Do-it-yourself bookshelf acoustics drawings. DIY acoustic design. Devices with closed housing

Do-it-yourself bookshelf acoustics

DIY or Do It Yourself

One day I decided to build myself high-quality acoustics for sound recording. small room, and also for use as near-field monitors when working with sound on a computer (hobby). The main requirement is adequate sound in relation to the source. It’s not so much that “the lows are wobbling” or that “the cymbals are ringing,” but rather an adequate natural sound. So, we collect high-quality “shelf holders”.

Number of lanes

In theory, the ideal system is single-band. But, like everything ideal, such a system does not exist in nature. Yes, there are very high-quality broadband speakers from the same "Visaton", but for some reason all well-known manufacturers make two-way bookshelf systems. And when it comes to the floor option, then 3 stripes are not uncommon. There wasn’t much of a question here – the classic two-band version: low-frequency and high-frequency.

Speaker selection

The main requirement for speakers is an optimal price/quality ratio. Those. it shouldn’t be “cheap” for 500 rubles, but also not a mind-blowing “high-end” for $1000. Besides, I was in no hurry. The idea of ​​assembling “shelf speakers” with my own hands came quite a long time ago, and I threw the bait in advance to my good friend, “sick” with sound, with whom we have been constantly and fruitfully communicating on this topic for a long time.

The first to appear was the HF - Vifa XT19SD-00/04 ring-rad. These are high-quality 4-ohm tweeters, quite popular among audiophiles. They were planned for one set, but for some reason they didn’t work out and ended up in my set.

LF arrived second. They turned out to be very decent midbass from the Soundstream Exact 5.3 kit. Here you can read a little about them. It so happened that the tweeters burned out during installation, and the lone woofers themselves turned out to be unnecessary. 4-ohm 5.5" midbass mounted in a cast aluminum basket were immediately purchased.

Now that you have the speakers, you can start creating acoustics.

Active / passive?

Each option has its pros and cons. Firstly, you need to take into account the compactness of the speakers themselves and the associated difficulties in layout in limited space. There is no point in installing it outside. Secondly, individual modules as independent components can be combined in the future, and it is also easier to repair if something happens. And thirdly, active speakers are quite expensive. Because if you make a decent amplifier (and sometimes there is one in each case), then it will turn out to be more expensive than the acoustics themselves. Besides, I already had an amplifier. But in any case, I am in favor of the scheme - passive acoustics + amplifier, it is more universal.

Calculation of housing dimensions

We have decided on the speakers, now we need to understand which housing is optimal for them. Dimensions are calculated based on the sound characteristics of the woofer. There are no recommendations on the manufacturer's website, because... The speaker was intended primarily for car audio. There is no point in keeping special equipment for these purposes unless it is your job. Therefore, a smart guy with a special stand comes to the rescue. As a result of laboratory tests, we obtain a calculated case size of 310 x 210 x 270 mm. During the measurement process, the bass reflex parameters were also calculated.

By the way, many manufacturers publish recommended housing sizes for speakers on their websites. When such information is available, it is logical to use it, but in this case I did not have such data, so I had to do laboratory research.

Housing material

In my opinion, the most optimal material for the body is MDF. It is acoustically neutral and also performs slightly better than chipboard. Plywood is also good, but quality plywood is not easy to find and is more expensive and difficult to process. 22mm MDF sheet was chosen as the source material for the body. In principle, standard 18-20mm is quite enough, but I decided to make a little extra. There is no such thing as too much rigidity.

Housing construction and design

One of the most important stages. Before going for MDF, I advise you to decide on the design so that you can immediately ask the seller to cut the sheet in parts, and at a normal point of sale there are always good machines with accurate and even cuts. It is difficult to obtain such a cut at home.

So, design. The speakers should look at least as good as “industrial” ones, so that there is no feeling of a club of crazy hands. We make not only high-quality, but also beautiful acoustics. In general, there are practically no beautiful, interesting and at the same time structurally simple acoustic systems. Beautiful acoustics are made by the Italian Sonus Faber, stunning in beauty - Magico Mini. But they are all made using precision machines, which, by definition, are not available at home. As an option, you can order the cases from a good “cabinet maker” with hands and CNC. Depending on where and what you order, such work will cost from 10,000 rubles. up to 30,000 rub. along with materials. If the specialist is good, then the speakers will look no worse, or even better, than store-bought ones. In this case, I decided that I would do everything completely myself. Therefore, we look at things realistically and make a design without any bevels, curly cuts, etc. Those. it will be a parallelepiped. The calculated dimensions give a fairly pleasant proportion, and proportion in the design is already half the battle.

What to design in? Although I am related to design by line of work, my knowledge of 3D packages is, to put it mildly, superficial. In this case, the program should be more engineering than rendering. Specialized "Kads" for this purpose are heavy and unnecessary. A solution was found quickly enough - frivolous SketchUp is more than suitable for this purpose. It is so simple and intuitive that I was completely mastered in about an hour. The main thing he can do is quickly create any shapes, set dimensions, use simple textures. I believe that such a program is ideal for “home” purposes. You can easily use it, for example, to design a kitchen or even a small house.

Here is the body design:

Based on the drawing, a diagram of cutting the sheet emerges:

In general, the options are not bad in appearance, but purely structurally they cause difficulties. As a result, it was decided to trim the side walls with ash veneer, and cover the remaining 4 walls around the circumference with leather, or rather with high-quality automotive leatherette. The arquebus is beautiful in itself, but the woofer has a structural overlay on the front side of the housing that will not look very nice. Therefore, it was decided to make an additional decorative overlay (ring) for it, which will press it to the body, and at the same time add beauty to the speaker itself. The construction and design have been decided.

Tools

Before moving on to the next stage, I’ll outline what basic tools are needed for the job:

Circular.

Jigsaw.

Sanding machine.

Straight arms.

Without this kit, it is better to order the cases from a good craftsman.

Sawing

So, we cut the budget MDF sheet. I have already written that it is better to saw on special machines - it is inexpensive, but the results are accurate. But because I decided to make the body myself inside and out, then for the purity of the experiment I sawed it myself with a manual circular saw, and small pieces with a jigsaw with a guide. As expected, the perfect cut did not work out. After the cut, pairs of walls (left-right, front-back, etc.) are installed in pairs, adjusted with a grinder and/or electric planer and checked for perpendicularity with a square. And later during assembly they are finally adjusted after gluing. A loss of 2-3 mm is insignificant. But I still recommend sawing right away “at the base”, you will save a lot of time.

Housing assembly

The walls are glued together with PVA and tightened with screws. First we glue the body without the front wall.

Now there is a hole for the terminal block, as well as a chamfer in order to “sink” it. Initially, according to the design, the terminal block was supposed to be placed at the bottom. But during the process, it became clear that mounting the crossover in the center through the hole for the woofer would not be very convenient, so I moved the hole for the terminal block higher, and the place for the crossover lower.

You can close the box.

Now one of the very important stages is cutting out the holes for the speakers on the front panel. I already said it's perfect acoustic system- it's single-lane. Why? Because sound propagates from one source to the listener without a time mismatch due to the (tiny) difference in distance that occurs when using a multi-band system. Therefore, it is best to place the speakers as far as possible closer friend to friend. This makes the sound image “dense.” We calculate the holes so that the distance between the edges of the speakers will be approximately 1 cm. The holes are cut with a jigsaw with a circular guide.

After the chamfers are removed, we attach the terminal block and speakers, and then drill holes for future self-tapping screws with a thin drill. Without them, firstly, the MDF itself may “spread open” when screwing in the screws, and secondly, during the final installation the speakers will be more difficult to position evenly. I thought for a very long time about how to position the speakers relative to each other, and came up with the following scheme:

Holes from screws on external surfaces must be sealed before final finishing. I used epoxy. In order not to wait for one surface to harden, I sealed each surface with tape and moved on to the next one. When the epoxy had dried, I sanded it with a sander.

The veneer needs to be protected. I coated it with clear yacht varnish.

Now you need to cover the body with leatherette. There are many options for how to do this. I decided to do it as follows. A strip is cut 20 mm larger than the width of the case and slightly longer than the circumference of the case. On each side it is folded by 10 mm, the hem is glued with “special glue 88”. Then, using the same glue, the strip is glued around the circumference to the body. First the bottom (partially), then the back wall, then the top, then the front and the bottom again. At the last stage before gluing, the strip is cut in place and glued end-to-end. I glued all sides at once, i.e. didn't wait for each side to dry. After each side I took a short break (the glue sets quite quickly) and started on the next one.

If you really want to, then the phasic can be somehow refined.

Then holes are cut on the terminal block, “woofer” and “tweeter”. The skin on the terminal block and RF will be recessed downwards, so the diameter of the cutout can be left 5-10 mm smaller. The skin on the woofer will be pressed against the decorative ring, so you need to trim it so that it is not visible.

Final editing

First of all, we mount the crossover. The cross is home-made, based on a good element base. Air-core coils, tweeter film capacitors and MOX resistors are used. I didn’t solder it myself, but ordered it from smart guys.

Now we solder the required pair of wires to the terminal block and fix it on the body. The terminal block and speakers are screwed on with decorative black self-tapping screws with an asterisk head. The cover on the “squeaks” is screwed with similar screws, so it would be logical to use the same ones for the rest. The back wall is ready.

The midbass needs to be slipped under the skin, and pressed down on top with a decorative ring. Solder the remaining couple of wires and mount the speaker.

All? All. We screw the acoustic cable to the terminal block and begin testing.

Tests

The system was tested in the following configurations:

1. Receiver Sherwood VR-758R + acoustics.

2. Computer + Unicorn (USB-DAC) + Homemade stereo amplifier + acoustics.

3. Computer + E-mu 0204 (USB-DAC) + Sherwood VR-758R + acoustics.

A little about the configurations themselves. I personally think that at the moment the ideal option for a home music center is: computer + USB DAC + amplifier + acoustics. Digital sound without distortion is captured via USB and sent to a high-quality DAC, from which it is transmitted to a high-quality amplifier and then to the acoustics. In such a chain the amount of distortion is minimal. In addition, you can use completely different soundtracks: 44000/16, 48000/24, 96000/24, etc. Everything is limited by the capabilities of the driver and DAC. Receivers in this regard are a less flexible and obsolete option. The size of modern hard drives allows you to store almost your entire media library on them. And trends towards subscription to Internet content may eliminate this option, although this is not in the near future and is not suitable for everyone.

I will say right away that in all three configurations the acoustics sounded great. To be honest, I didn't even expect it. Here are some subjective aspects.

1. Adequate and natural sound. What is recorded is what is played back. There are no distortions in any direction. Just as I wanted.

2. Greater sensitivity to the source material. All recording flaws, if any, are clearly audible. High-quality mixed tracks are listened to perfectly.

3. Well-readable bass for such sizes. Of course, you can’t fully appreciate organ music on bookshelf speakers (it’s generally difficult to appreciate it on acoustics), but most of the material can be “digested” without problems. It's hard to expect more from such babies.

4. Very good attention to detail. You can hear every instrument. Even with a rich sound image and decent volume, the sound does not turn into a mess (the amplifier plays an important role here).

5. I would like to make it louder;) That is. The acoustics do not scream, but play smoothly. Although this is also not a small merit of the amplifier itself, because As the load increases, a good amplifier maintains linearity.

6. Long listening does not give you a headache. Personally, this often happens to me, but here it plays all day and nothing happens.

7. Concerns about incorrect panorama and strong dependence of the sound on the position of the listener were not confirmed. As far as I know, car acoustics have a specific sound phasing due to the location of the speakers in the cabin. Namely, I read about this set that its midbass is more universal in this regard. Which was actually confirmed. You can sit in the center in front of the speakers, or stand next to them sideways - the sound is excellent. There is a dependence, but it is very small.

As for the configurations themselves, the highest quality sound was achieved with the second configuration.

Firstly, a very high quality Unicorn DAC was used.

Secondly, the “home-made amplifier” is the know-how of one smart Tolyatti “sound specialist”. Here it is in a nice little aluminum case:

In a nutshell, we were able to find a circuit solution in which the amplifier retains its characteristics when the volume changes, i.e. does not distort the sound at any (constructively permissible) volume. Many amplifiers (even very expensive ones) suffer from this. It was amazing to hear how such an amplifier brought many speakers to life, i.e. made them sound the way they should sound. By the way, some industrial amplifiers (in particular, the Xindak, which is quite good in itself), were also rebuilt according to this scheme, and they got a “second wind”.

Have you compared acoustics with something else, you ask? Yes, for example, with ProAC Studio 110 – these are quite high-quality bookshelf acoustics, here’s a little about them. We compared them and realized that they definitely sound no worse. The “Proaks” may have a slightly lesser dependence of the sound on the position of the listener due to the specific placement of the inverter and the “tweeter”; somehow they cleverly calculated all this. As for the rest, it’s absolutely no worse, even I personally liked my homemade products better, but we’ll chalk this up to subjectivity;) I also put on headphones (quite good Koss) and compared them by panorama, highs and lows. Absolutely identical sound. Even at the bottom. In general, complete delight.

Costing by materials

Mid/bass speakers (pair): 3,000 rub.

HF speakers (pair): 3,000 rub.

Crossover (pair): 3,000 rub.

Sintepon: 160 rub.

Terminal (terminal block): 700 rub.

Screws: 80 rub.

MDF sheet, 22mm: RUR 2,750.

Scotch tape: 30 rub.

PVA: 120 rub.

Special glue 88: 120 rub.

Vibration isolation: 200 rub.

Figured ring-onlay: 500 rub.

Cable: 500r.

Total: 14,160 rub.

Some materials were or were received free of charge and accordingly are not taken into account here.

In custody

In any more or less complex device or complete functional system absolutely everything is important. When it comes to a music system, the final result is influenced by a large number of factors:

Soundtrack quality.

A device for playing a phonogram.

Digital-to-analog converter.

Signal amplifier.

Wires.

Speakers installed in the acoustic system housing.

Correctly designed for speakers and high-quality assembled housings.

Diagram and accessories for the crossover.

This is a basic but not complete list.

It is wrong to think that the main thing is the amplifier, or the main thing is the wires, or the main thing is the speakers. A home music system is like an orchestra. And if in this orchestra some people play poorly and others play brilliantly, then overall the result will be average. Or, as they said in a very precise example: if you mix a barrel of shit with a barrel of jam, you get two barrels of shit.

There is another extreme. A good system costs incredible amounts of money. This means that each component should cost half a million. And phonograms must be exclusively on Super Audio CDs or branded records. Like a closed society of elite audiophiles. This is all bullshit.

I came to the conclusion that it is quite possible to assemble your own relatively budget system, which can be described in one word “Sounds”. And if, due to its specific features, it is better to use real existing solutions as a DAC or amplifier, of which there are a lot now. Then a correctly made (either independently or to order) acoustic system will sound better than a “branded” one purchased for the same money. Nowadays almost all components can be ordered online. Moreover, many manufacturers publish enclosure diagrams for their respective speakers. There is a lot of software for calculating housing parameters. There are many specialized forums online, and offline there are people with hands. Of course, it is impossible to be an expert in everything. As in any field, the main thing is to know the general principles.

The article does not claim to be the ultimate truth, but I hope that my thoughts and my experience will be useful to someone else.
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Acoustic design does not mean decorating the speakers with carvings in an antique style, although this will give the speakers uniqueness, but solving the problems of acoustic short circuit.
The fact is that when the diffuser moves, excess air pressure is formed on one side, and the air is discharged on the other. For sound to occur, it is necessary that air vibrations propagate into space and reach the listener, and in this case, the air vibrates around the dynamic head basket and the sound it creates sound pressure not very large, especially in the low frequency region:

More details about the principle of operation of the dynamic head HERE.
Methods of breaking the acoustic circuit are called acoustic design, and each of them is designed to make it difficult for air to penetrate from one side of the diffuser to the other.
There are several main options for breaking an acoustic short circuit. The simplest one is to use sheet material in the middle of which a hole is cut for the dynamic head. This is called an acoustic screen:

A little more the hard way- open box, i.e. drawer without back wall:

Both of the above methods have too little efficiency, so they are practically not used only in cases where “there is no fish and no cancer.”
It is much more effective to use a closed box, and in such speakers special attention is paid to the tightness of the box - any gap in the box will produce overtones, since quite a lot of pressure arises in the box (when the diffuser goes inside the box) and a fairly large vacuum (when the diffuser moves out) :

The next option for acoustic design is a box with a bass reflex:

In this case, this is a rectangular hole located in a strictly calculated location on the front panel of the speaker system. However, this option can also be done using a pipe:

The advantages of these options include increased output at the frequency at which the bass reflex is designed, the main purpose of which is to invert, i.e. change the phase to the opposite. As a result, sound is emitted into space not only by the front part of the diffuser, but also by the rear part, the phase of which is changed by the bass reflex.
More difficult option acoustic design - acoustic labyrinth. The essence of this option is that the passages inside the speakers are located in such a way that resonance occurs at a certain frequency and, as a result, a large increase in output at this frequency. The calculations and manufacturing accuracy of such systems should be taken VERY seriously, since there is a high probability of “standing” waves occurring in the labyrinth. In this case, the sound quality will be even worse than that of the option with an acoustic screen:

The horn version allows you to get even greater output at the resonant frequency:

The difference between a horn speaker and a labyrinth speaker is that the direction of sound waves varies according to different laws - the horn either expands conically along its entire length, or exponentially. The labyrinth can have the same window along its entire length, it can expand or, on the contrary, narrow, but always linearly. In addition, for speakers with a labyrinth, both the front and rear parts of the diffuser take part in the work, while for horn speakers, both one and both sides can radiate.
The next acoustic design option is a bandpass or bandpass resonator:

This option differs from all previous ones primarily in that it emits only at the resonance frequency and requires strict adherence to the design dimensions.
The last three options are mainly designed for using a low-frequency dynamic head, while the previous ones are quite suitable for wideband speakers. Therefore, if the acoustic system has, in addition to woofers, others, for example, midrange and HF, then it is not recommended to embed them into the housing with the woofer.
In any case, to calculate the speaker sizes, you will need the characteristics of the dynamic head, in particular the Thiel-Small parameters. If this data is not available, it is necessary to obtain it before calculating the dimensions of the speaker housing. There are quite a lot of descriptions of methods for obtaining these parameters - just use any search engine.
Of course, these are not all types of acoustic design - these are the most popular.
The enclosure dimensions are calculated using special programs for calculating speaker enclosures. Finding them on the Internet, as well as instructions on how to use them, is also not problematic.
When designing speakers, you should take into account some technological features - if the front panel on which the speaker is installed is recessed into the housing, then you will need to make additional ribs into which the front panel will actually rest:

If you don’t want to mess around with the ribs, you can make the front panel so that it rests against the sides of the case, which also strengthens the connection between the front panel and the sides:

All this will give the front panel an additional, more rigid connection with the body.
You should also not forget about the methods of attaching the dynamic head to the front panel and the pitfalls that you may encounter. Mounting the speaker from the outside is most preferable, since it does not mechanically weaken the structure, but this method involves chamfering along the diameter of the dynamic head and sinking the speaker inside the body so that ALL emitters, bass, midrange, and treble are in the same line. chamfering reduces the mechanical strength of the front panel and its restoration will require an additional ring secured from the inside. The relevance of this ring is the higher, the greater the power expected to be obtained from the speaker being manufactured, and at powers above 150 W it is already 100% necessary:

If necessary, you will need to remove the side chamfers on the ring so that it does not interfere with the front panel installation into the case itself.
When installing the dynamic head, it is necessary to ensure that there are no gaps. If the chamfer is removed by a machine, the surface turns out to be relatively smooth; all that remains is to sand it. However, at home it is quite difficult to obtain a flat surface. It is not entirely clear what the manufacturers are doing here - it is strongly recommended to install the speaker from the outside, but the sealing rubber on almost all dynamic heads is located for installation from the inside:

To solve sealing problems, you can use door seals - self-adhesive strips of porous rubber, sold in all hardware stores. The sealant is glued along the perimeter of the chamfer and when installing the speaker, it completely fills all the cracks:

If the dynamic head is installed from the inside, then the hole will need to be chamfered to prevent the appearance of standing waves. However, such a chamfer weakens the rigidity at the point where the speaker is attached to the panel (the material is too thin) and this method of fastening is not acceptable for powers above 50 W without additional reinforcement of the structure:

It is advisable to use natural material for the manufacture of speaker cabinets, optimally plywood, but this material is too expensive. Therefore, it is better to use plywood to build speakers of medium and high price categories, using dynamic heads of VERY good quality and power above 100 W.
For the average price category and low powers (up to 50W), you can use fiberboard or MDF (the same as fiberboard, only the thickness and density is greater), but it must be processed and modified, or chipboard.

For powers up to 10 W, plastic is also quite suitable, but also using technological tricks.
The first problem when making speakers from plastic arises when eliminating the chatter of the plastic itself, especially manifested in the centers of the sidewalls. You can get rid of this unpleasant sound by using thicker plastic, or you can glue additional stiffeners. If the plastic is dissolved with dichloritane, then dichloritane with plastic chips dissolved in it can be used to attach the ribs. If the plastic is not dissolved by dichloroethane, then it is better to use epoxy glue, preferably made in Dzerzhinsk. Before gluing, carefully sand the contact areas with coarse sandpaper and do not be afraid that the glue forms beads at the point of contact of the parts to be glued:

For greater efficiency in suppressing overtones of the body, you can “paint” the resulting “baths” in 2-3 layers with anti-gravel - a coating used to cover the underbody of cars to protect against small gravel.

After drying, anti-gravel acquires the properties of rubber and absorbs sound quite well.
When using fiberboard as a material for the manufacture of speakers, it is necessary to determine the required thickness. If the speaker power does not exceed 5 W, then fiberboard can be used in one layer. Before cutting the fiberboard, it is coated on one side with epoxy glue and heated with a hairdryer. Under the influence of temperature, the glue becomes more liquid and impregnates the fiberboard to almost half the thickness. Once the glue has hardened, the resulting material is quite strong, essentially getinax, but on the one hand retains the sound-absorbing properties of fiberboard. You can cut DPV with a jigsaw, and you can glue the workpieces with epoxy glue reinforced with material. To do this, the blanks are folded into the desired structure and secured with any SUPERGLUE. Then strips of strong fabric are cut, in our case it is red silk. The width of the strips should be approximately 3...4 cm. The strips are laid at the joints of the workpieces, covered with epoxy on top, and then “ironed” with a 40...60 W soldering iron. High temperature allows the glue to completely saturate the fabric, and also significantly accelerates the polymerization of the glue. True, during operation a certain amount of smoke is released, so work must be done either outside or under a hood:

If the speaker power is higher than 10 W, but less than 20, then it is better to glue the fiberboard in half - first the sheets are glued together, and then the finished case is assembled:

For powers up to 30...35 W, you will need to fold the fiberboard in three or use 18 mm thick chipboard (unfortunately, 22 mm thick chipboard can only be found in old grannies in the form of old wardrobes made before the 80s). To stiffen the sidewalls, you can use spacers of the "CROSS" type:

For powers up to 50 W, the relevance of using fiberboard is already debatable - it is much easier to work with chipboard, MDF or plywood than to fold fiberboard from 4-5 layers. For this, material with a thickness of 18 mm is suitable, but you will have to use additional bars to ensure a greater connection between the speaker parts:

The speaker can be assembled using self-tapping screws, but since the power is not greater, it can be glued with epoxy glue or PVA, but it is better to buy it not at an office supply store, but at a hardware or construction store. This PVA will be called MOMENT-STOLYAR, water-dispersion glue. Buy on the market Recommended only in summer - after freezing the glue seriously loses its quality. However, to ease your conscience, it is better to screw at least a couple of screws into each block.
When manufacturing speakers, sometimes they make a serious mistake - the mid-HF link is not acoustically protected in any way from the impact of the back side of the woofer cone, which leads to a decrease in the efficiency of the speaker itself, and often the failure of the midrange link - too strong air impacts from the back side of the woofer diffuser lead to the midrange speaker coil being pushed out of the magnetic gap and the coil jamming.
Much more often they forget to subtract the volume of the protective casing of the midrange-high-frequency speakers from the total volume of the speaker; as a result, the internal volume of the speaker is less than necessary and the final characteristics are greatly blurred - the resonant frequency of the phase interferors increases noticeably, which results in unwanted overtones.
When assembling speakers with a power of up to 100 W, you can also use either chipboard or plywood 18 mm thick, although of course it is better to look for material 22 mm thick. To eliminate the occurrence of resonances in the sidewalls of the speaker body, additional support bars are also used through which parts of the speaker are attached. It would not be superfluous to install a “cross” and an additional washer for attaching the woofer dynamic head, as well as treating the speakers from the inside with sound-absorbing materials, for example, pasting with paralon or foam plastic 5-10 mm thick, just do not forget that the pasting will “eat” part of the internal volume and it is necessary to make an adjustment for it when calculating the dimensions of the body.

The best results are obtained with polyurethane foam, since the thickness of the applied layer can be adjusted by the speed at which the foam is released from the can. If the foam is released VERY slowly, then it turns out to be very dense and the increase in volume is not very large. If the foam is released VERY quickly, then it turns out to be much looser, and when it hardens, it greatly increases in volume. If foam is applied to the sides of the case from the front panel, increasing the foam output as it approaches the rear wall, and ensuring a minimum rate of foam output at the front panel, the internal volume of the speaker will take the shape of a pyramid lying on its side. Such tricks make it possible to completely solve the problems of standing waves, since there are no parallel planes inside the speakers, and the unevenness of the frozen foam only enhances the pyramid effect. When using this technology, you should be more careful when calculating the dimensions of the workpieces - the internal volume decreases VERY significantly and this requires a serious increase in the speaker body.

It is recommended to glue the ribs for fastening the sidewalls, in addition to the screed with self-tapping screws, as in the previous version, but there are several more options for adhesive masses:
- epoxy glue mixed with fine sawdust, or, better yet, wood dust;
- MOMENT-JOINER, but before screeding, the applied glue must be allowed to dry a little until the consistency is obtained butter room temperature. This will allow you to more completely fill with glue all the irregularities between the speaker parts;
- polyurethane glue, for example MOMENT-CRYSTAL, which also needs to be allowed to dry a little. After assembly, the gluing area must be thoroughly heated with a hairdryer, which will lead to the formation of small bubbles in the adhesive mass, and the mass itself will more tightly fill the unevenness between the contacting parts of the body;
- automotive sealant of domestic production, precisely domestic, since after hardening it is much tougher than imported sealants;
- mounting, polyurethane foam. Before applying it to the parts to be glued, the foam is “released” onto an unnecessary piece of plywood or fiberboard, and then thoroughly mixed with a metal spatula until it “shrinks,” i.e. until you obtain a mass similar in thickness to thick sour cream. After application and screeding, the foam will still expand slightly and completely fill all the irregularities at the point of contact between the speaker parts.
After gluing, the parts should be allowed to dry thoroughly for 20...26 hours.
To increase the volume at the same output power, you can use “double” dynamic heads - parallel or series connections of two identical speakers are used for the low-frequency section. In this case, the total area of ​​the diffusers increases, therefore the speaker can interact with a much larger amount of air, i.e. create greater sound pressure and this makes the subjective loudness much higher:

It should be noted here that the use of a large number of speakers, including for dividing the audio range, begins to introduce some troubles - it is quite difficult to achieve signal phasing in those places where the frequency response of speakers neighboring in the range intersects. Therefore, you should not chase a large number of bands for a homemade speaker - this mess can be very spoiled with such oil.
It is better to make speakers with a power from 100 to 300 W from plywood, and you will have to look for plywood with a thickness of 22 mm. The speaker is also assembled using stiffening bars that are glued. It is better to give the bars the shape of equilateral triangles, where the legs will be attached to the sides, and the hypotenuse will be directed inside the body.
If you cannot find plywood of this thickness, then you can use 8 mm thick plywood glued in three - the final thickness of the material is 24...25 mm. The adhesives are listed above.
As technological advice, we can only recommend first cutting the necessary blanks and only then gluing them, and immediately tightening them with self-tapping screws.
When installing a “cross” inside the AC, which would not be amiss, it is better to round the corners of the tie bars - quite large volumes of air are already moving and turbulence may occur around the right corners of the screeds. It is also recommended to “round” all internal corners using plasticine or applying several layers of thick anti-gravel.
Another type of acoustic design is separate housings for each speaker. These speakers do not use passive filters, and the signal is divided into ranges immediately after the amplifier's volume control. The split signal is then fed to three separate power amplifiers, which each drive their own speakers:

It would be unfair not to mention the “fillers” often used in speakers - small rollers of sound-absorbing material lying inside the speaker. Such rollers make it possible to slightly increase the calculated internal volume of the body, however, in order to correctly manufacture such a “filler” it is necessary to know its acoustic properties. It is quite problematic to obtain the characteristics of a “filler” in a home-made environment, so the only option is to either refuse to use the “filler” or empirically find out the required volume and the material used (usually fluff wool, batting, sentipon).
At powers above 100 W, it also becomes important to ensure the stability of the speaker cabinet, since quite a lot of work is already being done to move the diffuser and the air is actively “resisting”. It is also advisable to break the mechanical connection between the bottom of the speaker and the floor on which the speaker is installed. For these purposes, they usually use either tripods, which are problematic to make at home, or they use steel spikes screwed into the bottom of the speaker:

At powers above 200 W, it is desirable to strengthen the front panel of the speakers and it is desirable to use materials of different structures, for example, if the front panel is made of plywood, then with inside a sheet of chipboard is glued, the thickness of which is 1.5-2 times less than the thickness of the panel. This combination of materials ensures the absorption of vibrations in a larger audio range precisely due to the heterogeneity of the materials.
For greater stability of the speaker, its mass can be increased by coating the bottom with polyurethane polyurethane foam and lay a couple of bricks in it, covering them with the same foam on top. After the foam has hardened, it is better to cut off the irregularities with a stationery cutter. The “stolen” internal volume must be taken into account when calculating the size of the future speaker.
For powers above 200 W, it is better to use combination materials - all speaker parts are glued together from 18 mm chipboard and 18 mm plywood. Plywood is used as the outer layer and chipboard as the inner layer. This trick allows you to save a little - chipboard is much cheaper than plywood. It is advisable to glue inside the speaker sound-absorbing material, for example, triple-sewn batting, double-stitched with quadruple padding (the padding can be double and quadruple), 5...10 mm polystyrene foam. The different structure of tightly glued materials of different structures eliminates the problem of resonance of the body itself.
It is better to additionally tighten the corners with metal corners - this will add rigidity to the structure and protect the corners of the speakers from damage - the speakers are already quite heavy and during transportation various impacts are possible from which the corners most often suffer.

For powers closer to 1000 W, the thickness of the material should already be quite large, for example, two layers of 18 mm plywood plus a layer of 18 mm DPS for a total of 54 mm, and the DPS is glued between the layers of plywood, however, the speakers already move into the category “for sound”, therefore quality can be sacrificed in favor of mobility. Based on this, you can use double 18 mm plywood, installing a “cross” inside.
It is not difficult to notice that with increasing power, the thickness of the speaker walls increases. This is primarily due to the fact that it is necessary to isolate the air moving inside the speaker from the listener. However, we should not forget that the speaker cabinet can also resonate. It is to eliminate this nuisance that it is better to use internal pasting of the housings and minimize the overtones resulting from resonance. It is not difficult to check the resonant frequency of the housing yourself. To do this, you need to tilt the speaker 20...25 degrees and throw a rubber mallet on top of it, from which you first pull out the handle. The tilt of the AC is necessary so that the blow is single and the mallet bounces far to the side.
A microphone attached to the speaker (the membrane hole to the body) and connected to any linear amplifier on the oscilloscope screen will draw both the moment of impact and the aftersound that the body itself gives. The test is, of course, quite crude, since in reality the “shock wave” comes from the inside, and during the experiment from the outside, however, based on the results of this test, one can judge at what frequency the body itself resonates and how quickly attenuation occurs:

An ideal speaker does not cut and the moment of impact fades immediately, almost instantly, but the walls of an ideal speaker consist of concrete 1 cm thick for every watt of power and such a speaker is more suitable for ridicule than for use:

The finishing of the speakers can be very different, there are no strict requirements here. If the body is made of plywood and the pattern is quite attractive, then the body can be sanded and then coated several times with colorless varnish:

You can buy veneer valuable species trees and cover the AC with veneer to match the color of the furniture in the room:

Car audio stores sell so-called acoustic fabric, which is synthetic felt. The material adheres well and stretches, which will allow you to finish the speaker in a fairly high level:

Having sanded the body, you can paint it with car paint, just make allowance for the fact that car enamels dry when high temperature. Therefore, you will have to use a special hardener "IZUR", the mixing proportions are written on the packaging of the hardener, although it is better to add 10-15% more than the suggested proportion:

If the body is carefully sanded and sanded, then it can be covered with a self-adhesive film sold in BOI stores, but this material is quite delicate and should be used if you are sure that the speakers will stand in their place for ten years:

If you plan to frequently transport the speaker system, it will be very useful to provide appropriate handles. This is especially true for small speakers, which you want to take two at once, and for large ones, which simply have a lot of weight.

How to independently assemble an active speaker with increased efficiency at low frequencies is described.

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At first glance, making your own speakers is quite simple. However, this is misleading. First of all, it should be noted that the models are made with different elements. Depending on them, the device parameters and sound quality will be different.

There are special requirements for computer speakers. You can also make a model for your car or studio yourself. In this case, it is very important to follow the instructions. First of all, to assemble the speakers, you should consider the standard model diagram.

Speaker layout

The speaker circuit includes drivers, pads, diffuser and crossover. Powerful models use a special bass reflex. Amplifiers can be installed with field-effect or switching transistors. To improve sound quality, capacitors are used. The woofer is matched with the amplifier. The dynamic head must be attached to the seal.

Single speaker models

Single speaker speakers are very common. To assemble the model, you will first have to deal with the body. Plywood is often used for this purpose. At the end of the work it will have to be sheathed. However, first of all you should make side racks. For this purpose you will have to use a jigsaw. you can choose a small power.

The inside of the plywood is necessarily stitched with vibration-proof tape. After fixing the speaker, the seal is fixed. Glue is used for this purpose. Next, all that remains is to attach the diffuser. Some people make a separate shelf for it and fix it with stacking screws. To connect the speaker to the plug, a terminal block is installed. How to turn on speakers? For this purpose, a cable is used from the terminal block, which should lead to a power source.

Model drawing for two speakers

Speakers with two speakers can be made for home or car. If we consider the first option, then a pulse type diffuser will be required. First of all, durable plywood is selected for assembly. The next step is to cut out the bottom post. Models with legs are very rare. To cover the veneer, you can use regular varnish. There is no need to glue vibration isolation tape to the front pillar. The diffuser is mounted under the speaker. To make a hole in the panel, you need to use a jigsaw. The bass reflex is fixed at the rear wall. Some manufacture devices with horizontal speakers. In this case, the diffuser will be located at the top of the structure. Speaker wires are of the two-core type.

Devices with three speakers

Speakers (homemade) with three speakers are very rare. These devices are most suitable for the multi-channel type. To assemble the model, first of all, sheets of plywood are selected. Some also recommend using veneers. However, models made of natural wood are quite expensive on the market. The speakers should be installed horizontally. The device will also require an amplifier.

To fix it, use metal corners. To connect the plates you will need tightening screws. In some cases, the plates are secured with glue. Next, the model will have to be partially covered with leatherette. The next step is to install the terminal block. In order to fix it on the body, you will need to make a separate hole. It is also important to note with regulators. Microcircuits for them are used of the capacitor type. When the speakers produce noise, you need to change the diffuser.

Studio devices

Speaker drawings for studios assume the use of powerful speakers. The diffuser is most often used of the pulse type. Many experts recommend installing two amplifiers. For normal operation you will need a zener diode.

In order to assemble the speakers yourself, the housing is first made. Round holes are made on the front panel for the speakers. You will also need a separate output for the bass reflex. The design of the columns is quite different. Some people prefer to varnish the surface of the case. However, there are models covered in leather.

Models for computers

Speakers for computers are often made with one speaker. To assemble the model, veneer sheets of small thickness are selected. A hole for the speaker is cut out on the front panel. The bass reflex must be located at the rear of the housing. If we consider low-power models, the amplifier can be used without a resistor.

To adjust the speaker volume, special crossovers are used. These elements are allowed to be installed on a bass reflex. If we consider devices with a power of more than 100 W, then amplifiers can only be used with resistors. Some people select pulse diffusers for the model. At the end of the work, the terminal block is always installed.

Automotive modifications

Available with two or three speakers. To assemble the model yourself, you will need sheets of plywood. In some cases, varnished veneer is used. To fix the speaker, you need to make a hole in the panel. The next step is to install the bass reflex. Some modifications are made with low-frequency cores. If we consider speakers (homemade) of low power, then the bass reflex can be installed without an amplifier.

In this case, a multi-channel crossover is used to control sound. Some specialists install terminal blocks behind the bass reflex. If we consider speakers with a power of more than 50 W, then the microcircuits are used for two amplifiers. The diffuser is installed as a standard pulse type. Before fastening the case together, it is important to take care of the vibration-proofing layer. For the terminal block, you need to make a separate hole on the plate. Some people believe that the body must be cleaned. The wires for the speakers are of the two-wire type.

Open-back speakers

Portable speakers with an open case are quite easy to make. Most often they are made with one speaker. Holes are made on the back panel of the device with a drill. The plates are directly connected with tightening screws. The diffuser for such devices is suitable for pulse type. Bass reflex units are often installed with one amplifier. If we consider powerful portable speakers, they use a resistor crossover. It is attached to the bass reflex. Many experts recommend installing speakers on a seal.

Devices with closed housing

Speakers (homemade) with closed case are considered the most common. Many experts believe that they are the best in sound quality. Bass reflex devices for devices are suitable for the operational type. The woofers are installed in the holes. For the purpose of assembling the case, ordinary sheets of plywood are suitable. It is also important to note that there are modifications with cores. If we consider high-power speakers, the terminal blocks are installed in the lower part of the housing. The design of the models is quite different.

20 W models

Assembling 20V speakers is quite simple. First of all, experts recommend preparing six sheets of veneer. They should be varnished at the end of the work. It makes more sense to start assembly by installing the speakers. The bass reflex is used as a pulse type. In some cases it is installed on pads. Experts also recommend using rubber seals.

Power supply to the speakers is provided through the terminal block. It is attached to the back panel. The bass reflex can be installed either with or without an amplifier. If we consider the first option, then the cores are selected of the phase type. In this case, the woofer does not need to be used. If we consider speakers without an amplifier, then they use a crossover. At the end of the work, it is important to clean the body and varnish it.

50 W devices

Speakers (homemade) rated at 50 W are suitable for ordinary acoustic players. In this case, the body can be made from ordinary plywood. Many experts also recommend using natural wood veneer. However, it is important to note that he is afraid of high humidity.

After choosing the material, you should work on the speakers. They must be installed next to the bass reflex. In this case, you cannot do without an amplifier. Many experts recommend selecting only low-frequency crossovers. If we consider modifications with a regulator, then they use a pulse diffuser. The terminal block in this case is installed last. You can always use leatherette to decorate the speakers. A simpler option is to varnish the surface.

Speakers with a power of 100 W

100 W speakers are suitable for powerful ones. In this case, the bass reflex is taken only of the pulse type. It is also important to note that the amplifier is installed with a crossover. Many experts recommend using veneer to assemble the case. It is better to install the woofer on a pad.

Before a detailed consideration of the problem, we will outline the range of tasks; knowing the final goal, it will be easier to choose the right direction. Making speaker systems with your own hands is a rare occurrence. Practiced by professionals and novice musicians when store options not satisfied. The problem arises of integrating into furniture or high-quality listening to existing media. These are typical examples that can be solved using a set of generally accepted methods. We'll take a look at it. We do not recommend scrolling diagonally through the speaker system, delve into it!

Acoustic system design

There is no chance of making an acoustic system yourself without understanding the theory. Music lovers should know that biological species Homo Sapiens hears sound vibrations of frequencies 16-20000 Hz with the inner ear. When it comes to classical masterpieces, the variation is high. Bottom edge– 40 Hz, upper – 20,000 Hz (20 kHz). The physical meaning of this fact is that not all speakers are capable of reproducing the full spectrum at once. Relatively slow frequencies are better handled by massive subwoofers, and squeaking at the lower edge is reproduced by smaller speakers. Obviously, this means nothing to most people. And even if part of the signal disappears or is not reproduced, no one will notice it.

We believe that those who set the goal self-production sound system, must evaluate the sound critically. It will be useful to know that a suitable speaker has two or more speakers in order to be able to reflect the sound of a wide swath of the audible spectrum. But the subwoofer even in complex systems one. This is due to the fact that low frequencies cause the environment to vibrate, even penetrating through walls. It becomes unclear where exactly the bass is coming from. Consequently, there is only one low-frequency speaker – a subwoofer. But as for other things, a person will confidently say from which direction this or that special effect came (the ultrasound beam is blocked by the palm).

In connection with the above, we will divide the acoustic systems:

1. Sound in Mono format is unpopular, so we avoid touching on historical excursions.
2. Stereo sound is provided by two channels. Both contain low and high frequencies. Equal speakers equipped with a pair of speakers (bass and squeak) are better suited.
3. Surround Sound is distinguished by the presence of a larger number of channels, creating a surround sound effect. We avoid getting carried away with subtleties; traditionally, 5 speakers plus a subwoofer convey the range to music lovers. The design is varied. Research is still underway to improve the quality of acoustic transmission. The traditional arrangement is as follows: in the four corners of the room (roughly speaking) there is a speaker, the subwoofer is on the floor to the left or in the center, the front speaker is placed under the TV. The latter is in any case equipped with two or more speakers.

It is important to create the correct enclosure for each speaker. Low frequencies will require a wooden resonator, but for the upper end of the range it doesn’t matter. In the first case, the sides of the box serve as additional emitters. Find a video demonstrating dimensions, corresponding to the wavelengths of low frequencies according to science, it practically remains to copy ready-made designs; the topic is devoid of relevant literature.

The range of tasks is outlined, readers understand that a homemade acoustic system is built with the following elements:

• a set of frequency speakers according to the number of channels;
• plywood, veneer, body boards;
• decorative elements, paint, varnish, stain.

Acoustics design

Initially, select the number of columns, type, location. Obviously, producing more channels than a home theater has is an unwise tactical move. A cassette recorder will only need two speakers. At least six buildings will be released for the home theater (there will be more speakers). According to the needs, accessories are built into the furniture, the quality of low frequency reproduction is poor. Now the question of choosing speakers: in the publication by Naidenko and Karpov the nomenclature is given:

1. Low frequencies - CA21RE (H397) head with an 8-inch fit.
2. Mid range - MP14RCY/P (H522) 5" head.
3. High frequencies – head 27TDC (H1149) by 27 mm.

They presented the basic principles of designing acoustic systems and suggested electrical diagram a filter that cuts the flow into two parts (a list of three subranges is given above), the name of the purchased speakers was given, solving the problem creating two stereo speakers. We avoid repetition; readers can take the trouble to look through the section and find specific titles.

The next question will be the filter. We believe that National Semiconductor will not be offended if we screenshot the drawing of the Ridico translation amplifier. The figure shows an active filter with a power supply of +15, -15 volts, 5 identical microcircuits (operational amplifiers), the cutoff frequency of the subbands is calculated by the formula shown in the image (duplicated in text):

P – number Pi, known to schoolchildren (3.14); R, C – resistor and capacitance values. In the figure, R = 24 kOhm, C is silent.

Active filter powered by electric current

Taking into account the capabilities of the selected speakers, the reader will be able to select a parameter. The characteristics of the speaker's playback band are taken, the overlap junction between them is found, and the cutoff frequency is placed there. Thanks to the formula, we calculate the value of the capacitance. Avoid touching the resistance value, reason: it can (disputed fact) set the operating point of the amplifier, the transmission coefficient. On the frequency response given in the translation, which we omit, the limit is 1 kHz. Let's calculate the capacity of the specified case:

C = 1/2P Rf = 1/2 x 3.14 x 24000 x 1000 = 6.6 pF.

It’s not that big of a capacitance; it’s selected based on the maximum permissible voltage. In a circuit with sources of +15 and -15 V, it is unlikely that the nominal value exceeds the total level (30 volts), take a breakdown voltage (the reference book will help) of at least 50 volts. Do not try to install DC electrolytic capacitors; the circuit has a chance of blowing up. There is no point in looking for the original circuit diagram of the LM833 chip due to Sisyphean labor. Some readers will find a replacement chip that is different... we hope for your understanding.

About comparatively small capacity capacitors (retail and total) the description of the filter says: due to the low impedance of the heads without active components, the ratings would have to be increased. Naturally causing the appearance of distortions due to the presence of electrolytic capacitors and coils with a ferromagnetic core. Feel free to move the range division boundary, the total throughput remains the same.

Passive filters can be assembled with your own hands by anyone trained in soldering. school physics. IN as a last resort enlist the help of Gonorovsky, the intricacies of the passage of signals through radio-electronic lines that have nonlinear properties could not be better described. The presented material interested the authors in low and high frequency filters. Those wishing to divide the signal into three parts should read works that reveal the basis of bandpass filters. The maximum permissible (or breakdown) voltage will be scanty, the nominal value will become significant. Matching the mentioned electrolytic capacitors are capacitances with a nominal value of tens of microfarads (three orders of magnitude higher than those used by an active filter).

Beginners are concerned about the issue of obtaining a voltage of +15, -15 V to power speaker systems. Wind a transformer (an example was given, PC program Trans50Hz), equip it with a full-wave rectifier (diode bridge), filter, enjoy. Finally, buy an active or passive filter. This thing is called a crossover, carefully select the speakers, correlate the ranges more accurately with the filter parameters.

For passive speaker crossovers, you will find many calculators on the Internet (http://ccs.exl.info/calc_cr.html). The calculation program takes the input impedances of the speakers and the division frequency as the initial numbers. Enter the data, the robot program will quickly provide the values ​​of capacitances and inductances. On the page below, specify the filter type (Bessel, Butterworth, Linkwitz-Riley). In our opinion, this is a task for the pros. The above active stage is formed by 2nd order Butterworth filters (rate of frequency response reduction 12 dB per octave). It concerns the frequency response (frequency response) of the system, understandable only to professionals. When in doubt, choose the middle ground. Literally check the third circle (Bessel).

Acoustics of computer speakers

I happened to watch a video on YouTube: a young man announced that he would make an acoustic system with his own hands. The boy is talented: he ripped out the speakers of his personal computer - well, none at all - brought out an amplifier with a regulator, placed it in a matchbox (speaker system housing). Computer speakers are notorious for poor bass response. The devices themselves are small, light, and secondly, the bourgeoisie saves on materials. Where does bass come from in a speaker system? The young man took... read on!

The most expensive component of a music center. Hi-end acoustics cost less cheap apartment. Repairing and assembling speakers is a good business.

The low-frequency amplifier of the speaker system will be assembled by an advanced radio amateur; no Kulibins are needed. From matchbox The volume control knob sticks out, the input is on one side, the output is on the other. The speakers of the old sound system are small. The young man got hold of an old loudspeaker, not of fabulous size, but solid. From a Soviet-era speaker system.

To prevent the sound from disturbing the air with squeaking, the clever youth nailed together one-inch boards into a box. The speaker of the old acoustic system was placed in the size of a mailbox, moved, as is done by the manufacturers of modern home theater subwoofers. I was too lazy to decorate the inside of the speaker with soundproofing. Anyone can use batting or other similar material for the acoustic system. Small speakers are placed inside oblong boxes that just contain a loudspeaker at the end. The proud youth connected one channel of the speaker system to two small speakers, the second to one large one. Works.

The young man is a fabulous fellow, he doesn’t drink in the gateway, being like his peers, he doesn’t spoil the free time future brides, busy with business. As one acquaintance said: “The younger generation is forgiven for a lack of knowledge and experience, not an excess of arrogance, strengthened by indifference.”

Improvements

We decided to improve the method; we sincerely hope that the addition will help make the acoustic system itself somewhat better. Problem? The concept was invented by radio engineers and creators of acoustic systems - frequency. The vibration of the Universe has a frequency. They say that it is even inherent in a person’s aura. It’s not for nothing that every good speaker can accommodate several speakers. Large ones are intended for low frequencies, bass; others - for medium and high. Not only the size, but also their structure is different. We have already discussed this issue and refer those interested to the written reviews, which provide a classification of acoustic systems and reveal the operating principles of the most popular ones.

Computer scientists know the system buzzer, which operates via a BIOS interrupt, which seems to be capable of producing one sound, but talented programmers wrote elaborate melodies on it, even with an attempt at digital synthesis and voice reproduction. However, such a tweeter cannot produce bass if desired.

Why this conversation... A large speaker should not just be adapted to one of the channels, but should be given a specialization for bass. As you know, most modern compositions (We don’t take Sound Around) are designed for two channels (stereo playback). It turns out that two identical speakers (small) play the same notes, this makes little sense. At the same time, from the same channel, the bass is lost, and the high frequencies die on a large speaker. What should I do? We propose to introduce passive bandpass filters into the circuit, which will help split the flow into two parts. We take the diagram from a foreign publication for the simple reason that it was the first one that caught our eye. Here is a link to the original site chegdomyn.narod.ru. The radio amateur copied it from the book, we apologize to the author for not indicating the original source. This happens for the simple reason that he is unknown to us.

So, here's the picture. The words Woofer and Tweeter immediately catch your eye. As you might guess, this is, respectively, a subwoofer for low frequencies and a speaker for high frequencies. The range of musical works is covered from 50-20000 Hz, with the subwoofer accounting for the low frequency band. Radio amateurs themselves can calculate the passbands using well-known formulas; for comparison, A of the first octave, as is known, is 440 Hz. We believe that such a division is suitable for our case. I would just like to find two large speakers, one for each channel. Let's look at the diagram...

Not really musical scheme. In the position occupied by the system, the voice is filtered. Range 300-3000 Hz. The switch is signed Narrow, translated as a stripe. To get Wide playback, lower the terminals. Music fans may want to throw out the Narrow bandpass filter; those who like to surf Skype should avoid a hasty decision. The circuit will completely eliminate the microphone loop effect, which is known everywhere: a high-pitched hum due to over-amplification (positive feedback). A valuable effect, even a military man knows the difficulties of using a speakerphone. The owner of the laptop is aware...

To eliminate the feedback effect, study the issue, find at what frequency the system resonates, cut off the excess with a filter. Very comfortably. Regarding popular music, we turn off the microphone, move it away from the speakers (in the case of karaoke), and start singing. We will leave the high and low pass filters unchanged, the products were calculated by unknown Western friends. For those who have difficulty reading foreign drawings, we explain that the diagram depicts (the Narrow bandpass filter is discarded):

1. Capacitance 4 µF.
2. Non-inductive resistances R1, R2 with a nominal value of 2.4 Ohm, 20 Ohm.
3. Inductance (coil) 0.27 mH.
4. Resistance R3 8 Ohms.
5. Capacitor C4 17 uF.

The speakers must match. Advice from this site. The subwoofer will be MSM 1853, the tweeter (the word has not been written off) will be PE 270-175. You can calculate the bandwidth yourself. The capital letter Ω means kOhm - no big deal, change the value. We remind you that the capacitances of parallel-connected capacitors add up, like series-connected resistors. In case it is difficult to get suitable denominations. It is unlikely that you will be able to make speakers with your own hands; it is realistic to obtain small resistance values. Do not use coils; we cut out plates of nichrome or similar alloys. After manufacturing, the resistor is varnished; high current is not planned; the element should not be protected.

It is easier to wind inductors yourself. It is logical to use an online calculator, by setting the capacitance, we will get the parameters: number of turns, diameter, core material, core thickness. Let's give an example, avoiding being unfounded. We visit Yandex, type something like “ online calculator inductance." We receive a number of output responses. We choose the site we like, and begin to think about how to wind the inductance of an acoustic system with a nominal value of 0.27 mH. We liked the site coil32.narod.ru, let's get started.

Initial information: inductance 0.27 mH, frame diameter 15 mm, PEL wire 0.2, winding length 40 millimeters.

The question immediately arises, seeing the calculator, where to get the nominal diameter of the insulated wire... We worked hard, found a table on the website servomotors.ru, taken from the reference book, which we present in the review, consider it for your health. The diameter of the copper is 0.2 mm, the insulated core is 0.225 mm. Feel free to feed the values ​​to the calculator, calculating the required values.

The result was a two-layer coil with 226 turns. The length of the wire was 10.88 meters with a resistance of about 6 ohms. The main parameters have been found, we begin to wind. A homemade speaker system is made in self made case, there is a place to place the filter. We connect a tweeter to one output, and a subwoofer to the other. A few words about amplification. It may happen that the amplifier stage will not support four speakers. Each circuit is characterized by a certain load capacity; you cannot jump higher. The speaker system is designed with a fixed headroom in mind; to match the load, an emitter follower is often used. The cascade that makes the circuit work, full impact on any speaker.

Parting words for beginning designers

We believe that we have helped readers understand how to properly design an acoustic system. Passive elements (capacitors, resistors, inductors) can be obtained and manufactured by anyone. All that remains is to assemble the speaker system body with your own hands. And we believe that this will not be the case. It is important to understand that music is formed by a range of frequencies that are cut off by improper manufacturing of the device. When you are planning to make a speaker system, think about it and look for the components. It is important to convey the magnificence of the melody, there will be a strong confidence: the work was not in vain. The speaker system will last a long time and will give you joy.

We believe that readers will enjoy making speaker systems with their own hands. The coming time is unique. Believe me, at the beginning of the 20th century it was impossible to obtain tons of information every day. Training resulted in hard, painstaking work. I had to rummage through the dusty shelves of libraries. Enjoy the Internet. Stradivarius impregnated the wood of his violins with a unique composition. Modern violinists continue to choose Italian examples. Think about it, 30 years have passed, the cart has been left behind.

The current generation knows the brands of adhesives and the names of materials. Necessities are sold in stores. The USSR took away the abundance of people, providing them with relative stability. Today, advantage is described by the possibility of invention unique ways earnings. A self-taught professional will cut down cabbages everywhere.

Having on hand a number of old and very ordinary Soviet speakers, I wanted to assemble speakers on them (MAS - small-sized speakers) and see what could be gotten from this idea.
I think that the design is suitable for repetition, the cost of components is low. If I used rare imported speakers, the possibility of exact repetition would be minimal. The frequency range of the finished speaker is 40…20000 Hz.

Selecting the speaker type

There are 6GD-2 speakers and some others, but they are in short supply and you definitely can’t make small-sized speakers with them; 6GD-2 require boxes the size of a small refrigerator.

To get a more or less low frequency on the shield, it must be very large, this is also not a MAC. For MAS, only FI remains because, in my opinion, there are no Soviet speakers capable of providing bass in a small ZY.

All the woofers I know have a rubber surround (they had foam rubber, but at the moment they require mandatory replacement of the surrounds, and the volume of the box will be too big for MAC) and they sound bad in the midrange, and these frequencies are very important for me because I think that they determine the overall sound quality.

All Soviet MACs are made using a two-way design, have a high crossover frequency, approximately 5 kHz, and therefore sound inexpressive due to the fact that the “rubber” low-frequency speaker does not sound above 1...2 kHz in the best possible way.

Most industrial speakers, even those assembled using a three-way design, also sound muddy in the midrange because they usually have a “rubber” 15GD-11 installed. This circumstance is the reason for the huge number of articles on the conversion of 25AC, 35AC and their clones. Therefore, a three-way version with a paper midrange speaker was chosen for the project.
In addition, I believe that for the midrange dynamics best design- shield or shallow OYA. The shield is preferable in terms of sound, but is inconvenient in design.

Therefore, the choice of column type is as follows: three-way, woofer in a small box with FI, midrange speaker in a small shallow OJ, tweeter on a tiny shield.

The midrange speakers also need to be improved. Soak the corrugation (the entire diffuser cannot be soaked) with a liquid solution of guerlain. The process is described in detail by Shorov and his followers.
But this was not enough. When listening to the assembled and configured speakers, the sound was somewhat harsh. The reason turned out to be the high acoustic quality factor of the speakers. I had to use PAS, which gave a noticeable positive result.

Attempts to modify the 2GD-36 using the method of improving the 3GD-31 did not give a positive result.

AC crossover filter

I was unable to smoothly mix the midrange and high-frequency speakers at a frequency of about 5 kHz; I was forced to succeed only at a frequency of 8...9 kHz, which has its drawbacks. LF-MF section at 500 Hz.

Unlike parallel filters, where the filter for each speaker can be adjusted separately and independently, there is an unwanted interdependency that makes adjustment difficult.
The result is a filter like this.

According to the author of this solution, the circuit has the smoothest joints since everything that is cut off by the low-pass and high-pass filters goes to the midrange speaker. The idea is interesting and everything would be so if there were resistors instead of speakers. But, as I have written many times, speakers, like electromechanical devices, have their own temper and the result may not live up to expectations.

Speaker design

The front panel of the speaker is removable.

The midrange speaker is in the OJ, it is advisable to make it minimally deep. The PAS is cut out of a piece of laminate, the large hole is for the magnetic speaker system, the small ones with a diameter of 10 mm are for the PAS. The number of holes is not critical; about 20 can be made.

The tweeter is mounted on a small rectangular piece of laminate.

Since three independent housings were made, it became possible to move the speakers inward. The midrange is shifted by about 4 cm, the treble is also shifted by 4 cm relative to the midrange. And if the shift of the midrange speaker relative to the bass has little effect on the shape of the measuring pulse, then the shift of the tweeter is quite noticeable, the shift value was chosen optimal for listening to speakers from a distance of 2...2.5 meters.

I would like to note that if all the speakers are traditionally placed in one housing, this shift will be very difficult. Imagine an 8 cm deepening...

One can argue about the usefulness of such a solution, but it was tried on in some speakers for a very long time and I think that it was abandoned due to its low technology.
However, this solution is still used today, but not in wood, but cast housings– plastic or metal. To do this, the recess is made flat; some believe that this is a horn, but this is not so - this is a way to move the speakers inward.

I think music lovers will hear the difference; I did not conduct special tests on music, but configured them using computer programs and a microphone.

The height of the speaker is 73 cm, if you listen while sitting in a chair, a stand for the speaker is not needed. The direction of the midrange and tweeter axes was chosen deliberately.

If anyone wants to repeat my “15MAS-1”, you can buy a pair of 15AC-109 in good condition (clones are not suitable) for LF boxes.
You will need to remove the tweeter and plug the hole; you can use a standard FI pipe.

Results

I think it’s better than any Soviet small-sized speaker, which is not surprising because they are two-way.
As for industrial three-lanes, the situation here is ambiguous. It is clear that in terms of power (volume level), my speakers cannot compete with the 25AC and 35AC series of clones.
They cannot compete in terms of the amount of bass, despite the fact that my speakers operate from approximately 34 Hz ​​at a level of -3 dB, a speaker of such a small diameter is noticeably inferior in power to the woofers of the 25GD, 30GD series.

But 2GD-36 sounds softer than 10GD-35. And the main advantage is in the midrange. Rubber 15GD-11 sound clearly worse, although louder. I think the overall balance is in favor of these MACs, but not for lovers of killer bass.

For home use, the volume of these speakers is quite sufficient, despite the low sensitivity of the 25GDN3-4. But for a disco - no. But quality is not needed for a disco.

The purpose of my experiments was to try out some techniques and tuning methods, see what can be done from cheap and affordable speakers, and if the result is positive, offer Datagor readers a new article.

I think that the design is suitable for repetition, the cost of components is low. If I used rare imported speakers, the possibility of exact repetition would be minimal.
The frequency range of the speakers is at least 40...20000 Hz, in fact, according to the standard method, even wider.

The speakers work well.
I don’t give measurement graphs; anyone who wishes can measure it themselves, for example, using the methods I described on Datagor.

Thank you for your attention!

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