Acoustic enclosure with optimal acoustic transmission device, and associated acoustic enclosure system

Abstract

ACOUSTIC ENCLOSURE WITH OPTIMAL ACOUSTIC TRANSMISSION DEVICE, AND ASSOCIATED ACOUSTIC ENCLOSURE ASSEMBLY The present invention relates to an acoustic enclosure (1) comprising a box (2) in which at least one loudspeaker (3) is mounted, said box (2) comprising, for each loudspeaker (3), an opening (2a) closed by the front part of the associated loudspeaker (3) and a vent (4) opening to the outside, the acoustic enclosure (1) further comprising, for each loudspeaker (3), an acoustic transmission device (5) extending between an input end (5a) configured to receive sound waves emitted from the rear of the associated loudspeaker (3) and an output end (5b) opening into the associated vent (4),Each acoustic transmission device (5) has a constant characteristic length and cross-sectional area dimensioned such that the acoustic resistance of the acoustic transmission device (5) is identical to the acoustic resistance of the associated loudspeaker (3). Figure to be published with the abbreviation: Figure 1,

Description

Title of the invention: ACOUSTIC SPEAKER WITH OPTIMAL ACOUSTIC TRANSMISSION DEVICE, AND ASSOCIATED ACOUSTIC SPEAKER ASSEMBLY

[0001] The present invention relates to the field of acoustic speakers, and relates in particular to an acoustic speaker with an optimal acoustic transmission device and to an associated acoustic speaker assembly.

[0002] A conventional loudspeaker emits sound waves forward, but also sound waves backward. Indeed, when the loudspeaker membrane moves forward, the air in front of the membrane is compressed, while that located at the rear is rarefied, and conversely when the loudspeaker membrane moves backward, the air in front of the membrane is rarefied, while that located at the rear is compressed. Thus, when the loudspeaker reproduces audio content, its membrane moves forward and backward, creating an unwanted pressure or depression with each forward or backward movement. A sound wave is thus created in phase opposition with that of the original signal, inducing an acoustic problem.

[0003] In order to overcome this acoustic problem, it is known to place the loudspeaker in an acoustic enclosure in order to allow the loudspeaker to reproduce the original audio signal more faithfully.

[0004] The main types of existing acoustic enclosures are:

[0005] - the closed enclosure, in which the waves emitted towards the rear of the loudspeaker are isolated within the enclosure,

[0006] - the enclosure with vent, in which the waves emitted towards the rear of the loudspeaker join the waves emitted forward through a vent,

[0007] - the passive radiator enclosure, in which the vent is replaced by a loudspeaker bass without motor (coil and magnet), and

[0008] - the double speaker enclosure.

[0009] All these types of existing loudspeakers attempt to correct the defects of the loudspeakers with more or less effectiveness and introduce an undesired high order frequency response.

[0010] Complex solutions also exist to try to achieve an optimal and constant level at all required frequencies in the frequency range of the human ear (commonly accepted between 20Hz and 20kHz). However, these solutions often require several types of loudspeakers to cover the full frequency band, most of the time using at the same time loudspeakers bass, midrange and treble speakers, but sometimes also an additional separate subwoofer for the extreme bass.

[0011] The weaknesses of these solutions which use several loudspeakers are multiple:

[0012] - difficulty of having each loudspeaker at the same level,

[0013] - frequency overlap between speakers almost impossible to calibrate (requires graphic or parametric equalization for approximate correction),

[0014] - very sensitive to the physical characteristics of the loudspeaker,

[0015] - control of the phase shift according to the complex and often impossible (introduction of unwanted high-order filtering),

[0016] - very difficult overall equalization, and

[0017] - sensitive to the reverberations of the room where the acoustic enclosure is placed.

[0018] Some monitoring speakers, commonly used in recording studios, may also be based on acoustic transmission line speaker technology in which the speaker cabinet includes a long duct inside it that acts as a guide for the acoustic waves emitted from the rear of the speaker to a vent. However, these existing acoustic transmission line speakers do not cover the entire 20Hz - 20kHz frequency range and generally use several speakers in an attempt to achieve a wider spectral range. Some are capable of reaching a minimum frequency of around 40Hz but the speaker then reaches a very high price (i.e., several thousand euros).

[0019] Thus, no acoustic enclosure currently on the market makes it possible to obtain a flat spectral response over the entire 20Hz - 20kHz frequency range, while being inexpensive.

[0020] The present invention aims to solve the drawbacks of the prior art, by proposing an acoustic enclosure comprising an optimal acoustic transmission device which makes it possible to propagate the sound waves emitted from the rear of the loudspeaker towards a vent, and whose characteristic length and characteristic cross-section are dimensioned in such a way that the acoustic resistance of the acoustic transmission device is identical to the acoustic resistance of the loudspeaker, which makes it possible to obtain, with a single loudspeaker, a flat spectral response over a very wide frequency band, for example over the entire frequency range 20Hz - 20kHz.

[0021] The present invention thus makes it possible to improve the audio reproduction of the acoustic speaker which can provide the most faithful sound possible with maximum efficiency in comparison with traditional speakers currently on the market.

[0022] The present invention therefore relates to an acoustic enclosure comprising a box in which at least one loudspeaker is mounted, said box comprising, for each loudspeaker, an opening closed by the front part of the associated loudspeaker and a vent opening onto the outside, the acoustic enclosure further comprising, inside the box and for each loudspeaker, an acoustic transmission device extending between an input end configured to receive the sound waves emitted from the rear of the associated loudspeaker and an output end opening into the associated vent, said acoustic transmission device being configured to propagate the sound waves emitted from the rear of the associated loudspeaker towards the associated vent, characterized in that each acoustic transmission device has a characteristic length and a constant characteristic cross-section,said characteristic length and said characteristic cross-section being dimensioned such that the acoustic resistance of the acoustic transmission device is identical to the acoustic resistance of the associated loudspeaker.

[0023] Thus, dimensioning the acoustic transmission device so that its acoustic resistance is equal to that of its loudspeaker makes it possible to obtain maximum acoustic power and maximum efficiency of the acoustic enclosure, in addition to a flat spectral response of the acoustic enclosure over a very wide frequency band (for example, over the entire frequency range 20Hz - 20kHz) due to the constancy of the cross-section of the acoustic transmission device.

[0024] The cross-section of the acoustic transmission device must remain constant over the entire length of the acoustic transmission device in order to ensure constant acoustic resistance of the acoustic transmission device, regardless of the frequency above the low cut-off frequency of the acoustic transmission device. Below the latter, the acoustic resistance of the acoustic transmission device collapses.

[0025] The acoustic transmission device thus ensures constant acoustic power regardless of the frequency above the low cut-off frequency of the acoustic transmission device.

[0026] The acoustic transmission device allows optimal control of the movement of the loudspeaker membrane, allowing a reduction in the physical constraints on it, and therefore allows a greater longevity of the loudspeaker to be guaranteed as well as an increase in its admissible power.

[0027] The acoustic transmission device allows an increase in the total efficiency of the acoustic enclosure and therefore a reduction in the return to the amplifier. reactive power audio harmful to digital amplifiers (Class D) especially in low frequencies.

[0028] The use of small loudspeakers can ensure a maximum bandwidth of up to 20 kHz. Larger loudspeakers will not be able to reach 20 kHz. The use of small loudspeakers will not affect the low cut-off frequency of the acoustic transmission device. Only the power will be reduced, so it will be sufficient to add several acoustic enclosures to achieve the desired power.

[0029] With the present invention, unlike traditional speakers, all edge effects are corrected.

[0030] The present invention is based on acoustic transmission line technology which allows, in the acoustic domain, a strict control of the frequency spectrum of the acoustic enclosure. It can provide a flat spectral response from the highest to the lowest frequencies, where the latter are defined by the length of the acoustic transmission line following a simple linear relationship.

[0031] The acoustic enclosure according to the invention is independent of the resonance frequency of the at least one loudspeaker. Even if the loudspeaker has a resonance frequency of 80 Hz or even 120 Hz, this will not prevent the acoustic enclosure from reaching lower frequencies such as 20 Hz or even lower only depending on the length of the acoustic transmission device.

[0032] Since the acoustic transmission line architecture has no limit in the high frequencies, the highest frequency of the acoustic enclosure will be limited by the maximum frequency that the at least one loudspeaker can provide.

[0033] The present invention makes it possible, with a single loudspeaker, to cover at least the entire frequency range 20Hz - 20kHz. Furthermore, with the present invention, there is no frequency overlap management, nor uncontrolled phase shift, which makes it possible to reduce unwanted resonance / rejection behavior.

[0034] Virtually no equalization is necessary with the acoustic enclosure according to the invention, which allows a frequency response made flat by the acoustic transmission line technology, self-compensation for loudspeaker defects, and less sensitivity to room reverberations.

[0035] Since the acoustic resistance of the acoustic transmission device is much higher than the acoustic resistance of a room (having a large volume compared to that of the acoustic transmission device and therefore no constraints on air pressure variations), this makes the frequency response of the acoustic enclosure of the present invention virtually independent of its location as well as the size and furnishings of the room in which it is installed. In contrast, conventional acoustic enclosures generally have low acoustic resistance and non-constant in frequency, which makes them very dependent on the configuration of the rooms.

[0036] The acoustic enclosure according to the invention has a high power efficiency (acoustic power / electrical power) for all frequencies: use of both the front and rear acoustic power of the loudspeaker (the rear acoustic power being reproduced through the vent with the same frequency response as the front acoustic power by simply adding a fixed phase shift (identical to the reverberation of a wall)), high dynamic range, ability to obtain a full range in a small volume (for example, 20Hz - 20kHz with a 2 liter enclosure for 20 Watts RMS in equivalent acoustic power), the minimum response frequency does not depend on the resonance frequency of the loudspeaker (for example, 20Hz can be achieved with a loudspeaker having a resonance frequency of 80Hz or even 120Hz), no need for a separate subwoofer.

[0037] The overall cost of the solution is reduced: a low-end loudspeaker is sufficient to obtain a high-level acoustic result (the solution can be used for professional acoustic solutions), compatibility with class D amplifiers even at low frequencies (low reactive power feedback), fully scalable in power by association of several acoustic speakers without impact on the frequency response or on the phase shift.

[0038] According to a particular characteristic of the invention, the characteristic length Lolt (in meters) of the acoustic transmission device is defined according to the following equation:

[0039] Lolt = 4^,

[0040] where c is the speed of sound in air (in m / s), and Fc is the desired low cutoff frequency of the acoustic transmission device (in Hz).

[0041] Thus, the choice of the low cut-off frequency of the acoustic transmission device makes it possible to define the characteristic length of the latter.

[0042] According to a particular characteristic of the invention, the surface SuLT (in m2) of the characteristic cross-section of the acoustic transmission device is defined according to the following equation:

[0043] Çw __QLÆ£, ^ULT ~ PrHP Lolt

[0044] where PO is the atmospheric pressure (in Pa), PrHP is the maximum pressure (in Pa) exerted on the air by the membrane of the associated loudspeaker, VoHp is the maximum volume of air (in m3) displaced by the membrane of the associated loudspeaker, and Lolt is the characteristic length (in m) of the acoustic transmission device.

[0045] Thus, once the characteristic length Lolt of the acoustic transmission device is defined, knowledge of the PrHp and VoHp values ​​associated with the loudspeaker speaker allows you to define the SuLT value of the acoustic transmission device allowing you to obtain an acoustic resistance of the acoustic transmission device identical to that of the loudspeaker.

[0046] According to a particular characteristic of the invention, the characteristic cross-section of the acoustic transmission device is one of circular, oval, rectangular, and polygonal.

[0047] It should be noted that any other shape is possible for the characteristic cross-section of the acoustic transmission device, the main thing being that the value of the surface area of ​​the characteristic cross-section is constant over the entire length Lolt.

[0048] The shape of the cross-section of the acoustic transmission device may, for example, be circular, so that the acoustic transmission device constitutes a tubular duct. The shape of the cross-section may also be rectangular to optimize the size of the acoustic enclosure.

[0049] According to a particular characteristic of the invention, the acoustic enclosure comprises a plurality of identical and adjacent loudspeakers, a common opening for the plurality of loudspeakers, a common vent for the plurality of loudspeakers and a common acoustic transmission device for the plurality of loudspeakers, said common acoustic transmission device having a length corresponding to the characteristic length and a cross-section corresponding to the characteristic cross-section multiplied by the number of loudspeakers.

[0050] Thus, the plurality of loudspeakers mounted adjacent in the same box are associated with the same acoustic transmission device, this increases the surface area of ​​displaced air and therefore the volume of displaced air, which has the consequence of increasing the surface area of ​​the cross-section of the common acoustic transmission device and therefore the volume of the acoustic enclosure. Thus, for example, an enclosure with two loudspeakers is equivalent in terms of volume and admissible power to two enclosures each coupled with a single loudspeaker.

[0051] According to a particular characteristic of the invention, each acoustic transmission device comprises one of an acoustic transmission line arranged between its input end and its output end, and several parallel acoustic transmission lines arranged between its input end and its output end.

[0052] Thus, the acoustic transmission device comprises either a single acoustic transmission line having the characteristic cross-section, or several parallel acoustic transmission lines whose sum of the cross-sections is equal to the characteristic cross-section.

[0053] Each acoustic transmission line may include one or more bends (e.g., to be serpentine-shaped) so as to reduce the volume of the enclosure box. However, for simplicity of design, it is preferable to have as few bends as possible.

[0054] According to a particular characteristic of the invention, the acoustic enclosure further comprises, for each acoustic transmission device, an anti-resonance device configured to attenuate the resonances of the structural elements of the acoustic enclosure.

[0055] Thus, the anti-resonance device makes it possible to attenuate the resonances of the structural elements of the acoustic enclosure due to the shape of the acoustic transmission device.

[0056] According to a particular characteristic of the invention, the acoustic enclosure comprises a single acoustic transmission device, the acoustic enclosure further comprising internal separation walls arranged in parallel inside the box to form a path between the rear of the at least one loudspeaker and the vent, constituting a serpentine-shaped acoustic transmission line between the input end and the output end of the acoustic transmission device.

[0057] Thus, the staggered arrangement of the parallel internal separating walls in the box makes it possible to create a path serving as an acoustic transmission line between the rear of the loudspeaker and the vent.

[0058] According to a particular characteristic of the invention, the acoustic transmission device comprises a single acoustic transmission line consisting of a sealed conduit having the characteristic length and the characteristic cross-section, the acoustic enclosure further comprising, as an anti-resonance device, a plurality of anti-resonance axes arranged inside the box, each anti-resonance axis passing through all of the parallel internal separation walls.

[0059] Thus, the anti-resonance axes make it possible to significantly reduce the internal resonances of the acoustic enclosure. However, they do not allow them to be completely cancelled out when used at high power.

[0060] According to a particular characteristic of the invention, each acoustic transmission device comprises a plurality of superimposed acoustic transmission lines, each acoustic transmission line consisting of a sealed conduit having the characteristic length, the sum of the cross-sections of the plurality of conduits corresponding to the characteristic cross-section of the acoustic transmission device.

[0061] Thus, for reasons of cancellation of any internal resonance of the acoustic enclosure, the characteristic cross-section can be divided into several separate cross-sections. This configuration ensures the absence of internal resonances that can seriously affect the quality of sound reproduction. Unlike anti-resonance axes, the solution by multiplying the sections ensures total cancellation of internal resonances. It is therefore a preferred solution, especially when the acoustic enclosure is subjected to high acoustic powers.

[0062] The present invention also relates to an acoustic enclosure assembly comprising a plurality of acoustic enclosures as described above, the loudspeakers of the plurality of acoustic enclosures being electrically connected to each other in at least one of series and parallel.

[0063] Thus, the combination of several acoustic speakers according to the invention makes it possible to increase the acoustic power, while maintaining a maximum bandwidth.

[0064] The plurality of acoustic enclosures will not affect the total frequency response or the phase of the acoustic signal but will multiply the total admissible power.

[0065] According to a particular characteristic of the invention, the plurality of loudspeakers are distributed into a plurality of groups of loudspeakers, each group of loudspeakers comprising an even number of loudspeakers electrically connected in parallel, the groups of loudspeakers being electrically connected in series, so that the electrical impedance of the loudspeaker assembly is compatible with an audio amplifier.

[0066] The most commonly used electrical impedance in audio amplifiers is 8 Ohms. Thus, in the case where the loudspeaker assembly is connected to an audio amplifier having an electrical impedance of 8 Ohms, the loudspeakers will be connected together so as to also have an electrical impedance of 8 Ohms.

[0067] To better illustrate the object of the present invention, preferred embodiments will be described below, by way of illustration and not limitation, with reference to the appended drawings.

[0068] In these drawings:

[0069] [Fig.l] is a schematic sectional view of an acoustic enclosure according to a first embodiment of the present invention;

[0070] [Fig.2] is a schematic sectional view of an acoustic enclosure according to a second embodiment of the present invention;

[0071] [Fig.3] is a schematic sectional view of an acoustic enclosure according to a third embodiment of the present invention;

[0072] [Fig.4] represents the evolution curve of the acoustic impedance of a line of acoustic transmission as a function of frequency;

[0073] [Fig.5] is a schematic diagram in the field of acoustics of an acoustic enclosure according to the present invention;

[0074] [Fig.6] represents the curve of evolution of the acoustic power of an acoustic transmission line as a function of its acoustic resistance;

[0075] [Fig.7] is a horizontal sectional view of an exemplary acoustic enclosure according to the first embodiment of the invention;

[0076] [Fig.8] is a perspective view of an acoustic enclosure assembly according to one embodiment of the invention;

[0077] [Fig.9] is a perspective view of an acoustic enclosure assembly according to another embodiment of the invention;

[0078] [Fig. 10] is a perspective view of an acoustic enclosure assembly according to yet another embodiment of the invention;

[0079] [Fig. 11] is a perspective view of an acoustic enclosure assembly according to yet another embodiment of the invention;

[0080] [Fig. 12] is a perspective view of an acoustic enclosure assembly according to yet another embodiment of the invention;

[0081] [Fig. 13] is a perspective view of an acoustic enclosure assembly according to yet another embodiment of the invention;

[0082] [Fig. 14] is a schematic diagram of an acoustic enclosure assembly according to a particular embodiment of the invention;

[0083] [Fig. 15] is a schematic diagram of an acoustic enclosure assembly according to another particular embodiment of the invention;

[0084] [Fig. 16] is a schematic diagram of an acoustic enclosure assembly according to yet another particular embodiment of the invention;

[0085] [Fig. 17] is a diagram representing a loudspeaker with its acoustic transmission line;

[0086] [Fig. 18] is a diagram showing an acoustic transmission line;

[0087] [Fig. 19] is a vertical sectional view of an acoustic enclosure according to a first variant of the first embodiment of the invention; and

[0088] [Fig.20] is a vertical sectional view of an acoustic enclosure according to a second variant of the first embodiment of the invention.

[0089] Referring to [Fig. 1], it can be seen that there is shown an acoustic enclosure 1 according to a first embodiment of the present invention.

[0090] The acoustic enclosure 1 comprises a box 2 in which a loudspeaker 3 is mounted.

[0091] The box 2 comprises an opening 2a closed by the front part of the loudspeaker 3 and a vent 4 opening onto the outside.

[0092] The acoustic enclosure 1 further comprises, inside the box 2, an acoustic transmission device 5 in the form of an acoustic transmission line extending between an input end 5a, formed in a chamber 6 in which the loudspeaker 3 is arranged and configured to receive the sound waves emitted from the rear of the loudspeaker 3, and an output end 5b opening into the vent 4.

[0093] Since the opening 2a and the vent 4 are formed on the same side of the box 2, the acoustic transmission device 5 is angled. However, the acoustic transmission device 5 could also be straight in the case where the opening 2a and the vent 4 are formed on two opposite sides of the box 2, without departing from the scope of the present invention.

[0094] The acoustic transmission device 5 is configured to propagate the sound waves emitted from the rear of the loudspeaker 3 towards the vent 4.

[0095] The acoustic transmission device 5 has a characteristic length and a constant characteristic cross-section, said characteristic length and said characteristic cross-section being dimensioned such that the acoustic resistance of the acoustic transmission device 5 is identical to the acoustic resistance of the loudspeaker 3.

[0096] Thus, dimensioning the acoustic transmission device so that its acoustic resistance is equal to that of its loudspeaker makes it possible to obtain maximum acoustic power and efficiency with a flat spectral response of the acoustic enclosure over the entire frequency range 20Hz - 20kHz. The cross-section of the acoustic transmission device 5 must remain constant along its length in order to guarantee constant acoustic resistance of the acoustic transmission device 5, whatever the frequency above the low cut-off frequency of the acoustic transmission device 5. Below the latter, the acoustic resistance of the acoustic transmission device 5 collapses.

[0097] The acoustic transmission device 5 allows optimal control of the movement of the membrane of the loudspeaker 3, allowing a reduction in the physical constraints on the latter, and therefore making it possible to guarantee a greater longevity of the loudspeaker 3 as well as an increase in the admissible power thereof.

[0098] The acoustic transmission device 5 allows an increase in the total efficiency of the acoustic enclosure 1 and therefore a reduction in the return to the audio amplifier of reactive power which is harmful for digital amplifiers (Class D) particularly in the low frequencies.

[0099] The acoustic enclosure 1 according to the invention is independent of the resonance frequency of the loudspeaker 3. Even if the loudspeaker 3 has a resonance frequency of 80 Hz or even 120 Hz, this will not prevent the acoustic enclosure 1 from reaching

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] [YES]

[0112] lower frequencies such as 20 Hz or even lower, the low frequency being solely dependent on the length of the acoustic transmission device 5. Since the acoustic transmission line has no limit in the high frequencies, the highest frequency of the acoustic speaker 1 will be limited by the maximum frequency that the loudspeaker 3 can deliver. The overall cost of the solution is thus reduced, given that a low-end 3-way speaker is sufficient to achieve a high-level acoustic result. The characteristic cross-section of the acoustic transmission device 5 may, for example, have a circular, oval, rectangular or polygonal shape. It should be noted that any other shape is possible, the main thing being that the value of the surface area of ​​the characteristic cross-section is constant over its entire length. For example, the shape of the cross-section of the acoustic transmission device 5 may be circular, so that the acoustic transmission device 5 constitutes a tubular duct. The shape of the cross-section may also be rectangular to optimize the size of the acoustic enclosure 1. The characteristic length Lolt (in meters) of the acoustic transmission device 5 is defined according to the following equation: ^LT = WÇ ' where c is the speed of sound in air (in m / s), and Fc is the desired low cut-off frequency of the acoustic transmission device 5 (in Hz). Furthermore, the surface area SuLT (in m2) of the characteristic cross-section of the acoustic transmission device 5 is defined according to the following equation: PraP Lolt where PO is the atmospheric pressure (in Pa), PrHP is the maximum pressure (in Pa) exerted on the air by the membrane of the loudspeaker 3, VoHp is the maximum air volume (in m3) displaced by the membrane of the loudspeaker 3, and Lolt is the characteristic length (in m) of the acoustic transmission device 5. Referring to [Fig. 2], it can be seen that there is shown an acoustic enclosure 7 according to a second embodiment of the present invention. The common elements between the first embodiment of the invention in [Fig.l] and this second embodiment of the invention bear the same reference number, and will not be described in more detail here when they are of identical structures. The acoustic enclosure 7 according to the second embodiment is identical to the acoustic enclosure 1 according to the first embodiment, except that it further comprises:

[0113] - a second loudspeaker 8 arranged in a second chamber 9 of the box 2 and of which the front part closes a second opening 2b formed in the box 2;

[0114] - a second vent 10 opening onto the outside; and

[0115] - a second acoustic transmission device 11 in the form of a line of acoustic transmission extending between an input end 11a, formed in the second chamber 9 and configured to receive the sound waves emitted from the rear of the second loudspeaker 8, and an output end 11b opening into the second vent 10.

[0116] The second acoustic transmission device 11 is configured to propagate the sound waves emitted from the rear of the second loudspeaker 8 towards the second vent 10. The second acoustic transmission device 11 has a characteristic length and a constant characteristic cross-section, said characteristic length and said characteristic cross-section being dimensioned such that the acoustic resistance of the second acoustic transmission device 11 is identical to the acoustic resistance of the second loudspeaker 8.

[0117] It should be noted that the acoustic enclosure 7 could also comprise any number of loudspeakers, each associated with a separate vent and a separate acoustic transmission device, without departing from the scope of the present invention.

[0118] If we refer to [Fig.3], we can see that there is shown an acoustic enclosure 12 according to a third embodiment of the present invention.

[0119] The elements common to the second embodiment of the invention in [Fig.2] and this third embodiment of the invention bear the same reference number, and will not be described in more detail here when they are of identical structures.

[0120] The acoustic enclosure 12 according to the third embodiment is identical to the acoustic enclosure 7 according to the second embodiment, except that:

[0121] - the two loudspeakers 3 and 8 are identical, adjacent and arranged in a common room 6 of box 2;

[0122] - the acoustic enclosure 12 has a common opening 2a for the two loudspeakers speakers 3 and 8;

[0123] - the acoustic enclosure 12 has a common vent 13 for the two loudspeakers 3 and 8; and

[0124] - the acoustic enclosure 12 has a common acoustic transmission device 14 for the two loudspeakers 3 and 8, in the form of an acoustic transmission line extending between an input end 14a, formed in the common chamber 6 and configured to receive the sound waves emitted from the rear of the two loudspeakers 3 and 8, and an output end 14b opening into the common vent 13.

[0125] The common acoustic transmission device 14 has a length corresponding to the characteristic length (i.e., the length of the acoustic transmission device 5 according to the first embodiment) and a cross-section corresponding to the characteristic cross-section multiplied by the number of loudspeakers (i.e., the cross-section of the acoustic transmission device 5 according to the first embodiment multiplied by two).

[0126] It should be noted that the acoustic enclosure 12 could also comprise any number of adjacent loudspeakers, with a common vent 13 and a common acoustic transmission device 14, without departing from the scope of the present invention.

[0127] As indicated above, for each of the acoustic transmission devices 5, 11 and 14 of the three acoustic enclosures 1, 7 and 12, the parameters to be taken into account to obtain a flat spectral response are its length and its cross-section (or its diameter in the case of a tubular conduit type transmission line).

[0128] Since the cross-section of the acoustic transmission line impacts the spectral response, it must be constant along the entire length of the acoustic transmission line to achieve a flat response.

[0129] The larger the cross-section of the acoustic transmission line, the more air will be displaced. On the other hand, the larger the cross-section of the acoustic transmission line, the less the air will be compressed and the less it will correct the loudspeaker defects. This is why the section of the acoustic transmission line must be chosen optimally to maximize the acoustic power. This is due to the volume of air displacement that must be transformed into compression by the acoustic transmission line to transmit the acoustic power acting as an acoustic resistance.

[0130] The length of the acoustic transmission line defines the minimum permissible frequency, i.e. the low cut-off frequency of the acoustic transmission device.

[0131] The low cut-off frequency of the acoustic transmission device is defined according to the equation:

[0132] Fc = ^~,

[0133] where Fc is the low cut-off frequency of the acoustic transmission line (in Hz), c is the speed of sound in air (approximately equal to 300 m / s), Lolt is the characteristic length of the acoustic transmission line (in meters), and the coefficient 4 is due to the fact that a quarter of the signal period needs to be taken into account.

[0134] For example, for a four-meter acoustic transmission line, the minimum admissible frequency will be:

[0135] Fc= g) ^19^.

[0136] [Fig.4] represents the curve of evolution of the acoustic impedance of an acoustic transmission line as a function of frequency (logarithmic scale).

[0137] We note that below Fc, the frequencies are acoustically short-circuited (the acoustic impedance will tend towards zero) and that the efficiency collapses very violently.

[0138] On the contrary, above Fc, the acoustic impedance is constant and equal to the acoustic resistance Rac of the acoustic transmission line.

[0139] The acoustic power Pac is defined by the air pressure multiplied by the air flow:

[0140] Pac - Air pressure^Air flow-

[0141] The air compression capacity of the acoustic transmission line is inversely proportional to the cross-section of the acoustic transmission line. The air displacement capacity of the acoustic transmission line is proportional to the cross-section of the acoustic transmission line. Thus, the optimal cross-section of the acoustic transmission line must be defined to obtain maximum transmission of acoustic power.

[0142] The loudspeaker's ability to move air depends linearly on the diameter of the loudspeaker cone and the travel of the loudspeaker cone, defined by the voltage (Vbobme) applied to the loudspeaker coil. The loudspeaker's ability to compress air depends linearly on the force applied to the cone, defined by the current (Ibobine) applied to the loudspeaker coil. [0i43] Air flow = VM„*KHP

[0144] Air pressure =

[0145] It should be noted that the KHp parameter can be compared to the KV parameter (turns per volt ratio) for a brushless motor (magnetic motor) which allows an efficiency of up to 98%. For a loudspeaker, the KHP parameter depends on the physical characteristics of the latter (diameter of the cone, elasticity of the damper, weight of the moving part, etc.). By analogy, an acoustic enclosure according to the present invention makes it possible to optimally restore the acoustic power by using a magnetic loudspeaker.

[0146] Furthermore, it should be noted that the acoustic transmission line allows the acoustic power to be transmitted from the rear of the loudspeaker to the vent without changing the spectrum but only with a fixed phase shift:

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154]

[0155]

[0156]

[0157]

[0158]

[0159]

[0160]

[0161]

[0162]

[0163] Duration of phase shift (in seconds) = Lolt (in meters) * 300ml s In this way, the acoustic power at the vent doubles the acoustic power at the front of the speaker, ensuring very high power efficiency. Based on this definition, the acoustic impedance of the acoustic transmission line in the permissible frequency range can be introduced. Using the analogy of the loudspeaker's electrical equations: Loudspeaker electrical power: Pwound^coil. Electrical impedance of the loudspeaker: R HP - coil T * coil and by the definition of acoustic power, the acoustic impedance of an acoustic transmission line in the permissible frequency range can be defined by: n Air pressure koclt - Flow rate It should be noted that, for a large section of the acoustic transmission line, the air pressure will tend towards zero, RacLT will then be close to zero. On the contrary, for a zero section of the acoustic transmission line (closed enclosure), the air displacement will be zero and RacLT will tend towards infinity. For the acoustic impedance of a loudspeaker, we obtain the following equations: RüCvp — rr H* * coil ahp ,¾ coil I reel RacHP — „ ^HP "^HP The acoustic enclosure according to the present invention can thus be modeled in the field of acoustics by the equivalent in the field of electricity. [Fig. 5] represents a voltage divider bridge in the field of acoustics, which comprises an acoustic model of a loudspeaker 15 and an acoustic model of an acoustic transmission line 16. Using the equivalent of the voltage divider bridge in the acoustic domain makes it possible to obtain: a?lt Ritepp aPhp where ApLT is the air pressure of the acoustic transmission line, ApHP is the loudspeaker air pressure, RacHp is the loudspeaker acoustic resistance, and RacLT is the acoustic resistance of the acoustic transmission line.

[0164]

[0165]

[0166]

[0167]

[0168]

[0169]

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176]

[0177]

[0178]

[0179]

[0180]

[0181]

[0182] And the equivalent of Ohm's law in the acoustic domain gives: Racjfp+RaciT ' where Ad is the air flow rate. Using the definition of acoustic power for an acoustic transmission line: Pa£LT = Ad*ApLT Combining the last three equations, we obtain: RaclT, Pacr T = ;-----—3 “ (R <u:Hp+RaCrr) H? Taking the derivative of this equation using RacLT as a variable, we see that the maximum power is found at: — RdC^p Maximum power is thus obtained when the acoustic resistance of the acoustic transmission line and the acoustic resistance of the loudspeaker are identical. [Fig.6] represents the acoustic power curve of the PacLT acoustic transmission line as a function of RacLT. Since RacLT evolves inversely proportionally to the cross-section of the acoustic transmission line, there is a direct link between the maximum power of the loudspeaker and the size of the acoustic transmission line and therefore the size of the acoustic enclosure. Consequently, at a given power of the loudspeaker, the maximum power restitution of a transmission line enclosure depends linearly only on its volume. The dimensioning of the acoustic transmission line section will now be described below. The definition of loudspeaker acoustic power is as follows: PacHP — PrHp^Depip (N / m2 * m3 / s). where PacHp is the loudspeaker's acoustic power, PrHp is the maximum pressure produced by the loudspeaker's membrane, and DeHP is the maximum airflow produced by the loudspeaker's membrane. The force exerted on the loudspeaker membrane is defined as follows: F°HP = HP^HP where Fohp is the force exerted by the speaker coil on the membrane, BHp is the magnetic field in the air gap of the speaker's permanent magnet, LbobmeHp is the length of the speaker coil wire, and IHP is the electric current flowing through the coil.

[0183]

[0184]

[0185]

[0186]

[0187]

[0188]

[0189]

[0190]

[0191]

[0192]

[0193]

[0194]

[0195]

[0196]

[0197]

[0198]

[0199]

[0200]

[0201]

[0202]

[0203]

[0204]

[0205] Since it is often difficult to obtain the value of the magnetic field in the air gap as well as the length of the coil wire, a simple method for determining the force exerted by the coil is described below. First, you must lay the speaker flat on its own (not mounted in an enclosure), membrane facing upwards. A weight must then be added to move the diaphragm to the maximum displacement of the loudspeaker within the manufacturer's linearity limit. This displacement will be reused in the calculation below, and will be noted CuHP. The force FoHp will therefore be the weight (in kg) added to the membrane multiplied by 9.81 N / kg- The pressure exerted by the loudspeaker membrane on the air is defined as follows: Fohp where PrHP is the maximum pressure exerted on the air by the speaker cone, FoHP is the force exerted by the speaker coil on the cone, and SuHP is the surface area of ​​the speaker cone. The surface area of ​​the loudspeaker membrane is defined as follows: StlHp = j where SuHp is the membrane surface area, and DHp is the membrane diameter. The volume of air displaced by the loudspeaker is defined as follows: where VoHP is the maximum air volume displaced by the speaker cone, SuHP is the speaker cone area, and CuHP is the maximum cone travel. [Fig. 17] represents these different parameters. Since the acoustic resistance of the loudspeaker is: PrHP Racnv=D^: and that the acoustic resistance of the acoustic transmission line is: RaCLT=D^ as the two acoustic resistances must be identical (Racl T = RacHP\ we obtain: _ ?rHP . DeLT ~ DeHP And, knowing that power is conserved in the system: PrLT*DeLT = PrHP*DeHP The last two equations imply that:

[0206] Pfu — Prfjp

[0207] = From hp

[0208] To define the relationships between pressures and air volumes, the following thermodynamic equation is used:

[0209] P^ = n*R*T,

[0210] where P is the pressure (in Pa), V is the volume (in m3), n is the quantity of matter (in mol), R is the universal constant of ideal gases ('8.314 JK '.mol1), and T is the absolute temperature (in K).

[0211] Since in the present case, the quantity of matter as well as the temperature remain constant, they will be replaced by the constant K:

[0212] n*R*T = K

[0213] Knowing that the volume of air to be taken into account in the system is the volume of the acoustic transmission line because above the minimum frequency defined by the length of the acoustic transmission line, the conduit of the acoustic transmission line can be considered as closed, given that below this frequency the air pressure will no longer have any effect on the system. This also explains the collapse of the acoustic resistance below this frequency.

[0214] K=VoLT*PQ

[0215] where K is a constant, VoLT is the volume of the acoustic transmission line, and PO is the atmospheric pressure (hereinafter assumed to be equal to 101000 Pa).

[0216] In the initial equation of thermodynamics, K can be replaced by its value:

[0217] P*V=VoLT*PV

[0218] Thus, in the general case, the relationship between the volume V and the pressure P is:

[0219] v Volt*pg v - P

[0220] The variables P and V are defined as follows:

[0221] P = PQ + PrLT,

[0222] where P is the system pressure, PO is the atmospheric pressure, and PrLT is the pressure exerted in the acoustic transmission line.

[0223] V=VoLT-dV,

[0224] where V is the system volume, VoLT is the volume of the acoustic transmission line, and dV is the volume variation in the acoustic transmission line.

[0225] [Fig. 18] represents these different parameters.

[0226] Thus, by combining the last three equations, we obtain: [°227] VolT-dV=^ rurr ijj

[0228] So: [°229] dV^Vo^-^ in rurrijr

[0230]

[0231]

[0232]

[0233]

[0234]

[0235]

[0236]

[0237]

[0238]

[0239]

[0240]

[0241]

[0242]

[0243]

[0244]

[0245]

[0246]

[0247] Therefore, factoring VoLT and putting everything on the same denominator, we get: dV = Vo Pr, 'LT P0+PrLT Knowing that the pressures of the loudspeaker and the acoustic transmission line must be the same, we obtain: dV = VoLT^ p^ppifp Knowing that the volume variation is the volume of air displaced by the speaker membrane: dV = VoHP, and that the volume of the acoustic transmission line is: = Sult*Lolt, where VoLT is the volume of the acoustic transmission line, SuLT is the cross-sectional area of ​​the acoustic transmission line, and Lolt is the length of the acoustic transmission line, we therefore obtain: You PrHP 'HP “ P0+PrHP or the surface area of ​​the section of the acoustic transmission line: CP(P-PrHP^VoHf - Prap • Ij>lt Knowing that the pressure exerted by the loudspeaker is negligible compared to atmospheric pressure PO, we finally obtain: ^LT P^np P°lt Referring to [Fig.7], it can be seen that there is shown an exemplary implementation of the acoustic enclosure 1 according to the first embodiment. The acoustic enclosure 1 shown in [Fig.7] has dimensions of 60 x 220 x 150mm with a four-meter acoustic transmission device 5 allowing a bandwidth of 20Hz-20kHz to be obtained. It should be noted that the use of an acoustic transmission device having a length greater than four meters makes it possible to reach frequencies lower than 20Hz. For example, a length of eight meters makes it possible to go down to 10Hz, which can be useful for certain acoustic installations. Thus, the acoustic transmission device of the present invention retains all its qualities and characteristics below 20Hz with an appropriate length, when this is useful for, for example, physically feeling very low frequencies even if the latter remain inaudible to the human ear.

[0248] The acoustic transmission device 5 is bent several times between its input end 5a and its output end 5b so as to reduce the size of the box 2 and therefore of the acoustic enclosure 1.

[0249] In particular, the acoustic enclosure 1 comprises vertical internal separation walls 17 arranged in a parallel and staggered manner inside the box 2 to form a path between the rear of the loudspeaker 3 and the vent 4, constituting a serpentine-shaped acoustic transmission line between the inlet end 5a and the outlet end 5b of the acoustic transmission device 5.

[0250] The acoustic enclosure 1 further comprises, as an anti-resonance device, a plurality of anti-resonance axes 18 arranged horizontally inside the box 2, each anti-resonance axis 18 passing through all of the vertical internal separation walls 17.

[0251] The anti-resonance axes 18 thus make it possible to significantly reduce the resonances of the structural elements of the acoustic enclosure 1. However, they do not make it possible to completely cancel them out when used at high power.

[0252] The acoustic enclosure 1 further has a lateral conduit 19 allowing the passage of a connecting wire therethrough, so as to electrically connect the loudspeaker 3 to a connector 20 arranged at the rear of the acoustic enclosure 1.

[0253] Since there must be no air leakage except from the vent 4, it is preferable to use silicone at the end (speaker 3 side) of the conduit 19 provided for the passage of the electric wire of the speaker 3. For the same reason, it is preferable to use a seal between the opening 2a of the box 2 and the front face of the speaker 3.

[0254] The volume of the box 2 of the acoustic enclosure 1 is thus composed of the volume of the acoustic transmission device 5 and the volume of the structural material required (namely, the internal separation walls 17) to construct the acoustic transmission device 5 in a rigid and stable manner.

[0255] Advantageously, the structural volume may range from 1 / 2 to 1 time the volume of the acoustic transmission device 5, depending on the material used for the acoustic enclosure 1.

[0256] As: Structural volume = (½ to 1) * VoLT

[0257] We therefore obtain:

[0258] Loudspeaker volume = VoLT + (½ to 1) * VoLT = (3 / 2 to 2) * VoLT

[0259] Referring to Figures 8 to 13, it can be seen that there are shown different acoustic enclosure assemblies 21, 22, 23, 24, 25 and 26 according to particular embodiments of the present invention.

[0260] Each acoustic enclosure assembly 21, 22, 23, 24, 25 and 26 comprises a plurality of acoustic enclosures 1 as described above, the loudspeakers 3 of the plurality of acoustic enclosures 1 being electrically connected to each other in at least one of series and parallel.

[0261] Thus, the combination of several acoustic enclosures 1 makes it possible to increase the acoustic power of the acoustic enclosure assembly 21, 22, 23, 24, 25 and 26, while maintaining a maximum bandwidth.

[0262] The plurality of acoustic enclosures 1 will not affect the total frequency response or the phase of the acoustic signal but will multiply the total admissible power.

[0263] Since the size of a loudspeaker 3 defines its maximum power, the relationship between the power and the size of an acoustic enclosure 1 according to the invention is constant and evaluated for a loudspeaker 3 of 10 Watts RMS at approximately 10 Watts RMS / dm3 or 10 Watts RMS / liter. This value can be decreased by increasing the acoustic impedance of the acoustic transmission device 5 and therefore by increasing the acoustic impedance of the loudspeaker 3.

[0264] For a given loudspeaker 3, given that the power of an acoustic enclosure 1 according to the invention depends linearly only on its size, the stacking of several acoustic enclosures 1 will linearly multiply the overall power of the system.

[0265] [Fig.8] represents an acoustic speaker assembly 21 in a sound bar using two acoustic speakers 1 of 20W (60 x 300 x 110mm) making it possible to obtain an overall power of 40W.

[0266] Figures 9 to 11 show shelf loudspeaker assemblies 22, 23 and 24 using 20W loudspeakers 1 (60 x 150 x 220mm).

[0267] The acoustic speaker assembly 22 of [Fig.9] comprises two acoustic speakers 1 spaced from each other (namely, an acoustic speaker 1 of 20W per channel), to obtain two small ambient (or "surround") speakers.

[0268] The acoustic speaker assembly 23 of [Fig. 10] comprises two 20W acoustic speakers 1 placed side by side, to obtain a central 40W speaker (with a total size of 60 x 300 x 220 mm).

[0269] The acoustic speaker assembly 24 of [Fig.l 1] comprises two groups of four acoustic speakers 1 of 20W superimposed (namely one group per channel), to obtain main speakers of 80W per channel (with a total size of 240 x 150 x 220mm or 120 x 300 x 220mm).

[0270] Figures 12 and 13 show high-power loudspeaker sets 25 and 26 using 20W loudspeakers 1 (60 x 75 x 440mm).

[0271] In [Fig.12], 4*8 = 32 20W loudspeakers are used to obtain an overall acoustic power of 640W (with a total size of 480 x 300 x 440mm or 240 x 600 x 440mm).

[0272] In [Fig.13], 16*8 = 128 20W loudspeakers are used to obtain an overall acoustic power of 2560W (with a total size of 960 x 600 x 440mm).

[0273] It should be noted that all the loudspeaker assemblies 21, 22, 23, 24, 25 and 26 will have the same bandwidth (for example, 20Hz to 20kHz).

[0274] The combination of several identical acoustic speakers also allows, if each of them is individually controlled very precisely by digital processing, a very precise spatialization of the sound. This method is very commonly used to simulate rear speakers from a single sound bar at the front, including a large number of loudspeakers (from ten to a few dozen) each controlled individually using the laser effect of light wave propagation, but applied here to sound waves. In the specific case of the present invention, this method is particularly interesting because the greater the number of loudspeakers, the greater the spatialization precision will be.

[0275] Referring to Figures 14 to 16, it can be seen that there are shown different examples of connections of loudspeakers 1 in loudspeaker assemblies 27, 28 and 29.

[0276] The plurality of loudspeakers 1 are distributed into a plurality of loudspeaker groups 30, each loudspeaker group 30 comprising an even number of loudspeakers 1 electrically connected in parallel, the loudspeaker groups 30 being electrically connected in series, so that the electrical impedance of the loudspeaker assembly 27, 28 or 29 is compatible with an audio amplifier (not shown in the Figures).

[0277] The most commonly used electrical impedance in audio amplifiers is 8 Ohms. Thus, in the case where the acoustic speaker assembly 27, 28 or 29 is connected to an audio amplifier having an electrical impedance of 8 Ohms, the acoustic speakers 1 will be connected together in such a way that the acoustic speaker assembly 27, 28 or 29 also has an electrical impedance of 8 Ohms.

[0278] The interconnection of several loudspeakers 1 has no impact on the overall spectrum and the phase shift insofar as all the loudspeakers 1 remain identical and powered by the same electrical signal.

[0279] For example, ten 10 Watts RMS loudspeakers with a volume of 10 liters will deliver 100 Watts RMS of acoustic power at all frequency ranges.

[0280] [Fig. 14] shows the connections of an exemplary loudspeaker assembly 27 comprising two groups 30 of two loudspeakers 1 (each with an 8 Ohm loudspeaker 3).

[0281] [Fig. 15] shows the connections of an exemplary loudspeaker assembly 28 comprising four groups 30 of four loudspeakers 1 (each with an 8 Ohm loudspeaker 3).

[0282] [Fig. 16] shows the connections of an exemplary loudspeaker assembly 29 comprising eight groups 30 of four loudspeakers 1 (each with a 4 Ohm loudspeaker 3).

[0283] Thus, each of the acoustic speaker assemblies 26, 27 and 28 of Figures 14 to 16 has an electrical impedance of 8 Ohms.

[0284] Referring to [Fig. 19], it can be seen that there is shown a partial vertical sectional view of the acoustic enclosure 1 shown in [Fig.7].

[0285] It can be seen that the cross-section of the acoustic transmission device 5 formed by the vertical internal separation walls 17 has a rectangular shape.

[0286] Since the structure of the acoustic transmission device 5 is created from rectangular surfaces (internal separation walls 17 constituting the duct of the acoustic transmission device 5), certain reinforcements must be incorporated into the design to avoid unexpected internal resonances.

[0287] An acoustic transmission device 5 for a complete frequency range may consist of 10 to 20 internal separation walls 17 which are almost all the same size and therefore all have the same internal resonance frequency. This can cause the acoustic enclosure 1 to vibrate and therefore strongly affect the frequency response.

[0288] To avoid this, a first solution is to add anti-resonance axes 18 passing through each internal separation wall 17, over the entire width of the acoustic enclosure 1. The diameter of the anti-resonance axes 18 must remain small so as not to have an impact on the section of the duct of the acoustic transmission device 5.

[0289] If we refer to [Fig.20], we can see that there is shown a partial vertical sectional view of the acoustic enclosure 1 according to a variant of the invention.

[0290] In this variant of the invention, the antiresonance axes are removed and replaced by a multiplication of the ducts placed in parallel. For example, instead of having a single duct of four meters, three horizontal separations can be created which will form four superimposed ducts of four meters with a section four times smaller than the initial duct. Given that the impedance of a duct is linked to its section, the sum of the four sections of the four ducts will give the same total section and therefore the same acoustic impedance. The thickness of the horizontal separations must remain small so as not to have too much impact on the sum of the sections.

[0291] This variant thus makes it possible to guarantee the absence of internal resonances which can seriously harm the quality of the sound reproduction. Unlike the anti-resonance axes 18, the solution by multiplying the sections ensures total cancellation of internal resonances. It is therefore a solution to be favored, especially when the acoustic enclosure 1 is subjected to high acoustic powers.

[0292] This variant thus has two advantages:

[0293] - it reduces the possibilities of resonance even more than the antiresonance axes 18 internal, and

[0294] - it allows the construction of the acoustic enclosure 1 per layer (construction by molding then assembly).

[0295] In [Fig.20], the acoustic enclosure 1 has four identical and stacked stages 31, and an upper closing cover 32, which makes it possible to create four superimposed ducts 33 having the same length and the same cross-section, the total section 34 of the four cross-sections of the four ducts 33 being equal to the cross-section of the duct of [Fig. 19], such that the cross-section of each duct 33 is equal to a quarter of the cross-section of the duct of [Fig.19],

[0296] In practice, the four stages 31 and the upper closing cover 32 are injection molded or manufactured by 3D printing, then the four stages 31 are superimposed and fixed together (for example, by gluing or screwing), then the upper closing cover 32 is fixed on the last stage 31 (for example, by gluing or screwing), the different elements being assembled to present an airtight seal, in particular by means of seals and / or directly by means of the glue. Advantageously, a polyurethane-based glue will be used.

[0297] It is understood that the particular embodiments which have just been described have been given for informational and non-limiting purposes, and that modifications may be made without departing from the present invention.

Claims

1. Claims Acoustic enclosure (1; 7; 12) comprising a box (2) in which at least one loudspeaker (3, 8) is mounted, said box (2) comprising, for each loudspeaker (3, 8), an opening (2a, 2b) closed by the front part of the associated loudspeaker (3, 8) and a vent (4, 10; 13) opening onto the outside, the acoustic enclosure (1; 7; 12) further comprising, inside the box (2) and for each loudspeaker (3, 8), an acoustic transmission device (5, 11; 14) extending between an inlet end (5a, 11a; 14a) configured to receive the sound waves emitted from the rear of the associated loudspeaker (3, 8) and an outlet end (5b, 11b; 14b) opening into the vent (4, 10; 13) associated, said acoustic transmission device (5, 11; 14) being configured to propagate the sound waves emitted from the rear of the associated loudspeaker (3, 8) towards the vent (4, 10;13) associated, characterized in that each acoustic transmission device (5,11; 14) has a characteristic length and a constant characteristic cross-section, said characteristic length and said characteristic cross-section being dimensioned such that:; the characteristic length Lolt of the acoustic transmission device (5, 11; 14) is defined according to the following equation: Ta--— ^LT “ 4*FC ' where c is the speed of sound in air, and Fc is the low cut-off frequency of the acoustic transmission device (5, 11; 14), i.e. the frequency Fc below which the frequencies are acoustically short-circuited; and the surface SuLT of the characteristic cross-section of the acoustic transmission device (5, 11; 14) is defined according to the following equation: _ PO *Vohp , k LT PrHr LoLr where PO is the atmospheric pressure, PrHP is the maximum pressure exerted on the air by the membrane of the associated loudspeaker (3, 8), VoHp is the maximum air volume displaced by the membrane of the associated loudspeaker (3, 8), and Lolt is the characteristic length of the acoustic transmission device (5, 11; 14).

2. Acoustic enclosure (1; 7; 12) according to claim 1, characterized in that the characteristic cross-section of the acoustic transmission device (5, 11; 14) is one of circular, oval, rectangular, and polygonal.

3. Acoustic enclosure (12) according to one of claims 1 and 2, characterized in that it comprises a plurality of identical and adjacent loudspeakers (3, 8), a common opening (2a) for the plurality of loudspeakers (3, 8), a common vent (13) for the plurality of loudspeakers (3, 8) and a common acoustic transmission device (14) for the plurality of loudspeakers (3, 8), said common acoustic transmission device (14) having a length corresponding to the characteristic length and a cross-section corresponding to the characteristic cross-section multiplied by the number of loudspeakers (3, 8).

4. Acoustic enclosure (1; 7; 12) according to one of claims 1 to 3, characterized in that each acoustic transmission device (5, 11; 14) comprises one of an acoustic transmission line arranged between its input end (5a, 11a; 14a) and its output end (5b, 11b; 14b), and several parallel acoustic transmission lines arranged between its input end (5a, 11a; 14a) and its output end (5b, 11b; 14b).

5. Acoustic enclosure (1; 7; 12) according to one of claims 1 to 4, characterized in that the acoustic enclosure (1; 7; 12) further comprises, for each acoustic transmission device (5, 11; 14), an anti-resonance device configured to attenuate the resonances of the structural elements of the acoustic enclosure (1; 7; 12).

6. Acoustic enclosure (1) according to one of claims 4 and 5, characterized in that it comprises a single acoustic transmission device (5), the acoustic enclosure (1) further comprising internal separation walls (17) arranged in parallel inside the box (2) to form a path between the rear of the at least one loudspeaker (3) and the vent (4), constituting a serpentine-shaped acoustic transmission line between the inlet end (5a) and the outlet end (5b) of the acoustic transmission device (5).

7. Acoustic enclosure (1) according to claim 6 in dependence on claim 5, characterized in that the acoustic transmission device (5) comprises a single acoustic transmission line consisting of a sealed conduit having the characteristic length and the characteristic cross-section, the acoustic enclosure (1) further comprising, as an anti-resonance device, a plurality of anti-resonance axes (18) arranged inside the box (2), each anti-resonance axis (18) passing through all of the parallel internal separation walls (17).

8. Acoustic enclosure (1; 7; 12) according to one of claims 1 to 4, characterized in that each acoustic transmission device (5, 11; 14) comprises a plurality of superimposed acoustic transmission lines, each acoustic transmission line consisting of a sealed conduit (33) having the characteristic length, the sum of the cross-sections of the plurality of conduits (33) corresponding to the characteristic cross-section of the acoustic transmission device (5, 11; 14).

9. An acoustic enclosure assembly (21; 22; 23; 24; 25; 26; 27; 28; 29) comprising a plurality of acoustic enclosures (1; 7; 12) according to one of claims 1 to 8, the loudspeakers (3, 8) of the plurality of acoustic enclosures (1; 7; 12) being electrically connected to each other in at least one of series and parallel.

10. Acoustic enclosure assembly (21; 22; 23; 24; 25; 26; 27; 28; 29) according to claim 9, characterized in that the plurality of acoustic enclosures (1; 7; 12) are distributed into a plurality of groups of acoustic enclosures (30), each group of acoustic enclosures (30) comprising an even number of acoustic enclosures (1; 7; 12) electrically connected in parallel, the groups of acoustic enclosures (30) being electrically connected in series, so that the electrical impedance of the acoustic enclosure assembly (21; 22; 23; 24; 25; 26; 27; 28; 29) is compatible with an audio amplifier.

Images