Loudspeaker assembly

Abstract

A loudspeaker assembly configured to be mounted to a vehicle. The loudspeaker assembly includes: a loudspeaker, including 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 that faces in a forwards direction parallel to the movement axis and a rear face that faces in a rearwards direction parallel to the movement axis, wherein the loudspeaker has a front face that faces in the forwards direction and includes the front face of the diaphragm; and a grille, positioned in front of the front face of the loudspeaker, with a rear face of the grille facing in the rearwards direction toward the front face of the loudspeaker, and with a front face of the grille facing in the forwards direction, wherein the front face of the grille is configured to face downwards and be exposed to an outdoor environment when the loudspeaker assembly is mounted to the vehicle. The grille includes openings which extend from the rear face of the grille to the front face of the grille, wherein the openings are configured to permit sound to pass from the rear face of the grille to the front face of the grille, and to inhibit the ingress of water incident on the front face of the grille from entering into a space enclosed between the rear face of the grille and the front face of the loudspeaker when the loudspeaker assembly is in use. The rear face of the grille includes a sloped region which extends circumferentially around the movement axis, wherein the sloped region, when viewed in cross section in a plane parallel to the movement axis, slopes from a rearwardmost extent of the sloped region to a forwardmost extent of the sloped region with respect to the movement axis. The openings include slots formed in the sloped region, wherein each slot in the sloped region, when viewed in cross section in a plane parallel to the movement axis, extends from a first location positioned towards the rearwardmost extent of the sloped region to a second location positioned at the forwardmost extent of the sloped region so as to facilitate drainage of water from the rear face of the grille when the loudspeaker assembly is mounted to the vehicle.

Description

[0001] LOUDSPEAKER ASSEMBLY

[0002] This application claims priority to GB2410750.0, filed 23 July 2024.

[0003] Field of the Invention

[0004] The present invention relates to a loudspeaker assembly configured to be mounted to a vehicle.

[0005] Background

[0006] WO2022 / 189546A1 discloses a loudspeaker assembly suitable for use in a vehicle, the loudspeaker assembly including a loudspeaker and a grille. A front face of the grille is configured to be exposed to an outdoor environment. This document describes various loudspeaker assembly features which help to boost the sound pressure level (“SPL”) produced by the loudspeaker assembly in frequencies of interest for an acoustic vehicle alerting system (“AVAS”).

[0007] WO2022 / 253924A1 discloses another loudspeaker assembly suitable for use in a vehicle, the loudspeaker assembly including a loudspeaker and a grille. In this disclosure, the loudspeaker has a diaphragm and surround formed of a single piece of material.

[0008] WO2024 / 115672A1 discloses another loudspeaker assembly suitable for use in a vehicle, the loudspeaker assembly including a loudspeaker and a grille. In this disclosure, the loudspeaker again has a diaphragm and surround formed of a single piece of material and is further configured to be used as part of a horn apparatus.

[0009] A purpose of a grille in loudspeaker assemblies as described above is to inhibit the ingress of water incident on the front face of the grille from entering into a space enclosed between the rear face of the grille and the front face of the loudspeaker when the loudspeaker assembly is in use in a vehicle such as a car. However, when cars drive in wet conditions, e.g. in heavy rain and / or with a car wading through water, it is likely that water will enter a space between the grille and the loudspeaker. When this happens, it is generally desirable for water to drain from this space, to allow for normal operation of the loudspeaker assembly.

[0010] The present invention has been devised in light of the above considerations.

[0011] EP4379710A1 discloses another loudspeaker assembly suitable for use in a vehicle, the loudspeaker assembly including a loudspeaker and a grille. In this disclosure, a different form of grille is used.

[0012] Summary of the Invention

[0013] The loudspeaker assemblies of WO2022 / 189546A1 , WO2022 / 253924A1 and WO2024 / 115672A1 are all suitable for use in cars, e.g. in a position such as that shown in Figure 1 herein. When cars drive in wet conditions, e.g. in heavy rain and / or with a car wading through water, it has been observed by the inventors that significant amounts of water can enter a space between the grille and the loudspeaker. The inventors have further observed that for a grille with circular slots 50 as shown in Figures 2A and 2B herein (which implement a similar design to that taught by Figure. 4A of WO2022 / 189546A1), water drains less than ideally from the space between the grille and the loudspeaker, once water has entered this space. Without wishing to be bound by theory, it is believed by the inventors that this is because of capillary action of the water within the narrow circular slots 50 having an acoustical width of ~2mm (see below for a definition of “acoustical width”) meaning that the water is unable to drop out from the circular slots 50 under the effect of gravity, which causes the slots 50 to become blocked. This blocking of the circular slots 50 in turn inhibits performance of the loudspeaker assembly (by blocking sound generated by the loudspeaker). In practice, the inventors have found that air movement caused by the loudspeaker generating sound is not enough to clear the blocked circular slots and that, a car incorporating the grille of Figures. 2A and 2B needs to be moving at 50km / h or more to unblock the slots 50 (the reason for the slots becoming unblocked at such speeds is not known, but it is thought this could be because of pressure difference caused by movement at such speeds and / or by shaking of the car at such speeds).

[0014] Tests show that water blocking the slots in this way can cause losses of around 10dB on the SPL of the horn sound produced by the loudspeaker assembly.

[0015] The present inventors considered addressing this problem by widening the narrow circular slots of the grille design of Figures. 2A and 2B. The present inventors found that widening the slots to have an acoustical width of 6mm (with a grille made of polypropylene) was able to achieve better drainage. However, wider slots along these lines created other problems of allowing stones, and larger particles to enter the grille. Moreover, WO2022 / 189546A1 teaches that a relatively narrow slots (relatively high values of A1 / A3, to use the terminology of WO2022 / 189546A1) helps to benefit the acoustic transfer function (ATF) of the loudspeaker assembly. For these reasons, the inventors have found it preferable in practice to retain narrow circular slots with the grille design of Figures. 2A and 2B (“narrow” here meaning an acoustical width of 1 mm-5mm, preferably ~2mm), even though this results in inhibited SPL performance in wet conditions.

[0016] The present inventors have observed, in view of the above factors, that it would be advantageous to provide a loudspeaker assembly in which a grille allows for better drainage of water (from a space between the loudspeaker and grille) compared with the design of Figures. 2A and 2B, and yet which is capable of implementing the teachings of WO2022 / 189546A1 .

[0017] In a first aspect of the present invention, there is provided: A loudspeaker assembly configured to be mounted to a vehicle, the loudspeaker assembly including: a loudspeaker, including 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 that faces in a forwards direction parallel to the movement axis and a rear face that faces in a rearwards direction parallel to the movement axis, wherein the loudspeaker has a front face that faces in the forwards direction and includes the front face of the diaphragm; and a grille, positioned in front of the front face of the loudspeaker, with a rear face of the grille facing in the rearwards direction toward the front face of the loudspeaker, and with a front face of the grille facing in the forwards direction, wherein the front face of the grille is configured to face downwards and be exposed to an outdoor environment when the loudspeaker assembly is mounted to the vehicle; wherein the grille includes openings which extend from the rear face of the grille to the front face of the grille, wherein the openings are configured to permit sound to pass from the rear face of the grille to the front face of the grille, and to inhibit the ingress of water incident on the front face of the grille from entering into a space enclosed between the rear face of the grille and the front face of the loudspeaker when the loudspeaker assembly is in use; wherein the rear face of the grille includes a sloped region which extends circumferentially around the movement axis, wherein the sloped region, when viewed in cross section in a plane parallel to the movement axis, slopes from a rearwardmost extent of the sloped region to a forwardmost extent of the sloped region with respect to the movement axis; wherein the openings include slots formed in the sloped region, wherein each slot in the sloped region, when viewed in cross section in a plane parallel to the movement axis, extends from a first location positioned towards the rearwardmost extent of the sloped region to a second location positioned at the forwardmost extent of the sloped region so as to facilitate drainage of water from the rear face of the grille when the loudspeaker assembly is mounted to the vehicle.

[0018] The present inventors have observed that slots formed in this way are able to improve the drainage of water from the space enclosed between the grille and loudspeaker the loudspeaker (yet still be effective in inhibiting the ingress of water and particulate matter incident on the front face of the grille into this space), without requiring a widening of the slots, when the loudspeaker assembly is mounted to a vehicle with the front face of the grille facing downwards and exposed to an outdoor environment. Without wishing to be bound by theory, it is thought this improvement in drainage comes from water trapped in the slots by capillary action being pulled towards the second location by the effect of gravity, which helps to drain the slot (see e.g. path of water 170 as shown in Figure 4A).

[0019] In the context of this disclosure, the terms “up” and “down” are generally used to denote up and down with respect to the loudspeaker assembly when the loudspeaker assembly is mounted to a vehicle (e.g. a car), typically with the front face of the grille facing downwards. However, for the avoidance of any doubt, when the loudspeaker assembly is mounted in a vehicle with the front face of the grille facing downwards, the loudspeaker assembly need not be mounted with the movement axis of the loudspeaker assembly being exactly vertical. Rather, the loudspeaker assembly may be mounted with the front face of the grille facing downwards when the movement axis of the loudspeaker assembly is a few degrees off vertical, e.g. as shown in Figure 1 . Note that even with the loudspeaker assembly mounted in this way, the present inventors have found that the slots formed according to the invention are still able to usefully drain the loudspeaker assembly (e.g. as discussed in more detail in the specific description, below).

[0020] In the context of this disclosure, the terms “forwards” and “rearwards” are generally used to describe opposite directions with respect to the movement axis of the loudspeaker assembly. Thus the “forwardmost extent” of the sloped region when viewed in cross section in a plane parallel to the movement axis is intended to refer to a part of the sloped region that is furthest along the movement axis in the “forwards” direction as viewed within that cross section. Similarly, the “rearwardmost extent” of the sloped region is intended to refer to a part of the sloped region that is furthest along the movement axis in the “rearwards” direction as viewed within that cross section.

[0021] In the context of this disclosure, a slot may be understood as a passage formed in the grille which extends between an elongate aperture in the rear surface of the grille to an elongate aperture in the front surface of the grille. The passage may in some examples follow a straight line path when viewed in cross section, but in other examples may be labyrinthine, e.g. as shown in Figure 5C.

[0022] The “first location” (from which each slot extends) is defined as being “towards” the rearwardmost extent of the sloped region, meaning that it is closer to the rearwardmost extent that it is to the forwardmost extent.

[0023] The “second location” (to which each slot extends) is defined as being “at” the forwardmost extent of the sloped region, meaning that the slot should provide an aperture in the rear surface of the grille (i.e. it should be open to allow water to enter into the slot) substantially at the forwardmost extent of the sloped region, so as to allow water to enter into the slot at the aperture in the rear surface of the grille (so it can subsequently exit the slot from the aperture in the front surface of the grille after passing along the passage formed between these apertures, e.g. as depicted in Figure 5D), rather than collect at this location.

[0024] The movement axis may also serve as an axis of the grille.

[0025] For avoidance of any doubt, the “forwardmost extent” may vary with rotational position around the movement axis - i.e. it need not always be a constant distance along the movement axis, as it is in the specific examples discussed below (where the forwardmost extent of the sloped region is, in effect, a circle at a fixed distance along the movement axis.

[0026] For avoidance of any doubt, the sloped region need not form a straight line when viewed in cross section along the movement axis. For example, the sloped region may be curved when viewed in cross section along the movement axis. The sloped region should, however, form a slope with respect to the movement axis.

[0027] For avoidance of any doubt, the slots need not follow a straight line path when the front face of the grille is viewed along the movement axis. For example, the slots may follow a curved or zig zag path along the front face of the grille, when the front face of the grille is viewed along the movement axis.

[0028] In some examples, each slot in the sloped region may begin at the first location and terminate at the second location. However, this need not be the case in all examples of the invention since, for example, the slot may extend beyond the second location, e.g. into a reverse sloped region as described below.

[0029] In some examples, the “first location” (from which each slot extends) may be at or adjacent to the rearwardmost extent of the sloped region. However, this is not essential, and the first location may be located some distance from the rearwardmost extent of the sloped region (as long as it is positioned “towards” the rearwardmost extent, i.e. closer to the rearwardmost extent than the forwardmost extent).

[0030] In some examples, for each slot, the slot provides (e.g. at its second location) an aperture located in a valley formed in the rear face of the grille, the valley being formed by the sloped region transitioning to a reverse sloped region, wherein the sloped region and the reverse sloped region slope forwardly towards aperture.

[0031] In this way, for each slot, the reverse sloped region helps to direct water to the aperture provided by the slot (e.g. at its second location), which the inventors have found helps to better drain water from space between the loudspeaker and grille.

[0032] As noted above, a slot may be understood as a passage formed in the grille which extends between an elongate aperture in the rear surface of the grille to an elongate aperture in the front surface of the grille. Thus, for each slot, the aperture located in the valley which is provided by the slot may be provided by the aperture in the rear surface of the grille from which the passage of the slot extends to the aperture in the front surface of the grille (see e.g. Figure 5A, below).

[0033] The term “reverse” in “reverse sloped region” is intended to refer to the reverse sloped region being sloped oppositely to the sloped region (e.g. when viewed in cross-section in a plane parallel to the movement axis), thereby forming the valley. Thus if the sloped region slopes forwardly (i.e. in the forwards direction) towards the aperture as distance increases from the movement axis (e.g. when viewed in cross section in a plane parallel to the movement axis), the reverse sloped region should slope forwardly towards the aperture as distance decreases from the movement axis (this is shown for example in Figure 7B). Alternatively, if the sloped region slopes forwardly towards the aperture as distance decreases from the movement axis, the reverse sloped region should slope forwardly towards the aperture as distance increases from the movement axis (not shown in the drawings).

[0034] In some examples, the reverse sloped region, when viewed in cross section in a plane parallel to the axis of the movement axis, forms an angle of at least 5° (in some examples at least 10°, in some examples at least 15°) relative to a plane perpendicular to the movement axis.

[0035] In some examples, As / A3 > 60%, more preferably wherein As / A3 > 70%, more preferably

[0036] As / A3 > 80%. In this context, A3 is the area which is the sum of cross-sectional areas for all openings in the grille which allow for airborne sound propagation through the grille, wherein for each of said openings, the cross-sectional area of the opening is defined as the minimum cross-section of the opening along the path of airborne sound propagation through the opening [cm2], wherein As is the sum of cross-sectional areas for all slots in the sloped region which allow for airborne sound propagation through the grille.

[0037] Thus, As / A3 can be understood as a measure of what proportion of the total cross-sectional area for airborne sound propagation provided by the grille is provided by the slots in the sloped region, and values of As / A3 > 60% (more preferably > 70%, more preferably > 80%) equates to most of the total cross- sectional area for airborne sound propagation being provided by the slots. Preferably, all slots in the sloped region which contribute to ‘As’ are slots which extend from a first location to a second location, as recited in connection with this aspect of the invention. However, for the avoidance of any doubt, we note that in some examples there may be some additional slots in the sloped region which do not extend from a first location to a second location in this matter (see e.g. the discussion of circumferentially extending openings, below).

[0038] In some examples, the sloped region, when viewed in cross section in a plane parallel to the movement axis, forms an angle of at least 10°, (in some examples at least 20°, in some examples at least 25°) relative to a plane perpendicular to the movement axis. This helps to encourage flow of water down the sloped region, which helps to facilitate drainage of the space between the grille and the loudspeaker.

[0039] Here, the angle formed by a slot relative to a plane perpendicular to the movement axis may be understood as an angle formed between a plane perpendicular to the movement axis and the rear face of the grille when viewed in cross section in a plane parallel to the movement axis. This angle may vary along the length of the slope, e.g. if the slope of the sloped portion varies along its length.

[0040] In some examples, each slot forms an angle of at least 10° (in some examples at least 20°, in some examples at least 30°), relative to a plane perpendicular to the movement axis. This helps to facilitate drainage of the space between the grille and the loudspeaker.

[0041] Here, the angle formed by a slot relative to a plane perpendicular to the movement axis may be understood as an angle formed between a plane perpendicular to the movement axis and a line drawn along the slot at the rear face of the grille. This angle may vary along the length of the slot, e.g. if the slope of the sloped portion varies along its length, or if the slot does not follow a straight line path when the front face of the grille is viewed along the movement axis.

[0042] In some examples, for each slot, the second location may be at least 5 mm further forward along the movement axis, more preferably at least 10mm further forward along the movement axis, than the first location. Again, this helps to facilitate drainage of the space between the grille and the loudspeaker.

[0043] In some examples, there are no circumferentially extending openings in the sloped region.

[0044] In this context, a circumferentially extending opening may be understood as an elongate opening which extends predominantly in a direction which is circumferential with respect to the movement axis, preferably with little or no radial component.

[0045] As discussed above, the present inventors have found that circumferentially extending openings are not well suited for drainage to facilitate drainage of the space between the grille and the loudspeaker, so it is generally better to omit them or at least ensure that they provide a relatively small proportion of the total cross-sectional area for airborne sound propagation.

[0046] Thus, in some examples, Ac I A3 < 20%, more preferably Ac I A3 < 10%, more preferably Ac I A3 < 5%, where Ac is the sum of cross-sectional areas for all circumferentially extending openings in the sloped region. For avoidance of any doubt, if the sloped region does include any circumferentially extending openings (which could in theory be referred to as “circumferentially extending slots”, though we are avoiding using this term in this context to avoid confusion with slots which extend from a first location to a second location as required by the first aspect of the invention), these circumferentially extending openings might in some examples be excluded from contributing towards the value of As defined previously, since ‘As’ may be used to provide a measure of the cross-sectional area provided by slots which extend from a first location to a second location as required by the first aspect of the invention.

[0047] In some examples, each slot has an acoustical width of no more than 3mm (preferably no more than 2.5mm), wherein the acoustical width is defined as the minimum (i.e. smallest measurable) width of the slot along the path of airborne sound propagation through the slot. This helps with inhibiting the ingress of water and particulate matter (e.g. dirt particles) incident on the front face of the grille into the space between the grille and the loudspeaker.

[0048] In some examples, each slot has an acoustical width of more than 1 mm (preferably more than 1 .5mm), wherein the acoustical width is defined as the minimum (i.e. smallest measurable) width of the slot along the path of airborne sound propagation through the slot. This helps with allowing sound to propagate through the grille when the loudspeaker assembly is in use.

[0049] In some examples, each slot has a length of at least 10mm, in some examples at least 15mm. This length may be measured at the rear surface of the grille. As noted previously, each slot need not follow a straight line path when the front face of the grille is viewed along the movement axis.

[0050] In some examples, the sloped region slopes forwardly away from the movement axis, when the front face of the grille faces downwards.

[0051] In some examples, the sloped region slopes forwardly (i.e. in the forwards direction) towards the aperture as distance increases from the movement axis (e.g. when viewed in cross section in a plane parallel to the movement axis).

[0052] In other examples (not shown in the drawings), the sloped region slopes forwardly (i.e. in the forwards direction) towards the aperture as distance decreases from the movement axis (e.g. when viewed in cross section in a plane parallel to the movement axis).

[0053] In some examples, the sloped region is dish shaped (e.g. shaped as a frustocone). If the sloped region slopes forwardly (i.e. in the forwards direction) towards the aperture as distance increases from the movement axis, this dish shape may be convex at the rear face of the grille.

[0054] In some examples, the rear face of the grille may include a concave central region which slopes forwardly from a rearwardmost periphery of the concave central region towards a floor of the concave central region. This concave central region may be surrounded by the sloped region, e.g. with the sloped region extending around the concave central region. In some examples, the floor of the concave central region may be substantially planar. In other examples, the floor of the concave central region may be a curved surface.

[0055] In some examples, the openings (included in the grille) may include one or more slots formed in the concave central region, wherein the / each slot extends from a first location positioned towards the rearwardmost periphery (i.e. closer to the rearwardmost periphery than the floor) of the concave central region to a second location positioned towards the floor of the concave central region (i.e. closer to the floor than the periphery) so as to facilitate drainage of water from the concave central region when the loudspeaker assembly is mounted to the vehicle. The second location of the / each slot may be located at the floor of the concave central region.

[0056] The floor may be a location or set of locations of the concave central region which are forwardmost within the concave central region. The slots may each extend to a second location at the floor of the concave central region. Note, however, that the slots might not terminate at the floor (i.e. at a forwardmost location of the concave central region) in all examples (see e.g. Figure 8A), since this might be difficult to manufacture.

[0057] In some examples, each slot in the concave central region may begin at the first location and terminate at the second location.

[0058] In some examples, the openings (included in the grille) may include a hole formed in the floor of the concave central region so as to facilitate drainage of water from the concave central region when the loudspeaker assembly is mounted to the vehicle. The hole may have a width of 6mm or more. The hole may have a width of 12mm or less.

[0059] The front face of the grille may include a cover which at least partially obscures the hole when viewed along the movement axis from the front face of the grille.

[0060] In some examples, the rear face of the grille is contoured to at least partly follow contours in the front face of the loudspeaker, when the diaphragm is in its rest position. As discussed e.g. in WO2022 / 189546A1 , a grille whose rear face is contoured in this way helps to facilitate a lower values of V1 / V2 (V1A / 2 is discussed in more detail below). This may be achieved, for example, by the sloped region in the rear face of the grille being shaped to correspond to a shape of the diaphragm, and / or the reverse sloped region being shaped to correspond to the shape of a suspension of the loudspeaker.

[0061] In some examples, the sloped region in the rear face of the grille may be shaped to correspond to a dish shape of (e.g. a frustoconical shape of) the diaphragm of the loudspeaker.

[0062] In some examples, the reverse sloped region in the rear face of the grille (if present) may be shaped to correspond to the shape of a suspension (e.g. a roll suspension) via which the diaphragm is suspended from a frame of the loudspeaker.

[0063] In some examples, the concave central region (if present) may be shaped to correspond to the shape of a dustcap of the loudspeaker.

[0064] The loudspeaker assembly may include any of the features described in connection with the loudspeaker assemblies of WO2022 / 189546A1 , except where such a combination is clearly impermissible or expressly avoided. The advantages of such features are discussed in detail in WO2022 / 189546A1 .

[0065] Thus, in some examples, V1 / V2 < 0.7, wherein V1 is a volume of space [cm3] enclosed between the front face of the loudspeaker when the diaphragm is in its rest position and the rear face of the grille, and V2 is a volume of space [cm3] enclosed between the front face of the loudspeaker when the diaphragm is in its rest position and a plane perpendicular to the movement axis that has a position along the movement axis corresponding to a forwardmost position of the grille on the movement axis.

[0066] Thus, in some examples, V1 / V2 < 0.5, more preferably V1 / V2 < 0.3.

[0067] The rest position of the diaphragm may be defined as a position at which the diaphragm is at rest, when the loudspeaker is not in use, preferably without force being exerted on it by the drive unit, preferably with equalised pressure on both front and rear faces of the diaphragm. The rest position may alternatively be described as the “neutral” position.

[0068] Thus, in some examples, the rear face of the grille may be contoured to substantially match contours in the front face of the loudspeaker when the diaphragm is in its rest position.

[0069] Thus, in some examples, the grille is configured (e.g. by configuring it according to one or more teachings provided herein or in WO2022 / 189546A1) such that:

[0070] • the acoustic transfer function is higher than 3dB for at least some frequencies in the range 1.8kHz-7.2kHz; and / or

[0071] • the acoustic transfer function is higher than 3dB for at least some frequencies in the range

[0072] 1 .8kHz-3.6kHz (a particularly important frequency band for the production of sound by an AVAS loudspeaker; and / or

[0073] • the acoustic transfer function is higher than 6dB for at least some frequencies in an above-stated range (e.g. in the range 1 .8kHz-7.2kHz, or the range 1 .8kHz-3.6kHz); and / or

[0074] • the acoustic transfer function is higher than OdB, more preferably higher than 3dB, for at least half of the 1 / 3th octave bands in an above stated range; and / or

[0075] • the acoustic transfer function is higher than OdB for all frequencies in an above stated range; and / or

[0076] • the acoustic transfer function does not fall below -10 dB (more preferably -5dB, more preferably OdB) at any frequency in a frequency range in which the loudspeaker assembly is rated for use (“rated frequency range”); and / or

[0077] • the acoustic transfer function does not fall below -10 dB (more preferably -5dB, more preferably OdB) at any frequency in the range 1 .8kHz-3.6kHz.

[0078] Thus, in some examples, Mlf 2 > 5 (preferably Mlf 2 > 10, more preferably A1 / A2 > 20), wherein A1 is the area corresponding to the movable part of the front face of the loudspeaker as projected onto a plane perpendicular to the movement axis [cm2], and A2 is the area within A1 which has a direct line of sight to the front face of the loudspeaker in the direction of the movement axis [cm2].

[0079] Thus, in some examples, A1 / A3 > 3 (preferably A1 / A3 > 3, more preferably A1 / A3 > 6, more preferably A1 / A3 > 10), wherein A1 is as defined above [cm2], and A3 is the area which is the sum of cross-sectional areas of all openings in the grille which allow for airborne sound propagation through the grille, wherein for each of said openings, the cross-sectional area of the opening is defined as the minimum crosssection of the opening along the path of airborne sound propagation through the opening [cm2].

[0080] Thus, in some examples, a distance h measured between the front face of the loudspeaker when the diaphragm is in its rest position and the rear face of the grille (excluding any gaps in the rear face of the grille) in the direction of the movement axis, does not exceed hmax mm, wherein hmax mm may be 15mm, more preferably 10mm, more preferably 5mm.

[0081] Thus, in some examples, the grille may be formed by a one-piece grille element which provides the front and rear faces of the grille, wherein the openings are formed in said one-piece grille element. The grille is preferably formed of a rigid material. In some examples the rigid material may be a polymer, such as polypropylene.

[0082] Thus, in some examples, the rear face of the grille may be configured to (e.g. by appropriately contouring the rear face of the grille, and positioning it appropriately along the movement axis) physically contact the front face of the diaphragm at multiple locations dispersed across the front face of the diaphragm when the diaphragm is pushed in the forwards direction to a predefined mechanical stop position, so as to prevent the diaphragm from moving beyond the predefined mechanical stop position when the loudspeaker is in use.

[0083] The loudspeaker may include a frame from which the diaphragm is suspended by at least one suspension.

[0084] For example, an outer edge of the diaphragm may be suspended from the frame by a surround, which may be implemented as a roll suspension. Another part of the diaphragm (preferably inwardly spaced from the outer edge of the diaphragm) may be suspended from the frame by a further suspension (e.g. a spider).

[0085] The diaphragm and surround may be formed of a single piece of material, e.g. as described in WO2022 / 253924 or WO2024 / 1 15672.

[0086] The front face of the diaphragm may be concave and the rear face of the diaphragm may be convex. For example, the diaphragm may be dish shaped (e.g. shaped as a frustocone), with a concave radiating surface on the concave side of the diaphragm providing the front face of the diaphragm, and a convex radiating surface on the convex side of the diaphragm providing the rear face of the diaphragm. Other diaphragm shapes are well-known.

[0087] The diaphragm may be flat in some examples, though is preferably non-flat.

[0088] The loudspeaker may include a dustcap on the front face of the loudspeaker. The dustcap may be integral with the diaphragm, e.g. as described in WO2024 / 115672.

[0089] The drive unit may be an electromagnetic drive unit that includes a magnet unit configured to produce a magnetic field in an air gap, and a voice coil attached to the diaphragm (typically via an intermediary coupling element, such as a voice coil former). The magnet unit may be attached to the frame. In use, the voice coil may be energized (have a current passed through it based on the electrical signal) to produce a magnetic field which interacts with the magnetic field produced by the magnet unit and which causes the voice coil (and therefore the diaphragm) to move relative to the magnet unit along the movement axis. The magnet unit may include a permanent magnet. The voice coil may be configured to sit in the air gap when the diaphragm is at rest. Such drive units are well known.

[0090] The loudspeaker assembly may include an enclosure configured to receive sound (pressure) produced by a rear face of diaphragm, and to inhibit sound (pressure) produced by the rear face of diaphragm from leaking into the environment.

[0091] The loudspeaker assembly may be configured for use in a road vehicle with the front face of the grille exposed to an outdoor environment.

[0092] The loudspeaker assembly may form part of an Acoustic Vehicle Alerting System (AV AS).

[0093] In a second aspect of the invention, there may be provided a vehicle, wherein a loudspeaker assembly according to the first aspect of the invention is mounted to the vehicle with the front face of the grille facing downwards and exposed to an outdoor environment.

[0094] Without wishing to be bound by theory, the present inventors believe that the slots facilitate drainage of the space enclosed between the grille and the loudspeaker because each slot extends to a second location positioned at the forwardmost extent of the sloped region, which helps water drain from this second location (rather than gather there).

[0095] The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

[0096] Summary of the Figures

[0097] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0098] Figure 1 schematically shows a vehicle to which a loudspeaker assembly according to the present disclosure is mounted.

[0099] Figures 2A and 2B implement a grille design similar to that taught by Figure. 4A of WO2022 / 189546A1 .

[0100] Figure 3 shows a cross-sectional view of a loudspeaker assembly according to the present disclosure.

[0101] Figures 4A, 4B, and 4C respectively show a rear perspective view, a front perspective view, and a front view of a grille included in the loudspeaker assembly of Figure 3.

[0102] Figures 5A, 5B, 5C, and 5D show respective different views of a slot formed in the sloped region of the grille of Figures 4A-C.

[0103] Figure 6 schematically shows a partial cross-sectional view of the diaphragm and grille of the loudspeaker assembly of Figures 4A-C.

[0104] Figure 7A shows a cross-sectional view of the grille of the loudspeaker assembly of Figures 4A-C. Figure 7B shows a magnified partial view of the grille as shown in Figure 7A.

[0105] Figures 8A and 8B respectively show a rear perspective view and a front perspective view of a variant of a grille according to the present disclosure, which could be used in the loudspeaker assembly of Figures 4A-C.

[0106] Detailed Description of the Invention

[0107] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0108] Figure 1 shows a vehicle 200, in this example a car, to which a loudspeaker assembly 100 according to the disclosure is mounted, with a front face 158 of a grille 150 of the loudspeaker assembly 100 (discussed in more detail below) facing downwards and exposed to an outdoor environment. Note that although the front face 158 of the grille 150 of the loudspeaker assembly 100 faces downwards, it does not in this example face vertically downwards, as a movement axis 112 of the loudspeaker assembly is inclined at an angle that is a few degrees off vertical 114. In practice, the inventors have found that a small incline of this nature does not significantly impact drainage of the loudspeaker assembly, though it is preferable for this angle to be less than the angle at which the sloped region 152 (discussed below), and if present the reverse sloped region 159 (also discussed above), when viewed in cross section in a plane parallel to the movement axis 112, form relative to a plane perpendicular to the movement axis 112 (so that water still rolls down the sloped region 152 and reverse sloped region 159 when the loudspeaker assembly is mounted to the vehicle). A skilled person would appreciate that the exact angle of incline (between movement axis and vertical when the loudspeaker assembly 100 is mounted to the vehicle) would depend on a multitude of factors including not just drainage of water from the grille 150, but also factors concerning the design of the vehicle 200 itself.

[0109] In other examples (not shown), the loudspeaker assembly 100 may be mounted to the vehicle 200 with the front face 158 of the grille 150 of the loudspeaker assembly 100 facing vertically downwards, i.e. with the movement axis 112 vertical.

[0110] Figure 3 shows the loudspeaker assembly 100 according to the present disclosure in more detail. The loudspeaker assembly 100 has a loudspeaker 110 including a drive unit 120 and a diaphragm 130.

[0111] The loudspeaker 100 includes a frame 113 from which the diaphragm 130 is suspended by at least one suspension that includes a surround 115. An outer edge of the diaphragm 130 is suspended from the frame 113 by the surround 115, which here is implemented as a roll suspension. Another part of the diaphragm, inwardly spaced from the outer edge of the diaphragm, is suspended from the frame by a further suspension (e.g. a spider).

[0112] The drive unit 120 is configured to move the diaphragm 130 along a movement axis 112, wherein the diaphragm has a front face 132 that faces in a forwards direction parallel to the movement axis 112 and a rear face 134 that faces in a rearwards direction parallel to the movement axis 112. The loudspeaker has a front face 111 that faces in the forwards direction and includes the front face 132 of the diaphragm 130. The forward direction, F, and the rearwards direction, R, are indicated in Figures 3, 4A, 5B, 6, 7A, and 8A.

[0113] In this example, the drive unit 120 is an electromagnetic drive unit that includes a magnet unit (not labelled) configured to produce a magnetic field in an air gap, and a voice coil (not labelled) attached to the diaphragm (typically via an intermediary coupling element, such as a voice coil former). In use, the voice coil is energized to produce a magnetic field which interacts with the magnetic field produced by the magnet unit and which causes the voice coil (and therefore the diaphragm 130) to move relative to the magnet unit along the movement axis 112. The magnet unit may include a permanent magnet.

[0114] The front face 132 of the diaphragm 130 is concave and the rear face 134 of the diaphragm is convex. The diaphragm 130 is dish shaped (in this example, shaped as a frustocone), with a concave radiating surface on the concave side of the diaphragm providing the front face 132 of the diaphragm 130, and a convex radiating surface on the convex side of the diaphragm providing the rear face 134 of the diaphragm. The loudspeaker 100 includes a dustcap 117 on the front face 111 of the loudspeaker 100, to protect against dust ingress into the air gap.

[0115] The diaphragm 130, the surround 115 and the dustcap 117 are in this example formed of a single piece of material, e.g. as described in WO2024 / 1 15672.

[0116] The loudspeaker assembly 100 includes an enclosure 118 configured to receive sound (pressure) produced by the rear face 134 of diaphragm 130, and to inhibit sound (pressure) produced by the rear face of diaphragm from leaking into the environment.

[0117] In addition to the loudspeaker 110, the loudspeaker assembly 100 also includes a grille 150 positioned in front of the front face 111 of the loudspeaker (and thus in front of the front face 132 of the diaphragm 130), with a rear face 156 of the grille facing in the rearwards direction toward the front face 111 of the loudspeaker, and with a front face 158 of the grille 150 facing in the forwards direction. The front face of the grille 150 is configured to face downwards and be exposed to an outdoor environment when the loudspeaker assembly 100 is mounted to the vehicle 200.

[0118] The rear face 156 of the grille 150 is contoured to at least partly follow (ideally substantially match) the contours in the front face 1 11 of the loudspeaker 110, when the diaphragm is in its rest position, which helps facilitate a reduction in V1A / 2, wherein V1 is a volume of space [cm3] enclosed between the front face of the loudspeaker when the diaphragm 130 is in its rest position and the rear face of the grille, and V2 is a volume of space [cm3] enclosed between the front face of the loudspeaker when the diaphragm is in its rest position and a plane perpendicular to the movement axis 1 12 that has a position along the movement axis corresponding to a forwardmost position of the grille 150 on the movement axis. For this example, V1A / 2 = 29.5 [cm3] / 122 [cm3] = 0.24.

[0119] Furthermore, a distance h measured between the front face 11 1 of the loudspeaker 110 when the diaphragm is in its rest position and the rear face 156 of the grille 150 (excluding any gaps in the rear face of the grille) in the direction of the movement axis 112, does not exceed hmax mm. For this example, hmax is 6.5mm at the location depicted on Figure 3.

[0120] Figures 4A-4C show the grille 150 of Figure 3 in more detail.

[0121] The grille 150 includes openings 154, 164 which extend from the rear face 156 of the grille to the front face 158 of the grille. The openings 154, 164 are configured to permit sound to pass from the rear face 156 of the grille 150 to the front face 158 of the grille, and to inhibit the ingress of water incident on the front face of the grille from entering into a space enclosed between the rear face of the grille and the front face 11 1 of the loudspeaker 110 when the loudspeaker assembly 100 is in use.

[0122] The grille 150 is formed by a one-piece grille element which provides the front 158 and rear 156 faces of the grille and the openings 154, 162, 164 are formed in said one-piece grille element. The grille 150 is formed of a rigid material.

[0123] A1 is the area corresponding to the movable part of the front face of the loudspeaker 110 as projected onto a plane perpendicular to the movement axis [cm2], and A2 is the area within A1 which has a direct line of sight to the front face of the loudspeaker in the direction of the movement axis [cm2]. A3 is the area which is the sum of cross-sectional areas of all openings in the grille 150 which allow for airborne sound propagation through the grille, wherein for each of said openings, the cross-sectional area of the opening is defined as the minimum cross-section of the opening along the path of airborne sound propagation through the opening [cm2].

[0124] A1 / A3 represents the extent to which the grille is acoustically closed. For this example A1 / A3 = 105.14 [cm2] 16.27 [cm2] = 16.77 which, as discussed in WO2022 / 189546A1 , helps to boost the gain of the loudspeaker assembly 100 in a desirable manner.

[0125] As discussed in WO2022 / 189546A1 , A1 / A2 characterizes the extent to which the grille is able to inhibit the ingress of water incident on the front face of the grille 150 from entering the space enclosed between the rear face of the grill and the front face of the loudspeaker. A1 / A2 also characterizes the extent to which the grille protects against stones and small particles from entering this space. A relatively high value of A1 / A2 is thus preferred. For this loudspeaker, A1 / A2 = 105.14 [cm2] 1 0.32 [cm2] = 328.

[0126] Next, the rear face 156 of the grille 150 includes a sloped region 152 which extends circumferentially around the movement axis 112. When viewed in cross section in a plane parallel to the movement axis, the sloped region slopes from a rearwardmost extent of the sloped region 152 to a forwardmost extent of the sloped region with respect to the movement axis 112. In other words, the sloped region 152 slopes forwardly away from the movement axis 112, when the front face of the grille faces downwards as shown in Figure 4A. The sloped region 152 is dish shaped (in this example a frustocone), with the dish shape being convex at the rear face 156 of the grille 150.

[0127] The rear face 156 of the grille 150 also includes a concave central region 160 which slopes forwardly from a rearwardmost periphery 167 of the concave central region towards a floor 166 of the concave central region. This concave central region 160 is surrounded by the sloped region 152 such that the sloped region 152 extends around the concave central region 160. In this example, the openings of the grille 150 include a hole 164 formed in the floor 166 of the concave central region so as to facilitate drainage of water from the concave central region when the loudspeaker assembly 100 is mounted to the vehicle 200. The hole 164 has a width of around 8mm. As shown for example in Figures 3, 4B, 4C, and 7A, the front face 158 of the grille 150 includes a cover 165 which obscures the hole 164 when viewed along the movement axis 112 from the front face 158 of the grille 150, which helps contribute to the grille having a large value of A1 / A2 (which as noted above is = 328 for this example).

[0128] The openings 154, 162, 164 of the grille 150 further include slots 154 formed in the sloped region 152, wherein each slot in the sloped region, when viewed in cross section in a plane parallel to the movement axis 112, begins at a first location 153a positioned at the rearwardmost extent of the sloped region 152 and extends to and terminates at a second location 153b positioned at the forwardmost extent of the sloped region so as to facilitate drainage of water along path 170 from the rear face 156 of the grille 150 when the loudspeaker assembly 100 is mounted to the vehicle 200. Since each slot 154 begins at the first location 153a, the first location 153a can also be referred to as a first end 153a. Since each slot 154 terminates at the second location 153b, the second location 153b can also be referred to as a second end 153b.

[0129] There are no circumferentially extending openings in the sloped region 152, a circumferentially extending opening being an elongate opening which extends predominantly in a direction which is circumferential with respect to the movement axis 112, preferably with little or no radial component. As discussed above, such circumferentially extending openings can be problematic from a water drainage perspective.

[0130] As is the sum of cross-sectional areas for all openings in the sloped region 152 (in this case all slots 154, since the slots 154 are the only openings in the sloped region 152) which allow for airborne sound propagation through the grille. As noted above, As / A3 can be understood as a measure of what proportion of the total cross-sectional area for airborne sound propagation provided by the grille is provided by the slots 154 in the sloped region. For this example, As is 5.27 [cm2] (0.439 [cm2] for each of the 12 slots), A3 is 6.27 [cm2] (5.27 [cm2] for the slots plus 0.10 [cm2] for the center hole), and therefore As I A3 is 5.27 [cm2] 16.27 [cm2] = 84%.

[0131] The structure of slots 154 in the sloped region 152 of the grille 150 is shown in more detail in Figures 5A- 5D, where Figures. 5C-D show the grille when viewed in the cross section indicated by Y-Y in Figure 5B.

[0132] For each slot 154, the second end 153b of the slot 154 provides (at its second end 153b) an aperture 155 located in a valley 147 formed in the rear face 156 of the grille 150. The valley 157 is formed by the sloped region 152 transitioning to a reverse sloped region 159, wherein the sloped region 152 and the reverse sloped region 159 slope forwardly towards the aperture 155 (see also Figure 6).

[0133] The aperture 155 is part of the slot itself, i.e. part of an elongate aperture formed in the rear surface of the grille which extends to an elongate aperture formed in the front surface of the grille via a passage formed in the grille (see e.g. Figure 5D). Water is able to enter into the slot at the aperture in the rear surface of the grille, and then exit the slot from the aperture in the front surface of the grille after passing along the passage formed between these apertures, rather than collect at the second location 153b. In this example, the passage does not follow a straight-line path when viewed in cross section, but is instead labyrinthine, as shown in Figures 5C and 5D.

[0134] With reference to Figure 5C, each slot 154 has an acoustical width, W, which is defined as the minimum (i.e. smallest measurable) width of the slot along the path of airborne sound propagation 180 through the slot 154. In this example, each slot 154 has an acoustical width, W, of ~2mm.

[0135] For each slot 154, the length of the slot 154 as measured at the rear surface 156 of the grille 150 is ~22.4mm and the second location 153b is -11.6 mm further forward along the movement axis 112 than the first location 153a.

[0136] Each slot 154 forms an angle of around 30° relative to a plane perpendicular to the movement axis 112 (see also Figure 6). This helps to facilitate drainage of the space between the grille 150 and the loudspeaker 110.

[0137] The structure of the reverse sloped region 159 of the grille 150 can be seen in more detail in Figure 6 (which is a simplified view of the grille 150) and also Figures 7A-7B

[0138] The reverse sloped region 159 is sloped oppositely to the sloped region 152 when viewed in crosssection in a plane parallel to the movement axis 112, thereby forming the valley 157. As shown in Figure 6 for example, the sloped region slopes 152 forwardly (i.e. in the forwards direction) towards the aperture 155 as distance increases from the movement axis 112, and the reverse sloped region 159 slopes forwardly towards the aperture 155 as distance decreases from the movement axis 112.

[0139] The sloped region 152 in the rear face 156 of the grille 150 is shaped to correspond to a dish shape of the diaphragm 130, the reverse sloped region 159 is shaped to correspond to the shape of the surround 115, and the concave central region 160 is shaped to correspond to the shape of the dustcap 117 of the loudspeaker.

[0140] As shown in Figure 6, the sloped region 152, when viewed in cross section in a plane parallel to the movement axis 112, forms an angle, p, of in this example around 30° relative to a plane perpendicular to the movement axis 112. This helps to encourage flow of water down the sloped region 152, which helps to facilitate drainage of the space between the grille 150 and the loudspeaker 110. In practice, this angle p is limited by the angle (in this case 30°) of the frustoconical portion of the diaphragm 130 (if the angle p were larger than the angle of the frustoconical portion of the diaphragm 130, then it would interfere with movement of the diaphragm 130 or would not allow for an adequately small value of V1A / 2. In practice, the inventors have found that an angle p of at least 10° is useful to help overcome the capillary action of water so as to adequately drain the slots 154.

[0141] As shown in Figure 6B, the reverse sloped region 159, when viewed in cross section in a plane parallel to the movement axis 112, forms an angle, a, of at least 5°, in some examples at least 10°, relative to a plane perpendicular to the movement axis. This helps guide water down the reverse sloped region 159 along path 170, towards the valley 157, again to facilitate water drainage from the loudspeaker assembly 110. A skilled person would appreciate that the drainage of water from the space enclosed between the grille and the loudspeaker will depend on a multitude of factors, such as the dimension of openings, the shape of openings and the material from which the grille is made (e.g. hydrophobic vs hydrophilic) etc. The example dimensions and other parameters given in relation to this example are premised on the grille being made of polypropylene (more specifically, polypropylene with -20% glass fibre mixed into it, e.g. PP-GF20), but a skilled person would appreciate that other materials are possible.

[0142] Figures 8A and 8B show a variant of the grille 150 discussed above. The grille 150 of Figures 8A and 8B only differs from the examples discussed above in that, instead of a hole 164, the concave central region 160 of the grille 150 instead includes a plurality of, in this example three, slots 162. Each slot 162 extends from a first location 161 positioned towards the rearwardmost periphery 167 (i.e. closer to the rearwardmost periphery than the floor 166) of the concave central region 160 to a second location 163 positioned towards the floor 166 of the concave central region 160 (i.e. closer to the floor than the periphery). This helps facilitate drainage of water from the concave central region 160 when the loudspeaker assembly 100 is mounted to the vehicle 200.

[0143] For the example shown in Figures 8A-B, As is 5.27 [cm2] (0.439 [cm2] for each of the 12 slots), A3 is 5.94 [cm2] (5.27 [cm2] for the slots plus 0.67 [cm2] total for the three slots in the concave central region 160), and therefore As / A3 is 5.27 [cm2] 15.94 [cm2] = 89%.

[0144] ***

[0145] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0146] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0147] For example, the slots 154 in the sloped region 152 do not have to be radially extending slots 154 as shown in the figures above, but may instead follow a different, non-straight line path. For example, they may trace an arc shape on the rear face of the grille 150 when viewed along the movement axis.

[0148] For example, the slots 154 in the sloped region 152 do not have to be of the same size.

[0149] For example, the slots may have a cross section when viewed in the cross section indicated by Y-Y in Figure 5B which differs from the cross section depicted in Figures 5C-D. For example, the slots may have a T shape, a ‘double T’ shape, and ‘S’ shape, or a straight line shape, when viewed in the cross section indicated by Y-Y in Figure 5B. For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0150] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0151] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a 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. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. 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 the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

Claims

Claims:1 . A loudspeaker assembly configured to be mounted to a vehicle, the loudspeaker assembly including: a loudspeaker, including 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 that faces in a forwards direction parallel to the movement axis and a rear face that faces in a rearwards direction parallel to the movement axis, wherein the loudspeaker has a front face that faces in the forwards direction and includes the front face of the diaphragm; and a grille, positioned in front of the front face of the loudspeaker, with a rear face of the grille facing in the rearwards direction toward the front face of the loudspeaker, and with a front face of the grille facing in the forwards direction, wherein the front face of the grille is configured to face downwards and be exposed to an outdoor environment when the loudspeaker assembly is mounted to the vehicle; wherein the grille includes openings which extend from the rear face of the grille to the front face of the grille, wherein the openings are configured to permit sound to pass from the rear face of the grille to the front face of the grille, and to inhibit the ingress of water incident on the front face of the grille from entering into a space enclosed between the rear face of the grille and the front face of the loudspeaker when the loudspeaker assembly is in use; wherein the rear face of the grille includes a sloped region which extends circumferentially around the movement axis, wherein the sloped region, when viewed in cross section in a plane parallel to the movement axis, slopes from a rearwardmost extent of the sloped region to a forwardmost extent of the sloped region with respect to the movement axis; wherein the openings include slots formed in the sloped region, wherein each slot in the sloped region, when viewed in cross section in a plane parallel to the movement axis, extends from a first location positioned towards the rearwardmost extent of the sloped region to a second location positioned at the forwardmost extent of the sloped region so as to facilitate drainage of water from the rear face of the grille when the loudspeaker assembly is mounted to the vehicle.

2. A loudspeaker assembly according to claim 1 wherein, for each slot, the slot provides an aperture located in a valley formed in the rear face of the grille, the valley being formed by the sloped region transitioning to a reverse sloped region, wherein the sloped region and the reverse sloped region slope forwardly towards aperture.

3. A loudspeaker assembly according to any previous claim as dependent on claim 2, wherein the reverse sloped region, when viewed in cross section in a plane parallel to the movement axis, forms an angle of at least 5° relative to a plane perpendicular to the movement axis.

4. A loudspeaker assembly according to claim 1 , wherein As / A3 > 80%, wherein A3 is the area which is the sum of cross-sectional areas for all openings in the grille which allow for airborne sound propagation through the grille, wherein for each of said openings, the cross-sectional area of the opening is defined as the minimum cross-section of the opening along the path of airborne soundpropagation through the opening [cm2], wherein As is the sum of cross-sectional areas for all slots in the sloped region which allow for airborne sound propagation through the grille.

5. A loudspeaker assembly according to any previous claim, wherein each slot is forms an angle of at least 10° relative to a plane perpendicular to the movement axis.

6. A loudspeaker assembly according to any previous claim, wherein there are no circumferentially extending slots in the sloped region.

7. A loudspeaker assembly according to any previous claim, wherein each slot has an acoustical width of no more than 3mm, wherein the acoustical width is defined as the minimum width of the slot along the path of airborne sound propagation through the slot.

8. A loudspeaker assembly according to any previous claim, wherein each slot has a length of at least 10mm.

9. A loudspeaker assembly according to any previous claim, wherein the sloped region slopes forwardly away from the movement axis, when the front face of the grille faces downwards.10 A loudspeaker assembly according to any previous claim, wherein the sloped region is dish shaped.11 . A loudspeaker assembly according to any previous claim, wherein V1 / 2 < 0.7, wherein V1 is a volume of space [cm3] enclosed between the front face of the loudspeaker when the diaphragm is in its rest position and the rear face of the grille, and V2 is a volume of space [cm3] enclosed between the front face of the loudspeaker when the diaphragm is in its rest position and a plane perpendicular to the movement axis that has a position along the movement axis corresponding to a forwardmost position of the grille on the movement axis.

12. A loudspeaker assembly according to any previous claim, wherein the rear face of the grille includes a concave central region which slopes forwardly from a rearwardmost periphery of the concave central region towards a floor of the concave central region.

13. A loudspeaker assembly according to any previous claim, wherein the openings include one or more slots formed in the concave central region, wherein the / each slot extends from a first location positioned towards the rearwardmost periphery of the concave central region to a second location positioned towards the floor of the concave central region so as to facilitate drainage of water from the concave central region when the loudspeaker assembly is mounted to the vehicle.

14. A loudspeaker assembly according to any previous claim, wherein the openings include a hole formed in the floor of the concave central region, wherein the front face of the grille includes a coverwhich at least partially obscures the hole when viewed along the movement axis from the front face of the grille.

15. A vehicle, wherein a loudspeaker assembly according to any previous claim is mounted to the vehicle with the front face of the grille facing downwards and exposed to an outdoor environment.

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