How to make active speakers from s90. Refinement of the S90 or how to make them “sing” at minimal cost. Speakers and other "trifles"
Actually there are four ways, not three. But we will not describe the first way - throw it away. We have plenty of stuff in our dacha and garage...
The main disadvantages of the S-90 series speakers.
1. Small housing volume for the woofer. Consequence - muttering low frequencies.
2. The bass reflex is designed for a frequency of 20 Hz. The consequence is large low-frequency distortion.
3. Worthless midrange speaker. The consequences are disgusting midrange and overtones.
4. Low resonance frequency of the tweeter. Consequences - "quacking", hissing.
5. The filter is designed taking into account the previous shortcomings. The consequence is that when modifying any unit, the filter must be changed.
6. The body is not rigid enough and is not “damped”. Consequences - vibrations, overtones, "barrel".
7. Etc. and so on. ...
We study and dare
While drinking beer, we reach three truths. There are three ways:
1. Lightweight and effective.
2. Medium difficulty. More shamanism and snobbery. Some sound improvements compared to point 1.
3. Super complex, time consuming and super efficient. In reality, you are trying to make new speakers. It all depends on the quality of workmanship and musical flair. If nothing works out, then no one promised you anything. I'll describe everything. I recommend the 1st way to start. Its value is that it does not take much time, you leave all the components of the speakers. Minimum of scarce parts and costs.
ATTENTION! ATTENTION! ATTENTION!
1. When carrying out all work, ensure that the phasing of the speakers is correct. If you have not encountered this yourself, invite a specialist - electronics!
2. Remaking the speaker 15 GD - 11A is an irreversible process. If you are not careful, the speaker has one path - to the trash can, and you have another - to the market.
The first way. Lightweight and effective
1. Mid frequencies are the main emphasis. By reworking the speaker, we will make it work in piston mode, increase the upper limit frequency, remove overtones, increase sensitivity, improve directivity, and dampen it.
2. Let's move the speaker to the range from 31.5 Hz, instead of 20 Hz. There will be less muttering.
3. Suppress the resonance of the high-frequency head.
4. Let’s calm down the sounds of the building
We buy a Soviet tennis ball from a store. Chinese and others are not suitable. They have different material. The ball should be exactly the same as in distant childhood for 8 kopecks. As a last resort, you can take it from friends or in the tennis sports section. We buy epoxy resin (a little, maybe 1cm cube), glue (Supercement, Mars, Argo, etc. - hard after hardening), a couple of simple pencils, any medical bandage and cotton wool.
Let's get creative. We saw the ball in half along the seam. The seam is visible to light. It is overlapped and 1 - 2 mm wide. You need to cut in the middle of the seam. I sawed with a Nev blade, having previously made notches on it with a sharpening stone. After sawing, align the cut line on sandpaper and sand the outer surface of the ball with fine sandpaper. If there are large deposits inside the seam area, then they also need to be removed. When working, the ball must be secured with plasticine on a Mars battery (a film case, a jar of fish food, etc., according to your imagination) at three points. It's enough. Plasticine is removed later either with a dry cloth or by wiping with gasoline. Once the surface of the ball has been treated, do not touch it with your hands. Grind the pencil leads on sandpaper. Dilute epoxy resin with double the amount of hardener. Cover the surface of the ball with the thinnest layer. If necessary, excess glue can be removed with newsprint. Sprinkle with graphite and shake off excess. It is necessary to ensure that the white plastic of the ball does not show through the graphite. If it shows through, it means the layer of epoxy resin was small. Need to add. Once everything is done, let it harden.
Assembling a 3 KHz filter. To do this, we take a 4.7 Mf capacitor and a 0.6 mH inductor. You can take a capacitor from 4 to 7 mF and adjust the inductor to it. In order not to bother your head with unnecessary formulas, the simplest thing is that the product of the capacitor capacitance in microfarads and the inductance of the inductor in mH should be equal to 2.82. Let's say the capacitance of the filter capacitor is 6.6 μF (MBGO and MBM with a permissible deviation from the nominal value of ±10%), then the inductance of the coil is 2.82: 6.6 = 0.43 mH, (the winding contains 150 turns of PEV-1 0.8 wire , wound on a frame with a diameter of 22 and a length of 22 mm with a cheek diameter of 44 mm). Using these data, it is possible to assemble a circuit without an LC meter, since it is not the exact value that is important, but the “capture” of the resonant frequency, which has a certain spread. We attach the capacitor and inductor to a piece of fiberboard and solder one terminal of the coil to the terminal of the capacitor. We solder wires 40 -50 cm long to the free terminals.
Let's disassemble the column. We remove the low-frequency speaker, the mid-frequency speaker, take out the glass from it, remove the high-frequency speaker, remove the decorative trim, remove the phase reflex (on some speakers you will have to unscrew the filter). We take half of the dried ball, polish it on the outside with suede or newsprint and glue it over the dust cap of the mid-range speaker head with hard glue. You must ensure that there are no un-glued gaps between the edge of the ball and the cap and that the ball is glued exactly in the center. We do the same with the second midrange driver. Leave to dry.
We screw a homemade filter onto the back wall of the speaker (inside) opposite the tweeter. Solder the wires from the filter to the output of the high-frequency speaker. Which one goes where does not matter. We remove the connectors from the back wall of the speakers and solder the wire going from the amplifier directly to the filter. We saw off 10 cm from the phase reflex pipe with a hacksaw along the center line. We wrap the phase reflex pipe and the mid-frequency speaker glass with a layer of gauze and bandage it. It is necessary to check whether they will enter their nests after this procedure. If they do not fit, then reduce the layer of cotton wool and gauze. We check if there is cotton wool and gauze in the glass. Add if it’s not enough until it’s full. We dampen the mid-frequency speakers. To do this, we additionally cover their diffuser holders with foam rings made from 10x27x355 mm blanks. the ends of which are glued end-to-end with Moment glue. We cover the bottom and ceiling of the column from the inside with felt (batting, padding polyester, etc.). We wrap the wires with a bandage. We place the bandage along the wire and twist it, wrapping it around the wire. It is convenient to secure the bandage with threads. Assembling the column. We coat all the perimeters of all speakers with plasticine. There is no need to wear protective nets, but only on the condition that there are no small children, the wife will not come in with a mop or vacuum cleaner, and that the speakers will not be transported. Turn on the speakers. We don't know right. We call our friends. Please bring your favorite recordings. Let's listen. We calm our friends down with beer. We note with mockery how useful the bucks spent on purchasing foreign rubbish would be for them.
The second way. Medium difficulty
We do everything indicated in path 1, but do not collect the columns.
1. Let’s improve the properties of the body and eliminate overtones and “barrel”
2. Let's achieve better signal transmission
3. ?
So, let's go. Strengthen the rear wall of the case by placing two slats with a cross-section of 3x2 cm vertically along the entire length at a distance of 15 - 20 cm from each other symmetrically, and attaching them with screws to the rear wall. Pre-treat the mounting area with epoxy. It is necessary to take into account the possibility of installing a phase reflex later. Between the rear and front walls we install a spacer rail at the level of the midrange head, taking into account the possibility of installing a glass. We coat all wall joints and corners from the inside with silicone glue such as "Bison" or plumbing silicone putty. We cover the entire body inside with felt (batting, padding polyester, etc.). It should not be thicker than 1.5 cm, so as not to greatly reduce the internal volume of the case. We reject all proposals to replace 15 GD-11A with 6 GDSH-5. Ours is already “cool”, and such a replacement will lead to a loss of power, a decrease dynamic range(very dangerous) and you will have to change the filter a lot. So, when replacing 15 GD - 11A with 6 GDSh-5 for 35AS - 212, you will have to replace the following parts: L1 - 0.22mH, C2 - 1.0mF, C8 - 0.5mF, L4 - 0.1mH. New parameters have been specified. When using 6 GDSH - 5 - 4, you will also have to install an additional resistance in the circuit of this head at 4 Ohms. Also appearance columns changes. Well, if you really want to, then you can. Further. Removing tone switches. Remove unnecessary resistors R (1, 2, 4, 5, 7, 8, 9, 11, 12). We replace the wires on the filter mounting with a copper wire with a diameter of 1.2 mm. We replace the wires going from the speakers to the filter with more traveling ones. For the low-frequency speaker - multi-core - with a cross-section of 2.5 - 3 mm square, for the mid-frequency - 2.5 mm square. For high frequency - 2 mm square. - single-core. All wires are soldered to the filter directly, rather than passing through previous speakers. The filter is installed at the bottom of the column. All wires are laid under a layer of felt. On the side walls. The filter regulators are removed. In their place, we make wooden (chipboard, plywood) plugs according to the thickness of the body. We pour them onto the epoxy and sand them down. We cover the front panel with self-adhesive wood-look film to match the veneer of the speakers. Installing speakers. Low-frequency and mid-frequency through rubber gaskets. Suitable rubber from window insulation, thin rubber medical hoses, silicone hoses (worse). We treat the installed speakers around the perimeter with plasticine or non-hardening window putty (it resembles a bar of laundry soap and is cheap). Checking the sound. We're just fooling around. We push aside all sorts of “Pioner”, “Technics”, JAMO and ...
The third way. Super complex, time consuming and super efficient
It’s good to have the following devices: oscilloscope, generator audio frequencies, digital multimeter, LC meter. A person who does not do repairs and assembly at home, of course, doesn’t have all this, but there is a way out - go to the workshop and ask to try on what you need, taking filters, heads, etc. with you. If they ask for payment for this, it will be purely symbolic. You can even order a filter. It will, of course, be more expensive.
Begin. We take as a basis 35AC -212 with dimensions 710x360x285. It is desirable that the case be made of plywood, a woofer with a rubber surround, and a high-frequency speaker with a fiberglass dome. Let's sort everything out. We no longer need the midrange speaker. The housing needs to be increased to 100 liters for a woofer with a rubber surround. If the suspension is polyurethane foam, then up to 120 - 130 liters. Our body is 70 liters. There are two options:
1. Remove the front wall from the case in order to later use it for a matrix for the holes for the speakers in the newly manufactured 100 liter case. The remains of the buildings make good boxes for potatoes and markoshka in the cellar.
2. You can try to build up the old body. In the first case, you need to focus on the dimensions - 1100x360x350 and production in a furniture workshop according to your drawings, with abuse and quibbles about quality. We will consider the second way.
So, you can try to get by with little blood. We make it ourselves, or we order two boxes with tightly fitting walls and lids made of double 10-layer plywood with external dimensions - 380x360x285. We cut out identical holes approximately 270x210 in the bottom of the column and in the lid of the box. We cover the inside of the box with felt. After assembly it will be impossible to do this. We drill holes in the lid of the box and in the bottom of the column through which we fasten them together with bolts. The bolt heads should sink into the countersunk area. Add a little bit of shot - 10 kilograms of shot won't hurt, throw a gauze bag with cotton wool on top. We pre-fill the joint with epoxy with a normal content of hardener. We cover the joint with felt. The rest of the body movements are the same as in paths 1 and 2. Let's take the mid-frequency head 30 GDS - 1. You just need to check them - there are a lot of defects. Purely mechanical properties. Further. We measure f resonance of all speakers. You can use a felt-tip pen to sign directly on the magnets so you don’t get confused and try everything on again. It would be good if the resonance frequency of paired speakers did not differ greatly. If the speaker makes extraneous sounds at any of the audio frequencies, then it must either be cleaned or replaced if cleaning did not achieve normal operation. We calculate and make filters for our case. The fewer inductances, the better. We continue to work with the body. Remove excess resin at the joint. Let's polish it. We make two wooden boxes for filters. We will mount them on the back wall from the outside. We solder the wires from the amplifier directly to the filters. And we will drag the wires to the speakers through the fastenings of the speaker connectors. All wires are branded audiophile ones. Choose your own price category. There’s just no point in taking very expensive ones. It is better to convert the bass reflex to a frequency of 31.5 - 40 Hz. If the dome of the high-frequency head is made of lavsan, then, after removing the crosspiece, you need to coat the suspension and the outer third of the dome with perchlorovinyl. We cover the entire body with self-adhesive film. For the rest, see path 1 and path 2. With obligatory step by step check- better - worse. The best method, if there is no obvious result, is blind listening.
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To participate in the voting, register and log in to the site with your username and password.Modification of 35AC-212 (S-90) with original speakers and switches.
According to the prospectus of the 90s, the Riga Radio Plant mass-produced two models of acoustic systems: 35AC-212 or “S-90” and 35AC-012 in the modifications “S-90B”, “S-90D”, “S-100B”. The time has come to modify the older model 35AC-212, as well as its predecessor 35AC-1, which have a similar set of speakers.
These models have switches for the level of attenuation of the energy supplied to the midrange and tweeters, allowing you to adjust them to the level of the woofer and adjust the system to specific listening conditions. All this is good, of course, but it “thumps and clicks” no matter how you turn the switches. I want it to be musical. Somehow I was talking about alternative thoughts about finalizing the S-90. These thoughts happily dissipated without being realized. They were replaced by others, more interesting ones. It seemed the most promising to use the “Nivaga 9” filter from the previous article and convert it to another set of speakers, and leave the midrange and high-frequency switches in their original factory form. The resulting filter diagram for the S-90 is shown in the figure. I propose to call it “Nivaga 10”.
Distinctive feature The filter is the presence of resistors R1, R2, R3, R4, which provide direct potential contact of all speakers with the output of the PA and do not allow the phase characteristic to deviate far from a linear dependence in frequency. If you look closely at the diagram, you will notice that the resistance of these resistors is close to the active resistance of the corresponding speakers. Meticulous comrades can of course add the inductive equivalent of these speakers. I was lazy, because even in this form the sound quality completely satisfied me, but I didn’t have the opportunity to experiment in a sound chamber. Well, if you look even more closely at the circuit of the bandpass filter leading to the midrange speaker, you can see that it was created from a previously developed filter like “Nivaga 6 or 8” by replacing the speakers with equivalent resistors. Similarly in the lowpass and highpass filters resistors R1 and R3 are equivalent to the corresponding speakers.Therefore, this circuit with parallel connection of speakers is a logical development of the previous one with serial connection speakers, which means it retains all its advantages, which were written about in earlier articles. And at the same time, it creates new opportunities to move the cutoff frequency of all four filters included in the circuit independently of each other, controlling the peaks and dips in the frequency response of the speaker, which was not the case in the previous circuit. In the specific case of this circuit, I sought to spread the cutoff frequencies of the bass and midrange speakers, as well as the cutoff frequencies of the midrange and tweeters, by half an octave. The results are brilliant. Elastic bass, stereo panorama, volume, clear mids - everything that a music lover's ear craves is present in the modified S-90 speakers.
The fear that the introduced resistors would heat up was not justified. Their power is theoretically based. In practice, it can be reduced by 2 - 3 times, but the resistors must be wirewound.
Practice shows that not everything that I like suits others. Well, the proposed scheme is open to reasonable modifications, and I am ready for serious discussions.
This treatise was compiled on February 20, 2012.
Here are located scheme,detailed description, options Acoustic speakers speakers Radiotehnika class S90 (S90, S90B, S90D, S90F)
High-quality acoustics from Soviet times, after minor modifications and restoration, we can confidently say that they will give a head start to many modern acoustic systems. If you have similar ones lying around or bought them somewhere cheap, then put them in order and they will delight you for a long time with powerful bass, rich mid and high frequencies in musical works of any style and direction.
S-90 first model
In the speaker system
S-90 There are two step playback level controls separately for mid and high frequencies in the ranges from 500 to 5000 Hz and from 5 to 20 kHz, respectively. Both regulators have three fixed positions: “0”, “-3dB” and “-6 dB”. In position "0", the signal from the crossover filter is supplied to the corresponding head directly. In the “-3 dB” and “-6 dB” positions, the signal is weakened relative to the “0” position by 1.4 and 2 times, respectively.
With the appropriate spectral composition of the program, switching the regulator changes the timbre coloring of the sound.
S-90
Nameplate power 90 W
Rated power 35 W
Nominal electrical resistance 4 ohm
Frequency range 31.5-20000 Hz
Nominal sound pressure 1.2 Pa
Overall dimensions of speakers 360x710x285 mm
Speaker weight no more than 30 kg
IN AC There is an indication of speaker head overload. Regulators located on the front panel AC, make it possible to smoothly adjust the sound pressure level of the high-frequency and mid-frequency loudspeaker heads in the range from 0 to minus 6 dB.
There is also a model of the speaker system" S-100D", it uses a mid-frequency head 30 GDS-3 with MAHID magnetic fluid, which allows you to increase the rated power of the speaker system to 100 W. The rest of the design" S-90D" And " S-100D" are similar.
To operate, the speakers must be connected to an amplifier that has the highest (maximum) power at the output of each channel, ranging from 50 to 150 W.
If the OVERLOAD indicators start to light up when the speaker is operating, then you should reduce the level of the input signal supplied to it (by using the volume control in the amplifier to which the speaker is connected).
Passport specifications S-90D
Nameplate electrical power " S-90D"/"S100-D" not less than 90 W 100 W
Rated electrical power 35 W
Nominal electrical resistance 8 ohms
The range of reproduced frequencies is no longer 25-25000 Hz
Characteristic sensitivity in the frequency range 100-8000 Hz, at a power of 1 W, not less than 89 dB
Overall dimensions of speakers 360x710x286 mm
Speaker weight no more than 23 kg
The figure below shows the principle scheme speakers S90D.
Schematic diagram of S90D
Speakers S90 diagram, description.
Reworking the S-90 filter
Having been an opponent of audiophilia as a simplification, after experiments I changed my point of view and now I’m even ready to sacrifice something for the sake of a small number of obstacles in the path of sound :). This is actually very important, even on the speakers discussed below. But this also forces you to sacrifice some things: high power and congestion of frequency bands.
I used the crossover below, broken down into pieces, for my s-90de with speakers: 30GD-2, 6GDSH-5-5, 3GD-2, where it plays simply wonderful with any genre of music. 3GD-2 (its worse analogue 6GDV-1-16) is a very old high-frequency speaker (my copy is from 1977) with a resonance frequency of as much as 4500 Hz (but there is an opinion that in this place it is quite calm), so the high frequency of the midrange section is HF is due precisely to this fact. However, most domestic tweeters have not gone far, so I consider this cut to be very good for them.
This filter will work great on good foreign mid-high-frequency speakers, which I tried myself :). But, of course, it needs to be changed taking into account everything new (including the frequency of the section) - taking the principle itself as a basis.
p.s. Still, we should not forget that everything in the world is not only relative, but also subjective :). Besides, I have this moment There are absolutely no means of measuring the frequency response of your system - everything is adjusted by ear in the same room...
speakers
NC: Let's look at the generally good bass driver used in the s-90. 30GD-2 (75GDN-1-4) with a nominal resistance Z=4Ohm, sensitivity S=86dB (or dB/W*m) and frequencies F=30-1000Hz does not provide the best IFC (impedance-frequency characteristic:)) in the compartment with poor sound at frequencies above 500Hz.
Our cutoff will be at 500Hz. Ideally, to make this speaker work really well, you would cut off everything above 200Hz. After all, the main drawback of the 30GD-2 is that at these frequencies it mumbles (“sound from under the diffuser hood”) and plays very poorly. But to make such a low crossover frequency you need an excellent midrange speaker with a resonance frequency of no more than 70Hz.
MF: The standard mid-range driver 15GD-11 (20GDS-4-8), with parameters Z=8Ohm, S=89dB, F=200-5000Hz, does not stand up to any criticism either in terms of sound or the characteristics we need. Therefore, it needs to be replaced with the nice baby 6GDSh-5-4 (Z=4Ohm, S=92dB, F=150-12000Hz) which looks completely frivolous, but in fact turns out to be very good. In addition, it has the sizes we need, price (no more than $4!) and availability in Russia.
It should be noted the low power of the 6GDSH-5 (as a result, the inability to work at discos/parties) and bursts in some parts of the frequency range (“loudness”).
There were opinions that the 6GDSH-5 has poor directivity at high frequencies, which is why the stereo panorama is “unstable” at a relatively high section. It seemed to me that this was not so, so if there are problems, act according to the circumstances :).
HF: Any tweeter with parameters S=89-92dB and Z=16Ohm will do. It is important to note F (actually, the minimum operating frequency of the speaker) - it should not be more than 4500Hz, and the lower the better.
Structural dimensions and fastenings are selected on site using available means.
sensitivity
MF: To cut off the extra 7 dB (92-85 = 6), I suggest using the option of one resistor, which will avoid unnecessary elements in the circuit and at the same time reduce the ratings of the filter elements due to an increase in the speaker resistance. Resistor R2=4.3Ohm will give us a reduction of 6dB. The sensitivity is reduced by a resistor in the approximate ratio of 1 dB/0.7 Ohm. Coil L1 has its own resistance of 0.75 Ohm and will help us remove another 1 dB. Voila! :)
However, the disadvantage here is that there are no exact formulas and dependencies, and the values I gave appeared as a result of my personal feelings.
VC: We use the same method, selecting the desired resistor until the desired result is achieved. However, in this circuit there are no filter elements with a high intrinsic resistance, so resistor R1 must be taken with a margin of 1 dB. We also note that the volume of the high-frequency speakers relative to others in the system strongly characterizes its “inclinations” - for example, most listeners like a slightly muffled high-frequency sound (by about 1-2 dB), the system seems to be “softer”. What is relevant for domestic high-frequency speakers is not the most best quality:)). For heavy music, emphasizing the high frequencies may be more important.
It's nice to know that changing the sensitivity resistors within one unit (1 Ohm) has virtually no effect on the filter itself and the cutoff frequencies, which makes it possible to experiment.
But you shouldn't cross the 0.7 Ohm difference when experimenting with R2 - the L1 coil is much more sensitive to this change.
inductors
The most difficult thing. We urgently need to find ways to measure inductance, otherwise precise tuning will not work.
In the absence of a way to measure, I suggest the following: compare the coils by their own resistance, taking into account all design parameters. Theoretically, if all the factors influencing the inductance rating coincide (there are some very interesting ones - the density of turns, the content of iron impurities in the frame :)), then you can obtain the necessary inductance, as if “following a model”.
Despite everything, this method, it must be said, is very inaccurate. There is no difference between the inductance L2, for example, 1.5 mH and 1.27 mH in terms of resistance.
LF: I’ll give you my parameters for a large coil (it also has “ears” on the sides): inner diameter of the ring: 35mm, outer: 70mm, coil height: 37mm, width of the winding area (height without sides): 30mm, wire thickness (copper, enameled ): 1mm. With these parameters, the coil resistance DC(measured by digital tester): 0.8 Ohm.
If these parameters are observed, you should get an inductance in the region of 1.0-1.6 mH, congratulations :).
You can wind the coil the “old fashioned” way, knowing how many turns you need to make. This has recently become known: for 1.27 mH, 210 turns of “manual” (not very neat) winding are required. In this case, for every 0.05 mH there are approximately 5 turns.
SC: The small coils should all be the same in frame; I took the one with the smallest inductance. Inner ring diameter: 12mm, outer: 32mm, coil height: 23mm, winding area width (height without edges): 18mm, wire thickness (copper, enameled): 0.5mm. Resistance: 0.7 Ohm, inductance 0.18-0.21 mH.
At 0.18 mH the number of turns is 127 pieces. At 0.21 mH - 136.
By the way, do not repeat the mistakes of the USSR assemblers, do not fasten small coils with screws inside - the inductance will change and nonlinearity will be added; attach with glue.
For those who measure themselves: it is useless to try to rewind a small coil with a thick wire from a large one, and you probably want to do this :). Even having completely wound the entire frame, I did not get an inductance of more than 0.1 mH.
At the same time, if you build a new optimal frame (see links, “Cec”), which is not as simple as it seems, then the coil’s own resistance will allow you to gain 1 dB to the speaker sensitivity - you will need to slightly calibrate the sensitivity resistors in front of the speakers.
If you try to find the same large frames somewhere else and wind the L1 coils with thick wire, then their resistance will be approximately 0.4 Ohm - also better.
p.s. I kindly ask you not to write me letters asking for help in calculating inductance on other frames and other values using this method. Assemble the “box” (see links), it is very easy and will solve all your problems with precise winding of coils.
capacitors
Everything is extremely simple. You need to find the same values for decent quality capacitors, you can read about the types here, and about resistors there, by the way. Capacitors can be combined (summed) in parallel (as well as reduced according to the resistance rule by connecting in series). If you have disassembled the s-90 filters, then you should already have a good set of necessary containers :).
Among the domestic ones, instead of the film K73-xx that you probably came across, I recommend trying the metal-paper MBxx - a “softer” sound. If funds and accessibility are available, foreign MKPs are preferable (1uF ~ $1.1, domestic analogue- k78).
The capacitors, of course, are non-polar and for a voltage of at least 40V. The quality of the elements in Zobel circuits is just as important.
Here you can experiment with changing the “color” of the system that the capacitors give. I recommend trying to bypass all capacitors (except those in the Zobel circuit) with small (around 0.1 µF) capacitors of other, usually higher quality, types. For example, polystyrene (k71-7) or mica (SGM) - the result is more detailed sound at mid-high frequencies and increases the transparency of the system. In addition, metal-paper (MBxx) capacitors give a slightly “muddy” sound. To bypass means to combine together in parallel :).
resistors
With a power of at least 2W, with less, overheating and a change in rating are possible. Among the domestic ones, MLT-2 can be used. PEV-10 from the s-90 kit are not the best, but they will reluctantly go... I recommend Chinese ceramics - they look like white teeth, they are large, they are inexpensively sold everywhere in radio stores (power up to 15 W), but the range of ratings is fully present.
In other matters, low-power MLT resistors also work well at non-disco power levels, at least in place of R1.
Please note that the value written on the resistor is not necessarily the same as what it actually is. I strongly recommend selecting resistors by measuring them with an ohmmeter/tester. The diagram shows clearly measured resistors.
When finalizing the speakers, it is highly recommended to place resistors R1 and R2 as close to the speakers as possible - directly on the terminals. This will greatly reduce the influence of the cable (which is after these resistors, but not before them) on the sound.
Zobel chains
The reason is that the impedance of the speaker is not constant and increases as the frequency response decreases. This effect occurs in all dynamic type heads without exception, regardless of the country and year of production. More precisely, the Zobel circuit (in my filter only a simplified version of it is used; full ones allow you to adjust the impedance at low frequencies, which is not always necessary) is necessary for the normal operation of the filter inductors, with a sufficiently large self-inductance of the speaker coil. Without a Zobel circuit, the operation of the inductor as a low-pass filter is grossly disrupted and filtering is practically not carried out at all (!).
LF: Elements R4 and C4. It is advisable to set C3 to more than 60 µF, but even this is sufficient for a crossover frequency of 500 Hz. R4 is equal to 4.3 Ohm.
Compare the ICHH of 30GD-2 without and with Zobel. The graphs are approximate, but there you can see the tuning frequency of the s-90 bass reflex - the second huge rock on the left, before 100Hz :).
SC: ICHH 6gdsh-5. You can try smoothing above 3 kHz with Zobel R3, C3. For this, 10-20 µF and an 8.0 Ohm resistor are enough.
Important: a Zobel circuit on the midrange is required for the normal operation of this crossover. Without it, the “new lightweight filter” showed its complete inconsistency in the midrange and high frequencies.
HF: Due to the low inductance of the speaker's own coil and the cutoff at low frequencies, the circuit is irrelevant.
filter
In all frequency sections, a passive all-pass filter of the first order is used with an attenuation of 6 dB per octave (frequency change by a factor of two), Butterworth approximation. Actually, the filter itself was calculated by the JBL Speaker Shop program and slightly adjusted manually :)).
LF: Low pass filter. As you can already understand, the cutoff frequency is 500 Hz (for 30GD-2/75GDN-1-4, lower is desirable, but was chosen as a compromise to 6GDSH-5). Provided by element L2, speaker load, coupled with a simplified Zobel correction circuit.
Midrange: Bandpass filter. The lower part (C2) is matched with the low-pass filter and is tuned to a cutoff frequency of 500 Hz based on considerations of the resonant frequency of the 6GDSh-5. The upper part (L1) is matched with the high-pass filter and is tuned to 7500Hz, which allows for a broadband speaker structure, coupled with Zobel.
Both parts are loaded at 8 ohms (4 ohms from 6GDSH-5-4 + 4 ohms from R2).
HF: High pass filter. The frequency is matched to the upper part of the midrange filter and operates at 7500Hz, which avoids problems associated with the high frequency of the main resonance of domestic high-frequency speakers. Load 21 Ohm (16 Ohm speaker + 5 Ohm from R1).
All speakers are switched on in phase, which has a lesser effect on the phase characteristics of the system.
scheme
Electrical circuit diagram. Click to enlarge :).
The arrow on the right shows the “sound input” from the amplifier. The dotted lines are bi-wiring (the low-pass and mid-high-frequency filter sections are connected to each other in parallel at the amplifier - plus the low-pass with the plus of the mid-range and high-frequency to the plus of the amplifier, the minuses are the same).
The gray numbers in brackets above the filter elements indicate their load. The gray numbers with an "r" in front of them are the element's own resistance. Gray marks -1dB - loss of speaker sensitivity on the elements.
Next to the speakers, their important characteristics are briefly written out; below are the frequencies at which the bands/links intersect.
Inductance in mH, capacitance in µF, resistance in Ohm. After assembling the filter, the nominal speaker impedance for the amplifier remains equal to 4 Ohms.
A version of the “new lightweight” filter for s-90 clones, more precisely for Orbit 35AC-016. Speakers: 10gdv-2-16, 6gdsh-5-4, 75gdn-1-4 - a fairly common set.
Manufacturer: Riga Radio Plant named after. A. S. Popova.
Purpose: Acustic systems designed for high-quality sound reproduction as part of household electronic equipment.
Specifications:
3-way floorstanding speaker with bass reflex
Frequency range: 25 – 25000 Hz
Frequency response unevenness in the range 100-8000 Hz: ±4 dB
Sensitivity in the range 100-8000 Hz: 89 dB
Resistance: 8 ohms
Minimum impedance value: 7.6 ohms
Rated power: 35W
Maximum (nameplate) power: 90 W
Short-term power: 600 W
Installed speakers:
Dimensions (HxWxD): 710x360x285 mm
Description:
The acoustic system is similar except for the midrange speaker; the S-100F is installed with MAXID magnetic fluid. The speakers have two smooth playback level controls for midrange and treble. Adjustment limits are from 0 to -6 dB in the ranges of 500-5000 Hz and 5000-20000 Hz. In the “-6 dB” position the signal is weakened by 2 times. The speakers have LED indication of speaker overloads.
The body is made in the form of a rectangular non-separable box made of chipboard, veneered with valuable wood veneer. The wall thickness is 16 mm, the front panel is plywood 22 mm thick. At the joints of the housing walls, elements are installed on the inside that increase the strength and rigidity of the housing.
The heads are each framed with decorative black plates with four mounting holes. The midrange head is isolated on the inside from the total volume of the housing by a special plastic casing in the shape of a truncated cone. The LF head is located on the front panel along a vertical axis, and the MF and HF heads are shifted relative to this axis to the left. In the upper corner of the front panel there are overload indicators, and in the lower part there is a rectangular bass reflex hole, measuring 108x35 mm and tuning frequency 25 Hz. The nameplate on the midrange and treble regulators shows the frequency response curve and the manufacturer's logo. In addition, the front panel has bushings for attaching a decorative frame with fabric. On the rear wall, in the lower part, a block with terminals and a nameplate are attached. The set includes grills with acoustically transparent fabric.
The internal volume of the speaker is 45 liters. To reduce the influence on the frequency response of sound pressure and the sound quality of the speaker resonances of the internal volume of the housing, it is filled with a sound absorber, which is mats of technical wool, covered with gauze.
Inside the case, on one board, there are electrical filters that ensure separation of the speaker bands. The frequency section between LF/MF is 750±50 Hz, between MF/HF - 5000±500 Hz. The design of the filters and the overload indication unit uses resistors such as BC, MLT, SP3-38B, S5-35I, PPB, capacitors such as MBGO-2, K50-12, K75-11 and inductors on plastic cast frames.
