RU2756167C1 - Acoustic system - Google Patents

Abstract

FIELD: acoustics.

SUBSTANCE: acoustic system containing an open-type acoustic system including an electrodynamic head fixed in the hole of a shield, additionally comprises an apparatus for absorbing a backward wave emitted by the back side of the diffuser of the head of the open-type acoustic system, constituting a closed-type acoustic system consisting of an electrodynamic head placed in a closed box, wherein the closed-type acoustic system is located on the rear side of the shield, wherein the distance between the head of the open-type acoustic system and the head of the closed-type acoustic system is less than 0.3λ2, wherein λ2 is the wavelength of the high frequency of the working band of the claimed acoustic system; wherein the head of the closed-type acoustic system is located on the upper wall of the closed box, and the upper wall of the closed box is made at an angle β of 0 to 80 degrees relative to the plane of the shield; wherein the head of the open-type speaker system and the head of the closed-type speaker system have the same electroacoustic parameters and are connected to an electrical signal source.

EFFECT: short-circuiting between the front and back sides of the diffuser is excluded.

5 cl, 15 dwg, 8 ex

Description

Technology area

The claimed invention relates to the field of electroacoustics and can be used for sounding rooms and in household electroacoustic equipment.

State of the art

Depending on the type of acoustic design, acoustic systems are divided into systems with open acoustic design, closed acoustic design, bass reflex design, acoustic labyrinth, and so on.

Open-type systems have been used for a long time, but these systems have certain limitations that prevent them from being widely used in high-quality sound systems, since in order to provide comfortable sounding of low frequencies, without which the modern consumer no longer imagines sound reproduction, such systems have large dimensions.

Known acoustic system with an open acoustic design (hereinafter referred to as an open-type speaker) (VK Iofe, MV Lizunkov. "Household acoustic systems". Page 34, Fig. 28. Published in 1984) [1]. In the known open-type speaker system (Fig. 1), the rear side of the sound-emitting surface of the diffuser of the electrodynamic head of direct radiation (hereinafter referred to as the head) is not acoustically isolated from the front. As an open design, a flat screen (shield) or a box, usually in the shape of a parallelepiped without a back wall, is used (VK Iofe, MV Lizunkov. "Household acoustic systems", p. 41, Fig. 36) [1 ]. The known speaker consists of a head and an open acoustic design, for example, a shield with a hole in which the head is fixed. The advantage of the well-known speaker is the simplicity and the absence of the phenomenon of increasing the main resonant frequency of the head after its installation in such an speaker. The disadvantage of an open-type speaker system is its large dimensions, and the lower the required reproducible frequency limit, the larger its dimensions should be. For example, to reproduce without attenuation of sound with a frequency of 50 Hz, the wavelength of which is λ ₁ = 6.8 m, it is necessary that the side of the shield is at least 0.5λ ₁ = 3.4 m. If the side of the shield is less than 0.5λ ₁ , then the incoming, due to the phenomenon diffraction, to the point in space where the listener is located, forward and backward (from the front and back sides of the diffuser) waves interacting with one another due to interference will mutually cancel, and the sound pressure level at these frequencies will be partially or completely reduced. Moreover, the degree of such a decrease will be the greater, the side of the shield is less than 0.5λ ₁ . In this case, instead of exciting sound waves in the surrounding space, the speaker will "distill" the air from one side to the other. This effect is called acoustic short circuit. It manifests itself at frequencies for which the side of the shield is less than 0.5λ ₁ . To exclude the effect of an acoustic short circuit, the speaker with an extended audio range (30-50 Hz) should have large dimensions (3-5 m). This is the main disadvantage of the well-known AS [1].

Known speaker systems with closed acoustic design (VK Iofe, MV Lizunkov. "Household acoustic systems", p. 42, Fig. 37) [1], in which there is no acoustic short circuit, tk. the exit into the space of the sound wave emitted by the rear side of the diffuser of its head is excluded. The main disadvantage of a speaker with a closed acoustic design is that the elasticity of the air volume in a closed box of such an speaker adds up with the elasticity of the moving head system and increases its fundamental resonant frequency, thus narrowing the working band of the speaker from the lower frequencies.

Elimination of acoustic short circuit in the speaker when creating a simple and energy efficient speaker device with open acoustic design, practically without loss of sound energy, is currently an important and unsolved problem.

The problems of creating an open speaker system are described, for example, in the article “Open acoustics. Reopening ”. Internet resource http://www.salonav.com/arch/2016/05/otkrytaya-akustika.htm. (Posted on 05/12/2016). The publication says that the raised topic is not easy and poorly covered in the literature. When designing, you have to be guided by empirical calculations and the results of endless experiments and listening.

From the source https://volgograd.pult.ru/product/napolnaya-akustika-pure-audio-project-trio-15-tb (Published on June 5, 2018) an open-type speaker system is known: floor acoustics Pure Audio Project Trio 15 TB.

All Trio15 models and configurations are based on an exclusive, carefully designed open frame with the best audio components. Since its inception, the Trio15TB (with Tang Band W8-1808 and Eminence Alpha15a speakers) has been highly praised by customers and the media. The new aluminum frame is carefully designed to be vibration-free and easy to transport and install. Two 15 "woofers designed specifically for an open system with a modular architecture.

Specifications

Sensitivity, dB / W / m: 93.

Frequency Response: 36Hz - 20,000Hz.

Resistance: 3.5 to 8 ohms.

Amplifier nominal impedance: 8 ohms.

Recommended Amplifiers: 3.5W (Tubes SE) and above (Tubes, Solid State, Class D).

Number of heads 3.

Heads:

OB-A15se, OB-A15neo.

TB W8-1808, Beyma TPL150 / H, ESS Heil AMT 1.

The main disadvantages of the Trio15 system are its high cost, complexity and the need for special heads.

All open-type acoustic systems offered on the market in the low-frequency range have a significant drop in recoil due to the acoustic short-circuit that occurs precisely at low frequencies (from 20 to 300 Hz). To increase the output in the low-frequency range, manufacturers are forced to install several heads on the shield and increase the shield area, which fundamentally still does not solve the problem of eliminating the acoustic circuit and increases the dimensions. To reduce acoustic distortion and expand the range of reproducible frequencies in the low-frequency region, "systems with a labyrinth" are used, for example: "Acoustic system" (US Patent No. 4,930,596, Loudspeaker system, 05.06, 1990, US class: 181/152, IPC: H04R1 / 28 ); or "bass reflex systems", for example: US Patent No. 5,535,284 Woofer speaker and acoustically coupled sub-woofer speaker system; July 9, 1996, USA class: 381/338, MKI H04R 1/34, H04R 1/32) and other designs of acoustic design.

The disadvantage of the known systems using the above acoustic design of the heads is that the acoustic properties of such designs lead to the color of the emitted sound (due to the fact that their frequency response has a large unevenness due to the presence of standing waves, resonances, vibrations of structural elements, etc. ), and phase inverters are difficult to adjust and their parameters are unstable over time.

Known acoustic system (options) according to patent No. 133378 for a useful model (application No. 2013133407; IPC H04R 5/02; published 10.10.2013) [2], the technical result of which is the elimination of the color of the sound caused by the properties of the housing, equalization of the frequency characteristics of the loudspeaker. The technical result is achieved due to the fact that in an acoustic system containing a housing in which at least one subwoofer is fixed, installed above it, at least one high-frequency loudspeaker, or a coaxial loudspeaker, and the coaxial loudspeaker is a high-frequency loudspeaker mounted on a low-frequency loudspeaker and working through it, the loudspeaker diffusers are directed towards the body mounted on the upper end of the body intended to interact with the flow of sound energy, each subsequent cross-section of the said body in the direction from each loudspeaker is greater than the previous cross-section of the body, the body made open from the side of the lower end and is intended for installation at a distance from the horizontal surface, between the lower end of the housing and the back side of the diffuser of the lower loudspeaker there is a block of acoustic dampers ania (dietary supplement). Both housings 1 and 8 and the scattering cones are interconnected by supporting elements. The distance from the bottom end of the housing 1 to the horizontal surface of the floor and the location of the dietary supplement are selected experimentally according to the quality of low frequency reproduction. Racks 6 set the distance to the floor.

The disadvantages of this speaker are the complexity in manufacturing and tuning, as well as its large dimensions and instability of parameters over time.

A known acoustic system device, which consists of a low-frequency channel, a loudspeaker, a direct sound guide and two taps (US patent No. 5,535,284 Woofer speaker and acoustically coupled sub-woofer speaker system; July 9, 1996, IPC H04R 1/34, H04R 1/32) [3]. In the known device, the reverse side of the loudspeaker diffuser emits sound in a phase of 180 degrees with respect to the direct diffuser. In order to emit sound in phase with a direct diffuser, it is necessary to pass the sound through a sound guide with a length equal to half the wavelength. The sound wavelength at 20 Hz is 16 meters. Taking into account the spacing of the direct and return outputs of the speaker system, the length of the direct sound guide should be about 4 meters. For this purpose, the device uses a direct sound guide (a box in the form of a straight circular cylinder) with a total height of more than 3 meters. The used method of fastening inevitably causes mechanical stresses in the pipe, and this, as is known, leads to resonance of the sound guide at its natural frequency. Therefore, the frequency range is limited to low frequencies only. In addition, to reduce resonance effects, the internal volume of the sound guide is filled with polyester fiber. The advantage of the device is low acoustic distortion, since the speaker system is open. The disadvantage is the large size and large unevenness of the amplitude-frequency characteristic, the complexity of tuning and the instability of the device parameters over time.

In search of a solution to the problem associated with the phenomenon of acoustic closure in an open-type speaker system, the authors turned to methods and devices for active noise cancellation.

To eliminate the effect of acoustic short circuit in an open-type speaker system, the authors suggested that it is possible to suppress the sound wave emitted by the rear side of the diffuser of its head using known methods of active suppression of acoustic noise.

The basis of active methods for damping acoustic noises and vibrations is the excitation of such additional noise and vibration fields, the interference of which with the primary fields leads to a predetermined reduction in the residual noise level in the room. The variety of systems for active noise and vibration damping is determined by the methods of generating signals that provide excitation of additional fields, a variety of means for their excitation, features of objects or characteristics of the space in which active damping is provided, etc.

At the same time, active noise suppression devices have the best dynamic performance characteristics, in which signals for exciting additional fields are formed using negative feedback circuits. Such devices contain at least one acoustic field exciter (a loudspeaker loaded on the medium) and a corresponding acoustic pressure receiver (microphone) located in the immediate vicinity of this loudspeaker.

A large number of patents related to active noise cancellation are known in the art.

Known devices for suppressing noise (USSR Inventor's Certificate: No. 349011, 356819, 590807, 832578, 836655), the essence of which is that the sound signal of the noise, perceived by the microphone, is converted into electrical and after processing is fed to a speaker that emits sound waves of the same frequency, but with a phase opposite to the waves incident on the microphone.

A device for suppressing noise is known, comprising a microphone, a diffuser for emitting waves in antiphase to the noise waves and an amplifier connected to a microphone located on the inside of the diffuser, characterized in that it contains one or more vibrators located on the outside of the diffuser from the side of the incoming noise waves , while the amplifier has an adjustable gain and is connected to the vibrators, and for uniform noise suppression in the entire suppression zone, the diffuser has a shape close to the wavefront of the incoming noise waves. Patent of the Russian Federation No. 2115960, IPC G10K 11/16, 1998 [4].

There is a known method of active sound damping, which consists in the fact that in the direction of propagation of the suppressed signal wave, together and collinear with it, a pump wave is emitted with an amplitude much greater than the amplitude of the signal wave, and the frequency and initial phase of the emitted wave are twice the frequency and initial phase of the suppressed waves. As a result, the efficiency of sound damping increases, suppression of the low-frequency signal by high-frequency pumping is provided. The pump is prevented from falling into the passband of the receiving path of the locator. Patent of the Russian Federation No. 2185666, IPC G10K 11/16, 2002 [5].

Known is an active noise suppression device containing an acoustic field exciter (a loudspeaker loaded on a medium) and a corresponding acoustic pressure receiver (microphone) located opposite this loudspeaker. An inverting amplifier and a compensator are included in the negative feedback circuit. The negative feedback circuit includes both a loudspeaker and a microphone, and the microphone output is connected to the input of the preamplifier, the output of which is connected to the input of the compensator, and the output of the compensator is connected to the input of the inverting amplifier, to the output of which the loudspeaker is connected. US patent No. 4527282, IPC G11K 11/00, 1985 [6].

The known method and device for active suppression of acoustic noise, containing an acoustic field exciter (loudspeaker), loaded on the medium, and a corresponding acoustic pressure receiver (microphone) located opposite this loudspeaker. The inverting amplifier and compensator are included in the feedback circuit, which includes both a loudspeaker and a microphone, and the microphone output is connected to the input of the preamplifier with an electrically controlled gain, the output of the preamplifier is connected to the input of the compensator, the output of the compensator is connected to the input of the inverting amplifier, to the output of which is connected to a loudspeaker, and the control input of the preamplifier is connected to the output of the control voltage driver, the input of which is connected to the output of the microphone. US patent No. 5848169, IPC G11K 11/00, 1998 [7].

However, all patents known from the prior art relate to protection against acoustic noises of various origins: in industrial and residential premises, theaters, concert halls, offices, as well as in open areas, from unpleasant or interfering sounds. The use of known patents to eliminate the acoustic short circuit significantly complicates the open-type speaker system and can lead to significant linear, nonlinear and intermodulation distortions of the acoustic signal emitted by the speaker due to the inertia of the used circuits and their nonlinearity.

An acoustic system with an open acoustic design (hereinafter referred to as an open-type speaker) (VK Iofe, MV Lizunkov. "Household acoustic systems". Pages 34, Fig. 28 Published 1984) [1], consisting of a head and an open acoustic design in the form of a shield with a hole in which the head is fixed. The advantage of the known open-type speaker system is that there is no increase in the resonant frequency of the head. The disadvantage is the presence of the effect of an acoustic short circuit between the front and rear sides of the diffuser, to eliminate the effect of which it is necessary to increase its dimensions, and the lower the required reproducible frequency limit, the larger its dimensions should be.

The technical result is the creation of an open-type acoustic system, with the elimination of an acoustic short circuit between the front and rear sides of the diffuser, and thus having a small size and a range of reproducible frequencies extended into the low-frequency region up to 20 Hz.

Disclosure of invention

The technical result is achieved by the fact that an acoustic system (AC) containing an open-type speaker, including an electrodynamic head fixed in the shield opening, additionally contains a device for absorbing the backward wave emitted by the rear side of the diffuser of the open-type speaker head, which is a closed-type speaker system , consisting of an electrodynamic head located in a closed box, and the closed-type speaker system is located on the rear side of the shield, while the distance between the open-type speaker system head and the closed-type speaker system head is less than 0.3λ2, where λ2 is the wavelength of the upper frequency of the operating stripes of the claimed acoustic system;

moreover, the head of the closed-type speaker system is located on the upper wall of the closed box, and the upper wall of the closed box is made at an angle β from 0 to 80 degrees with respect to the plane of the shield;

moreover, the head of the open-type speaker system and the head of the closed-type speaker system have the same electro-acoustic parameters and are connected to the source of the electrical signal.

In this case, the head of the open-type speaker system and the head of the closed-type speaker system are connected to the source of the electrical signal in parallel to each other and in phase.

In this case, the head of the open-type speaker system and the head of the closed-type speaker system are connected to the source of the electrical signal in series and in phase.

The technical result is also achieved by the fact that an acoustic system (AC) containing an open-type acoustic system, including an electrodynamic head fixed in the shield opening, further comprises a device for absorbing the backward wave emitted by the back side of the diffuser of the open-type acoustic system head, which is an acoustic system closed type, consisting of an electrodynamic head placed in a closed box, and the head of the open type speaker system and the head of the closed type speaker system are installed on the shield in the same plane, as a result of which their axes are parallel, and at a distance of less than 0.3λ2, where λ2 is the wavelength the upper frequency of the working band of the claimed acoustic system, while the closed box of the closed-type speaker system is located on the front side of the speaker panel;

moreover, the head of the open-type speaker system and the head of the closed-type speaker system have the same electro-acoustic parameters and are connected to the source of the electrical signal.

In this case, the head of the open-type speaker system and the head of the closed-type speaker system are connected to the source of the electrical signal in parallel to each other and in antiphase.

In this case, the head of the open-type speaker system and the head of the closed-type speaker system are connected to the source of the electrical signal in series and in antiphase.

List of figures

FIG. 1. Block diagram of the speaker system.

FIG. 2. Scheme of propagation of sound waves from the speaker system to the listening point.

FIG. 3a. Diagram of parallel connection of electrodynamic heads 2 and 6 of the acoustic system.

FIG. 3b. Diagram of serial connection of electrodynamic heads 2 and 6 of the acoustic system.

FIG. 4. The inventive speaker system according to example 1, front view.

FIG. 5. Section AA in FIG. 4.

FIG. 6. The inventive acoustic system according to example 5.

FIG. 7. Section B-B in Fig. 6.

FIG. 8. The claimed acoustic system according to example 6.

FIG. 9. Section BB in FIG. eight.

FIG. 10. The inventive acoustic system according to example 7.

FIG. 11. Section G-G in Fig. ten.

FIG. 12. The inventive acoustic system according to example 8.

FIG. 13. Section D-D in Fig. 12.

FIG. 14a. The scheme of parallel connection of the electrodynamic heads 2 and 6 of the acoustic system according to example 8.

FIG. 14b. Diagram of the serial connection of the electrodynamic heads 2 and 6 of the acoustic system according to example 8.

FIG. 15. Graphs showing the effectiveness of the backward wave absorption device.

List of positions

1 - an open-type speaker system (AC);

2 - electrodynamic head of direct radiation (hereinafter referred to as head) AC 1 of open type;

3 - shield;

4 - an installation hole in the shield 3;

5 - closed-type acoustic system (AC);

6 - closed-type electrodynamic head of direct radiation AC 5;

7 - closed box AC 5 closed type;

8 - listening point;

9 - the path of the sound wave emitted by the front wall of the diffuser of the head 2 to the listening point 8 (conventionally);

10 - the path of the sound wave emitted by the rear wall of the diffuser of the head 2 to the listening point 8 (conventionally);

11 - the path of the sound wave emitted by the front wall of the diffuser of the head 6 to the listening point 8 (conventionally);

12 - declared AU;

13 - top wall of a closed box;

14 - source of electrical signal;

15 - cable providing electrical connection of the electrical signal source 14 with heads 2 and 6;

16 - acoustic unit, including mid-frequency and high-frequency channels of example 1 of the claimed speaker;

17 - mid-frequency head of an example of the claimed speaker;

18 - high-frequency head of an example of the claimed speaker;

19 - element of rigidity of the structure of an example of the implementation of the inventive AU;

20 - axis of the electrodynamic head 2;

21 - axis of the electrodynamic head 6;

22 - front side of AC 5 for example 5;

23 is a graph of the frequency response of the inventive speaker with the included device for absorbing the backward wave.

24 - AFC of the claimed speaker with switched off backward wave absorption device.

25 - arithmetic difference between the amplitude values in the first and second cases.

Implementation of the invention

The claimed device of the acoustic system 12 (Fig. 1) contains an acoustic system AC 1 with an open acoustic design (hereinafter referred to as an open-type AC), consisting of a shield 3 with a mounting hole 4, in which an electrodynamic head 2 of direct radiation is placed (hereinafter referred to as a head 2) ...

The claimed AC 12 also contains a device 5 for absorbing the backward wave emitted by the rear side of the diffuser of the head 2. The device 5 for absorbing the backward wave may be a closed-type speaker system AC 5, consisting of an electrodynamic head 6 of direct radiation (hereinafter, head 6) and a closed box 7. The head 6 is installed on the upper wall 13 of the box 7. The upper wall 13 of the closed box 7 is made at an angle β with respect to the plane of the shield 3.

The inventive system 12 can be made in two versions: in one version, the AC 1 of the open type and the AC 5 of the closed type are combined into a single structure by a stiffening element 19 (Figs. 4, 5). In another version, the AC 1 of the open type and the AC 5 of the closed type are made in the form of separate devices (Fig. 6, 7). In this case, the angle β between the axis 20 of the electrodynamic head 2 and the axis 21 of the electrodynamic head 6 can vary over a wide range from 0 to 80 degrees. In the construction of FIG. 4 the angle β is 70 degrees. In the construction of FIG. 6, the coaxial arrangement of electrodynamic heads 2 and 6 is optimal, when the angle β = 0. Deviation from coaxiality up to 80 degrees is also allowed (example 6, Figs. 8, 9).

Below will be given a detailed description of each of the executions with specific examples.

The device 5 for absorbing the backward wave is placed behind the AC 1 from the rear side of the shield 3, in the immediate vicinity of the rear side of the diffuser of the head 2 of the AC 1 of the open type (Fig. 1).

Distancel between the head 2 AC 1 of the open type and the head 6 AC 5 of the closed type is:l<0.3λ _v , where λ _v - the length of the sound wave at the upper frequencyf _v working band of the claimed AU 12. Preferablyf _v = 350 Hz, for which λ _v = 0.97 m.

The head 2 AC 1 of the open type and the head 6 of the AC 5 of the closed type have the same electro-acoustic parameters and with the help of the cable 15 are connected in phase to the source 14 of the electrical signal, while the heads 2 and 6 can be connected both in parallel to each other (Fig.3a), so and sequentially (Fig. 3b).

In the claimed AC 12, low-frequency heads, for example, 150GDN45-8 (http://noema.ru/catalog/64/234. Published on 04/11/2020), can be used as heads 2 and 6. The diameter of these heads is 260 mm.

Body 7 АС 5 and shield 3 АС 1 must be made of dense material with a high level of internal sound absorption. One of the materials meeting these requirements is hardwood plywood.

Examples of specific implementation

Example 1 . Below is an example of a specific implementation of the inventive acoustic system 12 in the performance, manufactured by the authors empirically, when the AC 1 of the open type and the AC 5 of the closed type are combined into a single structure (Fig. 4, 5).

FIG. 4 is a front view and FIG. 5 is shown in section A-A of a sample made by the authors.

The open-type speaker system 1 is made up of a shield 3 with a mounting hole 4, in which an electrodynamic head 2 of direct radiation is placed (hereinafter, head 2). Behind AC 1, in the immediate vicinity of the rear side of the diffuser of the open-type AC head 2, there is a device 5 for absorbing the backward wave emitted by the rear side of the diffuser of the head 2. The device for absorbing the backward wave is a closed-type speaker system AC 5, consisting of a direct radiation (hereinafter head 6) and closed box 7. Head 6 AC 5 closed type is located on the upper side 13 of the closed box 7, the front wall of which is a continuation of the shield 3. The top side 13 of the closed box 7 is inclined to the horizontal plane. The angle β between the axis 20 of the electrodynamic driver 2 and the axis 21 e lektrodinamicheskoy head 6 is in the range of 0 to 80 degrees. In example 1, the angle β is 70 degrees. The distance l between the centers of the diffusers of the head 2 and the head 6 of the AC 5 closed type is 255 mm.

The reproducible range of the claimed AC 12 frequencies - the operating frequency range - is located within 20-350 Hz. The range of frequencies audible to the human ear extends from 20 up to 20,000 Hz. Therefore, the claimed AC 12 is a low-frequency channel of a sound reproducing system. To expand the range of reproducible frequencies up to 20,000 Hz, a sample of the practical implementation of the claimed AC 12 is supplemented with an acoustic unit 16 containing mid-frequency (head 17) and high-frequency (head 18) channels (Figs. 4 and 5). Block 16 is structurally located in the upper part of the sample of practical implementation, above the claimed AC 12.

The shield 3 AC 1 of the open type and the closed box 7 AC 5 of the closed type in example 1 are a single structure. Stiffeners 19 ensure the integrity of the structure of the AC 12, while being its side walls. Frontal shield 3 has dimensions: width b = 360 mm;height h = 1077 mm. The dimensions of the claimed AU are determined by the rigidity of the head 2 and the dimensions of the AU 5. Therefore, the height h of the claimed AU can have a value equal to 900-1600 mm, the width b = 350-450 mm.

In this example, the speaker height from the floor to the upper plane is given taking into account the height of the acoustic unit 16 and is equal to = 1573 mm. The height h of the claimed AC 12, excluding block 16, is equal to 1077 mm. Depth k of closed speaker = 450 mm.

The material used is birch plywood 22 mm thick.

The open-type speaker 2 and the closed-type speaker 6 have the same electro-acoustic parameters. As these heads can be used, for example, heads 150GDN45-8 (http://noema.ru/catalog/64/234. Published on April 11, 2020). Head diameter 260 mm.

Heads 2 and 6 are connected in parallel to each other and are connected by means of a cable 15 to a source 14 of an electrical signal in phase (Fig. 3a). Signal source 14 is a low frequency power amplifier with sufficient power to drive heads 2 and 6.

As a mid-frequency head 17 can be used a broadband head of the firm "Noema" for example 100GDSh65-4 (http://noema.ru/catalog/81/226. Published on 04/11/2020). As a head 18 for reproducing high frequencies, a broadband head from Noema, for example, 50GDSh83-4 (http://noema.ru/catalog/81/216. Published on 11.04.2020), can be used. Because there is no acoustic short circuit in the mid-frequency and high-frequency channels of the acoustic unit 16 due to the small wavelengths excited by their heads; they use an open-type acoustic design.

Example 2. The example is similar to example 1, but the angle β between the axis 20 of the electrodynamic head 2 and the axis 21 of the electrodynamic head 6 is 40 degrees.

Example 3. The example is made similarly to example 1, but the angle β between the axis 20 of the electrodynamic head 2 and the axis 21 of the electrodynamic head 6 is 80 degrees, and the electrodynamic heads 2 and 6, connected to the source 14 of the electrical signal, are connected in series with each other and in phase (Fig.3b).

Example 4. The example is made similarly to example 1, but without the addition of an acoustic unit 16, containing mid-frequency (head 17) and high-frequency (head 18) channels 16, while the height h of the claimed speaker is 1077 mm, width b = 350 mm. The material used is birch plywood 16 mm thick.

Example 5. In the inventive speaker system, the open-type speaker 1 and the closed-type speaker 5 are made as separate devices, as shown in FIG. 6, 7.

The open-type speaker system 1 is made up of a shield 3 with a mounting hole 4, in which an electrodynamic head 2 of direct radiation is placed (hereinafter, head 2). In this case, the shield 3 can be made with some inclination in relation to the horizontal plane (Fig. 7). Behind AC 1, in the immediate vicinity of the rear side of the diffuser of the open-type AC head 2, there is a device 5 for absorbing the backward wave emitted by the rear side of the diffuser of the head 2. The device for absorbing the backward wave is a closed-type speaker system AC 5, consisting of a direct radiation (hereinafter referred to as head 6) and a closed box 7.

The head 6 AC 5 of the closed type is located on the front side 22 of the closed box 7, which is located to the horizontal plane at the same angle as the shield 3, in order to ensure the coaxiality of the heads 2 and 6. In this example, their coaxial arrangement is used, i.e. angle β = 0.

With a coaxial arrangement, a minimum distance l between the head 2 and the head 6 of the AC 5 closed type is achieved, less than 300 mm.

So the distancel between the head 2 AC open type and the head 6 AC closed type is:l<0.3λ _v , where λ _v - the wavelength of the upper frequencyf _v working band of the claimed AU. Preferablyf _v = 350 Hz, for which λ _v = 0.97 m.

The open-type speaker 2 and the closed-type speaker 6 have the same electro-acoustic parameters and are connected to an electrical signal source 14 in phase and sequentially (Fig. 3a).

In the claimed AC 12, low-frequency heads, for example, 150GDN45-8 ( http://noema.ru/catalog/64/234. Published on 04/11/2020), can be used as heads 2 and 6. The diameter of these heads is 260 mm.

The casing 7 АС 5 and Shield 3 АС 1 are made of dense material with a high level of internal sound absorption, namely of plywood with a thickness of 42 mm.

Example 6. The claimed acoustic system is made according to example 5, however, the angle β between the axes of the electrodynamic heads 2 and 6 in the embodiment shown in FIG. 8 and 9 has a value of 80 degrees. Heads 2 and 6 are connected with a cable 15 to a source 14 of an electrical signal in phase, with series connection (Fig. 3b). The height of the shield 3 is significantly increased, while the head 6 is located on the upper edge of the closed-type speaker. The material used is birch plywood 22 mm thick.

Example 7. The claimed acoustic system is made according to example 5, however, the shield 3 AC 1 of the open type and the closed box 7 AC 5 of the closed type are interconnected by connecting elements, such as strips or threaded bushings (not shown), to fix the optimal distance between the AC open type 1 and closed-type AC 5. The angle β between the axes of the electrodynamic heads 2 and 6 in the embodiment shown in FIG. 10 and 11, has a value of 0 degrees (coaxial position of heads 2 and 6).

Example 8. The claimed acoustic system is made according to example 1, however, the dynamic heads 2 and 6 are installed on the shield 3 in one plane, at a distance slightly exceeding their diameter. As a result, the axes 20 and 21 of heads 2 and 6 are parallel (co-directional arrangement of heads 2 and 6, β = 0 degrees). In this case, the closed box 7 АС 5 is located on the front side of the speaker system (from the listener's side).

The head 2 AC 1 of the open type and the head 6 of the AC 5 of the closed type have the same electro-acoustic parameters and with the help of the cable 15 are connected to the source 14 of the electrical signal in antiphase, while the heads 2 and 6 can be connected both in parallel to each other (Fig.14a), so and sequentially (Fig. 14b).

This design is the most advantageous in terms of sound fidelity and the ability of a closed speaker 5 to absorb the backward wave of speaker 1, since the geometric path lengths of sound waves from the back of the head 2 and the back of the head 6 to the listener are practically the same, and the diffusers move in antiphase. Consequently, two antiphase, interfering waves at the listening point practically cancel each other out.

Work

Elimination of the acoustic short circuit in the open AC 1 of the claimed device is achieved by eliminating the sound wave emitted by the rear side of the diffuser of the AC 1 head 2, i.e. backward wave. This is achieved by including in the inventive device an additional sound source located in the immediate vicinity of the rear side of the diffuser of the head 2 AC 1. At the same time, the additional sound source and the rear side of the diffuser of the head 2, in the operating frequency range, emit sound waves into the surrounding space equal to in amplitude, but opposite in phase. Such a ratio of these waves leads to their mutual destruction in the surrounding space due to their interference. The above is true for sound waves, the length of which is much greater than the distance between the additional source and the rear side of the diffuser of the head 2, which takes place in the low-frequency range of the audio range (20-350 Hz), for which the claimed acoustic system 12 is intended. For the specified frequency range , at a speed of sound in the air of 340 m / s, sound waves have a length of 0.97 m to 17 m. An additional sound source in the claimed device 12 is a closed-type AC 5 (Fig. 1). In this case, the head 2 and the head 6 receive the same electrical signal from the source 14 (Fig. 3).

The claimed device 12 works as follows. When an electrical signal is supplied from a source 14 to heads 2 and 6 (Fig. 3), their diffusers begin to oscillate in phase in accordance with the shape of the supplied sound signal. The spectrum of the specified signal does not go beyond the operating frequency range of the claimed device 12. At the same time, sound waves are emitted into the surrounding space by three emitters, namely: the front and rear sides of the diffuser of the head 2 and the front side of the diffuser of the head 6 (Fig. 2). The minimum length λ _in these waves is at the upper frequency f _in = 350 Hz of the operating frequency range of the claimed AC 12, where λ _in = 0.97 m, which is much larger than the sizes of heads 2 and 6, due to which the directivity pattern of each of the three above-mentioned emitters throughout the operating frequency range has the shape of a sphere. In this case, the front wall of the diffuser of the head 2 emits a sound wave 9 (Fig. 2), the rear wall of this diffuser emits a sound wave 10, and the front wall of the diffuser of the head 6 emits a sound wave 11. Due to the diffraction of these waves and their large length in comparison with the dimensions around obstacles, these waves reach listening point 8 with practically the same phase delay and attenuation. At the same time, at the point 8 of the location of the listener, sound waves 9, 10 and 11 have sound pressures B ₈ , C ₈ , D _8, respectively. Because heads 2 and 6 are connected in phase, then the oscillations of their diffusers are in phase. In addition, the electroacoustic parameters of heads 2 and 6 are the same, therefore, for sound pressures C ₈ and D ₈ , the equality is true:

D ₈ = -C ₈ (1)

At the listening point 8 (Fig. 2), the result of the interference of waves 9, 10 and 11 will be their sum. Therefore, the sound pressure A ₈ at listening point 8 has the form:

A ₈ = B ₈ + C ₈ + D ₈ = B ₈ + (C ₈ + D ₈ ) = B ₈ , (2)

since from (1) it follows that the expression in brackets (C ₈ + D ₈ ) is equal to zero.

From (2) it can be seen that at the listening point 8, the waves emitted by the rear side of the diffuser of the head 2 and the front side of the diffuser of the head 6, due to interference, completely extinguished each other, and the listener hears only wave 9 emitted by the front wall of the diffuser of the head 2. Similar the results will be when you change the listening point. Thus, the goal of creating an open-type speaker system with small dimensions has been achieved, allowing the use of the claimed AC 12 in a small room, incl. in ordinary apartments. For the operation of the claimed acoustic system, shield 3 should not have dimensions comparable to the wavelength. It can be much smaller in size, sufficient for rigid attachment of the head 2, and at the same time the range of reproducible frequencies in the low-frequency region claimed by the speaker extends to the lower limit of the frequencies reproduced by the head 2.

FIG. 15 is a graph showing the efficiency of the backward wave absorption device. The dependence of the sound pressure in decibels on the signal frequency in the range from 20 to 440 Hz.

Graph 1 23 - AFC of the claimed speaker with the included device for absorbing the backward wave. Graph 2 24 - AFC of the claimed speaker with switched off backward wave absorption device. Graph 3 25 - arithmetic difference between the amplitude values in the first and second cases, showing the effectiveness of the application of the backward wave absorption device. At a frequency of 20 Hz, the effectiveness of the claimed device is 24 dB, which significantly increases the level of reproduction of low frequencies in the audio range.

Operation of the sample of the claimed AC 12 as part of a stereophonic system has shown that the sample provides high sound quality. Experts noted that low frequencies sound effective, without booming and with good dynamics. The sound of the low frequencies of the sample is preferable to the sound of speakers with a different acoustic design, for example, with such as a bass reflex. Musical works of different styles were listened to: classical, jazz, rock, orchestra, electronic instruments, organ, male and female vocals, opera. The sound of individual instruments was also assessed: piano, drums, winds (saxophone, trumpet), strings (violin, cello, double bass). None of the several independent experts indicated any negative perceptions of the works they heard. On the contrary, everyone noted a very correct, light, even, natural sound. The bass sounds voluminous, low frequencies appear at once in the entire volume of the room, while not "pressing" on the listener. The contrabass, like the bass guitar, is heard in the entire range evenly, without amplification of individual notes (as is often the case when listening to bass-reflex speakers). Percussion instruments sound bright. The sounds of drum membranes are clearly audible. The sound is very spacious. The impression that it is generated not in the speakers, but directly in the space of the room. When listening to orchestral works, experts noted that the sound is very similar to the sound of live instruments.

An important characteristic of the proposed speaker design is the absence of internal resonances. AC 1 of the open type is not capable of generating resonances due to the absence of parallel surfaces that reflect sound. Resonances do not arise inside the enclosure of the AC 5 of a closed type, since its natural resonance frequencies are outside the range reproduced by the electrodynamic head 6.

Industrial applicability

The claimed acoustic system is made of industrially applicable components (components) and materials.

The prototype showed the possibility of achieving the technical result: the elimination of an acoustic short circuit between the front and rear sides of the diffuser of the open speaker head, and due to this, having a small size and expanded into the low-frequency region, the reproducible frequency range up to 20 Hz.

The claimed acoustic system can be used in household electro-acoustic equipment.

SOURCES OF INFORMATION

1. V.K. Iofe, M.V. Lizunkov. "Household acoustic systems". Published in 1984 - the closest analogue.

2. Patent for utility model No. 133378 "Acoustic system (options)" (application No. 2013133407; IPC H04R 5/02; published 10.10.2013).

3. US Patent No. 5,535,284 Woofer speaker and acoustically coupled sub-woofer speaker system; July 9, 1996, IPC H04R 1/34, H04R 1/32.

4. Patent of the Russian Federation No. 2115960, IPC G10K 11/16, 1998

5. Patent of the Russian Federation No. 2185666, IPC G10K 11/16, 2002

6. US patent No. 4527282, IPC G11K 11/00, 1985

7. US patent No. 5848169, IPC G11K 11/00, 1998

Claims (8)

1 . An acoustic system containing an open-type speaker system, including an electrodynamic head fixed in the shield opening, additionally contains a device for absorbing the backward wave emitted by the back side of the diffuser of the open-type speaker system head, which is a closed-type speaker system consisting of an electrodynamic head located in a closed box, and the closed-type speaker system is located on the back of the shield, while the distance between the open-type speaker head and the closed-type speaker head is less than 0.3

2, where

2 - wavelength of the upper frequency of the working band of the claimed acoustic system; moreover, the head of the closed-type speaker system is located on the upper wall of the closed box, and the upper wall of the closed box is made at an angle β from 0 to 80 degrees with respect to the plane of the shield; moreover, the head of the open-type speaker system and the head of the closed-type speaker system have the same electro-acoustic parameters and are connected to the source of the electrical signal. 2. The speaker system according to claim 1, characterized in that the head of the open-type speaker system and the head of the closed-type speaker system are connected to the source of the electrical signal in parallel to each other and in phase. 3. The speaker system according to claim 1, characterized in that the head of the open-type speaker system and the head of the closed-type speaker system are connected to the source of the electrical signal in series and in phase. 4 . An acoustic system containing an open-type speaker system, including an electrodynamic head fixed in the shield opening, additionally contains a device for absorbing the backward wave emitted by the back side of the diffuser of the open-type speaker system head, which is a closed-type speaker system consisting of an electrodynamic head located in closed box, and the head of the open-type speaker system and the head of the closed-type speaker system are installed on the shield in the same plane, as a result of which their axes are parallel, and at a distance of less than 0.3

2, where

2 - the wavelength of the upper frequency of the working band of the claimed acoustic system, while the closed box of the closed-type speaker system is located on the front side of the speaker panel; moreover, the head of the open-type speaker system and the head of the closed-type speaker system have the same electro-acoustic parameters and are connected to the source of the electrical signal. 5. The speaker system according to claim 4, characterized in that the head of the open-type speaker system and the head of the closed-type speaker system are connected to the source of the electrical signal in parallel to each other and antiphase or in series and antiphase.

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