Electrodynamic loudspeaker

Abstract

The invention relates to an electrodynamic loudspeaker (10) comprising a device (22) for suspending a diaphragm (20) and a coil (18), which device can be translated along a longitudinal axis (Z) and which comprises: - a peripheral suspension (44) extending radially relative to the longitudinal axis (Z) between a proximal edge (50) and a distal edge (52) linked to an outer frame (12) of the loudspeaker; - an intermediate connection device (46) between the outer frame (12) and the diaphragm (20) along the longitudinal axis (Z), and extending along said axis between a lower base (54) to which is attached the proximal edge (50), and an upper base (56), and radially relative to said axis, between an inner circumference (58) rigidly connected to the coil (18), and an outer circumference (60) rigidly connected to the diaphragm (20); and - an inner suspension (48) extending radially relative to the longitudinal axis (Z) between a proximal contour (72) attached to an inner frame (74) rigidly connected to the outer frame (12), and a distal contour (70) attached to the upper base (56).

Description

[0001] DESCRIPTION

[0002] TITLE: Electrodynamic Loudspeaker

[0003] The present invention relates to an electrodynamic loudspeaker, and more particularly to an electrodynamic loudspeaker of the "woofer" type, that is to say configured to emit low frequency sounds.

[0004] An electrodynamic loudspeaker comprises a vibrating element relative to a magnet and configured to be operated in piston mode, i.e., vibrating in translation along a longitudinal axis.

[0005] The design of the various elements of an electrodynamic loudspeaker is complex because it must take into account various and often contradictory constraints, including spatial, sonic and, in some cases, aesthetic constraints.

[0006] With regard to the spatial aspect, the size of the speaker must most often be controlled, whether the speaker is used alone in free placement or after integration into another device, for example in a soundproof enclosure or in a vehicle.

[0007] A loudspeaker must also meet a set of specifications, which can vary in stringency, regarding sound quality and sound pressure level (SPL). In particular, it is desirable to minimize sound distortion within the loudspeaker's frequency response.

[0008] Rotational vibration modes (in English, "rocking mode") of the vibrating element are notably responsible for such distortions and a loss of acoustic efficiency.

[0009] These rotational vibration modes are particularly troublesome in the field of low-frequency loudspeakers, due to the length of the stroke of the vibrating element along the direction of the piston mode, which is particularly large in this case.

[0010] Document DK 178810 describes a low-profile loudspeaker in which the impact of rotational vibration modes is reduced. This loudspeaker incorporates a double "spider" suspension, meaning one formed from a corrugated material. The double suspension is positioned beneath the diaphragm and is attached at one end to the diaphragm and at the other to a top plate located above the magnet. In such a loudspeaker, it is very difficult to control rocking, that is, the rotational movements of the loudspeaker's moving parts that occur during operation due to asymmetries in the shape of the various moving parts during production and / or the air gap in which the voice coil oscillates, and / or asymmetries created during the assembly of these different components.

[0011] These tilting movements can lead to impacts between the moving and fixed parts of the speaker, which impair the quality of the sound emitted and cause premature wear of the speaker.

[0012] Furthermore, this speaker does not fully satisfy in terms of sound distortion or compactness.

[0013] One aim of the invention is therefore to offer a loudspeaker for which the risk of tipping is reduced, preferably more compact, particularly in the direction of the piston mode, and / or allowing a quality sound reproduction, in particular with reduced total harmonic distortion (THD), especially in the low frequencies, the loudspeaker being if possible easy to produce industrially.

[0014] To this end, the invention relates to an electrodynamic loudspeaker comprising: a) an external chassis, b) a motor having a base mechanically fixed to the external chassis, and a voice coil moving in translation about a longitudinal axis relative to the external chassis, the voice coil comprising a winding, c) a diaphragm, and d) a suspension device for the diaphragm and the voice coil, characterized in that the suspension device comprises: i) a peripheral suspension extending radially about the longitudinal axis between a proximal edge and a distal edge, the distal edge being connected to the external chassis; ii) an intermediate linking device, placed between the external chassis and the diaphragm along the longitudinal axis, the intermediate linking device extending:

[0015] - along the longitudinal axis, between a lower base to which the proximal edge of the peripheral suspension is fixed and an upper base, and

[0016] - radially relative to the longitudinal axis, between an inner circumference, mechanically attached to the coil, and an outer circumference, mechanically attached to the diaphragm; and iii) an internal suspension, which extends radially relative to the longitudinal axis between a proximal contour, fixed on an inner chassis of the loudspeaker mechanically attached to the outer chassis, and a distal contour fixed on the upper base of the intermediate linking device.

[0017] The intermediate linking device forms a mechanical intermediate suspended by means of the peripheral and internal suspension, and connected on one side to the membrane and on the other side to the moving assembly comprising the excitation coil.

[0018] The choice of mass distribution of the intermediate link device makes it possible to control and improve the sensitivity of the loudspeaker in the low frequencies, while ensuring good stability of the moving assembly during large excursions.

[0019] In particular, the design of the intermediate linking device in terms of shape and / or mass distribution, advantageously in synergy with the choice of stiffnesses and / or positions of the peripheral and internal suspensions, allows fine adjustment of the position of the center of tilt of the moving assembly formed by the moving crew, the diaphragm and the suspension device, so that this center of tilt is as close as possible to the center of gravity of this moving assembly taking into account possible asymmetries related to the shape and / or assembly of the moving crew and / or the air gap in which the coil is intended to oscillate.

[0020] Such asymmetries do indeed increase the speaker's sensitivity to tilting.

[0021] The positioning of the intermediate linking device between the peripheral and internal suspensions along the longitudinal axis simultaneously allows control of the speaker's footprint along this axis, or even a reduction of this footprint by using the volume located inside the diaphragm, particularly important in the case where this diaphragm is concave, while maximizing the stability of the rotating moving assembly during large excursions.

[0022] The mechanical intermediary also ensures that neither the diaphragm nor the moving parts, and in particular the voice coil, are directly connected simultaneously to the peripheral and internal suspensions. Thanks to this intermediate linkage, the mass distribution on the diaphragm is thus reduced compared to prior art loudspeakers, and the stiffness of the suspension system is particularly well controlled.

[0023] According to other advantageous aspects of the invention, the loudspeaker comprises one or more of the following features, taken individually or in any technically possible combination:

[0024] - The intermediate link device is configured so that a distance (RG) between:

[0025] * a center of gravity (G) of a moving assembly comprising the coil, the diaphragm, and the suspension device, defined in an equilibrium position of the moving assembly relative to the external chassis, and * a tilting center (R) about which a moving subgroup of the moving assembly, said moving subgroup comprising the coil, the diaphragm, and the intermediate linking device, exhibits a rigid-body mode of rotation, satisfies the relation RG < y kAGA +k B GB d ans which RG designates the distance between the

[0026] 'k B GB-k A GA ° center of gravity (G) and the center of tipping (R), y denotes a predetermined coefficient, A and kA denote an attachment point on the moving assembly and a stiffness constant of a first ideal spring modeling a connection provided by the peripheral suspension between the moving assembly and the external chassis, and B and k Bdesignate an attachment point on the moving assembly and a stiffness constant of a second ideal spring modeling a connection ensured by the internal suspension between the moving assembly and the internal chassis;

[0027] - the predetermined coefficient is less than or equal to 0.100;

[0028] - the intermediate linking device is formed in a more rigid material than the peripheral and internal suspensions;

[0029] - the intermediate linking device comprises a lattice structure, the inner circumference and the outer circumference each being formed on a respective beam of the lattice, said beams being linked by a plurality of crossbeams;

[0030] - the lattice is formed from a material such that the ratio of the Young's modulus of this material to the density of this material is greater than or equal to 1.9 x 10 9 Pa.kg' 1 .m 3 ;

[0031] - the internal suspension is not directly connected to the membrane;

[0032] - the speaker includes a single internal suspension;

[0033] - the coil winding extends along the longitudinal axis over a length less than that of an air gap of a motor magnet attached to the base;

[0034] - the internal suspension comprises a surface extending radially relative to the longitudinal axis and undulating along the longitudinal axis, the characteristic amplitude of the undulations along the longitudinal axis and / or the characteristic length of the undulations radially relative to the longitudinal axis decreasing from the proximal contour to the distal contour;

[0035] - the height of the speaker along the longitudinal axis is less than 100 mm;

[0036] - The speaker is configured to emit sounds with a frequency between 20 Hz and 2,000 Hz.

[0037] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which: - Figure 1 is a cross-sectional view of an electrodynamic loudspeaker according to the invention in a plane containing the longitudinal axis; and

[0038] - Figure 2 is an enlarged view of part of the loudspeaker shown in Figure 1; and

[0039] - Figure 3 is a schematic representation of the moving group of the loudspeaker in Figure 1 in the main tilting mode and models of the mechanical actions exerted on this moving group.

[0040] With reference to figures 1 and 2, an electrodynamic loudspeaker 10 according to the invention is described.

[0041] Speaker 10, for example, is a speaker configured to emit sounds in the low frequency range, also referred to by the English term "woofer".

[0042] In particular, speaker 10 can be configured to emit sounds with frequencies between 20 Hz and 2000 Hz

[0043] The loudspeaker 10 comprises an external chassis 12, a motor 14 comprising a base 16 mechanically attached to the external chassis 12 and a coil 18, movable in translation along a longitudinal axis Z relative to the external chassis 12 and comprising a winding 19, a diaphragm 20 and a suspension device 22 for the diaphragm 20 and the coil 18.

[0044] The diaphragm 20, the suspension device 22 and the coil 18 together form a moving assembly 23 of the loudspeaker 10, the moving assembly 23 being movable relative to the external chassis 12.

[0045] The center of gravity of the mobile crew 23 is designated in the following by point G, visible in figure 1 and, in a very schematic case, in figure 3.

[0046] The center of rotation of a mobile subgroup 23A of the moving assembly 23 comprising the membrane 20, the coil 18 and a portion of the suspension device 22 linking the membrane 20 and the coil 18 which will be described later is called the center of tilt R, this mobile subgroup 23A being assimilated to a rigid body in its dominant mode of rotation, the rotation then taking place around an axis of rotation A orthogonal to the longitudinal axis Z passing through the center of tilt R, as can be seen in a very schematic way in Figure 3.

[0047] It is therefore understood that the mobile subgroup 23A behaves, depending on the excitation conditions, as a rigid or deformable solid.

[0048] As shown in Figure 1, the longitudinal axis Z is advantageously an axis with respect to which the loudspeaker 10 has approximately rotational symmetry.

[0049] The external chassis 12 is also known as the "salad bowl". The external chassis 12 comprises a base 24 and a circumferential wall 26 extending from the base 24 towards the front of the speaker 10.

[0050] In this description, the expressions "front", "in front", "rear", "behind" are to be understood in reference to the main direction of propagation of the sounds emitted by the loudspeaker along the longitudinal axis Z.

[0051] The circumferential wall 26 in the example has a truncated conical shape with axis the longitudinal axis Z, flared towards the front of the loudspeaker 10.

[0052] Advantageously, the circumferential wall 26 is formed by a plurality of radial pillars 28 extending between the bottom 24 of the external frame 12 and an external peripheral edge 30 of the circumferential wall 26.

[0053] The external chassis 12 extends around the engine 14, in particular the base 16 of the engine 14 to which it is mechanically attached.

[0054] In the embodiment of the invention shown in the figures, the base 16 of the motor 20 includes a cylinder head 32 on which a magnet 34 is placed.

[0055] The cylinder head 32 defines at least one air gap 36.

[0056] Advantageously, the base 16 of the engine 14 further includes an annular support 38 centered on the longitudinal axis Z and arranged in an internal space delimited by the cylinder head 32, the annular support 38 then delimiting the air gap 36 with the cylinder head 32.

[0057] Advantageously, the magnet 34 has an annular shape and is arranged along the longitudinal axis Z in front of the breech 32, in particular between the breech 32 and the annular support 38.

[0058] The coil 18 is intended to oscillate relative to the magnet 34 when the motor 14 receives electrical energy, around an equilibrium position shown in Figure 1.

[0059] The coil 18 includes a coil holder 40, on an outer surface of which the winding 19 is formed.

[0060] The spool holder 40 is, for example, cylindrical with axis the longitudinal axis Z.

[0061] Winding 19 is arranged in air gap 36.

[0062] Preferably, the winding 19 extends along the longitudinal axis Z over a length less than that of the air gap 36. This arrangement makes it possible to produce a motor described by the English term "underhung", in which the risks of rotation of the coil 18, in addition to the desired piston movement, are reduced.

[0063] The oscillations of the coil 18 and in particular of the winding 19, allow the reproduction of sounds by the loudspeaker 10, through oscillations of the diaphragm 20.

[0064] The membrane 20 defines an acoustic radiation surface of the loudspeaker 10. Advantageously, the membrane 20 has a convexity oriented towards the front of the loudspeaker 10.

[0065] In particular, membrane 20 has a spherical cap or dome shape.

[0066] Membrane 20 has a peripheral edge 20a.

[0067] The peripheral edge 20a has in the example a substantially annular shape centered on the longitudinal axis Z.

[0068] To allow oscillations of the membrane 20 along the longitudinal axis Z, the membrane 20 is suspended by means of the suspension device 22.

[0069] The suspension device 22 includes a peripheral suspension 44, an intermediate linking device 46, and an internal suspension 48.

[0070] The peripheral suspension 44 extends radially relative to the longitudinal axis Z between a proximal edge 50 and a distal edge 52.

[0071] The peripheral suspension 44 extends around the longitudinal axis Z.

[0072] In the example, the peripheral suspension 44 has, in section along a plane passing through the longitudinal axis Z, a Q shape, the convexity of the Q being turned axially towards the rear of the loudspeaker 10.

[0073] The peripheral suspension 44 is preferably airtight.

[0074] The peripheral suspension 44 is formed in an elastic material such as an elastomeric material. The elastomeric material is, for example, chosen from a butadiene-acrylonitrile copolymer (in English, "nitrile butadiene rubber", abbreviated NBR) and a styrene-butadiene copolymer (in English, "styrene butadiene rubber", abbreviated SBR).

[0075] The distal edge 52 of the peripheral suspension 44 is linked to the external frame 12, preferably near or on the external peripheral edge 30 of the circumferential wall 26.

[0076] The proximal edge 50 is linked to the intermediate linking device 46.

[0077] The intermediate linking device 46 is placed along the longitudinal axis Z between the external frame 12 and the membrane 20.

[0078] The intermediate linking device 46 is thus positioned along the longitudinal axis Z in front of the base 24 of the external frame 12 and behind at least a central portion of the membrane 20 extending from the longitudinal axis Z.

[0079] The intermediate link device 46 forms the portion of the suspension device 22 included in the mobile subgroup 23A of the mobile crew 23 mentioned above.

[0080] The moving subgroup 23A of the moving assembly therefore includes the coil 18, the intermediate linking device 46 and the diaphragm 20. The intermediate linking device 46 is thus intended in particular to form with the diaphragm 20 and the coil 18 an assembly having in certain cases of excitation a rigid body displacement, in particular in the dominant rotation mode of the moving subgroup 23A.

[0081] The intermediate linking device 46 is also intended to form an intermediate link between the peripheral suspension 44 and internal suspension 48.

[0082] To this end, the intermediate linking device 46 is formed in a material more rigid than the materials in which the peripheral suspensions 44 and internal suspensions 48 are formed.

[0083] The intermediate connecting device 46 is for example formed in a rigid plastic material, such as acrylonitrile butadiene styrene (abbreviated ABS), or a metal, or even in carbon fiber.

[0084] The intermediate linking device 46 can be a single unit.

[0085] The intermediate connecting device 46 can in particular be obtained by molding.

[0086] The intermediate linking device 46 extends along the longitudinal axis Z between a lower base 54, on which is fixed the proximal edge 50 of the peripheral suspension 44, and an upper base 56.

[0087] The lower base 54 is for example glued to the proximal edge 50, in particular in front of the proximal edge 50 along the longitudinal axis Z.

[0088] The upper base 56 is linked to the internal suspension 48, as will be described later.

[0089] The intermediate linking device 46 extends radially relative to the longitudinal axis Z between an inner circumference 58, mechanically attached to the coil 18 and an outer circumference 60, mechanically attached to the membrane 20.

[0090] The internal circumference 58 is positioned between the lower base 54 and the upper base 56 along the longitudinal direction Z.

[0091] In the example, the internal circumference 58 includes a receiving groove 62 in which one end of the spool holder 40 of the spool 18 is received.

[0092] The receiving groove 52 is, for example, glued to the spool holder 40.

[0093] Preferably, the inner circumference 58 is in front of the outer circumference 60 along the longitudinal direction Z.

[0094] The external circumference 60 is preferably between the lower base 54 and the upper base 56 along the longitudinal direction Z.

[0095] In the example, the outer circumference 60 has a receiving wall 60a to which the peripheral edge 20a of the membrane 20 is directly fixed, for example, glued. In a particular embodiment, shown in Figures 1 and 2, the intermediate connecting device 46 comprises a lattice structure.

[0096] The truss structure comprises a plurality of beams 64 extending around the longitudinal axis Z, linked by a plurality of crossbeams 66 extending radially relative to the longitudinal axis Z.

[0097] The internal circumference 58 and the external circumference 60 are in this case each formed on a respective beam 64.

[0098] The cross members 66 are preferably equally distributed around the longitudinal axis Z.

[0099] The implementation of a lattice structure makes it possible to control the stiffness of the mobile subgroup 23A comprising the coil 18, the diaphragm 20 and the intermediate linking device 46 and the mass distribution of this mobile subgroup 23A of the moving assembly 23, so as to control its possible tilting, without excessively weighing down the loudspeaker 10. The energy consumption of the loudspeaker 10 is therefore controlled.

[0100] The lattice structure is, for example, formed from a material with a Young's modulus measured according to ISO 6721-1 published in April 2019 and a density such that the ratio of the Young's modulus to the density of the material is greater than or equal to 1.9 GPa.kg' 1 .m 3 .

[0101] The truss structure optionally includes one or more connecting elements 68 extending radially from at least one beam 64.

[0102] The connection elements 68 are configured to compensate for any potential imbalance of the mobile crew 23, particularly the mobile subgroup 23A, in the absence of these connection elements 68.

[0103] The internal suspension device 48 extends radially relative to the longitudinal axis Z between a distal contour 70 fixed on the upper base 56 of the intermediate linking device 22 and a proximal contour 72 fixed on an internal chassis 74 of the loudspeaker mechanically attached to the external chassis 12.

[0104] The internal suspension device 48 is commonly known by the English name "spider".

[0105] The internal suspension device 48 is formed from a more flexible material than the intermediate connecting device 46.

[0106] For example, the internal suspension device 48 is formed from a resin-filled woven mesh material.

[0107] In particular, the woven mesh may include fibers selected from cotton fibers, polyester fibers, meta-aramid fibers and their blends.

[0108] The resin is, for example, a thermosetting resin, in particular a phenolic resin. The internal suspension device 48 extends around the longitudinal axis Z.

[0109] In a particular embodiment, shown in the figures, the internal suspension device 48 comprises a surface extending radially relative to the longitudinal axis Z and corrugated along the longitudinal axis Z.

[0110] In a particular embodiment, an amplitude H characteristic of the undulations along the longitudinal axis Z and / or a length L characteristic of the undulations radially relative to the longitudinal axis Z decrease from the proximal contour 72 to the distal contour 70, as shown in Figure 2.

[0111] The internal suspension 48 thus forms a surface exhibiting corrugations of decreasing radii.

[0112] This arrangement increases the stiffness of the internal suspension 48 radially relative to the longitudinal direction, without significantly increasing its stiffness along the longitudinal direction. Thus, the amplitude of the radial displacement of the voice coil 18 is reduced without affecting its ability to oscillate along the longitudinal direction of interest for sound reproduction. This arrangement further reduces the risk of tipping around the tipping center R within the bandwidth of the loudspeaker 10, particularly during large excursions of the voice coil 18 along the longitudinal axis Z relative to its equilibrium position, as will be explained at the end of this description.

[0113] Preferably, as shown in the figures, the internal suspension 48 is not directly linked to the membrane 20.

[0114] Preferably, as shown in the figures, the loudspeaker 10 comprises a single internal suspension 48.

[0115] The distal contour 70 of the internal suspension 48 is fixed to the upper base 56 of the intermediate linking device 46. For example, it is glued to the upper base 56, in front of it along the longitudinal axis Z.

[0116] The proximal contour 72 is fixed to the internal frame 74.

[0117] The internal chassis 74 is mechanically attached to the external chassis 12, in front of the external chassis 12 along the longitudinal axis Z.

[0118] The internal chassis 74 includes an external peripheral edge 76 extending around the longitudinal axis Z.

[0119] The outer peripheral edge 76 extends for example in a plane perpendicular to the longitudinal axis Z, for example in which also extends the upper base 56 of the intermediate connecting device 46.

[0120] The outer peripheral edge 76 extends radially less far from the longitudinal axis Z than the circumferential wall 26 of the fixed frame 12. The proximal contour 72 is for example fixed on the outer peripheral edge 76, in particular glued to the outer peripheral edge 76, in front of it in the longitudinal direction.

[0121] Advantageously, the internal frame 74 extends radially less far from the longitudinal axis Z than the internal circumference 58 of the intermediate linking device 46, through this internal circumference 58 along the longitudinal axis Z.

[0122] Advantageously, the internal chassis 74 further includes an internal peripheral edge 78.

[0123] The inner peripheral edge 78 extends in particular in a plane perpendicular to the longitudinal axis Z, for example in which also extends the lower base 54 of the intermediate connecting device 46.

[0124] The internal peripheral edge 78 and external peripheral edge 76 are then connected by an internal circumferential wall 80.

[0125] The internal circumferential wall 80 includes, for example, a plurality of radial pillars 82 connecting the external peripheral edge 76 and the internal peripheral edge 78.

[0126] The radial pillars 82 are advantageously equidistributed angularly around the longitudinal axis Z.

[0127] The internal circumferential wall 80 has in the example shown in the figures a truncated conical shape with axis the longitudinal axis Z and flared towards the front of the loudspeaker 10. The internal chassis 74 thus forms an internal “basket”.

[0128] The internal chassis 74 is in the example mechanically attached to the annular support 38 and in front of the annular support 38 along the longitudinal axis Z.

[0129] The choice of the shape and mass distribution of the intermediate linking device 46 allows fine control of the position of the center of gravity G of the moving assembly 23 and of the tilting center R of the moving subgroup 23A of the moving assembly 23 formed by the coil 18, the intermediate linking device 46 and the diaphragm 20.

[0130] The centers of gravity G and tilting R can be visualized in Figure 1 when the moving assembly 23 is in equilibrium relative to the external frame 12, and in Figure 3 in a particular position during a particular tilting movement of the moving subgroup 23A of the moving assembly 23.

[0131] The absolute and relative positions of the centers of gravity G and tilting R vary according to the overall movement of the moving assembly 23 and / or the relative movements of the diaphragm 20, the suspension device 22 and / or the coil 18 which make up the moving assembly 23. As a first intention, it is important to limit the amplitude of the tilting movement of the moving subgroup 23A of the moving assembly 23 in the dominant mode of rotation.

[0132] An excessively large tilt in this dominant rotation mode can indeed lead to mechanical contacts that are detrimental to the operation and lifespan of the loudspeaker 10 and to the quality of the sound emitted.

[0133] This is all the more problematic for low-frequency speakers, for which the frequency of the dominant rotation mode, referred to hereafter as the fundamental switching frequency f0, is often included within a bandwidth of the speaker 10,

[0134] To mathematically describe the tilting motion of the moving subgroup 23A of the moving assembly 23 in the dominant rotation mode, the moving assembly 23 can, as a first approximation, be considered as a solid of mass m, with center of gravity G, the 23A subgroup of the moving assembly 23 formed by the coil 18, the intermediate linking device 46 and the diaphragm 20 having a single degree of freedom in rotation around the axis of rotation A orthogonal to the longitudinal direction Z and passing through the center of tilting R, this axis being considered as fixed as a first approximation relative to the external chassis 12.

[0135] The position of the mobile subgroup 23A is located by the oriented angle 0 formed between the longitudinal direction Z and the line RG, visible in figure 3.

[0136] The connections between the external chassis 12 and the internal chassis 74 and the moving assembly 23 via the peripheral suspension 44 and internal suspension 48 are respectively modeled by:

[0137] - a first ideal spring 84, without mass, linked at a point A to the moving assembly 23 visible in figures 1 to 3 and with a spring constant kA, and

[0138] - a second ideal spring 86, without mass, linked at a point B to the moving assembly 23 visible in figures 1 and 3 and of stiffness constant ks.

[0139] The total effort generated by the possible imbalances of forces, stiffness and mass due in particular to imperfections in the manufacture of the different elements of the moving assembly 23, is modeled by a force couple of moment C about the axis of rotation A, as seen in Figure 3.

[0140] Applying the fundamental laws of dynamics to the moving assembly 23 in a frame of reference attached to the external chassis 12 shows that:

[0141] - the distance RG between the center of tipping R and the center of gravity G is increased by a maximum distance RG ma x, for rotational oscillations of small angular amplitude, the following equation 1:

[0142] - amplitude 0 ma x of these oscillations satisfies the following equation 2, in which IG denotes a moment of inertia of the moving assembly 23 with respect to an axis passing through the center of gravity G and parallel to the axis of rotation A:

[0143] It is therefore understandable that the choice of the mass m of the moving assembly 23, the distribution of this mass m in space (and in particular the position of the center of gravity G), as well as the choice of the stiffnesses and positions of the peripheral suspension 44 and internal suspension 48 modeled by the first and second springs 84, 86 with stiffness constants kA and k B allows control of the RG distance in all possible movements of the mobile crew 23 as well as the amplitude 0 ma x oscillations during the tilting of the mobile subgroup 23A of the mobile crew 23.

[0144] Consequently, the intermediate linking device 46, which allows action on all these factors influencing the dominant mode of rotation, makes it possible to precisely limit the distance RG in all possible movements of the moving assembly 23 and the amplitude 0 ma x of the tilting oscillations of the mobile subgroup 23A during the operation of the loudspeaker 10.

[0145] In particular, to minimize the amplitude 0 ma Given the tilting oscillations, it is desirable to maximize the denominator of the last term of equation 2. For example, it is possible to configure the intermediate linking device 46 so that: k A GA 2 + k B GB 2 » RG. k B GB - k A GA) (3) or equivalently so that:

[0146] K to this end, it is possible to choose a predetermined coefficient y and to configure the intermediate link device 46 so that the mobile crew 23 satisfies equation 5:

[0147] K, for example, the predetermined coefficient y may be chosen to be less than or equal to 0.100, or even less than or equal to 0.050, preferably less than or equal to 0.010.

[0148] It should be noted that the positions of the attachment points A and B of the first and second springs 84, 86 model the connections between the external frame 12 and the internal frame 74 and the moving assembly 23, the stiffness constants kA and k B corresponding, as well as the positions of the center of gravity G and the center of tilt R can be determined by finite element simulation, and / or verified experimentally, once the loudspeaker 10 is assembled.

[0149] Preferably, the intermediate linkage device 46 is configured so that the tilting center R is located on the longitudinal axis Z, as is the center of gravity G, when the moving assembly 23 is in equilibrium relative to the external chassis 12, as shown in Figure 1.

[0150] Preferably, the center of gravity G and the center of tilt R coincide when the moving assembly 23 is in equilibrium relative to the external chassis 12. In a particular embodiment, the distance RG is less than or equal to 0.5 mm, advantageously less than 0.4 mm, or even less than 0.3 mm or 0.2 mm.

[0151] Thanks to the invention described above, the risk of rocking (tilting with mechanical contact) is very low, and simultaneously a reduction in harmonic distortion rate of 4 to 9 dB, with a height gain of 24% along the longitudinal axis Z, were obtained.

Claims

DEMANDS 1. Electrodynamic loudspeaker (10) comprising: a) an external chassis (12), b) a motor (14) having a base (16) mechanically fixed to the external chassis (12), and a coil (18) movable in translation about a longitudinal axis (Z) relative to the external chassis (12), the coil (18) comprising a winding (19), c) a diaphragm (20), and d) a suspension device (22) for the diaphragm (20) and the coil (18), characterized in that the suspension device (22) comprises: i) a peripheral suspension (44) extending radially relative to the longitudinal axis (Z) between a proximal edge (50) and a distal edge (52), the distal edge (52) being connected to the external chassis (12); ii) an intermediate connecting device (46), placed between the external frame (12) and the membrane (20) along the longitudinal axis (Z), the intermediate connecting device (46) extending: - along the longitudinal axis (Z), between a lower base (54) on which the proximal edge (50) of the peripheral suspension (44) is fixed and an upper base (56), and - radially relative to the longitudinal axis (Z), between an inner circumference (58), mechanically attached to the coil (18), and an outer circumference (60), mechanically attached to the diaphragm (20); and iii) an internal suspension (48), which extends radially relative to the longitudinal axis (Z) between a proximal contour (72), fixed on an inner frame (74) of the loudspeaker (10) mechanically attached to the outer frame (12), and a distal contour (70) fixed on the upper base (56) of the intermediate linking device (46).

2. Loudspeaker (10) according to claim 1, wherein the intermediate linking device (46) is configured such that a distance (RG) between: - a center of gravity (G) of a moving assembly (23) comprising the coil (18), the diaphragm (20) and the suspension device (22), defined in an equilibrium position of the moving assembly (23) relative to the external chassis (12), and - a tilting center (R) with respect to which a moving subgroup (23A) of the moving assembly (23), said moving subgroup (23A) comprising the coil (18), the diaphragm (20) and the intermediate linking device (46), has a rigid body type mode of rotation, checks the relation RG < vkAGA +I(bGBd ans which RG denotes the distance between the center 'k B GB-k AGA ° of gravity (G) and the center of tipping (R), y denotes a predetermined coefficient, A and kA denote an attachment point on the moving assembly (23) and a stiffness constant of a first ideal spring (84) modeling a connection ensured by the peripheral suspension (44) between the moving assembly (23) and the external chassis (12), and B and k B designate an attachment point on the moving assembly (23) and a stiffness constant of a second ideal spring (86) modeling a connection ensured by the internal suspension (48) between the moving assembly (23) and the internal chassis (74).

3. Loudspeaker (10) according to claim 2 in which said predetermined coefficient (y) is less than or equal to 0.

100.

4. Loudspeaker (10) according to any one of the preceding claims, wherein the intermediate linking device (46) is formed in a material more rigid than the peripheral suspensions (44) and internal suspensions (48).

5. Loudspeaker (10) according to any one of the preceding claims, wherein the intermediate connecting device (46) comprises a lattice structure, the inner circumference (58) and the outer circumference (60) each being formed on a respective beam (64) of the lattice, said beams (64) being connected by a plurality of cross members (66).

6. Loudspeaker (10) according to claim 5, wherein the lattice is formed in a material such that the ratio of the Young's modulus of this material to the density of this material is greater than or equal to 1.9 x 10 9 Pa.kg' 1 .m 3 .

7. Loudspeaker (10) according to any one of the preceding claims, wherein the internal suspension (48) is not directly connected to the diaphragm (20).

8. Loudspeaker (10) according to any one of the preceding claims, comprising a single internal suspension (48).

9. Loudspeaker (10) according to any one of the preceding claims, wherein the winding (19) of the coil (18) extends along the longitudinal axis (Z) over a length less than that of an air gap (36) of a magnet (34) of the motor (14) attached to the base (12). 17 10. Loudspeaker (10) according to any one of the preceding claims, wherein the internal suspension (48) comprises a surface extending radially relative to the longitudinal axis (Z) and undulating along the longitudinal axis (Z), the amplitude (H) characteristic of the undulations along the longitudinal axis (Z) and / or the length (L) characteristic of the undulations radially relative to the longitudinal axis (Z) decreasing from the proximal contour (72) to the distal contour (70).

11. Loudspeaker (10) according to any one of the preceding claims, wherein the height of the loudspeaker along the longitudinal axis is less than 100 mm.

12. Loudspeaker (10) according to any one of the preceding claims, configured to emit sounds with a frequency between 20 Hz and 2,000 Hz.

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