A column is a speaker system of very modest dimensions, which has one or more loudspeakers with a built-in amplifier. Speakers are used to increase the sound volume, and the sound is increased using speakers. Speakers are made up of two magnets, usually a ceramic permanent magnet and an electrical magnet controlled by an audio amplifier. These magnets produce sound when they interact. Speakers are divided into two more categories: passive - that is, in which an audio amplifier is not built in, for example, headphones; and active - respectively speakers that have their own built-in audio amplifier. The active speaker system has its own power supply. In this article, you will see how to make a do-it-yourself homemade active speaker system. This column can be connected to a computer, and to the phone, and to the player, and so on. To make this homemade product, I needed:

Materials:
1) Two speakers with a power of 3 watts each (they will serve as a sound source);
2) Three and a half mm plug for connecting the speaker to various devices;
3) (the amplifier will receive sound signals from some device and transmit them to the speakers amplifying these signals);
4) Switch to turn off the speaker power;
5) Wires for connecting contacts;
6) Insulating tape for wire insulation and other needs;
7) USB plug for power supply;
8) Heat-shrinkable tubes for insulating bare contacts;
9) Plywood (the body will be made of plywood, as this is the most affordable material);
10) Self-tapping screws for body assembly.

Tools:
1) Electric soldering iron for soldering wires;
2) Glue gun and hot glue for gluing some parts and for insulating contacts;
3) Stationery knife for cleaning wires from insulation and for other needs;
4) Lighter for heat shrink tubes;
5) Hacksaw for sawing plywood;
6) Jigsaw for sawing round and other holes on plywood;
7) Electric drill for drilling holes;
8) Screwdriver for tightening self-tapping screws;
9) Ruler and pencil for drawing notes on plywood for the column body;
10) Sandpaper for polishing the case;
11) Nippers for cutting wires and extra contacts;
12) Compasses for drawing circles.

The process of making a homemade active column.

Let's prepare two three-wool loudspeakers, a 3.5 mm jack and a PAM 8403 audio amplifier and connect their contacts using connecting wires.

The characteristics of the speakers are written on the back of them, namely, here they are:

The 3.5 mm jack has three pins: left channel, right channel and common. There are four more contact plugs: left and right channels, common and microphone; but in this column there is no microphone and why, so you can not use a four-pin plug. The meanings of the plug contacts are shown in the photo.

We will use the audio amplifier, ordered from Aliexpress of very good quality, as mentioned earlier. This amplifier is powered by a voltage of five volts, so the future speaker can be connected to both a laptop and a phone charger...

We will also use the power button to turn off the column.

We take the wires and clean their ends from insulation with the help of clerical pressure for future soldering.

We solder these wires to the audio amplifier using an electric soldering iron, but be very careful not to spoil or damage the amplifier.

In my case, the blue wire is positive and the brown wire is negative.

We cut off the extra protruding contacts with the help of wire cutters in order to look neater.

We fix the wires together with insulating tape.

It should turn out like this, as shown in the photo.

Now solder the power wire to the amplifier with a USB plug. Yes, at the end of the article the wire will be white, since I resoldered it due to insufficient length, so do not judge too much.

We clean the wires of the USB wires and solder one of the wires with an electric soldering iron to the speaker power switch.

Isolate the wiring with heat shrink.

Now we solder the resulting two wires to the audio amplifier, always observing the polarity: in my case, brown is minus, blue is plus.

Again, we bite off the excess on the board with wire cutters.

That's what I did:

Now solder a wire with a 3.5 mm plug to the audio amplifier.

The wire must have at least three contacts, but exactly three is better.

We strip the wires and solder them to the 3.5 mm plug.

Now we solder the wires to the audio amplifier, but each posting in its place.

According to the colors of the wires, we solder them to the board, namely the black wire is the left channel, which is marked on the board with the letter L; red wiring is the right channel, which is marked on the amplifier with the Latin letter R; and the green wiring is a common channel, which is marked on the amplifier, respectively, with the Latin letter G.

Now we isolate the 3.5 mm plug with heat shrink and hot glue.

In general, I got it like in the photo.

Now a more complex process begins, namely, the preparation of the body.

Drawing a rectangle on plywood, dividing it in half we get two identical squares, in each of which, in the center of the squares, using a compass, we draw circles of equal diameter for future speaker seats.

Using an electric drill, we drill a hole for threading a jigsaw into this hole.

Cut out the rectangle with a hacksaw.

Using a manual jigsaw, cut out circles from a rectangular part of the column body.

Three-watt speakers are easily inserted into the two holes obtained.

And two more rectangular parts of the same size.

For now, we assemble the body from everything received.

Now you need to fix the audio amplifier on the front of the case.

To do this, we drill a hole with an electric drill, it is necessary that the amplifier is freely and securely installed in this hole.

On the inside of the part near the drilled hole, using a clerical knife, we pick out a recess for the amplifier board.

Dedicated to those who have free time

We open a popular magazine about good sound and look with pleasure at the elegant images (if not the image) of acoustic systems, but there is something to see. Powerful towers bristle in all directions with speakers, shine with their varnished sides, crush the parquet with sharp spikes and generally evoke a feeling of deep respect. It seems that they have only one drawback - this, of course, is the price. A quite logical question arises, what if you make a copy of a monster yourself? It is not difficult to buy a speaker, to assemble a case, albeit not so beautiful - too, coils and capacitors can be domestic, carefully solder 3 parts - and it’s a task for a student of the 10th grade of the school.

With the number of off-the-shelf modules that Ebay has to offer, making a good amplifier isn't much more difficult. What is there just not there: switching, speaker protection, A-AB-D class boards, volume controls for every taste, beautiful cases made specifically for audio, knobs, legs and transformers - just know how to connect. In the next article, we will definitely tell you how to assemble your own amplifier, which will not yield to most "brand" samples worth up to 60-70 thousand rubles.

You may come across unfamiliar words later in the text. Fortunately, an unknown audiophile came to our aid and left link to your personal archive of information on acoustics and amplifiers, there is really ALL and even more, highly recommended for review.

What to do? Plywood, MDF, chipboard, plastic, solid wood.

The world has seen many strange acoustic structures, for example, made of concrete or cinder block. Yet the most "demanded" are the above wood-based lumber. Let's try to understand which one is "more correct". The basic rule - regardless of the material chosen, do not save on its quality, that is, the price.

The first is the king of the modern Hi-Fi and Hi-End industry - MDF, the vast majority of speakers, both expensive and cheap, are made from it. The reason is simple - low cost, ease of processing and finishing, including options with finished veneer, the absence of bright resonances. With proper design, optimal results are guaranteed. Recommended, nothing more to say.

Plastic - the concept is very loose, its "authority" is significantly undermined by cheap Chinese fakes, although it has no less advantages than any other material. The problem of the inaccessible opportunity for an amateur to cast their workpieces from the desired material - we pass by.

A good material for making a speaker cabinet can be Chipboard. Perhaps its main drawback is a lot of problems with finishing, no matter what you decide: paint, veneered or fitted. Chipboard has a huge plus: if you need to do it quickly and very cheaply, then you can use a factory laminated board (LDSP). In this case, it is unlikely that it will be possible to achieve high aesthetics, but the price and speed will leave all other contenders far behind. If we compare the resonant properties of materials in terms of suitability for speakers, chipboard takes first place, although the difference compared to MDF is small.

Capricious, but invariably desired by "hardened audiophiles" Mrs. plywood. There are several types of plywood - birch, coniferous, alder, laminated. Why capricious? Any plywood "leads", that is, when it dries, the sheet changes its geometry, when sawing, chips often appear. Also, this is not the easiest material to finish if you want to get a “deaf” matte color without protruding edges, textures, edges. The reason for enduring these torments is rather controversial: according to the “experienced”, only plywood gives the very living breath that chipboard and MDF “kill”. What I don’t understand the most is the desire to make a body out of “live” plywood and “kill” it with layers of putty, primer, paint, varnish in an attempt to hide the “terrible” joints with veins (layers of plywood), which day and night look with mute reproach at their owner . Much more preferable are the options for special impregnation, at least with the same “Danish oil”, these dark “stripes” on the ribs of the case are not so terrible ...

What kind of poverty is this chipboard-MDF? Maybe immediately from solid oak, but thicker!? Do not rush to insert the speaker into the first hollow you see. Contrary to expectations array fine wood does not enrich the sound in proportion to the money invested, in fact, it even requires additional damping compared to cheaper materials. Although its undoubted advantages are the convenience of finishing: if the acoustics are assembled carefully, it will not be difficult to bring them to a nice eco-look. Instead of increasing the thickness, it is recommended to add (glue) another sheet of less resonant material on the reverse side, for example, the same MDF, to make a “sandwich”. The most successful use of the array is a "shield" acoustics, where a beautiful and heavy front panel is required.

Exotic. Often the choice is determined by what is at hand. Just as a bird can masterfully weave any rubbish into the nest, so the music lover drags everything that lies badly. You can find ideas on the net, embodied from plumbing pipes, artificial stone, papier-mâché, cases and cases from musical instruments, primitive building materials, IKEA products, etc., etc.

Where to put the speaker?

The main task of acoustic design can be formulated in simple language approximately as follows: to separate as much as possible the vibrations emitted by the front side of the speaker cone from the same anti-phase vibrations emitted by the rear side of the cone. The ideal acoustic design from a textbook point of view is considered to be an infinity screen, such an incredibly huge shield in which the speaker is installed. Obviously, the words "incredibly huge" do not fit either our home or salary, so the engineers began to look for a way to "fold" this screen with minimal negative consequences for the sound. So it turned out all the variety of options, some have earned themselves the most extensive fame on the Internet, and we will consider them in this article.

Just speaker or case without case

It’s hard to imagine that there is such a kind of “acoustics”, but, scrolling through the photo feed on pinterest on the topic of audio, I increasingly come across clusters of 12-inch speakers that are assembled together without any design and clearly represent a complete unit. Probably, the author’s intention is permeated with the following logic: any case spoils the sound, an acoustic short circuit is better than wooden fetters, but in order to have at least some kind of “low”, you need to take speakers with the maximum cone area, for which there is only enough money. If this is your path, no comment.

Shield and "broadband"

It is said that those who have tried the lamp, full-range speaker and open design never return to the traditional, transistor-rubber lifestyle. Describing the properties of the shield is not a rewarding task, all the necessary information is in the archive, and for the laziest - on youtube, where they explain in detail what kind of animal it is and what it is eaten with, for example: .

The biggest advantage of this design is ease of manufacture. You need a sheet of your favorite material and a jigsaw. The most important criterion that will affect the final sound quality is the cost of the installed dynamic head. The 4a32 speaker gained unceasing popular fame, even such giants as fostex, sonido, supravox, sica or the visaton B200 itself were left far behind. The adage "size matters" is the best mathematical formula for a shield (the bigger the better). Then there are shield variations, for example, a shield with rolled-up side walls, a shield in which the low-frequency module is made in the form of a box with a phase inverter, etc. A signature feature of the sound is an "airy" sound with a minimum of resonances, with a relatively high sound pressure.

PAS - acoustic impedance panel

What if you try to cross a shield and a closed box? You will get a box with a back wall in which many holes are made. The number of holes, their total area in combination with the volume of the box will determine the degree of damping (resistance), the level of low frequencies (the fewer “holes” - the more bass, but also more “buzz”). The amount is selected experimentally, to taste.

Line array of emitters, group emitter (GI)

In fact, this subspecies of acoustics concerns more speakers than the design of the case itself. I think you have already seen speakers, each of which consists of a large number of the same small, small speakers, well, or not very small, as your budget and living space allow.

According to the electrical circuit, the heads are connected in series, that is, the "plus" of the previous one is connected to the "minus" of the next one, it is possible to combine a series-parallel connection. The number of speakers, in fact, is also limited only by money, common sense, as a rule, has already disappeared without a trace by this moment. Do not think anything bad about me, I tried such a perversion, I even liked it, if possible, I strongly recommend that you assemble a similar design for yourself, if only for the sake of interest. Again, the budget for this outrage is not very large, as a rule, domestic speakers are used in good condition, 5gdsh, 8gdsh, 4gd-8e, etc.

Acoustic design - the same shield or a closed box, preferably a cunning shape, such as a triangular one. One of the problems to be faced is the high total resistance, not every amplifier will reveal the potential of the "array". Factory-produced serial samples have more complex solutions, speakers are often assembled into tricky modules, filters are added.

Phase inverter, bass reflex port, Helmholtz resonator, aka a box with a "pipe"

Here it is - the most popular option for acoustic design. The most profitable in terms of price / result obtained becomes mass, our case is no exception to this rule. For those who have not downloaded the archive of an unknown audiophile, we explain on the fingers. There is a certain amount of air in the phase inverter pipe, which depends on its length, it is also “connected” with the air contained inside the column. With a successful adjustment of the length of the pipe (we will not immediately dive into the theory), it is possible to achieve a more confident reproduction of low frequencies than just in a closed box. If even simpler - with a bass reflex you get deep bass. For a more in-depth understanding, here is a video from the channel we have already fallen in love with:

Although this type of acoustics is popular, it is far from being so easy to manufacture, one pulls after another. Speakers that are suitable for this design are called "compression", most often have a rubber surround and a frequency band that requires the installation of a high-frequency link, tweeter or tweeter, that is, an electric filter is added. The choice of the optimal body volume, its geometry, fine tuning of the pipe length are of great importance and do not always correspond to the calculated values. The situation is facilitated by the presence of a mass of projects on the network, where the authors have already gone through a thorny path and offer step-by-step instructions with a detailed description of what, how, what to do. However, there are always enthusiasts who are not satisfied with the "ready" and have enough perseverance to go their own way. The disadvantages of a phase inverter are “bubbling” and “crushed middle”. The first is solved by careful selection of the shape, diameter, material and length of the pipe; the second - by adding a separate mid-frequency link. The right way to three-way acoustics.

TQWP Reverse Shout and Other Labyrinths of Destiny

What people just didn’t come up with to complicate the path of vibrations coming from the back of the speaker ... Perhaps the most distinguished company was B&W with their Nautilus, at least put a monument to this mutant seashell. But these are giants, and all we, ordinary audiophiles, can do is remember our nightmares and put planks with nails inside a rectangular box so that this filthy sound doesn’t seem enough. Seriously though, there are some speakers for which the design of the “phase inverter” type is not suitable, and the shield does not give the desired amount of bass, but the sight of a subwoofer makes something in the stomach shrink. Then a reverse mouthpiece or a more complex version - a labyrinth - comes to the rescue. For those who are interested in how it works, we wish you a pleasant viewing.

Someone may object: the reverse horn is not quite a labyrinth, we can partly agree, but what is more reliable is that it is closer to labyrinths than the classic horn

reminiscent of an old gramophone. As you can guess from the name, the backhorn or labyrinth is far from the simplest type of acoustic design, it requires a good understanding of the theory, accurate calculation, or at least following the factory recommendations. For example, large manufacturers of full-range speakers, as a rule, provide a couple of options for cabinet drawings in the documentation for their speakers.

Onken, closed box (ZYa), horn, passive radiator and others

Our story follows in the footsteps of popular popularity, and this is a rather narrow list. A closed box almost always hums, it’s hard to pick up a speaker for an onken, the horn is large in size, difficult to manufacture and calculate, the passive radiator works well, but for some reason it didn’t take root in amateur designs. You can probably find a few more rare types or subspecies of design that are not mentioned here, what to do, you won’t cover everything.

Damping, "stuffing", "plug"

The hulls are ready, what to do with them next? That's right, dampen. Damping can be divided into two types: vibration absorption and sound absorption. Automotive materials, mastics and special sheets with an adhesive layer are well suited for vibration absorption, the latter is preferable. With sound absorption, confusion and reeling are observed, someone likes felt, someone likes wool, batting, synthetic winterizer, etc. The answer is quite simple - for a different effect, depending on the type of case and the frequency that you want to suppress, the choice of material will depend. Filling the case with sound-absorbing material increases its virtual volume, however, in my opinion, it is impossible to determine a universal norm.

Setting the crossover (crossover)

You have decided to make multi-band acoustics. Is a measuring microphone required? If this is a one-time project, then no, it is not needed, it is enough to have a test selection of tracks and some experience to understand which sound can be called more correct. It will just take longer to go through the details of the passive filter, listen and compare, but in the end the result will be exactly the one that your ears, the room need. The situation is a little easier with active crossovers. Previously, they had to be made on their own, etching and spreading boards, soldering, a very dreary process, especially if the circuit has a decent cutoff and adjustment steepness, for three-way acoustics it’s just a wild thing. Fortunately, today it’s enough just to go to ebay and choose the option you can afford, whether you want on opamps, or on DSP. You can adjust the frequency, and sometimes the steepness of the cut (in very rare cases, the phase), even smoothly every day.

The final

Sometimes it seems to me that the situation in the world of audio is reminiscent of the legend of the Tower of Babel. Once upon a time, before Van Den Hul's foot had set foot on the ground, people built together one set of home stereos. Big, big speakers, no less big amplifier, and thick, thick cables stretched to them. Someone from above saw this and was horrified - well, game, even if they read some books ... Severe punishment befell unlucky audiophiles, since then they have been arguing until they are hoarse, but they still cannot agree on how to make amplifier speakers, so everyone makes their own , how can.

I dedicate this material to all DIYers and wish them good luck in their work.

Start

Dear friends, allow me to introduce myself. My name is Yuri. He received his name in honor of Yuri Alekseevich Gagarin, like many boys of that period. That's how popular he was when I was born. Apparently, the energy of that time and the name of the first cosmonaut was transferred to me to some extent and became a part of the soul that required activity. During the school years, the activity was multidirectional, but did not include studies. In life, this did not become a hindrance. Graduated from the Technical University with honors. I have not changed my profession, chosen on the basis of the maximum complexity of the specialties offered by the university I entered, and I still earn it. They taught me to be a designer of hydraulic machines and means of their automation.

In his free time from work, all sorts of hobbies did not let go further. In another spiritual outburst that happened quite recently, I discovered a wonderful Audiomania store, in particular, its “Do It Yourself” section. What I saw there on my first visit was a dream of youth. True, in those days it was impossible to imagine. The assortment of this store opened the door for me to the world of ideas implementation. I think, as for many other obsessed with ideas, people.

In addition to my passion for audio technology, which accompanies me through life, I love photography, I read science fiction (necessarily about space travel - that same energy works out). And one more hobby - for almost a dozen years I have been making wooden furniture. Now there is already a serious experience of a cabinetmaker, which allows him to make furniture professionally.

Creating acoustics, which will be discussed, is one of my old hobbies. But, the accumulated experience, today's opportunities and new desires made it possible to set ourselves a difficult task - to create acoustics for the home, conveying the dynamics, scale and emotionality of a concert performance of music.

To all readers - my immense location and best wishes.

Yuri Kobzar

I am an amateur. I will try to write only about the specifics. I will share my practical experience in creating high-level acoustic systems. I address this information to the same amateurs who like high-quality sound, who enjoy not the background, but listening to music. People who are in the world of sounds, have preferences and favorite records.

In the spring of 2017 something happened to me. In the evening, on the veranda, a bird's chirp reached my ears, a real warmth blew, somewhere it turned green, the first vegetable aroma flew in, I wanted to sip wine and listen to music. Without analyzing (one can attribute everything to the fluctuations of the soul), I felt the need, and I had the idea to get a good sound for the house. Moreover, there is “music” in the house. But at that moment, the term good sound suddenly took on a different meaning. Memories popped up in my head from casual listening to music in a store (in a high-end room), a great opportunity to experience the highest quality sound with a few friends. All this happened years ago, but the need for a good sound took shape precisely in the spring of the seventeenth. Despite the fact that a reverent attitude towards “good” music has accompanied me all my life, and almost always there was an opportunity to listen to sound of decent quality, it suddenly became clear: music sounding from acoustics should not just be pure, detailed, powerful, deep, natural, bewitching or even amazing (the body at high volume is a joke). The sound reproduced by acoustics should convey emotions: soloists and musicians, and all those who prepare the recording for us - listeners.

According to preliminary estimates, possibly overestimated, it turned out to be too expensive to buy such equipment. I didn’t want to exchange for a good affordable one. Thus, the task arose to build the acoustics of the highest class available at home. Without laboratories, high-precision measurements, but in order for the breed, the solidity and elitism of the sound was undeniable. To create such an impression from listening.

As a small digression, it should be said that the idea had a base. I had certain skills at my disposal: in my youth I built acoustics in a “closed box”. I was happy with her sound. Various transistor amplifiers were soldered, one model is extremely high quality. Now, in addition to the former half-forgotten knowledge, skills and experience, a love for making furniture from wood and a certain set of carpentry tools have been added. Additionally, I wanted to get a high-quality tube amplifier. In order to shorten the implementation of the plan, he offered the participation of his friend, an enthusiast and homemade, who has the base of the radio department of the UPI (Ural State Technical University). We agreed that acoustics (rebounds, calculations and implementation) would be my task, lampovik is part of it.

From this position, they began to "shake the old days."

Choice

The question of building AS was started with the study of theory and related materials. Before me, as well as before many builders of their own acoustic systems, the question arose of choosing an acoustic design. Knowledge, information, opinions began to be accumulated and systematized, but the answer to the question about the type of acoustic design of the speakers remained open. At this time, three broadband heads 75GDSh3-1 became available to my partner. A local recreation center decided to throw away two stage subwoofers that had worked for over 30 years. Each had two speakers. In one of them, the speaker failed, hence the decision to throw it away. Listening to the speakers "on the floor" confirmed the "no sound" expectation. Listening in the native subwoofer case - the assessment has not changed. Almost without enthusiasm, I began to dig the Internet on the topic of using speakers of the existing type in speakers. Materials of comrades who had already built speakers based on these speakers were quickly found. I liked the option with “tekuvete” (tqwt) Voigt’s pipe - I am attaching the material, authorship has not been established, see link). I liked this option, including because of the "open case", to which some sympathy has already arisen. Why: no speaker damping or minimal damping as needed. In other words, the dynamic head is not obstructed during operation, and this, as I understand it, means a minimum of conditions for creating external resistance and, as a result, distortion. Still, the resonant frequency of the speaker in the housing with the pipe does not change. This, in turn, should ensure the reproduction of a richer bass component, which is the basis of the rhythm, providing surround sound and enhancing the psycho-emotional perception of the musical program. With internal resistance (after listening to the speakers), fear of getting a weak result and, nevertheless, with hope, I bought three sheets of 12mm construction plywood to repeat the proposed design in the material. The refinement consisted in the use of radius transitions in each corner (bent plywood for the first time), the installation of a stiffening rib inside (taking into account the dimensions and thickness of the material) and the device of a rigid removable rear wall for the convenience of work on subsequent possible damping.

I do not give the manufacturing technology. Open up too. Taking into account my experience of working with wood, I believe that each craftsman who undertakes the manufacture of such a structure will have his own specific design and manufacturing work. Specificity is associated with conditions, skills and a set of tools. I'm used to working with glue, refusing metal fasteners (except for a removable back wall). This ensures the absence of technological rails that take volume, give additional geometry in the sound channel, which, from my point of view - certified hydraulics - is not good for the movement of a sound wave through the channel. And the task, by the way, is to create conditions for its smooth, laminar (there is a term that means the absence of turbulence) movement through the channel. This reduces the chance of overtones that are unnecessary for high-end sound.

The sound of the built speakers surprised me right away. Powerful, bright, beautiful and different from my branded three-way bass-converter (FI) speakers of the English brand. Considerably excellent. Emphasis on the word "excellent". Surprise was intensified by the fact that in the same place - England, the intelligence of engineers and large-scale production, and here is a 35-year-old miracle in a plywood box. After the first surge of emotions subsided, it became clear that one speaker was not enough for this speaker. Not enough tops and ... bottoms. The bass is low, beautiful, with many shades (which is not heard on FI) and, at the same time, weak. You can persuade yourself to such a sound, but the disadvantage is noticeable.

Having doubts about the ability of this speaker to play bass in a full-range speaker, he built a narrowing maze - a transmission wave line (TVL). According to reviews on the network - this is just what you need. I describe without details and arguments in favor of such a decision. I do not give recommendations and dependencies for the construction of TVL. Everything is on the Internet. This design was made more technological: with legs, without fillets. It should be noted that the speakers turned out to be more compact in size. Here is her cut.

Many authors in the network mention the importance of correctly made calculations of the transmission-wave channel, the absence of fundamental errors, the complexity of the design and the need for its exact repetition during manufacture. At the same time, apart from the geometry and the rules for choosing speakers, there is actually nothing in their approach. When drawing the design of speakers with TVL, I was accompanied by a feeling of deep understanding of mechanics, but not acoustics. He did everything on faith. After all, many people have already shared their practical experience, the results achieved and photographs. Many were satisfied with the received sound. It's a weighty argument.

Again took construction plywood. This time, two sheets, taking into account the remnants of the previous version. Produced quickly and accurately. It should be emphasized the excessive rigidity of the hulls of such structures, even when using 12mm plywood.

So, the listening experience is very good. The disadvantages are the same. If the lack of treble is the design of the speaker, then the lack of bass is the case. It should be said that the bass has become more expressive and emphasized. This was noted independently by all participants in the audition. The surprise was this. At first, each column was listened to separately. I wanted to hear its capabilities, compare with another option. Moreover, the first experiment of repeating the design gave only one column. Then they were connected together. The effect was amazing. There was not only a panorama of sound, a stage. First of all, the sound itself has changed. His power, openness, lightness stunned! Yes, later, while listening to an unequal pair of speakers, I had to raise the treble and bass on the amplifier. But the sound was not just beautiful. He held and pulled. Favorite tracks sounded like listening to them for the first time. On many, shades of bass and mids began to be heard, the existence of which I had not even suspected before with English floor speakers. A friend of the wife, who was present with her in the house in the next room while testing a pair of speakers at different volumes and styles: chamber music, jazz, electronics, leaving, said that she had visited the Philharmonic or at a concert. This phrase was not a delicacy towards the owners, but similar to the truth. The spread of sound through adjacent rooms turned out to be a pleasant surprise. This will be an important point when receiving guests to create a light, unobtrusive musical accompaniment in several areas at once. The equipment began to turn on with each pass by. And, in the end, after three days, he finally gave up and asked the future owner to take this test version of the acoustics home to listen to until the time comes for the production of front-end speakers.

The conclusion was this: if there was a choice of speakers in the store, the sound of the received speakers (not a plywood look, of course) would suit me completely. About the received sound it is said modestly. The sound is grand. When a couple of speakers are playing, the high frequencies are practically enough. This is not sand, the speaker cannot reproduce it. But what he reproduces already met our requirements. The resulting sound shocked, turned something inside, there were lumps in the throat. Without exaggeration. There was only one "splinter" - the bass on the amplifier was twisted to the maximum. Nevertheless, the owner of the speaker also liked the sound. Later, it was even decided to make the final version on the basis of TVL: the dimensions and sound of the bass took over.

ordeal

In the meantime, the issue of creating an AU for "own use" has become topical. It is highly likely that after the speakers on the 75GDSH3-1 speakers, the search for good sound would come to an end. Pretty quickly it happened, and hit almost to the point. Fortunately or unfortunately, but the second pair of heads 75GDSH3-1 or 3-3 was not found. Crawling on the World Wide Web, collecting and analyzing information, continuing his studies, he began to closely examine the acoustics of the English company Tannoy. An ideal speaker is a device that can linearly reproduce the entire spectrum of sound from a single point. And life is full of compromises. Creating acoustics is the search for the optimum among many compromises. Each speaker option solves its own problems and becomes a tool in the hands of marketing: a successful combination of speakers in the speaker system, beautiful (correct) frequency separation, bulging bass, clattering tweeter, unique design, use of precious wood in the case, or just a well-known brand. All together or separately is designed to convince the buyer of the correct choice. The older Tannoy acoustics (Westminster and Canterbury) interested me in appearance, and it is built on just one speaker. Sound from one point! The old, well-known company, which retains its leading position to this day, has its admirers. I soon learned that the Tannoy acoustics are still two-way, but the bass / midrange and tweeters are coaxial. In engineering terms, this solution turned out to be very attractive. Great solution. In the same network, I read the praise of some and the disappointment of other owners of this acoustics after moving it from the salon to my home. I recalled that I myself appreciated the sound of Tannoy a few years ago in the listening room of a store. Then I liked the Cornwall version of the American Klipsch more. And another understanding came - good acoustics do not always sound good (on different musical material and in different rooms), and this fact had to be somehow taken into account when designing your own speakers. For example, Tannoy is equipped with two knobs for adjusting the midrange and treble.

Given the need to accept compromises, the intention arose to create something like Tannoy Westminster or Canterbury. It turned out that at "affordable" prices in China, you can order complete copies of the Canterbury speakers. They even offer their speakers. There were no reviews about the quality of the system and sound. Decided not to risk it. After analyzing the accumulated information, I began to search for the design of Tannoy acoustics. I found something for the Westminster speakers, and in one Polish chat - 150 photos of the process of making a copy of this acoustics. The decision to repeat almost happened. Stopped scheduling the installation site. Still, Westminsters are built for the big space. Of course, you can install them in the room of an ordinary apartment, but the discrepancy between the dimensions of the living space and two huge speakers catches your eye. I have a private house and some free space is available for accommodation. However, this option (with a creak) was rejected from implementation. Because of the dimensions and, because of the inaccessibility of the native Tanno speakers (as well as their high cost). In addition, the design will be largely at random (exact drawings are not available). Expect high quality sound, in this case, it is not necessary. I wanted to have a controlled process. The study of the issue continued, and the coaxial tannoevsky speaker did not give rest. Frankly, I continued to look for reasonable opportunities to purchase Tannoev heads until I came across the Spanish Beyma. This manufacturer offers the design of a coaxial two-way speaker that interested me. Here is a photo of a coaxially installed tweeter in the center of the woofer.

Bandwidth performance was not as "smart" as the Tannoy. But, I remember, when, in my youth, friends and I connected different heads to the sound frequency generator, we were surprised at the limited range of audible frequencies. The low-frequency effect was especially interesting: significant movements of the speaker cone are visually observed, and at the same time, there is practically no sound. Therefore, having doubted as it should, I chose the speaker 15XA38Nd of the Spanish Beyma with a neodymium magnet. Of course, I was embarrassed by the lack of traces of the use of this speaker for home acoustics on the network: both on Russian and on Western resources. I was confused by the power rating of the speaker: 350 W for low frequencies and plus 90 W for high frequencies. Settled head size 15 inches. The lines read by someone on the net remained in my head: “... the transfer of the grandiose nature of the sound of a concert scale is achieved by heads of 12 inches and above.” With this statement, I agreed in my heart. Yes, and the parameters of Westminster and Canterbury confirmed the correctness of this phrase. It was also clear that the dimensions of acoustics with these heads would be significant. But the characteristics of the speakers, their declared sensitivity of -99 dB, pushed the last doubts. The decision to take the risk was made. For those who are interested, you can find the characteristics of the head on the net or Audiomania.

Speakers ordered, had to wait almost three months for delivery. At this time, the issue of acoustic design returned again. Without digression, I will say that the material “Rogozhin's Labyrinth” seriously helped to approve my choice. It can be easily found on the web. I do not provide a link, since the author asks for prior approval (although the material is available for free). But there, thanks to Rogozhin, both justifications and practical recommendations are given. I would venture to make a statement: this is the only material without water, to the point, with a full set of recommendations for a practical outcome. Hence its popularity.

After this stage, the ordeal with the decision was left behind. Ahead were the pleasant hardships of night acoustic calculations and the design of the speaker cabinet.

A little "around and around"

All of the above, conditionally briefly represents the path traveled. I described it for those who are interested in creating a high-quality speaker system with their own hands, who are faced with similar issues. This describes the process of developing speakers from scratch, and the path was completed all the way to the creation of a prototype. Anyone who wishes can also go all the way, more consciously. Someone will be able to cut corners on it.

A few words about Rogozhin's labyrinth. The attractiveness of this design lies not only in the ability to obtain excellent acoustic results (I say this already with understanding), but also opens up the possibility of designing the exterior and internal architecture in the widest possible range. Ultimately, this technology allows you to create speakers "for yourself." Such an indoshiv. It is extremely convenient and attractive. Probably, everyone understands the difference between a purchased ready-made cabinet and a built-in or shaped according to specific requirements. Functionality, adaptability of the second option is higher. If we take into account the possibility of creating an appearance according to your requirements, linking the appearance of the speakers, color with the interior in the placement area, the value of the option further increases.

Frankly, the understanding of the purpose in acoustic calculations according to Rogozhin's recommendations should be clear. At the first stage, this is achieved by following the instructions given in the material and, already at the second stage, ... by gaining experience. In order to achieve the desired result, I had to perform a lot of acoustic calculations to obtain optimums and build six experimental options in order to reach the seventh - final. By comparing the result obtained in material and sound, you can clarify the calculations performed and make the right choice of option, fitting it to your preferences, providing excellent sounding speakers.

For those who are not tired

Quite a practical side. So, the choice of dynamic heads is behind, the choice of construct (maze channel) too. On the recommendation of Rogozhin, I installed the Hornresp program from an Australian developer. After following the step-by-step instructions, I got the first result. I will say this, almost blindly, I had to perform at least a hundred calculations to meet all the requirements. What you need to strive for - instructions are given by Rogozhin. Next, I share my own experience.

First of all, a photo of the attempts made to find the desired sound:

Here are five enclosure options for one type of speaker. All options, except for the last one (this is the sixth option, obtained by altering the fifth), are made in the amount of 1520 mm in height (the height of the plywood sheet). The width and depth of the hulls are different and depend on the design section of the channel. The internal architecture is also different. The first option (the right body in the first photo) is made of 15 mm plywood. Hull weight - about 70 kg (without finishing). All subsequent ones are 12 mm plywood and weigh from 35 to 55 kg. Light vibrations of minor surface areas on 12 mm thick acoustic cabinets are present at a supplied power of 100 watts. To be honest, the developed sound pressure at such a power in a limited space cannot be sustained for a long time. It's good that there are no neighbors behind the wall.

Thus, at a comfortable volume level, vibrations of the case and overtones are not noted. By the way, no overtones were noted at any volume level.

It was noticed that the volume of the third mode quenching chamber (KHTM is my term), which is located in the zone of the S1-S2 channel, directly affects the quality of the quenching of this mode. We decrease the volume of the KGTM while maintaining the length of the channel section, the mode amplitude increases (in the figure above, its burst corresponds to a frequency slightly above 100 Hz), and vice versa, with an increase in the volume of the KGTM, the mode burst decreases. The change in the volume of KGTM was performed by changing the cross-sectional area S1.

Crossover Debugging

The approaches and features of creating the acoustic design of speakers have been described above. It should be noted that the dimensions and weight of the speakers are impressive, the power of the speaker used is high. When speaker systems were conceived, there was a belief that they needed to be listened to with an input power of 0.5 watts. This circumstance was one of the limitations when choosing a speaker. There was doubt that a powerful speaker would provide efficient operation with low power input. Despite the available headroom, built speaker prototypes perform this function, providing great sound with minimal power input. And, without detracting from the grandeur of the sound.

Currently, the received speakers are connected to a Sony amplifier, in which the volume level is calibrated in decibels. Late in the evening, when there are no extraneous sounds, the acoustics sound great and bright at a volume of minus 66 dB. I also note that the power reserve of the speakers guarantees the operation of the speakers with minimal linear distortion at any volume at a comfortable level.

So, debugging the sound in the crossover.

Initially received a set of speakers and ordered from the manufacturer (Beyma, Spain) FD-2XA crossovers for these particular speakers disappointed me. The first inclusion at low volume led to complete bewilderment. The sound was just terrible. At low volume, the bass was almost non-existent. As the volume increased, they turned into something completely absurd, emitting an incredible muttering. There was no music as such.

After a 3-4 hour run at high volume (70-90 W), the speakers started working (warmed up). However, the dissatisfaction with the sound did not disappear. Neither sincerity, nor grandiosity of basses, nor desired emotions. Only commendable sound detail.

As I mentioned earlier, sound development was carried out in two directions: the search for the optimal parameters of the labyrinth and work with the crossover. The developments in the labyrinth are given above. Crossover also taught its lessons. His scheme was found on the Internet. It was a first-order filter with a matching circuit for the input impedance of the low-frequency loudspeaker. The crossover frequency, according to the Beyma website, is 1800 Hz.

Of course, I could describe in detail all the searches and turns of the settings of the obtained filters, but something tells me that such a presentation would be boring and uninformative. I'll put it in the thesis.

1. It turned out that after turning off the capacitance of 15 microfarads, bass reproduction became more pleasant.
2. Tests have shown that on some musical compositions acoustics gives audible distortion. It was possible to establish that the distortion is introduced by the HF part of the speaker. Distortion disappears when the high-pass filter cutoff frequency is shifted to 2500 Hz and above.
3. To reduce the brightness, one might even say, the "clamor" of the speakers in the midrange range, instead of a capacitance of 2.2 microfarads, it is better to use a capacitance of 0.68 microfarads.

After such changes, the sound became very good, but still, not quite satisfied. An attempt to leave the woofer without inductance L1 did not further improve the sound of the speakers. Nevertheless, the uneven frequency response of the speaker needs to be compensated. The manufacturer's inductance is kept in place. Her influence is well felt.

And so, after a long listening to various genres, after trying to vary the values ​​​​of the remaining filter elements right during listening, “on the go”, so to speak, turned off the RC matching chain (8.2 ohms and 8.25 microfarads - indicated in the diagram). There was an amazing effect. Feeling the sigh of a speaker who has gained freedom, previously held by a kind of noose. The previously held sound escaped, flew, became light and noble. It is impossible to convey in words the newfound lightness and virtuosity of the renewed sound. Exactly the sound appeared, from which an internal response arises, chills go through the body, and pouring music fills all the cells of the brain.

It should also be noted that the inductors of the Beyma crossover are not serious. They are wound with 1mm copper wire. For the woofer, the inductance parameters are 1 ohm and 1.44 mH. At high power, the loss of bass energy is guaranteed. Taking into account the parameters of the low-pass filter inductance obtained by measurement, I ordered inductors for low-frequency and capacitances for high-frequency links of a higher class.

Total:

The work done made it possible to adapt the parameters of the resonant channel to the selected speaker and ensured the sound of the speakers was not lower than the expectations drawn by consciousness. I'll write about the sound below. All work took about five months (weekends and evenings, taking into account the presence of a fuse, time for listening and analysis, for the following calculations, etc.) and required certain costs. I can confidently say that the sound level corresponds to the acoustics of the price range from two million rubles. Actual costs, especially considering the existing equipment, are disproportionately lower. The path traveled was not easy. The created speaker sounded not only due to the accurate or successful calculation of the resonant channel, intuitively, to some extent, the selected speaker, its approach to modeling and manufacturing of the cabinet. Let me remind you that the built speaker system is two-way, the presence of a crossover is mandatory. Working with the crossover also allowed me to contribute to the final sound and gain a rewarding experience. Damping was not used in the speaker design. Perhaps I will try to evaluate the effect of damping in a particular case. I can say that the accumulated experience made it possible to evaluate the two variants of speakers for the 75GDSh3-1 speakers mentioned at the beginning, to see the shortcomings of the bass tuning and make adjustments.

There is no ready-made front speaker option for the 15XA38Nd speaker yet. There is a project. A new calculation of speakers with a 75GDSH3-1 speaker with increased bass response has been performed. The new variant will be equipped with a tweeter. Given the current workload and the delivery of additionally ordered components, these projects will be implemented no earlier than October-November of this year. The results will be presented. Part of the speaker cabinet design for the 15XA38Nd head is shown below:

Sound

It is possible that I have developed sentimentality. The achieved sound of two-way speakers on one or the other tracks led to spiritual and heart trembling, to breath locking, provoked to re-listening to favorite compositions. Right or wrong sound - I do not discuss. If the sounding speaker evokes in the listener the conviction of reality from the audible music, vocals, sounds and overtones, the goal has already been achieved. If individual turns of the musical program can dry the throat, make the eyes moist - the task is completed to the maximum. I am inclined to believe that the built prototypes of future speakers are close to the coveted maximum.

To be frank, without getting such a result, I would not allow myself to openly share my achievements. Perhaps, someone will say, beginners are lucky. I got double luck. Two pairs of excellent speakers based on 75GDSh3-1 speakers, released in the Soviet era, which have extended 35 years of stage life and a pair of new ones, based on 15XA38Nd speakers from the Spanish Beyma. Let it be lucky, but for those who consider it possible to make such speakers, given the additional recommendations provided in the material, the result is guaranteed. It is for such people that I write.

Making loudspeakers based on branded speakers may seem like a fairly simple job at first glance. However, in reality, making columns on your own is not so simple, as it might seem at first glance.

Do-it-yourself acoustics from scratch

In this article on ours, we will tell you how to properly make acoustics with your own hands based on branded speakers. The crossover is made on metal film
capacitors and resistors from Jantzen Audio.

Inductors, metal film capacitors and resistors are located on the printed circuit board. For the manufacture of acoustic boxes, we used plywood with a thickness of 18 millimeters. The total volume of the box for acoustics was 13 liters, and the weight of the manufactured speaker was 6 kilograms.

The calculation of the volume and dimensions of the speakers was carried out using the BassBox 6 Pro program. Crossovers were calculated using the X over 3 Pro plugin. We recommend using Titebond Original Wood Glue. The bass-reflex tube was used by Intertechnik BR SL 45. The acoustics were sheathed with a special black Audiomania 101-14 fabric.

Crossover circuit

Production of an acoustic enclosure

All required dimensions were obtained using a special utility. You can cut plywood according to the drawing both independently and entrust this work to experienced professionals. In the latter case, you will get the highest quality work, which will provide a spectacular appearance of the structure.

The walls are glued in stages using special wood glue. To increase the strength of the structure, window glazing beads can be used, which in this case are actually stiffeners. It is necessary to glue the plywood from the inside with batting, which is pre-cut to the original dimensions. Thus, you will improve the acoustic performance of the device case.

In the event that you did the cutting yourself, you need to go through the joints with a milling machine and carefully grind the joints, rounding the edges. After the box is ready, it can be pasted over with a decorative film that imitates the structure of wood or black acoustic fabric can be used. In this case, the choice is entirely yours.

We mount the crossover

As a rule, testing a crossover for acoustics takes about several weeks. During the tests, you need to choose the optimal sound, after which you can proceed to the final installation work. Crossover boards are glued with silicone sealant or silicone-based glue.

After the sealant has hardened, you can begin to solder the radioelements. When doing this work, do not spare solder. The work must be done with the highest quality possible. Having assembled the crossovers, we fix them in the column body. All you have to do is connect the crossover speakers with a special speaker cable.

We fix the speakers with self-tapping screws in the case and carefully seal the junction to ensure the maximum possible tightness of the internal capacity of the column. The sound quality of self-made speakers based on Visaton speakers is at the highest level. In terms of quality, they are not inferior to ready-made branded speakers from well-known brands, and at the same time, the cost of their manufacture is much lower.

Now on sale (at least in large cities) you can buy the most diverse in terms of power, design, overall dimensions and cost of acoustic systems for almost every taste, ranging from small-sized volumes of 2 ... 3 dm 3 to floor-standing volumes of more than a cubic meter. However, the vast majority of these systems have one common feature: they are all closed box type.

This means that the acoustic design is tightly closed and the loudspeaker cone works like a piston, the cylinder of which has a constant volume of enclosed air inside.

The acoustic design of a closed box has a number of indisputable advantages, among which the most important are the following:

1. Acoustic short circuit between the front and rear sides of the loudspeaker cone is completely eliminated, which increases the relative (but not absolute!) response at extreme low frequencies and, therefore, reduces the overall frequency response unevenness due to this part of the spectrum
2. Due to the fact that the diffuser works like a piston in a closed cylinder, the resistance of the internal volume of air in the case increases sharply, which leads to a rapid damping of the free oscillations of the diffuser, and this is equivalent to an increase in the damping factor.
3. Due to the increase in low-frequency radiation (see point 1), it is possible to significantly reduce the overall dimensions of the case while maintaining sound quality in the bass register.

However, as they say, only cheese in a mousetrap is free. Everything else has to be paid for. In the case of compression loudspeakers, the trade-off is their efficiency and, therefore, the electrical power that must be supplied to the system in order to obtain sufficient sound volume.

Readers probably paid attention to the fact that most modern portable and compact receivers, radio tape recorders, as well as their car twins, have a passport output power of 50, 60, 100 and even 300 W! Meanwhile, the vast majority of old tube radios and radios, even of the highest class, had an output power 10 ... 20 times less. For example, the highest-class console stereo radio "Symphony" had an output power of each channel that did not exceed 6 W, first-class desktop receivers "Latvia", "Mir", "T-689" had an output power of 5 W, although the volume of their sound was by no means less , but rather more than today's car radio with a nameplate power of 2x30 watts.

What's the matter? But the fact is that before the widespread use of transistor radio equipment, not compression, but exclusively open radiators were used as acoustic systems, i.e. those in which the rear side of the speaker cones communicated with the air volume of the room through the perforated back wall of the case. Although these open loudspeakers did not have the advantages of compression systems, they nevertheless provided excellent sound quality with much less electrical power input.

A comparison of the two types of speaker systems is provided so that the radio amateur can make the right choice. The fact is that today's nomenclature of powerful terminal transistors makes it possible to obtain undistorted output power of 50 and 100 W with exceptionally high efficiency, since special circuit solutions allow these transistors to operate in class B with virtually no noticeable non-linear distortion. In this case, the use of compression acoustic systems is not only possible, but also quite justified.

The situation is different with tube amplifiers. Modern tube end stages can only work in pure class A.

This is necessary to ensure an acceptable level of non-linear distortion. But this, as you know, is the most uneconomical mode. In addition, powerful terminal lamps consume a large current through the filament circuit, so it turns out that even with an output power of 10 ... 15 W, the amplifier consumes more than 100 W from the network.

It is clear that it is simply pointless to create a tube amplifier with an output power of 100 W or more for the normal buildup of a sufficiently powerful compression system: it will consume at least 1 kW from the network and, accordingly, generate heat on a par with an iron or electric stove.

It follows that an open-type speaker system is preferable for a tube amplifier. But such systems today are not produced by almost any company either in Russia or abroad. What is left for the reader to do? It remains for him to build such a system himself.

For those who have never done this, we inform you that it is not at all as easy as it may seem at first, and that building a high-quality loudspeaker system is no easier than building a high-quality amplifier. Therefore, we will give not only a detailed description of one of the systems (far from the most complex), but also accompany it with explanations and comments that will help you competently approach the choice of loudspeaker types, determine the shape and dimensions of the case and structural materials for its manufacture.

You should start designing an acoustic system by setting the basic parameters. The main indicators of any speaker system are:

1. Really reproducible frequency range for sound pressure.
2. The unevenness of the frequency response in this range.
3. Real value of sound pressure.
4. The coefficient of non-linear distortion.
5. Power consumption of the audio signal.

These parameters are directly related to the choice of types and number of loudspeakers that can solve this problem. Here again a small digression into the field of theory is required, without which much of the further reasoning may turn out to be incomprehensible. Let's start by looking at how a loudspeaker works. For effective radiation of the lowest frequencies, the loudspeaker cone must have the maximum possible radiating surface (cone area), extremely soft suspension (elastic corrugation and low elasticity of the suspension), which entails a sufficiently large inertia of the entire system. However, at the lower frequencies of the range, this practically does not negatively affect the sound quality of bass instruments.

To effectively reproduce the higher frequencies of the range (starting from 8 ... 10 kHz), the requirements for the loudspeaker are reversed. The diffuser can be small, but necessarily rigid: very often, to achieve this goal, a paper diffuser is impregnated with bakelite varnish, and for the most expensive models (mainly Western firms) they are made of plastic or light duralumin. The suspension of the coil is made rigid and as inertialess as possible.

Even what has been said is enough to understand that one loudspeaker is indispensable for effective radiation of a wide spectrum of frequencies. Indeed, the vast majority of broadband speaker systems consist of three or more different drivers.

Why three and not two? Because a good low-frequency loudspeaker with a low frequency of its own mechanical resonance effectively radiates only frequencies no higher than 4 ... 6 kHz, and high-frequency heads start working from 8 ...

In order to fill this area, the system usually includes a third, broadband loudspeaker of medium power (3 ... 5 W), to a relatively large cone of which a small rigid cone is glued to improve high-frequency radiation. In this case, it is possible to achieve a frequency band for such loudspeakers in the range from 60...80 Hz to 10...12 kHz with an acceptable degree of unevenness.

1. 6GD-2 RRZ - as the main low-frequency one (frequency band 40 ... 5000 Hz, natural resonance frequency 25 ... 35 Hz, rated power 6 W, impedance 8 Ohm). It was used in the top-class stereoradiol "Symphony".
2. 4GD-7 - as a mid-frequency "fill" (frequency band 80 ... 12000 Hz, natural resonance frequency 50 ... 70 Hz, rated power 4 W, impedance 4.5 Ohm).
3. 1GD-3 RRZ - as a high-frequency (frequency band 5000 ... 18000 Hz, natural resonance frequency 4500 Hz, rated power 1 W, impedance (at a frequency of 10 kHz) 12.5 Ohm.

It is likely that it is impossible to purchase these particular loudspeakers today. There is nothing to worry about, since the types available for sale are not only not worse than those indicated, but often surpass them in basic indicators. It is important only when choosing them. Adhere to the given ratios of nominal powers (6:4:1) and, if possible, the ratios of impedances. It goes without saying that the power rating of replacement loudspeakers cannot be less than those recommended.

Well, for those who do not intend to engage in independent calculations and design, we will give a detailed description of the simplest, but nevertheless quite meeting the requirements of Hi-Fi acoustic stereo system, consisting of two identical 10-watt speakers - providing sound with a large margin of room area up to 50 m and specially designed for the previously described stereo amplifier 2x8 (10) W.

So let's start with the case. For its manufacture, you will need good, defect-free (preferably aviation) plywood 10 ... sheet rubber (you can use old car tubes), as well as 20 special shipping pads made of loose cardboard used in the packaging and transportation of chicken eggs, and good carpentry or casein glue.

In addition, you will need special joinery and carpentry tools for woodworking (longitudinal sawing of a thick board, sawing plywood, planing, cutting holes for loudspeakers in the front board and perforations on the back walls), as well as wide clamps or clamps for making a glued front shield.

The figures show drawings of individual parts of the case and its general view, indicating the main dimensions. As for the number, shape and size of the holes in the front shield, they will be determined solely by the overall dimensions of the loudspeakers used by the radio amateur and their number. The dimensions shown in the figure correspond to loudspeakers of the 6GD-2 RRZ (low-frequency), 4GD-7 (mid-frequency) and 1GD-3 RRZ (high-frequency) types.

It should be noted that when using loudspeakers of any other types, their relative position and the coordinates of the centers on the front shield must be kept as indicated in the drawing. If two identical ones are used instead of one high-frequency loudspeaker, they must be placed side by side, horizontally and symmetrically with respect to the coordinates indicated on the drawing for 1GD-3. They must be connected to each other in series and in phase.

Work should begin with the most difficult and time-consuming part of it - the manufacture of the front shield. This shield is assembled from individual spruce or pine bars, cut from a single, well-dried, unwarped board with a thickness of at least 30 mm (in planed form). The board is sawn lengthwise into separate bars with a section of 30x30 mm and a length of 1.1 m (with a technological margin). After carefully processing the bars with coarse sandpaper, they are glued with a board of the required width (with a small margin) using carpentry or casein glue, and, clamping it in clamps or clamps, leave it to dry for at least a week.

At this time, you can start making cases. For them, two side, top and bottom panels are cut out of 10 mm plywood, wooden corners are harvested, and acoustic design is assembled using glue and screws. During the assembly process, it is important to maintain the rectangularity of the structure. This is necessary so that in the future the front board will fall into place without distortions.

You can trim the case with valuable veneer (walnut, Karelian birch) or paste over with a self-adhesive film "wood-like". Exterior finishing must be completely finished before final assembly of the unit.

Now we need to make the back walls. They are cut from 4mm plywood to exactly fit the back window of the acoustic design.

Then you need to take three shipping tablets from the eggs and put them on the table with the "loose" side of the cardboard down. With a sharp knife or hacksaw blade, you need to cut flush all the "smooth" cones protruding from above, then put all three tablets with the cut side on the back wall and mark the future holes in the back wall through the holes formed in the tablet with a pencil.

After all the marked holes are cut out in the plywood, the back wall must be painted with stain or other water-soluble paint, gauze is glued on the inside over the entire area and, after it has completely dried, the prepared plates are glued on top of the gauze, making sure that the holes in them are precisely positioned against the holes in the back wall. On this, you can consider the manufacture of the rear walls finished and return to the front panel.

If the front panel is well dried and the glue "tightly" connected the individual bars into a whole board, you need to carefully and with a high degree of accuracy cut it to the desired size. Such a size is considered necessary so that after sticking sealing rubber strips-belts on all four end sides of the board, the board fits tightly and without gaps inside the case from the front side. Fastening the board to the case can be solved in different ways. In the author's designs, mounting brackets-angles with washers and "lambs" from mounting the kinescope to the TV case were used.

When the front board is precisely fitted to the design opening and pasted over with rubber strips at the ends, you can start cutting holes for the speakers. In this case, it should be taken into account that the diameter of the hole in the board, to the nearest millimeter, must correspond to the distance between the inner edges of the cardboard sticker on the loudspeaker from the diffuser side.

After cutting all the holes, the inner end sides of the holes must be carefully sanded with sandpaper, wiped from the resulting dust and covered with any varnish or nitro paint. Now, on the outer side of the board, you need to stick or stretch radio fabric or any other, but always rare (transparent) matter with the help of small carnations. Only then can loudspeakers be installed on the front panel, while ensuring their absolutely precise centering relative to the holes in the board.

The remaining six "egg" tablets (for each of the cases) must be nailed or glued to the inner sides of the side walls of the case (three for each wall) with a "loose" layer of cardboard inside the case. This makes it possible to almost completely eliminate reflections from the side and rear walls of the case and significantly reduce peaks and dips in the frequency response of the unit in terms of sound pressure.

The loudspeakers are connected to each other in accordance with the diagram shown in fig.

The parameters of the parts indicated in this diagram correspond to the types of loudspeakers used.

Consider the phasing of the loudspeakers inside the speakers and the speakers among themselves. This is an extremely important matter, because with incorrect phasing, even a perfectly assembled system will work very badly. Unfortunately, many radio amateurs do not know this or do not attach importance to this, paying for the poor performance of good speakers.

The physical meaning of phasing is that in a group of parallel, series or mixed-connected loudspeakers operating from a common two-wire line, when a DC voltage of positive or negative polarity is applied to the input of the line, the diffusers of all loudspeakers react in the same way: either they are drawn into the magnetic gap, or they are pushed out of him. It is unacceptable for the cones of different loudspeakers to move in opposite directions.

In practice, things are a little more complicated. The fact is that the high-frequency loudspeaker is connected to the line through an isolation capacitor, and the mid-frequency loudspeaker is shunted by a choke, so when a battery (1.5 V) is connected to the line, you can simply not notice the deflection of the diffuser. So for the time of checking the common mode, the isolation capacitor must be short-circuited with a jumper, and the inductor must be unsoldered on one side (any). To change the phasing of any loudspeaker, you need to swap the wires suitable for it, and after finishing work, do not forget to restore the temporarily broken circuit.

After all the loudspeakers inside each of the speakers are in phase, the speakers should be phased with each other. To do this, both speakers must be placed close to each other at a distance of 2 ... 3 m from the operator "facing" to him, turned on in parallel and a signal from a sound generator with a frequency of 200 Hz of a very low level should be given, so that the sound was barely audible . One wire from one of the speakers (any) must be broken and a long piece of connecting wire must be included in the resulting gap so that the operator, being at a distance of 3 m from the speakers, can alternately close and open the broken circuit.

If, when the broken circuit is closed, the volume hardly changes or increases very slightly, then the speakers are phased correctly. If, when connecting a second, open speaker, the sound volume decreases sharply or the sound ceases to be heard at all, then the speakers are turned on in antiphase. In this case, the wires from one of them (it doesn’t matter which one) must be swapped and once again make sure that the speakers work in phase.

After that, the same-name ends of the wires of both speakers must be marked (painted over with paint, wrapped with electrical tape, put on a vinyl chloride "stocking"), so that later they can be properly soldered to connectors or other connectors that exclude non-phase connection of two speakers to the outputs of stereo amplifier channels. It is useful to check for common mode again with the amplifier running, since it may turn out that the secondary windings of the output transformers in the two channels of the amplifier have different phases at the output. With such a test, a signal with a frequency of 200 Hz from the generator must be simultaneously applied to both inputs of the amplifier.

And finally, a final note about columns. Since the current at peak power (10 ... 12 W) exceeds 3 A, the connecting wires must have a sufficient cross section so that there is no noticeable signal voltage drop on them with a length of 3 ... 5 m. It is best to use a standard lighting cord from household electrical appliances as connecting wires for speakers. The wires must be solid, connections in them are unacceptable.

Before using the speaker system, you need to check each of them for the absence of rattling. To do this, a sound generator is connected to the input of the amplifier, the signal level is set to correspond to the nominal power of the speaker system (in our case, 10 W) and the frequency is changed very slowly within the entire band, from 40 Hz to 18 kHz, maintaining the output power unchanged and carefully listening to the appearance of extraneous overtones and rattles.

Most often, they are caused by loose washers under screws and screws, a loosely screwed back wall, sound-absorbing plates that are not securely glued, radio fabric or shavings, sawdust and small foreign objects that are between the diffuser and radio fabric, loosely stretched on the front panel. All identified causes must be eliminated before the speaker system is put into operation.

And if you were not too lazy and did everything that was recommended, the author guarantees you great sounding that the owners of 50 and 100-watt compression speakers will envy.