The present invention relates to a boxed loudspeaker for mounting to a vehicle, for instance a car, and particularly, although not exclusively, to boxed loudspeakers for mounting between inner and outer portions of a vehicle frame.

Background

Boxed loudspeakers are mounted at various different locations of the Body In White (BIW) build of a vehicle, for instance a car, in order to satisfy musical purposes of the interior. More recently, it has also become common to mount boxed loudspeakers to the vehicle to emit audible noise to the exterior of the car. Such boxed loudspeakers mounted to a vehicle can be referred to as Acoustic Vehicle Alerting Systems (AVAS). Here, one purpose of the boxed loudspeaker is to alert pedestrians to the presence of the vehicle. For instance, in electric drive vehicles, it can be a requirement for the vehicle to generate a warning sound when the vehicle is travelling at low speeds.

Typically, the boxed loudspeakers mounted to the vehicle generally comprises an enclosure (or speaker enclosure) forming a housing that houses a speaker unit for emitting the audible sound, typically in the frequency range of around 200Hz-2kHz.

The speaker unit of known boxed loudspeakers (for AVAS applications and interior sound) typically generate sound pressure through movement of a diaphragm attached to a motor system (e.g. an electromagnetic motor). The diaphragm is suspended at a rest position from which it has limited movement range in both directions. Sound is generated when the diaphragm oscillates around this rest position and excites the air around it. For reasons of efficiency, the diaphragm and components that move with it are designed to be as lightweight as possible. Also, the surface area of the diaphragm is maximized so that it can move the most amount of air and be acoustically efficient. Here, the diaphragm is a dipole sound source, radiating sound to both directions of its movement axis. The acoustical radiation is in opposite phase for each of these directions. Therefore, to generate an audible sound, typically one side of the diaphragm is isolated to prevent the two opposite phases being allowed to sum, which would cause the radiation on these two sides to cancel each other, causing a compromised sound output, for instance a reduction in generated sound. The isolation of one side of the diaphragm can be achieved by mounting the diaphragm in an aperture in the speaker enclosure and forming the speaker enclosure to surround and enclose the diaphragm to form an enclosure. In this way, the opposite side radiation is not able to interfere with the radiation on the listener side in a destructive way.

Accordingly, known boxed loudspeakers have a diaphragm with a listener side open to the exterior of the vehicle (for AVAS applications) orthe interior of the vehicle (for musical purposes) and an opposed, isolated side housed in a speaker enclosure that is mounted to the vehicle. The boxed loudspeakers can be mounted in the dry zone or the wet zone or a combination of both.

For instance, often the boxed loudspeaker for musical purposes is mounted between inner and outer portions of a frame, for instance between inner and outer metal sheets of the BIW. Whereas, AVAS boxed loudspeakers are typically located at the front or rear of the vehicle so that they are positioned close to potential pedestrians in directions of travel of the vehicle. Typically, the front of the vehicle may have a highly enclosed engine compartment restricting location possibilities. Moreover, the aesthetics and aerodynamics of the vehicle can be affected by the mounting location of the AVAS boxed loudspeaker. Consequently, common locations for mounting the boxed loudspeaker are under the radiator and headlights or taillights, where holes can be opened up in an under-body panel or bumper for the listener side of the diaphragm to be exposed to the exterior of the vehicle. Thus, the speaker enclosure of AVAS boxed loudspeakers may be mounted between inner and outer portions of the frame, similar to the boxed loudspeakers for musical purposes, or can be mounted between inner and outer portions of, for instance a bumper. Here, in either location, it is advantageous for the boxed loudspeaker enclosure to prevent the formation of a mechanical bridge between the inner and outer portions. This is because a mechanical bridge can transfer loads from the outer portion to the inner portion. The transfer of load can cause unwanted deformation of the inner portion, and in particular, unwanted deformation of the inner portion into the vehicle.

The present invention has been devised in light of the above considerations. In particular, it is an aim to provide a boxed loudspeaker having a speaker enclosure formed from a housing that does not transfer load from an outer portion to an inner portion of a vehicle even at a low force impact, that is wherein the housing does not transmit a force between two portions of the housing when the impact from a low force impact is applied across the portions.

Summary of the Invention

According to the present invention, the speaker enclosure of the boxed loudspeaker is configured to fail at a low force by fracturing into a master box and a slave box, wherein the slave box collapses into the master box so that, when fractured, the speaker enclosure has a smaller dimension than before the failure. Advantageously, the fracture zone is configured to fracture continuously and instantaneously. Suitably, the speaker enclosure is configured with a fracture zone. Here, the fracture zone defines the separation of the speaker enclosure into the master box and the slave box. The fracture zone suitably defines a perimeter, for instance a perimeter between the master and slave boxes. The master box and slave box include a first portion and a second portion between which the load is applied in a load direction. Here, the first portion and the second portion move towards each other, in the load direction, when the speaker enclosure fails along the fracture zone. Suitably, the load direction may be one dimension of the speaker enclosure, for instance the one dimension may be a height or a thickness or a width or a length of the speaker enclosure. It will be appreciated that the respective terminology may be dependent on the shape and size of the speaker enclosure and the mounting orientation of the speaker enclosure relative to the load direction. However, by way on a non-limiting example, the load direction will herein be described in relation to a height of the speaker enclosure. The fracture zone defines the master box and the slave box so that each of the master box and the slave box has a part of sides of the speaker enclosure in the height direction. Thus, when the slave box collapses into the master box, the portions of the side wall on the slave box overlay the portions of the side wall on the master box when viewed in a plane along the load direction, e.g. a plane through the height of the speaker enclosure. This allows the collapsed speaker enclosure when the fracture zone fails to have a smaller extent in the height direction than when the speaker enclosure is operational. As will be appreciated, if the fracture zone is configured to separate the speaker enclosure into the master box and slave box at a mid-point in the height direction, the maximum height reduction between the operational, unfractured speaker enclosure and the collapsed structure when the speaker enclosure has been fractured through the fracture zone and the slave box collapsed into the master box, can be achieved. Here, distal edges of the fractured perimeter around the salve box abut the master box (and vice-versa) to prevent further collapsing.

According to an aspect there is therefore provided a boxed loudspeaker comprising a speaker enclosure and a speaker unit mounted within the speaker enclosure. The speaker enclosure comprises a housing having a fracture zone defining a perimeter, the perimeter defining a slave box inside the perimeter and a master box. The fracture zone being configured to fracture to separate the master and slave boxes and to allow the slave boxto collapse into the master box such that a dimension (e.g. the height) of the speaker enclosure reduces after the fracture zone has been fractured.

In the exemplary embodiments, the fracture zone forms a perimeter groove. The perimeter groove is open in a plane perpendicular to the reduced dimension (herein the height of the speaker enclosure, by way of example, the height being arranged in the anticipated load direction). That is, if the boxed loudspeaker is installed so that the height of the speaker enclosure is arranged horizontally, for instance in the direction of forward travel, the permitter grove is open in a vertical plane. Here, the perimeter groove forms a weakness in a material of the speaker enclosure, for instance a relatively thin wall permitter, through which the speaker enclosure is encouraged to fail when an impact force is transmitted between the respective first and second portions on the master and slave boxes. The speaker enclosure is suitably moulded from a plastic and by having the perimeter groove open in a in a single plane, the part can still be de-moulded. To achieve a simultaneous fracture along the entire perimeter, suitably the perimeter groove lies in a single plane. However, design constraints and considerations of the speaker enclosure mean the perimeter groove may lie in one or more planes and part of the perimeter groove may transition between planes. However, the perimeter groove can still be open in a plane perpendicular to the height (e.g. open in a single plane). That is, the perimeter groove may have a base of the groove that is spaced from a surrounding area and the base of the groove is spaced from the surrounding area in a height direction along the entirety of the perimeter groove. In the exemplary embodiments having a perimeter groove, the groove may have a consistent groove cross section. The groove cross-section suitably has a base that is spaced from a surrounding area. The groove-cross section suitably has side walls that extend between the surrounding area and the base.

The groove side walls suitably extend at an angle to the height direction, for instance, the side walls may form a ‘V’ or TJ’ shaped cross-section or a combination of both. In some instances, the groove cross- section is symmetrical about a centre line of the cross-section. For instance, in a ‘U’ shaped groove, the base is substantially parallel to the surrounding area, and in a ‘V’ shaped groove, the base is the apex between the two sidewalls.

In the exemplary embodiments, the speaker enclosure is formed from a housing having a wall-thickness. As explained, in exemplary embodiments, the fracture zone is formed by a groove in the surface of the housing, such that the groove extends into the wall-thickness. Suitably, the groove maintains a minimum thickness suitable to withstand internal validations such as shaker profiles at different temperatures. For instance, a minimum mouldable thickness not smaller than 0.8mm has been found to be sufficient. Therefore, in exemplary embodiments, the groove may provide a localised reduction in wall thickness of greater than 50% or greater than 55% or greater than 60% or up to75%. In the example of a perimeter groove, the perimeter groove is open to one surface of the housing. In some exemplary embodiments, the fracture zone further comprises a second groove. That is, the perimeter groove if formed from a first perimeter groove a second perimeter groove. Flere, the second groove suitably opposes the first groove. That is, the second groove is formed in the opposite surface of the housing’s thickness. For instance, the second grove may be a second perimeter groove that substantially opposes the first perimeter groove. The second perimeter groove being open in the same plane as the first permitter groove (e.g. perpendicular to the height direction) but in an opposed direction. In the exemplary embodiments comprising a second permitter groove, the second perimeter groove may mirror the first perimeter groove. For instance, in the case of the first and second perimeter grooves having a ‘V’ shaped cross-section, the apex of the sidewalls of the first permitter groove may be aligned in a plane perpendicular to the height direction. That is, the shortest distance between the respective apex’s may be arrange in the height direction. Alternatively, in a preferred exemplary embodiment, the first and second perimeter grooves are off-set from each other. That is, in a cross-section through the housing’s wall-thickness the shortest distance between the respective grooves is angled to the height direction. Remembering that the height direction is the direction between the first and second portions that the impact force is applied, by offsetting the first and second perimeter grooves so that the shortest distance between the grooves is angled to this direction, the groove can be configured to break under shear force conditions and it has been found that producing a shear through the speaker enclosure has achieved good instantaneous and continuous fracture of the speaker enclosure at low speed impacts, without unintended failing from vibrational forces or the like.

In the exemplary embodiments including a perimeter groove, the perimeter groove is substantially the same size as the perimeter of the slave box. Flowever, in some embodiments, the perimeter groove is longer than the perimeter of the salve box. For instance, the perimeter groove may include an extension groove. The extension groove suitably extends from the perimeter groove such that the extension groove does not define the separation between the slave box and master box, but rather extends in one of the boxes only (for instance, suitably the master box). Extension grooves can be arranged to dissipate the energy accumulated during the impact and release it in the master box without any performance impact based on the design and shape of the speaker enclosure.

In exemplary embodiments wherein the fracture zone (e.g. perimeter groove) is arranged in multiple planes with portions of the fracture zone extending between respective planes to form the periphery separating the master and slave boxes, the housing forming the speaker enclosure can suitably include means for initiating fracture at different times or forces of the impact. For instance, portions of the fracture zone forming a radius or two areas lying in different planes can break at different forces or times so that the fracture through the fracture zone is not instantaneous (i.e. the fracture zone breaks in some areas but not others that risks transferring force). In some embodiments, the means for initiating fracture at different times includes protrusions from the housing in the height direction. Here, the protrusions can be used to cause areas of the fracture zone that are harder to break than other areas, to be engaged earlier in the impact than the weaker areas. Thus, some deformation of the speaker enclosure or part of the vehicle pressing the speaker enclosure is required before the weaker areas are engaged to initiate the fracture. In other exemplary embodiments, the means for initiating fracture at different forces includes ribs in the housing. For instance, the means for fracturing the fracture zone may comprise at least one rib. That is a first rib. The means for fracturing the fracture zone comprising at least one rib may comprise a plurality or series of ribs. That is, a second rib and or third and further ribs. Here, the rib or series of ribss can be used to strengthen weak areas of the housing in order to avoid unwanted deformation of non-target areas or to increase the absorption of the energy applied by the impact at the fracture zone. In other exemplary embodiments, the means for initiating fracture at different forces may include a notch forming element. The notch forming element is suitably a relatively rigid protrusion from the housing that can initially move with deformation of the speaker enclosure or part of the vehicle pressing the speaker enclosure and arranged to extend from the housing at or near to the fracture zone. The notch forming element can aid in starting the crack at relatively hard areas of the fracture zone by applying momentum in a smaller area resulting in higher compression force at a small surface which is considered to be hard to break. The first crack assisting the rest of the plastic break or shear. It will be appreciated that the loudspeaker enclosure may be designed with one or more of the means for initiating fracture as appropriate depending on the design of the speaker enclosure and the identified relatively hard and weak areas and in order to initiate a simultaneous fracture through the fracture zone.

In the exemplary embodiments, the master box includes a speaker unit. The speaker unit is mounted in the master box, and has a diaphragm arranged to vibrate to produce an audible sound. The diaphragm has a listener side exposed to an exterior of the speaker enclosure. The opposed side of the diaphragm to the listener side is enclosed within the speaker enclosure. Suitably the speaker unit includes a motor system, for instance an electromagnetic motor, for driving the diaphragm to vibrate. Suitably, the diaphragm has a cone shape and is designed to be lightweight and with the surface area of the diaphragm maximised. The diaphragm may be formed from pressed paper or the like as is known in the art. As explained, the speaker unit is mounted to the housing in an area of the master box. Here, the diaphragm may be sealed within a diaphragm aperture in the housing. For instance, the diaphragm may be suitably sealed to the speaker enclosure around a periphery of the diaphragm and diaphragm aperture. In some exemplary embodiments wherein the diaphragm aperture is not arranged in a plane substantially perpendicular to the height direction (i.e. the direction the load is applied), suitably, the speaker unit is mounted to a portion of the housing defining the master box that is not arranged to be impacted. For instance, in an AVAS application where the boxed loudspeaker is mounted in a bumper, the boxed loudspeaker may be installed to the vehicle with a portion of the speaker enclosure having the speaker unit projecting from the underside of the bumper. Thus, in an impact on the bumper, the bumper collapses to absorb the energy of the impact transferring the force to the salve box, which collapses into the master box without requiring the protruding portion to also collapse.

For the avoidance of doubt, the relative terms: above, below, upwards, downwards, vertical, horizontal and the like terminology; are provided in relation to the intended orientation of the boxed loudspeaker.

For instance, the terms reference the orientation of the boxed loudspeaker when installed in a vehicle. It will be appreciated that the installation orientation of a boxed loudspeaker is generally readily discernible. Moreover, the examples herein are given whereby he boxed loudspeaker is installed such that the height of the loudspeaker enclosure is aligned with the direction of the anticipated impact to be absorbed. It will be appreciated that references to the height of the loudspeaker are therefore intended to reference the anticipated direction of impact.

The speaker enclosure is formed from a housing. Suitably, the housing can be moulded, for instance injection moulded. Here, the speaker enclosure may be formed from two shell pieces. The shell pieces can be suitably joined via vibration / friction welding or other welding techniques before the speaker unit is installed. Suitably, one of the shell pieces includes the fracture zone forming a perimeter and the slave box is defined inside the perimeter and a portion of the master box is defined outside the perimeter, with the remainder of the housing that forms the master box comprising the other shell piece. The other shell piece suitably contains the mounting point and is preferably flat and rigid in order to distribute the load equally through the mounting points resulting in as low as possible load transferred to the inner panel of the BIW. Consequently, according to a further aspect, there is provided a shell piece for forming a speaker enclosure, the shell piece having a fracture zone forming a perimeter and the slave box is defined inside the perimeter and a portion of the master box is defined outside the perimeter.

It will be appreciated that according to further aspects, there is provided a vehicle having the exemplary boxed loudspeaker installed. Suitably, the housing of the speaker enclosure comprising the master box includes mounting locations via which the boxed loudspeaker is installed to the vehicle. In the exemplary embodiments, the housing is formed from a first shell piece comprising the fracture zone and a second shell piece including the mounting portions. The shell pieces are joined together, for instance via friction welding etc..

According to a further aspect, there is provided a method of installing the exemplary boxed loudspeaker in a vehicle, the method comprises installing a housing of the loudspeaker enclosure between first and second portions of the vehicle intended to collapse to absorb energy in the event of an impact. The method comprises arranging a fracture zone in the housing to define a perimeter defining a slave box inside the perimeter and a master box. The method further comprising causing an impact force to be imparted between first and second portions of the housing on respective master and slave boxes, the impact force causing the fracture zone to fracture about the periphery and to collapse the slave box into the master box.

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

Summary of the Figures

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

Figure 1 shows a view representation of a boxed loudspeaker;

Figure 2 shows schematic representations of a top view and a side view of a shell piece for forming a housing of a boxed loudspeaker;

Figure 3 shows a perspective view of a boxed loudspeaker of Figure 1 installed on a vehicle;

Figure 4 shows a schematic front view representation of Figure 3;

Figure 5 shows a perspective view of a housing for a boxed loudspeaker after a force representing a low speed impact is applied with a slave box collapsed into a master box;

Figures 6 to 8 show perspective representations of exemplary groove shapes;

Figure 9 shows a series of representations of portions of a housing defining hard to break areas;

Figure 10 shows a perspective view of a housing after a force is applied where a hard to break area remains unbroken;

Figures 11 to 13 shows perspective views of a shell piece for forming a housing of a boxed loudspeaker having ribs on the inner and outer surfaces;

Figures 14 and 15 show perspective representations of a housing for forming a boxed loudspeaker having elements to aid the instantaneous fracture between the master and slave boxes; and

Figure 16 shows a top representation of a shell piece for forming a housing of a loudspeaker enclosure. Detailed Description of the Invention

Aspects and exemplary embodiments 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.

Figure 1 shows an exemplary embodiment of a boxed loudspeaker 10. The boxed loudspeaker 10 comprises a loudspeaker enclosure 20 and a speaker unit 30. The loudspeaker enclosure 20 comprises a housing 21 having a diaphragm aperture 22. The speaker unit is arranged in the housing 21 with respect to the diaphragm aperture 22. The speaker enclosure further includes a cover 23 that is secured to the housing 21 over the diaphragm aperture 22, for instance the cover is a protective mesh or the like as is known in the art.

As herein described, the housing 21 is suitably formed from a first shell piece suitably joined to a second shell piece. The shell pieces can be suitably joined, for instance, by friction welding or the like to form a single housing 21 defining a closed, hollow box in which the speaker unit is housed. As shown in Figure 1 , suitably the first shell piece (shown in Figure 1 as a lower or bottom shell piece) includes mounting points for mounting the housing to the vehicle. The second shell piece (shown in Figure 1 as the upper or top shell piece contains the fracture zone).

Also as is known in the art, the speaker unit 30, is shown suitably as a dipole loudspeaker comprising a motor system (not shown) and a diaphragm 34. It will be appreciated that the speaker unit 30 comprises further components as is known, for instance suspension elements etc. Indeed, it is envisaged that the exemplary boxed loudspeaker embodiments described herein will be suitable for use with known speaker units 30. That is, the known speaker units, will not have to be specifically adapted beyond general workshop variations. Whilst a detailed explanation of the speaker units 30 (e.g. dipole loudspeaker) is not thought necessary, in brief, the diaphragm 34 and motor system may take various forms as is known in the art.

For instance, in exemplary speaker units, the diaphragm may be a single (monolithic) piece of material. The material forming the diaphragm is suitably lightweight, for instance, the material suitably has a density of 0.5 g/cm3 or less. In exemplary embodiments, the material is extruded polystyrene or extruded polypropylene or similar. In some examples, the diaphragm is covered by a skin, e.g. to protect the diaphragm. Suitably, the skin is formed from paper, carbon fibre, plastic foil, or the like. In some exemplary embodiments, the diaphragm includes several pieces of material attached together. For instance, the diaphragm includes several pieces of material attached to each other by glue. Here, the diaphragm may include a first cone and a second cone being first and second pieces attached together, wherein suitably the first and second cones are glued back to back to attach each cone to the other cone. Here, a front surface of one of the cones forms the first radiating (e.g. front) surface and a back surface of the other cone provides the second radiating (e.g. back) surface. In one exemplary embodiment, the first and second cones are formed from paper. The diaphragm may further include one or more cut-outs in one of the radiating surfaces (preferably the second radiating surface), wherein each cut-out is configured to have a respective rigid supporting element extend through it when the speaker unit is in use. This may allow the speaker unit to have a lower profile in the height direction of the diaphragm. Suitably, the diaphragm is watertight.

Further, in the exemplary embodiments the motor system suitably includes an electromagnetic drive unit that includes a magnet unit configured to produce a magnetic field, and a voice coil attached to the diaphragm. In use, the voice coil may be energized (have a current passed through it) 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. The magnet unit may include a permanent magnet. The magnet unit may be configured to provide an air gap, and may be configured to provide a magnetic field in the air gap. The voice coil may be configured to sit in the air gap when the diaphragm is at rest. Such motor systems are well known. The magnet unit may be located in front of the second radiating surface of the diaphragm.

Referring back to Figure 1 there is shown an speaker 30, such as a dipole loudspeaker, mounted in the housing 21. The dipole loudspeaker 30 comprises a diaphragm 34 having a first radiating surface 36 and a second radiating surface. The first surface 36 is shown as a front surface, or a listener side, which faces outwards through the diaphragm aperture 22, and the second surface is the opposed rear surface, or isolated surface which faces into the housing 21 . The drive unit is configured to drive the diaphragm 34 to produce audible sound as is known in the art. Consequently, in operation, the motor system is operational to drive the first radiating surface 36 to emit a sound and the second surface to emit a response 180 degrees out of phase. This out of phase response is an anti-phase sound and if allowed to interfere with the sound from the first surface would act to cancel out and compromise the sound. Consequently, the second surface of the diaphragm is isolated by being housed in the housing 21 of the speaker enclosure.

As shown in Figure 1 , the housing 21 includes mounting features 25 for mounting the housing to a vehicle. In the exemplary embodiment shown in Figure 1 , the mounting features are formed on one shell piece that is joined to a second shell piece having the fracture zone. The first shell piece can suitably be substantially flat. As explained above, vehicles include boxed loudspeakers at various locations for musical purposes to the interior as well as to provide artificial noise to the exterior. The exemplary boxed loudspeakers can be adapted for any purpose and are ideally suited for applications where the boxed loudspeaker is installed in-between inner and outer portions where it is necessary to restrict the transfer of an impact from one portion to another. As shown in the Figures, a suitable example is in an Acoustic Vehicle Alerting System (AVAS). As will be understood, in an AVAS the boxed loudspeaker 10 is mounted to a vehicle 40. Referring to Figure 3, the loudspeaker 10 is typically installed in a front 42 and / or rear area of the vehicle so that it is in proximity to any pedestrians in a direction of travel of the vehicle. As will be appreciated, the boxed loudspeaker is located close to the bodywork of the vehicle so that the listener surface of the diaphragm is located in a position near to the pedestrian. Common convenient free spots for locating the boxed loudspeaker 10 are under the radiator and headlights / taillights.

Furthermore, As shown in Figures 3 and 4, it is common to open holes in an under-body panel or bumper. Here, the boxed loudspeaker might be arranged so that the listener side of the diaphragm is arranged within the hole, or the hole might be an acoustic opening such as mesh or a perforated area. In any event, the boxed loudspeaker is installed on the vehicle 40 so that the listener side of the boxed loudspeaker’s diaphragm is exposed to the external environment of the vehicle. Moreover, one or more boxed loudspeakers may be installed on a vehicle at spaced locations.

Referring specifically to Figures 3 and 4, the boxed loudspeaker is suitably shown as being installed to the vehicle behind a bumper 42 of the vehicle. Here the mounting features are fixed to an inner portion of the vehicle and the bumper is installed over the boxed loudspeaker. The speaker unit is shown as protruding from underneath the bumper. In the event the vehicle hits an object, the bumper is designed to crumple to absorb the impact, even at low speeds. As will be appreciated, as the bumper crumples, the impact is transferred to the housing of the boxed loudspeaker. Because the housing is relatively rigid, the housing can transfer the impact to the inner portion of the vehicle that can cause undesirable deformation to the inner portion of the vehicle. Consequently, as shown in Figure 2, the housing of the boxed loudspeaker of the exemplary embodiments is provided with a fracture zone 50.

The fracture zone is shown as defining a perimeter. The perimeter separates the housing 21 into a master box 60 and a slave box 70. The slave box is defined to the inside of the perimeter. The Master box includes the diaphragm aperture 22 and a mounting and installation space for the speaker unit. The mounting for attachment to the vehicle is also defined on the master box. The master box includes a first portion and the slave box a second portion spaced in a height direction and between which the force from the impact is applied. The height direction is shown by arrow F and is the direction of the expected impact. The first portion on the master box is shown as being substantially flat and is in contact with an inner portion of the vehicle when installed. The second portion is also substantially planar and parallel to the first portion. The second portion comes into contact with the second portion of the vehicle, for instance the bumper, as it collapses in the event of an impact. It will be appreciated that as herein described, the housing 21 is suitably moulded in two shell pieces and the hollow enclosure obtained by joining the shell pieces together.

As will be appreciated and explained herein, the fracture zone 50 is designed to fracture in the event that a threshold force is applied between the first and second portions. Because the fracture zone defines a perimeter in a vertical plane, when the housing is separated into a master box and slave box by the fracture zone separating, the slave box is able to collapse into the master box in order to reduce the one dimension of the speaker enclosure (herein, by way of example, the height of the housing) and therefore absorb the impact and reducing the transfer of the load to the inner panel of the BIWvia the first portion. As will be appreciated, in order to reduce the height, each of the master box and slave box includes a portion of the side walls of the housing. In particular, the maximum reduction in height can be achieved by locating the perimeter to separate the housing around a mid-point in the height between the first and second portions of the housing 21. Here, when the slave box collapses into the master box, the distal perimeter of the slave box (formed by the fracture along the fracture zone) abuts an inside of the master box and the height of the housing has been reduced by around 50%.

Figure 5 shows the housing after a force exceeding the threshold force has been applied between the first portion and second portion of the housing and sufficient to fracture through the fracture zone 50. The housing has been separated into the master box and the slave box and the slave box has collapsed into the master box to reduce the height of the housing. The reduction in the height of the housing allows the impact to be absorbed and reduces the transfer of force to the inner portion of the vehicle.

As will be appreciated, the boxed loudspeaker 10 has a defined installation orientation, defining a vertical and horizontal direction. References therefore to vertical and horizontal or the like relative orientation terms are to the boxed speaker’s intended installation orientation, for instance, when installed in a vehicle. Generally, the speaker 10 may be intended to be installed with a plane of the diaphragm being installed in either a vertical or horizontal plane. Or at least one wall or surface of the loudspeaker’s housing is intended to be installed in a horizontal or vertical plane. In these circumstances, as appropriate, references to vertical and horizontal or the like relative terms may be provided in relation to the features intended to be mounted in a horizontal or vertical plane. In particular, it is generally clear from a loudspeaker the intended mounting orientation. It will be appreciated however, that the exact shape of the housing may be influenced by the particular application, and in particular, any constraints on the shape of the housing dictated by the space in which the loudspeaker 10 is to be assembled or fitted. Moreover, the boxed loudspeaker has been described with reference to an AVAS system shown with the boxed loudspeaker installed with the loudspeaker enclosure extending in a length (vertical direction), a width (horizontal direction) and therefore having a height in a direction of travel, and therefore expected direction of impact. However, as other installation orientations are envisaged, the reference to height is to the intended direction of the impact rather than the geometry of the housing.

Figures 6 to 8 show exemplary fracture zones for initiating the fracture through the housing to separate the housing into the master and slave boxes. The fracture zone is formed from an integral material having a generally consistent wall-thickness. For instance, the housing may be formed form a plastic and may be moulded, for instance injection moulded. The wall-thickness may therefore be between 2mm to 3mm thick, but the exact wall-thickness will be defined by the specific implementation. As is known in injection moulding, the minimum wall-thickness may be around 0.8mm and it will be appreciated that the fracture zone comprises a minimum wall-thickness to initiate the fracture through. The minimum wall- thickness can be created with a groove. For instance, the fracture zone may suitably be formed by a perimeter groove. The perimeter groove may have a simple notch shape-cross section. For instance, the groove cross-section may be a V’ shape or a ‘U’ shape cross-section. As shown in Figures 6 to 8, both the ‘V’ shape and ‘U’ shape cross-sections 70 have angled sides 72, 74 and a base 76. The sides can be angled to the surrounding areas 78 suitably between 110° and 160°. The base is spaced form surrounding areas 78 of the wall-thickness. In the ‘V’ shaped cross-section, the sides meet at an apex and the base is the apex. Suitably, the sides are shown meeting at the apex to form a 90° angle, but it is envisaged, the angle may suitably be between 60° and 120° or 70° and 110° or 80° and 110°. It is envisaged the angle will be preferably be suitable for injection moulding techniques. In the ‘LT shaped cross-section the sides meet at a base being substantially parallel to the surrounding area. Figure 8 shows a combination of a ‘U’ shaped cross-section and a ‘V’ shaped cross section. Here, a secondary ‘V’ shaped groove is formed in the centre of the base of the ‘U’ shaped groove. In the embodiments with the fracture zone having a single groove, the groove can be installed in the inner or outer surface of the housing.

In Figures 6 and 7 the fracture zone 50 is shown as being formed from two perimeter grooves, with a perimeter groove formed in the outer and inner surface of the housing. In Figure 6, the grooves in the inner and outer surfaces are shown as being in register. That is, the grooves are substantially aligned. In Figure 6, the grooves are shown as having ‘V’ shaped cross-sections and the grooves are registered with the apex’s of the inner and outer surface grooves being aligned across the wall-thickness. Here, the minimum distance between the grooves is between the apex’s which lie in the thickness direction (i.e. the direction of impact). A preferable fracture zone is shown in Figure 7, where the grooves in the inner and outer surfaces are off-set. Here, apexes of the inner and outer surface grooves are not aligned such that the shortest distance between the grooves is angled to the height direction. The shortest distance may be between the apex of each groove or between an apex and a side wall. But in either case, the shortest distance is angled to the height direction, which is believed to generate a shear force in the material of the fracture zone when the impact force is applied. It has been found that the shear force generates an improved fracture initiation and continuous and instantaneous nature of the failure through the fracture zone.

In each of the exemplary fracture zones comprising a perimeter groove, the groove cross-section is open in the height direction. In a simple embodiment, the perimeter groove may lie on a single plane, the groove being formed in the wall of the housing and being open (e.g. with the base spaced from the surrounding area in the height direction) in the height direction. However, as herein described, in the case of a complex perimeter groove lying and transitioning between multiple planes, the groove is arranged to remain open in the height direction around the entire periphery. This enables the groove to be moulded, for instance injection moulded, without complex demoulding solutions as well as allowing the fracture zone to be activated consistently in the height direction.

Due to the design considerations and constraints of the boxed loudspeaker application, the speaker enclosure may suitably have a complex shape and the fracture zone defining a perimeter can be arranged on multiple planes. That is, as shown in Figure 9, part of the fracture zone may lie along a first plane around a mid-point of the height direction of the housing, and a second part (shown as being near the accommodation area for the speaker unit) may lie on a second plane close to the second portion that contacts the outer portion of the vehicle. The fracture zone transitions between the two planes along a sloped wall of the housing. As explained, in the examples having a perimeter groove, the groove remains open in the height direction along the sloped wall as well as the walls lying in the first and second planes, at least. Due to the complex arrangement of the fracture zone, various regions of the fracture zone are formed that have a relatively hard to break portion compared to others. For instance, as highlighted in Figure 9 around radius’s or the portions on different planes. The harder to break areas prevent the fracture zone from fracturing continuously and instantaneously around the perimeter separating the housing into the slave box and master box. For instance, as shown in Figure 10, the housing is shown where the fracture zone as initiated in the portion along the first plane, but has not initiated in the portion along the second plane and sloped wall. Thus, the slave box is not entirely detached from the slave box and remains hinged thereto along the un-fractured part of the fracture zone. Rather than collapsing into the master box, the slave box hinges retaining the possibility of transferring the impact force to the inner portion of the vehicle. Moreover, when the slave box begins to hinge, the impact force is no longer transferred through the attached fracture zone reducing the force initiating the fracture in the un-detached fracture zone.

To assist the continuous and instantaneous fracture through the fracture zone 50, housing can include features to assist some areas to fracture at an earlier time in the impact or to strengthen some areas to delay the fracture time of those areas. For instance, as shown in Figures 11 to 13, ribbing 80can be provided on the inside or outside surfaces of the housing. The ribbing provides localised strengthening to the areas of the housing. For instance, the ribbing is a series of ribs 82 that extend in the height direction and that act to resist deformation when an impact force is applied and therefore strengthen the local area to assist in initiating the fracture through the fracture zone at the same time as other areas. Additionally or alternatively, as shown in Figure 14, protrusions 84 can be provided on the housing to cause local areas to be engaged by the outer portion of the vehicle before other areas. For instance the protrusions on the top of the housing’s second portion on the slave box project in the height direction so that the protrusions engage with the outer portion of the vehicle before the second portion and therefore pre-load the fracture zone near the protrusions to encourage the hard to break area to fracture at the same time as the other areas of the fracture zone. Figure 15 shows a feature comprising a combination of a protrusion and a rib. The feature 86 is a notch initiation feature. The notch initiation feature protrudes towards the outer portion of the vehicle to engage the outer portion at an early stage of the impact. Moreover, the notch initiation feature is suitably a rib extending in the height direction. The rib is elongate and relatively rigid and extends from near a hard to break portion of the fracture zone. The combination of the protrusion and rib causes the notch initiation feature to move during an early stage of the impact and the momentum of the movement causes a fracture initiation force at the hard to break area.

Furthermore, referring back to Figure 1 , the fracture zone 50 is shown as having an extension portion. That is, in addition to forming the perimeter, an extension fracture zone 51 is formed. The extension fracture zone 51 extends through the portion of the housing defining the master box. The extension fracture zone does not separate the housing into the slave box and master box, but rather can be used to assist in the fracturing of the perimeter portion. It is understood that the extension zone 51 assists in releasing stress accumulation.

The design of the fracture zone and housing using the initiation features an extension zones can be used to balance the loading during the impact to assist in the continuous and instantaneous fracture through the fracture zone.

The housing 21 of the loudspeaker enclosure, as mentioned, can be formed from fibre filled polymers that are injection moulded. It will be appreciated that in order to injection mould a hollow enclosure, the housing 21 , as herein described, can be formed from a plurality of shell pieces fixed together. For instance, as shown in Figure 16, the housing 21 is suitably fabricated from a first shell piece 24. The first shell piece is suitably moulded and intended to be fixed to further shell pieces to form the hollow enclosure. The first shell piece 24 includes the diaphragm aperture 22 and the fracture zone 50. The speaker unit can be installed to the first shell piece 24. Subsequently, a further shell piece (e.g. second shell piece) can be affixed to the first shell piece to enclose the speaker unit and to firm the housing 21. The further shell piece can be welded or glued or otherwise suitably affixed to the first shell piece. Figure 1 shows the first shell piece fixed to the second shell ;piece to form the housing 21 . Suitably, the further shell piece (e.g. the second shell piece) is substantially planar and include the mounting locations to affix the housing to the vehicle.

There is therefore provided a boxed loudspeaker having a housing arranged to resist the transfer of load from an outer portion of a vehicle to an inner portion in the event of an impact, and in particular a low speed impact. The boxed loudspeaker has a fracture zone that initiates a fracture through the housing to sperate the housing in to a master box and a slave box. Both the master box and slave box have portions of the housing’s side wall in the height direction such that, when separated through the fracture zone, the slave box can collapse into the master box to reduce the dimension of the housing in the height direction and to absorb the impact and resist transfer of the load to the inner portion of the vehicle to which the housing is mounted. The housing and fracture zone can be designed to assist the continuous and instantaneous fracture through the fracture zone. Accordingly, an improved housing for a boxed loudspeaker is provided that can reduce the transfer of load across the housing from a low speed impact. Advantageously, it has been found that by arranging the fracture zone to fracture through a shear force by off-setting a perimeter groove in an outer surface with a corresponding perimeter groove in an inner surface, a good balance can be achieved for the force required to fracture the fracture zone.

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.

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.

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.

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

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%.