Abstract
A loudspeaker (1) comprising a diaphragm (2), a voice coil (10) mounted on the diaphragm (2) to move with the diaphragm (2), a chassis (4), and a spider (20) is disclosed. The spider (20) extends across a gap between the chassis (4) and the voice coil (10) and comprises a plurality of legs (36), each leg (36) extending radially across at least a portion of the gap. The diaphragm (2) is configured to move from a neutral position to an extended position. When the diaphragm (2) is in the neutral position the cross-sectional shape of each leg (36) follows a line which varies in height with respect to a reference plane, said line comprising first, second and third curves, the second curve being located in between the first and third curves. Either the first and third curves are convex and the second curve is concave, or the first and third curves are concave and the second curve is convex. Thus, the spider (20) may have legs (36) having an ‘m’ or ‘w’ shaped profile in at least one region of the leg (36).
Claims
1. A loudspeaker assembly comprising a diaphragm, a voice coil mounted on the diaphragm to move with the diaphragm, a chassis, and a spider, wherein the spider extends across a gap between the chassis and the voice coil and comprises a plurality of legs, each leg extending radially across at least a portion of the gap; the diaphragm is configured to move from a neutral position to an extended position and wherein when the diaphragm is in the neutral position the cross-sectional shape of each leg follows a line which varies in height with respect to a reference plane, the reference plane being a plane perpendicular to the direction of movement of the voice coil, said line comprising first, second and third curves, the second curve being located in between the first and third curves and the amplitude of the first and third curves is greater than the amplitude of the second curve and wherein either the first and third curves are convex and the second curve is concave, or the first and third curves are concave and the second curve is convex; and each concave curve extends from a local maximum to a local maximum via a local minimum and the amplitude of the curve is defined as the axial distance between said local minimum and the local maxima, and each convex curve extends from a local minimum to a local minimum via a local maximum and the amplitude of the curve is defined as the axial distance between said local maximum and the local minima, and in the case that the axial distance between the local maximum/minimum and each of the respective minima/maxima differs, the amplitude shall be taken as the larger of the two axial distances.
2. A loudspeaker assembly according to claim 1, wherein the line further comprises fourth, fifth and sixth curves, the fifth curve being located in between the fourth and sixth curves and wherein either the fourth and sixth curves are convex and the fifth curve is concave, or the fourth and sixth curves are concave and the fifth curve is convex.
3. A loudspeaker assembly according to claim 1, wherein a mass element is mounted on each leg such that the mass element can move relative to the rest of the spider, the mass element and the leg thereby forming a mass damping element configured to damp vibration of the spider.
4. A loudspeaker assembly according to claim 3, wherein the mass element is integrally formed with the leg.
5. A loudspeaker assembly according to claim 1, wherein the spider is made substantially of a plastic material, for example a thermoplastic polymer, for example Polyether ether ketone (PEEK).
6. A loudspeaker assembly according to claim 1, wherein each leg of the spider has the same cross-sectional shape when the diaphragm is in the neutral position.
7. A loudspeaker assembly according to claim 1, wherein the spider is integrally formed with the chassis.
8. (canceled)
9. (canceled)
10. A loudspeaker assembly according to claim 1, wherein the spider has an outer edge adjacent the chassis and an inner edge adjacent the voice coil, and comprises one or more intermediate members spaced apart radially from the inner edge and the outer edge; a first set of legs, each leg of the first set extending radially from an intermediate member towards the chassis; and a second set of legs, each leg of the second set extending radially from an intermediate member towards the voice coil.
11. A loudspeaker assembly according to claim 10, wherein the spider comprises a ring spaced apart radially from the inner edge and the outer edge, each leg of the first set extending radially from the ring towards the chassis, each leg of the second set extending radially from the ring towards the voice coil.
12. A loudspeaker assembly according to claim 11, wherein the ring is integrally formed with the rest of the spider.
13. A loudspeaker assembly according to claim 1, wherein the spider extends around the entire perimeter of the voice coil.
14. A loudspeaker enclosure including a loudspeaker assembly according to claim 1.
15. A spider suitable for use as the spider of claim 1.
16. A method of manufacturing a spider for a loudspeaker, wherein the spider comprises one or more radially extending legs, and the method comprises a step of shaping one or more legs of the spider to follow a line which varies in height above a reference plane, the reference plane being a plane perpendicular to the direction of movement of a voice coil of the loudspeaker, said line comprising first, second and third curves, the second curve being located in between the first and third curves and the amplitude of the first and third curves is greater than the amplitude of the second curve and wherein either the first and third curves are convex and the second curve is concave, or the first and third curves are concave and the second curve is convex; and each concave curve extends from a local maximum to a local maximum via a local minimum and has an amplitude defined as the axial distance between said local minimum and the local maxima, and each convex curve extends from a local minimum to a local minimum via a local maximum and has an amplitude defined as the axial distance between said local maximum and the local minima and in the case that the axial distance between the local maximum/minimum and each of the respective minima/maxima differs, the amplitude shall be taken as the larger of the two axial distances, to produce a spider having a target stiffness versus excursion response.
17. A method of manufacturing a spider according to claim 16, wherein the method includes modifying the amplitude and/or wavelength of said convex and/or concave curves from an original spider design to produce the target stiffness versus excursion response.
18. (canceled)
19. (canceled)
20. (canceled)
Description
DESCRIPTION OF THE DRAWINGS
[0096] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:
[0097] FIG. 1 is a schematic cross-sectional view of a loudspeaker in accordance with a first example embodiment of the invention;
[0098] FIG. 2 is a perspective view of the spider of the first embodiment;
[0099] FIG. 3 is a schematic view of a portion of a spider in accordance with a second example embodiment of the invention;
[0100] FIG. 4 shows a schematic view of a portion of a spider in accordance with a third example embodiment of the invention;
[0101] FIG. 5 shows a schematic view of a portion of a spider in accordance with a fourth example embodiment of the invention;
[0102] FIG. 6 shows a schematic view of a portion of a spider in accordance with a fifth example embodiment of the invention;
[0103] FIG. 7 shows a schematic view of a spider in accordance with a sixth example embodiment of the invention;
[0104] FIG. 8 shows a comparison of acoustic power vs frequency for the spiders of the second and sixth example embodiments;
[0105] FIG. 9 shows a schematic view of a portion of a spider in accordance with a seventh example embodiment of the invention; and
[0106] FIG. 10 shows a flow chart of an example method of manufacturing a spider.
DETAILED DESCRIPTION
[0107] FIG. 1 shows a cross-sectional schematic view of a loudspeaker 1 in accordance with a first embodiment of the invention. A cone-type loudspeaker diaphragm 2, is concentrically located within a chassis 4. An annular surround 6 extends from the outer perimeter of the diaphragm 2 to the inner edge of the chassis 4. A support 6 extends across a gap 8 between the diaphragm 2 and the chassis 4 at the front end of the diaphragm 2. A voice coil 10 is mounted to the rear end of the diaphragm 2 and extends rearwardly from the diaphragm 2 into a voice coil gap 12 formed between an annular magnet 14 and a central pole piece 16. An annular top plate 18 is located between the annular magnet 14 and the chassis 4. A spider 20 is attached to, and extends between, the voice coil 10 and the chassis 4. A dust cap 22 covers a gap 24 in the centre of the diaphragm 2. It will be appreciated that the present invention is concerned with the spider 20, and the shape and configuration of other elements of the loudspeaker, e.g. the shape and configuration of the diaphragm 2, support 6, chassis 4, magnet 14 and/or pole piece 16, may differ from that shown here. Additionally or alternatively, some elements shown here, for example dust cap 22 and/or top plate 18 etc. may be absent in other embodiments of the present invention.
[0108] FIG. 2 shows a perspective view of the spider 20 of the first example embodiment. The spider 20 comprises an outer ring 30 and an inner ring 32 (while referred to as a ring, it can be seen that ring 32 is closer to a polygon shape) and is made of Polyether ether ketone (PEEK). In other embodiments, the inner and/or outer ring may be only a partial ring. In other embodiments, different materials may be used. Six legs 36 are spaced equidistantly around the outer ring 30 and extend radially between the outer ring 30 and inner ring 32. In other embodiments more or fewer legs may be used, in some cases three legs may be sufficient. Each leg 36 has a length (in the radial direction) and a width (in the circumferential direction) very much greater than its thickness (in the vertical direction). Each leg 36 has a profile that varies with radial distance when viewed in cross-section. Each leg 36 comprises an outer attachment portion 38 and an inner attachment portion 40 via which the leg 36 is connected to the outer ring 30 and inner ring 32 respectively, both attachment portions 38, 40 having a different profile to the portion of the leg 36 immediately adjacent. Each leg 36 of the first embodiment is an ‘m’-shaped leg having a profile comprising two curves that curve in a first sense (that sense being convex with respect to the top side of the leg 36) with a curve that curves in a second, opposite, sense (that sense being concave with respect to the top side of the leg 36) located between them. The width of each leg 36 also varies with respect to radial distance along the leg, with a middle region of the leg 36b, being narrower than the regions 36a, 36c on either side. The middle region of the leg 36b is the concave region of the leg. In use, outer ring 30 is connected to the chassis 4 and inner ring 32 is connected to the voice coil 10.
[0109] FIG. 3 shows a portion of a spider 120 having an m-shaped leg, similar to the type shown in FIG. 2, in accordance with an embodiment of the invention. Elements that are similar as between FIG. 1 or 2 and FIG. 3 have been indicated in FIG. 3 using their reference numeral from FIG. 1 or 2 incremented by 100 (i.e. spider 20 in FIG. 1 or 2 is referred to as spider 120 in FIG. 3). Working from left to right, FIG. 3 shows a portion of the chassis 104 to which an outer ring 130 of the spider 120 is attached. An outer flange 138 connects the outer end of a leg 136 to the outer ring 130 and an inner flange 140 connects the inner end of the leg 136 to the inner ring 132 of the spider 120. The inner ring 132 is connected to a portion of the voice coil 110. A dashed line labelled A extends horizontally across FIG. 3 and denotes a neutral plane i.e. a plane perpendicular to the voice coil 110. A dashed line labelled B in FIG. 3 denotes the midline of the leg 136 (i.e. a series of points equidistant between the upper and lower surfaces of the leg). The height of the midline B varies with respect to the neutral plane A with radial distance between outer flange 138 and inner flange 140. In a first region 136a of the leg 136, the height increases to a maximum at a point 142a and then begins to decrease. In a second region 136b of the leg 136, the height decreases to a minimum at a point 142b and then begins to increase. In a third region 136c of the leg 136, the height increases to a maximum at a point 142c and then begins to decrease. The second region 136b is located between the first and third regions 136a, 136c and the shape of the leg 136 is smooth as it transitions between each region. Such a leg may be said to have two concave regions and a convex region when considered from above. The depth of the convex region (i.e. second region 136b) is less than the height of the concave regions (i.e. first and third regions 136a, 136c).
[0110] In FIG. 3, the height varies while the midline B remains above the neutral plane, in other embodiments, the height may vary while the midline B remains below the neutral plane. In yet further embodiments, the height may vary while the midline B crosses the neutral plane. In FIG. 3 the leg 36 may be described has having an ‘m’ shape. In other embodiments the shape of the leg may comprise two convex regions with a concave region between them (when considered from above). Such a leg may be referred to as having a ‘w’ shape.
[0111] The shape of the ‘w’ or ‘m’ or the combination thereof may be varied to provide a spider with a target stiffness vs excursion curve. Spiders with legs having such an ‘m’ or ‘w’ profile may provide better radial stiffness than a spider of the same material with legs having a simple roll profile. This in turn may allow a more flexible material to be used for the spider, while maintaining the ability of the spider to control and stabilise the voice coil. Such spiders may also be more compact that spiders with legs having a simple roll profile and providing the same range of movement of the diaphragm. The shape of the legs may also result in an improved stress distribution in the leg thereby increasing the fatigue life of the spider.
[0112] FIG. 4 shows a portion of a spider 220 in accordance with an embodiment of the invention. Elements that are similar as between FIG. 1 or 2 and FIG. 4 have been indicated in FIG. 4 using their reference numeral from FIG. 1 or 2 incremented by 200 (i.e. spider 20 in FIG. 1 or 2 is referred to as spider 220 in FIG. 5). FIG. 4 shows a leg in which the first, second and third regions 236a, 236b, 236c comprise concave, convex and concave curves respectively (i.e. a ‘w’ shape) and the leg 236 further comprises, when viewed from left to right, a fourth transition region 236d, and fifth, sixth and seventh regions 236e, 236f, 236g. The fifth, sixth and seventh regions 236e, 236f, 236g comprise convex, concave and convex curves respectively (i.e. a ‘m’ shape). The fourth transition region 236d comprises a substantially flat portion of the leg 236 that links the ‘w’ formed by the first, second and third regions 236a, 236b, 236c to the ‘m’ formed by the fifth, sixth and seventh regions 236e, 236f, 236g.
[0113] FIG. 5 shows a portion of a spider 320 in accordance with an embodiment of the invention. Elements that are similar as between FIG. 4 and FIG. 5 have been indicated in FIG. 5 using their reference numeral from FIG. 4 incremented by 100 (i.e. first region 236a in FIG. 4 is referred to as first region 336a in FIG. 5). The embodiment of FIG. 5 is similar to the embodiment of FIG. 4 with the exception that the first, second and third regions 336a, 336b, 336c comprise convex, concave and convex curves respectively (i.e. a ‘m’ shape). Thus, the leg 336 of the spider 320 comprises two ‘m’ shapes linked by a substantially flat transition portion 336d. The ‘m’ shape formed by the first, second and third regions 336a, 336b, 336c is smaller (having both a lower amplitude and shorter wavelength) than the ‘m’ shape formed by the fifth, sixth and seventh regions 336e, 336f, 336g.
[0114] FIG. 6 shows a portion of a spider 420 in accordance with an embodiment of the invention. Elements that are similar as between FIG. 4 and FIG. 6 have been indicated in FIG. 6 using their reference numeral from FIG. 4 incremented by 200 (i.e. first region 236a in FIG. 4 is referred to as first region 436a in FIG. 6). In the embodiment of FIG. 6, the first, second and third regions 436a, 436b, 436c comprise convex, concave and convex curves respectively (i.e. a ‘m’ shape), fifth, sixth and seventh regions 436e, 436f, 436g comprise concave, convex and concave curves respectively (i.e. a ‘w’ shape) and ninth, tenth and eleventh regions 436i, 436j, 436k comprise convex, concave and convex curves respectively (i.e. a ‘m’ shape). No substantially flat transition regions are present in this embodiment; the central ‘w’ shape is smoothly connected to the ‘m’ shape on either side.
[0115] FIG. 7 shows an embodiment of the invention in which mass damping elements 544 are provided on the legs 536 of a spider 520 which is otherwise as shown in FIG. 2. Elements that are similar as between FIG. 2 and FIG. 7 have been indicated in FIG. 7 using their reference numeral from FIG. 2 incremented by 500 (i.e. spider 20 in FIG. 2 is referred to as spider 520 in FIG. 7). Each mass damping element 544 comprises a substantially cylindrical body located in the second region 536b of the leg, approximately equidistant between the outer ring 530 and inner ring 532. In other embodiments the shape and/or location of the mass damping element may differ. Each mass damping element 544 is integrally formed with a leg 536. In other embodiments, the mass damping element may be a separate element attached to the leg.
[0116] FIG. 8 shows a plot of acoustic power in Watts (W) vs frequency in Hertz (Hz) using a 3D finite element analysis model to estimate the total radiate acoustic power from the spider alone. Line 46 shows the response of the spider 20 of FIG. 2 (i.e. with no mass damping elements) while line 48 shows the response of the spider 520 of FIG. 7. It can be seen that the response of both spiders is similar below 1000 Hz, but the response diverges above 1000 Hz, particularly with the response of the spider 20 (i.e. line 46) becoming highly variable and the response of the spider 520 (i.e. line 48) being much smoother.
[0117] FIG. 9 shows a portion of a spider in accordance with shows a portion of a spider 620 in accordance with an embodiment of the invention. Elements that are similar as between FIG. 2 and FIG. 9 have been indicated in FIG. 9 using their reference numeral from FIG. 2 incremented by 600 (i.e. spider 20 in FIG. 2 is referred to as spider 620 in FIG. 9). In contrast to the FIG. 2 embodiment, an intermediate ring 650 is located between the inner ring 632 and outer ring 630 of the spider 620. A first set of legs 636AA extend between the outer 630 and intermediate 650 rings and a second set of legs 636BB extend between the intermediate 650 and inner ring 632. The number, location and shape of the legs may differ as between the first and second sets. Such spiders may allow for a bigger displacement of the diaphragm for a spider of a given height and/or provide additional design flexibility that assists in achieving a target stiffness/excursion curve. In some embodiments, the intermediate ring 650 may be incomplete, that is to say it may extend around the perimeter of the inner ring 632 at only discrete regions. In other embodiments the intermediate ring may be a complete annulus.
[0118] FIG. 10 shows a flow chart of an example method of manufacturing a spider in accordance with the present invention. The method comprises a set of providing 60 an original spider design for a spider having a plurality of radially extending legs. The method comprises modifying 62 the design. The step of modifying the design comprises one changing 62a the shape of one or more of the legs to modify the stiffness vs excursion response of the spider and/or adding 62b a mass element to one or more of the legs to attenuate the frequency response of the spider at and/or around one or more vibrational modes. The step of changing 62a the shape of the legs comprises one or more of changing the curvature of the leg to provide first, second and/or third curves as discussed above; changing the amplitude and/or wavelength of the first, second and/or third curves; increasing and/or decreasing the cross-sectional area of the leg in a first, second and/or third region; increasing and/or decreasing the width of the leg in a first, second and/or third region.
[0119] The method comprises making 64 to the modified design. The step of making 64 the spider comprises molding 66 a spider from plastic material, for example PEEK.
[0120] In some embodiments the spider so produced includes one or more legs of the spider to have a cross-sectional shape that includes either (i) a concave curve located between two convex curves or (ii) a convex curve located between two concave curves. In some embodiments the legs include further curves, for example fourth, fifth and sixth curves, as described above.
[0121] In some embodiments the spider so produces includes legs having a first region having a first cross-sectional area, a second region having a second cross-sectional area, and a third region having a third cross-sectional area, the second region being located between the first and third regions, the second cross-sectional area being smaller than the first and third cross-sectional areas. In some embodiments, the one or more legs have a constant thickness, and a second width being less a first and a third width, as described above.
[0122] In some embodiments the spider so produced includes a mass element mounted on at least one of said legs, the leg and the mass element together forming a mass damping element to attenuate the frequency response of the spider at and/or around one or more vibrational modes.
[0123] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein.
[0124] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.
