Electrodynamic loudspeaker

Abstract

Electrodynamic loudspeaker The electrodynamic loudspeaker (10) includes a suspension device (22) for a diaphragm (20) and a voice coil (18) movable in translation about a longitudinal axis (Z), comprising 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 external frame (12) of the loudspeaker; an intermediate linking device (46) between the external frame (12) and the diaphragm (20) along the longitudinal axis (Z), and extending along this axis between a lower base (54) on which said proximal edge (50) is fixed and an upper base (56), and radially relative to this axis, between an inner circumference (58), integral with the voice coil (18), and an outer circumference (60), integral with the diaphragm (20);and an internal suspension (48) extending radially relative to the longitudinal axis (Z) between a proximal contour (72), fixed on an internal frame (74) integral with the external frame (12) and a distal contour (70) fixed on said upper base (56). Figure for the abbreviation: 1;

Description

Title of the invention: Electrodynamic loudspeaker

[0001] 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.

[0002] An electrodynamic loudspeaker includes a vibrating element relative to a magnet and configured to be operated in piston mode, i.e. in translational vibration along a longitudinal axis.

[0003] 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.

[0004] With regard to the spatial aspect, the size of the loudspeaker must most often be controlled, whether the loudspeaker is used alone in free placement or after integration into another device, for example in a soundproof enclosure or in a vehicle.

[0005] A loudspeaker must also meet a set of specifications that are more or less stringent in terms of sound quality and sound pressure level (SPL). In particular, it is desirable to limit sound distortion within the loudspeaker's bandwidth.

[0006] The rotational vibration modes (in English, "rocking mode") of the vibrating element are notably responsible for such distortions and a loss of acoustic efficiency.

[0007] 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.

[0008] Document DK 178810 describes a low-profile loudspeaker in which the impact of rotational vibration modes is reduced. This loudspeaker includes, for this purpose, a double "spider" type suspension, i.e., one formed from a corrugated material. The double suspension is positioned below the diaphragm and is attached at one end to the diaphragm and at the other end to a top plate located above the magnet.

[0009] In such a loudspeaker, it is very difficult to control rocking, that is, the rotational movements of the moving parts of the loudspeaker that appear during operation of the loudspeaker due to asymmetries in shape during the production of the different moving parts and / or the air gap in which oscillates the excitation coil and / or asymmetries created during the assembly of these different elements.

[0010] These tilting movements can lead to impacts between the moving and fixed parts of the loudspeaker, which impair the quality of the sound emitted and cause premature wear of the loudspeaker.

[0011] This loudspeaker also does not give complete satisfaction in terms of sound distortion or in terms of compactness.

[0012] One object of the invention is then to propose a loudspeaker for which the risk of tipping is reduced, preferably more compact, in particular in the direction of the piston mode, and / or allowing a quality sound reproduction, in particular with a reduced total harmonic distortion (in English, "Total Harmony Distortion", THD), in particular in the low frequencies, the loudspeaker being if possible easy to produce industrially.

[0013] To this end, the invention relates to an electrodynamic loudspeaker comprising:

[0014] a) an external chassis, b) a motor comprising a base mechanically fixed to the external chassis, and a coil movable in translation about a longitudinal axis relative to the external chassis, the coil comprising a winding, c) a diaphragm, and d) a device for suspending the membrane and the coil, characterized in that the suspension device comprises: i) a peripheral suspension extending radially relative to the longitudinal axis between a proximal edge and a distal edge, the distal edge being connected to the external frame; ii) an intermediate connecting device, placed between the external frame and the membrane along the longitudinal axis, the intermediate connecting device extending: - along the longitudinal axis, between a lower base to which the proximal edge of the peripheral suspension is fixed and an upper base, and - radially relative to the longitudinal axis, between an inner circumference, mechanically fixed to the coil, and an outer circumference, mechanically fixed to the diaphragm; and iii) an internal suspension, which extends radially relative to the longitudinal axis between a proximal contour, fixed on an internal chassis of the loudspeaker mechanically attached to the external chassis, and a distal contour fixed on the upper base of the intermediate linking device.

[0015] 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.

[0016] The choice of mass distribution of the intermediate linking 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.

[0017] 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 assembly, 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 assembly and / or the air gap in which the coil is intended to oscillate.

[0018] Such asymmetries do indeed increase the sensitivity of the loudspeaker to tilting.

[0019] 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.

[0020] The mechanical intermediary also ensures that neither the diaphragm nor the moving assembly, and in particular the voice coil, is directly connected simultaneously to the peripheral suspension and the internal suspension. Thanks to the intermediate connection device, the mass localization on the diaphragm is thus reduced compared to prior art loudspeakers, and the stiffness of the suspension system is particularly well controlled.

[0021] According to other advantageous aspects of the invention, the loudspeaker comprises one or more of the following features, taken individually or in all technically possible combinations:

[0022] - the intermediate linking device is configured so that a distance (RG) between: * 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) with respect to 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 type mode of rotation, satisfies the relation "k^GAAk^B1", in which RG denotes the distance between y kgGB-k^A the center of gravity (G) and the center of tipping (R), y denotes a coefficient predetermined, A and kA denote an attachment point on the moving assembly and a stiffness constant of a first ideal spring modeling a connection ensured by the peripheral suspension between the moving assembly and the external chassis, and B and kB denote 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;

[0023] - the predetermined coefficient is less than or equal to 0.100;

[0024] - the intermediate connecting device is formed in a material more rigid than the peripheral and internal suspensions;

[0025] - the intermediate connecting device comprises a lattice structure, the inner circumference and outer circumference each being formed on a respective beam of the truss, said beams being connected by a plurality of crossbeams;

[0026] - the lattice is formed in a material such that the ratio of the Young's modulus of this material and the density of this material is greater than or equal to 1.9.109 Pa.kg '.m3;

[0027] - the internal suspension is not directly connected to the membrane;

[0028] - the loudspeaker comprises a single internal suspension;

[0029] - the coil winding extends along the longitudinal axis over a length inferior to that of an air gap of a motor magnet attached to the base;

[0030] - the internal suspension comprises a surface extending radially relative to the longitudinal axis and wavy 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;

[0031] - the height of the loudspeaker along the longitudinal axis is less than 100 mm;

[0032] - the loudspeaker is configured to emit sounds with a frequency between 20 Hz and 2000 Hz.

[0033] 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:

[0034] [Fig. 1] [Fig. 1] is a cross-sectional view of an electrodynamic loudspeaker according to the invention in a plane containing the longitudinal axis; and

[0035] [Fig.2] [Fig.2] is an enlarged view of part of the loudspeaker in [Fig.1]; and

[0036] [Fig.3] [Fig.3] is a schematic representation of the upper moving group speaker of the [Fig.l] in the main tilting mode and models of the mechanical actions exerted on this moving group.

[0037] With reference to figures 1 and 2, an electrodynamic loudspeaker 10 according to the invention is described.

[0038] The speaker 10 is, for example, a speaker configured to emit sounds in the low frequency range, also referred to by the English term "woofer".

[0039] In particular, the speaker 10 can be configured to emit sounds with frequencies between 20 Hz and 2000 Hz

[0040] The loudspeaker 10 comprises an external chassis 12, a motor 14 comprising a base 16 mechanically fixed to the external chassis 12 and a coil 8, 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.

[0041] The membrane 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.

[0042] The center of gravity of the moving crew 23 is designated in the following by point G, visible on [Fig.1] and, in a very schematic case, on [Fig.3].

[0043] 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 connecting the membrane 20 and the coil 18 which will be described later is called the center of tilt R, this mobile subgroup 23A being considered as 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 [Fig.3] in a very schematic way.

[0044] It is therefore understood that the mobile subgroup 23A behaves according to the excitation cases as a rigid or deformable solid.

[0045] As shown in [Fig.1], the longitudinal axis Z is advantageously an axis with respect to which the loudspeaker 10 has approximately rotational symmetry.

[0046] The external chassis 12 is also known as the “salad bowl”.

[0047] The external frame 12 comprises a base 24 and a circumferential wall 26 extending from the bottom 24 towards the front of the speaker 10.

[0048] 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.

[0049] The circumferential wall 26 has in the example a truncated conical shape with axis the longitudinal axis Z, flared towards the front of the loudspeaker 10.

[0050] 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.

[0051] The external chassis 12 extends around the engine 14, in particular the base 16 of the engine 14 to which it is mechanically attached.

[0052] 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 disposed.

[0053] The cylinder head 32 defines at least one air gap 36.

[0054] 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.

[0055] 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.

[0056] 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 [Fig.1].

[0057] The coil 18 includes a coil holder 40, on an outer surface of which the winding 19 is formed.

[0058] The spool holder 40 is for example cylindrical with axis the longitudinal axis Z.

[0059] The winding 19 is arranged in the air gap 36.

[0060] 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.

[0061] The oscillations of the coil 18 and in particular of the winding 19, allow the reproduction of sounds by the loudspeaker 10, by means of oscillations of the diaphragm 20.

[0062] The membrane 20 defines an acoustic radiation surface of the loudspeaker 10.

[0063] Advantageously, the membrane 20 has a convexity oriented towards the front of the loudspeaker 10.

[0064] In particular, the membrane 20 has a spherical cap or dome shape.

[0065] The membrane 20 has a peripheral edge 20a.

[0066] The peripheral edge 20a has in the example a substantially annular shape centered on the longitudinal axis Z.

[0067] To allow oscillations of the membrane 20 along the longitudinal axis Z, the membrane 20 is suspended by means of the suspension device 22.

[0068] The suspension device 22 includes a peripheral suspension 44, an intermediate linking device 46, and an internal suspension 48.

[0069] The peripheral suspension 44 extends radially relative to the longitudinal axis Z between a proximal edge 50 and a distal edge 52.

[0070] The peripheral suspension 44 extends around the longitudinal axis Z.

[0071] 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 axially turned towards the rear of the loudspeaker 10.

[0072] The peripheral suspension 44 is preferably airtight.

[0073] The peripheral suspension 44 is formed in an elastic material such as a 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).

[0074] 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.

[0075] The proximal edge 50 is linked to the intermediate linking device 46.

[0076] The intermediate linking device 46 is placed along the longitudinal axis Z between the external frame 12 and the membrane 20.

[0077] 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.

[0078] 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.

[0079] The moving subgroup 23A of the moving assembly therefore includes the coil 18, the intermediate linking device 46 and the diaphragm 20.

[0080] The intermediate linking device 46 is thus intended in particular to form with the membrane 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 mobile subgroup 23A.

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

[0082] To this end, the intermediate connecting 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 piece.

[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 on which the peripheral edge 20a of the membrane 20 is directly fixed, for example glued.

[0096] In a particular embodiment, shown in Figures 1 and 2, the intermediate connecting device 46 comprises a lattice structure.

[0097] The truss structure comprises a plurality of beams 64 extending around the longitudinal axis Z, linked by a plurality of cross members 66 extending radially relative to the longitudinal axis Z.

[0098] The internal circumference 58 and the external circumference 60 are in this case each formed on a respective beam 64.

[0099] The cross members 66 are preferably equidistributed around the longitudinal axis Z.

[0100] The implementation of a truss structure makes it possible to control the stiffness of the sub- mobile group 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.

[0101] The lattice structure is for example formed in a material having 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 and the density of the material is greater than or equal to 1.9 GPa.kg'.m3.

[0102] The truss structure optionally includes one or more connecting elements 68 extending radially from at least one beam 64.

[0103] The connection elements 68 are configured to compensate for a possible imbalance of the mobile crew 23, in particular of the mobile subgroup 23A, in the absence of these connection elements 68.

[0104] 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.

[0105] The internal suspension device 48 is commonly known by the English name "spider".

[0106] The internal suspension device 48 is formed in a more flexible material than the intermediate connecting device 46.

[0107] For example, the internal suspension device 48 is formed in a resin-loaded woven mesh material.

[0108] In particular, the woven mesh may comprise fibers selected from cotton fibers, polyester fibers, meta-aramid fibers and their mixtures.

[0109] The resin is for example a thermosetting resin, in particular a phenolic resin.

[0110] The internal suspension device 48 extends around the longitudinal axis Z.

[0111] 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.

[0112] 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 [Fig.2].

[0113] The internal suspension 48 thus forms a surface exhibiting corrugations of decreasing radii.

[0114] This arrangement makes it possible to increase the stiffness of the internal suspension 48 radially relative to the longitudinal direction, without significantly increasing the stiffness of the internal suspension 48 along the longitudinal direction. Thus, the amplitude of the radial displacement of the coil 18 is reduced without affecting the ability of the coil 18 to oscillate along the longitudinal direction of interest for reproduction no sound is affected. This arrangement further reduces the risk of tipping around the tipping center R in the bandwidth of the loudspeaker 10, particularly during large excursions of the coil 18 along the longitudinal axis Z relative to its equilibrium position, as will be explained at the end of this description.

[0115] Preferably, as shown in the figures, the internal suspension 48 is not directly linked to the membrane 20.

[0116] Preferably, as shown in the figures, the loudspeaker 10 comprises a single internal suspension 48.

[0117] The distal contour 70 of the internal suspension 48 is fixed to the upper base 56 of the intermediate connecting device 46. It is, for example, glued to the upper base 56, in front of it along the longitudinal axis Z.

[0118] The proximal contour 72 is fixed to the internal frame 74.

[0119] The internal chassis 74 is mechanically attached to the external chassis 12, in front of the external chassis 12 along the longitudinal axis Z.

[0120] The internal chassis 74 includes an external peripheral edge 76 extending around the longitudinal axis Z.

[0121] 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.

[0122] The outer peripheral edge 76 extends radially less far from the longitudinal axis Z than the circumferential wall 26 of the fixed frame 12.

[0123] The proximal contour 72 is for example fixed on the external peripheral edge 76, in particular glued to the external peripheral edge 76, in front of it in the longitudinal direction.

[0124] Advantageously, the internal frame 74 extends radially less far from the longitudinal axis Z than the internal circumference 58 of the intermediate connecting device 46, through this internal circumference 58 along the longitudinal axis Z.

[0125] Advantageously, the internal chassis 74 further comprises an internal peripheral edge 78.

[0126] 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.

[0127] The internal peripheral edges 78 and external peripheral edges 76 are then connected by an internal circumferential wall 80.

[0128] The internal circumferential wall 80 comprises, for example, a plurality of radial pillars 82 connecting the external peripheral edge 76 and the internal peripheral edge 78.

[0129] The radial pillars 82 are advantageously equidistributed angularly around the longitudinal axis Z.

[0130] 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”.

[0131] The internal chassis 74 is in the example mechanically fixed to the annular support 38 and in front of the annular support 38 along the longitudinal axis Z.

[0132] 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.

[0133] The centers of gravity G and tilting R can be visualized on [Fig. 1] when the moving assembly 23 is in equilibrium relative to the external chassis 12, and on [Fig. 3] in a particular position during a particular tilting movement of the moving subgroup 23A of the moving assembly 23.

[0134] 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 membrane 20, the suspension device 22 and / or the coil 18 which make up the moving assembly 23.

[0135] As a first intention, it is important to limit the amplitude of the tilting movement of the mobile subgroup 23A of the mobile crew 23 in the dominant rotation mode.

[0136] 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.

[0137] This is all the more problematic for low-frequency loudspeakers, for which the frequency of the dominant rotation mode, referred to hereafter as the fundamental switching frequency f0, is often included in a bandwidth of the loudspeaker 10,

[0138] 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 subgroup 23A 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 frame 12.

[0139] 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 on the [Fig.3].

[0140] 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: - 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 - a second ideal spring 86, without mass, linked at a point B to the moving assembly 23 visible in figures 1 and 3 and with a stiffness constant kB.

[0141] The set of forces 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 [Fig.3].

[0142] Applying the fundamental laws of dynamics to the moving assembly 23 in a frame of reference attached to the external chassis 12 shows that: - the distance RG between the center of tilt R and the center of gravity G is bounded by a maximum distance RGmax, for rotational oscillations of small angular amplitude, the following equation 1:

[0143] _ k^GB-k^GA / and - the amplitude 0max 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:

[0144] » = 2C = ________2C________ Q max kAGA2+kBGB2-RG (kfiB-k^GA}

[0145] It is therefore understood that the choice of the mass m of the moving assembly 23, of the distribution of this mass m in space (and in particular of the position of the center of gravity G), as well as the choice of the stiffnesses and positions of the peripheral suspensions 44 and internal suspensions 48 modeled by the first and second springs 84, 86 with stiffness constants kA and kB makes it possible to control the distance RG in all possible movements of the moving assembly 23 as well as the amplitude 0max of the oscillations during the tilting of the moving subgroup 23A of the moving assembly 23.

[0146] Consequently, the intermediate linking device 46, which allows action on all these factors influencing the dominant rotation mode, makes it possible to precisely limit the distance RG in all possible crew movements mobile 23 and the amplitude 0max of the tilting oscillations of the mobile subgroup 23A during the operation of the loudspeaker 10.

[0147] In particular, to minimize the amplitude 0max of the tilting oscillations, it is desirable to maximize the denominator of the last member of equation 2. For example, it is possible to configure the intermediate linking device 46 so that: k A G^ + k B GB 2 > RG. ( k B GB - k A GA) (3)

[0148]

[0149] or equivalently so that: k^AAk^B2 (4) GA

[0150] 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:

[0151] kAGA2+kBGB2 (4) Y kBGB-kAGA

[0152] By way of 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.

[0153] It will be noted that the positions of the attachment points A and B of the first and second springs 84, 86 modeling the links between the external chassis 12 and the internal chassis 74 and the moving assembly 23, the corresponding stiffness constants kA and kB, 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.

[0154] 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 [Fig.1].

[0155] 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.

[0156] 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.

[0157] 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, have been 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 voice coil (18) movable in translation about a longitudinal axis (Z) relative to the external chassis (12), the voice coil (18) comprising a winding (19), c) a diaphragm (20), and d) a suspension device (22) for the diaphragm (20) and the voice 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 linking device (46), placed between the outer frame (12) and the diaphragm (20) along the longitudinal axis (Z), the intermediate linking 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 fixed to the coil (18), and an outer circumference (60), mechanically fixed 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 to an inner frame (74) of the loudspeaker (10) mechanically fixed to the outer frame (12), and a distal contour (70) fixed to 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 voice 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), exhibits a rigid body type mode of rotation, satisfies the relation "fc4GA2+^BGB2", in which RG denotes the distance between the center of gravity (G) and the tilting center (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 kB denote 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 wherein 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 (44) and internal (48) suspensions.

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 1.9.109 Pa.kg *.m3.

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).

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 of frequency between 20 Hz and 2,000 Hz.

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