INERTIAL EXCITERS, DRIVE UNITS AND LOUDSPEAKERS

Abstract

An inertial exciter for use with an acoustic radiator, the inertial exciter comprising: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the inertial exciter; a coil assembly including: an attachment portion configured to provide an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap.

Claims

1-23. (canceled)

24. An inertial exciter for use with an acoustic radiator, the inertial exciter comprising: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the inertial exciter; a coil assembly including: an attachment portion configured to provide an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap, wherein the voice coil is mounted to the voice coil former so that the voice coil sits in the air gap when the inertial exciter is at rest; a tubular member, which is positioned radially outwardly of the voice coil former with respect to the movement axis, and which overlaps the voice coil former along at least a portion of the movement axis; at least one suspension attached to the tubular member and a part of the magnet assembly positioned radially outwardly of the tubular member so that, when the coil assembly is attached to the acoustic radiator via the attachment portion, the magnet assembly is suspended from the acoustic radiator via the coil assembly by the at least one suspension.

25. An inertial exciter according to claim 24, wherein the inertial exciter comprises: a first suspension attached to the tubular member and the part of the magnet assembly positioned radially outwardly of the tubular member; and a second suspension, separated from the first suspension in a direction extending parallel to the movement axis, wherein the second suspension is either: attached to the tubular member and the part of the magnet assembly positioned radially outwardly of the tubular member or is attached to the voice coil former and a part of the magnet assembly positioned radially inwardly of the voice coil former.

26. An inertial exciter according to claim 25, wherein: the first suspension is attached to a distal portion of the tubular member and a distal portion of the part of the magnet assembly positioned radially outwardly of the tubular member.

27. An inertial exciter according to claim 26, wherein: the second suspension is attached to a proximal portion of the tubular member and a proximal portion of the part of the magnet assembly positioned radially outwardly of the tubular member.

28. An inertial exciter according to claim 27, wherein: a third suspension is attached to a proximal portion of the voice coil former and a proximal portion of a part of the magnet assembly positioned radially inwardly of the voice coil former.

29. An inertial exciter according to claim 26, wherein: the second suspension is attached to a proximal portion of the voice coil former and a proximal portion of a part of the magnet assembly positioned radially inwardly of the voice coil former.

30. An inertial exciter according to claim 24, wherein the magnet assembly includes a frame to which the magnet unit is attached, wherein the part of the magnet assembly positioned radially outwardly of the tubular member is a part of the frame.

31. An inertial exciter for use with an acoustic radiator, the inertial exciter comprising: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the exciter; a coil assembly including: an attachment portion configured to provide an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap, wherein the voice coil is mounted to the voice coil former so that the voice coil sits in the air gap when the inertial exciter is at rest; a tubular member, which is positioned radially inwardly of the voice coil former with respect to the movement axis, and which overlaps the voice coil former along at least a portion of the movement axis; at least one suspension attached to the tubular member and a part of the magnet assembly positioned radially inwardly of the tubular member so that, when the coil assembly is attached to the acoustic radiator via the attachment portion, the magnet assembly is suspended from the acoustic radiator via the coil assembly by the at least one suspension.

32. An inertial exciter according to claim 31, wherein the inertial exciter comprises: a first suspension attached to the tubular member and the part of the magnet assembly positioned radially inwardly of the tubular member; and a second suspension, separated from the first suspension in a direction extending parallel to the movement axis, wherein the second suspension is either: attached to the tubular member and the part of the magnet assembly positioned radially inwardly of the tubular member or is attached to the voice coil former and a part of the magnet assembly positioned radially outwardly of the voice coil former.

33. An inertial exciter according to claim 32, wherein: the first suspension is attached to a distal portion of the tubular member and a distal portion of the part of the magnet assembly positioned radially inwardly of the tubular member.

34. An inertial exciter according to claim 33, wherein: the second suspension is attached to a proximal portion of the tubular member and a proximal portion of the part of the magnet assembly positioned radially inwardly of the tubular member.

35. An inertial exciter according to claim 34, wherein: a third suspension is attached to a proximal portion of the voice coil former and a proximal portion of a part of the magnet assembly positioned radially outwardly of the voice coil former.

36. An inertial exciter according to claim 33, wherein: the second suspension is attached to a proximal portion of the voice coil former and a proximal portion of a part of the magnet assembly positioned radially outwardly of the voice coil former.

37. An inertial exciter according to claim 31, wherein the magnet assembly includes a frame to which the magnet unit is attached, wherein the part of the magnet assembly positioned radially inwardly of the tubular member is a part of the frame.

38. An inertial exciter according to claim 24, wherein the tubular member is shaped to include the attachment portion, and optionally the voice coil former.

39. An inertial exciter according to claim 24, wherein the tubular member has one or more extensions in a radial direction with respect to the movement axis to provide a respective attachment surface for the/each suspension attached to the tubular member, thereby facilitating attachment of the/each suspension to the tubular member.

40. An inertial exciter according to claim 24, wherein the attachment portion is a coupling element which is separately attached to the voice coil former and/or tubular member.

41. An inertial exciter according to claim 24, wherein the attachment portion is configured to provide an attachment between the coil assembly and the acoustic radiator by including bayonet features configured to engage with corresponding bayonet features on the acoustic radiator to provide a bayonet attachment between the attachment portion and the acoustic radiator.

42. An inertial exciter according to claim 24, wherein the inertial exciter includes one or more wires configured to provide an electrical path for supplying an electrical current carrying an audio signal (representative of sound) to the voice coil, wherein: the electrical path provided by the one or more wires extends from a connector formed on the magnet assembly to the voice coil; and/or the one or more wires include a wire that passes through or around the tubular member, wherein optionally a coupling element is configured to guide said wire through or around the tubular member; and/or the one or more wires may include a wire that passes through a frame included in the magnet assembly.

43. An inertial exciter according to claim 24, wherein the inertial exciter is part of a loudspeaker including an acoustic radiator, wherein the coil assembly of the inertial exciter is attached to the acoustic radiator via the attachment portion so that the magnet assembly is suspended from the acoustic radiator via the coil assembly via the at least one suspension.

44. An inertial exciter according to claim 31, wherein the tubular member is shaped to include the attachment portion, and optionally the voice coil former.

45. An inertial exciter according to claim 31, wherein the tubular member has one or more extensions in a radial direction with respect to the movement axis to provide a respective attachment surface for the/each suspension attached to the tubular member, thereby facilitating attachment of the/each suspension to the tubular member.

46. An inertial exciter according to claim 31, wherein the attachment portion is a coupling element which is separately attached to the voice coil former and/or tubular member.

47. An inertial exciter according to claim 31, wherein the attachment portion is configured to provide an attachment between the coil assembly and the acoustic radiator by including bayonet features configured to engage with corresponding bayonet features on the acoustic radiator to provide a bayonet attachment between the attachment portion and the acoustic radiator.

48. An inertial exciter according to claim 31, wherein the inertial exciter includes one or more wires configured to provide an electrical path for supplying an electrical current carrying an audio signal (representative of sound) to the voice coil, wherein: the electrical path provided by the one or more wires extends from a connector formed on the magnet assembly to the voice coil; and/or the one or more wires include a wire that passes through or around the tubular member, wherein optionally a coupling element is configured to guide said wire through or around the tubular member; and/or the one or more wires may include a wire that passes through a frame included in the magnet assembly.

49. An inertial exciter according to claim 31, wherein the inertial exciter is part of a loudspeaker including an acoustic radiator, wherein the coil assembly of the inertial exciter is attached to the acoustic radiator via the attachment portion so that the magnet assembly is suspended from the acoustic radiator via the coil assembly via the at least one suspension.

50. A drive unit for use with an acoustic radiator, the drive unit comprising: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the inertial exciter; a coil assembly including: an attachment portion configured to provide an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap, wherein the voice coil is mounted to the voice coil former so that the voice coil sits in the air gap when the drive unit is at rest; a tubular member, which is positioned radially outwardly of the voice coil former with respect to the movement axis, and which overlaps the voice coil former along at least a portion of the movement axis; at least one suspension attached to the tubular member and a part of the magnet assembly positioned radially outwardly of the tubular member so that, when the coil assembly is attached to the acoustic radiator via the attachment portion, the acoustic radiator is suspended from the magnet assembly via the coil assembly by the at least one suspension.

51. A drive unit for use with an acoustic radiator, the drive unit comprising: a magnet assembly including a magnet unit configured to provide a magnetic field in an air gap, wherein the air gap extends around a movement axis of the exciter; a coil assembly including: an attachment portion configured to provide an attachment between the coil assembly and the acoustic radiator; a voice coil; a voice coil former which extends from the attachment portion into the air gap, wherein the voice coil is mounted to the voice coil former so that the voice coil sits in the air gap when the drive unit is at rest; a tubular member, which is positioned radially inwardly of the voice coil former with respect to the movement axis, and which overlaps the voice coil former along at least a portion of the movement axis; at least one suspension attached to the tubular member and a part of the magnet assembly positioned radially inwardly of the tubular member so that, when the coil assembly is attached to the acoustic radiator via the attachment portion, the acoustic radiator is suspended from the magnet assembly via the coil assembly by the at least one suspension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0297] 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.

[0298] For the purpose of this description, example inertial exciters are divided into two types, referred to as “inner magnet” type according to the first aspect of the invention and “outer magnet” type according to the second aspect of the invention. Similarly, example drive units are divided into two types, referred to as “inner magnet” type according to the fifth aspect of the invention and “outer magnet” type according to the sixth aspect of the invention

Inertial Exciter—Inner Magnet Type Examples

[0299] A first inertial exciter 101a that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(a)(i).

[0300] The inertial exciter 101a of FIG. 4(a) comprises a magnet assembly 102a and a coil assembly 104a.

[0301] The magnet assembly 102a includes a magnet unit 110a and a frame 120a to which the magnet unit 110a is attached.

[0302] In this example, the magnet unit 110a includes a main magnet 112a, a washer 113a an extra magnet 114a and a U-yoke 115a. The magnet unit 110a is configured to provide a magnetic field in an air gap 116a. The air gap 116a extends around a movement axis 106a of the inertial exciter 101a.

[0303] The frame 120a includes a base portion 122a which extends radially outwardly with respect to the movement axis 106a (in this example from a base of the U-yoke 115a), and a rim 124a which extends axially with respect to the movement axis 106a, that is at least partly along the movement axis 106a. The rim 124a of the frame 120a is positioned at the periphery of the base portion 122a, and is positioned radially outwardly of the magnet unit 110a.

[0304] The rim 124a of the frame 120a is positioned radially outwardly of a tubular member 140a, and thus serves as the “part of the magnet assembly positioned radially outwardly of the tubular member” referenced in the “Summary of the invention” section of this document, above.

[0305] In this example, the main magnet 112a, washer 113a, extra magnet 114a, U-yoke 115a, and air gap 116a are circular, though other forms are possible.

[0306] In this example, the washer 114a and U-yoke 116a may be made of steel, though other materials are possible.

[0307] In this example, the coil assembly 104a includes a voice coil 130a, a voice coil former 132a, a tubular member 140a and an attachment portion 150a.

[0308] In this example, the attachment portion 150a is a coupling element which is separately attached to the voice coil former and tubular member, e.g. by glue. The coupling element 150a is configured to provide an attachment between the coil assembly 104a and an acoustic radiator (not shown) by including a gluing surface 151a configured to be glued to the acoustic radiator. The coupling element 150a could for example be a plastic or cardboard ring-shaped element.

[0309] The voice coil former 132a extends axially with respect to the movement axis 106a from the coupling element 150a into the air gap 116a. The voice coil 130a is mounted to the voice coil former 132a so that the voice coil 130a sits in the air gap 116a when the inertial exciter 101a is at rest.

[0310] The tubular member 140a is positioned radially outwardly of the voice coil former 132a with respect to the movement axis 106a. The tubular member 140a also overlaps the voice coil former 132a along a portion of the movement axis (this portion corresponding to the full length of the voice coil former 132a).

[0311] In this example, the voice coil former 132a and tubular member 140a are cylindrical, though other shapes are possible.

[0312] Two planes are depicted in FIG. 4(a)(i).

[0313] A first plane 108a is perpendicular to the movement axis 106a and extends through the attachment portion which as noted above is the coupling element 150a.

[0314] A second plane 109a is perpendicular to the movement axis 106a and extends through the air gap 116a.

[0315] The rim 124a of the frame 120a includes:

[0316] a proximal portion, wherein the proximal portion of the rim 124a is located between the first plane 108a and the second plane 109a; and a distal portion, wherein the distal portion of the rim 124a is located is on an opposite side of the second plane 109a from the proximal portion of the rim 124a.

[0317] The tubular member 140a similarly includes:

[0318] a proximal portion, wherein the proximal portion of the tubular member 140a is located between the first plane 108a and the second plane 109a; and a distal portion, wherein the distal portion of the tubular member 140a is located is on an opposite side of the second plane 109a from the proximal portion of the of the tubular member 140a.

[0319] The inertial exciter 101a includes:

[0320] a first suspension 160a that is attached to the distal portion of the tubular member 140a and the distal portion of the rim 124a; and a second suspension 165a that is attached to the proximal portion of the tubular member 140a and the proximal portion of the rim 124a.

[0321] Each suspension 160a, 165a in this example is a spider including multiple corrugations. Such suspensions are well known in the art.

[0322] Thus, when the coil assembly 104a is attached to the acoustic radiator via the attachment portion/coupling element 150a, the magnet assembly 102a is suspended from the acoustic radiator via the coil assembly 104a by the first and second suspensions 160a, 165a.

[0323] As can be seen from FIG. 4(a)(i), the rim 124a of the frame 120a includes a first ledge 125a to which the first suspension 160a is attached, and a second ledge 126a to which the second suspension 165a is attached.

[0324] In this example, the first and second suspensions 160a, 165a are each shown as a respective spider having multiple corrugations.

[0325] The inertial exciter 101a includes wires 134a, 135a configured to provide an electrical path for supplying an electrical current carrying an audio signal (representative of sound) to the voice coil 130a.

[0326] The electrical path provided by the wires 134a, 135a extend from a connector 138a formed on an outwardly facing surface of the rim 124a of the frame 120a to the voice coil 130a.

[0327] In this example, the wires include part of the voice coil winding 134a as well as a lead wire 135a. In this example, the voice coil winding 134a extends around the tubular member 140a as guided by the coupling element 150a.

[0328] The voice coil winding 134a and lead wire 135a meet at an electrical junction formed at a solderpad or glue dot 136a on an outwardly facing surface of the tubular member 140a.

[0329] FIG. 4(a)(ii) shows a loudspeaker 180a including the inertial exciter 101a of FIG. 4(a)(i) and an acoustic radiator 190a suspended from a frame 192, wherein the coil assembly 104a of the inertial exciter 101a is attached to the acoustic radiator 190a via the attachment portion/coupling element 150a so that the magnet assembly 102a is suspended from the acoustic radiator 190a via the coil assembly by the first and second suspensions 160a, 165a.

[0330] In use, electrical current carrying an audio signal is supplied to the voice coil 130a via the connector 138a and wires 134a, 135a. This energises the voice coil 130a and causes a magnetic field to be produced by the current in the voice coil 130a, which interacts with the magnetic field produced in the air gap 116a by the magnet unit 110a, and causes the voice coil assembly 104a to move relative to the magnet assembly 102a. This relative movement is accommodated by the first and second suspensions 160a, 165a.

[0331] Because the magnet assembly 102a is suspended from the acoustic radiator via the coil assembly 104a by the first and second suspensions 160a, 165a, the loudspeaker is able to be moved by MC and MM excitation, as indicated by FIG. 4(a)(iii).

[0332] Because the voice coil former 132a and tubular member 140a are tubular, they provide good stiffness even when made of a lightweight material such as paper, cardboard, Kapton, aluminium, kevlar etc. Thus, the voice coil assembly 104a can have low weight and good stiffness, as is needed for good wide bandwidth performance from MC excitation.

[0333] Moreover, because the tubular member 140a has a distal portion which overlaps the voice coil former 132a so as to extend beyond the air gap 116a, i.e. to the opposite side of the second plane 109a from the proximal portion of the tubular member 140a, it is possible to have a large distance between the first and second suspensions 160a, 165a, which helps inhibit rotation of the magnet assembly 102a relative to the voice coil assembly 104a when the acoustic radiator 190a is vertically mounted, e.g. as may be the case in a car door, as depicted in FIG. 4(a)(iii).

[0334] Note that this is achieved whilst providing one interface (the glue surface of the coupling element 150a) with the acoustic radiator 190a, and also whilst permitting MC excitation. The low mass of the voice coil assembly (see above) help to achieve acoustic sensitivity and balance in the upper frequency band, as depicted in FIG. 4(a)(iv).

[0335] FIG. 4(a)(v) shows a method step involved in assembling the inertial exciter 101a which makes use of a conventional centering jig 195a to align the voice coil former 132a in the air gap 116a before the components of the voice coil assembly 104a are glued together. The coupling element 150a may be flush with an inwardly facing surface of the voice coil former 132a to facilitate use of the centering jig 195a.

[0336] FIG. 4(a)(vi) shows an alternative or additional method step involved in assembling the inertial exciter 101a in which apertures are incorporated into the frame 120a to allow a centering jig 196a to be inserted into the apertures during assembly, e.g. to help with aligning the voice coil former 132a in the air gap 116a.

[0337] Preferably the voice coil assembly (including the coupling element 150am the voice coil 130a, voice coil former 132a and the tubular member 140a) could be pre-assembled on a separate jig (not shown) before being assembled in the magnet assembly 102a.

[0338] Various alternative inner magnet examples will now be described. Alike features have been given alike reference numerals where appropriate and are not described in further detail, except where necessary.

[0339] A second inertial exciter 101b that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(b)(i).

[0340] The coupling element 150b of the inertial exciter 101b is shown in FIG. 4(b)(ii) and includes bayonet features in the form of radial extensions 151b configured to engage with corresponding bayonet features 191b on the acoustic radiator 190b shown in FIG. 4(b)(iii) to provide a bayonet attachment between the coupling element 150b and the acoustic radiator 190b. The bayonet features 191b on the acoustic radiator preferably form slots for accommodating the radial extensions 151b. The resulting loudspeaker 180b is shown in FIG. 4(b)(iv).

[0341] The above-described bayonet feature could facilitate assembly and replacement of the inertial exciter 101b to the acoustic radiator 190b.

[0342] The above-described bayonet features could be combined with adhesives or filler (e.g. grease) to avoid rattling during operation. The adhesive or filler could have temperature dependent properties so that by applying heat the inertial exciter 101b can be replaced.

[0343] A third inertial exciter 101c that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(c).

[0344] In this example, the tubular member 140c includes a collar 141c that provides a flat face to facilitate gluing of the first suspension 160c, which in this example could be a fabric damper, a metal or plastic spiral spring, a rubber element, etc.

[0345] A fourth inertial exciter 101d that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(d).

[0346] In this example, the a ring 141d, e.g. made of cardboard or plastic, is attached to the distal portion of the tubular member 140d to provide a flat surface 141d to facilitate gluing of the first suspension 160d.

[0347] A fifth inertial exciter 101e that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(e).

[0348] In this example, the tubular member 140e is integrally formed with the attachment portion 150e by appropriately shaping the tubular member 140e to include the attachment portion 150e. This allows the tubular member 140e to be glued directly to the voice coil former 132e, and avoids the use of a coupling element as described in previous examples. In this example, the attachment portion 150e is a flat face of the tubular member 140e that is configured to be glued to the acoustic radiator (not shown).

[0349] The tubular member 140e could be made of paper, cardboard, Kapton, aluminium, kevlar, PE, ABS etc.

[0350] A sixth inertial exciter 101f that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(f).

[0351] The inertial exciter 101f is the same as the fifth inertial exciter 101e shown in FIG. 4(e), except that holes are formed in the attachment portion 150f to enhance the glue attachment to the acoustic radiator (not shown).

[0352] A seventh inertial exciter 101g that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(g).

[0353] In this example, the coupling element 150g is attached only to the voice coil former 132g, with the tubular member 140g being attached to the voice coil former 132g.

[0354] An eighth inertial exciter 101h that exemplifies an inertial exciter of the inner magnet type is shown in

[0355] FIG. 4(h).

[0356] In this example, the tubular member 140h forms an angle with respect to the movement axis, thereby forming a frusto-conical tubular member 140h. In this case, the angle is preferably no more than 15°.

[0357] A tubular member 140h shaped in this way could facilitate the making of the tubular member 140h from paper or from plastic in a deep draw process.

[0358] In this example, the tubular member 140h is again integrally formed with the attachment portion 150h by appropriately shaping the tubular member 140h to include the attachment portion 150h.

[0359] A ninth inertial exciter 101i that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(i)(i).

[0360] This example is essentially the same as the first inertial exciter 101a shown in FIG. 4(a)(i), except that in this case the first and second suspensions 160i, 165i include only a single corrugation, and the single corrugations mirror each other (in a plane 108i perpendicular to the movement axis 106i) to help cancel asymmetries in stiffness between the two suspensions 160i, 165i. The first and second suspensions 160i, 165i may in this case be roll suspensions, e.g. made of rubber, textile or foam.

[0361] FIG. 4(i)(ii) show the attachment between the frame 120i and the suspensions 160i, 165i. In this particular example, the rim of the frame 120i is provided in two parts, 124i(i) and 124i(ii).

[0362] Example dimensions are drawn on FIG. 4(i)(i) and FIG. 4(i)(ii), noting that the distance between locations at which the two suspensions 160i, 165i attach to the rim of the magnet assembly is 6.3 mm in this example, which is large given the overall size of the inertial exciter 101i.

[0363] FIGS. 4(i)(iii)-(viii) are 3D views showing the inertial exciter 101i from various angles.

[0364] A tenth inertial exciter 101j that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(j)(i).

[0365] The inertial exciter 101j shown in FIG. 4(j)(i) is the same as the inertial exciter 101a shown in FIG. 4(a)(i) except that the inertial exciter includes an alternative form of first and second suspensions 160j, 165j.

[0366] The alternative form of suspension used for the first and second suspensions 160j, 165j is shown in more detail in FIG. 4(j)(ii).

[0367] As can be seen most clearly from FIG. 4(j)(ii), the alternative form of first and second suspensions 160j, 165j is a piece of sheet material having a geometry configured to allow deflection in a direction parallel to the movement axis 106j, whilst inhibiting movement in a direction perpendicular to the movement axis 106j.

[0368] A suitable material for the alternative form of first and second suspensions 160j, 165j could be a fiber-reinforced plastic, e.g. a polymer matrix reinforced with glass fibres or carbon fibres, or a metal, e.g. steel spring material.

[0369] An eleventh inertial exciter 101k that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(k).

[0370] The inertial exciter 101k shown in FIG. 4(k) is the same as the inertial exciter 101a shown in FIG. 4(a)(i) except that in this example the second suspension 165k is attached to a proximal portion of the voice coil former 132k and a proximal portion of a part of the magnet assembly positioned radially inwardly of the voice coil former (in this case the extra magnet 114k).

[0371] Note, that in this case the inertial exciter 101k has: [0372] a first suspension 160k that is attached to a distal portion of the tubular member 140k and the distal portion of the rim 124k; and [0373] a second suspension 165k that is attached to a proximal portion of the voice coil former 132k and a proximal portion of a part of the magnet assembly positioned radially inwardly of the voice coil former 132k (in this case the extra magnet 114k).

[0374] Thus, this arrangement still allows for a wide separation between the first and second suspensions 160k, 165k, thereby helping to inhibit rotation of the magnet assembly 102k relative to the voice coil assembly 104k.

[0375] Besides providing suspension, the second suspension 165k can also serve as a dust cover to prevent dust in the airgap 116k prior to mounting the inertial exciter 101k to an acoustic radiator.

[0376] In this example, the first suspension 165k is a roll suspension including only one corrugation.

[0377] A twelfth inertial exciter 101l that exemplifies an inertial exciter of the inner magnet type is shown in FIG. 4(l).

[0378] The inertial exciter 101l shown in FIG. 4(l) is the same as the inertial exciter 101a shown in FIG. 4(a)(i) except that a third suspension 168l is attached to a proximal portion of the voice coil former 132l and a proximal portion of a part of the magnet assembly positioned radially inwardly of the voice coil former (in this case the extra magnet 114l).

[0379] Besides providing suspension, the third suspension 168l can also serve as a dust cover to prevent dust in the airgap 116l prior to mounting the inertial exciter 101l to an acoustic radiator.

Inertial Exciter—Outer Magnet Type Examples

[0380] A first inertial exciter 201a that exemplifies an inertial exciter of the outer magnet type is shown in FIG. 5(a).

[0381] The inertial exciter 201a shown in FIG. 5(a) includes many features which are common to the inertial exciter 101a shown in FIG. 4(a)(i). Alike features have been given alike reference numerals where appropriate and are not described in further detail, except where necessary.

[0382] The magnet assembly 202a includes a magnet unit 210a and a frame 220a to which the magnet unit 210a is attached.

[0383] In this example, the magnet unit 210a includes a (ring-shaped) main magnet 212a, a (ring-shaped) washer 213a and a T-yoke 215a (which looks like an upside down “T” as drawn). The magnet unit 210a is configured to provide a magnetic field in an air gap 216a. The air gap 216a extends around a movement axis 206a of the inertial exciter 201a.

[0384] The outer magnet type examples can be useful as they allow more magnet material to be used compared with the inner magnet type examples, and therefore enable more powerful exciters, as may be desirable in some cases.

[0385] In this example, the frame 220a includes a base portion 222a which extends radially inwardly with respect to the movement axis 206a (in this example from a base of the T-yoke 215a).

[0386] In this example, the frame 220a also include a hub 224a which extends axially with respect to the movement axis 206a, that is at least partly along the movement axis 206a. The hub 224a of the frame 220a is positioned at the centre of the base portion 222a, and is positioned radially inwardly of the tubular member 240a.

[0387] In this example, the tubular member 240a is positioned radially inwardly of the voice coil former 232a with respect to the movement axis 206a, and overlaps the voice coil former 232a along at least a portion of the movement axis 206a.

[0388] The inertial exciter 201a includes: [0389] a first suspension 260a that is attached to a distal portion of the tubular member 240a and the distal portion of the hub 224a; and [0390] a second suspension 265a that is attached to the proximal portion of the tubular member 240a and the proximal portion of the hub 224a.

[0391] The proximal portions of the tubular member 240a and hub 224a are located between the first plane 208a and the second plane 209a as defined above. The proximal portions of the tubular member 240a and hub 224a are located on an opposite side of the second plane 209a from the proximal portions.

[0392] As can be seen from FIG. 5(a), the hub 224a of the frame 220a includes a first ledge 225a to which the first suspension 260a is attached, and a second ledge 226a to which the second suspension 265a is attached.

[0393] In this example, the inertial exciter 201a includes a lead wire 234a configured to provide an electrical path for supplying an electrical current carrying an audio signal (representative of sound) to the voice coil 130a.

[0394] In this example, the electrical path provided by the lead wire 234a extend from a connector 238a formed on an outwardly facing surface of the base portion 222 of the frame 220a (outward in the sense of facing away from the hub 224a) to the voice coil 230a.

[0395] In this example, the lead wire 234a extends through the frame 220a.

[0396] In this example, the coupling element 250a is similar to that shown in FIG. 4(a)(i).

[0397] In use, electrical current carrying an audio signal is supplied to the voice coil 230a via the connector 238a and lead wire 234a. This energises the voice coil 230a and causes a magnetic field to be produced by the current in the voice coil 230a, which interacts with the magnetic field produced in the air gap 216a by the magnet unit 210a, and causes the voice coil assembly 204a to move relative to the magnet assembly 202a. This relative movement is accommodated by the first and second suspensions 260a, 265a.

[0398] Various alternative inner magnet examples will now be described. Alike features have been given alike reference numerals where appropriate and are not described in further detail, except where necessary.

[0399] A second inertial exciter 201b that exemplifies an inertial exciter of the outer magnet type is shown in FIG. 5(b).

[0400] This example is that same as that shown in FIG. 5(a), except that a third suspension 268b is attached to the voice coil former 232b and to a part of the magnet assembly 202b (in this case the washer 213b) positioned radially outwardly of the voice coil former 232a.

[0401] Besides providing suspension, the third suspension 268b can also serve as a dust cover to prevent dust in the airgap 216b when the inertial exciter 201b is in use.

[0402] A third inertial exciter 201c that exemplifies an inertial exciter of the outer magnet type is shown in FIG. 5(c).

[0403] This example is that same as that shown in FIG. 5(a), except that in this example the second suspension 265c is attached to the voice coil former 232b and to a part of the magnet assembly 202b (in this case the washer 213b) positioned radially outwardly of the voice coil former 232a.

[0404] Note, that in this case the inertial exciter 201c has:

[0405] a first suspension 260c that is attached to a distal portion of the tubular member 240c and the distal portion of the hub 224c; and an second suspension 265c that is attached to a proximal portion of the tubular member 240c and a proximal portion of a part of the magnet assembly positioned radially outwardly of the tubular member 240c (in this case the washer 213b).

[0406] Thus, this arrangement still allows for a wide separation between the first and second suspensions 160k, 165k, thereby helping to inhibit rotation of the magnet assembly 202c relative to the voice coil assembly 204c.

[0407] Besides providing suspension, the second suspension 265c can also serve as a dust cover to prevent dust in the airgap 216c when the inertial exciter 201b is in use.

[0408] A fourth inertial exciter 201d that exemplifies an inertial exciter of the outer magnet type is shown in FIG. 5(d).

[0409] This example is that same as that shown in FIG. 5(b), except that: [0410] the tubular member 240d is integrally formed with the attachment portion 250d by appropriately shaping the tubular member 240d to include the attachment portion 250d. [0411] holes are formed in the attachment portion 250d to enhance the glue attachment to the acoustic radiator (not shown)

Drive Unit—Inner Magnet Type Example

[0412] A drive unit 301a that exemplifies a drive unit of the inner magnet type is shown in FIG. 6(a). The construction of the drive unit 301a is essentially the same as the inertial exciter 101a of the inner magnet type shown in FIG. 4(a)(i), with alike features being given alike reference numerals that do not need to be described further here.

[0413] A key difference from the inertial exciter 101a shown in FIG. 4(a)(i) is that the magnet assembly 302a of the drive unit 301a shown here is grounded, i.e. with the magnet assembly 302a (preferably the frame 320a of the magnet assembly 302a) being rigidly attached to an external body, preferably a frame from which the acoustic radiator 390a is suspended.

[0414] Thus, the acoustic radiator 390a is suspended from the magnet assembly 302a via the coil assembly 304a by the first and second suspensions 360a, 365a, rather than magnet assembly 302a being suspended from the acoustic radiator 390a.

[0415] Of course, any of the inertial exciters of the inner magnet type as shown in any of the preceding drawings could be configured for use as a drive unit in this way.

[0416] As noted previously, this arrangement helps to provide stable pistonic movement of the acoustic radiator 390a and reduces rocking of the acoustic radiator 390a, and also takes up a small surface area on a radiating surface of the acoustic radiator 390a and thus is particularly useful in a dipole loudspeaker.

Drive Unit—Outer Magnet Type Example

[0417] A drive unit 401a that exemplifies a drive unit of the outer magnet type is shown in FIG. 6(b).

[0418] The construction of the drive unit 401a is essentially the same as the inertial exciter 201a of the outer magnet type shown in FIG. 5(a), with alike features being given alike reference numerals that do not need to be described further here.

[0419] A key difference from the inertial exciter 201 shown in FIG. 5(a) is that the magnet assembly 402a of the drive unit 401a shown here is grounded, i.e. with the magnet assembly 402a (preferably the frame 420a of the magnet assembly 402a) being rigidly attached to an external body, preferably a frame from which the acoustic radiator is suspended.

[0420] Thus, the acoustic radiator 490a is suspended from the magnet assembly 402a via the coil assembly 404a by the first and second suspensions 460a, 465a, rather than magnet assembly 402a being suspended from the acoustic radiator 490a.

[0421] Of course, any of the inertial exciters of the outer magnet type as shown in any of the preceding drawings could be configured for use as a drive unit in this way.

[0422] As noted previously, this arrangement helps to provide stable pistonic movement of the acoustic radiator 490a and reduces rocking of the acoustic radiator 490a, and also takes up a small surface area on a radiating surface of the acoustic radiator 490a and thus is particularly useful in a dipole loudspeaker.

[0423] 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.

[0424] 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.

[0425] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventor does not wish to be bound by any of these theoretical explanations.

[0426] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0427] 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.

[0428] 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%.

REFERENCES

[0429] A number of publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below.

[0430] The entirety of each of these references is incorporated herein. [0431] [1] U.S. Pat. No. 6,618,487B1 [0432] [2] U.S. Pat. No. 4,506,117A [0433] [3] U.S. Pat. No. 8,247,930B2 [0434] [4] U.S. Pat. No. 7,372,968B2 [0435] [5] U.S. Pat. No. 4,550,428A [0436] [6] U.S. Pat. No. 6,965,679B1 [0437] [7] US2005/180587A1 [0438] [8] U.S. Pat. No. 4,675,907A [0439] [9] U.S. Pat. No. 4,354,067A [0440] [10] U.S. Pat. No. 4,750,208A [0441] [11] DE102004009902A1 [0442] [12] U.S. Pat. No. 9,621,994B1 [0443] [13] U.S. Pat. No. 5,734,132