EP3284269A1

EP3284269A1 - Suspension device for a loudspeaker, manufacturing method and associated loudspeakers

Info

Publication number: EP3284269A1
Application number: EP16717319.4A
Authority: EP
Inventors: Giuliano NICOLETTI
Original assignee: Focal JMLab SAS
Current assignee: Focal JMLab SAS
Priority date: 2015-04-15
Filing date: 2016-04-12
Publication date: 2018-02-21
Anticipated expiration: 2036-04-12
Also published as: FR3035295B1; US10171913B2; FR3035295A1; US20180124519A1; EP3284269B1; WO2016166111A1

Abstract

The invention relates to a suspension device for a loudspeaker, comprising an annular outer edge (12) that is able to fasten the suspension device to a frame (13), an annular inner edge (14) that is able to fasten the suspension device to a membrane (15), a suspension hoop (16) that extends annularly between the edges, said suspension hoop (16) being able to absorb movement stresses produced at the inner edge (14) by means of a deformation that thus forms a resonance mode, the suspension hoop (16) comprising at least one annular protuberance (20) that is positioned so as to minimize the at least one resonance mode of the suspension hoop (16), the mass of the at least one annular protuberance (20) being between 150% and 400% the mass of a part of the suspension hoop (16) on which the at least one annular protuberance (20) is positioned.

Description

SUSPENSION DEVICE FOR SPEAKER, METHOD OF

MANUFACTURE AND ASSOCIATED SPEAKERS

TECHNICAL AREA

The invention relates to the field of acoustic equipment. It relates to a suspension device for a loudspeaker, and more specifically to a suspension device connecting a chassis of a loudspeaker with a membrane. It also relates to a method of manufacturing the suspension device and a loudspeaker comprising such a suspension device. The invention more specifically relates to a new suspension device which has advantages in terms of acoustic performance, particularly with regard to the regularity of the frequency response curve. PRIOR ART

In general, a loudspeaker comprises a fixed frame and a circular mobile membrane mechanically associated with a coil traversed by a current representative of the acoustic signal to be generated. The loudspeaker also comprises a magnetic field source, generally constant, which interacts with the current flowing through the winding to allow movement of the winding and therefore of the membrane.

The movements of the circular membrane relative to the frame are guided by an annular suspension device comprising an annular outer edge adapted to fix the suspension device on the frame and an annular inner edge adapted to fix the suspension device with the circular membrane. Between these two annular edges, the suspension device comprises a suspension arc intended to absorb displacement stresses produced on the inner edge.

However, during the absorption of the displacement stresses, the deformations of the suspension arc create oscillations around the position of the suspension arc when it is not in an absorption situation. These oscillations can resonate and form a resonance mode degrading the quality of the acoustic wave emitted by the speaker.

To eliminate these modes of resonance, it is known to increase the rigidity of the suspension arc. US Pat. No. 7,463,749 proposes to position three hemi-toric protuberances under the suspension arch in order to increase its rigidity and to limit its deformations. US patent application US 2002/005158 also proposes positioning hemi-toric excrescences in the center of the arc of suspension.

However, the rigidity of the suspension arc conditions the dynamics of the loudspeaker, that is to say the time required for the speaker diaphragm to move when a setpoint is applied thereto. For an ideal loudspeaker, the membrane is free in the air and when a displacement instruction is applied to the membrane, it can respond directly by moving. The suspension device has the primary function of guiding the displacement of the membrane in translation, but it constitutes a brake on the movement of the membrane because it must overcome the rigidity of the suspension arc to effect a displacement following a command . Thus, the solution of US Pat. No. 7,463,749 and US patent application US 2002/005158 consisting of limiting the deformations of the suspension arc is not optimal because it greatly degrades the dynamics of the loudspeaker.

The patent application US 2003/0228027 proposes to position one or two partial O-shaped protuberances on the suspension arc to limit its deformations. He also proposes to limit the stiffness of the suspension arc by means of a circular profile of the crenellated growths. The profile of the crenellated growths limits the weight of the suspension arc and has recesses whose length is determined by empirical tests.

However, picking up and plotting the response curve of a loudspeaker is a complex operation, often a long one, using rare equipment such as an anechoic chamber. The empirical definition of the shape of the slots associated with each range of loudspeakers therefore constitutes a particularly long operation.

In addition, the protrusions of US patent application 2003/0228027 do not follow the circular shape of the suspension arc. The annular resonances induced by the slot shape must therefore be damped so as not to degrade the performance of the loudspeakers thus limiting the effectiveness of this device.

The technical problem of the invention is therefore to effectively absorb the resonance modes of a speaker suspension device without negatively impacting the performance of the suspension device.

SUMMARY OF THE INVENTION

The present invention aims to provide a more easily achievable device comprising a suspension arc capable of effectively absorbing oscillations and whose weight is controlled by means of at least one protrusion whose position is determined according to the position of the resonance mode. According to a first aspect, the invention relates to a suspension device for a loudspeaker, this device comprising an annular outer edge adapted to fix the suspension device with a frame, an annular inner edge adapted to fix the suspension device with a membrane. , and a suspension arc extending annularly between the outer and inner edges. This suspension arc is able to absorb displacement stresses produced at the inner edge by means of a deformation of the suspension arc thus forming at least one resonance mode. This suspension arc comprises at least one annular protrusion positioned so as to minimize the at least one resonant mode of the suspension arc, the mass of each of this annular protrusion being between 150% and 400% of the mass of d a part of the suspension arc on which the annular protuberance is positioned.

The invention thus makes it possible to quickly and accurately define the position of the excrescences capable of significantly reducing the resonances. In addition, the controlled weight of the growths limits the impact of these growths on the dynamics of the loudspeaker.

Within the meaning of the invention, an annular protrusion positioned so as to minimize the at least one resonance mode of the suspension arc corresponds to an outgrowth of which a positioning study has been carried out when the suspension arc is not not provided with the protrusion so as to locate at least one mode of resonance of the suspension arc. This protrusion is therefore different from the protrusions of the US patent application US 2002/005158 which are simply positioned in the middle of the suspension arc without taking into consideration at least one resonant mode of the suspension arc.

According to one embodiment, this annular protrusion forms a regular material thickness of circular radial section. This form of outgrowth is particularly simple to control in terms of weight. In addition, adjustments in loudspeaker dynamics can be made by changing the radius of the circular radial section of the protrusion.

According to one embodiment, the mass of the at least one annular protrusion corresponds to approximately 250% of the mass of a portion of the suspension arc on which the at least one annular protrusion is positioned. This value makes it possible to obtain a particularly suitable compromise between the dynamics of the loudspeaker and the need to reduce the resonances of the suspension arc.

According to one embodiment, the device comprises one, two or three annular excrescences. According to a second aspect, the invention relates to a method of manufacturing a speaker suspension device as described above comprising the steps of:

- excite the inner edge of the suspension device,

measuring, during a duration of characterization, the displacements of the suspension arc with respect to a stable state of the suspension arc,

detecting the position of the first local maximum of displacements of the suspension arc with respect to the stable state of the suspension arc, and

defining a position of an outgrowth corresponding to a projection of the first local maximum on the suspension arc in the stable state.

This manufacturing method makes it possible to determine the position of the excrescences capable of significantly reducing the oscillations by means of a single numerical analysis of the displacements of the suspension arc. The position of the local maximum relative to the stable state of the suspension arc makes it possible to highlight both the hollows and the bumps resulting from the deformations of the suspension arc.

According to one embodiment, the step of defining a position of an outgrowth comprises the steps of:

define at least one set of positions whose distance between the positions is less than 20% of the total distance of the arc of suspension in the stable state, and

determining an average position of the at least one set of positions corresponding to the position of the outgrowth.

This embodiment makes it possible to eliminate the double positions detected using an averaging whose accuracy of 20% is particularly suitable.

According to one embodiment, the step of exciting the inner edge of the suspension device is performed with a characteristic signal whose frequencies evolve in a predetermined frequency range, preferably between 100 Hz and 10 KHz. It is well known that very high-end suspension devices are made to be effective over a characteristic frequency range. This embodiment makes it possible to manufacture a suspension device that is particularly suited to its characteristic frequency range.

According to one embodiment, the method comprises the steps of:

numerically modeling the dynamics of the suspension device as a function of the measurements, during the duration of the characterization, of the displacements of the suspension arc with respect to a stable state of the suspension arc, and

define the size of the outgrowth by numerical simulation of the previously defined model so as to minimize the resonance modes and limit the impact of the weight of the outgrowth. This embodiment makes it possible to numerically define the size of the protuberance thus improving the resonance reduction performance and limiting the impact of the weight of the protrusion on the suspension arc.

According to one embodiment, the method comprises the following steps:

- Exciting a second time the inner edge of the improved suspension device when an annular protrusion has been positioned on the suspension device and the suspension device still has detrimental modes of resonance,

measuring, during a second duration of characterization, the displacements of the improved suspension arc, that is to say provided with the annular protrusion, with respect to a stable state of the improved suspension arc ,

detecting the position of the second local maximum of the displacements of the improved suspension arc relative to the stable state of the improved suspension arc, and

defining a position of a second protrusion corresponding to a projection of the second local maximum on the improved suspension arc in the stable state.

This embodiment makes it possible to position a second protrusion in order to further limit the resonant modes of the suspension device. As a variant, these steps may be repeated to add a third protrusion if the limitation of the resonance modes is still not sufficient.

According to a third aspect, the invention relates to a loudspeaker comprising a frame, a diaphragm movable in translation, and a suspension device as described above.

SUMMARY DESCRIPTION OF THE FIGURES

The manner of carrying out the invention as well as the advantages which result therefrom, will emerge from the following embodiment, given by way of indication but not by way of limitation, in support of the appended figures in which FIGS. 1 to 11 represent:

- Figure 1: a radial sectional view of a suspension device in a stable state;

- Figure 2: a radial sectional view of the suspension device of Figure 1 in a first excitation state;

- Figure 3: a radial sectional view of the suspension device of Figure 1 in a second excitation state;

- Figure 4: a radial sectional view of the suspension device of Figure 1 in a third state of excitation;

- Figure 5: a radial sectional view of the suspension device of Figure 1 in a step of defining sets of positions; - Figure 6: a radial sectional view of the suspension device of Figure 1 in a step of defining a mean position;

- Figure 7: a radial sectional view of a suspension device provided with three annular protrusions according to a first embodiment of the invention; - Figure 8: an enlargement of a radial protuberance of Figure 7;

- Figure 9: a radial sectional view and in perspective of a suspension device provided with two annular protrusions according to a second embodiment of the invention;

- Figure 10: a radial sectional view and in perspective of a suspension device provided with two annular growths according to a third embodiment of the invention; and

- Figure 11: a radial sectional view and in perspective of a suspension device provided with a single annular protrusion according to a fourth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figures 1 to 8 describe the method of producing the suspension device according to the invention. In a first step illustrated in FIG. 1, a suspension device 10 to be improved is observed for a stable state. The suspension device 10 has a fixed outer annular edge 12 and an annular inner edge 14 fixed to a translational membrane 15. A suspension arc 16 annularly connects the two edges 12, 14. The membrane 15 is then moved to measure the induced displacements of the suspension arc 16 during a duration of characterization. Preferably, the membrane 15 is moved on frequencies contained in a frequency range associated with the suspension device. Preferably, the excitation signal of the membrane corresponds to a sinusoidal signal whose amplitude is constant and whose frequency is variable between a low frequency and a high frequency in the frequency range, for example in the frequency range. 100Hz to the OKHz.

Figures 2 to 4 reveal the resonances induced on the suspension arc 16 by the displacements of the membrane 15. The resonances of the suspension arc 16 during the duration of characterization are digitally captured by sampling and each sample is analyzed to detect local maxima 17.

The measurements are preferably carried out by an interferometry system. The suspension device 10 is placed on a dedicated support, and a laser is positioned on a support movable along three axes so as to scan the entire emitting surface of the suspension device 10. The laser makes it possible to measure the displacements of the suspension device 10 during the duration of characterization. This measure provides measuring the sound pressure and harmonic distortion curves of the suspension device 10 during the characterization period.

Figures 2 to 4 show three of these samples with reference to the suspension device 16 of Figure 1. The local maxima correspond to the peaks of the bumps and troughs formed by the suspension arc 16 over time. The first maxima 17 and its projection on the suspension arc 16 in the stable state (FIG. 1) is measured, that is to say the maxima 17 closest to the annular inner edge 14 capable of fixing the device of FIG. suspension with a membrane 15.

In FIG. 5, the projection of the maxima 17 is marked on the suspension arc 16 in the stable state (FIG. 1) thus making it possible to determine the position of at least one protrusion 20.

The characteristic "positioned so as to minimize the at least one resonance mode" is thus interpreted in this document as being positioned on the suspension arc 16 on the first local maximum 17.

When several positions are determined, it may be useful to gather the nearest positions to avoid double detections that correspond to the same weakness of the suspension arc 16. To do this, Figure 5 reveals that the positions 18 detected are grouped according to sets 19 whose distance is less than 20% of the total distance of the suspension arc 16 in the stable state. The position of each protrusion 20 is then an average position 21 between the positions 18 of each set 19. FIG. 6 reveals three average positions 21 detected during an analysis example corresponding to FIGS. 1 to 8.

A protrusion 20 is thus positioned on the suspension arch 16 at the average position 21. The frequency response of the suspension device 10 can thus be newly studied and if the response is not satisfactory, that is to say that is, the improved suspension arc 16 still has detrimental resonance modes, a new protrusion 20 can be added.

FIG. 7 illustrates an improved suspension arch 16 according to a first embodiment of the invention by three protuberances 20 whose position corresponds to the average positions 21 detected during three consecutive improvements of the suspension device 10. The annular protrusions 20 consist of of a regular material thickness of circular radial section.

FIG. 8 illustrates that the size of the annular growths is controlled so that the mass (or for a homogeneous material, the volume) of each outgrowth is between 150% and 400% of the mass of a part of the suspension arc 16 on which the at least one annular protrusion 20 is positioned. Thus, the volume of the outgrowth is between 150% and 400% of the volume 24 of the portion of the suspension arc 16 on which the protrusion 20 is implanted. Preferably, the volume of the protrusion 20 corresponds to 250% of the volume 24 of the portion of the suspension arc 16.

Alternatively, the weight of each protrusion 20 can be defined numerically using a numerical model of the suspension device 10. The dynamics of the suspension device 10 is then modeled numerically as a function of the measurements of the displacements of the arc. suspension 16. The size of the protrusion 20 is sought by numerical simulation of the previously defined model so as to minimize the resonance modes and limit the impact of the weight of the protrusion 20.

The size of the protrusion 20 is changed between two numerical simulations to travel the mass ratio from 150% to 400% with a predefined calculation step, about 10%>. For each simulation, the response is observed in order to calculate the amplitude of the oscillations of the suspension device 10 and the rigidity of the annular inner edge 14. The amplitude of the oscillations of the suspension device 10 makes it possible to estimate numerically the resonance modes, it is therefore necessary that this amplitude be minimal. The rigidity of the annular inner edge 14 makes it possible to estimate numerically the impact of the weight of the protrusion 20, this rigidity must also be minimal. The more the weight of the protrusion increases, the more the amplitude decreases and the stiffness increases. The main concern is to reduce the resonance modes then, the weight of the protrusion 20 will be increased numerically in the mass ratio 150% (400%) to halve the amplitude of the oscillations with respect to the variations of the device. suspension 10 without outgrowth.

In another variant, the weight of each outgrowth 20 can be defined as a function of the maximum distance of the local maximum 17 with the stable state of the suspension arc 16 during the duration of the characterization while remaining in the ratio of mass 150% to 400%.

Figures 9, 10 and 11 show three different embodiments in which the stresses applied to the suspension device are different. As a result, the number of growths differs, namely two for FIGS. 9 and 10 and only one for FIG. 11, and the position of the growths also differs between FIGS. 9 to 11.

The invention thus makes it possible to suppress only the oscillations of the suspension arc 16 which are identified as detrimental to the listening quality. However, it aims not to reduce all oscillations because it would lead to a reduction of the loudspeaker dynamic too important. In addition, the weight of the excrescences 20 is controlled to limit the degradation induced on the dynamics of a speaker.

The invention thus makes it possible to propose a loudspeaker whose acoustic performance is increased by means of the suspension device of the invention.

Claims

A suspension device (10) for a loudspeaker, said device comprising:

an annular outer edge (12) able to fix the suspension device (10) with a frame (13),

an annular inner edge (14) able to fix the suspension device (10) with a membrane (15),

- a suspension arc (16) extending annularly between the outer (12) and inner (14) edges,

said suspension arc (16) being able to absorb displacement stresses produced on the inner edge (14) by means of a deformation of the suspension arc (16) thus forming at least one resonance mode,

characterized in that the suspension arc (16) has at least one annular protrusion (20) positioned to minimize the at least one resonant mode of the suspension arc (16),

the mass of the at least one annular protuberance (20) being between 150% and 400%) of the mass of a portion of the suspension arch (16) on which the at least one annular protrusion (20) is positioned.

2. Suspension device according to claim 1, characterized in that said annular protuberance (20) forms a regular material thickness of circular radial section.

3. Suspension device according to claim 1 or 2, characterized in that the mass of the at least one annular protuberance (20) corresponds to 250%> of the mass of a part of the suspension arc (16) wherein the at least one annular protrusion (20) is positioned.

4. Suspension device according to one of claims 1 to 3, characterized in that it comprises one, two or three excrescences (20) annular.

A method of manufacturing a loudspeaker suspension device (10) according to one of claims 1 to 4, comprising the steps of:

- excite the inner edge (14) of the suspension device (10),

measuring, during a duration of characterization, the displacements of the suspension arc (16) with respect to a stable state of the suspension arc (16),

detecting the position of the first local maximum (17) of displacements of the suspension arc (16) relative to the stable state of the suspension arc (16), and - Define a position (18) of an outgrowth (20) corresponding to a projection of the first local maximum (17) on the suspension arc (16) in the stable state.

6. A method of manufacturing a suspension device according to claim 5, characterized in that the step of defining a position (18) of an outgrowth

(20) comprises the steps of:

defining at least one set (19) of positions (18) whose distance between the positions is less than 20% of the total distance of the suspension arc (16) in the stable state, and

determining an average position (21) of the at least one set of positions

(18) corresponding to the position of the protuberance (20).

7. A method of manufacturing a suspension device according to claim 5 or 6, characterized in that the step of exciting the inner edge (14) of the suspension device (10) is performed with a characteristic signal whose frequencies evolve in a predetermined frequency range, preferably between 100 Hz and 10 KHz.

8. A method of manufacturing a suspension device according to one of claims 5 to 7, characterized in that it comprises the steps of:

numerically modeling the dynamics of the suspension device (10) as a function of the measurements, during the duration of the characterization, of the displacements of the suspension arc (16) with respect to a stable state of the suspension arc (16); ), and

- Define the size of the protrusion (20) by numerical simulation of the previously defined model so as to minimize the resonance modes and limit the impact of the weight of the protrusion (20).

9. A method of manufacturing a suspension device according to one of claims 5 to 8, characterized in that it comprises the following steps:

- exciter a second time the inner edge (14) of the suspension device (10) improved when an annular protrusion (20) has been positioned on the suspension device (10) and the suspension device (10) still has harmful modes of resonance,

measuring, during a second duration of characterization, the displacements of the improved suspension arc (16), that is to say provided with the annular protrusion (20), with respect to a stable state of the suspension bow (16) improved,

detecting the position of the second local maximum (17) of displacements of the improved suspension arc (16) relative to the stable state of the improved suspension arc (16), and defining a position (18) of a second protrusion (20) corresponding to a projection of the second local maximum (17) on the suspension arc (16) improved in the stable state.

10. Speaker comprising:

a chassis (13), and

a diaphragm (15) movable in translation,

characterized in that it comprises a suspension device according to one of claims 1 to 4 made by a method according to one of claims 5 to 9.