Improving the sound of 15GD-11A and 10GD-35 (6GDV-6-16)

The magazine "Radio" has repeatedly published proposals for the modernization of the 35AC speaker system (various modifications), providing for the replacement of heads, filters and even the housing. In the article published below, the attention of readers is offered another fairly simple way to refine this speaker, which allows you to noticeably improve its sound in just one day. It should be noted that the results of the 35AC refinement were checked only by ear, by evaluating the sound quality by experts.

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

It all started with the fact that a friend gave me a Vesna-212 tape recorder, in a non-working condition, like this:

(photo from rw6ase.narod.ru)

At first I had a desire to reanimate it, but, having disassembled it, I realized that it was better not to waste time - all the rubber in the tape drive mechanism either crumbled or cracked, and it is difficult to get belts of the required diameter in our time. And in general, this model did not differ in either sound quality (speakers in a plastic case, mixed with boards and a mechanism, ULF on K174UN7), or reliability.

So this device was lying around in a semi-disassembled form, until, passing by, I paid attention to the speakers in it. It turned out 5GDSH-5-4(former 4GD-53), very good Soviet broadbands. On the forums, I read about the good qualities and high sensitivity of these speakers, and my hands immediately itched to somehow apply them. It would be nice to replace the 2.1 set of F&D near the computer with something, it has very small and weak satellites.

Speaker 5GDSH-5

Appointment - application in open acoustic systems of the automobile radio equipment for work in rooms and in the open air. Execution general industrial, export, tropical. Loudspeaker head of electrodynamic type, full range, oval, with unshielded magnetic circuit. The diffuser holder is made of stamped steel. Conical diffuser with sinusoidal suspension made of paper pulp. Centering washer and cap made of impregnated fabric.

Specifications

Effective operating frequency range Hz 100 ... 12500
Level of characteristic sensitivity, not less than dB 92.5
Working power W 1
Uneven frequency response dB 14
Average standard sound pressure Pa 0.28
Total harmonic distortion when supplying power corresponding to the nominal sound pressure,%, at Hz frequencies
below 1000 5
above 1000 3
Rated electrical resistance Ohm 4
Maximum noise (passport) power W 5
Maximum continuous power W 8
Limiting short-term power W 15
Main resonance frequency Hz 150+-30
Total quality factor 1.3+-0.5
Dimensions mm d125x49
Weight g 600

Details of the construction of the voice coil

Wire grade Hz PEVL
Wire diameter mm 0.14
Number of winding layers 2
Number of turns in the 1st layer 43
Number of turns in the 2nd layer 40
Ohmic coil resistance Ohm 8 +-0.6
Voice coil height mm 13
Inner diameter mm 15.4
Outer diameter, including winding mm 16.1

Before that, I had never made acoustics with my own hands, but I read a lot and knew that one cannot do without case calculations, measuring Till-Small parameters and other sacraments in this matter. And it became interesting to me how the speakers would sound, made without any calculations, anyhow and from anything.

Since, according to the passport data, 5GDSH-5 above 12500 Hz do not sound, it was decided to add high-frequency speakers to the speakers. We go to the radio store and buy the best of the cheapest Alphard tweeters, as much as 13 UAH apiece. We estimate the minimum dimensions necessary to fit 2 speakers in the column, we calculate the depth according to the convenience of the speakers on the table.

From the scraps of laminated chipboard available in the house, we cut out the details of the cases. In order to cut smoothly with a Chinese electric jigsaw, many years of experience and a steady hand are needed. We have neither one nor the other, so everything turns out pretty crooked. In the front panels we cut out holes for the speakers - a small one with a core drill for wood, a large one with a “ballerina”. We collect everything to the heap on self-tapping screws, we sink them deeper into the panel. Here's what we got:

From the inside, we coat the joints with silicone:

We putty the surfaces with putty on wood in several passes, trying to achieve even planes. Then we glue it on the outside with a self-adhesive film, and on the inside with a sound absorber based on foamed rubber:

Installing speakers. We connect the tweeter in parallel through a 4.7 microfarad capacitor. We coat the joint of the speakers with the case with silicone:

People say that the 5GDSh-5 speakers sound good in an open case, so the speakers do not have a back wall.

Control listening showed that the speakers sound good at medium and high frequencies, vocals and acoustic instruments are remarkably transmitted. Low frequencies are not enough, but you should not expect them from these speakers. I tried to drown out the volume of the speakers with rags - the impression is ambiguous. Low frequencies become deeper, but detail is lost in the middle ones. The most acceptable result appeared when the speakers fell into place near the computer monitor - the volume is not muffled, their back walls are almost close to the wall.

The final touch is to cut out the rings from the lids from mayonnaise buckets, stretch and glue the radio fabric to them with superglue, and glue them over the holes of the broadband.

7240

Experiments with the acoustic design of broadband speakers produced in the USSR give excellent results in terms of sound

It is necessary to play it safe and take to the country, along with Japanese broadband 3.5 "something else in return

About acoustics calculations and my attitude to this

I was visiting Mikhail Urakov, we talked for more than 2 hours. Time flew by completely unnoticed. We talked about speakers, diffusers, Teragaki acoustics, asymmetry, and psychoacoustics... Mikhail is a very interesting conversationalist, he knows a lot in various fields. We could have talked for a few more hours, but it was time to leave. Overall great, well spent time.

When he worked as a programmer in the department of engineering calculations, he was engaged in writing computer programs for calculating car parts for the Automotive Research Institute. Since this computer calculation had to be absolutely complete, it was necessary to first take from the technical library all the literature previously written by different authors on the calculations of this part. Usually it was 5-6 works, sometimes more than ten. And how I cursed when I tried to put all these calculations into a single complex, taking into account the works of all authors. It was extremely difficult to do this, since everyone had their own calculation, taking into account their own characteristics, it is not clear from what considerations they were chosen. Well, accordingly, everyone got a completely different result for calculating the same part. Sometimes it just reached the point of absurdity, the calculations were so different (and the results, respectively) that doubts arose about the sanity of the authors.

But this does not reach the builder Alexander, he has his own way - the construction one. Well, Ephrussi himself, and Malinin himself did the calculations. Yes, I saw a bunch of such Ephrussi and Malinins, sometimes they wrote such rubbish. Horseradish without a bottle will figure out how to dock them with other authors who wrote the same rubbish, but in the opposite direction. And all this for the calculation of the same detail. In audio, exactly the same picture occurs with the calculation of output transformers and horns. And by and large, as I suspect, and with all other calculations. Therefore, I rely only on my ears, they are more authoritative than all the big names in audio technology.

Experiments with broadband

Today, before leaving, I completed the second column and put a 4GD-28 broadband there. He stood in some kind of receiver, he looks ugly, his life has battered him. Unlike 4GD-35, its paper is looser, not so dense and thicker. It seems that the diffuser was not stamped, like in 4GD-35, but freely cast. I listened to him a little, I liked his sound more, it is freer, fluffier, more intelligent, or something. It works better on reproducing small nuances, the sound is thoroughbred and soft and at the same time very clear and musical. Perhaps, in this acoustics I will install exactly 4GD-28, it sounds very cool, you will listen. I don’t know whether to cover the diffuser with propolis - I’m afraid to spoil it. Factory impregnation, probably, has already evaporated over these more than 50 years, and whether it needs to be restored with propolis. Although even in such a ugly form it sounds very cool.

By the way, I listened to Vitaly's digitization. Before, when I listened to them in stereo, I had complaints about them. But in mono, I listened to one column - they sounded surprisingly great. I listened to everything, could not tear myself away - they sound great. Why did it happen? And FIG knows. But the fact is that his digitization in mono is simply incomparable, but in stereo - not so much. Anomaly…

For a long time I dreamed of trying one very interesting acoustic design, but how it will sound is unknown ... Since no one has done anything like this. Do it in large scale somehow I didn’t want to without a preliminary acquaintance, the costs are too high with an unknown result. And then, when sawing plywood for my last project, there were 4 pieces left measuring 360 by 430 mm. The size is certainly small, nothing good seems to work. And then I remembered that my friend gave me a pair of 3.5" broadband speakers from his broken TV, which, according to him, sounded very decent. But what if we try them? Size 360 ​​X 430 mm may be enough for them. try, and again - without formulas, without calculations, without Aldoshina's literature, without devices. By the way, here they are in the photo - handsome! The diffuser and viser are thin paper, a decent "motor", shielded by 8 ohms, made in Japan.

Then I thought, but I need to play it safe and take something else in return along with Japanese broadband 3.5 ". This is in case they do not sound in the design in which I want to try them. Also broadband and also small - 5" max. Useful to rummage through the bins, found two pairs of rare speakers 2GD-3. One is in perfect condition, the second is a little worse, but also "on the go". Well, one more should be taken, perhaps, just in case. The choice fell on 4GD-53 (4GDSH-3) with a diameter of 4.5". All of them have different size. I'll start with the Japanese, if you don't like it - the next 4GD-53. If this one doesn’t work either, then I’ll put the best one: 2GD-3. I found another broadband 1GD-4A new, in the package. And how I forgot about it and didn’t take it to the dacha for experiments ... And after all, I had listened to it before, and I really liked its sound. Here, many, probably, are at a loss as to why I am experimenting with small broadband speakers. And I'll tell you! Many people know about horn drivers. What is their main advantage? The membrane (diffuser), and the whole movement is almost weightless. And hence - the almost complete absence of inertia during its movement. And as a result - a very fast sound, clear, detailed, accented and, as a result, perfectly conveying all the nuances of sound production and voice leading. And that means the feelings of performers and musicians, their professional skills. But, there is also a "but":

• They often have a membrane (diffuser) - metal, sometimes a synthetic film, there are practically no paper ones. And it affects the sound;
• Even the best drivers "pull" from 500 Hz, not lower. And this means that they without fail woofer required. And this is already a two-band, and not a SH sound from one speaker;
• Their mouthpieces are almost always made of metal or plastic, and this affects the sound;
• Horns, whatever they are made of, have their own peculiarity of horn sounding. Of course, wood is better, but they are almost never used.

And since the drivers have both good qualities and even more bad ones, I thought - why not experiment with small widebands with a paper cone? In the sense - and what can be squeezed out of them if you set yourself this goal. You ask - why? And I will answer you - in them the movement is also almost weightless (more than in drivers, but still), and, therefore, its inertia is small. Hence the fast clear articulated sound and, as a result, good musicality. I was convinced of this already two years ago, when I started experiments with them. For two years now, a 5" broadband has been playing in my dacha in a rather large, relative to its size, horn. Of course, I would not demand bass from it from 20 Hz. But from 60 Hz it works quite fully. You say - not enough, it is necessary with 20 Hz, but who needs it and on what kind of music? For me personally, this is quite enough for certain music (A - trash, I don’t listen to heavy metal). No, the organ there, of course, does not "go" fully. and timpani. But everything else, even the double bass, is already quite. But what speed, what clarity, detail, articulation! What small nuances of music are revealed! 5" - possible, but less ? Therefore, 3.5 "and 4.5" speakers were chosen with them in last days and worked.

I understand that 60 Hz is not enough, and the acoustics should have a margin on the bottom. One broadband is not enough. Theoretically, you need a shovel to work with 40 Hz, and hence the amplifier needs a more powerful one. How to listen to a large symphony orchestra if there is no bass, you can’t hear a big drum with a double bass ... But in practice, on a broadband with a size of only 5 "everything is audible - excellent. Double bass - no questions asked, but timpani - and them, in time from time of the whole concert, three or four percent.You can sacrifice the timpani, but at the same time win the excellent sound of the remaining 96-97 percent of the music.

I started with a broadband 3.5". Although I don’t know whether it is a broadband or not, I would have to remove the frequency response. But it’s all in a hurry. As it turned out later, it’s more like a midrange. There was no spectrum analyzer in the country, I used a test disk, therefore - no I can only say one thing - I listened at a volume of 2 watts from a distance of 4 meters from a test disk. A frequency of 70 Hz is already audible, but weakly. However, frequencies of 80, 90, 100, 125 and 150 Hz are approximately the same at the same level. From which I concluded that this is more of a midrange speaker, and not a broadband speaker. Although it looks cool, the rubber suspension means it is long-throw. But because of the long stroke and low sensitivity. Maybe he should have been asked 10 watts of heat, but the transistor amplifier was too lazy to connect. And on a tube with two watts of power for bass, one fart, although marked. But the midrange and treble are quite at the level, you can listen, not bad for such a kid. shield, then applied the design with which I wanted to riment. Of course, the bass raised a little, but quite a bit. So this broadband will work well as a satellite with low-frequency support with one or two subwoofers. Then, later, I'll try, although 2 bands are somehow not very good for me.

Amazing broadbands from the USSR

Then came the turn of 4GD-53, at first also on the shield. This one is already 4.5 "... progress! I turned it on and was stunned ... It plays - super! I don’t want to turn it off. It sounds great, I was just shocked ... I was so impressed with its sound that I forgot about the experimental acoustic design. Ah, dike, I think I'll make this broadband - mini AML +, since it sounds so great. And I did ... I put it there, turn it on - it sounds disgusting. It won't work. I put it back in the shield - I don't want to turn it off again. I don't know that the designer was cheated there, but it turns out that he is only a shield. Even the OP, which is AML +, is no longer suitable. It’s not worth talking about anything else. Here are your calculations ... What the hell are the calculations, there’s only one heresy! Only ears, ears, nothing more By the way, it sounds quite full-fledged Hz from 60-70. Speed, drive, clarity, articulation of sound - just awesome! But only in the shield. I'll make him a bigger shield, so 450 X 450 mm in size, there he will play incomparably.

There was a mini AML + ... Well, where is it? But I brought another broadband: 2GD-3. This one is already 5". I remade AML + a little (from 4.5" to 5"), put this speaker there - it sounds great. Here are the calculations for you! 2GD-3 is the same broadband for open design, like 4GD-53. And one AML + did not accept, and the other - for a sweet soul. Of course, you can count for a long time and hard, even - whole year. But then all the same, everything will have to be redone, not in accordance with the calculations, but on the basis of listening. And not the fact that the calculations can be left. And most likely you will have to fine-tune them or completely throw the dog down the drain, along with a year spent on useless calculations.

Yes, I completely forgot. Before that, I experimented with two almost identical speakers 4GD-35 and 4GD-28. In fact, they are almost the same. Well, so - for 4GD-35 the best sound turned out to be with a slotted circular phase inverter formed by a reflective board. But 4GD-28 categorically did not accept this design, the sound was vile. And only when I removed this board and moved to the almost open box, the speaker sounded as it should, that is, great. And here's another example for you - broadbands are almost the same, which means they should sound the same in the same design, according to calculations. And in fact, they sound best in a completely different design. Of course, I understand that the deaf or completely deaf have to do everything according to calculations. I understand, but I feel sorry for them, because - according to calculations without fine-tuning by ear, they can only - shit or something like that. By the way, this applies not only to acoustics, but also to everything else in audio. Calculations by calculations, but the final decision is made only according to the results of listening and nothing else. What I wish for everyone else.