EP2643980A1

EP2643980A1 - High fidelty electro-acoustic enclosure and method of manufacture

Info

Publication number: EP2643980A1
Application number: EP11805070.7A
Authority: EP
Inventors: Guy Lemarquand
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-11-23
Filing date: 2011-11-22
Publication date: 2013-10-02
Also published as: US20140044299A1; FR2967860A1; US9210490B2; WO2012069708A1

Abstract

The invention relates to an electro-acoustic enclosure (10) comprising walls defining two cavities (1; 2), each provided with an aperture (11; 21) shut off by a loudspeaker (12; 22), noteworthy in that it is said to be "enclosed" and in that each cavity (1; 2) has a shape for which the intersection with any plane containing the central axis (Xl-Xl'; X2, X2') of said loudspeaker (12; 22) is a portion of an ellipse (Eli; E2i), the major axes (Xli-Xli'; X2i-X2i') of said ellipses (Eli; E2i) being substantially coincident with said central axis (Xl-Xl'; Χ2, Χ2') of said loudspeaker (12; 22), said aperture (11; 21) being secant to said ellipses (Eli; E2i) in such a way that the second extreme points (Pli'; P2i') of each ellipse (Eli; E2i) are situated in said aperture (11; 21).

Description

HIGH LOYALITY ELECTRO-ACOUSTIC SPEAKER AND METHOD OF

MANUFACTURING

Technical area

The present invention relates to a high fidelity electroacoustic enclosure and its method of manufacture. Prior art

Historically, attempts have been made to improve the musical reproducibility of electroacoustic loudspeakers. Electroacoustic loudspeakers are commonly called "two-way" or "three-way", each channel being constituted by one or more electromagnetic transducers, called "loudspeakers", and a cavity, called "charge" forming the seat. at the rear of the speaker which is fixed on the front wall thus closing the load. The dimensions, the volume, the geometry and the surface state of the load are adapted according to the desired frequency range and the performances to be achieved. Thus, the track or stage "boomer" is expected to restore frequencies between about 20 and 600 Hz, the "medium" stage is expected to restore frequencies between about 500 and 10 000 Hz and the "tweeter" stage is intended to reproduce frequencies from around 8000 Hz and, in principle, beyond 20 000 Hz.

The body of the electro-acoustic enclosure delimiting the load is generally made of wood-based panels, for example medium. During the operation of electro-acoustic enclosures, reciprocating or periodic movements of the speaker diaphragms cause the loudspeaker brackets and panels to vibrate. These vibrations parasitize the sound emitted by the electroacoustic speaker and interfere with the faithful reproduction of the recorded music. This nuisance is all the more prejudicial as the surface of the panels is clearly greater than that of the speaker diaphragm. The emission surface of the parasitic vibrations is therefore greater than that of the membranes. According to the mechanical properties of the panels and according to their method of assembly, the natural frequency of the panels can correspond to an exciter frequency of each speaker membrane. This unwanted coupling of the frequencies then creates resonance operation, which is prohibitive for the quality of acoustic reproduction. These vibratory phenomena are well known under the name of "cash signature" and create intermodulation distortions prohibiting the faithful reproduction of the signals emitted by the loudspeakers.

Moreover, in addition to the vibration of the walls of the acoustic chamber, it is known that the rear wave is reflected on said walls and spring towards the front of the enclosure creating additional distortions.

Some manufacturers have tried to minimize the problem of the "cash signature", in particular by stiffening the panels, for example by using sandwich-type panels made from crossed fibers, assembled by bonding and connected by transverse stiffeners.

The publication CN 2 274 853 describes an electro-acoustic enclosure comprising assembled panels, each panel being made of flat natural stone.

The publication CN 2 371 745 describes an electro-acoustic enclosure comprising assembled panels, each panel being made of stone such as in particular carnelian, granite or marble to limit the parasitic effects of the resonance of the walls.

The publication CN 2 284 477 also describes an electro-acoustic enclosure comprising assembled panels, each panel being made of stone for obtaining a pure, clean, rich and high quality sound.

Finally, the publication DE 10 111 129 describes an electro-acoustic enclosure whose walls are flat or curved and made of wood, stone, metal, plastic or artificial stone.

Despite the different techniques used, these electro-acoustic speakers do not provide a "cash signature" sufficiently reduced to obtain a high quality sound.

In addition to the materials used and the surface state of the load, it is known that the performance of the enclosure also depends on the volume and shape of the cavity forming the load, the geometry and the dimensions of the vents in the case. a speaker "bass reflex".

Since the work of some precursors such as Neville THIELE, Siegfried LINKWITZ, Garry MAGOLIS and Richard H. SMALL who laid the foundations of electroacoustics, software has been developed to optimally determine the volume and geometry of the vents. , for bass reflex speakers, depending on the characteristics of the speakers.

Regarding the geometry of the cavity, it is recognized that the parallelism of the inner walls of the cavity is conducive to the formation in the cavities of unsteady wave trains and parasitic standing waves. The presence of these vibratory modes affects the displacement of the membranes by creating intermodulation distortions and interferences which prevent the electro-acoustic enclosure from reaching an optimal level of reproduction of the sound signal. Also, to avoid the parasitic emissions generated by the parallel walls, it has been imagined to modify the surface condition of the interior walls of the cavities, for example in a random manner, to scramble the acoustic waves emitted at the back of the membrane and thus limit this problem.

A first technique consists in forming surface irregularities by randomly digging the inner wall of the cavity.

Of particular note, publication CN 2 279 755, a monobloc electro-acoustic enclosure made of stone, the load has an irregular surface in order to reduce vibrations and parasitic resonances.

JP 8,275,283 discloses an electro-acoustic chamber formed by digging a stone by means of a rounded tool forming a random rough internal surface to limit the resonance of the walls.

The experiments conducted with this kind of electro-acoustic speakers have, however, not been satisfactory.

Another technique, used by some electroacoustic loudspeaker manufacturers, is to provide, inside the cavity, coatings, for example corrugated, foam type, for example compact synthetic foam with low density whose function is to absorb or diffract in part the energy of the waves inside the cavity.

These solutions are, however, not satisfactory.

Moreover, it has been shown that cavities of non-parallelepipedic shapes make it possible to significantly reduce the parasitic phenomena associated with the waves generated by the parallel walls of traditional electroacoustic loudspeakers.

It is known, in particular publication DE 8 222 350 which describes an electro-acoustic chamber whose wall is formed of natural stone gravels connected by a resin, the electro-acoustic enclosure having a spherical shape.

The publication DE 4 227 696 describes an enclosure electro-acoustic comprising two semispherical shapes assembled together and whose walls are made of concrete.

The publication CN 2 489 531 describes an electro-acoustic enclosure whose external appearance simulates that of a natural stone and whose inner walls have an irregular surface state and are not parallel to each other.

The different geometries tested nevertheless do not allow to reach a satisfactory level of acoustic reproduction.

The present invention aims to remedy these drawbacks by proposing a high-fidelity electro-acoustic loudspeaker enabling the "cash signature" to be canceled and the backward waves returning to the front to be eliminated in order to obtain the ideal conditions for faithful reproduction of recorded music.

Presentation of the invention

The invention relates to an electroacoustic enclosure comprising walls defining at least one cavity provided with an opening closed by at least one loudspeaker comprising a membrane whose front surface emits a front wave and whose rear surface emits a rear wave. , said loudspeaker being thus defined in particular by the position of its front acoustic center for said front wave, by the position of its rear acoustic center for said rear wave and by its central axis passing through the front and rear acoustic centers. Said electro-acoustic chamber is remarkable in that it is called "close", that is to say free of vent and in that the shape of said cavity is such that its intersection with any plane containing said central axis said speaker is at least a portion of an ellipse having particular characteristics as a distinct first focus and a second focus and a major axis whose intersection with said ellipse defines a first extreme point and a second extreme point, respectively distributed on either side of the first and second foci, said major axes of said ellipses being arranged to be substantially merged with said central axis of said speaker, said opening being secant to said ellipses so that said second end points of each ellipse are located on the other side of said opening relative to the cavity, in that the cavity is arranged so that said first extreme points are substantially merged, said first foci are substantially merged, and at least part of said second foci are distant, and in that said speaker and said cavity are arranged so that said rear acoustic center of said speaker is located between said seco nds foci farthest from each other of said ellipses forming said cavity or coincident with one of said second foci furthest away from each other.

Due to this particular arrangement, the rear acoustic waves can not come out, they are trapped by a phenomenon that can be described as an "acoustic black hole".

The electro-acoustic enclosure according to the invention thus achieves unmatched sound reproduction quality. Indeed, only the waves emitted by the front surface of the speaker diaphragm out of the electro-acoustic enclosure. The acoustic center behind the loudspeaker being framed by the range of variation of the second foci of all the ellipses characterizing the geometry of the cavity, the waves emitted by the rear surface of the speaker's membrane, after reflection on the walls of the the cavity, converge towards the first focus, single. Thus, the parasitic waves emitted by the rear surface of the membrane are trapped and eventually disappear by the interplay of internal friction of viscosity between the air molecules contained in the cavity, without damaging the sound emitted by the front surface of the membrane the speaker of the electro-acoustic speaker.

According to a preferred embodiment, the shape of said cavity is an ellipsoid of revolution so that all the ellipses are identical and that their first foci, their second foci, their first extreme points and their second extreme points are substantially merged, and said speaker and said cavity are arranged so that the median position of said rear acoustic center of said speaker is substantially merged with the second foci of said ellipses.

Said walls of said cavity are preferably monobloc and made of a material whose density is greater than 1600 kg / m ³ by molding and / or machining.

Said material constituting the block forming said walls of said cavity is advantageously heterogeneous and coherent.

According to a preferred embodiment, said walls of said cavity are made of a dense and homogeneous material such as plaster, cement and some plastic materials.

According to another preferred embodiment, said walls of said cavity are made of a metallic material.

The electro-acoustic enclosure preferably comprises at least a first and a second cavity. Brief description of the drawings

Other advantages and features will become more apparent from the description which follows with reference to the appended figures among which:

- Figure 1 is a schematic sectional view of an electro-acoustic chamber according to the invention,

FIG. 2 is a diagrammatic view illustrating the shape of the cavity of the electro-acoustic enclosure according to the invention, the vertical and horizontal sectional planes being folded in the same plane, and the opening of the electromagnetic enclosure. acoustic being schematized by a vertical line,

- Figure 3 is a schematic sectional view of the cavity of the electro-acoustic chamber illustrating the phenomenon of "acoustic black hole" in which the parasitic waves flow, after reflections by the walls in both directions of movement represented by means arrows, between the first focus and the second focus of each specific ellipse delimiting the cavity of the electro-acoustic enclosure.

Best way to realize the invention

The rest of the description is based on a two-way electro-acoustic enclosure. It is understood that the invention applies to any type of electroacoustic speakers, regardless of its number of channels.

With reference to FIG. 1, the electroacoustic enclosure 10 according to the invention comprises a first cavity 1 and a second cavity 2, preferably made of a block of single solid material. Each first and second cavity 1, 2, is provided with an opening 11, 21, closed respectively by a first speaker 12 and a second speaker 22. In a variant embodiment not shown, the electro-acoustic enclosure is formed by the assembly of blocks, each block corresponding to a path of the electro-acoustic enclosure and having at least one cavity closed by at least one speaker. As illustrated, this electro-acoustic enclosure 10 is preferably called "close", that is to say free of vent.

The first speaker 12 (or electrodynamic transducer) comprises a membrane whose front surface emits a front wave and whose rear surface emits a rear wave. The first speaker 12 is thus characterized in particular by its front acoustic center, its rear acoustic center A1 and by its central axis X1-X1 'passing through the front and rear acoustic centers A1 of the first loudspeaker 12. The second loudspeaker 12 speaker 22 (or electrodynamic transducer) also has a membrane whose front surface emits a front wave and the rear surface emits a back wave. The second loudspeaker 22 is thus characterized in particular by its front acoustic center, its rear acoustic center A2 and its central axis X2-X2 'passing through the front and rear acoustic centers A2 of the second loudspeaker 22.

The front acoustic center of a loudspeaker is known to those skilled in the art. Indeed, it is well known that an acoustic wave is a local variation of the pressure due to the propagation of an overall motion of air molecules and that each spherical wave has an acoustic center which is the point in 1 space located at the origin of said acoustic wave. By analogy with waves on the surface of the water of a basin, the center of the wave is the place where a stone was thrown into the water. In particular, see John Vanderkooy's article "The Acoustic Center: A New Concept for Loudspeakers at Low Frequencies" published in the AES Convention Paper 6912, 121st Convention dating from 5-8 October 2006.

Furthermore, each surface element of the membrane of the first and second loudspeakers 12, 22, which respectively close the first and second cavities 1, 2 of the electro-acoustic enclosure 10, when it moves, pushes the air on one side and aspire on the other and reciprocally, thereby creating a front wave and a rear wave generated on both sides of said membrane, each of said front and rear waves being different and each having its own acoustic center , namely respectively the front acoustic center and the rear acoustic center A1, A2. These two front and rear acoustic centers A1, A2 determining the central axis XI, XI ', X2, X2' of said loudspeaker 12, 22.

In addition, concerning the determination of the front and rear acoustic centers A1, A2, it is well known to those skilled in the art that it is necessary to isolate the front wave with respect to the rear wave by using tubes with at their end a suitable impedance (without reflection) and experimentally search for an iso-pressure surface. We then find a sphere whose center is the acoustic center of the front wave. It is necessary to proceed in a similar way to determine the rear acoustic center A1, A2. Finally, it is well known to those skilled in the art that the position of the front and rear centers A1, A2 varies somewhat according to the sound frequency. The geometry of the first cavity 1 is remarkable in particular by the fact that its. intersection with any plane containing the central axis Xl-Xl 'of the first speaker 12 is a portion of an ellipse Eli. Thus, the intersection with a first plane containing the central axis X1-X1 'of the first speaker 12 is a portion of an ellipse Eli. FIG. 2 thus makes it possible to illustrate the two elliptical portions Ell and E12 obtained by the intersection of the first cavity 1 with first and second distinct sectional planes, for example a vertical sectional plane and a horizontal sectional plane.

As can be seen from FIG. 2, and from FIG. 1, in which a portion of the ellipse Ell is represented by a dotted line:

the ellipse Ell is characterized in particular by its first focus Fil, its second focus Fil 'and its large axis Xll-Xll' whose intersection with the ellipse Ell defines the first extreme point P11 and the second extreme point P11 ' , the first and second extreme points Pli, Pli 'being respectively distributed on each side of the first and second filament and fil' focal points,

the ellipse E12 is characterized in particular by its first focus F12, its second focus F12 'and its major axis X12-X12' whose intersection with ellipse E12 defines the first end point P12 and the second end point P12 ', the first and second extreme points P12, P12 'being respectively distributed on each side of the first and second foci F12 and F12'.

The first focus Fil of the ellipse Ell is distant from the second focus Fil 'of the same ellipse Ell. In addition, the major axis Xll-Xll 'of the ellipse Ell is substantially coincidental with the central axis X1-X1' of the loudspeaker 12. Similarly, the first focus F12 of the ellipse E12 is distant from the second focus F12 'of the same ellipse E12. In addition, the major axis X12-X12 'of the ellipse E12 is substantially coincidental with the central axis X1-X1' of the first speaker 12. By "substantially merged" is meant here that the tolerance of the lateral setting and the angular setting of the major axis Xll-Xll 'of the ellipse Ell with respect to the central axis Xl-Xl' of the loudspeaker 12 is defined by the maximum precision allowed by the machine implemented by the Man of the art to perform this operation. The same goes for the long axis X12-X12 'of the ellipse E12. The opening 11 is intersecting with ellipses Ell, E12 so that the second end points P11 ', P12' are located on the other side of the opening 11 adapted to receive the first speaker 12 with respect to cavity 1 according to Figures 1 and 2. The second extreme points P11 ', P12' are virtual points shown in the figures for the purpose of understanding the shape of the first cavity 1.

As can be seen in FIGS. 1 and 2, the first foci Fil, F12 of ellipses Ell, E12 are substantially merged and the second foci Fil ', F12' of ellipses Ell, E12 are distant. In addition, the rear acoustic center Al of the first speaker 12 is located between the second foci Fil 'and F12' respectively ellipses Ell, E12.

As described above, the rear acoustic center Al has a variable position depending on the sound frequency. Thus, the position of the rear acoustic center A1 varies along a segment of the central axis X1-X1 'of the loudspeaker 12 whose ends correspond to the positions of the rear acoustic center A1 for the lowest frequency and for the highest frequency. One of the features of the invention is such that said segment of the central axis X1-X1 'is located between the second foci furthest away from each other, namely the second focus of the smallest of said ellipses Eli of the first cavity 1 and the second focus of the largest of said ellipses Eli of the first cavity 1.

The term "small ellipse" denotes an ellipse whose first and second extreme points are the closest, and conversely, "large ellipse", an ellipse whose first and second extreme points are the furthest apart. Thus, in accordance with the preceding explanations and with reference to FIG. 3, the waves emitted by the rear surface of the membrane of the first loudspeaker 12 are trapped in the first cavity 1 by a kind of "acoustic black hole" phenomenon, related to the properties of the ellipses Eli of the cavity 1. The parasitic waves move between the first foci Fil and the second foci Fil ', in the two directions of circulation represented by means of the arrows C1 and C2, by bouncing against the walls of the first cavity 1. These parasitic waves eventually fade, by the interplay of internal friction of viscosity between the air molecules contained in the cavity, consecutive to their repeated reflections, without damaging the sound emitted by the front of the membrane of the first loudspeaker (not shown in FIG. 3) of the electro-acoustic enclosure 10.

Therefore, it is clear that it is important that the first cavity 1 is "closed", that is to say, free of vent, because the whole purpose of the invention is to remove said cash signature and the rear waves returning to the front of the enclosure substantially geometrically "trapping" the back wave within the first cavity 1.

With reference to FIG. 1, the geometry of the second cavity 2 is comparable to that of the first cavity 1. Thus its intersection by any plane containing the central axis X2-X2 'of the second speaker 22 is a portion of an ellipse E2i such that the ellipse E21 shown. The ellipse E21 is defined by its first focus F21, its second focus F21 'and its major axis X21-X21' whose intersection with the ellipse E21 defines the first end point P21 and the second end point P21 ', the first and second extreme points P21, P21 'being respectively distributed on either side of the first and second fireplaces F21 and F21 '. The first focus F21 of the ellipse E21 is distant from the second focus F21 'of the same ellipse E21. It is the same for the first foci F2i and the second foci F2i 'of the other ellipses E2i defining the second cavity 2. In addition, the major axis X21-X21' of the ellipse E21 is substantially coincident with the central axis X2 -X2 'of the second speaker 22. By "substantially merged" is meant here that the tolerance of the lateral setting and the angular setting of the major axis X21-X21' the ellipse E21 relative to the central axis X2-X2 ' second speaker 22 is defined by the maximum accuracy allowed by the machine implemented by the skilled person to perform this operation. The same is true for the major axes X2i-X2i 'of the other ellipses E2i defining the second cavity 2. The second extreme points P2i' are thus virtual points, in particular the second extreme point P22, represented in FIG. the needs of the understanding of the shape of the second cavity 2. The first foci F2i (whose first focus F21) ellipses E2i (whose ellipse E21) are substantially merged, and the second foci F2i 'ellipses E2i are distant . In addition, the rear acoustic center A2 of the second speaker 22 is located between the second foci F2i 'ellipses E2i.

As for the first cavity 1, the rear acoustic center A2 has a variable position depending on the sound frequency. Thus, the position of the rear acoustic center A2 varies along a segment of the central axis X2-X2 'of the loudspeaker 22 whose ends correspond to the positions of the rear acoustic center A2 for the lowest frequency and for the highest frequency. One of the features of the invention is such that said segment of the central axis X2-X2 'is located between the second foci furthest away from each other, namely the second focus of the smallest of said eli ellipses of the second cavity 2 and the second focus of the largest of said ellipses E2i of the second cavity 2.

Thus, as for the first cavity 1, the parasitic waves are trapped in the second cavity 2 between the first foci F2i and the second foci F2i 'between which they eventually fade, by the interplay of internal friction viscosity between the air molecules contained in the cavity, consecutive repeated rebounds against the walls of the second cavity 2. The sound emitted by the front surface of the membrane of the second speaker 22 of the electroacoustic enclosure 10 is not altered by these parasitic waves.

In this example, the electroacoustic enclosure 10 has an external shape corresponding at least in part to an ellipsoid, remarkable in particular by its first home F_3 and second home F3 'distant, and by its major axis X3-X3'. This ellipsoid is preferably an ellipsoid of revolution.

The single block of material is preferably a block having a density greater than 1600 kg / m3. For example, a heterogeneous and coherent material such as, for example, natural stone or ceramic is chosen. For example, natural, non-oriented, textured rocks may be used, in particular, biocetric limestones, oolitic limestones, and metamorphic limestones with densities ranging from about 1,600 kg / m3 to 2,900 kg / m3. It is also possible to use a trachy-andesite or so-called trachyandesite, that is to say a volcanic intraplate rock of the alkaline series, intermediate between a trachybasalte and a trachyte. These materials result either from the differentiation of alkaline basalts by fractional crystallization, or from mixtures between alkaline basalt and trachyte or rhyolite. These materials consist of calcareous sediments, possibly recombined under the influence of geological upheavals, offer a coherent structure of heterogeneous compounds whose properties allow them to behave in a completely neutral way in front of the direct excitation of the sound emissions produced by the speakers.

This neutrality is explained, on the one hand by the apparent porosity of the stone, constituted by the density of population and the geometry of its microscopic cells on its surface and whose properties, united under the name "tortuosity", produce the diffraction of acoustic waves and the weakening of the vibratory energy that penetrates the mass of stone. Indeed, the diffraction of the acoustic waves in the small cavities that constitute its porosity, combined with the very important difference between the YOUNG modules of compression and traction of the stone, explains that the excitation energy of the waves emitted the back of the membrane does not produce volumic waves, that is to say waves transmitted by the massive stone Thus, the vibrations caused by the acoustic waves in each first and second cavities 1, 2, do not are not transmitted in the mass of the stone. The absence of volumic waves within the massive stone causes the absence of vibrations of the external surfaces of the walls of the acoustic enclosure 10, thus avoiding the problem of "cash signature", namely the emission of waves acoustic parasites. The incident energy of the acoustic waves emitted from the rear of the speaker diaphragm 12, 22 remains at the inner surface of the stone cavity 1, 2 in the form of evanescent volumic waves. Good results have been obtained using the so-called "SAINT-RAPHAEL" stone whose density is 2,340 kg / m3 and whose apparent porosity is 12.03%. Even better results have also been obtained using the limestone "FOUSSANA" whose density is of the order of 2600 kg / m3 and whose apparent porosity is of the order of 3%. The limestone "FOUSSANA" made it possible to observe that the frequency amplitude response curves were more regular than those obtained with the "SAINT-RAPHAEL" stone.

The absence of a "cash signature", that is to say the vibratory neutrality obtained with the natural solid stone, can also be obtained by the inertia of other materials such as dense and homogeneous materials such as, for example , plaster, cement and some plastic materials. One can also advantageously choose a block made of metallic materials such as, for example, steels, cast irons, lead, copper, bronze, brass, silver, uranium or any suitable alloy whose mass. volume is close, or even much higher than that of natural stone.

In an alternative embodiment not shown, the cavities can be closed by several speakers.

In order to manufacture electroacoustic enclosures 10 according to the invention, a manufacturing method is implemented in which the number of cavities 1, 2 required is made by digging the front face of the block of material. This operation can advantageously be performed by means of industrial tools such as numerically controlled machines for example "five axes". With the same production means, it is possible to make the outer ellipsoid of the electroacoustic enclosure 10. When the cavities 1, 2 are made from moldable materials, the latter can be manufactured by molding.

The technical characteristics of the enclosure According to the invention, the electro-acoustic device 10 makes it possible to produce an acoustic seal which makes it possible to avoid the formation of stationary waves in the first cavity ^" 1 ^" and in the second cavity 2 which are stationary waves which would interfere with the movement of the membrane. speakers 12, 22 and would create unacceptable vibration nuisances.

Description of other embodiments

According to a preferred embodiment not shown, the shape or geometry of the first cavity 1 is an ellipsoid of revolution. Thus, the intersection of the first cavity 1 with any plane containing the central axis X1-X1 'of the first speaker 12 is a portion of an ellipse E1 and the intersection of the first cavity 1 with any plane perpendicular to the central axis X1-X1 'of the first speaker 12 is a circle.

All Eli ellipses are characterized in particular by their first and second homes distant from each other and their major axis whose intersection with ellipses Eli defines their first extreme point and their second extreme point, the first and second extreme points being respectively distributed on each side of the first and second homes Fil and Fil '

In the case of an ellipsoid of revolution, all the ellipses Eli are identical and therefore all the first foci are substantially merged, all the second foci are substantially merged, all the first extreme points are substantially merged and all the second points are substantially merged. .

In this particularly advantageous configuration for obvious reasons of simplicity of manufacture and implementation, the rear acoustic center Al of the loudspeaker 12 is located so that its position median is substantially confounded with the second focus ellipses Eli.

Here, the term "middle position" refers to the middle of the segment of the central axis X1-X1 'of the loudspeaker 12, the ends of which correspond respectively to the positions of the rear acoustic center A1 for the lowest frequency and for the highest frequency. .

Moreover, by "substantially confused" is meant here that the tolerance of said position is defined by the maximum precision allowed by the machine implemented by those skilled in the art to perform this operation.

In the case of a multi-way electro-acoustic enclosure, it goes without saying that the other cavities will have the same geometrical characteristics.

Possibilities of industrial application

The electro-acoustic enclosure 10 according to the invention can be used for any type of sound installation, by individuals, professionals and / or manufacturers. The electro-acoustic enclosure 10 according to the invention can also be manufactured according to an industrial process adapted to the larger or smaller scale needs to meet.

It is understood that the example described is only a particular illustration and in no way limiting the fields of application of the invention. Those skilled in the art may provide arrangements of size, shape and material to the particular embodiment and the manufacturing method without departing from the scope of the present invention.

Claims

1 - Electro-acoustic chamber (10) comprising walls defining at least one cavity (1; 2) provided with an opening (11; 21) closed by at least one loudspeaker (12; 22) comprising a membrane whose front surface emits a front wave and whose rear surface emits a back wave, said speaker (12; 22) thus being defined in particular by the position of its front acoustic center for said front wave, by the position of its rear acoustic center (A1; A2) for said rear wave and by its central axis (X1-X1 '; X2, X2') passing through the front and rear acoustic centers (A1; A2), said electro-acoustic chamber (10) being characterized by what is said to be "closed", that is to say, free of venting, and in that the shape of said cavity (1; 2) is such that its intersection with any plane containing said central axis (X1- X1 ', X2, X2') of said loudspeaker (12; 22) is at least a portion of an ellipse (Eli; E2i) having in particular as characteristics a first focus (Fli; F2i) and a second focus (Fli ';F2i') and a major axis (Xli-Xli ';X2i-X2i') whose intersection with said ellipse (Eli; E2i) defines a first extreme point (P1; ) and a second extreme point (Pli ', P2i'), respectively distributed on both sides of the first and second foci (Fli, Fli ', F2i, F2i'), said major axes (X1 - X1 '; X2i ') of said ellipses (Eli; E2i) being arranged to be substantially coincidental with said central axis (X1-X1'; X2, X2 ') of said speaker (12; 22), said opening (11; 21) being intersecting said ellipses (Eli; E2i) so that said second end points (P1 ';P2i') of each ellipse (Eli; E2i) are located on the other side of said ellipse opening (11; 21) relative to the cavity (1; 2), in that the cavity (1; 2) is arranged so that said first extreme points (P1; P2i) are substantially merged, said first foci (Fli; F2i) are substantially merged, and at least a portion of said second foci (Fli ';F2i') are spaced apart, and in that said speaker (12; 22) and said cavity (1; 2) are arranged so that said rear acoustic center (A1, A2) of said loudspeaker (12, 22) is located between said second foci (Fli ';F2i') furthest from each other of said ellipses forming said cavity (1; 2) or confused with one of said second foci (Fli ';F2i') furthest away from each other. 2 - electro-acoustic chamber (10) according to the preceding claim, characterized in that the shape of said cavity (1; 2) is an ellipsoid of revolution so that all the ellipses (Eli; E2i) are identical and that their first their second foci (Fli ', F2i'), their first extreme points (P1, P2i) and their second extreme points (P1 ', P2i') are substantially merged, and in that said said speaker (12; 22) and said cavity (1; 2) are arranged so that the median position of said rear acoustic center (A1; A2) of said speaker (12; 22) is substantially merged with the second foci (Fli '; F2i ') of said ellipses (Eli; E2i).

3 - electro-acoustic chamber (10) according to any one of claims 1 or 2, characterized in that said walls of said cavity (1; 2) are monobloc and made of a material whose density is greater than 1 600 kg / m ³ by molding and / or machining. 4 - electro-acoustic chamber (10) according to claim 3, characterized in that said material constituting the block forming said walls of said cavity (1; 2) is heterogeneous and coherent.

5 - electro-acoustic chamber (10) according to claim 3, characterized in that said walls of said cavity (1; 2) are made of a dense and homogeneous material such as plaster, cement and some plastic materials.

6 - electro-acoustic chamber (10) according to claim 3, characterized in that said walls of said cavity (1; 2) are made of a metallic material.

7 - electro-acoustic chamber (10) according to any one of the preceding claims, characterized in that it comprises at least a first and a second cavity (1; 2).