Loudspeaker adapted to attenuate an acoustic mode in a radially outer cavity relative to the moving part
The loudspeaker design addresses acoustic defects by using slots to connect a secondary cavity for air flow dissipation, enhancing sound quality and maintaining compactness without additional materials or complex adjustments.
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- DEVIALET
- Filing Date
- 2025-11-19
- Publication Date
- 2026-05-27
AI Technical Summary
Existing loudspeakers suffer from acoustic defects due to resonances in the cavity between the end cap and suspension system, which impair sound quality and are difficult to address without compromising enclosure compactness or requiring precise frequency matching.
A loudspeaker design featuring a main cavity with slots connecting to a secondary cavity, allowing air flow to dissipate resonance energy through viscous friction, eliminating the need for absorbent materials and maintaining compactness without precise frequency matching.
The design significantly reduces resonance intensity in the main cavity, improving acoustic quality while maintaining a competitive cost and compact form factor, without the need for additional materials or complex adjustments.
Smart Images
Figure IMGAF001_ABST
Abstract
Description
DOMAIN
[0001] The present invention relates to a loudspeaker, particularly intended for emitting sound in the midrange, the loudspeaker defining a central axis and comprising: a chassis, a moving assembly, a suspension system mechanically linking the moving assembly to the chassis, and a closing piece surrounding the membrane around the central axis, the moving assembly, the suspension system and the closing piece belonging to a loudspeaker assembly delimiting a cavity radially external to the moving assembly and extending axially at least forward of the suspension system, the diaphragm and the edge of the closing piece defining a passage from the cavity to a volume of air external to the loudspeaker.
[0002] The invention also relates to a sound enclosure comprising at least one such loudspeaker. EARLIER ART
[0003] The end cap serves both a structural and aesthetic purpose, particularly when it is continuous in shape with a visible portion of the membrane. However, this end cap creates a cavity between itself and the suspension system.
[0004] Unfortunately, a resonance can appear in the passage between the cavity thus created and the outside, which generates an acoustic defect that can impair the quality of the loudspeaker.
[0005] One theoretically possible solution is to place absorbent foam at the bottom of the cavity. However, the cavity is quite small, with a volume of, for example, a few cubic centimeters, making the use of foam impractical. Modeling has also shown that this solution is not very effective acoustically. Furthermore, the foam could come into contact with the moving parts and disrupt their movements.
[0006] Another solution would be to block the cavity's passage to the outside with a damping fabric. However, this fabric would disrupt the movements of the moving assembly and would be constantly and heavily stressed by these movements, making the solution difficult. Furthermore, modeling has shown that this solution would also not be very effective from an acoustic point of view.
[0007] Another known solution is to create a large cavity within the enclosure, physically separate from the loudspeaker and therefore from the cavity where the defect occurs. A Helmholtz resonance forms in this large cavity, and the resulting waves interfere with the problematic resonance, theoretically attenuating it. However, this solution compromises the compactness of the enclosure. Furthermore, it requires a fairly precise frequency match between the two resonances. This match necessitates a precise and repeatable adjustment of the dimensions of each cavity, which can lead to repeatability problems due to the dimensional variability of the components, particularly in a compact enclosure.
[0008] One aim of the invention is to provide a loudspeaker that overcomes all or part of the above disadvantages and offers improved acoustic quality at a competitive cost. SUMMARY OF THE INVENTION
[0009] For this purpose, the invention relates to a loudspeaker according to claim 1.
[0010] According to other advantageous aspects of the invention, the loudspeaker comprises one or more of the features corresponding to claims 2 to 8, taken individually or in all technically possible combinations.
[0011] The invention also relates to an acoustic enclosure according to claim 9, or advantageously claim 10.
[0012] According to a particular embodiment of the acoustic enclosure, the main cavity defines a main volume, the secondary cavity(ies), considered together, presenting a total volume between 10% and 30% of the main volume. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings, in which: there figure 1 is a schematic, front view of a soundproof enclosure according to the invention, the figure 2 is a schematic view of part of the acoustic enclosure shown on the figure 1 , in section along a radial plane with respect to a central axis of a tweeter and a midrange driver of the speaker enclosure, the section plane passing through one of the slots opening into a main cavity of the midrange driver, the figure 3 is a schematic view, in cross-section along the same plane and in perspective, showing a membrane, a chassis and the main cavity of the midrange speaker shown on the Figures 1 And 2, and showing a secondary cavity of the acoustic enclosure communicating with the main cavity, notably through the slit shown on the figure 2 Since internal speaker components are not shown in a way that better illustrates the shape of the chassis and diaphragm, the figure 4 is a view analogous to that of the figure 2 , but centered on the primary cavity and the secondary cavity represented on the figures 2 And 3 , and the figure 5 is a perspective view of part of a whole delimiting the main cavity shown on the figures 2 to 4 , this part partially delimiting the slits, one of which is visible on the figures 2 to 4 . DETAILED DESCRIPTION Acoustic enclosure
[0014] With reference to the figure 1 , an acoustic enclosure 10 is described according to the invention.
[0015] The acoustic enclosure 10 includes a loudspeaker 12 according to the invention, for example intended to emit sound in the midrange. In the example, the acoustic enclosure 10 also includes a loudspeaker 14 intended to emit sound in the treble range, or tweet in English, and advantageously two 16, 18 woofers, or woofers In English, for example, arranged back-to-back with respect to each other.
[0016] In the example, the acoustic enclosure 10 also includes an envelope 20, advantageously composed of a plurality of elements which extend between the loudspeakers 12, 16, 18. Among these elements, a closing piece 22, which will be described below, has been considered for reasons of clarity as part of the loudspeaker 12, but can also be considered as a piece of the envelope 20.
[0017] As seen on the figures 2 to 4, the acoustic enclosure 10 defines in the example a secondary cavity 24, an airflow F being intended to occur between a main cavity 26 of the loudspeaker 12 and the secondary cavity 24 via a plurality of slots 28.
[0018] According to an unrepresented variant, the acoustic enclosure 10 defines several secondary cavities (not shown, but can be deduced from the secondary cavity 24 in the presence of elements separating it into one or more cavities), the airflow F being established between the main cavity 26 and the secondary cavities via the slots 28.
[0019] The midrange speaker 12 surrounds and is, for example, coaxial with the tweeter 14, around a central axis X defined by the speaker 12.
[0020] In the example, the two bass speakers 16, 18 are back-to-back and coaxial along a Y axis orthogonal to the central X axis.
[0021] The term "designed to emit in the high range" means, for example, that the speaker 14 is adapted to reproduce high sound frequencies, i.e., treble sounds. Generally, the frequencies reproduced are above 2,000 Hz and can extend into the ultrasonic range, for example, at least between 2,000 Hz and 20 kHz, or even up to 40 kHz.
[0022] By "intended to emit in the midrange", we mean, for example, that the 12 speaker is adapted to reproduce sounds located in the mid-range of audible frequencies, that is, between bass and treble, generally in a frequency range between 200 Hz and 5.0 kHz.
[0023] By "bass speaker", we mean for example that the 16, 18 speakers are adapted to the reproduction of bass sounds, that is to say in the low area of audible frequencies, generally in a frequency range between 20 Hz and a few hundred Hz, for example 300 Hz.
[0024] Speakers 14, 16, and 18 are known in themselves and will not be described. Only speaker 12 will be described in detail below. Speaker
[0025] The loudspeaker 12 comprises a chassis 30, and a moving assembly 32 comprising a diaphragm 34 adapted to emit sound waves, the diaphragm being designed to vibrate relative to the chassis 30 along the central axis X and defining, relative to the chassis, a front side of the loudspeaker along the central axis X.
[0026] The loudspeaker 12 includes a suspension system 36 mechanically linking the moving assembly 32 to the chassis 30.
[0027] The loudspeaker 12 includes the closure piece 22 mentioned above, this closure piece surrounding the diaphragm 34 around the central axis X and having an edge 38 situated opposite the diaphragm 34 radially with respect to the central axis X.
[0028] The moving assembly 32, the suspension system 36 and the closing piece 22 belong to an assembly 40 ( figure 4 ) of the speaker 12 delimiting the main cavity 26.
[0029] The membrane 34 advantageously comprises a main portion 42 and an attachment portion 44 extending axially rearward from the main portion and to which the suspension system 36 is fixed. The membrane 34 is advantageously rigid, with a Young's modulus, for example, greater than 50 GPa. The membrane 34 is advantageously made of a metal with a mass content of at least 80%.
[0030] The main part 42 is for example spherical, and advantageously in continuity of form with an external surface 46 the closing piece 22 turned towards a volume of air 48 outside the acoustic enclosure 10.
[0031] The suspension system 36 includes a suspension joint 50, advantageously made of elastomeric material.
[0032] The suspension joint 50 advantageously presents, in section along a radial plane P, an "Ω" shape, the bulbous part of the "Ω" being for example turned towards the rear.
[0033] The suspension joint 50 includes a radially inner end 52 fixed on the attachment part 44 of the membrane 34, a radially outer end 54 fixed on an edge 56 of the frame 30, and a middle portion 58 connecting the ends 52, 54 and forming the bulbous part of the "Ω".
[0034] According to an unrepresented variant, the suspension system 36 is not fixed to the membrane 34, but to another part of the moving assembly 32, for example a spool holder 60. Cavities and fissures
[0035] The main cavity 26 extends around the central axis X. The main cavity 26 is radially external with respect to the moving assembly 32 and extends axially at least forward of the suspension system 36. In the example, the main cavity is even radially external with respect to the membrane.
[0036] The main cavity 26 advantageously has a volume between 10 and 15 cm³, for example about 12 cm³.
[0037] The membrane 34 and the edge 38 of the closure piece 22 define a passage 62 from the main cavity 26 to the air volume 48 outside the loudspeaker 12.
[0038] In the example, the assembly 40 consists of the membrane 34, the suspension system 36 and the closing piece 22. In other words, in the example, the membrane 34, the suspension system 36 and the closing piece 22 delimit the main cavity 26.
[0039] However, according to other embodiments (not shown), the main cavity 26 could be delimited by other elements, for example a spool holder fixed to the membrane 34, in particular if the suspension system 36 was fixed to this spool holder.
[0040] The set 40 defines the plurality of slits 28, which are distributed angularly around the central axis X, preferably regularly.
[0041] The assembly 40 defines surfaces 64 delimiting at least in part the slots 28, said surfaces having a roughness (parameter Ra) greater than 1.0 µm according to the ISO 04287 standard of 1997, according to which the roughness Ra is calculated by an arithmetic mean.
[0042] Passage 62 and slots 28 are advantageously the only inlets and outlets of the main cavity 26.
[0043] The slots 28 open into the main cavity 26 and respectively form conduits 66 adapted to allow, collectively, the flow of air F between the main cavity 26 and the secondary cavity 24.
[0044] Each of the slits 28 extends advantageously in a direction D1 orthogonal to the central axis X.
[0045] The number of slots 28 is for example at least ten, preferably at least fifteen.
[0046] Each of the 28 slots features: a length L1 between 5.0 mm and 15 mm in a first direction D1 orthogonal to the central axis X, for example 10 mm, a width L2 between 2.0 mm and 3.0 mm in a second direction D2 perpendicular to the first direction D1, for example 2.5 mm.
[0047] In the example, the slots 28 are partially defined by a part 68 of the assembly 40 extending axially between the closing piece 22 and the edge 56 of the frame 30.
[0048] According to an unrepresented variant, the slots 28 are for example defined by the closing piece 22.
[0049] Each of the conduits 66, for example, has a radial component, and is preferably oriented radially.
[0050] Part 68 of the assembly 40 advantageously forms a ring 70 around the central axis X, the ring forming a plurality of studs 74 and notches 76.
[0051] Part 68 advantageously comprises an elastomeric material ensuring a certain roughness, and is preferably made of the same material as the suspension system 36. In other words, the suspension system 36 and part 68 partially delimiting the slots 28 are one and the same piece.
[0052] The studs 74 alternate with the notches 76 around the central axis X and are located for example against the closing piece 22. In other words, the slots 28 are formed by the part 68 and the closing piece 22.
[0053] Alternatively or in addition, all or part of the studs 74 are located against the edge 56 of the chassis 30. In other words, at least some of the slots 28 are formed by the part 68 and the edge 56 of the chassis.
[0054] The secondary cavity 24 extends from orifices 78 defined by the conduits 66.
[0055] In the example, the secondary cavity 24 is located axially under the closing piece 22. The secondary cavity 24 is for example delimited by the closing piece 22 and by one or more internal elements 80 of the acoustic enclosure 10, and advantageously by a part of the chassis 30.
[0056] The secondary cavity 24 advantageously has a total volume between 10% and 30% of the volume of the main cavity 26, for example, approximately 20% of the volume of the main cavity. This total volume is advantageously between 1.5 and 3.0 cm³ and is, for example, approximately 2.5 cm³.
[0057] The secondary cavity24 is for example closed, in the sense that its only inlets and outlets are the orifices 78 defined by the conduits 66. Functioning
[0058] The slots 28 allow air to flow F between the main cavity 26 and the secondary cavity 24.
[0059] The air flow F is advantageously "pulsed", or alternating (in one direction then the other), that is to say, it occurs alternately towards the main cavity 26 and towards the secondary cavity 24 in the ducts 66. The air flow F (in fact the velocity of the air at a given point of the flow) is for example sinusoidal.
[0060] During this flow, the kinetic energy of the acoustic waves is dissipated by viscous friction on the surfaces (walls) delimiting the slits 28, in particular the surfaces 64.
[0061] This mechanism allows for a substantial dissipation of the energy of the resonance mode in the main cavity 26, which helps to mitigate the detrimental consequences on the quality of the acoustic enclosure 10.
[0062] This solution differs from known solutions in particular in that the secondary cavity 24 is not a fluidically separate cavity used to generate a Helmholtz resonance that would interfere with the resonance of the main cavity 26. On the contrary, the secondary cavity 24 communicates fluidly with the main cavity 26 via the slots 28 to allow the air flow F creating an energy dissipation at the slots which greatly reduces the intensity of the resonance in the main cavity. Benefits
[0063] Thanks to the above features, the 12 speaker offers improved acoustic quality and remains competitively priced.
[0064] Indeed, the slots 28 allow for a very significant reduction in resonance within the main cavity 26 in a simple manner, without the need for absorbent foams or fabric. This is particularly true when the loudspeaker 14 is present, for example, emitting in the treble range at frequencies likely to activate resonance in the main cavity 26 of the loudspeaker 12, which emits, for example, in the midrange range.
[0065] The secondary cavity 24 can remain of a modest volume compared to the main cavity 26, which preserves the compactness of the acoustic enclosure 10.
[0066] Furthermore, no precise frequency matching is required between cavities 24, 26, which avoids repeatability problems.
Claims
1. Loudspeaker (12), particularly intended for emitting sound in the midrange, the loudspeaker (12) defining a central axis (X) and comprising: - a chassis (30), - a moving assembly (32) comprising a diaphragm (34) adapted to emit sound waves, the diaphragm (34) being designed to vibrate relative to the chassis (30) along the central axis (X) and defining, relative to the chassis (30), a front side of the loudspeaker (12) along the central axis (X), - a suspension system (36) mechanically connecting the moving assembly (32) to the chassis (30), and - a closing piece (22) surrounding the diaphragm (34) around the central axis (X) and having an edge (38) situated radially opposite the diaphragm (34) with respect to the central axis (X), the moving assembly (32), the suspension system (36), and the closing piece (22) belonging to a set (40) of the loudspeaker (12) delimiting a main cavity (26) extending around the central axis (X),the main cavity (26) being radially external to the moving assembly (32) and extending axially at least forward of the suspension system (36), the diaphragm (34) and the edge (38) of the closing piece (22) defining a passage (62) from the main cavity (26) to an air volume (48) external to the loudspeaker (12), , characterized in that said assembly (40) defines a plurality of slots (28) distributed around the central axis (X), preferably regularly, the slots (28) opening into the main cavity (26) and forming respectively conduits (66) adapted to allow, collectively, an airflow (F) intended to be established between the main cavity (26) and one or more secondary cavity(ies) (24) delimited by an acoustic enclosure (10) integrating the loudspeaker (12).
2. Loudspeaker (12) according to claim 1, wherein said assembly (40) defines surfaces (64) delimiting at least in part the slots (28), said surfaces (64) having a roughness greater than 1.0 µm.
3. Loudspeaker (12) according to claim 1 or 2, in which each of the slots (28) extends in a direction (D1) orthogonal to the central axis (X), 4. Loudspeaker (12) according to any one of claims 1 to 3, wherein each of the conduits (66) has a radial component, and is preferably radially oriented.
5. Loudspeaker (12) according to any one of claims 1 to 4, wherein said plurality of slots (28) comprises at least ten slots, each of the slots (28) having: - a length (L1) between 5.0 mm and 15 mm in a first direction (D1) orthogonal to the central axis (X); and / or - a width (L2) between 2.0 mm and 3.0 mm in a second direction (D2) perpendicular to the first direction (D1).
6. Loudspeaker (12) according to any one of claims 1 to 5, wherein the slots (28) are at least partially defined by a part (68) of the assembly (40) extending axially between the closing piece (22) and an edge (56) of the chassis (30).
7. Loudspeaker (12) according to claim 6, wherein said part (68) of the assembly (40) forms a ring (70) around the central axis (X), the ring (70) forming a plurality of studs (74) and notches (76), the studs (74) alternating with the notches (76) around the central axis (X) and situated against the closing piece (22) and / or the edge (56) of the chassis (30).
8. Loudspeaker (12) according to claim 6 or 7, wherein the part (68) comprises an elastomeric material and is preferably made of material with the suspension system (36).
9. Acoustic enclosure (10) comprising at least one loudspeaker (12) any one of claims 1 to 8, the acoustic enclosure (10) defining at least in part one or more secondary cavity(ies) (24) extending from orifices (78) defined by the ducts (66), the ducts (66) being adapted to permit, collectively, said airflow (F) between the main cavity (26) and the secondary cavity(ies) (24).
10. Acoustic enclosure (10) according to claim 9, in which the main cavity (26) defines a main volume, the secondary cavity(ies) (24), considered together, having a total volume between 10% and 30% of the main volume.