reproducible frequency, you don't need to expect the same bass as from the S-90 due to the tiny size of the cone, but this is enough for tonal balance. From my point of view, tonal balance is extremely important.

Listening to updated 15AS-109

The columns were made back in the summer. Of course, they do not pretend to be a “hiend”. They were compared with my homemade three-band three-case version on 25GDN-3-4 with fashionable serial filters, and with the Tandberg 2510 (does anyone remember this company today - Hi-End of the 70s?).

Naturally, they are inferior to both. Nevertheless, after the rework, the speakers clearly became better... I am sure that they are better than any factory 15AC, S-20, S-30, all kinds of cubes, etc. The sound is clear, clean, compared to the three-band version, there is a slight color, which is not surprising since the buzzer works from about 2 , 5 kHz, and below - low-frequency.

A prerequisite is work on a stand, at least on a stool. If the bass is recorded on a disc, it is also in the speaker, if there is no bass in the recording, then the speakers will not reproduce it either. For a normal volume level in a room, a power of up to 4 watts per channel is sufficient. "Sibilants are not annoying."

In general, the speakers play quite brightly, but not annoyingly. The tonal balance is shifted slightly upwards in comparison with the above speakers.

Their small size allows them to be placed even on a computer desk. The speakers are quite heavy, which is rather an advantage.

Total

To my surprise, the result was better than expected. Now it remains to transfer the speakers into the good hands of one of my friends, for a new permanent residence.

Thank you for the attention!

Reader's vote

The article was approved by 124 readers.

To participate in the voting, register and enter the site with your username and password. I had a dream for a long time - to buy the legendary S90 and modify them with a file in order to make a budget decision to the envy of everyone. For a long time monitoring various flea markets, I still bought on one speaker 35AC-212 "Radiotekhnika" S90 that was produced in 1981 (my peers;)).
The state of the outside on a solid 4, inside with crooked paws, no one poked. There was only one drawback - a bass driver from one speaker was killed, which was honestly reported to me, well, I really did not like the fact that both woofers were painted with silver paint (it's good that the paint is not deep paint, i.e. the mass of the diffuser did not increase much).
For 1000 p. bought a set for creativity.
We will refine it.
Oh, I feel strong controversy between supporters of improvements Soviet acoustics and its supporters to bury it completely and without turning.
Immediately I apologize for the quality of the photos, because at the time of revision, and even now, I do not have a digital camera except a phone.

Let's climb inside

After listening, I decided to disassemble each speaker to ensure that the insides match the speaker passports. As it turned out, the quality of HF is 10GD-35, MF 15GD-11A, and LF 35GD (something) I did not remember, but with a rubber not dried out suspension.
The first thing I did was rewind the woofer.
Restoration of the dynamics for me did not constitute any problems, because I did it very often in my youth for denyuzhku. Unfortunately, I did not have a mandrel of a suitable diameter, but the need for inventions is tricky and I went with a caliper in my pocket to the nearest building store. As a mandrel, I bought some kind of plumbing pipe, it seems, for 20 rubles. I sawed it lengthwise (this is necessary because after winding it will be practically impossible to remove the coil from the mandrel).
Let's add another 20 minutes for winding and centering and a day for drying the speaker. Everything, the speaker started playing without extraneous overtones and just as untouched.

Let's start with the tweeters

After listening to the result and reading the great Internet, I began to think further how to make the sound even better. Basically, all types of modifications are reduced to replacing the HF, replacing the midrange and damping the case.
Treble really doesn't sound very good. There are unpleasant overtones on the HF and the lack of voicing on the MF. The high-frequency link uses speakers with domes made of some kind of plastic / polyethylene. For comparison, I put 10 W speakers with silk domes, the HF sound became much more transparent and the side-tones that simply cut the ear disappeared. As a result, these rootless speakers about 500 rubles per pair remained in them. I bought them for a long time and the marking on them is not readable, and I don’t remember what was written on the price tag. You can also use 10GDV speakers with silk domes.

I note that at first I made one speaker and compared the sound on test discs with the sound of the original speaker. After listening, I decide to leave the alteration or return everything back. Everything was done to my favorite ear, which never seemed to let me down.

Modification of the case

Then I decided to work on low frequencies, i.e. completion of the case. Batting was bought for ridiculous money 38 r per meter of length and 2 meters wide. Having also looked at the filters made, I listened to the advice to change all the wiring in the speakers.
I dismantled all the speakers from the speakers. He took out the filter and switches. The wires can be safely cut as they are all the same for replacement.
Then I cut out the necessary piece of batting, took a furniture stapler from a friend, began to sheathe them inside in 2 layers.

We put the bass reflex pipe on the sealant and also wrap it with batting.

The next thing to do is to modify the filter.

The filter circuit is simple

I completely disabled the switches, since they are completely unnecessary. Remove unnecessary elements from the filter board.
We change all the thin conductors in the filter for normal copper wire.
Here is the filter before the rework.

And this is a copper wire about 4 squares used for almost all connections

As a result, redesigned with dividers and regulators removed


then we install it in the case and close it with batting.
We also cover the entire midrange box from the outside with a batting.

Midrange link

In principle, after such improvements, the sound changed for the better, the bass became clearer, the upper frequencies became "more transparent" and "lighter", but the middle ones still I did not like, the upper middle was missing. There was a lack of sonority in the vocals.
Having rummaged through my stocks, I found two 4GD-8Es in excellent condition. I put one speaker and compared the result for a long time. I liked the result. In one blues recording, I heard brushes hitting the main drum. Before that, I did not distinguish between them.
But these speakers did not last long in acoustics.
After listening to the modified speakers for a week, I came to the conclusion that the sound began to bore me.
Probably all this is due to the fact that the dynamic heads 4GD-8E have a very high quality factor and in a closed box have a very rugged frequency response. Unfortunately, there is no normal microphone to take measurements. Yes, the midrange speakers were equipped with a PAS made of foam rubber covering the rear openings in the speakers. The midrange box itself is filled with fluffed "eye" cotton wool.

On the Internet, they often wrote about 5GDSH-5-4 and 6-GDSH-5, about the fact that after the installation of the PAS they give out the midrange perfectly. Walking through the neighboring radio stores, I bought a pair of 6-GDSH-5 4 Ohm for 110 rubles. As far as I understand, they are installed in household electronic equipment. I glued the windows in the basket of the diffuser holder with thin batting and put them instead of the 15GD-11A, since their installation dimensions completely coincide. There is another way to refine the midrange speakers - impregnation of the suspension with mystical guerlain mixed with the blood of the orchestra conductor with acetone and applying a thin layer on the back of the diffuser. But, as I understand it, it is quite rare and in construction stores they only shrug their hands. It would have taken for an experiment because 110 r for a couple of new speakers is not a pity.

After all the operations, we completely assemble the acoustics and enjoy the new sound. I tested the sound on a homemade high-fidelity amplifier from Sukhoi (I'm afraid that true connoisseurs of Hi-Fi will spew out beams of diarrhea in my direction). in the same form of an engineering sample. I connected it all to Sb Live! Playing flac of special discs such as audio doctor. And just wav and flac disks which are specially recommended for testing the audio path.

Outcome

Costs 1000 rub. the acoustics itself
500 r tweeters
110 r midrange speakers
150 rubles batting, glue staples for a stapler, screws and other trifles
Total 1760 p.
What have we got?

Here are such nice acoustics

Further there is only my opinion and the opinion of my friends who happened to it.
My friend, the owner of the jbl floor speakers, I don't remember the model, but they cost about 20,000 for one Yamaha receiver, he unequivocally agreed that after the S90 was revised, they would replay its set.
The sound suits me completely. Walking through different salons with acoustics and listening to it, I understand that such a sound is cheaper than 15,000 rubles. one speaker cannot be bought.

PS Now they are playing together with a Simple Gumel amplifier and preamplifier VV Sukhoi. Everything is connected to the same SB Live! and works as a front to 4.0 sound for watching movies on a 37 "LCD panel. There is more than enough realism in disaster movies. I don't even think about adding a subwoofer.

Hello dear readers! Now we will dispel the doubts of the owners of budget acoustic systems, costing up to $ 300, and about the second life of acoustics. I want to demonstrate to you some of my techniques for improving the sound quality of such acoustic systems on live samples..

Warfadale Diamond 8.4

The English company Warfedale is a true English connoisseur of hi-fi traditions, a company that has been producing acoustics for listening to music and home theaters for over 75 years, thanks to Gilbert Briggs, in a village called Dale, which lies in the valley of the Warfe River, hence the name. The Diamond lineup started with the 8 series models. Having spent in search of the optimal material for the speaker cone, they came to a very light, and at the same time durable material - Kevlar, which, contrary to many, creates more questions than gets answers, but this is not so. The main advantages of Kevlar are the lightness of sound, improved detail, a wider stage due to this and, as a consequence, the surround effect. In addition, due to the same low weight of the moving system, a very light but powerful bass was obtained, and this made it possible to hear much more subtleties of the compositions than with other composite materials and even paper. Bass guitar, drums, double bass here can perhaps be compared in lightness with Japanese speakers from Fostex, where the diffuser is made of banana tree bark and has a very low weight! Now let's talk about the other side of the medal: usually, when leaving the piston mode of operation, Kevlar speakers have a sharp spike in frequency, which just falls on the frequency of docking with the HF speakers, as a result of which the sound acquires either a sharp synthetic overtones or takes on a mushy character for those who are most responsible for hearing and building a scene at frequencies of 3-7KHz. This problem is solved either by using a notch filter, or by applying additional measures for vibration isolation of the speaker diffuser on the back side and using a specialized form of the diffuser. Not surprisingly, the Warfadale campaign took the difficult second path, since the frequency response bursts were not noticed by ear. But according to the graphs on the midrange speakers, a surge was noticed far from the section frequency

Native crossovers have already undergone changes in the direction of improvements - electrolytic non-polar capacitors have been replaced, which are clearly not suitable for metal film for sound. However, the third order of filters on the high-frequency dynamics, as well as the use of ferrite cores in filters in order to save copper, to be honest, misled and made you doubt the authority of the company, because acoustics are not the most budgetary, but they save on g ...

Also, to obtain a softer sound at the frequencies of the MF / HF section, metal-film capacitors are used, which have the lowest harmonics and distortions among the available ones (do not have a timbre color). Also, a Zobel circuit is included in the crossover circuit of the woofer-midrange speaker, which compensates for the impedance component of the 6 "speaker, and capacitors are added to the woofer circuit for better matching with the midrange. worked on its own separate volume in the design of a closed box, and the woofer / midrange speaker was on a closed box and with an impedance of 6 ohms, fenced off from each other by a partition at an angle, minimizing standing waves in the case, which is certainly a plus. the rating of the woofer coil of the speaker is an impressive 6.5mH, and without a core it is only 2mH.After the final adjustment, the filter looked as follows.

In general, the sound of Kevlar diffusers not only did not upset, but also did not leave indifferent and even made it possible to stand out from the gray mass of ordinary speaker systems. One of the main disadvantages of not tuned acoustics was the presence of sharp overtones when listening to heavy musical compositions of the genre Heavy metall, power metall. Now, any composition, this acoustics clicks like nuts, leaving no listener indifferent.

Heco interior reflex 20H

The Heco brand of acoustic systems was founded 60 years ago, and until the fall of 2001 was part of the Ricoton corporation, then became the property of Audiovox, which also includes the no less famous German company Magnat.

The acoustics of the German company HECO, both remake and vintage, are a work of art and are highly valued and respected by lovers of the audio industry. Each new line when developing, it takes into account many factors affecting the sound, and before going on sale is tested in the brand's own laboratory. Adhering to the company's motto "Sophisticated Sound", German engineers, based on their many years of experience, achieve an impeccable combination of both technical characteristics, sound quality and original design.

This speaker is a bass-reflex type. A feature of this model is that it is a real 2.5-way - that is, one woofer is responsible purely for low frequencies, and the second for low and medium frequencies up to 5 kHz. Alas, this acoustics turned out to be out of order HF speakers. Since any high-frequency speakers are afraid of power overloads, they are most often the ones that fail. The high-frequency component takes about 5-10% of the total power of the speaker system. According to simple calculations, acoustics with a power of 100 pure watts usually have a tweeter per tube with a power of up to 10 watts. When calculating the crossover for HF, the nominal load on it, the resonant frequency and the sensitivity of the speaker are taken into account, and based on this, the crossovers are designed and constructed. But given the fact that either not the best quality auxiliary equipment in the form of an amplifier and a signal source, or not the correct placement in the room and the location both relative to the listener and surrounding objects that absorb or re-reflect high frequencies, or the hearing characteristics of a particular listener reveal a lack of high frequencies in the compositions, and try to compensate for them with the timbre of the high frequencies on the amplifier or equalizer. And this, in turn, is an increase in the supplied power by half, different from the nominal, due to which the coils of the HF speakers fail in a matter of minutes. The photo shows a deformed acoustic lens and a burnt-out coil.

When the acoustics were opened, a sound absorber made of yellow technical cotton wool and a crossover board were found. At the very first inspection of the crossovers, even such a renowned company showed a clear sign of economy - this is the presence of iron cores in the inductors and electrolytes, but not polar, which is also unacceptable in the region of medium and high frequencies.

The body is made of MDF with a thickness of 16 mm, which is more than sufficient even without the presence of stiffeners.I was very impressed by the clarity of the bass reflex settings - not one phase reflex system was so close to this standard - the lower register here is very elastic, clear and, despite the small volume of the speaker system, deep and not booming. The woofer mounts are made of latex rather than heavy, rough rubber, which guarantees more detailed mids and a high acceleration factor (less amplifier). The use of two woofers made it possible to achieve greater return in the lower register, which can be seen on the graph, and the thoughtful shape and design of the speaker allowed minimizing the frequency response surge at the section frequency, and making its falloff as flat as possible, which gives an advantage in sound quality over similar 6 "competitors.

Removing the cores from the coils, and blowing the required amount of wire to obtain the required inductance and replacing the already sucked electrolytes with film capacitors

K73-16 and K73-11, had to face some difficulties. Firstly, the use of a non-standard HF head entailed a change in the crossover values ​​in the HF speaker circuit, and, accordingly, in and in the MF / LF. Secondly, the cores of the coil, in addition to distortion, give some non-linear deviations in the sound, which are not visible on the graphs. Therefore, at a certain stage, it turned out that the use of the nominal ratings of the inductors would not give the proper results.

After 8 days of painstaking work on adjusting the acoustics, we managed to achieve results that would satisfy me. The sound is very detailed, open, loud, resilient and balanced. Such oversized acoustic systems were more than enough for me to sound a room of 28m 2 until the voice of a neighboring person was completely inaudible, and the higher the volume level, the larger the sound images became and the more detailed the scene objects were localized. This is one of the most successful and interesting loudspeakers that I have ever dealt with, and I highly recommend it to all discerning listeners.

Speaker system for computer JBL Creature II

Perhaps you will have to look for more extravagant and extraordinary acoustics. With its dimensions, it allows you to effortlessly sound a room of 20m 2 or more, not to mention being locally on a computer table near the listener. However, oddly enough, polyurethane foam suspensions, as well as centering washers, also from polyurethane foam, over more than 5 years of operation, turned into a kind of sticky and fragile substance resembling plasticine, which affected the catastrophic lack of midrange and the presence of extraneous sounds due to the misalignment of the speakers. With a speaker diameter of 35mm and 20mm along the internal suspension wave, it turned out to be unrealistic to find a repair kit for such a rare and unusual brainchild.

If you order from abroad, and this is mainly the USA, and very rarely Europe, then taking into account the cost of delivery, it could fit into the amount of about $ 50, which is quite incomparable with their dimensions. Therefore, thinking creatively, the only option turned out to be the use of centering washers from light broadband speakers made in the USSR, such as 4gd-8e, 3GShD-8 and others. Yes, we will lose a little in the sensitivity and maximum volume of the speakers due to the harder material of the impregnated fabric, but from the positive aspects we will get durability, a meager cost compared to the previous version.

Since, in fact, we have 2 suspensions on each speaker, we will have to fit 4 centering washers in size, that is, spoil 4 speakers.

After gluing and centering, it turned out to achieve acceptable sound, but it remained necessary to eliminate the problem of poor contact of the satellites with the left channel subwoofer.

The originality of this acoustics is that the satellites are additionally powered by voltage from the subwoofers to indicate their operability and give an even more exciting look when the lights are off. The second satellite has an additional board for touch control volume from the touch of a finger and the ability to completely mute and turn on the sound by pressing both buttons at the same time.After disassembling the subwoofer, we find a rather cumbersome amplifier board with a timbre block as well as the rational use of a bass reflex for a subwoofer as a radiator for a power amplifier.

With a box volume of no more than 5 liters, it was possible to get an elastic, clear and deep bass, clearly superior to the competitors of budget acoustics Sven, Edifier, LogitekAfter opening, cold soldering was found on the left channel of the satellite socket.

Summing up, I would like to emphasize that this acoustics has not only an original design, advanced control technologies, but also excellent and loud sound for its dimensions and clearly outperforms its budget competitors.

Three-way speaker system Heco Precision 100.

Previous articles have mentioned the quality and history of this brand, so let's jump straight to the overview. This speaker system in the design of a closed box, with a volume of 24 liters on an 8 "" Westra woofer and 2 "" mid-range dome head and a 0.75 "" dome tweeter, was in average condition: the presence of extraneous holes on the decorative covers of the tweeter and midrange speaker they slightly spoiled the appearance of the acoustics, and the complete absence of crossovers, as well as torn solder terminals in the mid-range speakers and partially damaged coils, clearly spoil the first impression. However, if you look at it through the prism of optimism, then these disadvantages can be translated into advantages. For example, solving the problem with the midrange coils will make it possible to do without replacing the native coils, which will save the budget and preserve the maximum reliability in the sound. The absence of crossovers is encouraged, since the presence of cores in the coils and electrolytes instead of non-polar film capacitors will clearly not benefit high-quality sound. The presence of non-original woofers and tweeters is a controversial issue, however, due to better crossovers and painstaking work on setting them up, it will clearly put them in a more advantageous position than the original.

After measuring the frequency response and impedance of all speakers and the subsequent rough calculation and assembly of crossovers for them, we turn to the most painstaking moment - a selection of filter orders for our speakers.

It was not possible to find practically any useful information about native crossovers other than a photo of their appearance on the Internet, so I had to calculate them from scratch. Let's start with basic requirements for speakers. It is recommended to cut off the dome speakers with a filter of at least second order at a frequency of at least 3 octaves higher. Therefore, the frequencies of the LF / MF section are selected no more than 1 kHz in the second order from the side of the midrange speaker (as indicated in the passport), and the MF / HF -5 kHz is also in the second order, from the side of the HF speaker. From the side of the low-frequency speaker, we must use a Zobel circuit to compensate for the inductive component and a second-order filter, and from the side of the mid-range to the high-frequency, the first-order crossover boasted a cleaner and more detailed sound.

Another plus turned out to be the presence of a factory sound-absorbing material - mineral wool - an ideal sound absorber that can only be used in a closed box design, since its harmful particles are blown out through the opening of the phase inverter, and it is not very useful to breathe with glass wool.

Having glued the mounting holes of the tweeter and midrange speakers with sealant, we fix the non-standard woofer with wood screws. No air leaks were detected while listening to the songs. To eliminate the defects of the midrange of the dynamos, a sleeve was turned to fit the inner size of the coil and then ironed and given its original shape. After a long and painstaking work on centering, the result of which can be estimated by the absence of wheezing and crackling on the piano, electric guitar and violin, it was possible to achieve an almost indistinguishable sound of two speakers.Paying attention to the level controls of the midrange / treble speakers, we can safely say that they are of much higher quality than those produced in the USSR and used in three-way acoustics of the Amfiton type, however, in my experience and advice from more experienced colleagues of electroacoustics, more reliable sounding and more reliable for the speakers themselves are L-shaped attenuators made of fixed resistors.

After the work done, we can evaluate the result. The sound turned out to be very light, transparent in the mid-range due to the light dome mid-frequency speaker, and despite such small dimensions of the acoustics for the 8 "woofer, it was possible to achieve a sufficiently elastic and powerful bass. I am sure that this combination is in no way inferior, and even wins in sound reliability due to a more correctly tuned crossover and uneconomical use of materials in order to obtain the proper result.

Two-way speaker system Sven HP770-F.

for reasons that I will discuss later, the last tweeter immediately went out of order due to exceeding the power supplied to it. The second tweeter was native to the home building. Since it has a certain shape, designed for a gray horn-patch on the HF, which lifts the frequency response in that place,where should be its own roll-off, which the design engineers of this acoustics have played in order to be able to use the simplest first-order filter,

then there were two ways to solve the problem of burnt RF:

1) Or look for a similar tweeter from the same acoustics on the Internet, which gives little chance of success

2) Or make two identical mounting bezels for new identical tweeters.The search for such a speaker was unsuccessful, so I had to come to the second option.

The use of two woofers and the wasteful volume of the cabinet allowed not only to expand the directivity, but also to increase the sound pressure in the low frequency region, which gave the advantage in the form of deeper and more reliable bass and minimized the effect of baffle-step - the lack of low frequencies, which is especially felt at low volumes ...But the use of rather senseless and weak partitions in the case between the speakers, as well as the use of a core in the inductor, did not allow the full potential of this acoustics in the factory version to be fully unleashed.

Therefore, the first thing it was decided to strengthen the hull. It was cut from a wooden bar 25x25 mm, 3 spacers in each column in the places between the factory partitions:

After this simple manipulation, the body at the same time literally stopped “Howling” in the middle frequencies, the mid-bass drum parts in the form of drums and bass guitar became more clearly articulated. After that, it was decided to completely rework the crossover-cores from the coil, native Chinese polypropylene capacitors were dismantled, which are clearly inferior in sound even to the domestic K73-16. Also, using first order filters for these speakers is clearly a wrong decision, since the 6 ”woofer has an uneven frequency response after roll-off. In addition, there is a clear increase in impedance that affects the sound quality,

which also needs to be compensated by the Zobel chain.

In the tweeter circuit, a separate correction circuit was calculated to compensate for the unnecessary rise in frequency after the falloff frequency, which gave the sound an unpleasant color in the form of causticity, harshness and the desire to make it quieter when listening to complex symphonic or rock compositions.

However, even after correcting this surge, a certain sharpness in the sound remained. This drawback was eliminated by replacing the capacitors in the K73-13 tweeter circuit with more neutral K73-11.

Despite the use of rather coarse rubber suspensions in the woofer / midrange speakers, it was possible to achieve a fairly clear localization of objects and lightness (the so-called "air") in the sound. After a long tuning of the acoustics crossovers and the use of second-order filters with correcting circuits, it was possible to achieve a very velvety timbre, similar to a tube sound. Now these acoustics easily reproduce not only instrumental classics and rock, but also more complex genres such as power metal, symphony rock, jent and others. And once again we were convinced that the Sven speakers have good potential, which can be realized with time, hands and head!

Hans Deutsch

Hans Deutsch - famous sound engineer, engineer originally from Austria, invented a number ofHans Deutsch loudspeakers were delivered from Europe with out of order tweeters.

When opening the case, several signs of economy are striking at once:

1) The thickness of the walls of the case is thin - 10mm, mdv. Even for such dimensions it was worth making at least spacers.

2) The speakers are mounted to the cabinet without a seal, which leaks air and, as a result, hides the depth of the bass, distorts the mids and spoils the overall sound experience.

3) The absence of any sound absorber, which gives the effect of "kick" at low frequencies and "howling" at the middle.

4) The simplest crossover filter of the first order, and even with the use of a core on the crossover coil of the low-frequency speaker in order to save money, speaks of incompleteness and undisclosed potential.

All these shortcomings turn the sound of constructively well-made speakers into a more budgetary niche of reproduction quality, a level slightly better than the factory Svens.

Fortunately, however, these drawbacks are removable. Some can be done quickly and independently, and some, such as crossover selection, tuning, bass reflex tuning and sound absorber placement, require more time and attention and specialized skills.After finalizing the case, the acoustics looks like this:

Upon completion of the rewinding of the tweeters, and the finalization of the case, you can start setting up the crossovers. I repeat, the speakers are made very competently - low-frequency 6 "on a soft fabric suspension, wrapped in a wave in the opposite direction, allows you to expand the range towards the HF, making it wider, and allowing better docking with the HF speaker. Therefore, having seen the measured parameters of the frequency response and frequency response of the speakers, we can conclude that there will be enough second-order filters and they will fit on the original filter board.The final tuned crossovers have the following, more imposing look:

By placing a bundle of fluffed technical cotton wool in the speaker system just above the center, we managed to get rid of unpleasant overtones and howling.

However, the only drawback that did not disappear from the above measures is the barrel effect. With a more detailed study of the frequency response, it was possible, and after measuring the Thiel-Smol parameters for the woofers, it was possible to find the reason - the incorrect setting of the phase inverter. By lengthening it by a few centimeters, it was possible to finish off even greater bass depth without losing attack, which can be considered an absolute success.

So, impressions: for a two-way speaker system of this size, it was possible to achieve excellent depth and bass processing results, and the correct design of the woofers made it possible to achieve a very detailed and transparent sound. Ideal for rooms no more than 15m2 and tabletop.

Magnat Monitor C

Shelf three-way speaker system Magnat monitor C is the best small-sized, three-way speaker system in a closed box design that I have ever encountered.

Needless to say, the case is made of MDF material with a thickness of 16 mm, the linear frequency response and impedance of the speakers allow using the simplest, but the most phase-linear crossover filters of the first order without Zobel compensating circuits - not every acoustics can boast of this.However, polyurethane foam suspensions (PPU), due to the detrimental effect of ultraviolet radiation, the difference in moisture and temperature, simply crumbled, so they were immediately replaced by a woofer / midrange speaker. smooth impedance up to 5KHz, which is very rare for speakers of this size, especially for the production of the USSR, where in the dynamics of 35GDN it was possible to hold out no more than 500Hz due to the low acceleration factor.

The mid-range speaker of the diffuser type has such a linear frequency response and impedance towards high frequencies that, if desired, it makes it possible to expand its use as a tweeter, or use a first-order filter without a doubt. The design is very similar to the domestic 3GD-31, but in no way comparable with it in quality.

Crossovers also deserve special attention: yes, non-polar electrolytes were still used, which should be replaced immediately, but for the first time among all vintage European technology, ferrite cores were not used on coils for the sake of economy.

Replacing non-polar electrolytes with film electrolytes allowed for a more open and detailed sound in the mid and high frequencies. However, the revision affected not only the replacement of electrolytes. The values ​​of the inductors in the area of ​​the MF / HF section have been changed in order to obtain a more pleasant, non-metallic timbre in the high frequency area. In addition, the midrange attenuator has been redesigned to be L-shaped. This made it possible to relieve the speaker from the negative influence of the frequency of the main resonance and reduce distortion, and as a result, to obtain an even better sound.

This is especially true when using first-order filters. It is worth adding a sound absorber, but not much.

The listening result after the final adjustment was simply confusing: the use of first-order filters paid off - the sound came out very natural, monolithic, assembled without obvious deficiencies / excess of any frequencies and transitions-steps between the speakers with different acceleration factors. In short, it is very reminiscent of the sound of a high-quality broadband speaker, which is quite worthy for a three-way acoustics.

Improving the sound of the Grundig Aera 3-way speaker system

The three-way speaker system Grundig Aera is a rather rare specimen, but at the same time very worthy and interesting. In terms of playback quality, they are only slightly inferior to Magnat on some tracks. A special feature of this acoustics is paper tweeters. Possessing a not very linear frequency response, they made it possible to achieve a very soft timbre of sounding in the upper register. However, it was in this instance that there were some flaws, either from abroad, or after the previous master, the following shortcomings were revealed:

The most budgetary foam suspensions from the broadband domestic speaker 10GShD-1 are glued on. Everything is fine, but the shape of the suspension did not allow achieving the necessary compression of the woofer due to the limitation of the diffuser travel,

- Some incomprehensible crossovers were made, but clearly not factory ones, which are not credible in appearance, not in sound:

Obvious savings are noticeable - a minimum of copper at a maximum of cores, and too low-voltage and small-sized capacitors in crossovers - which is fraught with their hasty failure - everything is done to save on sound.

One of the mid-range speakers wheezes, either off-center or has already been repaired. Therefore, it was necessary to carry out its complete disassembly, alignment and assembly. All the same, it was opened before my intervention for some reason, and after assembly, slight differences in sound were noticed.

After the final calculation of the crossover, it looked like this:

Additionally, a spacer was used between the side walls to increase the rigidity of the body.

The result was impressive: This is the second small-sized loudspeaker in a closed box design after the Magnat Monitor C, which boasts not only a decent and deep low register, but also impressive, detailed mids and highs. Such acoustics can handle any genre of music.

P.S. After replacing the hangers, traces of the old ones remained, since it was almost impossible to remove the traces of the foam rubber from the hanger that had been embedded in the top layer of paper. And it was somewhat larger in width.

A technique for improving the sound of the Sven KF-21 active speaker system and its passive counterpart Sven HP 830b.

The Sven speaker system is a very hot commodity in the budget segment, and has such trump cards in the pocket as fairly well-designed speakers, which, if properly configured, will leave other speakers in this price niche out of competition.The KF model among Sven is the top model in the brand's lineup. Among distinctive features from the budget line, it is worth noting the presence of second-order crossovers - two coils and two non-polar electrolytic capacitors, which are not suitable as crossovers, will already give less distortion than polar ones. Also, the presence of fairly large enclosures, but rather thin-10 mm chipboard, the presence of sound-absorbing material, as well as a good power amplifier unit with a well-organized power subsystem in the form of a powerful transformer and capacious electrolytes.

However, the presence of cores in the crossover coils, as well as the other disadvantages listed above, indicate savings, and therefore the undiscovered potential of this acoustics.

Let's move on to eliminating these shortcomings. We make a partition between the side walls. I draw your attention to the fact that the baffle has a large contact area, minimizing vibrations of the walls more effectively than a spacer from a bar and stiffening ribs on the walls, but deducts more useful volume in the body. Since the latter is sufficient, the partition will be ideal.

When measuring the residual capacitance of the capacitors in the power circuit, the capacity of 6800 uF turned out to be at the proper level: one bank showed a value of 6770, the second at 6950 uF. Although the power amplifier has an acceptable signal-to-noise ratio, the binding of the TDA7377 microcircuit is almost basic. Therefore, we will try to slightly reduce the noise in the power subsystem. To do this, we shunt two supply capacitors and each of the four rectifier diodes in the bridge with film capacitors with a capacity of about 100nF.

Moving on to the finalization of the crossover filters. When measuring the inductance of the core coil in the woofer filter, the meter showed a value of 0.9mH. After dismantling the core, the value dropped threefold - 0.3mH. The use of the core is possible in a three-way system in the low-frequency part - up to 200 Hz, where the distortion is not so audible for our hearing aid. However, up to 4000Hz is unacceptable. We lose too much in detailing, localizing objects and building a soundstage - everything is too blurry and blurry.To wind a sufficient number of turns to the value we need on this frame is an insurmountable task, therefore we make a new frame and wind it with a thicker wire to reduce the reactance and losses at the lowest frequencies.

After measuring the frequency response and impedance of the speakers,

And the subsequent modeling of the crossovers, the crossover frequency of the filters turned out to be incorrect, and the need for a Zobel circuit for the woofer is necessary due to the large inductance of the speaker's voice coil (due to its dimensions) - on the face of one more saving of components - 2 capacitors and 2 resistors for each speaker. When modeling crossovers, there was no need to change the coil ratings, but the ratings of the capacitors, like the use of non-polar film ones, had to be increased. The attenuator for the tweeter was also converted to an L-shaped one, with the addition of one shunt resistor, which better dampens the resonant frequency and, accordingly, reduces distortion.

As a result of the operations performed, it was possible to achieve the formation of a uniform and detailed scene, better localization of objects and also greater reliability of the sound of instruments and their separation in audio compositions with the ability to convey the mood of the vocalists to the listener, which is not possible with every acoustic system.

Of the factory flaws in the circuitry, it is worth noting the RCA line input connectors (tulips), which loosen over time and tend to fall out, so they should be more carefully fixed on strong glue from the outside and from the inside. The bass reflexes were also glued, which, when listening to bass compositions, emitted an unpleasant creak, the tone control knobs, although of proper quality, with the setting of an average value, were additionally treated with contact grease.

To obtain better detail, you can replace the rough rubber suspensions with soft polyurethane foam (PPU), but it was surprising that I had not yet been able to achieve such detailed sounding with rubber, therefore, there is no limit to perfection, and enthusiasts can try this refinement with a better result.

The passive counterpart Sven HP 830b is quite common on the market. Of the differences in this model, it is worth noting a more massive coil in the low-frequency crossover (although it still had to be rolled up due to the presence of an iron mounting bolt, which is also partly a core). Also in this model, the heavy rubber mounts were replaced by lightweight Tonsil polyurethane foam mounts, which allowed for more detailed sound in the midrange.

The body has also been further strengthened and a sound absorber has been added.

The final look of the tuned crossover:

Improving the sound of a two-way speaker systemAcousticSound based on two 6 "" woofers and a tweeter dome, located D "apollito.

This method of placement improves the uniformity of the frequency response at mid frequencies (the most important for reproduction), expands the directional diagram horizontally, but narrows it vertically, thanks to this, the optimal listening area is noticeably expanded. Many factors that affect the quality of reproduction have been ignored by the manufacturer due to the savings. So their low weight is striking - only 5.4 kg. This is not strange, because the thickness of the walls of the MDF material is only 7mm! To increase the rigidity of the case by the decision of the steel manufacturer, stiffeners on the side walls of the case, 2 pieces on each side wall in each speaker - however, this is the most ineffective method of dealing with the vibrations of the case. As a sound-absorbing material, foam rubber of a cellular structure was used, resembling egg trays, one mat measuring 15x15 cm opposite the woofers.

Next, we see an unattractive crossover located on the board and soldered to the screw terminals (clamps) of the AC connection - made by a second-order filter (coil and capacitor) on the LF and first-order (capacitor) on the HF speaker.

The savings on crossover components are also obvious - a coil wound around an iron core and capacitors - non-polar electrolytes - all introduced quite strong distortions when playing audio compositions. However, all of the above disadvantages can be eliminated completely or to a greater extent, and the potential of the speakers turned out to be really high. So the manufacturer preferred paper as the material of the woofer cone (which allows not to lose microdynamics when playing the compositions) rather than Kevlar, polyethylene or composite materials, and the tweeter dome is made not of titanium, cellulose, but of silk, the best material for tweeters. A pleasant surprise was the rather low natural resonance frequency of 1200 Hz.

I would like to draw your attention to the material of the suspension of the low-mid-range speakers. This is a rubber-soft rubber, which, despite its durability and softer reproduction of the low-frequency register (due to its greater flexibility), has excessive absorption at mid frequencies (lead rubber is an ideal sound absorber) - these disadvantages can be described as monotony and compactness of the scene and poor microdynamics at medium frequencies (no "air" during playback). The ideal solution to this problem was the replacement of hangers with polyurethane foam (PPU). However, finding truly soft suspensions has become a challenge. At the first attempt to replace the suspensions (rather rough), by measuring the Thiel-Small characteristics, frequency response and impedance, it turned out that the resonant frequency and the total Q-factor increased significantly - instead of 55 Hz and the total Q-factor of 0.7, we got 77 Hz and the Q-factor as much as 1.5! As a consequence, a rather noticeable and unpleasant hump appeared on the frequency response and the lower cutoff frequency of reproduction was significantly reduced.

Domestic factories for the manufacture of suspensions are made only to order and with a rather long wait, and they can be purchased from import positions - from $ 6 per suspension, which is quite expensive. A week later, the suspensions were replaced. After dismantling the second suspension from the woofer from the solvent, traces were left on the painted speaker cones. However, the paint layer applied by the manufacturer turned out to be very impressive, which cannot but affect the deteriorated microdynamics. Therefore, the paint was washed off and cleaned, followed by spraying with a thinner layer of black paint. On the contrary, the appearance of the speaker system has become more strict and restrained.

After replacing the suspensions with more flexible polyurethane foam, the desired resilient resonance frequency dropped to 60 Hz, and the Q factor dropped to 0.75. As a result, the hump and characteristic "hum" at low frequencies disappeared.

To increase the rigidity of the walls, it was necessary to strengthen them not only with stiffeners on each side, but also with spacers, at least 4 along the entire height between the side walls of the acoustics. Of course, the use of partitions would be preferable - this would give a result equivalent to doubling the wall thickness - however, this would reduce the already not impressive volume of the speaker.

The experimental method was to increase the amount and type of sound-absorbing material. To decouple the speakers from the cabinet and prevent the transmission of vibrations from the woofers, rubber seals were glued under the seats of all speakers. The housings were additionally glued at the seams with a sealant.

The wiring was replaced with an acoustic one of increased cross-section - 2.5 sq. Mm.

The tweeters reproduced musical compositions with great differences from each other. The reason was poor alignment and gluing of the coils by the manufacturer. Moving on to the most laborious crossover tuning process, the problem of insufficient body volume and small wall thickness made itself felt. After listening to the audio composition, the listener was tired and a slight excess of the low-frequency register. It was decided to suppress it with a high-Q notch filter tuned to a frequency of 240 Hz.

Subsequent adjustments have shown that second-order crossovers at the bass with Zobel and second-order crossovers and an RC frequency equalization circuit for the tweeters were the ideal solution to unleash the potential of this loudspeaker.

After the work done and then listening to the speaker system, noticeable changes in sound were observed. The scene became deeper, more informative, with a rather impressive surround effect and lightness in sound, and the lower register showed itself as elastic with a powerful attack when playing audio compositions.

5.1 speaker system with an active F&D subwoofer.

The manufacturer F&D is one of the subsidiaries of Sven, occupying the budget segment of the market. Despite the attractive, strict and very impressive appearance and competitive market price, even when watching films, this system brings significant discomfort to the listener, leaving behind a dry sound, and a rather pronounced color in the lower register greatly distorts the sound and, of course, there is a desire that Then change by adjusting the equalizer, or by searching for the optimal location of the subwoofer in the room relative to the listener, however, the “kick” effect from the subwoofer pursues the listener anywhere in the room. When listening to musical compositions, it becomes clear that the system does not cope with the task of perseverance of the listener and is not enough for more than three audio tracks.

When opening the case of front-line two-way satellites, we find that there is no sound-absorbing material and any signs of an increase in the rigidity of the case. The crossover is made of an electrolytic polar capacitor with a nominal value of 3.3 microfarads, which, by its design features, introduces the greatest distortion of all possible types of capacitors.

The sound of the woofer is not limited by anything, which is fraught with large area joint radiation of loudspeakers, which do not have the smoothest frequency response, and as a result, a heavy, solid and highly colored sound without the presence of "transparency and air". Moreover, the woofer suspensions are made of rubber, which is an ideal sound absorber for microdynamics (detail) in the mid-frequency range ...

The tweeters are made of a cellulose dome on ferrite magnets and due to the small dimensions of the latter and the modest diameter of the former, the lower reproducible frequency is 7000 and does not reach for correct docking with the woofer.

However, in addition to the solid shortcomings, you can find several significant positive aspects. The enclosures of the speaker system are made of MDF, one of the densest materials available on the market, since many competitors have plastic enclosures, which makes them impossible for high-quality audio reproduction and subsequent refinement. Another significant advantage is paper as a material for the performance of woofers in satellites, which gives us a chance to reveal greater potential.

Taking into account the above disadvantages, we will begin to eliminate them. To improve the sound of the midwoofer, it is necessary to replace the rubber surround with polyurethane foam, this will improve the microdynamics at mid frequencies and expand the upper boundary reproducible frequency for better docking with the tweeter (at the expense of relative fragility, depending on the operating conditions for about 10 years).

To improve the sound of the tweeter, unfortunately, it makes sense to replace it with a better analogue with a powerful neodymium magnet and a silk dome from Philips, whose loudspeakers are highly valued among audiophiles.

Smooth frequency response, low resonant frequency as well as high fidelity of sound reproduction make this speaker out of competition among tweeters in the price range up to $ 250.

It is also necessary to apply vibration absorption measures.

(increase in stiffness by spacers) and sound absorption of the housing, experimentally choosing the amount and material and placement in the speaker system.

Next, we move on to the most important and time-consuming process - making crossovers. Due to the small dimensions of the woofer and as a consequence of the wide directivity and high acceleration factor, it was possible to achieve a fairly smooth frequency response up to 7 kHz. For the most successful frequency and phase matching, the crossover frequency was chosen as 3.5 kHz with second-order crossovers and a Zobel circuit on the midwoofer. The wiring was replaced with a high-section acoustic.

After the work done and the subsequent comparative listening to the speaker system, cardinal changes in sound were achieved. The scene became deeper, more informative, with a rather significant surround effect and airiness in the sound, and the lower register showed itself as elastic with a rather powerful attack when playing audio compositions.

By analogy, the central channel was refined with a slight change in the value of the coils and capacitors in view of the excellent resistance of the woofer-midrange speakers connected in series.

The rear acoustics are equipped with one woofer-midrange speaker, without tweeter support. Despite the fact that the requirements for the rear acoustics are the most minimal, the surround effect requires the presence of "air" and transparency in order to more clearly localize not only the sound images behind the listener, but in general to obtain an undistorted scene and lack of a proper immersive listening effect. Therefore, it was decided, to the detriment of ergonomics, to place the tweeter on the front side. It is also recommended to add a more palatal sound absorber than in the front and center speakers due to the smaller cabinet.

However, the support of the lower register in the form of a subwoofer led to rather quick listening fatigue. The reason for this is a constructively incorrect calculation of the dynamics for a rather capricious calculation of errors - 4th order bandpass in the presence of one chamber with a closed box and the second phase-inverted one.

Measurement of the Thiel-Resin parameters showed that the speaker will work perfectly in the design of the phase inverter in this volume-9L (that is, if you combine the front and rear cameras), it will allow you to have more flexible settings and much less distortion at the expense of lower efficiency, that is, a lower maximum volume ...

In order not to spoil both the external ergonomics and the internal one, it was decided to place the speaker on the right side of the subwoofer - this will allow you to spoil the appearance if you place it in front, and choose the most suitable place without destroying the internal partition, which is an excellent vibration absorber. In addition, the subwoofer will be placed in a niche, so that the sides will be closed, and a corresponding hole will be made for the speaker.

After the completed operations to modernize the subwoofer

We faced the following difficulties: the presence of a larger internal volume made it possible to reproduce lower frequencies, which means that the bass became deeper and more pleasant, however, distortions appeared due to the exit of the speaker coil from the working area of ​​the magnetic system. In science, this effect is called "clipping". If we consider this phenomenon in more detail, then there are two types of "clipping":

1) Mechanical-connected due to the fact that either the power amplifier is much more powerful than the speaker, and perhaps the above speaker can quickly both "burn" and "swing" in the literal sense of the word so that such distortions appear, or because that the speaker, in terms of its Tilya-Smola parameters, stands on the verge between the two necessary designs - Phi and ZYa or FI and bandpass, and when placed in the required volume, it necessarily needs an infra-low-frequency filter, implemented on an active filter from the first order to the third and more (taking into account the so-called ballast, which is necessary for more correct phase matching). Therefore, in order to establish the cause of clipping without special instruments in the form of oscilloscopy and a generator, you can start with the simplest steps.

Measuring the capacity of electrolytes for power is an initial action, however, as practice shows, it is far from always, readings within even 5% of deviations from the ratings will not give a big dip during operation, therefore two solutions to the problem follow: either it is necessary to measure the supply voltage during operation amplifier so that the deviations are no more than 20%, or if your device is already more than 10 years old, then you can safely change the electrolytes, and preferably a slightly larger capacity, this will allow you to get a certain power reserve.

However, in addition to the greater depth of the lower register, this did not remove the root of the problem, so it was decided to make an active second-order crossover + ballast at a cutoff frequency of 60 Hz. This made it possible to achieve a complete absence of distortion, even at peak powers, and the depth of the bass was minimally affected. In addition, the power amplifier has become much less heated. By placing a certain amount of a sound absorber and tuning the phase inverter to the desired frequency, it was possible to achieve a very deep and informative lower register, which did not really spoil but complemented the sound images.

Due to the peculiarities of the speaker placement, the rear wall with the power amplifier did not allow to close completely, creating a gap up to 1 cm in size and resting on the switching board. Because of this, we had to remove the magnetic shielding from the subwoofer speaker, isolate the magnet from possible contact with the board, and, unfortunately, as a forced compromise, get rid of a piece of the board. This rather controversial decision was made only for the reason that this "piece" of the board carried 4 "mass" tracks that did not affect the sound.

To implement this is quite simple - the input signal at any convenient point in front of the switch board must be passed through attenuators-adjustable resistors for the front, rear, center and subwoofer channels. Placing them on the rear panel directly on the heatsink between the inputs of the commutation board managed to achieve a rather harmonious look.

Having destroyed stereotypes about budget home theater systems, it was possible to achieve really decent sound not only for watching movies, but also for audio phonograms that are more demanding on sound quality. From the 1990s to the beginning of the 2000s, manufacturers, in view of little competition and low cost of resources, even in the budget segment, made fairly high-quality products with an embedded, but not disclosed potential. What can I say, the presence of magnetic shielding on the speakers, cases made of the most suitable material-MDF , a fairly simple design of the power amplifier boards, which reduces sound distortion. In addition, the speakers were manufactured under the Sven franchise, which speaks of the quality factor and impressive potential!