Hello to all DIYers! Once passing by the construction of an apartment building, I saw gas workers laying a plastic gas pipe d-225 mm. The idea came to make acoustic systems with it. I asked the builders, they cut me 2 pieces with bevels 70 cm long.
I cut out circles (bottom of the speaker) d-225 mm from chipboard, screwed them with black self-tapping screws (8 pcs), on glue.
From 10 mm of plywood, I cut ovals for speakers, and also fixed them on self-tapping screws.
On the back side of the case of the future speaker system, I drilled holes under the clamped for the wires.
I putty the places where I screwed the screws, cleaned the places of the putty and the pipe itself with sandpaper, degreased everything with acetone and began to glue the fabric.
Carpet is glued "Moment" in small areas with a stretch around the circumference. After gluing the inside of the pipe, I missed the joints with a sealant. I soldered the wires to the connector to the case, and on the other side to the speaker.
The speaker was also fixed to the plywood with self-tapping screws, and the mesh was fixed.
That's it - some decent compact home speakers are ready. Of course, this is not a branded JBL, but it plays well with a good amplifier.
Video - homemade speakers from car speakers
By varying the diameter and length of the body, you can achieve a different sound character. Since all these calculations are initially difficult to carry out - just take a little more to maximize the bass. Bye everyone! I was with you Alexey Ivchenko Novorossiysk.
Discuss the article HOW TO MAKE A COLUMN OUT OF A SPEAKER
Greetings to the readers of Datagora! I want to tell you about the creation of a speaker system using 3D printing technology. With the help of a 3D printer, I was able to build an unusual speaker system in the shape of a ball, as well as solve a number of additional problems arising in the manufacture of acoustics.
I want to note that I do not at all advocate the use of plastic as the main material for building speakers.
Ever since my student days, I had a dream - to make speakers in the form of balls. But the methods available at that time for me to create a non-standard shape case did not inspire me in any way. And now, many years later, I got a 3D printer.
Now here is my translation of Troels Gravesen's article about "the world's worst dome sounder Philips AD 0160". I think the Soviet, and many modern tweeters he did not come across.
Most likely, few people have this particular tweeter (tweeter, not to be confused with Twitter), but Troels' research will be useful to home-builders to assess the quality and proper use of tweeters.
Best regards, Sergei
I'll show you with a real example what you can do with old speakers, namely their speakers, to get better sound.
Good afternoon, lovers of good sound! Today I will introduce you to Fedor Gartsuev and his very interesting project Suono. An interesting step-by-step production of acoustics with your own hands, as a result, we got very high-class acoustic systems!
The idea to create something unusual that no one else would have, my brother and I arose a long time ago. Love for true music left no doubt that these would be hand-made acoustic systems. While studying at the university, there were even test versions in the form of two-way "poles" based on speakers from and a Chinese "tweeter". Then invaluable experience in working with wood was gained, an understanding of what could be done and what would have to tinker arose, there was a need to buy a tool. We are well aware of the importance of carefully calculating all the acoustics and sound settings. At that moment we could not afford any of this, so the implementation of our plans was postponed indefinitely ...
And last summer, there was free time, we decided to implement our plans, to make acoustics with our own hands. We started working on the project. I didn’t want to make standard parallelepipeds, there was an idea to “rip off” some eminent brand. I really liked Sonus Faber Stradivari, Aida, Jamo Epicon 8, but in each of them something did not suit me, then my brother (later, they nevertheless found very interesting solutions). We went through a lot of options (see the picture), and in the end we came to a project that suited both of them (later it was tweaked for the speakers we bought).
After reading the literature and thematic sites, analyzing the design of Hi-End class acoustics, as well as being guided by logic, also came to the conclusion with our own intuition: the design of the cabinets must meet the following requirements:
1. Prevent the generation of standing waves inside the speaker. 
2. Do not create sound distortions caused by resonances and re-reflection of sound waves in acoustics.
To ensure the first condition, the back panel was made narrow, the absence of parallel surfaces also contributes to this, and at the same time creates the effect of "infinite space". But the column needs volume, so the front panel is wide enough. Most firms try to make the speaker as narrow as possible, but acoustics with a wide front panel sound more.
To provide the second condition - the panel was broken at angles of 7.5 and 15 degrees to the radiation plane 
speakers. Concave side surfaces, not a single perpendicular plane both in relation to each other and to the front of wave propagation, all this serves one purpose - to achieve, if not Hi-End, then at least good Hi-Fi. Two phase inverters are installed at the back, however, they serve not for resonant amplification of low frequencies, but to equalize the pressure inside the speaker and are tuned to other frequencies so that they do not "whistle" when the air passes through - they put two on each speaker. The cabinet is installed on four copper spikes, and the stand itself stands on three steel supports with plastic pads, with the ability to adjust the height and angle of inclination, all this is done so that the vibration of the speakers is not transmitted to the supporting surface. Seen from above, the AC 
resembles a Soviet mouthpiece. Bulkheads are installed inside for rigidity and giving the side surfaces the desired bending radius. The edges of the front and rear panels have been rounded off. It was also planned to glue the sides with veneer for aesthetics.
The work began with the selection of speakers. Break a bunch of sites, settled on Polish speakers Alphard... We found their representative office in Minsk, from which everything you need was purchased, in addition, it turned out that the company is engaged in the manufacture of professional speakers and can provide assistance in the project. Looking ahead, I will say that they were entrusted with the calculation and manufacture of crossovers, as well as the final fine-tuning of the sound, which saved a lot of time and money. And themselves on the buildings.
Two sheets of plywood with a thickness of 18 mm and 9 meters of a bar of 95 × 35 mm were purchased. The plywood was lined, cut into the required parts. Straight lines were cut with a circular saw according to the rule, and curved lines were cut with a milling cutter (along the way, a compass was made for a milling cutter with the ability to set a radius from 300 to 1500 mm). I will make a reservation right away: cutting 18 mm plywood with a router is a bad idea, it is better to cut the workpiece with an electric jigsaw with an indentation of 2-3 mm and finish the shape with a router, the surface will be cleaner. The intricate details were printed on a Whatman paper at a 1: 1 scale and made something like templates. For manufacturing 
details took about a month, unfortunately, this process was not photographed. After processing all the parts, they were assembled: 
They collected everything with the help of corners, screws and wood glue. 
In the photo above, the holes for the speakers, bass reflexes and speaker terminals have already been cut. To extinguish any possible resonances and overtones, it was decided to lay out the inner surfaces with batting: cut with a knife on paper, secured with a stapler. Immediately, in the lower cavity, they were installed. 
After much mockery of 18 mm plywood, it was not possible to bend it to the desired radius. Therefore, it was decided to select the thickness of the side panels from three layers of plywood thinner. Each layer was screwed to the spacers with self-tapping screws and coated with wood glue to glue them together. The joints of all panels were lubricated with sealant from the inside. The gap between the panels in the photo is not shoddy build quality. The screws had to be loosened, otherwise the side panels would not fit. Top caps by rolling a bypass cutter directly over the column. 
Final fitting and assembly of some elements: 
After the main part of the bodies was assembled, they began to sand, putty, sand again ... and so on until smooth, even surfaces were obtained. It took us two jars of putty and a set of grinding wheels. There was a lot of dust. 
After everything was sanded, they started pasting the columns with veneer. The main color of the speakers is gloss black, the contrasting patterns from the veneer were intended to dilute this "blackness" and give a more aesthetic look. The experienced eye will immediately recognize the Jamo Epicon 8... The veneer was cut according to patterns from Whatman paper, with a knife on paper. If the veneer is thick (we had a thickness of 0.6 mm), then you do not need to try to cut it off at once to the full depth - it’s too big that it will burst.
This is not described in the instructions for the glue that was bought with the veneer, but from my experience I will say: it is better to apply the glue to the surface, not to the veneer, and let it stand for three minutes. It is better to protect the surfaces around the pasting area with masking tape - the glue "warps" the plywood - these places will then have to be sanded, and the paint does not want to stick in these places at all.
While the glue dries, it is advisable to periodically roll the veneer with a roller, since it gets soaked from the glue, air cavities form under it, if they are not removed immediately, then it will be very problematic to eliminate them.
After the glue has dried, the veneer can be sanded. On the left before grinding, on the right after. It doesn't look very nice right away, but after applying varnish or stain, everything changes.
In the absence of another room, they painted on the balcony. Before painting, the balcony was thoroughly washed and covered with cellophane to prevent dust from entering the painting area. The housings were “vacuumed” and wiped with a lint-free cloth (sold in auto dealerships). It is not necessary to wipe with a damp cloth - the veneer is very afraid of liquids, it begins to exfoliate. To prevent paint from getting on the veneer, it was covered with masking tape. Since the surfaces are large, it is better to glue the tape only along the edges, and fill the sheets of paper cut in shape under it.
Acrylic was chosen as paint and applied.
The first layer will reveal all the imperfections in the wood (scratches, dimples, gaps) that were allowed during sanding. Everything that has manifested itself is cleaned, putty, polished.
After that, several more layers of paint are applied. After the paint has dried, the masking tape is removed, probably this was the most pleasant moment in all four months. There was an idea to cover the veneer with a mahogany stain, but it looked gloomy on a test board, they decided to leave it as it is.
Coloring the strips (we left 2 mm gaps between the veneer strips), limiting them with masking tape:
We put the name. To do this, we come up with a beautiful word or phrase, we borrowed the name from the Italian language. We put the name on a special film using plotter cutting, such a service is available everywhere and is inexpensive. We glue the film (it is self-adhesive) to the surface and apply paint, we used a car in a spray can.
After the paint has dried, remove the film and get a beautiful inscription:
On the back panel we glue a plate with the characteristics of the speakers; screw on the bottom stand and footrests, there is nothing complicated here, simple mechanical assembly. We cover everything with varnish from the same spray gun. The veneer has acquired a yellowish tint, a gloss has appeared on the paint.
We hammer the bass reflexes, you need to beat more carefully, we broke one after all, we had to buy it in addition b. We solder the acoustic terminals, put them on the sealant and screw them on.
We solder and install the speakers. It is worth noting that on the inside of the speakers along the edge, we glued rubber tubes in order to exclude the "walking" of air through possible slots.
This is the final stage. We put the speakers on the floor; we check the impedance with a multimeter, connect the amplifier ...
First audition... This was the most anticipated and exciting event - the result of four months of work. I won't say that the sound has reached the High-End level (although I don't even know how it should sound), but it did not disappoint either.
Compared with existing Sony SS-F6000... At first the sound seemed to be (the ears got used to a different sound), but after a week of listening it began to seem the only correct one. The sound is more "mature" compared to the "disco-pop" sound of Sony. The bass is not as powerful, but more concentrated, without boominess. Each instrument is in its place, has its own weight, is well distinguishable, does not stick out or hide. Even at maximum volume, the music does not merge into one continuous roar. I can't say anything about it: there is nowhere to measure the characteristics and there is nothing. 
Speakers Alphard WH656, Alphard WH506, Alphard TW-317, woofer, mid and tweeter, respectively.
A few numbers:
- The cost of the speakers is $ 400, of which $ 270 was spent on speakers and crossovers.
- Maximum power 300 watts.
- Impedance 4 ohms.
- The total weight of one column is 38 kg.
Dimensions 1135 × 370 × 315mm
On my own behalf and on behalf of numerous fans of the site "Soundmania" I would like to express and wish great creative success to Fedor Gartsuev!
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Many users are wondering: how to make do-it-yourself computer speakers? And this is not at all surprising, since only work with your own hands will not raise any doubts about the quality of the finished system. To create speakers for a computer yourself at home, you will need skill in handling a soldering iron and an understanding of basic electrical circuits. Yes, even without these skills and knowledge, you can try to create your own invention, but be prepared to face difficulties. If you are interested in making speakers for your computer, we recommend that you familiarize yourself with each stage of creating this useful device. In order to understand the material that follows, you will need basic knowledge of school physics and a little perseverance.
Making a "bun"
Obviously, this popular component won't work without a box. The movement of air within the structure sets the cone in motion, which creates sound volume.
Apparently, you will have to make a closed box with only one hole - for air circulation. Since you're building music hardware on your PC, there is no need for hefty speakers. The best option is factory car acoustics.
Important! This option will not provide you with high air pressure, but it will be quite enough for a room with a computer.
Important! Don't look for obscure LPFs on a large number of amplifiers. A passive filter, which is easily assembled from resistors and capacitors, is quite enough for you.
We make the case
The body will require very strong wood. Well suited for such purposes: chipboard and fiberboard. The thickness of the sheets should not exceed five millimeters, so that the entire structure is lightweight.
Important! If an old TV set in a wooden case is lying around in the garage, then you can use this to create a high-quality box.
Use a jigsaw to cut out all the pieces you need. When creating a case, do not feel sorry for glue, screws and other elements that provide fixation. Also focus on the front part where the speaker will be installed.
Important! To achieve the required rigidity, you should use wood slats, which are triangular in shape. Pay attention to all the small holes and gaps - they definitely need to be glued.
Do not forget to drill a hole for the cable on the "back", and make a connector on the outside in order to connect to the amplifier. It will be extremely convenient if the design does not include any external blocks.
BP
How to make PC speakers? The system must be powered by energy, so a little attention should be paid to the power supply as well.
Important! Do not use ICs for your design that are bi-polarized as it will be extremely difficult to obtain the correct current for optimal performance.
Give preference to the design that requires a unipolar power supply with a voltage in the region of 12-24 V. Such measures in the future will have a positive effect on repairs, because it will be much easier to carry out it in the event of a breakdown.
What else do you need to consider? Pay attention to the following tips:
- The output power of the transformer must be significantly higher than the total power consumption.
- It is best to create one PSU for all components at once.
- For best efficiency, place the power supply and amp filter only for the “loaf”. It is better to mount the ULF near the main speakers and tweeters. Measures like this will help ensure the least amount of wires and the most cost-effectiveness.
Important! Do not forget that the sub is subject to high vibrations, so all soldering should be done very efficiently. All items in the subwoofer must be firmly attached.
Amplifier and power supply
It is better to fill the hole with a good sealant, and only then mount the front panel. Its masters also recommend putting it on a sealant, and after drying - to plant it on self-tapping screws.
After the entire box is completely dry, you need to choose a suitable material and cover it. For a power supply unit, you can use one transformer, a rectifier bridge and about two or three electrolytic capacitors. Such a device will reproduce sound cleanly and not create unnecessary interference.
Important! If you observe a small hum, you should increase the value of the electrolyte capacity. If you cannot find elements with a large capacity, then you can simply stick several components in parallel to each other.
Main columns
Here you can take at least wood or plastic for the case. It is of course best to choose the first material as it will help you achieve the best sound.
Important! If you are too lazy to deal with wood processing, then you can just cheat and take the old devices from the radio and put them unchanged.
As mentioned above, the amplifier and power supply unit will be in the box, so the finished speakers are simply connected to the desired terminals. If you want to do everything in the best possible way, it is recommended to resort to the following algorithm:
- Create two boxes for the main speakers. Use the tips for making the box as a guide.
- Use material to wrap the structure. Such measures will help to achieve good sound.
- Install two speakers in each cabinet.
Acoustic design does not mean the decoration of the speaker with carvings in the antique style, although this will give the speaker uniqueness, but a solution to the problems of acoustic short circuit.
The fact is that when the diffuser moves on one side, excess air pressure is formed, and on the other, the air is discharged. For sound to appear, it is necessary that the vibrations of the air propagate into space and reach the listener, and in this case the air vibrates around the basket of the dynamic head and the sound pressure generated by it is not very high, especially in the low-frequency region:
More details about how the dynamic head works HERE.
The methods of breaking the acoustic circuit are called acoustic design, and each of them is designed to impede the penetration of air from one side of the diffuser to the other.
There are several main options for breaking an acoustic short circuit. The easiest is to use sheet material in the middle of which a hole for the dynamic head is cut. This is called an acoustic screen:
A slightly more complicated way is to open the box, i.e. drawer without back wall:
Both of the above methods have too little efficiency, therefore, they are practically not used only in those cases when "there is no fish and cancer is a fish".
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 slot in the box will give overtones, since a sufficiently large pressure arises in the box (when the diffuser goes inside the box), and a sufficiently large discharge (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 place 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 phase inverter is designed, the main purpose of which is to invert, i.e. reverse phase. As a result, sound is emitted into space not only by the front of the diffuser, but also by the rear, the phase of which is changed by the phase inverter.
A more complex version of acoustic design is an acoustic labyrinth. The essence of this option lies in the fact that the paths inside the speakers are arranged in such a way that resonance occurs at a certain frequency and, as a result, a large increase in recoil at this frequency. The calculation and manufacturing accuracy of such systems should be taken VERY seriously, since there is a high probability of "standing" waves in the labyrinth. In this case, the sound quality will be even worse than that of the version with an acoustic shield:
An even greater return at the resonant frequency can be obtained with a horn version:
The difference between a horn speaker and a speaker with a labyrinth is that the direction of sound waves in them changes according to different laws - the horn either expands conically along its entire length, or exponentially. A labyrinth can have the same window along its entire length, it can expand or, conversely, 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, and for horns, both sides can radiate.
The next version of the acoustic design is a bandpass or band-pass resonator:
This option differs from all the previous ones, first of all, in that it emits only at the resonance frequency and requires the strictest adherence to the calculated dimensions.
The last three options are mainly designed for the use of a low-frequency dynamic head, and the previous ones are quite suitable for a wideband speaker. Therefore, if the speaker system has other speakers in addition to woofers, for example, midrange and treble, then it is not recommended to embed them in a housing with a woofer.
In any case, to calculate the dimensions of the speaker you will need the characteristics of the dynamic head, in particular the Thiel-Small parameters. If these data are not available, but before you start calculating the dimensions of the speaker case, you need to get them. There are a lot of descriptions of methods for obtaining these parameters - it is enough to use any search engine.
Of course, these are not all types of acoustic design - these are the most popular.
The dimensions of the enclosure are calculated using special programs for calculating the speaker enclosures. Finding them on the Internet, as well as instructions on how to use them, is also not problematic.
When designing the speaker, some technological features should be taken into account - if the front panel on which the speaker is installed is recessed into the housing, then additional ribs will need to be made, into which the front panel will actually rest:
If you don't want to mess with the ribs, you can make the front panel in such a way 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 case.
Also, you should 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 construct, however, this method involves chamfering the diameter of the dynamic head and immersing the speaker inside the case so that ALL radiators, both LF, MF, and HF are on the same line. chamfering reduces the mechanical strength of the bezel and requires an additional inner ring to restore it. The relevance of this ring is the higher, the more power is expected to be obtained from the manufactured speaker and at powers above 150 W it is already 100% necessary:
On the ring, if necessary, you will need to remove the side chamfers so that it does not interfere with the front panel of the installation in the case itself.
When installing the dynamic head, ensure that there are no gaps. If the chamfer is removed by a machine, then the surface is relatively flat, it remains only to sand it. However, at home, getting a flat surface is quite difficult. Here it is not entirely clear what the manufacturers are doing - it is strongly recommended to install the speaker outside, but the sealing rubber on almost all dynamic heads is located for installation from the inside:
To solve the problems of tightness, you can use a door seal - self-adhesive strips of porous rubber, sold in all hardware stores. The seal is glued along the perimeter of the chamfer and during the installation of the speaker completely fills all the gaps:
If the dynamic head is installed from the inside, then the hole will need to be chamfered to eliminate the appearance of standing waves. However, such a chamfer weakens the rigidity at the point of attachment of the speaker to the panel (the material turns out to be too thin) and this mounting method is not acceptable for powers above 50 W without additional reinforcement of the construct:
It is advisable to use natural material for the manufacture of speaker cabinets, plywood is optimal, but this material is too expensive. Therefore, it is better to use plywood for the construction of loudspeakers in the middle and high price range, using VERY good quality drivers and power above 100 watts.
For a medium price category and small capacities (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 with the use of technological tricks.
The first problem, in the manufacture of speakers from plastic, arises when the bounce of the plastic itself is eliminated, especially in the centers of the sidewalls. You can get rid of this unpleasant sound by using a thicker plastic, or you can glue additional stiffeners. If the plastic dissolves with dichloro tane, then dichloro tane can be used to fix the ribs, with plastic chips dissolved in it. If the plastic does not dissolve with dichloromethane, then it is better to use epoxy glue, preferably from Dzerzhinsky production. Before gluing, the places of the context should be carefully processed with a grain of sandpaper and they are not afraid that the glue forms rollers at the point of contact of the parts to be glued:
For greater efficiency in suppressing the overtones of the body, you can "paint over" in 2-3 layers the resulting "baths" with anti-gravel - a coating used to cover the bottom of cars to protect against fine gravel.
After drying, the anti-gravel acquires the properties of rubber and absorbs sound quite well.
When used as a material for the manufacture of AS fiberboard, it is required to be determined with 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 covered with epoxy glue on one side and heated with a hairdryer. Under the influence of temperature, the glue becomes more liquid and impregnates the fiberboard to almost half the thickness. After the glue hardens, a rather strong material is obtained, in fact a getinax, but on the one hand, it retains the sound-absorbing properties of fiberboard. You can cut DPV with a jigsaw, you can glue the workpieces with epoxy glue, reinforced with material. For this, the blanks are folded into the desired structure, and grabbed 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 on" with a 40 ... 60 W soldering iron. The high temperature allows the glue to completely saturate the weave, and also significantly accelerates the polymerization of the glue. True, during work, a certain amount of smoke is emitted, so work must be done either on the street or under an exhaust hood:
If a speaker with a power 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, it will already be necessary to fold the fiberboard three times or use a chipboard 18 mm thick (unfortunately, chipboard 22 mm thick can only be found in old grandmothers in the form of old, up to the 80s, wardrobes). To stiffen the sidewalls, you can use CREST struts:
For powers up to 50 W, the relevance of using fiberboard is already controversial - it is much easier to work with particleboard, MDF or plywood than folding fiberboard from 4-5 layers. For this, a material with a thickness of 18 mm is suitable, but you will have to use additional beams, which provide a greater bunch of the speaker parts with each other:
The speaker can be assembled using self-tapping screws, but since the power is not more, you can also glue it with epoxy glue or PVA, only it is better to buy it not in a stationery store, but in a household or construction one. This PVA will be called MOMENT-STOLYAR, water-dispersible glue. Buy in the market recommended only in summer - after freezing, the glue seriously loses its quality. However, to calm the conscience, it is better to screw at least a couple of self-tapping screws into each bar.
In the manufacture of speakers, they sometimes make a gross mistake - the mid-high-frequency link does not acoustically protect against the impact of the rear side of the woofer diffuser, which leads to a decrease in the efficiency of the speaker itself, and often to the failure of the mid-range link - too strong air strikes from the rear side of the low-frequency diffuser lead to pushing the midrange speaker coil 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-tweeter speakers from the total volume of the speakers, as a result, the internal volume of the speakers is less than necessary and the final characteristics are heavily lubricated - the resonant frequency of the phase inverters increases noticeably, which will lead to unwanted overtones.
When assembling speakers with a power of up to 100 W, you can also use either chipboard or 18 mm plywood, although of course it is better to look for material 22 mm thick. To exclude the occurrence of resonances in the sidewalls of the speaker cabinet, additional bars are also used, through which the speaker parts are attached. It will not be superfluous to install a "cross" and an additional washer for attaching the woofer of the dynamic head, as well as processing the speaker from the inside with sound-absorbing materials, for example, pasting with paralon or foam plastic with a thickness of 5-10 mm, just do not forget that pasting will "eat" part of the internal volume and it must be corrected for when calculating the size of the case.
The best results are obtained with polyurethane foam, since the thickness of the applied layer can be adjusted by the rate at which the foam is released from the spray can. If the foam is released VERY slowly, then it will 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 solidified, it greatly increases in volume. If foam is applied to the sides of the case from the front panel, increasing the foam output when approaching the rear wall, and at the front panel ensuring the minimum foam output rate, the internal volume of the speaker will take the shape of a pyramid lying on its side. Such tricks allow you to completely solve the problems of standing waves, since there are no parallel planes inside the speaker, and the unevenness of the frozen foam only enhances the effect of the pyramid. When using this technology, one should more carefully approach the calculations of the dimensions of the workpieces - the internal volume decreases VERY strongly and this requires a serious increase in the speaker cabinet.
The ribs for attaching the sidewalls, in addition to the screed with self-tapping screws, are recommended to be glued, as in the previous version, but there are slightly more options for adhesive masses:
- epoxy glue mixed with fine sawdust or, better, wood dust;
- MOMENT-CARPENTER, but before the screed, the applied glue should be allowed to dry a little, until the consistency of butter at room temperature is obtained. This will allow you to more fully 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 assembling the gluing site, it is necessary to thoroughly warm it up with a hairdryer, which will lead to the formation of small bubbles in the glue mass, and the mass itself will more densely fill the irregularities between the contacting parts of the case;
- automotive sealant of domestic production, namely domestic, since after hardening it is much tougher than imported sealants;
- polyurethane foam. Before being applied to the parts to be glued, the foam is "released" onto an unnecessary piece of plywood or particle board, and then thoroughly mixed with a metal spatula until it "shrinks", i.e. until a mass is obtained in a density similar to thick sour cream. After application and screed, the foam will still expand slightly and completely fill in all the irregularities at the point of contact of the speaker parts.
After gluing, the parts must 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 connection of two identical speakers for the low-frequency link is used. In this case, the total area of the diffusers increases, hence the speaker can interact with a much larger amount of air, i.e. create a higher sound pressure and from this the subjective loudness is much higher:
It should be noted here that the use of a large number of speakers, including for dividing the audio range, starts to introduce some troubles - it is rather difficult to achieve signal phasing in those places where the frequency response of the speakers neighboring in the range intersects. Therefore, you should not chase a large number of stripes for a home-made speaker - this porridge with such butter can be very spoiled.
Speakers with a power from 100 to 300 W are best made of plywood, and you will have to look for plywood 22 mm thick. 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 sidewalls, and the hypotenuse will be directed towards the inside of the body.
If you cannot find plywood of this thickness, then you can use plywood 8 mm thick glued three times - the final material thickness is 24 ... 25 mm. The adhesives are listed above.
As a technological advice, one can only recommend that you first cut the necessary blanks and only then glue them together, and immediately tighten them with self-tapping screws.
When installing a "cross" inside the speaker, which will not be superfluous, it is better to round the corners of the staggering beams - rather large volumes of air are already moving and turbulence may occur around the right angles of the screeds. It is also recommended to "round off" all internal corners, using plasticine or applying several layers of thick anti-gravel.
Another type of acoustic design is separate enclosures for each speaker. These speakers do not use passive filters, and the signal is divided into ranges immediately after the amplifier's volume control. Then the split signal is fed to three separate power amplifiers, which actually work each for its own speaker:
It would not be fair 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 rather problematic to obtain the characteristics of the "filler" in household conditions, so it remains either to refuse to use the "filler", or to experimentally find out the required volume and material used (usually fluff cotton wool, batting, centipon).
At powers of 100 W or more, it also becomes important to ensure the stability of the speaker case, since quite a lot of work is already being done to move the diffuser and the air is actively "resisting". It is also desirable 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 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 speaker and it is desirable to use materials of different structures, for example, if the front panel is made of plywood, then a chipboard sheet is glued on the inside, the thickness of which is 1.5-2 times less than the thickness of the panel. Such a combination of materials provides absorption of vibrations in a larger sound range precisely due to the heterogeneity of the materials.
For greater stability of the speaker, its mass can be increased by smearing the bottom with polyurethane foam and put a couple of bricks in it, covering them on top with the same foam. After the foam hardens, 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 over 200 W, it is better to use combination materials - all speaker parts are glued 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. Inside the speaker, it is advisable to glue it with a sound-absorbing material, for example, a batting stitched three times, double stitched with a quad centpon (a centpon can be double and quadruple), 5 ... 10 mm foam. The different structure of densely bonded materials of different structure eliminates the problem of resonance of the case 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 speaker from damage - the speakers are already quite heavy and during transportation, various shocks 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 DPS is glued between the layers of plywood, however, more specifically, the speakers are already moving into the category "for sounding", therefore quality can be sacrificed for mobility. Based on this, it is possible to use double 18 mm plywood with a "cross" installed inside.
It is not difficult to notice that with an increase in power, the wall thickness of the speaker increases. This is primarily due to the fact that it is necessary to isolate the air moving inside the speaker from the listener. Keep in mind, however, that the speaker cabinet can also resonate. It is to eliminate this nuisance that it is better to use the internal pasting of the enclosures and to minimize the resonance sounds obtained from the resonance. It is not difficult to check the resonant frequency of the case yourself. To do this, it is necessary to tilt the speaker by 20 ... 25 degrees and throw a rubber mallet on top of it from which, first pull out the handle. The tilt of the speaker is necessary so that the blow is single and the mallet bounces far to the side.
A microphone attached to the speaker (membrane opening to the body) and connected to any linear amplifier on the oscilloscope screen will draw both the moment of impact and the after-sound that the body itself gives. The test is, of course, rather rough, since in reality the "shock wave" comes from the inside, and during the experiment from the outside, nevertheless, on the basis of the results of this test, one can judge at what frequency the case itself resonates and how quickly the attenuation occurs:
An ideal speaker does not cut and the moment of impact dies out immediately, almost instantly, but the walls of an ideal speaker consist of concrete 1 cm thick for each W of power, and such an speaker is more suitable for ridicule than for operation:
The finishing of the speaker system can be very different, there are no strict requirements here. If the body is made of plywood and the drawing is pretty pretty, then the body can be sewn up, and then several times covered with colorless varnish:
You can buy veneer of valuable tree species and paste over the speaker with veneer to match the color of the furniture in the room:
In car audio salons, the so-called acoustic fabric is sold, which is a synthetic felt. The material adheres well and stretches, which will allow you to finish the speaker at a fairly high level:
Having sanded the body, you can paint it with car paint, just let's make an amendment to the fact that the car enamels are dried at a high temperature. Therefore, you will have to use a special hardener "IZUR", the mixing proportions are written on the hardener packaging, although it is better to add it 10-15% more than the proposed proportion:
If the body is carefully sanded and sanded, then it can be pasted over with a self-adhesive film sold in the OBOI stores, but this material is quite delicate and should be used if there is confidence that the speakers will stand in its place for ten years:
If you plan to transport your speaker system frequently, it will be very helpful 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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