› › What material is used inside acoustic speakers. What sound-absorbing and sound-proofing materials to choose. All these operations must be carried out carefully and without sudden movements, in order to avoid damage to wires and circuits.

What material is used inside acoustic speakers. What sound-absorbing and sound-proofing materials to choose. All these operations must be carried out carefully and without sudden movements, in order to avoid damage to wires and circuits.

Previously, speakers were ordinary horn loudspeakers and did not have a housing as such. Everything changed when speakers with paper cones appeared in the 20s of the 20th century.

Manufacturers began making large cases that housed all the electronics. However, until the 50s, many audio equipment manufacturers did not completely close the speaker cabinets - the back remained open. This was due to the need to cool the electronic components of that time (tube equipment).

The purpose of a speaker enclosure is to control the acoustic environment and contain the speakers and other system components. Even then it was noticed that the housing can have a serious impact on the sound of the loudspeaker. Since the front and rear parts of the speaker emit sound with different phases, amplification or attenuation interference occurred, resulting in deterioration of the sound and the appearance of comb filtering effect.

In this regard, the search began for ways to improve sound quality. To achieve this, many began to explore the natural acoustic properties of various materials suitable for the manufacture of enclosures.

Waves reflected from the inner surface of the walls of the speaker housing are superimposed on the main signal and create distortion, the intensity of which depends on the density of the materials used. In this regard, it often turns out that the case costs much more than the components contained in it.

When producing cabinets in large factories, all decisions regarding the choice of shape and thickness of materials are made on the basis of calculations and tests, but Yuri Fomin, a sound engineer and speaker design engineer, whose developments form the basis of multimedia systems under the Defender, Jetbalance and Arslab brands, does not excludes that even in the absence of special musical knowledge and extensive experience in the audio industry, it is possible to make something close in characteristics to “serious” Hi-Fi.

“We need to take ready-made developments that engineers share online and repeat them. This is 90% success,” notes Yuri Fomin.

When creating a speaker system housing, you should remember that, ideally, sound should come only from the speakers and special technological holes in the housing (bass reflex, transmission line) - you need to take care that it does not penetrate through the walls of the speakers. To do this, it is recommended to make them from dense materials with a high level of internal sound absorption. Here are some examples of what you can use to build a speaker enclosure.

Chipboard (chipboard)

These are boards made from compressed wood chips and glue. The material has a smooth surface and a loose, loose core. Chipboard dampens vibrations well, but transmits sound through itself. The boards are easily held together with wood glue or assembly adhesive, but their edges tend to crumble, which makes working with the material a little more difficult. He is also afraid of moisture - if production processes It absorbs and swells easily.

Stores sell boards of different thicknesses: 10, 12, 16, 19, 22 mm and so on. For small cases (volume less than 10 liters) chipboard with a thickness of 16 mm is suitable, and for larger cases you should choose boards with a thickness of 19 mm. Chipboard can be covered: covered with film or fabric, puttied and painted.

Chipboard is used to create the Denon DN-304S speaker system (pictured above). The manufacturer chose chipboard because this material is acoustically inert: the speakers do not resonate or color the sound even at high volumes.

Lined with chipboard

This is chipboard, lined with decorative plastics or veneer on one or both sides. Boards with wood cladding are held together with regular wood glue, but for chipboard lined with plastic, you will have to buy special glue. You can use edge tape to process board cuts.

Joiner board

A popular building material made from slats, bars or other fillers, which are covered on both sides with veneer or plywood. The advantages of wood board: relatively light weight and ease of edge processing.

Oriented Strand Board (OSB)

OSB is boards pressed from several layers of thin plywood and glue, the pattern on the surface of which resembles a mosaic of yellow and brown colors. The surface of the material itself is uneven, but it can be sanded and varnished, since the texture of the wood gives this material an unusual appearance. This slab has a high sound absorption coefficient and is resistant to vibrations.

It is also worth noting that, due to its properties, OSB is used to form acoustic screens. Screens are necessary to create listening rooms where users can evaluate the sound of loudspeaker systems under near-ideal conditions. OSB strips are attached at a certain distance from each other, thereby forming a Schroeder panel. The essence of the solution is that the strip fixed at certain points under the influence acoustic wave calculated length begins to emit in antiphase and extinguishes it.

Medium Density Fiberboard (MDF)

Made from wood chips and glue, this material is smoother than OSB. Due to its structure, MDF is well suited for the manufacture of designer cabinets, since it can be easily cut - this simplifies the joining of parts fastened together using mounting adhesive.

MDF can be veneered, puttied and painted. The thickness of the boards varies from 10 to 22 mm: for speaker bodies with a volume of up to 3 liters, a board with a thickness of 10 mm will be sufficient, for up to 10 liters - 16 mm. For large cases, it is better to choose 19 mm.

If, when choosing a material for the manufacture of speaker cabinets, we put aside the sound aspects, then three defining parameters remain: low cost, ease of processing, ease of gluing. MDF has all three. It is the low cost and “pliability” of MDF that make it one of the most popular materials for making speakers.

Plywood

This material is made from compressed and glued thin veneer (about 1 mm). To increase the strength of plywood, veneer layers are applied so that the wood fibers are directed perpendicular to the fibers of the previous sheet. Plywood is the best material for suppressing vibrations and keeping sound inside the cabinet. You can glue plywood boards together with regular wood glue.

Sanding plywood is more difficult than MDF, so you need to cut out the parts as accurately as possible. Among the advantages of plywood, it is worth highlighting its lightness. For this reason, it is often used to make cases for musical instruments, because it is quite a shame to cancel a concert because a musician injured his back.

It is this material that Penaudio uses to produce floor-standing acoustics - it uses Latvian plywood, which is made from birch. Many people like the way treated birch plywood looks, especially after varnishing - it gives the body a unique look. The company takes advantage of this: the transverse layers of plywood have become a kind of “calling card” of Penaudio.

Stone

The most commonly used stones are marble, granite and slate. Slate is the most suitable material for making cabinets: it is easy to work with due to its structure and it absorbs vibrations effectively. The main disadvantage is that special tools and stone processing skills are required. To somehow simplify the work, it may make sense to make only the front panel from stone.

It is worth noting that to install stone speakers on a shelf, you may need a mini-crane, and the shelves themselves must be strong enough: the weight of a stone audio speaker reaches 54 kg (for comparison, an OSB speaker weighs about 6 kilograms). Such enclosures seriously improve sound quality, but their cost can be prohibitive.

The speakers are made from a single piece of stone by the guys from Audiomasons. The bodies are carved from limestone and weigh about 18 kilograms. According to the developers, the sound of their product will appeal to even the most sophisticated music lovers.

Plexiglass/glass

You can make a speaker housing out of transparent material - it's really cool when you can see the "insides" of the speaker. Only here it is important to remember that without proper insulation the sound will be terrible. On the other hand, if you add a layer of sound-absorbing material, the transparent case will no longer be transparent.

A good example of high-end acoustic equipment made from glass is the Crystal Cable Arabesque. Cases of Crystal Cable equipment are made in Germany from strips of glass 19 mm thick with polished edges. The parts are fastened together with invisible glue in a vacuum installation to avoid the appearance of air bubbles.

At CES 2010, held in Las Vegas, the updated Arabesque won all three awards in the field of Innovation. “Until now, no equipment manufacturer has been able to achieve true hi-end sound from acoustics made from such a complex material. – wrote the critics. “Crystal Cable has proven that it can be done.”

Laminated timber/wood

Wood makes good cases, but there are some things to consider here: important point: wood has the property of “breathing”, that is, it expands if the air is humid and contracts if the air is dry.

Since the wooden block is glued on all sides, tension is created in it, which can lead to cracking of the wood. In this case, the housing will lose its acoustic properties.

Metal

Most often, aluminum is used for these purposes, or more precisely, its alloys. They are light and tough. According to a number of experts, aluminum can reduce resonance and improve the transmission of high frequencies in the sound spectrum. All these qualities contribute to the growing interest in aluminum from audio equipment manufacturers, and it is used for the manufacture of all-weather speaker systems.

There is an opinion that making an all-metal case is not a good idea. However, it is worth trying to make the top and bottom panels, as well as the stiffening partitions, from aluminum.

Based on materials from: geektimes.ru

The decline in amplitude-frequency characteristics in 100-liter speakers begins at approximately 60 Hz; to ensure high-quality sound from 30 Hz, a speaker volume of 400 liters is required. These contradictions are illustrated in Table 1

Table 1. LIMITING REQUIREMENTS AND MODERN ACCURACY OF SOUND REPRODUCTION.
Main parameters. Numerical recording and reproduction of electrical signals in the audio range. Limits of human capabilities. World-class electroacoustic transducers (output speakers) MONOLITH-111X Domestic speakers 35-AC (running for music lovers) The best domestic speakers 3 SL-113
Frequency reproduction bandwidth, Hz. 10-20000 16-22000 28-24000 50-20000 63-25000
Frequency response unevenness, dB. 0.5 0.5 + / - 2 + / - 5 + / - 3
Nonlinear distortion (clear factor), %. 0.005 0.05 1 12 2
Dynamic range, dB. 90 120 120 100 110
Preferred volume ( dynamic range), dB. - 80 for amateurs. 90 for professionals - - -
Volume, liters. - - 380 70 125
Cost, US dollars. 500 - 7000 per pair 300 per pair 500 per pair

As you can see, even in very expensive speakers with a volume of up to 400 liters, the entire octave is unsatisfactorily reproduced - 16:32 Hz, and harmonic distortion is 20 times higher than the permissible values. In mid-priced speakers with a volume of 60:100 liters, the second octave is unsatisfactorily reproduced - 32:64 Hz and the first is practically absent, while harmonic distortion exceeds the permissible limit by 50:100 times.

The last word in solving this problem is the active subwoofer - a separate loudspeaker designed to reproduce exclusively the low-frequency region of the sound spectrum. The dimensions of such subwoofers range from 70:40 liters, the frequency range is usually 30:150 Hz, but the “sweet-voiced” speakers for it do not exceed 10:12 liters. The increase in low frequencies in subwoofers is ensured by forced amplification modes built into the amplifier, which inevitably gives rise to an increase in harmonic distortion. To match the subwoofer with a pair of standard speakers, a special digital filter is required - all together leads to a price of about 500 US dollars.

As we can see, improving the acoustic performance of small-sized speakers using sound absorption inside the box remains attractive.

The proposed new original technical solution for the formation of a sound-absorbing environment can significantly simplify the situation. An experimental decrease in sound pressure in such an environment was obtained by up to 50 times. In addition, the sound-absorbing medium, compared to air, has a significantly higher viscosity; this quality, combined with the ability to reduce sound pressure, has the most favorable effect on the suppression of numerous resonances in the box, i.e. leads to smoothing (straightening) of the amplitude-frequency response and reducing harmonic distortion. There are no restrictions on the dimensions and shape of the absorbing medium, or on the amount of sound pressure.

A modern acoustic system usually contains 3 electroacoustic transducers: high-frequency, mid-frequency and low-frequency (woofer). The first 2 converters do not require large volumes for high-quality sound reproduction, therefore they are supplied already enclosed, and the woofer requires large volumes, so its housing is the body of an acoustic speaker. The new technical solution will make it possible to reduce the physical dimensions of the woofer housing to the size of the woofer itself and opens up the possibility of supplying it also packaged, in which case special requirements for the speaker system housing disappear.

For example, housing a 10-inch woofer with 6 liters of sound-absorbing media provides the following characteristics:

  • Frequency range (with unevenness of 0.5 dB and a decline of 31.5 Hz-6 dB) - 31.5...1250 Hz.
  • Maximum acoustic pressure - 110 dB.
  • Harmonic distortion at 90 dB - 0.5%

The research results are illustrated by graphs in Fig. 1 and Fig. 2, from which it follows that, in comparison with a modern subwoofer, the reproduction of low frequencies using the proposed solution is half an octave deeper, even with a closed-type acoustic design; the diffuser experiences a pneumatic load no more than in free space, the medium is viscous, as evidenced by the disappearance of the speaker system's own resonance - all this ensures extremely low harmonic distortion. If you take into account that the new technical solution provides dimensions that are an order of magnitude smaller, does not require an amplifier and an expensive digital filter, and provides a price several times lower, then you involuntarily begin to join in with those who believe that modern subwoofers are a “step to the side” : "a gesture of desperation born of the awareness of the serious limitations in achieving the deepest bass using classic loudspeaker systems." The real way to solve the problem of deep bass is opened by Russian patent No. 2107949 for the invention “Device for high-quality sound reproduction.”

This is a new series of posts dedicated to acoustic systems. Due to the fact that the topic is extremely broad, we decided to create a series of articles reflecting the selection criteria when purchasing speakers. This post is dedicated to the acoustic properties of cabinet materials and acoustic design. The post will be especially useful for those who are faced with choosing speakers, and will also provide information for people who want to create their own speakers in the process of their DIY experiments.

There is an opinion that one of the decisive factors affecting the sound of speakers is the material of the housing. PULT experts believe that the importance of this factor is often exaggerated, however, it is truly important and cannot be written off. An equally important factor (among many others) that determines the sound of speakers is the acoustic design.

Material: from plastic to granite and glass

Plastic - cheap, cheerful, but resonates

Plastic is often used in the production of budget speakers. The plastic body is lightweight, significantly expands the possibilities of designers; thanks to casting, almost any shape can be realized. Various types plastics differ very seriously in their acoustic properties. In the production of high-quality home acoustics, plastic is not very popular, but it is in demand for professional samples, where low weight and mobility of the device are important.

(for most plastics the sound absorption coefficient ranges from 0.02 - 0.03 at 125 Hz to 0.05 - 0.06 at 4 kHz)

Tree - from felling to golden ears

Due to its good absorption properties, wood is considered one of the best materials for making speakers.

(the sound absorption coefficient of wood, depending on the species, ranges from 0.15 – 0.17 at 125 Hz to 0.09 at 4 kHz)

Solid wood and veneer are used relatively rarely for the production of speakers and, as a rule, are in demand in the HI-End segment. Wooden speakers are gradually disappearing from the market due to low manufacturability, instability of the material and prohibitively high cost.

It is interesting that in order to create truly high-quality speakers of this type that meet the requirements of the most sophisticated listeners, technologists must select material at the cutting stage, as in the production of acoustic musical instruments. The latter is related to the properties of wood, where everything is important, from the area where the tree grew, to the humidity level of the room where it was stored, the temperature and duration of drying et cetera. The latter circumstance complicates DIY development; in the absence of special knowledge, an amateur creating a wooden speaker is doomed to act by trial and error.

Manufacturers of such acoustics do not report how the situation really is and whether the described conditions are met, and accordingly, any wooden system requires careful listening before purchasing. With a high degree of probability, two speakers of the same model from the same breed will sound slightly different, which is especially important for some discerning listeners with golden ears with big money.

Columns from an array of valuable rocks are available in units, their cost is astronomical. Everything yours truly has heard sounds excellent. However, in my subjectively pragmatic opinion, it is disproportionate to the cost. Sometimes, well-designed enclosures made of plywood and MDF have no less musicality, but for many audiophiles “not wood” = “not true hi-end”, and for some, “not wood” simply does not allow the status or spoils the interior design.

I believe that one of the best wooden systems in our catalog is this:
Floor-standing acoustics Sonus Faber Stradivari Homage graphite (price appropriate)

Plywood is almost a tree if it hasn't flown over Beijing

Plywood, used for the production of acoustic enclosures, has from 10 to 14 layers and is almost as good as wood in terms of acoustic properties, in particular in sound absorption, while being somewhat cheaper than wood, more technologically advanced in processing, lighter than chipboard and MDF. Multilayer plywood dampens unwanted vibrations well due to the structure of the material.

(sound absorption coefficient of 12-layer plywood ranges from 0.1–0.2 at 125 Hz to 0.07 at 4 kHz)

Like wood, plywood is used in quite expensive and sometimes luxury piece products. The cost of plywood speakers is not much lower than those made from solid wood, and are quite comparable in quality.

In some cases, cases declared by the manufacturer as “plywood” are made of chipboard and MDF. Therefore, low prices for speakers with plywood or wooden casings should alert you. A number of small Asian manufacturers, which change names regularly and sell mostly online, create composite cabinets that include a few small but noticeable plywood (wood) elements, with the bulk made from chipboard.

Among the speakers made from plywood, I can especially highlight this one: Yamaha NS-5000 bookshelf speakers

Chipboard – thickness, density, humidity

Chipboard is comparable in cost to plastic, but does not have a number of disadvantages that are inherent in plastic cases. The most significant problem of chipboard is low strength, with a fairly high mass of material.

Sound absorption in chipboard is non-uniform and in some cases low- and mid-frequency resonances may occur, although the likelihood of their occurrence is lower than in plastic. Plates with a thickness of more than 16 mm, which achieve the required density, can effectively dampen resonances. It should be noted that, as in the case of plastic, the properties of a particular chipboard are of great importance. It is important to take into account the density and humidity of the material, since different chipboards differ in these parameters. Thick, dense chipboards are often used to create studio monitors, which indicates the demand for the material in the production of professional equipment.

On a note, for comrades from the DIY fraternity, chipboard with a density of at least 650 - 820 kg/m³ (with a board thickness of 16 - 18 mm) and a humidity of no more than 6-7% is well suited for creating speakers. Failure to comply with these conditions will significantly affect the sound quality and reliability of the speakers.


Among worthy chipboard options for home speakers, our experts highlight: Cerwin-Vega SL-5M

MDF: from furniture to acoustics

Today, MDF (Medium Density Fiberboard) is used everywhere, among other things, MDF is one of the most common modern materials for the production of acoustics.

The reason for the popularity of MDF was the physical properties of the material, namely:

  • Density 700 - 800 kg/m³
  • Sound absorption coefficient 0.15 at 125 Hz – 0.09 at 4 kHz
  • Humidity 1-3%
  • Mechanical strength and wear resistance

The material is cheap to produce, has acoustic properties comparable to those of wood, while the resistance of the boards to mechanical damage is somewhat higher. MDF has sufficient acoustic rigidity of the speaker cabinet, and sound absorption meets the parameters necessary for creating HI-FI acoustics.
Visual difference between MDF and chipboard

There are a lot of wonderful systems among MDF acoustics; in my opinion, the optimal ones in terms of price/quality ratio are the following:

→ Yamaha NS-BP182 piano black - bookshelf

→ Focal Chorus 726 - floor-standing

Aluminum alloys - design and precise calculations

The most common metal in the production of speakers is aluminum, as well as alloys based on it. Some authors and experts believe that the aluminum housing reduces resonances and also improves the transmission of high frequencies. The sound absorption coefficient of aluminum alloys is not high, and is about 0.05, which, however, is significantly better than that of steel. To reduce body vibration, increase sound absorption and prevent harmful resonances, manufacturers use sandwich panels, where a layer of high molecular weight polyethylene resins or other low-density materials, such as viscoelastic, is placed between 2 aluminum sheets.

In the case of budget aluminum speakers, manufacturers often rely on design at the expense of sound: as a result, the acoustic characteristics leave much to be desired. Sometimes users of such acoustics complain of a harsh, distorted sound caused by insufficient sound absorption of the housing. Due to the fact that waves are well reflected and poorly absorbed, precise calculation of the housing design, selection of emitters, filters used, as well as the quality of connections of individual parts become very important in metal acoustics.

Among decent-sounding aluminum speakers, I was especially impressed by the sound:

→ Canton CD 310 white high gloss (impressive price, but not prohibitive)

Stone – granite slabs at the price of gold bars

Stone is one of the most expensive materials for the production of acoustic enclosures. Impeccable reflection and the practical impossibility of the appearance of vibrational resonances make these materials in demand among particularly demanding listeners.

Most rocks have a stable sound absorption coefficient, which, for example, for granite is 0.130 for the entire spectrum of sound frequencies, and for limestone 0.264. Manufacturers especially value porous stones, which have higher sound absorption.

Using stone slabs to make DIY acoustics is almost impossible, since it requires not only remarkable knowledge in acoustics and stone processing, but also extremely expensive equipment (no one produces home-made 3-D stone milling machines yet).


For the production of serial speakers, rocks such as granite, marble, slate, limestone, and basalt are used. These rocks have similar acoustic properties, and with appropriate processing they become real works of art. Stone enclosures are often used to create landscape acoustics; in such cases, a cavity is created in the raw stone to accommodate the emitter, in which fastening elements are installed (usually made to order).

The stone has 2 main problems: cost and weight. The price of a stone speaker may be higher than any other with similar characteristics. Weight of some samples floor systems can reach 40 kg or more.

Glass transparency and sound quality

An original solution is to create speakers from glass. So far, only two companies, Waterfall and SONY, have seriously succeeded in this matter. The material is interesting from a design point of view; acoustically glass creates certain problems, mainly in the form of resonances, which the above-mentioned companies have learned to solve; there are even reference options.

The prices for the transparent miracle can also hardly be called affordable; the latter is associated with low manufacturability and high production costs.

Of the glass samples that impressed with their sound, I can recommend: Waterfall Victoria Evo

Acoustic design - boxes, tubes and horns

Acoustic design is no less important for accurate sound transmission in speakers. I will talk about the most common types (it is natural that certain types can be combined depending on specific model, for example, the bass-reflex part of the speaker is responsible for the low and mid-frequency range, and a horn is built for the high ones).

Bass reflex - the main thing is the length of the pipe

A bass reflex is one of the most common types of acoustic design. This method allows, with the correct calculation of the length of the pipe, the cross-section of the hole and the volume of the housing, to obtain high efficiency, an optimal frequency ratio, and amplify low frequencies. The essence of the phase inverter principle is that on the back of the body there is a hole with a pipe, which allows you to create low-frequency oscillations in phase with the waves created by the front side of the diffuser. Most often, the bass reflex type is used when creating 2.0 and 4.0 systems.

To make calculations easier when creating your own speaker, it is convenient to use special calculators; one of the convenient ones is provided at the link.

In the HI-END philosophy, there are extremely radical, uncompromising judgments about bass reflex systems; I present one of them without comment:

“Enemy No. 1 is, of course, nonlinear amplification elements in the sound path (then everyone, to the best of their education, understands which elements are more linear and which are less). Enemy No. 2 is the bass reflex. the bass reflex is designed to show off, it should allow a small cheap speaker to record 50... 40... 30 in the passport, and what a trifle even 20 Hz at a level of -3 dB! But the lower frequency range of the bass reflex ceases to be relevant to music; more precisely, the bass reflex itself is a pipe singing its own melody.”

A closed box is a coffin for extra low ones

The classic option for many manufacturers is a regular closed box with speaker diffusers brought to the surface. This type of acoustics is quite simple to calculate, but the efficiency of such devices is not great. Also, the boxes are not recommended for lovers of characteristically pronounced lows, since in a closed system without additional elements that can enhance the lows (bass reflex, resonator), the frequency spectrum from 20 to 350 Hz is poorly expressed.

Many music lovers prefer the closed type, since it is characterized by a relatively flat frequency response and realistic “honest” transmission of the reproduced musical material. Most studio monitors are created in this acoustic design.

Band-Pass (closed resonator box) – the main thing is not to buzz
Open body - no extra walls

A relatively rare type of acoustic design today, in which the rear wall of the housing is repeatedly perforated or completely absent. This type of design is used to reduce the number of housing elements that affect the frequency response of the speakers.

IN open box The front wall has the most significant influence on the sound, which reduces the likelihood of distortion introduced by other parts of the case. The contribution of the side walls (if any are present in the structure), given their small width, is minimal and amounts to no more than 1-2 dB.

Horn design - problematic loudness champions

Horn acoustic design is more often used in combination with other types (in particular for the design of high-frequency emitters), however, there are also original 100% horn designs.

The main advantage of horn speakers is their high volume when combined with sensitive speakers.

Most experts, not without reason, are skeptical about horn acoustics, for several reasons:

  • Structural and technological complexity, and accordingly, high requirements for assembly
  • It is almost impossible to create a horn speaker with a uniform frequency response (with the exception of devices costing 10 kilobucks and more)
  • Due to the fact that the horn is not a resonating system, it is impossible to correct the frequency response (a minus for DIYers who intend to copy a Hi-end horn)
  • Due to the peculiarities of the waveform of horn acoustics, the sound volume is quite low
  • Overwhelmingly relatively low dynamic range
  • It produces a large number of characteristic overtones (considered a virtue by some audiophiles).


Horn systems have become the most popular among audiophiles in search of “divine” sound. The tendentious approach allowed the archaic horn design to get a second life, and modern manufacturers were able to find original solutions (effective, but extremely expensive) to common horn problems.

That's all for now. To be continued, as usual, but the “autopsy” will definitely show... I’ll announce for the future: emitters, power/sensitivity/room volume.

habr.com

The best soundproofing material, soundproofing ratings

Soundproofing of residential premises is becoming more and more relevant every year. And every homeowner wants to choose the best soundproofing material to protect against outside noise. Although it is difficult to choose soundproofing products based on the “good or bad” principle, since many of them have a specific purpose and, to one degree or another, fulfill the intended purpose.

The best soundproofing material, top six ranking

As a rule, sound insulation is a complex multilayer structure, including dense layers that reflect sound waves and soft layers that absorb extraneous sounds. In this regard, neither mineral wool, nor membrane, nor panel materials should be used as independent sound insulation.

At the same time, it is a mistake to assume that heat insulators (cork, PPS, PPE, etc.) are capable of fully fulfilling the role of noise protection. They are not able to stop creating a barrier against the penetration of structural noise. Even worse, if sheets of polyurethane or polystyrene foam are glued to the wall under the plaster, then such a design will increase the resonance of incoming noise.

Review of the best soundproofing materials

Rock Wool Acoustic Butts

In first place we can put Rockwool Acoustic Butts, a group of companies that have been producing basalt fiber slabs for the eighth decade. Stone wool, pressed into panels, has found its use in both residential and industrial construction as a heat and sound insulator.

Advantages of Rockwool Acoustic Butts:

  • High sound absorption class (A/B depending on thickness), excellent sound absorption ability: air vibrations up to 60 dB, shock – from 38.
  • Low thermal conductivity and complete fire safety.
  • Vapor permeability, moisture resistance, biostability, durability.
  • Certification according to Russian Federation and EU standards.
  • Easy to install.

Flaws:

There is a risk of purchasing a fake.

High cost, largely due to the need to use additional components and waste accounting.

Soundproofing

These are membrane-type bitumen-polymer soundproofing materials based on modified resins, which have sound, heat and waterproofing qualities. Applicable for walls, ceilings and floors, including “warm” ones using a floating system. Included in category G1 - low-flammable.

Positive properties:

  • Versatility, durability, affordable price.
  • Water, bio and temperature resistance (-40/+80°C).
  • Low degree of thermal conductivity in accordance with SNiP 23-02-2003.
  • Sound protection for airborne noise up to 28 dB, for shock – up to 23.

Negative:

  • A small dealer network in the Russian Federation.
  • The elements have considerable weight, and therefore cannot be named the best option for weak load-bearing foundations.
  • There is only one installation method allowed - adhesive.
Tecsound

The company produces polymer-mineral membrane soundproofing materials. These are flexible, elastic roll products, very dense, which is why they are classified as heavy. The basis is aragonite and elastomers. Belongs to classes G1 and D2 - low flammability, with an average degree of smoke formation.

Advantages:

  • Resistance to rotting, moisture and temperature resistance (properties do not change even at t°-20), durability.
  • Versatility due to the property of stretching.
  • Certification according to Russian and European standards.
  • Environmental safety due to the absence of phenol-containing substances.
  • Reduction of airborne noise up to 28 dB.

Flaws:

  • Possibility of installation - only adhesive.
  • Not applicable as an independent material for sound insulation.

The cost is above average.

Schumanet

Mineral wool boards of the Schumanet series are designed for wall and ceiling frame soundproofing systems for subsequent finishing with facing materials (plywood, plasterboard or fiber sheets, chipboard).

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  • Resistance to humidity, formation of mold and mildew, durability.
  • Excellent vapor permeability and minimal thermal conductivity.
  • Complete fire safety and non-flammability - classes KM0 and NG.
  • Compliance with high sound absorption classes - A/B at any frequency, reduction of structural and airborne noise waves from 35 dB.
  • Russian Federation certification.
  • Easy to install due to its elastic properties.

Flaws:

An increased degree of phenol emission (slightly exceeds the permissible limit), that is, environmental friendliness is in question.

High cost due to the need to purchase many additional items. elements, the need to strictly follow the installation instructions.

ZIPS panels

The panel system from the manufacturer Acoustic Group appeared at the very end of the last century. This is a multi-layer structure, the composition of which varies depending on its purpose. For ceiling and wall surfaces, tongue-and-groove plasterboard sheets are used as a base, and for floor surfaces, gypsum fiber sheets are used. They are supplemented with fiberglass or basalt slabs. To a large extent, vibration units made of polymer and silicone prevent the transmission of vibration and noise waves. Flammability degree G1 (low flammability).

Advantages:

  • Durability, efficiency and biostability.
  • Low thermal conductivity.
  • The absence of inter-plate gaps during installation is ensured by the tongue-and-groove type of connection.
  • There is no need to use adapters when attaching plates.
  • Compliance with GOST requirements.

Flaws:

When mounted on a wall, the slabs can resonate by 2-3 dB with incoming and outgoing low-frequency noise up to 100 Hz.

During the installation process, many components are required, which significantly increases the final cost of installation.

SoundGuard Plates

A fairly effective product, attractive at an affordable price, produced by an alliance of experienced manufacturers who have been known on the Russian market for many years. Prefabricated noise protection structure includes:

  • Drywall Volma,
  • SoundGuard profiled board (consists of plasterboard with mineral-quartz filler and a cardboard cellulose panel),
  • Frame profile.

According to the degree of flammability, they belong to group G2 (moderately flammable), toxicity T1 (low). The advantages of SaunGuard panels include:

  • Compliance with all safety requirements and certification of the Russian Federation.
  • Versatility - the slabs are suitable for any wall and floor bases.
  • Minimum thermal conductivity.
  • Good sound insulation performance (airborne noise - up to 60 dB, shock - up to 36).
  • Easy installation, the ability to choose the installation method (adhesive, frame, using plastic dowels).

    • Disadvantages:

    • Lack of moisture resistance properties.
    • There are few sales representatives in Russia.
    • High prices.
    • During the cutting process, the mineral filler is shed. This necessitates the need to cover the edges of all slabs with tape or tape.

    In addition, if the panels are used as an independent sound insulator, then the degree of interference with impact and airborne noise does not exceed 7 dB. Like ZIPS, panels can resonate with low-frequency noise.

    otdelkadom-surgut.ru

    Soundproofing of premises for various purposes – Acoustic Group

    Acoustic Group has been bringing peace and quiet to its clients' homes for over 18 years. We produce and sell materials designed to create a comfortable acoustic environment. Our specialization is sound insulation in apartments, offices, and factories, a wide range of vibration insulation tasks, and acoustics of premises for various purposes, including theaters, concert and sports halls, as well as cinema halls. Our acoustic engineers are ready to solve almost any problem:

    • Acoustic design;
    • Measurements;
    • Expertise;
    • Consulting;
    • Project support.

    Our customers are not only corporate clients, but also private individuals. Most often they require soundproofing for an apartment. At the same time, we approach each case individually, understanding that universal recipes do not always work. Our task is to achieve the desired result, and not to sell a solution that is convenient for ourselves. Our portfolio includes many different projects, from small apartments and country houses to world-famous concert and theater halls.

    Acoustic Group - professional soundproofing and soundproofing of apartments, offices, premises for various purposes with guaranteed results

    A lot depends on acoustic parameters: the sound quality of audio equipment, the penetration of street noise or noise from neighbors and, ultimately, the comfort of staying in the room. To create a calm and comfortable atmosphere, our engineers have developed and introduced unique materials into production. Soundproofing solutions from Acoustic Group for floors, walls and ceilings have been time-tested and, nevertheless, are constantly being improved and updated. All Acoustic Group products are certified and meet the most stringent quality standards.

    We offer sound insulation solutions for walls and ceilings:

    Frameless systems. Modern sound insulation using ZIPS sandwich panels. Effective, high quality, the thinnest of those that actually work. At the same time, it is quickly and easily installed. They provide ADDITIONAL sound insulation for airborne noise at a level of 9-18 dB (depending on the chosen design).

    Frame systems. Thicker. However, they are also effective. They are made using the Gyproc Ultrastil metal profile, Vibroflex vibration suspensions, special weighted plasterboard Aku-Line, acoustic plates Shumanet-ECO, SK or BM. Provide reliable protection premises from external noise.

    Sound insulation of the room: floor materials

    • Shumanet-100Combi and 100Hydro - under the screed, to comply with impact noise standards (can be used in several layers to enhance the effect).
    • Noise stop C2 and K2 - under the screed, for maximum sound insulation in terms of impact and airborne noise.
    • Shumoplast - under the screed, for uneven floors.
    • Akuflex underlay for finishing coatings to protect neighbors from impact noise.
    • Vibrostek-M, Sylomer SR, Shumanet-EKO, SK or BM, Vibrosil - for floor structures on joists.

    Soundproofing of premises: materials for walls and ceilings

    • ZIPS-III-Ultra, ZIPS Vector, ZIPS Module, ZIPS Cinema - sandwich panels for frameless sound insulation.
    • Acoustic triplex Soundline-dB
    • Soundproofing panels Soundline-PGP Super for thin partitions
    • Special weighted gypsum board Aku-Line
    • Vibroflex suspensions and wall mounts
    • Acoustic slabs Schumanet EKO, BM, SK

    Vibration isolation: materials

    • Sylomer SR is a polyurethane elastomer with a wide range of applications.
    • Isotop - spring vibration isolators.
    • Vibroflex suspensions 1/30 M8 and 4/30 M8.
    • Vibroflex SM vibration isolation supports.
    • Mastic Vibronet.

    Proper acoustics in a room can be achieved by creating decorative and acoustic materials that not only provide aesthetic appeal, but also allow you to adjust the acoustic characteristics.

    Advantages of Acoustic Group:

    • Impeccable quality. Only proven effectiveness, many years of implementation experience and positive customer reviews.
    • Reasonable cost of materials. Sound insulation for an apartment is a rather expensive item in the renovation estimate. However, our price for materials, upon detailed calculation, turns out to be not only justified, but also one of the best on the market.
    • Full range of services. We don't just supply materials. Our engineers are ready for comprehensive work on site from the design stage to the moment of commissioning of the facility, carrying out all the necessary acoustic measurements.
    • Wide geography. Our products are available throughout Russia, as well as in the CIS countries. You can buy it directly at Acoustic Group sales offices or from the company’s partners. You can directly order soundproofing of your apartment from us in Moscow, Kyiv, Minsk, Almaty and many other cities.

    www.acoustic.ru

    Acoustic design - Basics of acoustics

    The well-known confusion in understanding the principles of formation of the bass section of acoustics is largely due to the information policy of advertising, and often reference publications. There, the potential buyer is first told the size of the speaker, then its power, then the mythical “frequency range” and ends with the winning price.

    All? Not so! This is where it all begins. In English, the speaker itself is called driver - drive, and this is very correct. Just as an engine will become a car only by enriching itself with everything that humanity has developed for this, so a speaker will become a loudspeaker only in its inherent acoustic design.

    With high-frequency and mid-frequency heads the situation is relatively simple: the high-frequency heads carry their own acoustic design, while the mid-range heads require minimal dimensions.

    Bass players are a different matter. Here, almost everything is determined by the choice of acoustic design, and depending on this choice, all the parameters communicated to you will be subject to revision: power, frequency range, and, in a certain sense, price. Because with skillful selection of parameters, you can achieve the sickening sound of the most expensive and thoroughbred bass speaker.

    Now it’s time to “announce the entire list.” It's not that long:

    The task of any low-frequency acoustic design is solved according to the ancient principle of “divide and conquer”. “Separate” means that the vibrations emitted by one side of the diffuser must be somehow separated from the vibrations created by its opposite side, simultaneously and in antiphase with the first. “Conquer” means that the “extra” sound waves cut off in this way can be dealt with in different ways.

    Historically, the first acoustic design was an acoustic screen. It holds the defense, preventing oscillations from one side of the diffuser to the other and preventing them from mutually destroying up to frequencies at which the shortest distance between the front and reverse side diffuser will become comparable to the half-wavelength of the emitted frequency. And below this frequency, the acoustic screen “becomes completely incapable” and allows antiphase waves to cancel each other out as they please. To suppress an acoustic short circuit at a frequency of, say, 50 Hz, the shield must have a size of 3 meters by 3. Therefore, this type of acoustic design has long lost its practical significance, although it is still used as a reference when measuring speaker parameters.

    Structurally, the simplest acoustic design of those practically used is closed box (sealed or closed in foreign terminology). Here, unnecessary vibrations are dealt with decisively and abruptly: locked in a confined space behind the diffuser, they will sooner or later fade away and turn into heat. The amount of this heat is tiny, but in the world of acoustics everything is in the nature of small disturbances, so how this thermodynamic exchange occurs is not indifferent to the characteristics of the acoustic system. If the sound waves inside the speaker housing are allowed to dangle unattended, a significant part of the energy will be dissipated in the volume of air contained inside the housing, it will heat up, albeit slightly, and the elasticity of the air volume will change, and in the direction of increasing rigidity. To prevent this from happening, the internal volume is filled with sound-absorbing material. While absorbing sound, this material (usually wool, natural, synthetic, glass or mineral) also absorbs heat. Due to the significantly greater heat capacity of sound-absorbing fibers than air, the temperature increase becomes much smaller and it “seems” to the speaker that there is a significantly larger volume behind it than in reality. In practice, in this way it is possible to achieve an increase in the “acoustic” volume compared to the geometric one by 15 - 20%. This, and not at all the absorption of standing waves, as many believe, is the main point of introducing sound-absorbing material into closed loudspeakers.

    A variation of this (and not the previous one, as is often believed) type of acoustic design is the so-called “ endless screen" In English-language sources, this type of design is called infinite baffle or free-air. All the names given are equally misleading. We are all adults here and we understand that in practice there cannot be an endless screen. In fact, an infinite screen is considered to be a closed box with a volume so large that the elasticity of the air enclosed inside it is much less than the elasticity of the diffuser suspension, so that the speaker simply does not notice this elasticity and the characteristics of the speaker system are determined only by the parameters of the head. Where the boundary lies, starting from which the volume of the box becomes seemingly infinite, depends on the parameters of the speaker. However, when solving practical problems, this volume always turns out to be the internal volume of the trunk, which, even in a small car, will give the reaction of an “infinitely large” volume even for a large speaker. Another thing is that not every speaker will work well in such a design, but we will discuss this separately when we talk about choosing a speaker for an acoustic design (or vice versa).

    Despite all the (by the way, apparent) simplicity of a closed box as an acoustic design for the low-frequency section of car acoustics, this solution has many advantages that are absent in other, more sophisticated designs.

    Firstly, the simplicity (or simplicity) of calculating characteristics. A closed box has only one parameter - internal volume. You can choose the right one if you try! The margin for errors here is reduced to a minimum.

    Secondly, over the entire frequency range, down to zero, the vibrations of the diffuser are restrained by the elastic reaction of the air volume inside the box. This significantly reduces the likelihood of speaker overload and mechanical damage. I don’t know how comforting this sounds, but for avid bass lovers, the speakers in closed boxes sometimes burn, but almost never “spit out”.

    Thirdly, only the closed box is a second-order acoustic filter, that is, it has a drop in frequency response below the resonance frequency of the head-box system with a slope of 12 dB/oct. Namely, the frequency response of the interior volume of a car, below a certain frequency, has precisely this steepness, only in the opposite sign. If you guess, calculate or measure (depending on what happens), it becomes possible to obtain a perfectly horizontal frequency response at lower frequencies.

    Fourthly, with the right choice of head parameters and volume for it, a closed box has no equal in the field of impulse characteristics, which largely determine the subjective perception of bass notes.

    The natural question now is - what’s the catch? If everything is so good, why are all other types of acoustic design needed?

    There is only one catch. Efficiency For a closed box it is the smallest compared to any other type of acoustic design. Moreover, the smaller we manage to make the volume of the box, while maintaining the same operating frequency range, the less effective it will be. There is no more insatiable creature in terms of power input than a closed box of small volume, which is why the speakers in them, as was said, although they do not spit out, they often burn...

    The next most common type of acoustic design is bass reflex(ported, vented, bass-reflex), more humane in relation to the radiation from the rear side of the diffuser. In a bass reflex, part of the energy that is “put against the wall” in a closed box is used for peaceful purposes. To do this, the internal volume of the box communicates with the surrounding space through a tunnel containing a certain mass of air. The size of this mass is chosen in such a way that, in combination with the elasticity of the air inside the box, it creates a second oscillatory system that receives energy from the back side of the diffuser and radiates it where needed and in phase with the radiation of the diffuser. This effect is achieved in a not very wide frequency range, from one to two octaves, but the efficiency is within its limits. increases significantly, according to the principle “no waste - there are unused resources.” In addition to higher efficiency The bass reflex has another important advantage - near the tuning frequency, the amplitude of the diffuser oscillations significantly decreases. This may at first glance seem like a paradox - how the presence of a hefty hole in the loudspeaker cabinet can restrain the movement of the cone, but nevertheless it is a fact of life. In its operating range, the bass reflex creates completely greenhouse conditions for the speaker, and exactly at the tuning frequency the oscillation amplitude is minimal, and most of the sound is emitted by the tunnel. The permissible input power is maximum here, and the distortion introduced by the speaker is, on the contrary, minimal. Above the tuning frequency, the tunnel becomes less and less “transparent” to sound vibrations, due to the inertia of the air mass contained inside it, and the loudspeaker acts as if it were closed. Below the tuning frequency, the opposite happens: the inertia of the speaker gradually disappears and at the lowest frequencies the speaker operates practically without load, that is, as if it had been removed from the housing. The amplitude of oscillations quickly increases, and with it the risk of spitting out the diffuser or damaging the voice coil from hitting the magnetic system. In general, if you do not take precautions, going for a new speaker becomes a real prospect.

    A means of protecting against such troubles, in addition to being careful in choosing the volume level, is the use of infra-low-pass filters. By cutting off the part of the spectrum where there is still no useful signal (below 25 - 30 Hz), such filters prevent the diffuser from going into disarray at the risk of your own life and your wallet.

    Bass reflex significantly more capricious in the selection of parameters and settings, since three parameters are subject to selection for a specific speaker: box volume, cross-section and tunnel length. The tunnel is very often made so that with a ready-made subwoofer it is possible to adjust the length of the tunnel by changing the tuning frequency.

    Due to the presence of two interconnected oscillatory systems, the bass reflex is a fourth-order acoustic filter, that is, its frequency response theoretically has a roll-off of 24 dB/oct below the tuning frequency. (Actually, from 18 to 24). It is almost impossible to obtain a horizontal frequency response when installed in a cabin. Depending on the ratio of the size of the cabin (and, therefore, the characteristic frequency from which the rise in the frequency response of the internal acoustics begins) and the tuning frequency of the bass reflex, the total characteristic may have deviations from a delicate hump to crazy Amur waves. The hump, that is, a smooth rise in the frequency response by lower frequencies is often just what is needed for optimal subjective perception of bass in a noisy space, but sharp changes in amplitude due to an unsuccessful choice of parameters have earned the bass reflex, completely undeservedly, the nickname boom-box (“booze”). To restore justice, we note that the thumping effect can be achieved from a closed box - I’ll explain how next time; and a properly designed bass reflex can produce very clear and musical bass with a reasonable power input.

    A type of bass reflex design is passive radiator loudspeaker(or radiator). Foreign terms: passive radiator, drone cone. Here, the creative oscillatory system, which makes it possible to utilize the energy removed from the rear side of the diffuser, is implemented not in the form of a mass of air in the tunnel, but in the form of a second diffuser, not connected to anything, but weighted to the required mass. At the tuning frequency, this diffuser oscillates with the greatest amplitude, and the main one with the smallest. As they move up in frequency, they gradually change roles. Until recently, this type of acoustic design was not used in mobile installations, although it is used quite often at home. The reason for the dislike was the unjustified hassle of obtaining a second diffuser (this is usually the same speaker, but without a magnetic system and voice coil) and difficulties in placing two large diffusers where a conventional bass reflex would need to place a diffuser and a small tunnel. However, recently, car subwoofers with passive radiators have appeared - need forced them. The fact is that recently a new generation of speakers with a very large diffuser stroke, designed to work in small volumes, have begun to appear. The volume of air “blown out” by them during operation is very large, and the tunnel would have to be made significant in diameter (otherwise the air speed in the tunnel will increase so much that it will hiss like a steam locomotive). And the combination of a small volume and a large tunnel diameter makes it necessary to choose a longer length for the tunnel. So it turned out that bass reflexes of a conventional design for such heads would be decorated with meter-long pipes. To avoid such unnecessary incidents, we preferred to concentrate the required oscillating mass in a passive radiator with a diffuser stroke the same as that of an active speaker.

    The third type of subwoofer, quite often used in auto installations (although less frequently than the previous two) is bandpass loudspeaker. Sometimes the name “balanced-load loudspeaker” () is used. If a closed box and a bass reflex are acoustic high-pass filters, then a band-pass filter, as the name implies, combines high- and low-pass filters.

    The simplest bandpass loudspeaker is single 4th order(single reflex). It consists of a closed volume, the so-called. rear chamber and a second one, equipped with a tunnel, like a conventional bass reflex (front chamber). The speaker is installed in the partition between the chambers so that both sides of the diffuser operate in completely or partially closed volumes - hence the term “symmetrical load”.

    Of the traditional designs, the bandpass loudspeaker, in any version, is the champion in efficiency. Moreover, efficiency is directly related to bandwidth. The frequency response of a bandpass loudspeaker has the shape of a bell. By selecting the appropriate volumes and frequency tuning of the front chamber, it is possible to build a subwoofer with a wide bandwidth, but limited output, that is, the bell will be low and wide, or it can be with a narrow bandwidth and very high efficiency. in this strip. At the same time, the bell will stretch in height.

    Bandpass- a capricious thing to calculate and the most labor-intensive to manufacture. Since the speaker is buried inside the case, it is necessary to go to some lengths to assemble the box so that the presence of a removable panel does not violate the rigidity and tightness of the structure. Coordinating the frequency characteristics of the subwoofer, interior and front speakers is also associated with a well-known headache. The impulse characteristics are also not the best, especially with a wide bandwidth. How is this compensated?

    First of all, as stated - the highest efficiency.

    Secondly, the fact that all sound is emitted through the tunnel, and the speaker is completely closed. When assembling such a subwoofer, considerable possibilities open up for an installer (or amateur) with imagination. It is enough to find a small place at the junction of the trunk and the passenger compartment, where the mouth of the tunnel can be placed - and the path is open to the most powerful bass. Especially for such installations, JLAudio, for example, produces flexible plastic tunnel sleeves, with which it proposes (and many agree) to connect the subwoofer output to the cabin. Like a vacuum cleaner hose, only thicker and stiffer.

    Strip strips are even more effective 6th order loudspeakers with two tunnels. The chambers of such a subwoofer are adjusted at intervals of approximately an octave. A double bandpass provides less distortion in the operating band, since the speaker is loaded with bass reflexes on both sides of the diffuser, with all the advantages of such a load, but has a steeper frequency response decline below the operating band compared to a single bandpass.

    An intermediate position is occupied by the so-called quasi-bandpass loudspeaker, aka – with a sequential setting, where rear camera is connected by a tunnel to the front, and the front by another tunnel to the surrounding space.

    Three-chamber bandpass loudspeakers are simply alternative design implementations of conventional bandpass loudspeakers, and are composed of two conventional ones, after which the wall separating them has been removed.

    There are three more options for the acoustic design of low-frequency acoustics, which, although they exist, are practically not used. The first of the outsiders - acoustic labyrinth, where “energy removal” from the back of the diffuser occurs through a long pipe, usually folded for compactness, but still increasing the dimensions of the subwoofer to limits that are unacceptable in a mobile installation.

    Second - exponential horn, which, in order to obtain a sufficiently low cut-off frequency, must have cyclopean dimensions, which makes its use in the low-frequency link rare, even in stationary systems where there is more space than in a car.

    The third type, which has isolated precedents for use, is loudspeaker with aperiodic load in the form of a concentrated acoustic impedance (aperiodic membrane). We used to call it PAS - acoustic absorption panel. The idea is that the load for the diffuser is a nearby semi-permeable barrier, for example, dense fabric or a layer of silica wool sandwiched between perforated panels. Theoretically, such a load is inelastic in nature and, like a shock absorber in a car suspension, absorbs acoustic energy without affecting the resonant frequency of the speaker. But this is theoretical. But in practice, the presence of an air volume between the speaker and the PAS created such a mixture of characteristics and reactions that the results became difficult to predict.

    So, from a quick glance at the main types of acoustic design, it is clear that there is no perfection in the world. Any choice will be a compromise. And to make the essence of the compromise clearer, let's end this correspondence meeting as it should be - by summing up the interim results. Let's compare the considered options in terms of the main factors that determine the success of their use in a mobile audio installation.

    These factors should include:

    Efficiency

    The magnitude of the efficiency inherent in a particular type of acoustic design ultimately determines how much powerful amplifier will be needed to achieve the required volume level, and at the same time how difficult the life of the speaker will be.

    In the most important frequency range from the point of view of reproducing information in the bass register, 40 - 80 Hz, places will be distributed as follows: narrow-band bandpass loudspeakers are champions in this category, especially double-tunnel 6th order ones. They are followed by a wideband dual-tunnel and a conventional bass reflex. And finally, the ones that are most hungry for power input are a closed box and a wideband single bandpass.

    Introduced distortion

    In the lower octave - one and a half musical range (30 - 80 Hz) all types of acoustic design behave decently at low power levels. The bass reflex and bandpass loudspeaker are somewhat better than others, but not by much. But when high capacities opponents stretch along the distance. The best results here should be expected from a dual bandpass loudspeaker. Behind it is a single bandpass and bass reflex. And it completes the circuit - a closed box, which produces the greatest distortion at large signal amplitudes.

    Impulse characteristics

    Accurate reproduction of the fronts of bass instruments is perhaps the main quality for bass acoustics. Low bass efforts are of little use if they are blurred and sluggish. In this regard, a closed box promises the best results (if calculated correctly). The transient characteristics of a bass reflex can be very decent, but still on average will be inferior to a closed design. Single bandpass loudspeakers have good performance, which, however, deteriorates as the bandwidth increases. The worst response to a pulsed signal has a dual bandpass loudspeaker, again, especially a wideband one.

    The work of the subwoofer should be, starting from a certain frequency, delegated to the midbass of the front speakers. For a closed box and a bass reflex, this is not a problem and the system designer has a fair amount of freedom in choosing the crossover frequency, since both this frequency and the slope of the rolloff are determined by external circuits. But narrowband bandpasses often have their own frequency rolloff starting from 70-80 Hz, where not all midbass can painlessly pick up a song. At the same time, the requirements for midbass become more complicated, and working with a crossover does not become any easier.

    Let’s put all of the above in a table, based on our usual five-point system:

    Bandpass loudspeaker
    single double
    Closed box Bass reflex Narrow band Wide band Narrow band Wide band
    Distortion at low power 4 5 5 4 5 4
    Distortion at high power 2 4 4 3 5 4
    Impulse characteristics 5 4 4 2 3 2
    Coordination with front speakers 5 5 2 4 2 4
    Overload capacity in the operating range (above 30 Hz) > 4 5 4 5 4
    Overload capacity in the infra-low frequency range below 30 Hz) 5 2 5 5 2 2
    Smoothness of the frequency response taking into account the internal acoustics of the car. 5 4 2 3 2 3
    Sensitivity to design and manufacturing errors 5 4 2 2 2 2

    baseacoustica.ru

    Room acoustics - sound absorption - Paroc.ru

      Products

      Construction insulation

      General construction thermal insulation

      PAROC eXtra

      PAROC eXtra light

      PAROC eXtra plus

      PAROC eXtra Smart

    Thermal insulation of walls

    PAROC InWall

    PAROC WAB 10t

    PAROC WAS 120

    PAROC WAS 25t

    PAROC WAS 35

    PAROC WAS 35t

    PAROC WAS 35tb

    PAROC WAS 50

    PAROC WAS 50t

    Windproof insulation

    PAROC WPS 1n

    PAROC WPS 3n

    Thermal insulation of plaster facades

    PAROC Fatio

    PAROC Linio 10

    PAROC Linio 15

    PAROC Linio 18

    PAROC Linio 20

    PAROC Linio 80

    Thermal insulation for sandwich panels

    PAROC COS 5

    PAROC CES 50C

    PAROC CES 50CS100

    PAROC COS 10

    Thermal insulation of flat roofs

    PAROC ROB 60

    PAROC ROB 80

    PAROC ROB 80t

    www.paroc.ru

    Soundproofing and sound-absorbing materials

    What is the difference between sound insulation and sound absorption?

    Sound insulation is measured in decibels, a term used when we're talking about about reducing the volume of outgoing/incoming noise.

    Sound absorption is assessed by calculating the sound absorption coefficient and is measured from 0 to 1 (the closer to 1, the better). Sound-absorbing materials absorb sound inside the room and dampen it, resulting in the disappearance of echoes.

    If you need to get rid of the noise from your neighbors, you need soundproofing materials. If you need the absence of echo in the room, sound-absorbing ones.

    How to reduce noise from neighbors above/below/behind the wall? Is it possible to rid them of my noise?

    Soundproofing the ceiling is obviously a losing option. The maximum reduction that can be achieved is from 3 to 9 dB. Try to come to an agreement with your neighbors and soundproof the floor for them, then you will achieve a reduction of up to 25-30 dB!

    The sound insulation of a wall depends on the type of wall. They are either under construction or already existing (between rooms and apartments). For erected walls, immediately make double, independent frames. The thicker and more multi-layered the wall, the higher the chance of achieving a noise reduction of 50-60 dB in the apartment.

    For existing walls, either make a frame filled with soundproofing materials, but be prepared for it to “eat up” 10 cm of space. Or, if space is limited, attach soundproofing panels or roll material directly to the wall.

    To soundproof the floor, place materials such as TOPSILENT DUO or FONOSTOP BAR under the screed. If it is not possible to raise the floor under the screed by 10 cm, then lay soundproofing materials under the floor covering. Please note that in this case the noise will decrease by no more than 10-15 dB.

    Try to ensure that the screed and flooring do not come into contact with the walls of the premises. The “floating” design provides better sound insulation properties. Conversely, if the soundproofing layer extends a couple of centimeters onto the walls, this will additionally dampen the sound waves.

    We made repairs, didn’t think about soundproofing and now we hear noise from our neighbors, how can we fix it?

    Unfortunately, you will have to make changes to repairs that have already been made.

    If soundproofing of the floor is necessary, remove the laminate (or other finishing coating) and lay the FONOSTOP DUO soundproofing membrane underneath.

    If there are walls, then, as mentioned above, the covering must be removed, a frame must be made and a material like TOPSILENT BITEX must be glued. Likewise for the ceiling.

    What materials should be used to soundproof an apartment? How many do you need? How to calculate the required quantity?

    Soundproofing an apartment requires an integrated approach. A structure is assembled, a “sandwich” of several materials. The thickness of a high-quality structure is about 7-10 centimeters.

    To calculate the required quantity, send the dimensions of the room - length, width and height, the manager will make the calculation and tell you what materials will be needed.

    What materials are needed for a recording studio?

    For a recording studio, both types of materials are important and needed - soundproofing and sound-absorbing. First of all, high-quality sound in a studio is achieved through the use of sound-absorbing, acoustic panels made of melamine foam or open-cell polyurethane. The cellular structure of the material “quenches” sound vibrations. We recommend using thick panels up to 100 mm, this will ensure sound absorption in a wide range of frequencies. In addition, install “bass traps” up to 200-230 mm thick.

    With sound insulation, everything is simple - more layers and it is advisable to use two-layer materials with a lead layer, for example, AKUSTIK METAL SLIK.

    Which sound insulation is better?

    The best material is the one that solves the problem. The same soundproofing materials manifest themselves differently depending on the volume, type of walls, and ceiling of the room. We recommend that you consult with a specialist before you begin any repairs.

    How is soundproofing and sound-absorbing materials installed?

    The easiest way is to attach sound-absorbing acoustic panels. Take any type of glue and attach it wherever you need it. The material is light and easily adheres to the surface.

    For the installation of soundproofing materials, specially designed adhesives are used - OTTOCOLL P270 (for floors) and FONOCOLL (for walls and ceilings).

    Do you deliver materials? Is there pick-up?

    Yes, we deliver. Choose a convenient delivery method: pickup from a warehouse in Lyubertsy, delivery by van within the Moscow Ring Road and Moscow region (up to 100 km) or a transport company if you are far from Moscow.

    Where can I see prices?

    The price list for soundproofing and sound-absorbing materials is in the “Price Lists” section.

    www.riwa.ru

    Vertical sound-absorbing materials for improved acoustics

    To create an optimal sound environment It is necessary to use different types of sound absorbers. A sound-absorbing ceiling significantly reduces the sound pressure level and sound propagation in the room. However, bare walls will create an echo effect.

    Vertical sound absorbers reduce echo and improve speech intelligibility so you can hear what people say clearly.

    Required number of vertical sound absorbers will depend on the characteristics of the premises itself and the type of activity carried out in it:

    In open offices It is important to prevent the spread of speech and noise so that it does not disturb employees.

    In schools Students need a supportive learning environment that allows them to hear the teacher and each other well and have the opportunity to think in silence.

    In medical institutions patients need peace to rest and recover, and staff also need to be able to communicate.

    Read more in the “Acoustic Solutions” section.

    Acoustic parameters and their application

    Reverberation time (RT) is the most commonly used parameter for calculations and measurements in room acoustics. The Sabin formula or its derivatives are also commonly used. This formula is easy to use, since you only need to know the volume of the room and the amount of sound-absorbing material, calculated through the statistical sound absorption coefficient αp.

    However, these formulas are suitable for ideal conditions with diffuse sound fields. In reality, the sound field is far from uniform. It can be represented in the form of two fields: non-diffuse and diffuse.
    Non-diffuse sound field Diffuse sound field


    Non-diffuse sound fields are predominantly located in the mid- and high-frequency region and contain sound energy that is distributed in a plane parallel to the sound-absorbing surface (usually the ceiling). The reverberation time in a room is determined by the non-uniform sound field. This means that the practical value of reverberation time is significantly higher than the theoretical value calculated for a diffuse sound field.

    The best way to reduce energy non-diffuse sound fields is sound absorption by wall-mounted sound absorbers. Sound energy can also be redirected to a sound-absorbing suspended ceiling by reflection or dispersion from furniture, equipment, and room cladding.

    Breaking up the sound-absorbing area into small elements interspersed with a solid surface will increase diffusion and slightly reduce reverberation time.

    Additional benefits of vertical sound absorbers

    In many rooms for good acoustics it is necessary to reduce the noise level. The more sound-absorbing material, the correspondingly lower the noise level. Scientists have proven that reducing sound pressure levels (lower noise levels) in a room leads to a decrease in psychological stress - people begin to speak more quietly.

    For rooms where Speech intelligibility is a priority, and C50 is more important than reverberation time. Although STI is partially dependent on reverberation time, it correlates better with the amount of sound-absorbing material in the room. Adding sound-absorbing panels to walls reduces reverberation time and improves speech privacy, which also results in lower sound pressure levels.

    By the number of sound-absorbing materials The level of speech privacy and the level of sound pressure reduction can be calculated, but the reverberation time (RT) cannot be calculated, depending only on the amount of sound-absorbing materials.

    Practical solutions with vertical acoustics

    The main three factors that should be taken into account when installing sound-absorbing wall panels in a room are:

      area that can be lined with sound absorber

      mechanical strength requirements

      aesthetic requirements

    The first and easiest way is partial covering of walls with wall panels. From an acoustic point of view, it is best to install wall panels on two adjacent walls to avoid the effect of fluttering echoes.

    Another way to install wall panels- break them into small sections and distribute them evenly along the wall. This can be done either geometrically or in any order. This way you can create your own unique design.

    Another simple and functional way to place sound-absorbing material in classrooms or offices - installing a horizontal belt of wall panels at a height convenient for human height and using them as an information board. In this case, it is also preferable to install panels on at least two walls in combination with a sound-absorbing ceiling.

    Concrete floor in the garage - what brand, thickness of the concrete screed, how to concrete it correctly and inexpensively, how to make it and level it, foundation structure
    The quality of sound that is acceptable and preferable to the ear depends almost entirely on what the listener is accustomed to.

    Very few people with trained ears can judge sound quality with reasonable accuracy and in objective terms.

    The weakest link in the sound path is most often the speaker system. And this is no coincidence. Designing it is a technically very difficult task associated with many physical limitations. The main problem is usually the reproduction of the lowest frequencies of the audio range. At these frequencies, the loudspeaker must emit sound waves of sufficiently long length. If at a frequency of 300 Hz the length sound wave is a little more than a meter, then at a frequency of 30 Hz it is already 11 meters. The speaker cone, moving forward, creates a compression wave. But at the same time, a vacuum wave appears on the back side of the diffuser, and if the speed of the diffuser is low, then the air simply flows from the front side of the diffuser to the back without creating a sound wave in the surrounding space. A so-called acoustic short circuit occurs.

    The easiest way to improve the reproduction of low sound frequencies is to place the loudspeaker head on an acoustic shield - a shield big size. The screen operates effectively as long as the distance from the front side of the diffuser to the back, measured around the edge of the screen, is more than half the sound wavelength, i.e. for the 30 Hz frequency we mentioned, you need a screen with a side size of 5.5 meters. Of course, if you really want to actually reproduce this frequency, you can drill a hole in the wall separating two adjacent rooms and insert a loudspeaker head into this hole. But seriously? Let's try to bend the edges of the screen. The result is a box without a back wall. You can make the box larger, and those low frequencies that are still poorly reproduced can be “raised” in the amplifier audio frequency. So, at one time, they did it to lower the range of reproduced frequencies to 70 - 60 Hz.

    Modern speaker systems are made with a closed back wall and are treated inside with sound-absorbing material. This eliminates acoustic short-circuiting at low frequencies and improves playback quality at mid frequencies. However, low efficiency. The head of the loudspeaker, which is known to be even lower than that of a steam locomotive, is halved when using a closed box. Designers have to solve a number of problems associated with increasing the output of loudspeaker heads.

    This is why high-quality speaker systems are so complex and expensive.

    The design of the speaker system, at first glance, looks deceptively simple. Two or more loudspeaker heads installed in wooden box and connected by wires to the amplifier. However, it is a deep misconception to believe that several heads installed in a box can serve as an acoustic system for high-quality sound reproduction.

    A loudspeaker head installed in a box that acts as an acoustic design is called a loudspeaker. An acoustic system is a loudspeaker that contains one or more drivers that emit sound in different areas of the audio frequency range. Loudspeaker heads are divided into low-frequency, mid-frequency, high-frequency and full-range.

    Depending on the type of electroacoustic converter of an electrical signal into air vibrations surrounding the head, heads are electrostatic, electromagnetic, piezoelectric, plasma and electrodynamic. The most widespread are electrodynamic loudspeaker heads.

    The electrodynamic moving coil loudspeaker was first invented and patented in 1925 by General Electric and has not undergone fundamental changes since then.

    Any electrodynamic head of a moving system, magnetic system and diffuser holder. In turn, the moving system consists of a diffuser, an external suspension, a centering washer and a voice coil.

    Diffuser is the main element of the mobile system. Diffusers of low-frequency heads always have a cone shape. Mid-frequency and high-frequency heads can have diffusers either in the form of a cone (cone heads) or in the form of a sphere (dome heads). Cone head diffusers are made by casting from paper pulp with various additives (wool, cotton, etc.) introduced to obtain the necessary physical and mechanical properties, on which the sound quality largely depends. Recently, diffusers made of synthetic materials, in particular polypropylene, have found widespread use in the production of heads. Some companies use metal alloys for the manufacture of cone head diffusers, and also use layered structures consisting of several layers made of materials with different physical and mechanical properties. Such complex designs are used to improve the sound quality of loudspeakers. For this purpose, paper diffusers are impregnated with special compounds during the production process.

    There are diffusers with a rectilinear and curvilinear cone generatrix. Straight-line diffusers are easier to manufacture and were used in loudspeaker heads in the early years after their invention. In modern heads, diffusers are used exclusively with a curvilinear generatrix due to the absence in such diffusers of so-called parametric resonances, which cause extraneous sounds in the sound. To combat parametric resonances of the diffuser, many manufacturers apply a series of concentric grooves to the surface of the cone.

    Diffusers for dome heads are made by pressing from natural and synthetic fabrics, followed by impregnation with special compounds, as well as from synthetic films and metal foil. The second element of the movable system of the electrodynamic loudspeaker head is the external suspension, which is necessary for the progressive movement of the diffuser when the loudspeaker head is operating. The suspension can be made as a single unit with a diffuser in the form of a two- or multi-link corrugation, as well as in the form of a ring made of rubber, caoutchouc, polyurethane and other materials glued to the diffuser. Very stringent requirements are imposed on the suspension in terms of its elastic properties. The suspension must have sufficient flexibility and maintain linear elastic properties over the entire range of displacements of the moving system of the loudspeaker head. Fulfillment of the first condition is necessary to obtain a low frequency of the main (natural) resonance of the moving system of the loudspeaker head, which is very important for good reproduction of the lowest frequencies. The second condition must be met to ensure low nonlinear distortion. The fulfillment of the above conditions is achieved by using appropriate materials for the manufacture of the suspension and choosing its appropriate shape (shape and number of grooves, their height, etc.). Modern loudspeaker heads use suspensions that have an S-shaped, toroidal cross-section.

    Centering washer is the third element of the moving system that affects the quality of the loudspeaker head. Its purpose is to ensure the correct position of the voice coil in the air gap of the magnetic system of the head. To do this, the centering washer must have minimal flexibility in the radial direction and maximum possible flexibility in the axial direction. The fulfillment of the first condition is necessary to ensure the mechanical reliability of the head (the absence of the voice coil touching the walls of the gap of the magnetic system), the second - to ensure a low frequency of its main resonance. In addition, the centering washer must maintain linear elasticity characteristics throughout the entire range of movement of the movable system of the loudspeaker head. The amount of nonlinear distortion of the signal reproduced by the head depends on this. Centering washers can be made of textolite, cardboard, paper or fabric. Washers made of textolite, paper and cardboard, which became widespread in the 30-40s, are now completely replaced by corrugated washers of the so-called box type, made of cotton or silk fabric impregnated with bakelite varnish. By appearance such centering washers resemble a cylindrical box with a corrugated bottom and a cylindrical edge flared into a flat ring. The last element of the moving system of the electrodynamic loudspeaker head is the voice coil. The voice coil is wound with copper or aluminum wire in enamel insulation on a paper or metal frame and impregnated with varnish to prevent the turns from slipping. When current flows through the voice coil, an electromagnetic field is created around it, and when it interacts with the magnetic field created by the magnetic system of the head, a Lorentz force arises, which moves the voice coil and the diffuser attached to it in the axial direction. This is how sound is emitted from the head.

    Magnetic system is the most important structural unit of the electrodynamic head, largely determining its electroacoustic parameters. Back in the late 40s and early 50s, heads with electrical excitation were used, in the magnetic systems of which an electric coil called an excitation winding served to create a constant magnetic field. To power the field winding DC It was required to have special rectifiers with very good filtering of the rectified voltage. The field winding consumed significant power from the power source and generated a lot of heat when the head was operating. These and other shortcomings have caused the rapid displacement of heads with electromagnetic excitation by heads with permanent magnet excitation. Without exception, all modern electrodynamic heads have a permanent magnet magnetic system. Magnets come in core and ring types. The materials for the manufacture of core magnets are cobalt alloys and various grades of ferrites. Ring magnets are only ferrite. Most modern electrodynamic heads have ring ferrite magnets. Recently, special alloys with very good magnetic properties containing rare earth metals have been used to make magnets. This made it possible to significantly increase the sensitivity of the heads without increasing their overall dimensions and weight. The design of the magnetic system is determined by the shape of the magnet used. If the magnet has the shape of a ring, then the magnetic system consists of two annular flanges and a cylindrical core.

    The diameter of the core is smaller than the diameter of the hole in the upper flange. This creates an air gap in which the voice coil moves. When using a core magnet in the form of a solid or hollow cone, the magnetic system is a closed or semi-open magnetic circuit. A closed magnetic circuit consists of a steel cup, in the center of the bottom of which there is a magnet with a pole piece and an annular upper flange. The top flange hole and pole piece form an air gap that contains the voice coil. In a semi-open magnetic circuit, a metal bracket is used instead of a glass, and the upper flange has a rectangular shape. For the manufacture of cores, pole pieces and flanges, special grades of steel are used, the magnetic properties of which are subject to very stringent specific requirements. The shape of the pole pieces and the core has a significant impact on the magnitude of the magnetic induction in the air gap of the magnetic system of the head and the uniformity of the magnetic flux distribution in it. The sensitivity and level of nonlinear distortion of the head depends on this. The degree of heating, and therefore the thermal stability of the voice coil, depends on the size of the core and pole pieces, as well as on the size of the air gap. Therefore, in powerful low-frequency heads, pole pieces and cores of large diameter are used, and they also strive to increase the size of the air gap as much as possible (as the gap increases, the sensitivity of the head decreases and to preserve it, the use of a more powerful magnet is necessary). Recently, to improve the cooling of the voice coil, some companies have begun to produce heads with the air gap of the magnetic system filled with a special ferromagnetic liquid.

    The diffuser holder connects the moving and magnetic systems of the electrodynamic loudspeaker head into a single mechanically strong structure. The diffuser holder has windows for the exit of air enclosed between it and the diffuser. In the absence of windows, air will act on the moving system as an additional acoustic load, reducing the head's output and worsening its frequency response in the low-frequency region. Diffuser holders are made by stamping from special structural steel, cast using precision casting methods from light alloys, and also pressed from plastic.

    Dynamic drivers of loudspeakers, as a rule, are not used without the acoustic design necessary to obtain satisfactory results. The reason for this is that when the diffuser heads oscillate without forming the air condensation formed by one side of it, they are neutralized by the vacuum formed by the other side. The use of any acoustic design lengthens the path of air vibrations between the front and rear sides of the diffuser and complete neutralization of vibrations does not occur. This is especially important at low frequencies, where the diffuser dimensions are small compared to the wavelength of the acoustic radiation.

    Frame speaker system in addition to performing its main function - the formation of its amplitude-frequency response (AFC) in the low-frequency region, it introduces significant distortions into the reproduced signal due to vibration of the walls and vibrations of the air in it. With a decrease in wall thickness, the sound pressure at low frequencies decreases, the unevenness of the frequency response in the mid-frequency region increases, the level of nonlinear distortions and the duration of transient processes increase. These factors cause so-called “box” sounds, which degrade the sound quality. Therefore, the most serious attention is paid to the design of cabinets in the development of high-quality acoustic systems. There are two sources of vibrations that cause sound to be emitted from the walls of the speaker system:

    • excitation of vibrations of the air in the housing by the back side of the diffuser of the loudspeaker head installed in it and transmission of vibrations through the air to the walls of the housing;
    • direct transmission of vibrations from the diffuser holder of the head to the front wall of the housing, and from it to the side and rear walls.

    To reduce wall vibrations, designers speaker systems They use various methods of sound and sound absorption, as well as vibration insulation and vibration absorption. One of the widely used methods of sound absorption is to fill the internal volume of the housing with mineral wool, special synthetic fiber, wool, super-thin fiberglass and other materials. The effectiveness of sound-absorbing materials is assessed by the sound absorption coefficient A, equal to the ratio of the amount of absorbed energy Wabs to the amount of incident energy Win. The value of this coefficient depends on the frequency, thickness and density of the material. To increase the sound absorption coefficient at low frequencies, increase the thickness of the sound absorber, as well as the density of filling the speaker housing with it. However, the presence of an excessive amount of sound-absorbing material in the housing leads to a decrease in sound pressure at lower frequencies and the reproduction of “dry”, inexpressive bass.

    The sound insulation of the speaker system body is determined both by the amount and physical properties of the sound-absorbing material located inside it, and by the sound insulating properties of its walls. The task of acoustic system developers is to maximize the sound insulation of the cabinet by wisely choosing its design and wall material. One of the common methods of increasing sound insulation is to increase the rigidity and mass of the housing walls. Therefore, some companies use marble, foam concrete and even brick for the manufacture of speaker cabinets. Such enclosures provide good sound insulation (up to 30 dB), but are too heavy. More practical are enclosures whose walls are made of two layers of plywood or particle boards with the gap between them filled with sand, shot or sound-absorbing material. To reduce the amplitude of vibrations of the housing walls, vibration-absorbing coatings in the form of sheet rubber, hard plastic, bitumen mastics, etc. are used, applied to its internal surfaces.

    To combat the direct transmission of vibrations from the diffuser holder of the head to the front wall, and from it to the other walls of the housing, solid rubber gaskets are used, installed between the diffuser holder and the front wall, local support vibration isolators for mounting screws, shock-absorbing gaskets between the front and side walls of the housing, decoupling of the diffuser holder from the front wall by supporting it on the bottom of the body and other methods. The sound quality is also affected by the external configuration of the body (its shape, the presence of protrusions and depressions reflecting sound, the size of the corner radius, etc.), which determines the degree of manifestation of diffraction effects that cause a violation of the timbre coloring and stereophonic sound picture. Numerous experimental studies have shown that the transition from rectangular enclosures with sharp corners to smoothly shaped enclosures (for example, in the form of a sphere) can significantly reduce the unevenness of the frequency response of sound pressure in the mid and high frequencies. Therefore, many manufacturers of high-quality acoustic systems install mid- and high-frequency loudspeaker heads in streamlined blocks in the form of spheres, cylinders, cuboids with rounded corners, isolated from the acoustic design of low-frequency heads.

    To reduce the unevenness of the frequency response of a low-frequency loudspeaker, the front wall of the rectangular housing of the acoustic systems is made as narrow as possible (as far as the dimensions of the low-frequency head allow). In this case, the frequencies of diffraction peaks and dips in its frequency response are located, as a rule, above the cutoff frequency of the separating filter. Reducing the width of the front wall of the cabinet also helps to expand the directional pattern of the speaker system. The depth of the cabinet significantly affects the magnitude of “delayed” resonances, which, apparently, are the reason for the fact that has long been established experimentally that speaker systems with a flat cabinet subjectively sound worse compared to speaker systems with a sufficiently deep cabinet.

    This new series of articles is dedicated to acoustic systems. Due to the fact that the topic is extremely broad, we decided to create a series of publications reflecting the selection criteria when purchasing speakers. This article focuses on the acoustic properties of cabinet materials and acoustic design. The post will be especially useful for those who are faced with choosing speakers, and will also provide information for people who want to create their own speakers in the process of their DIY experiments.

    There is an opinion that one of the decisive factors affecting the sound of speakers is the material of the housing. PULT experts believe that the importance of this factor is often exaggerated, however, it is truly important and cannot be written off. An equally important factor (among many others) that determines the sound of speakers is the acoustic design.

    Material: from plastic to granite and glass

    Plastic - cheap, cheerful, but resonates

    Plastic is often used in the production of budget speakers. The plastic body is lightweight, significantly expands the possibilities of designers; thanks to casting, almost any shape can be realized. Different types of plastics differ greatly in their acoustic properties. In the production of high-quality home acoustics, plastic is not very popular, but it is in demand for professional samples, where low weight and mobility of the device are important.
    (for most plastics the sound absorption coefficient ranges from 0.02 - 0.03 at 125 Hz to 0.05 - 0.06 at 4 kHz)


    A typical representative of the “plastic brotherhood” in home acoustics with decent characteristics and an attractive price: Bookshelf speakers

    Tree - from felling to golden ears

    Due to its good absorption properties, wood is considered one of the best materials for making speakers.
    (the sound absorption coefficient of wood, depending on the species, ranges from 0.15 – 0.17 at 125 Hz to 0.09 at 4 kHz)

    Solid wood and veneer are used relatively rarely for the production of speakers and, as a rule, are in demand in the HI-End segment. Wooden speakers are gradually disappearing from the market due to low manufacturability, instability of the material and prohibitively high cost.


    It is interesting that in order to create truly high-quality speakers of this type that meet the requirements of the most sophisticated listeners, technologists must select material at the cutting stage, as in the production of acoustic musical instruments. The latter is related to the properties of wood, where everything is important, from the area where the tree grew, to the humidity level of the room where it was stored, the temperature and duration of drying et cetera. The latter circumstance complicates DIY development; in the absence of special knowledge, an amateur creating a wooden speaker is doomed to act by trial and error.


    Manufacturers of such acoustics do not report how the situation really is and whether the described conditions are met, and accordingly, any wooden system requires careful listening before purchasing. With a high degree of probability, two speakers of the same model from the same breed will sound slightly different, which is especially important for some demanding listeners.


    Columns from an array of valuable rocks are available in units, their cost is astronomical. Everything yours truly has heard sounds excellent. However, in my subjectively pragmatic opinion, it is disproportionate to the cost. Sometimes, well-designed enclosures made of plywood and MDF have no less musicality, but for many audiophiles “not wood” = “not true hi-end”, and for some, “not wood” simply does not allow the status or spoils the interior design.

    One of the best wooden systems in our catalog is this:
    Floor-standing acoustics (price appropriate)

    Chipboard – thickness, density, humidity

    Chipboard is comparable in cost to plastic, but does not have a number of disadvantages that are inherent in plastic cases. The most significant problem of chipboard is low strength, with a fairly high mass of material.


    Sound absorption in chipboard is non-uniform and in some cases low- and mid-frequency resonances may occur, although the likelihood of their occurrence is lower than in plastic. Plates with a thickness of more than 16 mm, which achieve the required density, can effectively dampen resonances. It should be noted that, as in the case of plastic, the properties of a particular chipboard are of great importance. It is important to take into account the density and humidity of the material, since different chipboards differ in these parameters. Thick, dense chipboards are often used to create studio monitors, which indicates the demand for the material in the production of professional equipment.

    On a note, for fellow DIY fraternity, chipboard with a density of at least 650 - 820 kg/m³ (with a board thickness of 16 - 18 mm) and a humidity of no more than 6-7% is well suited for creating speakers. Failure to comply with these conditions will significantly affect the sound quality and reliability of the speakers.


    Among the worthy chipboard options for home speakers, our experts highlight:

    MDF: from furniture to acoustics

    Today, MDF (Medium Density Fiberboard) is used everywhere, among other things, MDF is one of the most common modern materials for the production of acoustics.


    The reason for the popularity of MDF was the physical properties of the material, namely:
    • Density 700 - 800 kg/m³
    • Sound absorption coefficient 0.15 at 125 Hz – 0.09 at 4 kHz
    • Humidity 1-3%
    • Mechanical strength and wear resistance
    The material is cheap to produce, has acoustic properties comparable to those of wood, while the resistance of the boards to mechanical damage is somewhat higher. MDF has sufficient acoustic rigidity of the speaker cabinet, and sound absorption meets the parameters necessary for creating HI-FI acoustics.


    Visual difference between MDF and chipboard


    There are a lot of wonderful systems among MDF acoustics; the following are optimal in terms of price/quality ratio:

    Acoustic design - boxes, tubes and horns

    Acoustic design is no less important for accurate sound transmission in speakers. The most common types (it is natural that certain types can be combined depending on the specific model, for example, the bass-reflex part of the speaker is responsible for the low and mid-frequency range, and a horn is built for the high ones).

    Bass reflex - the main thing is the length of the pipe

    A bass reflex is one of the most common types of acoustic design. This method allows, with the correct calculation of the length of the pipe, the cross-section of the hole and the volume of the housing, to obtain high efficiency, an optimal frequency ratio, and amplify low frequencies. The essence of the phase inverter principle is that on the back of the body there is a hole with a pipe, which allows you to create low-frequency oscillations in phase with the waves created by the front side of the diffuser. Most often, the bass reflex type is used when creating 2.0 and 4.0 systems.


    To make calculations easier when creating your own speaker, it is convenient to use special calculators; one of the convenient ones is provided at the link.

    In the HI-END philosophy, there are extremely radical, uncompromising judgments about bass reflex systems; I present one of them without comment:

    “Enemy No. 1 is, of course, nonlinear amplification elements in the sound path (then everyone, to the best of their education, understands which elements are more linear and which are less). Enemy No. 2 is the bass reflex. the bass reflex is designed to show off, it should allow a small cheap speaker to record 50... 40... 30 in the passport, and what a trifle even 20 Hz at a level of -3 dB! But the lower frequency range of the bass reflex ceases to be relevant to music; more precisely, the bass reflex itself is a pipe singing its own melody.”

    A closed box is a coffin for extra low ones

    The classic option for many manufacturers is a regular closed box with speaker diffusers brought to the surface. This type of acoustics is quite simple to calculate, but the efficiency of such devices is not great. Also, the boxes are not recommended for lovers of characteristically pronounced lows, since in a closed system without additional elements that can enhance the lows (bass reflex, resonator), the frequency spectrum from 20 to 350 Hz is poorly expressed.


    Many music lovers prefer the closed type, since it is characterized by a relatively flat frequency response and realistic “honest” transmission of the reproduced musical material. Most studio monitors are created in this acoustic design.

    Band-Pass (closed resonator box) – the main thing is not to buzz

    Band-Pass became widespread in the creation of subwoofers. In this type of acoustic design, the emitter is hidden inside the housing, while the insides of the box are connected to the external environment by bass reflex pipes. The task of the emitter is to excite low-frequency oscillations, the amplitude of which increases many times thanks to the bass reflex pipes.

    Open body - no extra walls

    A relatively rare type of acoustic design today, in which the rear wall of the housing is repeatedly perforated or completely absent. This type of design is used to reduce the number of housing elements that affect the frequency response of the speakers.


    In an open box, the front wall has the most significant influence on the sound, which reduces the likelihood of distortion introduced by other parts of the case. The contribution of the side walls (if any are present in the structure), given their small width, is minimal and amounts to no more than 1-2 dB.


    →

    Horn design - problematic loudness champions

    Horn acoustic design is more often used in combination with other types (in particular for the design of high-frequency emitters), however, there are also original 100% horn designs.


    The main advantage of horn speakers is their high volume when combined with sensitive speakers.


    Most experts, not without reason, are skeptical about horn acoustics, for several reasons:
    • Structural and technological complexity, and accordingly, high requirements for assembly
    • It is almost impossible to create a horn speaker with a uniform frequency response (with the exception of devices costing 10 kilobucks and more)
    • Due to the fact that the horn is not a resonating system, it is impossible to correct the frequency response (a minus for DIYers who intend to copy a Hi-end horn)
    • Due to the peculiarities of the waveform of horn acoustics, the sound volume is quite low
    • Overwhelmingly relatively low dynamic range
    • It produces a large number of characteristic overtones (considered a virtue by some audiophiles).


    Horn systems have become the most popular among audiophiles in search of “divine” sound. The tendentious approach allowed the archaic horn design to get a second life, and modern manufacturers were able to find original solutions (effective, but extremely expensive) to common horn problems.


    →
    To be continued... soundproofing on walls

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