WO2018220028A1

WO2018220028A1 - Electrodynamic loudspeaker with at least two seals defining an intermediate cavity filled with air

Info

Publication number: WO2018220028A1
Application number: PCT/EP2018/064210
Authority: WO
Inventors: Max RAINER
Original assignee: Devialet
Priority date: 2017-05-30
Filing date: 2018-05-30
Publication date: 2018-12-06
Also published as: FR3067203A1; FR3067203B1

Abstract

An electrodynamic loudspeaker (5) comprising: - a frame (3), - an assembly moving in translation with respect to the frame (3) along an axis (D) of the loudspeaker (5) about an equilibrium position that is occupied when the loudspeaker is at rest, the assembly comprising at least one membrane (25) configured to emit sound waves, and a connection member (31) attached on the membrane and extending from the membrane to the inside of the loudspeaker, and - a first seal (21) for suspending the assembly, connecting the assembly and the frame, the first seal having a cross-section projecting towards the inside of the loudspeaker. The loudspeaker further comprises a second seal (23) for suspending the assembly, connecting the connection member and the frame, the second seal being situated axially with respect to the first seal on the inside of the loudspeaker, the second seal being radially outside the connection member, the assembly, first seal, second seal and frame defining an intermediate cavity (37) filled with air and with restricted air leak.

Description

Electrodynamic loudspeaker with at least two joints defining an intermediate housing filled with air

The present invention relates to an electrodynamic loudspeaker comprising a frame, an assembly movable relative to the frame in translation along an axis of the loudspeaker around an occupied equilibrium position when the loudspeaker is at rest, the assembly having at least one membrane configured to emit sound waves, and a connecting member secured to the membrane and extending from the membrane to the interior of the speaker, and a first suspension joint of the connecting assembly the assembly and the frame, the first seal having a cross section projecting inwardly of the speaker.

It also relates to an acoustic enclosure comprising at least one such speaker.

In a loudspeaker, the suspension joint (s) serve, as their name indicates, to suspend the moving assembly comprising the membrane. The suspension is sufficiently firm to prevent radial deviations from the moving assembly that can lead to mechanical friction, and sufficiently flexible not to substantially change the axial vibrations, which would create a sound distortion.

Thus, it is known to use a flexible seal located axially near the membrane, in or under the gap between the peripheral edge of the membrane and the box. This seal is completed by a second accordion seal, known as the "spider".

The axial displacements of the membrane create internal pressure fluctuations under the first joint, which may be important in the bass speakers, due to the range of motion. This creates a risk of reversal of the first seal in the axial direction. The first seal, once returned, produces noise and causes a fault in the axial displacement of the membrane.

An object of the invention is therefore to provide an electrodynamic loudspeaker of the type described above, in which the risk of reversal of the first seal is minimized.

For this purpose, the subject of the invention is an electrodynamic loudspeaker of the type described above, in which a second suspension joint of the assembly connecting the connecting member and the frame, the second seal being situated axially by relative to the first seal on the inner side of the loudspeaker, the second seal being radially outside the connecting member, the assembly, the first seal, the second seal and the frame defining an intermediate housing filled with air and with limited air leakage. According to particular embodiments, the loudspeaker comprises one or more of the following characteristics, taken in isolation or in any technically possible combination:

the second seal has a transverse section projecting towards the inside of the intermediate housing in the equilibrium position;

the first seal and the second seal are structurally similar;

the first seal and the second seal have a cradle cross-section in the equilibrium position;

the connecting member is of substantially cylindrical shape centered on the axis of the loudspeaker;

- In section according to any half-plane passing through the axis of the speaker and limited by the axis, the first seal has a first attachment point on the assembly, and a second attachment point on the frame , the second seal has a third attachment point on the assembly, and a fourth attachment point on the frame, and the first point, the second point, the fourth point and the third point form in this order a parallelogram in the equilibrium position;

in the equilibrium position, the first point and the second point are located axially substantially at the same level, and the third point and the fourth point are situated axially substantially at the same level;

the intermediate housing is configured to behave as a substantially watertight volume at the time scale of the worst sound waves, and has an internal pressure in the equilibrium position and is configured to allow, when the speaker is at rest, an equalization of the internal pressure at atmospheric pressure prevailing in the vicinity of the loudspeaker; and

the air situated in the intermediate housing has an internal pressure in the equilibrium position, the internal pressure having an initial value at an initial time, and the intermediate housing is configured so that the loudspeaker is at rest and subjected to at the initial time at a constant ambient pressure greater than 0.1 bar at the initial internal pressure, the internal pressure should be at least 0.04 seconds, preferably 1 second, or even 5 seconds from the initial time t ₀ to rise 0.05 bar.

The invention also relates to an acoustic enclosure comprising a loudspeaker as described above.

The invention finally relates to a motor vehicle equipped with at least one acoustic enclosure as described above. The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:

FIGS. 1 and 2 are perspective views of an acoustic enclosure according to the invention,

FIG. 3 is a sectional view of the acoustic enclosure shown in FIGS. 1 and 2, in a plane passing through an axis of a loudspeaker of the acoustic loudspeaker,

FIG. 4 is a detail of FIG. 3 centered on suspension joints of the subwoofer, and

FIG. 5 is an evolution diagram of the pressure in an intermediate housing of the loudspeaker shown in FIGS. 1 to 3.

With reference to FIGS. 1 to 3, an acoustic enclosure 1 according to the invention is described. The acoustic enclosure 1 is configured to be integrated in the passenger compartment (not shown) of a motor vehicle. The loudspeaker 1 comprises a box 3 advantageously of substantially spherical shape, a loudspeaker 5 according to the invention, and optionally one or more other speakers 7, 9 and 1 1.

The speaker 7 is for example structurally similar to the speaker 5 and will not be described in detail. The loudspeaker 7 advantageously arranged head to tail with the speaker 5 along an axis Δ of the loudspeaker 5.

The loudspeakers 9 and 11 are, for example, medium and treble loudspeakers configured to emit sound waves in a bandwidth ranging from 200 Hz to 25 kHz.

The loudspeaker 9 is for example configured to transmit directly into an interior volume (not shown) of the motor vehicle, while the speaker 1 1 is configured to transmit in one or conduits (not shown) defined by the passenger compartment. of the motor vehicle.

The loudspeaker 5 is advantageously a subwoofer, configured to transmit in a bandwidth, for example between 15 Hz and 500 Hz.

As can be seen in FIG. 3, the loudspeaker 5 comprises a chassis 13, a magnetic circuit 15 defining an air gap 17, and a set 19 movable relative to the chassis in translation along the axis Δ around an equilibrium position. busy when the speaker is at rest. The loudspeaker 5 further comprises a first gasket 21 and a second gasket 23 for suspending the assembly 19.

In the example shown, the frame 13 is quite small. The frame 13 is mechanically secured to the casing 3. The assembly 19 comprises a membrane 25 configured to emit sound waves, a coil holder 27 fixed on the membrane, a coil 29 fixed on the coil carrier and located in the gap 17, and a connecting member 31 also fixed on the membrane.

The spool holder 27 and the connecting member 31 are for example substantially cylindrical axis Δ.

The first gasket 21, the second gasket 23, the chassis 13, and gasketing rings 33, 35 define an intermediate air-filled housing 37 acting as a cushion, as will be explained later.

The first seal 21 and the second seal 23 are structurally similar, so only the first seal 21 will be described in detail structurally.

The first seal 21 surrounds the connecting member 31 around the axis Δ. The first seal 21 is advantageously of revolution about the axis D, and has a cradle cross section, the bottom of the cradle being rotated axially towards the inside of the intermediate housing 37 in the equilibrium position of the membrane 25.

The first seal 21 comprises an arcuate portion 39 forming a channel 41 below a peripheral edge 43 of the membrane 25 and an edge 45 of the box 3 located opposite the radial peripheral edge 43 in the position d balance of the membrane. The first seal 21 also comprises two flanges 47, 49 oriented towards the outside of the cradle.

The flange 47 is for example glued on the ring 33. The flange 47 has at least a first attachment point A in contact with the ring 33.

The rim 49 is for example also glued on the frame 13 and has a second attachment point B on the frame 13.

The second seal 23 has an inwardly directed cross-section of the intermediate housing 37. The second seal 23 has at least a third point C and a fourth attachment point D respectively in contact with the ring 35 and the frame 13.

The first point A, the second point B, the fourth point D and the third point C form in this order a parallelogram ABDC in the equilibrium position. This results in the volume of the intermediate housing 37 being not substantially modified by the axial displacements of the membrane 25, the parallelogram ABDC retaining substantially the same surface.

The first point A and the second point B are for example located axially at the same level. The third point C, the fourth point D are for example located axially also at the same level. The air in the intermediate housing 37 has an internal pressure in the equilibrium position. The intermediate housing 37 is configured to allow, when the speaker 5 is at rest, an equalization of the internal pressure at atmospheric pressure prevailing outside the speaker 5. The intermediate housing 37 is however relatively tight, so that this equalization requires a duration greater than the period of the lowest sound waves of the bandwidth of the loudspeaker 5.

The intermediate housing 37 has limited air leakage. Thus, the intermediate housing 37 is configured to behave advantageously as a substantially sealed volume at the time scale of the lowest sound waves (about 1/10 ^th of a second), but allows a balancing of its internal pressure with the outside for a longer period.

By "substantially sealed" is meant that the amount of air present in the intermediate housing 37 fluctuates by less than 80%, preferably less than 20%, or even less than 1% due to vibrations of the membrane 25.

For example, if the internal pressure of the intermediate housing 37 has an initial value P (t ₀ ) has an initial time t ₀ and the speaker 5 is at rest and subjected to the initial time t ₀ at a constant ambient pressure PA, 0.1 bar higher than the initial internal pressure P (t ₀ ), the intermediate housing is configured so that its internal pressure is at least 0.04 seconds, preferably 1 second, or even 5 seconds from the initial time t ₀ to rise by 0.05 bar.

The person skilled in the art knows how to obtain a restricted air leakage, for example by providing in the intermediate housing 37 passages (not shown) whose passage section is sufficiently small to obtain a quasi-tightness on the time scale of the most serious sound waves.

The operation of the speaker 1 will now be briefly described.

When the loudspeaker 5 is at rest, the internal pressure of the intermediate housing 37 is equalized with the ambient pressure PA, for example in about 50 seconds, as shown in FIG.

Alternatively, the equalization time is a little shorter or a little longer, but it remains in any case greater than the period of the lowest sound waves of the bandwidth of the speaker 5.

When the membrane 25 is driven by axial vibrations, the internal pressure of an internal volume 51 located under the membrane and under the seals (Figure 4) fluctuates up to about 0.1 bar. In particular, when the membrane 25 is moved towards the inside of the speaker 5, this internal pressure increases. In the absence of the intermediate housing 37, this increase in pressure would apply to the first seal 21 and may return it. The first seal 21 could then affect the sound quality.

Thanks to the characteristics described above, in particular the presence of the intermediate housing 37, these pressure fluctuations are not or hardly felt by the first seal 21. Thus, the risk of reversal of the first seal 21 is greatly reduced or canceled.

Claims

1 .- Electrodynamic loudspeaker (5) comprising:

a chassis (3),

- A set (19) movable relative to the frame (3) in translation along an axis

(Δ) of the loudspeaker (5) around an occupied equilibrium position when the loudspeaker (5) is at rest, the assembly (19) comprising at least one membrane (25) configured to emit waves sound, and a connecting member (31) attached to the diaphragm (25) and extending from the diaphragm (25) to the interior of the speaker (5), and

a first suspension joint (21) of the assembly (19) connecting the assembly (19) and the frame (3), the first seal (21) having a cross section projecting towards the inside of the loudspeaker (5)

characterized in that it further comprises a second joint (23) for suspending the assembly (19) connecting the connecting member (31) and the frame (13), the second seal (23) being situated axially by in relation to the first seal (31) on the inner side of the loudspeaker (5), the second seal (23) being radially outside the connecting member (31),

the assembly (19), the first seal (21), the second seal (23) and the frame (3) defining an intermediate housing (37) filled with air and with limited air leakage.

The loudspeaker (5) according to claim 1, wherein the second seal (23) has an inwardly projecting cross-section of the intermediate housing (37) in the equilibrium position.

3. - Loudspeaker (5) according to claim 1 or 2, wherein the first seal (21) and the second seal (23) are structurally similar.

4. - Loudspeaker (5) according to claim 3, wherein the first seal (21) and the second seal (23) have a cradle cross section in the equilibrium position.

5. Loudspeaker (5) according to any one of claims 1 to 4, wherein the connecting member (31) is of substantially cylindrical shape centered on the axis (Δ) of the speaker.

6. A loudspeaker (5) according to any one of claims 1 to 5, wherein, in section along any half-plane (X) passing through the axis (Δ) of the speaker (5) and limited by the axis (Δ): the first seal (21) has a first attachment point (A) on the assembly (19), and a second attachment point (B) on the frame (13),

the second seal (23) has a third attachment point (C) on the assembly (19), and a fourth attachment point (D) on the frame (13), and

the first point (A), the second point (B), the fourth point (D) and the third point (C) form in this order a parallelogram (ABDC) in the equilibrium position.

7. The loudspeaker (7) according to claim 6, wherein, in the equilibrium position:

the first point (A) and the second point (B) are located axially substantially at the same level, and

the third point (C) and the fourth point (D) are located axially substantially at the same level.

8. Loudspeaker (5) according to any one of claims 1 to 7, wherein the intermediate housing (37):

is configured to behave as a substantially watertight volume at the time scale of the worst sound waves, and

has an internal pressure (P) in the equilibrium position and is configured to allow, when the loudspeaker (5) is at rest, an equalization of the internal pressure (P) with the atmospheric pressure prevailing in the outer vicinity of the speaker (5).

9. - Loudspeaker (9) according to any one of claims 1 to 8, wherein: - the air located in the intermediate housing (37) has an internal pressure (P) in the equilibrium position, the internal pressure having an initial value (P (t ₀ )) at an initial time (t ₀ ), and

the intermediate housing (37) is configured so that the loudspeaker is at rest and subjected to the initial time (t ₀ ) at a constant ambient pressure (PA) 0.1 bar higher than the initial internal pressure (P ( t ₀ )), the internal pressure (P) sets at least 0.04 seconds, preferably 1 second, or even 5 seconds from the initial time t ₀ to increase by 0.05 bar.

10. - acoustic chamber (1) comprising at least one loudspeaker (5) as described by any one of claims 1 to 9.