Loudspeaker with a reversibly mounted membrane and acoustic enclosure comprising such a loudspeaker

Description

[0001] The present invention relates to a loudspeaker of the type comprising a magnetic circuit defining at least one air gap, and a moving assembly adapted to vibrate relative to the magnetic circuit along an axis of the loudspeaker, the moving assembly comprising a voice coil holder, a coil fixed to the voice coil holder and located in the air gap, a diaphragm adapted to emit sound waves, and a linkage system connecting the diaphragm and the voice coil holder, the diaphragm defining a front side of the loudspeaker along the axis.

[0002] The invention also relates to an acoustic enclosure incorporating such a loudspeaker, and a method corresponding to this loudspeaker.

[0003] A bass speaker is designed to reproduce sound waves with frequencies below 1000 Hz, preferably below 500 Hz, and even more preferably below 150 Hz. When mounted externally, a bass speaker is generally attached to the internal structure of a loudspeaker enclosure using a mounting screw that passes axially through the magnetic circuit and whose head is located on the diaphragm side.

[0004] We know that the moving assembly behaves overall like a mass M suspended from a spring of stiffness K and has a resonance frequency f given by the following equation: f = 1 2 π K / M , in which: f is the frequency in Hz (hertz), M is the mass of the moving assembly in kg, and K is the stiffness of the suspensions in N / m (newton per meter).

[0005] Similarly, each component of the moving assembly and other parts subjected to cyclic stresses possesses an intrinsic mass and stiffness that give it a resonant frequency determined by an equation analogous to the one above. It is important that the K / M ratio of each component is not too low, for example, above 450 Hz, preferably above 1500 Hz, or even more preferably above 5000 Hz, thanks to sufficient stiffness and a moderate mass. Otherwise, new resonant frequencies could be excited by the speaker's operating frequencies, creating distortion of the acoustic wave radiated by the diaphragm.

[0006] It is also important that the membrane is securely fixed to the linking system, in order to avoid poor contact which could cause vibrations that disrupt the acoustic signal of the membrane.

[0007] Therefore, in order to comply with these constraints, the membrane is first glued to the linking system, then the moving assembly is connected to the rest of the loudspeaker by one or more flexible suspensions.

[0008] Next, when the speaker is finished, it is, for example, attached to an outer casing. Then the speaker / outer casing assembly is attached to an internal structure 22 (see figure 1 ) using a fixing screw (or other means of fixing).

[0009] The diaphragm creates a central opening that allows access to the mounting screw using a screwdriver from outside the speaker and the enclosure. Once the speaker is mounted, a cover is placed over the speaker to conceal the opening created by the diaphragm.

[0010] This manufacturing process is acoustically satisfactory. Furthermore, the cover allows for centering the speaker's moving part with its motor during manufacturing. However, the opening in the diaphragm that allows access to the mounting screw must in fine being hidden by the cover, which detracts from the continuous and smooth appearance of the speaker enclosure, and sometimes makes it unsightly to users.

[0011] US document 4,559,584 A describes a loudspeaker in which a diaphragm is connected to a chassis by peripheral fasteners.

[0012] Document FR 3 097 397 A1 describes an acoustic enclosure in which a loudspeaker is fixed to a chassis using a screw passing through the loudspeaker's magnetic circuit.

[0013] One aim of the invention is therefore to provide a loudspeaker whose structure is more continuous and smooth, so that it is perceived as more aesthetically pleasing by a user, while remaining easy to mount on the cabinet of a loudspeaker.

[0014] For this purpose, the invention relates to a loudspeaker according to claim 1.

[0015] According to particular embodiments, the loudspeaker comprises one or more of the features corresponding to claims 2 to 6, taken individually or according to all the claimed combinations.

[0016] The invention also relates to an acoustic enclosure according to claim 7.

[0017] The invention also relates to an assembly method according to claim 8.

[0018] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the attached drawings, in which: [ Fig 1 ] there figure 1 is a schematic cross-sectional view of a soundproof enclosure according to the invention, with the diaphragm in the disassembled position, [ Fig 2 ] there figure 2 is a cross-sectional view of a loudspeaker according to the invention, analogous to that schematically represented on the figure 1 , the membrane being in the mounted position, and [ Fig 3 ] there figure 3 is a detailed view of the speaker shown on the figure 2 centered on the threaded part of the membrane.

[0019] With reference to the figure 1 , an acoustic enclosure 10 is described according to the invention.

[0020] The acoustic enclosure 10 includes a box 12 defining an opening 14, a loudspeaker 16 extending across the opening 14 and defining an axis D, and a fixing system 18 adapted to fix the loudspeaker on the box.

[0021] According to an unrepresented variant, the acoustic enclosure 10 includes one or more other loudspeakers, advantageously including a loudspeaker similar to loudspeaker 16 and placed head-to-tail with loudspeaker 16.

[0022] In the example shown, the box 12 includes an outer envelope 20 which defines the opening 14, and an internal structure 22 attached to the envelope 20, or alternatively, made of material with the outer envelope.

[0023] Speaker 16 is, for example, a bass speaker, in the sense defined in the preamble above.

[0024] The internal structure of the loudspeaker 16 will now be described with reference to the diagram of the figure 1 , but especially also in reference to the example shown on the figures 2 And 3 .

[0025] Except in special cases mentioned below, the loudspeaker 16 is substantially of revolution around the axis D.

[0026] The loudspeaker 16 includes a chassis 24, a magnetic circuit 26 defining an air gap 28, and a moving assembly 30 adapted to vibrate relative to the magnetic circuit along the axis D.

[0027] The loudspeaker 16 also advantageously includes two suspensions 32, 34.

[0028] In the example shown, the suspension 32 is a flexible joint connecting the moving assembly 30 to the chassis 24.

[0029] The flexible joint 32, for example, has a "U" shaped cross-section along a radial half-plane P ( figure 2 ).

[0030] Continuing with the example, suspension 34 is a corrugated or pleated joint, known by the English name of " spider ", for example, connecting the mobile crew 30 to the chassis 24.

[0031] The moving assembly 30 includes a coil holder 36, and a coil 38 fixed to the coil holder and located in the air gap 28. The moving assembly includes a diaphragm 40 adapted to emit sound waves, and a linkage system 42 rigidly connecting the diaphragm and the coil holder 36, the diaphragm defining a front side of the loudspeaker along the axis D.

[0032] For example, the spool holder 36 is cylindrical.

[0033] The membrane 40 is reversibly movable between a mounted position (represented on the figure 2 ), in which the membrane is integral with the linking system 42, and a disassembled position (represented on the figure 1 ), in which the diaphragm is away from the linking system. In the mounted position, the diaphragm 40 forms a screen between the outside of the loudspeaker and the magnetic circuit 26.

[0034] By "forms a screen", we mean that the membrane opposes access to the magnetic circuit from the front side of the speaker in the mounted position.

[0035] Membrane 40 is advantageously made of plastic, for example ABS (acrylonitrile butadiene styrene).

[0036] In the mounted position, the diaphragm is screwed onto the connecting system 42. Advantageously, the diaphragm and the connecting system are tightened with a tightening torque about the axis D greater than or equal to 0.05 Nm, preferably greater than or equal to 0.5 Nm, and even more preferably 4 Nm, or even 9 Nm.

[0037] According to an unshown variant, the membrane has an external thread and is screwed into the linking system.

[0038] The membrane comprises a central part 44, a threaded part 46, and advantageously a plurality of ribs 50.

[0039] The membrane has a diameter D1 perpendicular to the axis D. In the mounted position, the membrane and the linking system 42 exert pressure forces on each other having an axial resultant R.

[0040] The central portion 44, for example, forms a dome directed axially forward in the membrane's mounted position. The central portion 44 has an advantageously smooth front face 52 and a rear face 54 bearing the ribs 50.

[0041] The central part 44, for example, forms a portion of a sphere.

[0042] Advantageously, the central part 44 is devoid of any opening.

[0043] As seen on the figure 3 , the threaded part 46 extends for example axially towards the rear from an edge 56 of the central part 44. The threaded part 46 has for example a general cylindrical shape with axis D, forming a skirt at the periphery of the central part 44.

[0044] The threaded part 46, for example, has a thickness substantially equal to that of the central part 44, and advantageously between 0.2 and 8 mm.

[0045] On its radially inner side, the threaded part 46 forms a thread 58 adapted to cooperate with the linking system 42.

[0046] Thread 58, for example, forms a single-turn helix around axis D.

[0047] Alternatively, thread 58 has several helices distinct from each other.

[0048] The ribs 50 extend radially, advantageously from a crown 60 centered on the axis D.

[0049] The ribs 50 have an axial extension E which is advantageously maximum at the level of the crown 60, and which reduces as one moves away from the axis D.

[0050] The axial extension E becomes zero in a peripheral zone 60 of the rear face 54.

[0051] In section along the radial half-plane P, the linkage system 42 comprises a radially internal end piece 62 fixed to the spool holder 36, and a radially external end piece 64 defining an external thread 66 around the axis D configured to cooperate with the threaded portion 46 of the diaphragm. The linkage system 42 includes a first plurality of arms 68 extending radially between the ends pieces 62 and 64, and advantageously a second plurality of arms 70 extending axially rearward from the end piece 64, or alternatively from the arms 68.

[0052] The tip 62 is for example of revolution around the axis D. The tip 62 advantageously defines a slot 72 in which the spool holder 36 is received.

[0053] The arms 70 are advantageously distributed discreetly around the axis D. The arms 70 respectively have ends 74 on which the suspension 34 is fixed.

[0054] The arms 68 are advantageously distributed discreetly around the axis D. Each of the arms 68 includes, for example, a base 76 connecting the ends 62 and 64, and a stiffening rib 78 extending radially.

[0055] The end piece 64 has a lower face 80 on which the suspension 32 is fixed, the base of the "U" of the suspension being directed axially towards the rear.

[0056] The tip 64 defines an annular groove 82 receiving a sealing gasket 84 compressed radially between the tip 64 and the threaded part 46 of the diaphragm in the mounted position.

[0057] The tip 64 forms for example a protrusion 86 abutting axially against a peripheral part 88 of the central part 44 of the membrane.

[0058] The peripheral part 88 is located radially between the part 60, where the ribs 50 are interrupted, and the edge 56 of the membrane.

[0059] In the raised position of the membrane, the protrusion 86 exerts pressure forces on the membrane, the axial resultant of which R1 is shown on the figure 3 .

[0060] The thread 66 of the nozzle 64 exerts pressure forces on the thread 58 of the diaphragm, the axial resultant of which R2 is shown on the figure 3 .

[0061] The fixing system 18 is for example a screw 90 received in an axial housing 92 passing through the magnetic motor 26.

[0062] The screw head 92 is accessible from outside the loudspeaker 16 when the diaphragm 40 is in the disassembled and set aside position, via a housing 94 defined by the voice coil holder 36 and the linkage system 42 and opening axially towards the front.

[0063] A method for mounting the acoustic enclosure 10 will now be described.

[0064] Initially, the loudspeaker 16 is assembled without the diaphragm 40, meaning that the diaphragm is in the disassembled position. Throughout this phase, access to the housing 94 is possible from outside the loudspeaker, which facilitates the centering of the voice coil holder 36 and the linkage system 42 relative to the magnetic circuit 26.

[0065] In a second step, the loudspeaker 16, still without the diaphragm 40, is placed across the opening 14 against the internal structure 22 of the enclosure 12. The loudspeaker 16, without the diaphragm, is then fixed to the enclosure using the fixing system 18, i.e., by screwing the screw 90 into the enclosure. This screwing operation is carried out by acting on the head 92 of the screw with a tool (not shown) inserted into the recess 94 from outside the loudspeaker enclosure.

[0066] Finally, the membrane 40 is reversibly moved from the disassembled position to the assembled position. In the example shown, the membrane 40 is screwed onto the connecting system 42.

[0067] The screwing is carried out until the desired tightening torque is obtained around axis D.

[0068] The membrane 40 and the connecting system 42 then exert the aforementioned pressure forces on each other. The protrusion 86 of the end piece 64 of the connecting system exerts pressure forces on the membrane with an axial resultant R1. The membrane exerts pressure forces on the protrusion with an axial resultant opposite to R1.

[0069] The thread 66 of the tip 64 exerts pressure forces on the thread 58 of the threaded part 46 of the diaphragm, having an axial resultant R2. The thread 58, in turn, exerts pressure forces on the thread 66, the axial resultant of which is opposite to R2.

[0070] Thanks to the characteristics described above, the membrane 40 is assembled last and does not need to define an access opening for the fixing system 18. As a result, in the mounted position, the membrane forms a screen between the exterior of the loudspeaker 16 and the magnetic circuit 26. Thus, a cover is not necessary, and the loudspeaker has a more continuous and smooth external appearance than in the prior art.

[0071] Since the membrane 40 is mounted reversibly, it can be easily removed without risk of damage to the speaker 16. However, the tightening torque value advantageously prevents a user from easily removing the membrane 40.

[0072] The assembly of the membrane 40 onto the rest of the moving assembly 30 advantageously requires no glue, and allows the desired stiffness to be achieved.

[0073] If further maintenance operations are required, dismantling membrane 40 is quick, easy and economical.

Claims

1. A loudspeaker (16) comprising: - a magnetic circuit (26) defining at least one air gap (28), and - a moving assembly (30) adapted to vibrate with respect to the magnetic circuit (26) along an axis (D) of the loudspeaker (16), the moving assembly (30) comprising a coil carrier (36), a coil (38) attached to the coil carrier (36) and located in the air gap (28), a membrane (40) suitable for emitting sound waves, and a connection system (42) connecting the membrane (40) and the coil carrier (36), the membrane (40) defining a front side of the loudspeaker (16) along the axis (D), wherein: - the membrane (40) is reversibly movable with respect to the connection system (42) between an assembled position, in which the membrane (40) is secured to the connection system (42), and a disassembled position, in which the membrane (40) is away from the connection system (42), and - in the assembled position, the membrane (40) forms a screen between the exterior of the loudspeaker (16) and the magnetic circuit (26), opposing access to the magnetic circuit (26) from the front side of the loudspeaker (16) in the assembled position, characterized in that the membrane (40) comprises a threaded part (46) adapted to be screwed along the axis (D) into or onto the connection system (42) in the assembled position.

2. The loudspeaker (16) according to claim 1, wherein, in the assembled position, the membrane (40) and the connection system (42) are tightened with a tightening torque about the axis (D) greater than or equal at 0.05 N.m.

3. The loudspeaker (16) according to claims 1 or 2, wherein the connection system (42) includes an end piece (64) defining an external thread (66) about the axis (D), the external thread (66) being configured to engage with the threaded part (46) of the membrane (40).

4. The loudspeaker (16) according to claim 3, wherein the end piece (64) defines an annular groove (82), the loudspeaker (16) having a sealing gasket (84) received in the groove (82) and radially compressed between the end piece (64) and the threaded part (46) of the membrane (40) in the assembled position.

5. The loudspeaker (16) according to claim 3 or 4, wherein the membrane (40) comprises a central portion (44) forming a dome directed axially outward from the loudspeaker (16) in the assembled position, the end piece (64) preferably forming a protuberance (86) abutting axially against a peripheral part (88) of the central portion (44) in the assembled position.

6. The loudspeaker (16) according to any one of claims 1 to 5, wherein the membrane (40) is made of plastic material, for example acrylonitrile butadiene styrene, and includes an inner face (54) preferably defining radial ribs (50).

7. An acoustic enclosure (10) including: - a box (12), - at least one loudspeaker (16) according to any one of claims 1 to 6, and - an attachment system (18) suitable for selectively attaching the loudspeaker (16) on the box (12), the attachment system (18) passing through the magnetic circuit (26) and being accessible from the front side of the loudspeaker (16) when the membrane (40) is in the disassembled position.

8. A method of assembling an acoustic enclosure (10) according to claim 7, comprising the following steps: - attaching the loudspeaker (16) to the box (12) using the attachment system (18) accessible from the front side of the loudspeaker (16), the membrane (40) being in the disassembled position, and - moving the membrane (40) reversibly from the disassembled position to the assembled position.