SPEAKER

Abstract

The present invention provides a loudspeaker assembly for use on the outside of a vehicle. The diaphragm and surround are formed of a single piece of material, the material comprising a single layer woven fabric of orthogonal, woven fibers and a thermoset resin.

Claims

1.-17. (canceled)

18. A loudspeaker assembly for use on the outside of 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 assembly includes a frame from which the diaphragm is suspended by at least one suspension; wherein the at least one suspension includes a surround which is located at the perimeter of the diaphragm; and wherein the diaphragm and surround are formed of a single piece of material, the material comprising a single layer woven fabric of orthogonal, woven fibers and a thermoset resin.

19. A loudspeaker assembly according to claim 18, wherein the longest dimension of the surround and diaphragm unit in a direction perpendicular to the movement axis is D_clamp and is in the range 50 to 200 mm.

20. A loudspeaker assembly according to claim 18, wherein the material of the diaphragm and the surround has a Young's modulus in the warp/weft direction in the range 2 to 15 GPa and a Young's modulus at 45? to the warp/weft direction in the range 2 to 10 GPa; and wherein the thickness of the material of the diaphragm and the surround is in the range 0.03 to 1 mm.

21. A loudspeaker assembly according to claim 18, wherein the material of the diaphragm and the surround has a tensile strength in the warp/weft direction in the range 75 to 300 MPa and a tensile strength at 45? to the warp/weft direction in the range 50 to 200 MPa

22. A loudspeaker assembly according to claim 18, wherein the diaphragm includes a cone-shaped portion which is substantially in the shape of an open cone and has a cone opening angle in the range 60? to 160?.

23. A loudspeaker assembly according to claim 22, wherein the drive unit comprises a voice coil positioned at the tip of the open cone of the cone-shaped portion, and having a longest dimension D_VC in a direction perpendicular to the movement axis, wherein D_VC is in the range 18 to 50 mm and the ratio of D_clamp to D_VC is 2 or more.

24. A loudspeaker assembly according to claim 23, wherein the diaphragm has a shaped portion which is adapted to engage the voice coil.

25. A loudspeaker assembly according to claim 22, wherein the diaphragm further comprises a dust cap portion on the front face of the diaphragm covering the tip of the open cone of the cone-shaped portion.

26. A loudspeaker assembly according to claim 18, wherein the surround comprises a corrugation which extends around the perimeter of the diaphragm; the surround having a longest dimension D_d in a direction perpendicular to the movement axis measured between points at the peak of the corrugation in the forwards direction, the ratio of D_d to D_clamp being 0.8 or more.

27. A loudspeaker according to claim 26, wherein the corrugation has a curved cross section in a cross section parallel to the movement axis, the curve being a section of a circle; the corrugation being tangentially connected to the diaphragm.

28. A loudspeaker assembly according to claim 26, wherein the surround comprises at least a first corrugation, a second corrugation and a third corrugation, each of which extend around the perimeter of the diaphragm, wherein the first corrugation is located radially outwards of the second corrugation and the second corrugation is located radially outwards of the third corrugation.

29. A loudspeaker assembly according to claim 18, wherein the surround includes a mounting portion at the perimeter of the surround, wherein the surround is attached to the frame via the mounting portion.

30. A loudspeaker assembly according to claim 18, comprising a fixing member positioned between the surround and the frame and sized to fix the loudspeaker within the frame.

31. A loudspeaker assembly according to claim 18, further comprising a grille positioned in front of the front face of the diaphragm, with a rear face of the grille facing in the rearwards direction toward the front face of the diaphragm, and with a front face of the grille facing in the forwards direction; wherein the grille is configured to permit sound produced by the front face of the diaphragm to pass through the grille when the loudspeaker is in use, and to inhibit the ingress of water incident on the front face of the grille from entering into a space enclosed between the rear face of the grille and the front face of the diaphragm.

32. A loudspeaker assembly according to claim 18, which is configured for use in a road vehicle with the front face of the grille exposed to an outdoor environment.

33. An Acoustic Vehicle Alerting System (AVAS) comprising a loudspeaker assembly according to claim 18.

34. An Audible Warning Device comprising a loudspeaker assembly according to claim 18.

Description

SUMMARY OF THE FIGURES

[0073] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0074] FIG. 1 shows (a) piston-like movement of a cone shaped diaphragm relaxed (solid line) and actuated (dotted line); and (b) the non-piston-like, and uneven, movement of a flat membrane related (solid line) and actuated (dotted line).

[0075] FIG. 2 shows the output spectrum of a traditional two-horn vehicle alerting system.

[0076] FIG. 3 shows a schematic cross-sectional view of a loudspeaker assembly of the present invention, with the various longest dimensions mentioned herein labelled.

[0077] FIG. 4 shows an example output spectrum from a loudspeaker assembly of the present invention, at 2V on axis in infinite baffle, without a grille.

[0078] FIG. 5 shows an example output spectrum from a loudspeaker assembly of the present invention, at 8.5V on axis in infinite baffle, with a grille.

[0079] FIG. 6 shows an example output spectrum from a loudspeaker assembly of the present invention, at 2V on axis in infinite baffle, without a grille.

[0080] FIG. 7 shows a schematic cross-sectional view of a first loudspeaker assembly according to the present invention.

[0081] FIG. 8 shows a schematic cross-sectional view of a second loudspeaker assembly according to the present invention.

[0082] FIG. 9 shows a schematic cross-sectional view of a third loudspeaker assembly according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0083] 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.

[0084] FIG. 1 schematically illustrates the overarching concept of the present invention. FIG. 1(b) shows a simple membrane formed from a homogenous material (solid line) which moves when actuated to the dotted line position. The membrane bends, changing shape and affecting its response. These are disadvantageous speaker behaviours.

[0085] FIG. 1(a), on the other hand, shows the speaker motion enabled by the present invention. A loudspeaker assembly 1 is schematically illustrated. Here, the part corresponding to the homogenous membrane is the broadly conical (open cone)-shaped diaphragm 3, which is bounded by a surround 7 and has a dust cap 9 integrally formed at its centre. The dust cap stops dust, particles and other matter from getting into the voice coil former and entering the voice coil region.

[0086] Below mentions are made to the circumferential location of parts with respect to the diaphragm; of course, which might imply that the word applies only where the diaphragm is frustoconical. That is not the case. It will be appreciated that the diaphragm may have a different shape such that its perimeter is not circular. In that case, the skilled person can recognise that circumferential means the outer perimeter of the diaphragm; the outer circumferential direction being that outwards from the centre of the diaphragm no matter its perimeter shape.

[0087] Similarly, where parts are described as annular it will be appreciated that where the diaphragm is of a different shape those parts will not be annular but will have a shape to match the perimeter of the diaphragm.

[0088] When actuated by the drive unit 2, which includes a voice coil 8, the diaphragm and dust cap move to the dotted line position, together and in phase: this is piston-like movement as described herein. The surround 7, which here comprises a corrugation 10, a curved part of the diaphragm material which connects the diaphragm part to a flat annular mounting portion 15, flexes to permit this piston-like motion. The surround is part of a suspension 6, which broadly links the diaphragm 3 to a frame (not illustrated in FIG. 1(a); later the numeral 14 is used).

[0089] The piston-like movement occurs in a movement axis 4, with actuation of the voice coil and hence the diaphragm 3 moving it in what is herein referred to as a forwards direction, indicated by the arrow 5. Of course it will be appreciated that there will be some slight non-linear or deviated motion of the diaphragm during actuation; the axis 4 and direction 5 are merely indicative of the primary motion.

[0090] It can be seen that, at the point where the voice coil 8 meets the diaphragm 3, there is an annular notch/ledge 17 in the shape of the diaphragm. This lies between the diaphragm 3 and the dust cap 9. It permits easier placement and location of the voice coil 8 during manufacturing.

[0091] Further embodiments of speakers according to the present invention are illustrated in FIGS. 7-9.

[0092] Similar parts to those illustrated in FIG. 1 are given the same reference numeral.

[0093] FIG. 7 shows an embodiment wherein the suspension 6 is again includes a surround 7 having a corrugation 10, The surround 7 is attached to a frame 14 by the mounting portion 15, which is formed as a flat annular portion circumferentially outside the corrugation 10. The corrugation 10 is a curved portion of the material, effectively convex with respect to the forward direction 5 illustrated in FIG. 1; that is, the extended part of the curve extends in the forward direction 5.

[0094] The mounting portion 15 may be, for example, stuck to a ledge or platform part of the frame 14 by an adhesive. Alternatively it may be secured between the ledge/platform part 18 and a lid 19 of the unit.

[0095] Such a mechanical clamping may be used in combination with an adhesive to fix the mounting portion 15 and hence the surround 7.

[0096] The lid 19 can include a grille 16 for protecting the speaker assembly, for example protection from moisture ingress to permit outside usage.

[0097] In this embodiment, the voice coil 8 is suspended by a spider 20 which holds the voice coil within the frame. To work effectively there is not contact between the voice coil and the frame. The spider is sufficiently resilient to hold the voice coil by withstanding the forces that are generated when a current is passed through the voice coil. The spider also suspends the voice coil former and stops it form coming into contact with any other part of the loudspeaker when it is oscillating, or from touching any part of the loudspeaker when it is not oscillating.

[0098] The attachment of the diaphragm 3 to the frame 14 may be, as mentioned above, by a first mechanical clamp formed by a ledge or platform piece 18 of the frame 14 and a corresponding lip of the lid 19. To ensure the connection between the diaphragm and frame is flexible whilst being securely connected to the frame, there is provided the suspension 6 which has a surround 7, linking the diaphragm 3 to the mounting portion 15. This is attached to the diaphragm 3 at an internal end of the suspension 6 and to the mounting portion 15 at the outer end; that mounting portion 15 is held by the first mechanical clamp at its own outer end. This leads to a clamped boundary condition. The mounting portion 15, surround 7 and diaphragm 3 are all formed integrally of a single piece of material. The surround 7 can present as a corrugation or curved portion 10 at the outer periphery of the diaphragm portion 3; the mounting portion 15 can present as an annular flange at the outer periphery of the surround portion 7.

[0099] The properties of that material are discussed in detail herein. The material must have a certain thickness and Young's modulus, while the diaphragm has a certain size, to give the desired motion and hence acoustic response characteristics. For example, the material used in an embodiment such as that illustrated in FIG. 7 may be a glass fiber/epoxy resin composite material with a thickness of 0.08 mm.

[0100] The motor or drive system 2 in the illustrated embodiment utilises a ring magnet 21 to provide a magnetic field for movement of the voice coil 8; the magnet system is connected to the rear of the frame 14 by a yoke 22. The spider is connected to a washer part 23 of the magnet system. It will be recognised that such a drive system can be applied to a wide variety of different diaphragm/suspension/frame designs and configurations beyond those illustrated in FIG. 7.

[0101] The same is true of the grille 16 illustrated as part of the lid 19. As illustrated the grille follows the shape of the diaphragm and is therefore in the shape of a truncated cone (frustoconical). It has a flat portion corresponding to the location of the dust cap 9 and an angled portion corresponding to the location of the diaphragm 3. The grille 16 protects the diaphragm 3 and other internal workings from environmental factors; here, there is no line of sight through the grille from outside to the diaphragm. By presenting such a tortuous path for water droplets etc. the grille provides effective protection from water or debris.

[0102] By contrast, the grille illustrated in FIG. 8 is flat across the top of the frame 14. In this embodiment, the suspension 6 has a surround 7 including three corrugations, 11, 12 and 13, in place of the single corrugation 10 illustrated in FIG. 7. This arrangement features a corrugation 13 which is circumferentially outward of the diaphragm 3; that corrugation is convex in that it curves outwards from the frame towards the frontwards direction 5 (not illustrated). The next corrugation 12 is circumferentially outwards of the corrugation 13; it is convex in that it curves inwards towards the frame, away from the frontwards direction 5. This is followed in the circumferentially outward direction by a further corrugation 11, which is again convex. Outward of that is the mounting portion 15, a flanged portion equivalent to that illustrated and described earlier.

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

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

[0105] The drive system 2 illustrated for this embodiment utilises a disc magnet 24. It is mounted to the frame 14; in this instance, the frame 14 is itself mounted to a rear part 25 forming a cabinet (as is the spider 20). The rear part 25 can be attached to the frame by any means, such as an adhesive or mechanical bonding such as screw fixtures.

[0106] A third example embodiment is illustrated in FIG. 9. The drive system here is comparable to that of FIG. 8, with a disc magnet 24 mounted within the frame 14 (no rear part 25 is present in this embodiment). This is fixed to the rear wall of the frame 14; no spider is present in this embodiment.

[0107] The dust cap 9 is much as illustrated and explained for FIG. 7; a similar notch 17 is present to seat the voice coil 8.

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

[0109] The attachment of the surround 7 (having corrugation 10) to the frame 14 is different in this embodiment.

[0110] There is no mounting portion 15 provided here. Instead, the outer part of the corrugation 10 is wedged into the frame 14. Between the corrugation 10 (that is, the surround 7) and the inner wall of the frame 14 there is sandwiched one or more fixing members 15. The fixing members are sized to prevent movement of the outermost edge of the surround 7; thus again giving a clamped boundary condition. The fixing member(s) may be formed of a solid material or may be themselves adhesive to stick the surround in place. There may be a single fixing member 15 extending around the entire perimeter of the surround 7; alternatively, there may for example be four such members 15 positioned around the perimeter. Ideally a single fixing member extends around the entire perimeter to give the best mechanical clamping.

[0111] The material of the diaphragm, surround and dust cap in this embodiment is epoxy coated glass fiber with a thickness of 0.15 mm.

[0112] In order to test the response of the present speakers, output spectra shown in FIGS. 4, 5 and 6 were generated.

[0113] FIG. 4 shows an example frequency response from a loudspeaker assembly of the present invention having a 0.15 mm thick material forming the diaphragm, surround and dust cap, made from glass fiber and epoxy resin, at 2V on axis in infinite baffle, without a grille. It can be seen that despite the high resonance frequency of speakers of the present invention, the output at lower frequencies such as the 315 Hz ?.sup.rd octave band is still substantial (approximately 87 dB) due to the high loudspeaker sensitivity.

[0114] FIG. 5 shows an example frequency response and 2.sup.nd and 3.sup.rd order distortion components from a loudspeaker assembly of the present invention having a 0.15 mm thick material forming the diaphragm, surround and dust cap, made from glass fiber and epoxy resin, at 8.5V on axis in infinite baffle, with a grille. These Figures show that even at 8.5V the harmonic distortion remains moderate for low frequencies.

[0115] This allows the present loudspeakers to be used not only as vehicle warning horns but also as AVAS loudspeakers having to reproduce frequencies below its resonance frequency.

[0116] FIG. 6 shows an example frequency response from a loudspeaker assembly of the present invention with a 0.08 mm thick material forming the diaphragm, surround and dust cap, made from Kevlar dipped in phenolic resin, at 2V on axis in infinite baffle, without a grille. Despite the very thin membrane material the frequency response is substantially smooth within the decade ranging from 500 Hz to 5 kHz.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0121] 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 5 exclusion of any other integer or step or group of integers or steps.

[0122] 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%.