Loudspeaker

Abstract

A loudspeaker assembly (1) for use outside a vehicle is provided. The diaphragm (3) and the enclosure (7) are formed from a single piece of material comprising a single layer of woven fabric of orthogonally interwoven fibers and a thermosetting resin.

Description

[0001] Divisional Application Statement

[0002] This application claims priority from UK Patent Application No. 2108015.5 filed on June 4, 2021, PCT International Application No. PCT / EP2022 / 064971 filed on June 1, 2022, and entered China on November 30, 2023. It is a divisional application of a Chinese invention patent application with the application number 202280039459.5 and the invention title "Loudspeaker". Technical Field

[0003] The present invention generally relates to the field of external sound generating devices for vehicles. Specifically, the present invention relates to an acoustic vehicle warning system for outputting an acoustic warning signal. Background Art

[0004] The noise generated by slow-moving electric vehicles is too small to be noticed by pedestrians. This obviously creates safety problems, for example in front of schools, at pedestrian crossings or at traffic lights. Legislation has been adapted to solve this problem by mandating the generation of artificial sounds. Acoustic Vehicle Alerting Systems (AVAS) are designed to emit vehicle warning sounds and alert pedestrians to the presence of electric vehicles. These include hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV) and battery electric vehicles (BEV) traveling at low speeds, especially in the lowest speed range, below which the noise generated by rolling tires can no longer be easily heard.

[0005] A horn for generating a warning signal is installed in each vehicle. The horn signal has a typical sound that is automatically recognized as a horn by people. Although tonal differences may be observed between horn sound signals, people worldwide are accustomed to the sound of vehicle horns.

[0006] In the art, systems that combine the warning function of AVAS with the horn function are known. For example, US8217767B2 discloses a vehicle horn device that can be used as a dynamic loudspeaker to generate a pseudo-engine sound. The lack of low-pitched sounds in the parametric loudspeaker device is supplemented by the pseudo-engine sound generated by the vehicle horn device. When the vehicle approaches a pedestrian, the pitch of the pseudo-engine sound heard by the pedestrian changes, so that the pedestrian can easily notice the approach or presence of the vehicle.

[0007] US10406976B2 relates to a vehicle including a multi-purpose automotive sound device for alerting pedestrians. The sound device operates as a horn in a first mode in response to an external input (e.g., from the driver), and operates as a speaker or other sound generating device in a second mode in response to the vehicle moving backward or forward at a speed that meets a given threshold.

[0008] FR2983025 proposes a system for generating an external sound used in an electric motor vehicle. A hybrid transducer controlled by a common interface that ensures power distribution between a piezoelectric transducer and a magnetic transducer according to the desired function (e.g., an alarm function and a sound warning function).

[0009] In US2020 / 070719, an acoustic vehicle warning system for a motor vehicle is disclosed. The system includes at least one speaker and a control unit designed to output a continuous acoustic signal through the speaker during a driving operation of the motor vehicle. Further, the control unit can activate the speaker after an activation unit has been actuated, and the speaker is designed to output an acoustic warning signal after receiving the activation signal.

[0010] Traditional speakers utilize a diaphragm in the form of a cone made of a rigid material, connected to a surround made of a compliant / flexible material, which allows the cone to move axially easily. The cone is equipped with a central hole for connection to a voice coil former (so it is an open cone). The hole is closed by gluing a rigid dust cap above the voice coil former to the cone.

[0011] This method has several drawbacks. To form the exposed front surface, two connections must be made (connection of the diaphragm to the surround; connection of the dust cap to the diaphragm). This results in low efficiency in the speaker production process. Additionally, the two connections create a potential risk of water infiltration into the application on the exterior of the vehicle. Therefore, it is desirable to make the entire exposed front surface from a single piece of the same material that can be manufactured effectively.

[0012] Connecting the voice coil to a flat, circumferentially clamped membrane does not result in the desired acoustic behavior. The effective piston surface area of the membrane for acoustic radiation is small because the displacement radially decreases from a maximum at the center defined by the voice coil to zero at the clamped edge (see Figure 1 (b)). The modal behavior of the clamped membrane is also not ideal because a large number of resonances occur at low and mid frequencies within the rated frequency range of the speaker.

[0013] To overcome this behavior, the membrane is geometrically shaped. However, there is still a need for a speaker that also has the desired sound reproduction capabilities for various purposes.

[0014] In addition, cone speakers of the prior art can use cone materials having a Young's modulus in the range of 2 GPa to 10 GPa. To allow for easy cone movement, the connection between the cone and the frame is achieved through a compliant member (surround). The surround is typically made of rubber and has a Young's modulus in the range of 2 MPa to 10 MPa. Thus, the compliance of the surround is approximately 1000 times higher than that of the cone. This allows for a larger offset or movement of the rigid cone. Typically, the cone can move 2 mm to 10 mm from its relaxed position (i.e., its position is relaxed position ±2 mm to ±10 mm); in some cases, for effective radiation of low frequencies in automotive speakers, it can be up to ±20 mm.

[0015] Typically, a portion of the cone and a portion of the surround are glued on top of each other. The glued area typically spans a radial distance of 3 mm to 4 mm for a firm and durable connection.

[0016] In this range, the specific mass of the diaphragm is often more than twice the sum of the specific mass of the cone, the specific mass of the surround, and the amount of glue. For a low moving mass design, this additional annular mass load is a relatively high cost and reduces the electroacoustic conversion efficiency of the speaker. Since the surround is generally more compliant than the speaker cone, the outer boundary conditions of the cone can be considered "free" as opposed to "hinged" or "clamped". This results in a low cone breakage, especially considering the above-mentioned additional mass in the overlapping area at the outer side of the cone and the moving part of the surround. The first cone breakage is characterized by a frequency response that reduces efficiency and a subsequent rough decline in the frequency response, which results in part-to-part variation and colored sound.

[0017] The normal speaker size diameter for AVAS applications is approximately 50 mm to 170 mm. The free air resonance frequency of such speakers is typically in the range of 50 Hz to 150 Hz. The cavity behind the speaker diaphragm increases the resonance frequency, but this increase depends on the pressure, temperature, and humidity of the enclosed air. For speakers intended for use outside the vehicle, these factors must not be ignored. Typically, an otherwise sealed speaker box is equipped with a slow response valve that allows for environmental pressure equalization by means of air exchange between the inside and outside of the box.

[0018] Therefore, due to the high compliance of the speaker suspension and the varying stiffness of the air volume, the rest position of the axial voice coil in the air gap is not as well-defined as one would assume based on the experience of classical in-vehicle speakers or even home audio speakers. The axial offset of the voice coil relative to the center of the air gap reduces efficiency and generates distortion.

[0019] Accordingly, there is a desire for a wideband loudspeaker having a smooth frequency response in a rated frequency range of 350 Hz to 3.5 kHz, a relatively low moving mass, and being able to withstand the front surface of the element and a low axial compliance suspension. SUMMARY OF THE INVENTION

[0020] The present inventors have found that by carefully controlling the materials and shapes of the components of a loudspeaker, desired performance can be obtained.

[0021] By law, the combined A-weighted SPL (sound pressure level) of a vehicle alarm system in the 1 / 3 octave frequency bands at 2 kHz, 2.5 kHz, and 3.15 kHz must be no less than 105 dB (measured at a distance of 2 m on the main axis of the device under anechoic conditions). See, for example, the provisions of Article 28 of the Economic Commission for Europe of the United Nations (UN / ECE) regulations: "Uniform provisions concerning the approval of audible warning devices and of motor vehicles with regard to their audible signals".

[0022] A high SPL in this region is a necessary but not sufficient condition for also recognizing the sound as that of an automobile horn. Traditional high-quality automobile horns come in pairs: each of the two horns is equipped with a hammer that strikes a metal disk to make it resonate. The hammer or disk itself moves in a fixed manner electromagnetically, since the frequency at which the hammer or disk moves is defined by electromechanical interruption processing. Direct current from a vehicle battery (e.g., a 12 V battery) is fed into a coil. The hammer moves towards the disk and vice versa. By moving forward, the contact with the battery is interrupted, and after hitting the disk, the contact is restored and the cycle starts again. The resonant disk radiates sound into a cavity that is open to the horn throat. The sound enters the horn throat, travels along the horn, and exits via the horn mouth to the outside world. The impedance matching of the well-known horn with the surrounding air results in high efficiency and increased gain of the harmonics of the resonant disk. The fundamental frequencies and overtones of the two horns are tuned differently, interleaving the spectra and resulting in an overall broadband output spectrum (see Figure 2 ).

[0023] Accordingly, there is a requirement for a loudspeaker designed to be used as an automobile horn that plays a horn-like sound from a sound library to output a sound with a high sound pressure level.

[0024] The present inventor has found that, in particular, even in speakers for external use (such as in an AVAS system), the piston-like movement of the diaphragm can be greatly maintained, and the desired sound profile is generated for this purpose. This is facilitated by using a specific surround (suspension) portion as described herein.

[0025] Such piston-like movement is schematically shown in Figure 1 (a). Here, the schematic shows a speaker diaphragm 3 moving between a first relaxed position (solid line) and a second actuated position (dashed line). This movement in the direction 5 along the movement axis 4 is piston-like because the diaphragm 3 moves "in phase": each part of the diaphragm 3 moves as close as possible the same amount as every other part of the diaphragm 3. This includes, for example, the dust cap 9. The surround 7 facilitates this movement; the properties of the surround and the diaphragm are the focus of the present invention.

[0026] This is in contrast to the movement shown in Figure 1 (b), Figure 1 (b) shows the movement observed for a more membranous speaker design. Here it can be seen (solid and dashed lines) that the membrane movement is not piston-like: the membrane flexes and bends between its relaxed and actuated positions, bending outwards during its movement.

[0027] A first aspect of the present invention relates to a speaker assembly for outdoor use and in particular for use outside a vehicle, the speaker assembly comprising: a speaker comprising a drive unit and a diaphragm, wherein the drive unit is configured to move the diaphragm along a movement axis, wherein the diaphragm has a front face facing a forward direction parallel to the movement axis and a back face facing a backward direction parallel to the movement axis; wherein the speaker assembly comprises a frame, and the diaphragm is suspended from the frame by at least one suspension; wherein at least one suspension comprises a surround located at the periphery of the diaphragm; and wherein the diaphragm and the surround are formed from a single-piece material comprising a single-layer woven fabric of orthogonally woven fibers and a thermosetting resin. In some embodiments, the longest dimension of the surround and diaphragm unit in a direction perpendicular to the movement axis is D_clamp and is in the range of 50 mm to 200 mm. In some preferred embodiments, the Young's modulus of the material of the diaphragm and the surround is in the range of 2 GPa to 15 GPa, or even 8 GPa to 15 GPa. In some preferred embodiments, the thickness of the material of the diaphragm and the surround is in the range of 0.03 mm to 1 mm, for example in the range of 0.03 mm to 0.6 mm.

[0028] Such a speaker assembly configuration allows for piston-like movement of the diaphragm and desired sound output.

[0029] The D_clamp corresponds to the longest dimension of the surround and the diaphragm unit in a direction perpendicular to the axis of movement. Specifically, the surround and the diaphragm can be formed monolithically with additional material that extends radially beyond the surround. Such material can be used to fix the diaphragm and the surround to, for example, a frame. This material is not included in the D_clamp. For example, in the case where the outer periphery of a substantially circular surround is to be fixed by circumferential clamping, the D_clamp extends across the diameter of the surround from one clamped edge to the other. The D_clamp does not include the clamped material and only includes the material that can move.

[0030] Therefore, the boundary condition of the outer edge of the surround can be said to be clamped.

[0031] The present invention provides speakers having a relatively large axial stiffness and a relatively low moving mass. This can result in them having a high resonance frequency. The typical value of the D_clamp in the range of 100 mm to 150 mm is within the octave of 400 Hz to 800 Hz.

[0032] Such a high resonance frequency is particularly useful in a special application as a HAVAS speaker: the resonance frequency can be tuned to the frequency range where the fundamental frequency of the horn is located (usually 400 Hz to 600 Hz), and the actual power at the speaker in this range is reduced due to the impedance peak around the resonance. Despite having a high resonance frequency, the output at lower frequencies such as the 315 Hz 1 / 3 octave band is still large due to the high speaker sensitivity (see Figure 4 ).

[0033] In the speaker of the present invention, even at 6V, the total harmonic distortion for low frequencies is still below 10% (see Figure 5 ).

[0034] This allows this speaker to be used not only as a vehicle warning horn but also as an AVAS speaker that must reproduce frequencies below its resonance frequency.

[0035] A speaker assembly for outdoor use is intended to refer to a speaker assembly suitable for (preferably configured for) at least a part of the speaker assembly to be exposed to the open air (i.e., not inside an enclosure, vehicle, or building), such as outside a vehicle.

[0036] Therefore, the frame can be in the form of a box that is acoustically sealed except for covering the speaker or diaphragm on one of its sides.

[0037] The thickness of the material of the diaphragm and the surround can be appropriately in the range of 0.03 mm to 0.6 mm, preferably in the range of 0.05 mm to 0.3 mm, and more preferably in the range of 0.1 mm to 0.2 mm.

[0038] It will be recognized that the thickness of the material corresponds to its minimum dimension, which can be broadly in a direction parallel to the axis of movement (depending on the shape).

[0039] It has also been found that the Young's modulus of the materials of the diaphragm and the surround is a relevant factor in optimizing the piston-like movement in combination with other factors considered herein. For the loudspeaker of the present invention, the Young's modulus of the materials of the diaphragm and the surround can suitably be in the range of 2 GPa to 15 GPa, preferably in the range of 8 GPa to 15 GPa and more preferably in the range of 10 GPa to 12 GPa. However, for many materials (e.g., when woven fibers are included), the Young's modulus can vary depending on the direction of measurement. Thus, in some embodiments, the material has the above Young's modulus in at least one direction; and in some embodiments, has the above Young's modulus in all directions.

[0040] In a woven material, the Young's modulus and the tensile strength of the diaphragm material for the loudspeaker of the present invention can be determined, for example, by measurements according to ISO 527-1 on cut samples of 30 mm x 5.3 mm rectangular dimensions from the manufactured diaphragm. A first sample is cut with the warp and weft aligned with the cutting direction, and a second sample is cut with the warp and weft at 45° to the cutting direction.

[0041] The Young's modulus of the first sample after cutting with the warp and weft parallel to the edges of the rectangular sample (i.e., the Young's modulus in the warp / weft direction) is preferably in the range of 2 GPa to 15 GPa, more preferably in the range of 3 GPa to 10 GPa, more preferably in the range of 3 GPa to 8 GPa. The ultimate tensile strength is suitably in the range of 75 MPa to 300 MPa, preferably in the range of 100 MPa to 250 MPa, more preferably in the range of 175 MPa to 225 MPa.

[0042] The Young's modulus of the second sample after cutting with the warp and weft at an angle of 45° to the edges of the rectangular sample (i.e., the Young's modulus at 45° to the warp / weft direction) is suitably in the range of 2 GPa to 10 GPa, preferably in the range of 3 GPa to 8 GPa. The ultimate tensile strength should be in the range of 50 MPa to 200 MPa, preferably in the range of 50 MPa to 75 MPa.

[0043] The elongation at break of any sample is suitably a strain not exceeding 40%, preferably not exceeding 20% and more preferably not exceeding 10%.

[0044] In addition, when subjected to Differential Scanning Calorimetry testing in accordance with ISO 1137-1, the most suitable materials are thermally stable in the temperature range of -40°C to 300°C and have a substantially flat DSC curve. Ideally, there should be no change in conditions indicating melting, crystallization, or glass transition.

[0045] When subjected to Dynamical Mechanical Analysis in accordance with ISO 6721-4, the storage modulus E' of any sample of a suitable material is suitably substantially stable in the temperature range of -40°C to 100°C. At room temperature, the storage modulus is suitably in the range of 2 GPa to 10 GPa, preferably in the range of 4 GPa to 6 GPa. The loss modulus E'' at room temperature suitably does not exceed 1 GPa, preferably does not exceed 500 MPa, and more preferably does not exceed 200 MPa.

[0046] Suitable materials for the diaphragm and the surround include materials comprising a single-layer woven fabric containing orthogonally interwoven fibers (such as glass fibers, carbon fibers, or Kevlar (poly-p-phenylene terephthalamide)) and a matrix or coating of a thermosetting resin (such as epoxy resin or phenolic resin).

[0047] In this woven fabric, the weaving pattern is preferably a cross cloth or twill, and the same yarn count can be suitably used for the warp and weft. The yarn count can be, for example, from 20 yarns per inch (tpi) to 100 yarns per inch (tpi), and preferably is 30 tpi to 60 tpi.

[0048] The materials for the diaphragm and the surround can suitably have a specific mass in the range of 50 g / m 2 to 500 g / m 2 and can preferably be in the range of 100 g / m 2 to 300 g / m 2 In addition, it can suitably have a bulk density in the range of 1.2 g / cm 3 to 1.8 g / cm 3 and preferably in the range of 1.4 g / cm 3 to 1.6 g / cm 3 These properties help to further provide a diaphragm and surround material that has sufficient stiffness to allow piston-like movement of the diaphragm (maintaining its shape during movement) and is flexible enough to allow the surround portion to facilitate such piston-like movement.

[0049]

[0050] ​It will be apparent that while the diaphragm and the surround are made of a single piece of material (i.e., are monolithic), there may be some manufacturing variations in the properties of the material across the diaphragm and the surround. Preferably, the material has a substantially uniform or homogeneous thickness and Young's modulus.

[0051] The diaphragm may have a dish shape. For example, the diaphragm may include a conical portion that is generally in the shape of an open cone and has a cone opening angle in the range of 60° to 160°. As an open cone, this means that the "tip" of the cone is missing. Thus, the cone opening angle is measured as the angle between the side walls of the conical portion. Preferably, the cone opening angle is in the range of 90° to 130°. It should be appreciated that preferably, these side walls of the conical portion are straight / flat; i.e., the cone angle does not change in the radial direction.

[0052] The conical portion may have a longest dimension in the range of 40 mm to 180 mm in a direction perpendicular to the movement axis D_cone.

[0053] The drive unit of the loudspeaker may include a voice coil positioned at the tip of the open cone of the conical portion. In the presence of such a voice coil, it may desirably have a longest dimension D_VC in a direction perpendicular to the movement axis, where D_VC is in the range of 18 mm to 50 mm and the ratio of D_clamp to D_VC is 2 or more. D_VC may preferably be in the range of 25 mm to 40 mm.

[0054] The diaphragm may have a shaped portion adapted to engage the voice coil. For example, in a conical diaphragm, there may be a shoulder or a dent at the position in the conical portion corresponding to where the voice coil will engage the diaphragm (generally, at D_VC). This shoulder or dent may be annular or another shape to match the voice coil (or at least the shape of the portion of the voice coil that will engage the diaphragm). This allows the voice coil to be more easily positioned and more easily adhered / bonded / connected to the diaphragm, as the shoulder / dent acts as a seating or guiding portion.

[0055] The diaphragm may further include a dust cap portion on the front face of the diaphragm that covers the tip of the open cone of the conical portion. In this case, the dust cap is made of the same material as the surround and the diaphragm and is generally monolithic with them, i.e., formed from the same single piece of material (and thus subject to the above preferences and characteristics of the material).

[0056] The surround may suitably include a corrugated portion extending around the periphery of the diaphragm; the center of the surround corrugated portion has a longest dimension D_d measured between points at the peaks in the forward direction of the corrugated portion in a direction perpendicular to the axis of motion, and the ratio of D_d to D_clamp is 0.8 or more. The corrugated portion may be convex (i.e., the edges of the corrugated portion are not as forward as the middle of the corrugated portion relative to the forward direction) or concave (i.e., the edges of the corrugated portion are more forward than the middle of the corrugated portion relative to the forward direction). Preferably, the corrugated portion is convex relative to the forward direction. The corrugated portion may preferably have a curved cross-section (in a cross-section parallel to the axis of motion), particularly a curve that is a segment of a circle, and is tangentially connected to a radially adjacent feature, such as the diaphragm here. That is, the connection of the corrugated portion to the diaphragm is at a point where the wall of the diaphragm (e.g., the side wall of the above-mentioned conical portion) is in a direction tangent to the theoretical circle of which the curved corrugated portion is a segment of the circle. This provides a smooth transition between the corrugated portion and the diaphragm.

[0057] In Figure 3 a corresponding to D_clamp, D_d, D_cone, and D_VC are schematically shown in one embodiment.

[0058] During operation at low and medium frequencies (e.g., 2 kHz), according to (https: / / www.klippel.de / fileadmin / klippel / Files / Know_How / Application_Notes / AN_32_Effective_Radiation_Area.pdf), the movement of the membrane within a range up to diameter D_d and S_d can be substantially regarded as the movement of a piston. The speaker parameter S_d is calculated from the diameter D_d. The ratio of D_d to D_clamp is not less than 0.8.

[0059] In some embodiments, the surround may include a plurality of such corrugated portions. For example, it may include at least a first corrugated portion and a second corrugated portion extending around the periphery of the diaphragm, where the first corrugated portion is radially outside the second corrugated portion. The first corrugated portion may preferably be convex relative to the forward direction, and the second corrugated portion may preferably be concave relative to the forward direction.

[0060] Of course, it is conceivable that there are more than two corrugated portions. Each can independently be convex or concave relative to the forward direction. Preferably, there is a convex corrugated portion at the radial end of the surround. Preferably, the corrugated portions alternate between convex and concave.

[0061] Each can also independently have a curved cross-section (in a cross-section parallel to the axis of movement), in particular a curve that is a segment of a circle, and is tangentially connected to a radially adjacent feature, whether that feature is the diaphragm or another corrugation. That is, the connection of the corrugation to the adjacent feature is at a point where the wall of the diaphragm (such as the side wall of the aforementioned conical portion) or the curve of the adjacent corrugation is tangent to the theoretical circle of which this corrugation is a segment of the circle. This provides a smooth transition between the corrugations and between the innermost corrugation and the diaphragm.

[0062] It should be recognized that the transition between the outermost corrugation and any feature radially outside it does not need to have such a relationship and thus does not have to be "smooth" in this way.

[0063] For example, a third corrugation may be present between the aforementioned second corrugation and the diaphragm. That is to say, the surround may include at least a first corrugation, a second corrugation, and a third corrugation, each of which extends around the perimeter of the diaphragm, where the first corrugation is positioned radially outside the second corrugation and the second corrugation is positioned radially outside the third corrugation. The first corrugation may preferably be convex with respect to the forward direction, the second corrugation may preferably be concave with respect to the forward direction, and the third corrugation may preferably be convex with respect to the forward direction.

[0064] Such corrugations in the surround allow the diaphragm to move axially along the axis of movement. By the present invention, this movement can be piston-like (i.e., piston-type), such that each part of the diaphragm moves in phase (i.e., moves the same amount along the axis of movement as every other part of the diaphragm; see Figure 1 (a)).

[0065] The loudspeaker assembly (e.g., the diaphragm, the surround, and the driver) can be configured such that when the loudspeaker assembly is in use, the movement of the diaphragm along the axis of movement is relatively small. For example, the maximum displacement of the diaphragm (from one extreme to the other) can be at most 2 mm. For example, this can be ± at most 1 mm from the rest position of the diaphragm, more preferably ± at most 0.5 mm.

[0066] In some embodiments, the surround may include a mounting portion at the perimeter of the surround, where the surround is attached to the frame via the mounting portion. The mounting portion can be a flat annular portion around the perimeter of the surround. Generally, it is formed as a single-piece component of the surround. It can be attached to the frame by means such as adhesion, or physically / mechanically held in place by a fixing member, for example, by placing the mounting portion between the fixing member and the frame.

[0067] Alternatively, the surround and thus the loudspeaker can be held in place within the frame by the presence of one or more fixing (e.g., adhesive) members located between the surround and the frame. That is, the loudspeaker can include a fixing member positioned between the surround and the frame and sized to hold the loudspeaker fixed and retained within the frame. The fixing member is sandwiched between the frame and the surround in this way. The fixing member contacts the surround and the frame, allowing the desired movement of the diaphragm. Such an arrangement can be preferred over the flat annular mounting portion described above because for a given D_clamp, the loudspeaker assembly can be made smaller; that is, a larger diaphragm can be fitted within a given frame size.

[0068] Due to the fixing member, typically the outer boundary condition of the surround is "clamped"; that is, its movement is not permitted. This means that the breakup region occurs above the rated frequency range and results in a smooth response within the rated frequency range.

[0069] This breakup region is well known in the art; it occurs where the main piston-like movement of the diaphragm breaks up. At low frequencies, there are other modes that are excited and superimposed on top of the forced axial motion. However, these modes are circumferential, so similar-sized portions of the cone move more and others move less, and the resulting sound pressure level is hardly affected. However, the radial modal behavior has a strong influence on the radiated sound pressure level because the regions of increased or decreased motion are not uniform in size. This results in dips and subsequent peaks in the frequency response - this is the breakup. The radial modal behavior is determined by the material and shape but also by the boundary conditions.

[0070] Viewed in the direction along the axis of motion, looking towards the front of the diaphragm, the loudspeaker assembly can be circular. In particular, the shape of the surround can be circular; the shape of the perimeter of the diaphragm can also be circular.

[0071] In this case, D_clamp, D_VC, D_cone, and D_d each correspond to the diameter of the relevant circle.

[0072] To make the loudspeaker assembly more suitable for outdoor use, it can also include a grille positioned in front of the front of the diaphragm, with the back of the grille facing towards the front of the diaphragm in a rearward direction and the front of the grille facing in a forward direction; wherein the grille is configured to allow the sound generated by the front of the diaphragm to pass through the grille when the loudspeaker is in use and to inhibit the ingress of water incident on the front of the grille from penetrating into the space enclosed between the back of the grille and the front of the diaphragm.

[0073] The loudspeaker assembly may preferably be configured for use in a road vehicle where the front side of the grille is exposed to the outdoor environment. It may form part of an Acoustic Vehicle Alerting System (AVAS) or an audible warning device (horn).

[0074] The present invention includes combinations of the described aspects and preferred features, unless such combinations are clearly impermissible or should be explicitly avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Embodiments and experiments illustrating the principles of the present invention will now be discussed with reference to the accompanying drawings, in which:

[0076] Figure 1 Illustrated are (a) the piston-like movement of a relaxed (solid line) and actuated (dashed line) conical diaphragm; and (b) the non-piston-like and non-uniform movement of a relaxed (solid line) and actuated (dashed line) flat diaphragm.

[0077] Figure 2 Illustrated is the output spectrum of a conventional two-horn vehicle alerting system.

[0078] Figure 3 Illustrated is a schematic cross-sectional view of the loudspeaker assembly of the present invention, in which various longest dimensions mentioned herein are marked.

[0079] Figure 4 Illustrated is an example output spectrum of the loudspeaker assembly of the present invention at 2V on-axis in an infinite baffle without a grille.

[0080] Figure 5 Illustrated is an example output spectrum of the loudspeaker assembly of the present invention at 8.5V on-axis in an infinite baffle with a grille.

[0081] Figure 6 Illustrated is an example output spectrum of the loudspeaker assembly of the present invention at 2V on-axis in an infinite baffle without a grille.

[0082] Figure 7 Illustrated is a schematic cross-sectional view of a first loudspeaker assembly according to the present invention.

[0083] Figure 8 Illustrated is a schematic cross-sectional view of a second loudspeaker assembly according to the present invention.

[0084] Figure 9 Illustrated is a schematic cross-sectional view of a third loudspeaker assembly according to the present invention. DETAILED DESCRIPTION

[0085] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying drawings. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0086] Figure 1 The general concept of the present invention is schematically shown. Figure 1 (b) shows a simple membrane formed of a homogeneous material (solid line) that moves to the dashed position when actuated. The membrane bends, changes shape and affects its response. These are adverse speaker behaviors.

[0087] On the other hand, Figure 1 (a) shows the speaker movement achieved by the present invention. The speaker assembly 1 is schematically shown. Here, the part corresponding to the homogeneous membrane is a diaphragm 3 that is widely conical (open cone) in shape, which is bounded by a surround 7 and has a dust cap 9 integrally formed at its center. The dust cap prevents substances such as dust and particles from entering the voice coil former and entering the voice coil area.

[0088] The circumferential position of components relative to the diaphragm is mentioned below; of course, this may imply that the term is only applicable when the diaphragm is frustum-shaped. This is not the case. It should be understood that the diaphragm can have different shapes such that its perimeter is not circular. In that case, those skilled in the art will recognize that "circumferential" refers to the outer perimeter of the diaphragm; the outer circumferential direction is from the center of the diaphragm towards the outside, regardless of its perimeter shape.

[0089] Similarly, in cases where components are described as annular, it should be understood that in cases where the diaphragm has a different shape, those components will not be annular but will have a shape that matches the perimeter of the diaphragm.

[0090] When actuated by the drive unit 2 including the voice coil 8, the diaphragm and the dust cap move together and in phase to the dashed position: this is the piston-like movement as described herein. Here, the surround 7 including the corrugation 10 (the bent portion of the diaphragm material that connects the diaphragm components to the flat annular mounting portion 15) flexes to allow this piston-like movement. The surround is part of the suspension 6 that widely connects the diaphragm 3 to the frame ( Figure 1 (not shown in (a); subsequently denoted by the number 14).

[0091] The piston-like movement occurs on the movement axis 4, where actuation of the voice coil and thus the diaphragm 3 causes it to move in the direction herein referred to as the forward direction (indicated by the arrow 5). Of course, it should be understood that during actuation, there will be some slight non-linearity or deviation in the movement of the diaphragm; the axis 4 and the direction 5 only indicate the main movement.

[0092] It can be seen that at the point where the voice coil 8 contacts the diaphragm 3, there is an annular notch / ridge 17 in the shape of the diaphragm. This is located between the diaphragm 3 and the dust cap 9. It allows for easier placement and positioning of the voice coil 8 during the manufacturing process.

[0093] Figures 7 to 9 Other embodiments of the loudspeaker according to the present invention are shown. Parts similar to those Figure 1 shown therein are given the same reference numerals.

[0094] Figure 7 An embodiment is shown in which the suspension 6 again includes a surround 7 having a corrugated portion 10, the surround 7 being attached to the frame 14 by a mounting portion 15 which is formed as a flat annular portion circumferentially located outside the corrugated portion 10. The corrugated portion 10 is a bent portion of the material which effectively protrudes with respect to the Figure 1 forward direction 5 shown therein; that is, the bent extension extends in the forward direction 5.

[0095] The mounting portion 15 can be adhered, for example, to a ridge or platform portion of the frame 14 by bonding. Alternatively, it can be fastened between the ridge / platform portion 18 of the unit and the cover 19. Such mechanical clamping can be used in combination with bonding to fix the mounting portion 15 and thus the surround 7.

[0096] The cover 19 can include a grille 16 for protecting the loudspeaker assembly, for example to prevent moisture from penetrating to allow for outdoor use.

[0097] In this embodiment, the voice coil 8 is suspended by a spider 20 which holds the voice coil within the frame. For effective operation, there is no contact between the voice coil and the frame. The spider has sufficient elasticity to hold the voice coil by withstanding the forces generated when current flows through the voice coil. The spider also suspends the voice coil former and prevents it from contacting any other part of the loudspeaker when it vibrates, or from contacting any part of the loudspeaker when it is not vibrating.

[0098] As described above, the diaphragm 3 can be attached to the frame 14 by a first mechanical clamp formed by the ridges or platform members 18 of the frame 14 and the corresponding lips of the cover 19. To ensure that the connection between the diaphragm and the frame is flexible while being firmly attached to the frame, a suspension 6 with a surround 7 is provided to link the diaphragm 3 to the mounting portion 15. This is attached to the diaphragm 3 at the inner end of the suspension 6 and to the mounting portion 15 at the outer end; the mounting portion 15 is held by the first mechanical clamp at its own outer end. This results in a clamped boundary condition. The mounting portion 15, the surround 7, and the diaphragm 3 are all integrally formed from a single piece of material. The surround 7 can be presented as a corrugated portion or a bent portion 10 at the outer perimeter of the diaphragm portion 3; the mounting portion 15 can be presented as an annular flange at the outer perimeter of the surround portion 7.

[0099] The properties of this material are discussed in detail herein. The material must have a certain thickness and Young's modulus, while the diaphragm has certain dimensions to give the desired motion and thus the desired acoustic response characteristics. For example, in the Figure 7 embodiment shown as in, the material used can be a fiberglass / epoxy composite with a thickness of 0.08 mm.

[0100] In the illustrated embodiment, the motor or drive system 2 uses an annular magnet 21 to provide a magnetic field for the movement of the voice coil 8; the magnet system is connected to the rear of the frame 14 through a yoke 22. The centering washer is connected to the "washer" portion 23 of the magnet system. It should be recognized that such a drive system can be applied to various different diaphragm / suspension / frame designs and configurations in addition to those Figure 7 shown in.

[0101] The same is true for the grille 16 shown as part of the cover 19. As shown, the grille follows the shape of the diaphragm and thus has the shape of a frustum (truncated cone). It has a flat portion corresponding to the position of the dust cover 9 and an inclined portion corresponding to the position of the diaphragm 3. The grille 16 protects the diaphragm 3 and other internal components from environmental factors; here, there is no "line of sight" that can pass through the grille from the outside to reach the diaphragm. By presenting such a "tortuous path" for water droplets and the like, the grille provides effective protection against water or debris.

[0102] Conversely, Figure 8 the grille shown in spans flatly across the "top" of the frame 14. In this embodiment, the suspension 6 has a surround 7 including three corrugated portions 11, 12, and 13, instead of Figure 7The single corrugated portion 10 shown in []. The arrangement is characterized by a corrugated portion 13 that is circumferentially located outside the diaphragm 3; the corrugated portion is "convex", curving outward from the frame towards the forward direction 5 (not shown). The next corrugated portion 12 is circumferentially located outside the corrugated portion 13; it is convex and curves inward away from the forward direction 5 towards the frame. This is followed by a further corrugated portion 11 in the circumferentially outward direction, which is again convex. Outside of it is the mounting portion 15, and the flange portion is equivalent to the flange portion previously shown and described.

[0103] Such a suspension arrangement can provide further flexibility for the surround 7; this can mean that different material properties can be utilized.

[0104] It can be seen that the dust cap 9 in this embodiment is "inverted" compared to the Figure 7 dust cap shown in []. That is, instead of being convex and extending into the cone of the diaphragm, it is concave, bounded by a partition wall, and extends from this partition wall on the circumferentially inner side. The engagement between the surrounding wall and the diaphragm 3 provides a portion 17 in the form of an annular notch or ridge in which the voice coil 8 can be seated.

[0105] The drive system 2 shown in this embodiment uses a disc magnet 24. It is mounted to the frame 14; in this example, the frame 14 itself is mounted to the rear part 25 forming the chamber (like the centering washer 20). The rear part 25 can be attached to the frame by any means (such as adhesion or mechanical bonding, such as screw fasteners).

[0106] Figure 9 A third exemplary embodiment is shown in []. The drive system here can be analogous to the Figure 8 drive system in which the disc magnet 24 is mounted within the frame 14 (there is no rear part 25 in this embodiment). This is fixed to the rear wall of the frame 14; there is no centering washer in this embodiment.

[0107] The dust cap 9 is as shown and explained for the Figure 7 shown; there is a similar notch 17 for seating the voice coil 8.

[0108] The grille 16 in this embodiment is configured to enhance a specific frequency range.

[0109] In this embodiment, the attachment of the surround 7 (with the corrugated portion 10) to the frame 14 is different. No mounting portion 15 is provided here. Instead, the outer portion of the corrugated portion 10 is "wedged" into the frame 14. One or more fixing members 15 are clamped between the corrugated portion 10 (i.e., the surround 7) and the inner wall of the frame 14. The dimensions of these fixing members are determined to prevent the movement of the outermost edge of the surround 7; thus, the clamped boundary conditions are given again. The (one or more) fixing members can be formed of solid material or they can be adhesive themselves to adhere the surround in place. There can be a single fixing member 15 extending around the entire perimeter of the surround 7; alternatively, for example, there can be four such members 15 positioned around the perimeter. Ideally, a single fixing member extends around the entire perimeter to provide the best mechanical clamping.

[0110] In this embodiment, the materials of the diaphragm, surround, and dust cap are glass fibers coated with epoxy resin with a thickness of 0.15 mm.

[0111] To test the response of this loudspeaker, generate Figure 4 , Figure 5 and Figure 6 the output spectra shown in.

[0112] Figure 4 Shows the example frequency response of the loudspeaker assembly according to the present invention without a grille, at 2V on the axis in an infinite baffle, the loudspeaker assembly having a diaphragm, surround, and dust cap formed of a 0.15 mm thick material made of glass fiber and epoxy resin. It can be seen that despite the high resonance frequency of the loudspeaker of the present invention, due to the high loudspeaker sensitivity, the output at lower frequencies such as the 315 Hz 1 / 3 octave band is still large (about 87 dB).

[0113] Figure 5 Shows the example frequency response, as well as the second-order and third-order distortion components, of the loudspeaker assembly according to the present invention with a grille, at 8.5V on the axis in an infinite baffle, the loudspeaker assembly having a diaphragm, surround, and dust cap formed of a 0.15 mm thick material made of glass fiber and epoxy resin. These figures show that even at 8.5V, the harmonic distortion remains moderate for low frequencies.

[0114] This allows this loudspeaker to be used not only as a vehicle warning horn but also as an AVAS loudspeaker that must reproduce frequencies below its resonance frequency.

[0115] Figure 6Shows an example frequency response of a loudspeaker assembly according to the present invention at 2V on axis in an infinite baffle without a grille, the loudspeaker assembly having a diaphragm, surround, and dust cap formed from a 0.08 mm thick material made of Kevlar impregnated in phenolic resin. Although the membrane material is very thin, the frequency response is substantially smooth in the range from 500 Hz to 5 kHz.

[0116] Clause 1. A loudspeaker assembly (1) for use outside a vehicle, the loudspeaker assembly comprising:

[0117] A loudspeaker including a drive unit (2) and a diaphragm (3), wherein the drive unit (2) is configured to move the diaphragm (3) along a movement axis (4), wherein the diaphragm (3) has a front face facing a forward direction (5) parallel to the movement axis and a back face facing a backward direction parallel to the movement axis;

[0118] Wherein the loudspeaker assembly (1) includes a frame (14), and the diaphragm (3) is suspended from the frame (14) by at least one suspension (6);

[0119] Wherein the at least one suspension (6) includes a surround (7) located at the periphery of the diaphragm (3); and

[0120] Wherein the diaphragm (3) and the surround (7) are formed from a single piece of material, the material including a single layer woven fabric of orthogonally woven fibers and a thermosetting resin.

[0121] Clause 2. The loudspeaker assembly (1) according to Clause 1, wherein a longest dimension of the surround (7) and diaphragm (3) unit in a direction perpendicular to the movement axis (4) is D_clamp and is in the range of 50 mm to 200 mm.

[0122] Clause 3. The loudspeaker assembly (1) according to Clause 1 or Clause 2, wherein the material of the diaphragm (3) and the surround (7) has a Young's modulus in the range of 2 GPa to 15 GPa in the warp / weft direction and a Young's modulus in the range of 2 GPa to 10 GPa at 45° relative to the warp / weft direction;

[0123] And wherein the thickness of the material of the diaphragm (3) and the surround (7) is in the range of 0.03 mm to 1 mm.

[0124] Clause 4. The loudspeaker assembly (1) according to any one of the preceding clauses, wherein the materials of the diaphragm (3) and the surround (7) have a tensile strength in the range of 75 MPa to 300 MPa in the warp / weft direction, and a tensile strength in the range of 50 MPa to 200 MPa at 45° relative to the warp / weft direction.

[0125] Clause 5. The loudspeaker assembly (1) according to any one of the preceding clauses, wherein the diaphragm (3) includes a conical portion that is generally in the shape of an open cone and has a cone opening angle in the range of 60° to 160°.

[0126] Clause 6. The loudspeaker assembly (1) according to Clause 5, wherein the drive unit (2) includes a voice coil (8) that is located at the tip of the open cone of the conical portion and has a longest dimension D_VC in a direction perpendicular to the movement axis (4), where D_VC is in the range of 18 mm to 50 mm and the ratio of D_clamp to D_VC is 2 or more.

[0127] Clause 7. The loudspeaker assembly (1) according to Clause 6, wherein the diaphragm (3) has a shaped portion adapted to engage with the voice coil (8).

[0128] Clause 8. The loudspeaker assembly (1) according to Clause 5, 6 or 7, wherein the diaphragm (3) further includes a dust cap portion (9) on the front surface of the diaphragm (3), and the dust cap portion (9) covers the tip of the open cone of the conical portion.

[0129] Clause 9. The loudspeaker assembly (1) according to any one of the preceding clauses, wherein the surround (7) includes a corrugated portion (10) that extends around the perimeter of the diaphragm (3); the surround (7) has a longest dimension D_d measured between points at the peaks of the corrugated portion (10) in the forward (5) direction in a direction perpendicular to the movement axis (4), and the ratio of D_d to D_clamp is 0.8 or more.

[0130] Clause 10. The loudspeaker according to Clause 9, wherein the corrugated portion (10) has a curved cross-section in a cross-section parallel to the movement axis, and the curve is a segment of a circle; the corrugated portion (10) is tangentially connected to the diaphragm.

[0131] Clause 11. The loudspeaker assembly (1) according to Clause 9 or Clause 10, wherein the surround (7) comprises at least a first corrugated portion (11), a second corrugated portion (12) and a third corrugated portion (13), each of the first corrugated portion (11), the second corrugated portion (12) and the third corrugated portion (13) extending around the periphery of the diaphragm (3), wherein the first corrugated portion (11) is located radially outside the second corrugated portion (12), and the second corrugated portion (12) is located radially outside the third corrugated portion (13).

[0132] Clause 12. The loudspeaker assembly (1) according to any one of the preceding clauses, wherein the surround (7) comprises a mounting portion (15) located at the periphery of the surround (7), wherein the surround (7) is attached to the frame (14) via the mounting portion (15).

[0133] Clause 13. The loudspeaker assembly (1) according to any one of Clauses 1 to 11, comprising a fixing member (16) positioned between the surround (7) and the frame (14) and dimensioned to fix the loudspeaker within the frame (14).

[0134] Clause 14. The loudspeaker assembly (1) according to any one of the preceding clauses, further comprising a grille (16) positioned in front of the front face of the diaphragm (3), the back face of the grille (16) facing the front face of the diaphragm (3) in the backward direction, and the front face of the grille (16) facing the forward direction (5);

[0135] wherein the grille (16) is configured to allow sound generated by the front face of the diaphragm (3) to pass through the grille (16) when the loudspeaker is in use, and to inhibit the ingress of water incident on the front face of the grille (16) from penetrating into the space enclosed between the back face of the grille (16) and the front face of the diaphragm (3).

[0136] Clause 15. The loudspeaker assembly (1) according to any one of the preceding clauses, the loudspeaker assembly (1) being configured for use in a road vehicle in which the front face of the grille (16) is exposed to an outdoor environment.

[0137] Clause 16. An acoustic vehicle alarm system (AVAS) comprising the loudspeaker assembly (1) according to any one of the preceding clauses.

[0138] Clause 17. An audible warning device comprising the loudspeaker assembly (1) according to any one of the preceding clauses.

[0139] ***

[0140] Features disclosed in the foregoing description, the following claims or the drawings (expressed in their specific forms or in terms of devices for performing the disclosed functions or methods or processes for obtaining the disclosed results) may, where appropriate, be used alone or in any combination of these features to implement the present invention in its different forms.

[0141] Although the present invention has been described in connection with the above exemplary embodiments, many equivalent modifications and variations will be apparent to those skilled in the art when the present disclosure is given. Accordingly, the above exemplary embodiments of the present invention are considered illustrative rather than restrictive. Various changes may be made to the embodiments without departing from the spirit and scope of the present invention.

[0142] For the avoidance of any doubt, any theoretical explanations provided herein are provided to enhance the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations.

[0143] Any section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described.

[0144] Throughout the specification (including the following claims), unless the context requires otherwise, the words "comprise", "include" and variations such as "comprises", "includes" and "including" shall be understood to imply the inclusion of the stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0145] It must be noted that, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" used in this specification and the appended claims include plural referents. Ranges may be expressed herein as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, another embodiment includes from one particular value and / or to another particular value. Similarly, when values are expressed as approximations by use of the antecedent "about", it will be understood that the particular value forms another embodiment. The term "about" associated with a numerical value is optional and means, for example, + / - 10%.

Claims

1. A loudspeaker assembly for use outside a vehicle, the loudspeaker assembly comprising: A loudspeaker including a drive unit and a diaphragm, wherein the drive unit is configured to move the diaphragm along a movement axis, and wherein the diaphragm has a front side facing a forward direction parallel to the movement axis and a back side facing a backward direction parallel to the movement axis; Wherein the loudspeaker assembly includes a frame, and the diaphragm is suspended from the frame by at least one suspension; Wherein the diaphragm includes a conical portion that is generally in the shape of an open cone and has a cone opening angle in the range of 90° to 130°; Wherein the at least one suspension includes a surround located at the periphery of the diaphragm, and wherein the surround includes a single corrugation extending around the periphery of the diaphragm, and wherein the single corrugation is convex with respect to the forward direction, and wherein the corrugation has a curved cross-section in a cross-section parallel to the movement axis, and the corrugation is tangentially connected to the conical portion of the diaphragm; and Wherein the diaphragm and the surround are formed of a single piece of material, and the material has a Young's modulus in the range of 2 GPa to 15 GPa measured in at least one direction; Wherein the drive unit includes a voice coil that has a longest dimension D_VC in a direction perpendicular to the movement axis, and D_VC is in the range of 18 mm to 50 mm, and wherein the surround and the diaphragm have a longest dimension D_clamp in a direction perpendicular to the movement axis, and the ratio of D_clamp to D_VC is 2 or more.

2. The loudspeaker assembly according to claim 1, wherein, The material of the diaphragm and the surround has a Young's modulus in the range of 10 GPa to 12 GPa measured in at least one direction.

3. The loudspeaker assembly according to claim 1, wherein, The surround and the diaphragm unit have a longest dimension D_clamp in a direction perpendicular to the movement axis, and D_clamp is in the range of 50 mm to 200 mm.

4. The loudspeaker assembly according to claim 1, wherein The loudspeaker has a resonance frequency between 400 Hz and 800 Hz.

5. The loudspeaker assembly according to claim 1, wherein, The voice coil is located at the tip of the open cone of the conical portion.

6. The loudspeaker assembly according to claim 5, wherein, The diaphragm has a shaped portion adapted to engage with the voice coil.

7. The loudspeaker assembly according to claim 6, wherein, The shaped portion is a shoulder or a dent.

8. The loudspeaker assembly according to claim 7, wherein, The voice coil is attached to a radially outward facing portion of the shoulder or the dent.

9. The loudspeaker assembly according to any one of claims 1 to 7, wherein, The materials of the diaphragm and the surround have a specific mass in the range of 100 g / m 2 to 300 g / m 2 .

10. The loudspeaker assembly according to any one of claims 1 to 7, wherein, The materials of the diaphragm and the surrounding object have a bulk density in the range of 1.4 g / cm 3 to 1.6 g / cm 3 .

11. The loudspeaker assembly according to any one of claims 1 to 7, wherein, The thickness of the material of the diaphragm and the surround is in the range of 0.05 mm to 0.3 mm.

12. The loudspeaker assembly according to any one of claims 1 to 7, wherein, The surround and the diaphragm unit have a longest dimension D_clamp in a direction perpendicular to the movement axis, and the surround has a longest dimension D_d measured between points at the peak of the corrugation in the forward direction in a direction perpendicular to the movement axis, and the ratio of D_d to D_clamp is 0.8 or more.

13. The loudspeaker assembly according to any one of claims 1 to 7, wherein, The diaphragm further includes a dust cap portion on the front side of the diaphragm, and the dust cap portion covers the tip of the open cone of the conical portion.

14. The loudspeaker assembly according to claim 13, wherein, The diaphragm, the surround, and the dust cap are formed of the single piece of material.

15. The loudspeaker assembly according to any one of claims 1 to 7, wherein, The conical portion has a longest dimension D_cone in a direction perpendicular to the axis of movement in the range of 40 mm to 180 mm.

16. The loudspeaker according to any one of claims 1 to 7, wherein, The curved cross-section of the single corrugation portion includes a circular segment.

17. The loudspeaker assembly according to any one of claims 1 to 7, wherein, The surround includes a mounting portion located at the periphery of the surround, wherein the surround is attached to the frame via the mounting portion.

18. The loudspeaker assembly according to any one of claims 1 to 7, comprising a fixing member positioned between the surround and the frame and dimensioned to fix the loudspeaker within the frame.

19. The loudspeaker assembly according to any one of claims 1 to 7, further comprising a grille positioned in front of the front face of the diaphragm, the back face of the grille facing the front face of the diaphragm in the backward direction, and the front face of the grille facing the forward direction; Among them, The grille is configured to allow sound generated by the front face of the diaphragm to pass through the grille when the loudspeaker is in use and to inhibit the ingress of water incident on the front face of the grille from penetrating into the space enclosed between the back face of the grille and the front face of the diaphragm.

20. The loudspeaker assembly according to any one of claims 1 to 7, the loudspeaker assembly being configured for use in a road vehicle where the front face of the grille is exposed to an outdoor environment.

21. The loudspeaker assembly according to any one of claims 1 to 7, wherein, The loudspeaker assembly is configured to produce an A-weighted sound pressure level of not less than 105 dB in the 1 / 3 octave frequency bands of 2 kHz, 2.5 kHz and 3.15 kHz, the A-weighted sound pressure level being measured at a distance of 2 m on the main axis of the loudspeaker assembly under anechoic conditions.

22. An acoustic vehicle alert system (AVAS) comprising a loudspeaker assembly according to any one of claims 1 to 21.

23. An audible warning device comprising a loudspeaker assembly according to any one of claims 1 to 21.

Images