Many music lovers are familiar with the situation: a loudspeaker installed in one of the speaker systems suddenly begins to “wheeze.” Visual inspection does not give anything, when you “ring” the tester shows what is indicated on the label, but the sound is annoying, sometimes driving you crazy. This malfunction is especially typical for those with a large stroke. What's the matter?
A regular radio repair shop will advise you to simply replace the loudspeaker with a new one. This is a solution to the problem. It is simple but expensive. You can buy a good powerful head, and even a branded one, but it costs a lot. It will always be done. In the meantime, you can try to repair the speaker yourself.
As a rule, wheezing that occurs when playing the bass spectrum of sound frequencies is caused by short-term disruptions in the contacts connecting the coil to the speaker cable. In the place where thin, literally hair-like wires glued to the surface of the diffuser are connected to thicker elastic cables leading to the block, metal tin fatigue gradually accumulates during sound reproduction.
Repairing a subwoofer speaker, which most often suffers from this disease, is simple, but requires care. Usually the joint is filled with a drop of compound, so you need to pick it out very carefully, preheating it with a soldering iron. Once the connection is exposed, the contact should be soldered very carefully and quickly. After checking, if everything is in order, the repair area should be re-filled with an insulating compound, nail polish or viscous glue.
Speaker repair may also be necessary in cases where vintage or antique radio equipment over half a century old is being restored. For example, someone got an old American tube receiver from the post-war years. The condition is quite working, but the diffuser is badly damaged. You can, of course, simply replace the loudspeaker with a similar modern one. But you want to achieve “that” sound, to feel the time. In general, there is a desire to preserve as many of the original elements of the circuit as possible.
Repairing a speaker with a broken or torn cone is carried out using the gluing method. The best material, which serves to apply such a “plaster”, is Scissors should cut the patch so that it matches the shape of the missing fragment with an overlap of half a centimeter. Since rigidity is good quality diffuser, then it is best to glue the restorative part to it with acrylic nail polish. Where its edge adjoins the ring holder, rigidity, on the contrary, is inappropriate, the movement should be as free as possible, therefore it is recommended to restore the semicircular edge with rubber glue, like “eighty-eighth”. We can assume that the speaker repair is complete; all that remains is to let the varnish and glue harden and polymerize.
A common malfunction of loudspeakers is the wear and failure of the corrugated ring suspension, usually made of porous rubber and holding the diffuser along the edge. Repairing the speaker in this case involves removing the old one and gluing a new elastic ring. Kits for this procedure are sold, but it should be borne in mind that only expensive loudspeakers deserve such painstaking work; you shouldn’t bother with cheap ones.
Probably every radio amateur, and not only radio amateurs, has burnt speakers at home. This can happen to anyone. Breakdown of output transistors, overload, or manufacturing defects and much more can lead to failure of the coil inside the speaker. I want to tell you about my case. Dynamic head 25GDN-3-4.
She left us, going into the world of spirits, while listening to hard rock :) She left beautifully. At first she began to wheeze heavily, and then thick and stinking smoke poured out of her. The dust protection cap has melted. After disassembly, it turned out that half the coil had also burned out.
It is not difficult to rewind it, but the work requires patience. I only managed to wind the reel the second time. So, let's start repairing the speaker.
Stage 1 - collection of information. In reference books or on the Internet. You need to find data about the speaker itself, and especially about the coil. It will have to be made from scratch. Dynamic head specifications:
— Effective operating frequency range — 50 — 5000 Hz
— Level of characteristic sensitivity — 84 dB/W*m
— Frequency response unevenness — 14 dB
— Total harmonic distortion — 3 — 6%
— Nominal electrical resistance— 4 Ohm
— Maximum noise (nameplate) power — 25 W
— Limit long-term power — 30 W
— Maximum short-term power — 70 W
— Main resonance frequency — 55 ±10 Hz
— Equivalent volume — 8 Vas Liter
— Total quality factor — 0.5 ±0.5 Qts
— Diffuser diameter — 110 mm
— Magnet dimensions — d110x16 mm
- Are common dimensions— d125x79 mm (my measurements — d125x73 mm)
— Weight — 2000 g
— OST 4.383001-85
And the speaker coil data:
— Wire brand — PETV-1
— Wire diameter — 0.224 mm
— Number of winding layers — 2
— Number of turns in the 1st layer — 47
— Number of turns in the 2nd layer — 46
— Ohmic resistance — 3.1 ±0.4 Ohm
— Voice coil height — 22.5 mm
— Internal diameter — 25.4 mm
— External diameter, including winding — 26.6 mm
There is information. We select the required wire diameter and move on to the second stage.
Stage 2 – disassembling the speaker. We unsolder the multi-core wires going from the coil to the speaker terminals. For disassembly we need a solvent, a brush and plastic bag. Solvent for paints. It said 647 on the can. I bought it at a store that sells auto enamels. We need to use it to dissolve the glue that glues the speaker together. To do this, use a brush dipped in solvent to coat the edges of the speaker. And also at the bottom there is a linen centering washer, also along the edges where it is glued. The dust cap also needs to be peeled off. But I didn’t keep it. After impregnation, put the speaker in a plastic bag and tie it. This is so that the solvent does not evaporate so quickly. We wait about ten minutes. Let's take it out and look. The glue should have dissolved. The diffuser can be removed from above by hand, and the membrane from below must be pryed off with a knife or scalpel. If it lags behind heavily, then we repeat the procedure with the solvent and the bag. All work with solvent and glue must be carried out outdoors. I did it on the balcony. I hope everything worked out.
Stage 3 – winding a new coil. For this we need thin and thick paper. As you can see, the height of the coil is 22.5 mm. I cut a strip 300mm long and 22.5mm high. I selected a tube of the required diameter. The diameter can be adjusted by wrapping several turns of electrical tape around it. I measured it with a caliper. I wrapped the paper around the tube, coating each turn with glue or varnish. I used glue brand 505. It dries quickly and then becomes hard. It seems to withstand the temperature. Having removed the learned ring from the tube, we measure how it fits into the speaker core. It should go in and out easily with a small gap. If everything is fine, then we put it on the tube again and start winding the wire. Winding in two layers. The first layer is 47, and the second is 46 turns. Lay the coils one to one. The first turn must be secured with glue or varnish. After winding the first layer, soak it with glue. Next is the second layer, and again with glue. After drying, remove the coil from the tube and measure how it fits into the core. It should go in and out easily. If it rubs somewhere, or doesn’t fit at all, we redo it again.
Stage 4 – assembly. We glue the wound coil to the diffuser. You need to try as smoothly as possible. This time you need to use glue that can be dissolved. Suddenly it will need to be disassembled again. To do this, I bought glue for gluing rubber. We solder the coil wiring to the multi-core wires on the diffuser.
The coil with the speaker core needs to be centered using a piece of photographic film or thin plastic. Let's connect. We smooth the linen membrane with a knife or some flat object. To securely fasten the diffuser to the frame, we screw the speaker to a flat surface with self-tapping screws.
We solder the stranded wire to the speaker terminals and wait several hours.
Stage 5 – speaker tests. Unscrew it from the board. We take out the film from the core. By pressing the diffuser with your fingers, we listen to see if there is any friction in the coil. If it jams, then return to step 2. Check the coil resistance with an ohmmeter. Everything is okay? Then we connect it to the amplifier and listen. A properly assembled speaker will sound like new. If there is a slight friction between the spool paper and the core, it should go away over time. In case of friction of the coil wire with the outer iron washer - definitely stage 2. If the tests went well, then glue the dust cap. In my version, I peeled it off with a solvent from another speaker.
As you can see, there is nothing complicated. I think that it would not be advisable to rewind low-power small speakers. But it depends on your desire. Perhaps something can be simplified or done better. Happy rewinding everyone. The speaker was repaired - Boozer.
Acoustic systems are divided into active and passive; the difference is limited by the presence of sound processing chips inside, powered by electric current. Amplifiers, filters, interfaces for reading flash media, decoding compressed audio formats. In the latter case, the speaker system has similar functionality to a player. Let's look at what to do when the speakers don't work. Speakers include a myriad of sound reproduction devices; readers are interested in how to repair speaker systems with your own hands. You will need special glue. When the USSR was in use, BF 4, AK 20. Solvents were selected accordingly (based on the glue). You will need to disassemble, dismantle the connection, and repair the speaker system yourself.
The structure of a typical acoustic speaker
A moving part with a rigid plate creates air vibrations that are perceived by the human ear.
Classification of acoustic speakers
Repairing speaker systems with your own hands, if you doubt how the device works, relies on the principle of doing no harm. Regardless of speaker size speaker system formed by electrical and mechanical parts. The first is formed mainly by inductors. The second includes permanent magnet, membrane. Here is an incomplete classification of speakers for acoustic systems.
- Electrodynamic playback devices form three classes, united by the concept of the presence of a magnet and a moving membrane:
- Reel machines are built according to a principle known to the owners (repairers) geysers. When the inductor voltage is applied, the magnetic ring causes the membrane to move according to the law of the applied audio frequency current.
- In the tape role variable magnet performs a narrow corrugation. No coil, of course, inside. Speaker applications require matching transformers. A sign identifying the type of speaker of the speaker system.
- Isodynamic loudspeakers include a square, round spiral that moves parallel to the membrane in the field of a permanent magnet.
- Electrostatic playback devices have no moving parts. The membrane vibrates without making translational movements. The speakers reproduce high frequencies perfectly due to their low inertia.
- Piezoceramic speakers exploit the effect of converting electricity into vibrations of a quartz crystal. It is clear that you will not achieve high power from the device; the speaker is suitable for reproducing high frequencies of acoustic systems. Main advantage technical solution in low energy consumption.
- Ion speakers are practically rare; the theory was developed in the 50s. The operating principle is based on the modulation of gas ions sound vibrations. It is necessary to obtain an electric arc. Ideas have been put forward to use flames formed by positive and negative particles (air ions).
Readers are familiar with naturally occurring sound-reproducing devices. There is not always an inductor in the dynamics of an acoustic system. Therefore, before repairing, in the process, the technician carries out the correct classification of the devices by properly carrying out the necessary operations.
The device of the speakers of the acoustic system
Partially touched the device. Let's take a closer look at electrodynamic models. The diffuser forms the support of the cap. It is represented by something like a wide horn onto which a coil is glued on the reverse side. Flexible copper conductors carrying electricity, breaking through the diffuser from the inside. The soldering points are visible from the front of the speaker. The coil is light, it is required to ensure a relatively low inertia of the system. Even the tuning fork A of the first octave lies at a frequency of 440 Hz. It is clear that for fluctuations of the specified speed, the moving part of the acoustic speaker must be light.
The magnet is mounted motionless on the frame. Usually circular. An inductor runs in the hole in both directions, moving the cap-membrane assembly. The connecting wires perform constant oscillations. To position the moving part along the vertical and horizontal axis, a centering washer is used. A perforated piece of elastic material that centers the location of the cap, diffuser. The centering washer does not interfere with the displacement of the moving part along the axis of symmetry. The repair is ridiculously simple:
Since the membrane and cap do not break, the matter is to check electrical installation, places where wires are soldered, integrity of the coil.
The inductance is wound in the same way as the old one. Each layer of turns is coated with BF 4 glue. Poor-quality soldering is done again. Select the appropriate winding method and inductance. Usually done special device, formed by two pairs of posts standing opposite each other on a long board. Both are connected by axes. One contains the core of the new coil, the other contains the purchased wire. It is recommended to buy wire with varnish insulation. It is necessary to maintain the correct thickness. You can measure using a caliper.
Winding is carried out relatively quickly while the glue dries. The coils fit tightly one to the other, following the shuttle principle. It is important to maintain the correct number of revolutions and properly position the terminals.
Often you have to disassemble the speaker of an acoustic system for repairs. Stock up on solvent. The glued joints are wetted and a fixed time is waited. Please note: the joints are carefully cleaned. This is done regardless of the glue used to assemble the speaker of the speaker system.
Speaker range
Speakers for acoustic systems different types, each has a limited range of reproduced frequencies. Each one works as a kind of mechanical filter. However, it happens that you need to shift the range... You can raise the resonance frequencies of the electrodynamic system by varnishing the centering washer. A 5–10% solution of TsAPON and cellulose in acetone are used. The varnish is applied with a soft brush in a circle. Avoid misaligning the moving part of the speaker system. By performing the operations sequentially, we will increase the resonance frequencies by 1.5–2 times, approximately one octave.
To reduce the range, you should stick weights on the moving part. The correct ring of cardboard is attached to the back of the diffuser. The symmetry of the arrangement of parts should be more accurately maintained. The sound pressure drops rapidly. The volume decreases, the range of high frequencies narrows. However, in the resonance region, the speaker of the speaker system will demonstrate good performance.
The range can be expanded in both directions (if there is no cap). In the center, from the front, above the inductor coil of the speaker of the acoustic system, a truncated cone is glued. The mass is made as small as possible. Thin, thick paper impregnated with TsAPON varnish will do. The upper platform is equal to the coil, the height is half the diffuser, the taper is 70 degrees. Due to the increase in mass of the moving part, the resonant frequency drops, but the upper end of the range rises, thanks to the rigid core, harder than the diffuser. As a result, the spectrum of reproduced sounds expands in both directions. The total increase will be one and a half to two octaves, the game is worth the candle. Take care to configure the electronic part correctly: if there are passive filters on capacitors and resistors, they will limit (cut off) the capabilities of the mechanics.
Craftsmen increase the sound pressure at the resonant frequency for an unshielded magnetic system. Try to find this or a similar ring installed. Then glue the second magnet to the opposite side of the standing one, the interaction of the fields will intensify, therefore, the strength of the sound will increase.
The design of the acoustic system is simple, but it can break, they said. We hope the renovation goes off without a hitch.
How to repair a speaker yourself? FAQ Part 1
This is the first part of the loudspeaker repair manual.
Here you will find information about the terminology used, speaker problems and the simple repair when only replacement of flexible leads is required. Other issues will be discussed in future articles.
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How does the dynamic head work?
The schematic drawing shows a cross-section of the speaker. This is roughly how low-frequency and mid-frequency loudspeaker heads are designed.
- Suspension (corrugated).
- Flexible output (pigtail).
- Bracket (secures the braid to the diffuser).
- Damper (protects the pigtail from breaking near the terminal).
- Hole in the housing for flexible output.
- Insulating strip (holds the terminal).
- Terminal.
- Solders connecting the flexible lead to the terminal and the coil lead.
- Coil output.
- Coil.
- Speaker housing (basket, frame).
- Diffuser (membrane, diaphragm).
- Dust cap (plug).
- Centering washer.
- Sleeve.
- Pole piece.
- Kern.
- Top flange.
- Magnet.
- Bottom flange.
The letters N and S indicate the North and South poles of the magnet. This is the usual arrangement of the poles, although the opposite occurs occasionally.
In the next picture conventional drawing HF dynamics sectional view.
- Coil output.
- Insulating gasket.
- Suspension (elastic extension of the dome).
- Diffuser dome structure(membrane, diaphragm).
The main difference between tweeters and midrange and bass drivers is the absence of a centering washer.
In addition, many HF heads use a dome-shaped diffuser, often called a membrane. The dome and surround of such speakers are a single unit, and the sleeve is attached to the dome.
Since the stroke of the tweeter cone is small, the coil leads often play the role of flexible leads.
What are the types of speaker malfunctions?
Speaker malfunctions occur due to improper use, improper assembly, or normal wear and tear.
Incorrect operation.
Most often, damage occurs due to excess power supplied to the speaker. One of the reasons for such errors may be confusion with the method for determining the power of the speaker and amplifier. This is due to the fact that the same numerical values of effective, root-mean-square (RMS), or as it is also called, sinusoidal power and amplitude or musical power create a current in the speaker coil that differs by a factor of two.
Another reason that causes speaker overload is the careless redistribution of power between the heads of multi-way speakers. Most often, tweeters - tweeters - suffer from this. The fact is that the power of tweeters in multi-band systems can be less than 10% of the total speaker power. And if the user, using an equalizer, supplies most of the amplifier's power to the tweeter, then the death of the latter can be instantaneous.
There are also mechanical damages to the dust cap, suspension and diffuser. Sometimes these damages lead to misalignment, which in turn leads to the destruction of the coil and sleeve.
Destruction of the sleeve and coil can also be caused by displacement of the core. In such cases, the sleeve along with the coil gets jammed in the magnetic gap. This usually occurs as a result of a loudspeaker or speaker being dropped.
Unskilled assembly.
Due to unskilled assembly, the sleeve, coil, suspension or centering washer may come off. Poor quality gluing can also cause extraneous sounds.
Improper fastening of flexible leads can significantly reduce their service life.
Normal wear and tear.
If the loudspeaker head is assembled well, the suspension and flexible leads suffer the most as a result of normal wear and tear. The diffuser can also collapse if its safety factor does not match the power of the speaker.
How to identify a faulty speaker element without disassembling?
All speaker malfunctions can be divided into “mechanical” and “electrical”. However, some electrical defects are very difficult to distinguish from mechanical defects by ear.
If no external changes, such as destruction of the corrugation or diffuser has not been detected, but extraneous sounds have appeared in the form of crackling or periodic loss of sound occurs, then the flexible leads should first be checked.
To do this, connect a dial ohmmeter to the speaker terminals and move the pigtails while the diffuser is stationary. If the ohmmeter needle moves, it means the flexible lead is damaged.
Other electrical defects include coil breakage and short-circuiting of part of the coil turns or the entire coil. These defects can also be detected using an ohmmeter.
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To do this, a master oscillator signal is supplied to the amplifier input.
A partially peeled off coil or part of the turns can be identified by smoothly changing the frequency of the generator or turning on the generator in the GKCh (Swinging Frequency Generator) mode.
When testing this speaker, the frequency range 20Hz...2kHz with a period of 3 seconds was used. In this speaker, apparently, a significant part of the coil has come unstuck, as overtones are heard over a wide frequency range. If a small fragment of the coil peels off from the sleeve, overtones can appear only at a certain frequency, and only when the damaged structural element enters resonance.
In some cases, to identify a malfunction, it is useful to use an infra-low frequency generator. This can help identify, for example, defects in the gluing of the rubber corrugation to the diffuser. The arrow shows the place where the oversound is formed.
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Rubbing the sleeve against the core or the coil against the inner surface of the upper flange can also be detected at a frequency of several hertz if you lightly press the corrugation waves with your fingers.
More serious damage to the speakers is even easier to detect.
So, for example, if something is heard when turning the speaker over, it means that part of the turns or the entire coil has fallen off the sleeve.
If the diffuser moves very poorly, then most likely the coil has fallen off and jammed the sleeve in the magnetic gap.
If the diffuser does not move at all, then the core may have moved and jammed the coil along with the sleeve.
Never attempt to disassemble such a speaker without first removing the sleeve, as this may also damage the cone.
How to replace speaker flex leads?
Use extreme caution when replacing flexible leads on an unassembled speaker, as a steel tool attracted by the magnetic system may damage the cone and dust cap.
If access to the flexible terminals (pigtails) of the speaker is free, then you can try to replace them without disassembling the speaker. But, in some cases, the speaker will still have to be disassembled. The picture shows a broken flexible lead.
Old flexible leads should be removed with the utmost care so as not to damage the diffuser or break the coil leads.
First, unbend the brass bracket that holds the flexible terminal, if there is one, of course.
Then the soldering area is heated with a soldering iron to separate both the flexible lead and the coil lead from the diffuser. Usually, after warming up, the glue softens and the leads can be removed.
How can I replace damaged flexible leads?
Of course, the simplest solution is to borrow flexible leads from another speaker of similar power or order from suppliers that sell spare parts for speakers. But, if this is not possible, or you want to save on spare parts, then you can make surrogate braids yourself.
The first and simpler option is to replace the failed pigtail with a piece of MGTF wire suitable section. I don’t know who first came up with this, but it was with these flexible terminals that the once popular 4A32 speakers went on sale.
Another option is to make braids from a Soviet-made flexible telephone cable. It can still be found among all the junk at flea markets.
I am familiar with two types of such cable. In one, each wire consists of seven cores, and in the other of fourteen. Each core is made by winding copper tape on a lavsan thread. In cross-section, the tape has the shape of a rectangle with dimensions of 0.03 x 0.3 mm.
0,03 * 0,3 * 14 = 0,126 (mm²)
As you can see, the cross-section is small, so for powerful speakers you can twist two or more stranded wires.
First, a section or sections of telephone cable are prepared using a soldering iron.
Insulation is removed in small areas, to avoid damage to the cores.
Then the veins of each stranded wire unwind and twist again into one wire.
And finally, the flexible lead is carefully glued twice with rubber or 88 glue with an interval of 20 minutes.
Before the first gluing, the twist must be free so that the glue penetrates between the cores. Immediately after the first gluing, the strands are twisted to the end. The second gluing finally fixes the cores relative to each other.
Thus, it is possible to make a flexible lead for a speaker of any power.
If there is no telephone or MGTF wire, then as a temporary measure you can use MGShV wire or even a braid from a shielded wire, but such pigtails do not last long, and they put a greater load on the diffuser due to less flexibility.
When installing a flexible output, you need to take into account that the most weak points of this unit are the places where the pigtail is attached to the diffuser and the terminal.
If the fastening brackets are damaged or lost, the braid is secured with two crossed stitches of thread. Then the attachment point is glued with glue with a large dry residue. Weathered BF-2/BF-4 will do.
To prevent premature fracture of the pigtail, the attachment points are covered with several layers of rubber or 88 glue with a transition to a flexible terminal.
The current state of the market with loudspeaker prices makes speaker repair virtually unnecessary, but if difficulties arise in purchasing a new speaker to replace a broken or damaged one, then it makes sense to try to restore the damaged loudspeaker with your own hands. I received several coaxial-type speaker systems from various cars. Unfortunately, 2/3 of the speakers produce a distorted signal during playback, and the rest simply do not work. Below we will present material only on the restoration of “littered” car speakers coaxial type for later use when constructing or installing in multi-way stationary speaker systems. Before starting work we will carry out diagnostics speaker state.
Diagnostics of the speaker condition
1. Check for debris. Coaxial-type speakers are not completely protected from foreign objects getting into the magnetic gap, this is especially dangerous for old cars with rust or cars that have been used body repair. Checking is simple - carefully with your fingers let's move diffuser into the magnetic system, if at the same time extraneous sounds are clearly heard: rustling, crackling, grinding, then this means that metal debris may have gotten into the magnetic gap.
2. Take a tester and check the coil resistance in ohmmeter mode. If there is resistance, then this is our case. If there is no resistance, then it makes sense to check the thick flexible copper conductors from the speaker terminals to the diffuser for breaks. If there is no break, then most likely there is a break in the speaker coil and this is the case self-repair not discussed in this article. Instructions for self-repair are given below.
We disassemble and clean the dynamic head with our own hands
1. Unsolder the flexible coil leads from the contact petals for connecting the speaker and the contact petals of the coaxial speaker.
2. Remove coaxial speakers. The manufacturer does not provide for repair of the speaker system and coaxial speakers are installed tightly. The column with reinforced high-frequency speakers was removed by drilling out an aluminum rivet. We work carefully, the main thing is not to tear or damage anything.
3. On speaker repair forums, methods for dismantling the diffuser and centering washer are given. I also followed this path. We carry out work on outdoors in the absence of open flame sources! After using 100 ml of acetone, it was impossible to peel off the diffuser and washer. The solvent quickly evaporated without softening the adhesive joint. In order to save time and solvent, a strand of cotton fabric was placed at the gluing site and moistened with acetone; if necessary, wetting continued as it evaporated until the glue softened. After softening, use a thin screwdriver to pry up the edge of the centering washer and lift it above the gluing area. The thin rubber diffuser corrugation must be handled more carefully and delicately so as not to damage the rubber.
4. Remove the diffuser. Damage to the insulation of the speaker coil is noticeable from debris that has gotten inside the magnetic system. It is useful to look at the degree of damage under a magnifying glass for the presence of short-circuited turns (scratches to a depth of more than 40% of the diameter of the coil wire); if there is a suspicion of short-circuited turns, then it is better to reject the speaker. Using a damp cloth, I cleaned the diffuser, centering washer and coil inside and out from dirt. Cleaning must be done carefully so as not to damage the coil.
Coil damage
5. The gap in the magnetic system is a sad sight. Strong magnet Firmly holds small metal debris and dust. Tried to clean mechanically, but the small size of the gap and its curvature did not allow the debris to be successfully removed. I decided to use a strong stream of air from air compressor – Failed to clear the gap! I had to use another remedy - use a stream of water high pressure from a car wash. The result is that I’m all wet, but the gap is 100% cleared, and at the same time the entire frame is shining like new. I tried to do this carefully, since the pressure of the water jet is very high and I admit that if you are particularly zealous, you can destroy the adhesive of the magnet of the speaker system. To prevent rust, you must immediately dry the frame and magnet. After drying, it is useful to check the cleanliness of the gap under a magnifying glass. And as experience has shown, it’s a good idea to seal the gap with tape to protect it from accidental metal debris.
Assembling the speaker
1. After cleaning and drying components dynamics we assemble the structure. It's important not to rush. The goal is to position the coil in the magnetic system exactly in the center and ensure there is clearance and does not touch the coil. From a strip of A4 office paper, 10cm wide and about 18cm long, we roll up a cylinder and insert it inside the diffuser coil. The cylinder should fit snugly against the spool and have no protrusions or bulges inside.
2. Let's try to insert such a structure into a magnetic system. Do not hurry! It's better to practice several times. The cylinder should descend to the entire depth of the magnetic gap and at the same time the coil should hardly move along the inserted cylinder. If the coil moves along the cylinder with great effort, then it is necessary to shorten the length of the paper strip, and if the coil moves freely, then it is necessary to increase the length of the paper strip.