Patent Grant
11388523
This application is a U.S. National Stage Application of International Patent Application No. PCT/EP2019/084950 entitled “INERTIAL EXCITERS, DRIVE UNITS AND LOUDSPEAKERS” filed on 12 Dec. 2019, which claims priority from GB1820557.5 entitled “INERTIAL EXCITER” filed 17 Dec. 2018 and GB1908461.5 entitled “INERTIAL EXCITERS, DRIVE UNITS AND LOUDSPEAKERS” filed 13 Jun. 2019, the contents and elements of which are herein incorporated by reference for all purposes.
This application claims priority from GB1820557.5 filed 17 Dec. 2018 and GB1908461.5 filed 13 Jun. 2019, the contents and elements of which are herein incorporated by reference for all purposes.
The present invention relates to an inertial exciter, to a loudspeaker including an inertial exciter, to a drive unit, and also to a loudspeaker including a drive unit. Corresponding methods are also disclosed.
Traditional loudspeakers, an example of which is shown in
Inertial exciters, an example of which is shown in
Loudspeakers incorporating inertial exciters are well known, with examples being disclosed in, for example [1]-[12].
Acoustical exciters are capable of transmitting a wide bandwidth of mechanical vibration energy into acoustic radiators, typically panels or walls that are configured to sustain that vibration energy across their surface to produce acoustic output. For a loudspeaker incorporating an inertial exciter, the frequency spectrum of interest (the frequency spectrum across which the loudspeaker is able to produce sound) may be the audible range (20 Hz-20 kHz).
In order to produce sound over a wide bandwidth, inertial exciters typically need to have a coil assembly (the part of the inertial exciter that includes the voice coil) that has a low mass and is very stiff so as to maximize the efficiency across the audio bandwidth. Whereas the magnet assembly (the part of the inertial exciter that includes the magnet system) can have a much higher mass (and generally will have a higher mass in practice).
The mechanical fixation of the exciter to the acoustic panel requires special attention: when one wants to make use of moving coil (MC) excitation combined with moving magnet (MM) excitation (these types of excitation are discussed in more detail below), ideally the exciter is mounted to the acoustic radiator only via the coupler, i.e. with the magnet assembly being suspended from the acoustic radiator via the coil assembly, thereby leaving the magnet system freely suspended.
In this example, a magnet assembly 2 including a magnet unit 10 and a frame 12 is suspended from an acoustic radiator 90 via a coil assembly including a voice coil 30 and a voice coil former 32. The voice coil 30 sits in an air gap 16 of the magnet unit 10 when the exciter 1 is at rest
The voice coil will generate a force F according to:
F=BLI
where B is magnetic field, L is wire length and I is electric current (standard units).
The inertia of the magnet assembly 2 (which is typically significantly heavier than the voice coil assembly 4) allows the voice coil assembly 4 to transmit vibrational energy to the acoustic radiator 90. Excitation of the acoustic radiator 90 caused by movement of the voice coil assembly is referred to herein as “moving coil” or “MC” excitation.
Where the magnet assembly 2 is suspended from the acoustic radiator 90 via the coil assembly 4 (as in the example shown in
As shown in
The force level provided by MC excitation (labelled “MC” in
The present inventor has observed a problem with the loudspeaker illustrated in
In detail, when mounting the acoustic panel 90 (to which the wide bandwidth inertial exciter 1 is attached) vertically, e.g. in an interior door panel of a car, the gravitational force on the magnet assembly 2 tends to rotate its position relative to the voice coil 4 assembly over time. This is due to the compliance of the single suspension 60 (in this case a spider) that is configured to position the voice coil 30 in the air gap 16 (and does this job very well), but is not configured to inhibit rotation of the magnet assembly 2 relative to the voice coil assembly 4 when the acoustic radiator 90 is vertically mounted, e.g. as may be the case in a car door.
The prior art teaches some possible solutions to this problem, some of which are summarized as follows:
Solution F uses an inertial exciter as a shaker to transmit a small bandwidth of mechanical vibration energy into structures such as a seat in a car or in a cinema to augment the experience via tactile stimulus. Generally, the frequency spectrum in which this seems enjoyable is very limited, e.g. 30 Hz-80 Hz. The design of shakers is less complicated as compared to acoustic exciters because they rely solely on the inertial vibration energy of the moving magnet system (MM) since their scope is to transfer only low frequency vibration. The fixation of such shaker to the panel is also less critical and may involve heavier constructions without compromising performance. Of course a wide bandwidth inertial exciter (with a freely suspended magnet system as in solutions A, D, E) can also be used solely as a shaker.
The inventor has observed that it is difficult to make an inertial exciter that successfully inhibits rotation of the magnet assembly relative to the voice coil assembly whilst allowing MM excitation and without adding significant weight to the voice coil assembly. Thus, it is difficult to produce an inertial exciter having good sound reproduction over a wideband bandwidth, without encountering rotation issues when the acoustic radiator is mounted vertically, e.g. as might be the case in a car door.
The present invention has been devised in light of the above considerations.
A first aspect of the invention provides:
An inertial exciter for use with an acoustic radiator, the inertial exciter comprising:
The tubular member, by being positioned radially outwardly of the voice coil former (preferably also of the air gap) with respect to the movement axis, the tubular member facilitates the attachment of the at least one suspension, preferably two suspensions, to the part of the magnet assembly positioned radially outwardly of the tubular member.
The movement axis may be defined as an axis along which the voice coil assembly is configured to move relative to the magnet assembly when the inertial exciter is activated by supplying electrical current carrying an audio signal to the voice coil.
The inertial exciter may be considered to be at rest when electrical current is not supplied to the voice coil.
Note that in order for the magnet assembly to be suspended from the acoustic radiator via the coil assembly, the magnet assembly should only be attached to the acoustic radiator via the coil assembly, i.e. with no rigid attachment between the magnet assembly and the acoustic radiator.
Preferably, the inertial exciter comprises:
The use of two suspensions, separated in the direction of the movement axis, helps to significantly reduce the rotation described above with respect to
For a typical application, the distance between locations at which the two suspensions attach to the part of the magnet assembly positioned radially outwardly of the tubular member may be at least 3 mm, more preferably at least 5 mm, more preferably at least 6 mm as measured in a direction extending parallel to the movement axis. A skilled person would appreciate that actual distances will vary in practice depending on various factors including weight of the magnet assembly (larger weight requires larger distance) and design limitations (e.g. space in aperture in which loudspeaker is to be installed).
The magnet assembly may include a frame to which the magnet unit is attached, wherein the part of the magnet assembly positioned radially outwardly of the tubular member (to which the at least one suspension is attached) is a part of the frame.
The part of the magnet assembly positioned radially outwardly of the tubular member (to which the at least one suspension is attached) could, for example, be a rim of the frame.
The part of the magnet assembly positioned radially outwardly of the tubular member (to which the at least one suspension is attached) may include a respective ledge for the/each suspension attached to the part of the magnet assembly positioned radially outwardly of the tubular member, thereby facilitating attachment of the suspension element(s) to the part of the magnet assembly positioned radially outwardly of the tubular member.
The frame (included in the magnet assembly) may include apertures configured to allow a jig to be inserted to centre the tubular member during assembly.
Some optional features of the inertial exciter described herein are described with reference to:
Features described with reference to the first and second planes are preferably described with respect to the inertial exciter when the inertial exciter is at rest. As noted above, the inertial exciter may be considered to be at rest when electrical current is not supplied to the voice coil.
The part of the magnet assembly positioned radially outwardly of the tubular member (to which the at least one suspension is attached) may include:
The magnet assembly may include a part of the magnet assembly positioned radially inwardly of the voice coil former, wherein the part of the magnet assembly position radially inwardly of the voice coil former includes:
The part of the magnet assembly positioned radially inwardly of the voice coil former may include part of the magnet unit. The proximal portion of the part of the magnet assembly positioned radially inwardly of the voice coil former may for example include part of the magnet unit, e.g. an extra magnet 114a as shown in
The tubular member may include:
The voice coil former may include:
Note that if the tubular member has the distal portion (as described above), this allows the tubular member to reach past the air gap on the outside of the magnet unit, and allows the first and second suspensions to be separated by a larger distance, compared with an arrangement in which the two suspensions are attached to the voice coil former.
Preferably, the first suspension is attached to the distal portion of the tubular member and the distal portion of the part of the magnet assembly positioned radially outwardly of the tubular member.
Preferably, the second suspension is attached to the proximal portion of the tubular member and the proximal portion of the part of the magnet assembly positioned radially outwardly of the tubular member.
However, the second suspension could potentially instead attach to the proximal portion of the voice coil former and the proximal portion of the part of the magnet assembly positioned radially inwardly of the voice coil former, whilst still allowing a wide separation between the first and second suspensions, thereby still helping to reduce the rotation discussed above with reference to
Preferably, the inertial exciter comprises both:
This arrangement allows the first and second suspensions to have a particularly large space between them, which helps to reduce the rotation discussed above with reference to
In this arrangement, the inertial exciter may optionally include a third suspension that is attached to the proximal portion of the voice coil former and the proximal portion of the part of the magnet assembly positioned radially inwardly of the voice coil former (e.g. as shown in
The tubular member preferably extends around the magnet unit.
The tubular member preferably overlaps the magnet unit along at least a portion of the movement axis.
The tubular member may be shaped to include the attachment portion, e.g. so as to facilitate direct gluing (or some other attachment) of the tubular member to the acoustic radiator.
The tubular member may be shaped to include the attachment portion and the voice coil former.
The tubular member may include or be attached to a surface extending outwardly in a radial direction (with respect to the movement axis) from the distal portion of the tubular member to provide a surface for attaching the tubular member to the first suspension. The surface may be flat. The surface may be provided by a ring, e.g. made of plastic/cardboard.
The tubular member may include or be attached to a surface extending outwardly in a radial direction (with respect to the movement axis) from the proximal portion of the tubular member to provide a surface for attaching the tubular member to the second suspension. The surface may be flat. The surface may be provided by a ring, e.g. made of plastic/cardboard.
The wall of the tubular member could form an angle with respect to the movement axis, e.g. so that the distal portion of the tubular member is further from the movement axis than the proximal portion of the tubular member, thereby forming a frusto-conical tubular member. In this case, the angle is preferably no more than 15°.
The tubular member could have one or more extensions in radially outward 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.
The width of the inertial exciter in the radial direction (perpendicular to the movement axis) will generally depend on design requirements.
The inertial exciter may include 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.
The electrical path provided by the one or more wires may extend from a connector formed on the magnet assembly (e.g. on a frame of the magnet assembly) to the voice coil.
The one or more wires may include wire from the voice coil winding and/or a lead wire which connects to the voice coil winding.
The one or more wires may include a wire that passes through or around the tubular member. A coupling element (if present—see below) may be configured to guide said wire through or around the tubular member.
The one or more wires may include a wire that passes through or around (preferably through) a frame included in the magnet assembly.
The one or more wires may include two wires that meet at an electrical junction formed on an outwardly facing surface of the tubular member, e.g. at a solderpad or glue dot on the outwardly facing surface of the tubular member.
The magnet unit is preferably configured to provide a magnetic field in an air gap. The voice coil former and/or the tubular member may be cylindrical. But other shapes of air gap, voice coil former and tubular member are possible, e.g. oval, square.
Preferably the voice coil former is arranged around the movement axis.
The voice coil former preferably extends from the attachment portion in a direction which extends along the movement axis into the air gap.
The tubular member and voice coil former are each preferably made from lightweight materials such as paper, cardboard, Kapton, aluminium, kevlar, PE, ABS etc.
The tubular member and voice coil former are preferably made of the same material as each other, but could be made of different materials.
The tubular member and voice coil former may be formed integrally with each other (preferably also the attachment portion).
Preferably the attachment portion is arranged around the movement axis.
The attachment portion may be configured to provide an attachment between the coil assembly and the acoustic radiator by including a gluing surface configured to be glued to the acoustic radiator.
The attachment portion may be configured to provide an attachment between the coil assembly and the acoustic radiator by including bayonet features (e.g. projections) configured to engage with corresponding bayonet features (e.g. slots) on the acoustic radiator to provide a bayonet attachment between the attachment portion and the acoustic radiator.
The attachment portion may be a coupling element which is separately attached to the voice coil former and/or tubular member, e.g. by glue.
The coupling element could be a ring-shaped element, e.g. a cardboard or plastic ring.
The coupling element is not an essential element of the invention, since the attachment portion could be formed integrally with the voice coil former and/or the tubular member. Or the voice coil and tubular member could be configured to attach independently (e.g. by glue) to the acoustic radiator, in which case the attachment portion could include the glue and part of the acoustic radiator.
The/each suspension could take various forms.
Preferably, the/each suspension includes one or more corrugations. A suspension including one corrugation is preferred in some examples.
The at least one suspension may include a spider. The/each suspension may be a spider.
The at least one suspension may include a roll suspension. The/each suspension may be a roll suspension.
The at least one suspension may include a piece of sheet material having a geometry configured to allow deflection in a direction parallel to the movement axis, whilst inhibiting movement in a direction perpendicular to the movement axis. The/each suspension may be a piece of sheet material having a geometry configured to allow deflection in a direction parallel to the movement axis, whilst inhibiting movement in a direction perpendicular to the movement axis.
A potential advantage of a sheet material suspension could be a reduced height (in the movement axis direction) compared with classic suspensions which typically require a corrugation to facilitate deflection in the movement axis direction.
If there are two suspensions, each suspension including one or more corrugations, then the one or more corrugations in one suspension may mirror the one or more corrugations in the other spider, e.g. with respect to a plane perpendicular to the movement axis, e.g. to help cancel asymmetries in stiffness.
The magnet unit may include a central main magnet and a U-yoke.
In use, electrical current carrying an audio signal is supplied to the voice coil which energises the voice coil and causes a magnetic field to be produced by the current in the voice coil, which interacts with the magnetic field produced in the air gap by the magnet unit, and causes the voice coil assembly to move relative to the magnet assembly. This relative movement is accommodated by the at least one suspension.
We note for completeness that [13] teaches a loudspeaker that incorporates a tubular member similar to that shown in the loudspeaker according to the first aspect of the invention, but crucially in [13] the magnet assembly is attached to the frame (and is not suspended from the panel via the coil assembly), and therefore does not incorporate an inertial exciter. There is only one suspension connected between the tubular member and the frame in [13].
A second aspect of the invention provides:
An inertial exciter for use with an acoustic radiator, the inertial exciter comprising:
The inertial exciter provided by the second aspect of the invention is similar to that provided by the first aspect of the invention, and provides essentially the same benefits as the inertial exciter provided by the first aspect of the invention, but with the components arranged in a different order in the radial direction with respect to the movement axis.
The inertial exciter provided by the second aspect of the invention permits use of a ring-shaped magnet, allow more magnet material to be used compared with the inner magnet type examples, and therefore enable more powerful inertial exciters, as may be desirable in some cases.
An inertial exciter according to the second aspect of the invention may thus incorporate any one or more features described in connection with an inertial exciter according to the first aspect of the invention, but with the ordering and direction of certain elements being altered in the radial direction (with respect to the movement axis) in order to provide equivalent benefits. Similarly, definitions described above with respect to the first aspect of the invention may be used in connection with the first aspect of the invention.
Some example features of an inertial exciter according to the second aspect of the invention will now be described.
The movement axis may be defined as an axis along which the voice coil assembly is configured to move relative to the magnet assembly when the inertial exciter is activated by supplying electrical current carrying an audio signal to the voice coil.
The inertial exciter may be considered to be at rest when electrical current is not supplied to the voice coil.
Note that in order for the magnet assembly to be suspended from the acoustic radiator via the coil assembly, the magnet assembly should only be attached to the acoustic radiator via the coil assembly, i.e. with no rigid attachment between the magnet assembly and the acoustic radiator.
Preferably, the inertial exciter comprises:
For a typical application, the distance between locations at which the two suspensions attach to the part of the magnet assembly positioned radially inwardly of the tubular member may be at least 3 mm, more preferably at least 5 mm, more preferably at least 6 mm as measured in a direction extending parallel to the movement axis. A skilled person would appreciate that actual distances will vary in practice depending on various factors including weight of the magnet assembly (larger weight requires larger distance) and design limitations (e.g. space in aperture in which loudspeaker is to be installed).
The magnet assembly may include a frame to which the magnet unit is attached, wherein the part of the magnet assembly positioned radially inwardly of the tubular member (to which the at least one suspension is attached) is a part of the frame.
The part of the magnet assembly positioned radially inwardly of the tubular member (to which the at least one suspension is attached) could, for example, be a hub of the frame.
The part of the magnet assembly positioned radially inwardly of the tubular member (to which the at least one suspension is attached) may include a respective ledge for the/each suspension attached to the part of the magnet assembly positioned radially inwardly of the tubular member, thereby facilitating attachment of the suspension element(s) to the part of the magnet assembly positioned radially inwardly of the tubular member.
The frame (included in the magnet assembly) may include apertures configured to allow a jig to be inserted to centre the tubular member during assembly.
Some optional features of the inertial exciter described herein are described with reference to:
Features described with reference to the first and second planes are preferably described with respect to the inertial exciter when the inertial exciter is at rest. As noted above, the inertial exciter may be considered to be at rest when electrical current is not supplied to the voice coil.
The part of the magnet assembly positioned radially inwardly of the tubular member (to which the at least one suspension is attached) may include:
The magnet assembly may include a part of the magnet assembly positioned radially outwardly of the voice coil former, wherein the part of the magnet assembly position radially outwardly of the voice coil former includes:
The part of the magnet assembly positioned radially outwardly of the voice coil former may include part of the magnet unit. The proximal portion of the part of the magnet assembly positioned radially outwardly of the voice coil former may for example include part of the magnet unit, e.g. a washer 213a as shown in
The tubular member may include:
The voice coil former may include:
Note that if the tubular member has the distal portion (as described above), this allows the tubular member to reach past the air gap on the inside of the magnet unit, and allows the first and second suspensions to be separated by a larger distance, compared with an arrangement in which the two suspensions are attached to the voice coil former.
Preferably, the first suspension is attached to the distal portion of the tubular member and the distal portion of the part of the magnet assembly positioned radially inwardly of the tubular member.
Preferably, the second suspension is attached to the proximal portion of the tubular member and the proximal portion of the part of the magnet assembly positioned radially inwardly of the tubular member.
However, the second suspension could potentially instead attach to the proximal portion of the voice coil former and the proximal portion of the part of the magnet assembly positioned radially outwardly of the voice coil former (e.g. as shown in
Preferably, the inertial exciter comprises both:
This arrangement allows the first and second suspensions to have a particularly large space between them, which helps to reduce the rotation discussed above with reference to
In this arrangement, the inertial exciter may optionally include a third suspension that is attached to the proximal portion of the voice coil former and the proximal portion of the part of the magnet assembly positioned radially outwardly of the voice coil former (e.g. as shown in
The magnet unit preferably extends around the tubular member.
The tubular member preferably overlaps the magnet unit along at least a portion of the movement axis.
The tubular member may be shaped to include the attachment portion, e.g. so as to facilitate direct gluing (or some other attachment) of the tubular member to the acoustic radiator.
The tubular member may be shaped to include the attachment portion and the voice coil former.
The tubular member may include or be attached to a surface extending inwardly in a radial direction (with respect to the movement axis) from the distal portion of the tubular member to provide a surface for attaching the tubular member to the first suspension. The surface may be flat. The surface may be provided by a ring, e.g. made of plastic/cardboard.
The tubular member may include or be attached to a surface extending inwardly in a radial direction (with respect to the movement axis) from the proximal portion of the tubular member to provide a surface for attaching the tubular member to the second suspension. The surface may be flat. The surface may be provided by a ring, e.g. made of plastic/cardboard.
The wall of the tubular member could form an angle with respect to the movement axis, e.g. so that the distal portion of the tubular member is closer to the movement axis that the proximal portion of the tubular member, thereby forming a frusto-conical tubular member. In this case, the angle is preferably no more than 15°.
The tubular member could have one or more extensions in radially inward 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.
The width of the inertial exciter in the radial direction (perpendicular to the movement axis) will generally depend on design requirements.
The inertial exciter may include 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.
The electrical path provided by the one or more wires may extend from a connector formed on the magnet assembly (e.g. on a frame of the magnet assembly) to the voice coil.
The one or more wires may include wire from the voice coil winding and/or a lead wire which connects to the voice coil winding.
The one or more wires may include a wire that passes through or around the tubular member. A coupling element (if present—see below) may be configured to guide said wire through or around the tubular member.
The one or more wires may include a wire that passes through or around (preferably through) a frame included in the magnet assembly.
The one or more wires may include two wires that meet at an electrical junction formed on an inwardly facing surface of the tubular member, e.g. at a solderpad or glue dot on the inwardly facing surface of the tubular member.
The magnet unit is preferably configured to provide a magnetic field in an air gap. The voice coil former and/or the tubular member may be cylindrical. But other shapes of air gap, voice coil former and tubular member are possible, e.g. oval, square.
Preferably the voice coil former is arranged around the movement axis.
The voice coil former preferably extends from the attachment portion in a direction which extends along the movement axis into the air gap.
The tubular member and voice coil former are each preferably made from lightweight materials such as paper, cardboard, Kapton, aluminium, kevlar, PE, ABS etc.
The tubular member and voice coil former are preferably made of the same material as each other, but could be made of different materials.
The tubular member and voice coil former may be formed integrally with each other (preferably also the attachment portion).
Preferably the attachment portion is arranged around the movement axis.
The attachment portion may be configured to provide an attachment between the coil assembly and the acoustic radiator by including a gluing surface configured to be glued to the acoustic radiator.
The attachment portion may be 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.
The attachment portion may be a coupling element which is separately attached to the voice coil former and/or tubular member, e.g. by glue.
The coupling element could be a ring-shaped element, e.g. a cardboard or plastic ring.
The coupling element is not an essential element of the invention, since the attachment portion could be formed integrally with the voice coil former and/or the tubular member. Or the voice coil and tubular member could be configured to attach independently (e.g. by glue) to the acoustic radiator, in which case the attachment portion could include the glue and part of the acoustic radiator.
The/each suspension could take various forms.
Preferably, the/each suspension includes one or more corrugations. A suspension including one corrugation, e.g. a roll suspension, is preferred in some examples.
The at least one suspension may include a spider. The/each suspension may be a spider.
The at least one suspension may include a roll suspension. The/each suspension may be a roll suspension.
The at least one suspension may include a piece of sheet material having a geometry configured to allow deflection in a direction parallel to the movement axis, whilst inhibiting movement in a direction perpendicular to the movement axis. The/each suspension may be a piece of sheet material having a geometry configured to allow deflection in a direction parallel to the movement axis, whilst inhibiting movement in a direction perpendicular to the movement axis.
A potential advantage of a sheet material suspension could be a reduced height (in the movement axis direction) compared with classic suspensions which typically require a corrugation to facilitate deflection in the movement axis direction.
If there are two suspensions, each suspension including one or more corrugations, then the one or more corrugations in one suspension may mirror the one or more corrugations in the other spider, e.g. with respect to a plane perpendicular to the movement axis, e.g. to help cancel asymmetries in stiffness.
The magnet unit may include a ring-shaped main magnet and a T-yoke.
In use, electrical current carrying an audio signal is supplied to the voice coil which energises the voice coil and causes a magnetic field to be produced by the current in the voice coil, which interacts with the magnetic field produced in the air gap by the magnet unit, and causes the voice coil assembly to move relative to the magnet assembly. This relative movement is accommodated by the at least one suspension.
A third aspect of the invention provides:
The acoustic radiator could have various shapes (e.g. flat, curved, small, large, geometric, free-form).
The acoustic radiator may be suspended from a frame.
The loudspeaker is preferably a dipole loudspeaker, wherein the acoustic radiator is suspended from a frame (of the dipole loudspeaker) via one or more suspension elements, wherein the frame is configured to allow sound produced by a first radiating surface of the acoustic radiator to propagate out from a first side of the dipole loudspeaker and to allow sound produced by a second radiating surface of the acoustic radiator to propagate out from a second side of the dipole loudspeaker.
Here, the first radiating surface and the second radiating surface should be located on opposite faces of the acoustic radiator.
The coil assembly of the inertial exciter may be attached to the second radiating surface of the acoustic radiator (via the attachment portion).
An inertial exciter according to the first or second aspect of the invention is particularly well suited for use in a dipole loudspeaker because its construction is such that it can obstruct a smaller area of the radiating surface of the acoustic radiator to which it is attached compared with some of the prior art examples discussed above (see e.g. [13], which requires a frame).
A fourth aspect of the invention provides:
The method may include pre-assembling the coil assembly, before suspending the magnet assembly from the coil assembly by the at least one suspension.
A fifth aspect of the invention provides:
The drive unit according to the fifth aspect of the invention therefore has essentially the same construction as the inertial exciter according to the first aspect of the invention, except that in the drive unit according to the fifth aspect of the invention, the acoustic radiator is suspended from the magnet assembly, rather than magnet assembly being suspended from the acoustic radiator.
This is advantageous because it helps to provide stable pistonic movement of the acoustic radiator and reduces rocking of the acoustic radiator when the magnet assembly is rigidly attached to an external body (e.g. frame), i.e. when the drive assembly is “grounded”.
Preferably, the magnet assembly is rigidly attached to a frame, which may be rigidly attached to an external body.
Preferably, the magnet assembly is rigidly attached to a frame from which the acoustic radiator is suspended.
Any feature described in connection with the inertial exciter according to the first aspect of the invention may be incorporated in the drive unit according to the fifth aspect of the invention, except where such a combination is clearly impermissible or expressly avoided.
A sixth aspect of the invention provides:
The drive unit according to the sixth aspect of the invention therefore has essentially the same construction as the inertial exciter according to the second aspect of the invention, except that in the drive unit according to the sixth aspect of the invention, the acoustic radiator is suspended from the magnet assembly, rather than magnet assembly being suspended from the acoustic radiator.
This is advantageous because it helps to provide stable pistonic movement of the acoustic radiator and reduces rocking of the acoustic radiator when the magnet assembly is rigidly attached to an external body (e.g. frame), i.e. when the drive assembly is “grounded”.
Preferably, the magnet assembly is rigidly attached to a frame, which may be rigidly attached to an external body.
Preferably, the magnet assembly is rigidly attached to a frame from which the acoustic radiator is suspended.
Any feature described in connection with the inertial exciter according to the first aspect of the invention may be incorporated in the drive unit according to the fifth aspect of the invention, except where such a combination is clearly impermissible or expressly avoided.
A seventh aspect of the invention provides:
The acoustic radiator could have various shapes (e.g. flat, curved, small, large, geometric, free-form).
The acoustic radiator may be suspended from a frame.
The loudspeaker is preferably a dipole loudspeaker, wherein the acoustic radiator is suspended from a frame (of the dipole loudspeaker) via one or more suspension elements, wherein the frame is configured to allow sound produced by a first radiating surface of the acoustic radiator to propagate out from a first side of the dipole loudspeaker and to allow sound produced by a second radiating surface of the acoustic radiator to propagate out from a second side of the dipole loudspeaker.
Here, the first radiating surface and the second radiating surface should be located on opposite faces of the acoustic radiator.
The coil assembly of the inertial exciter may be attached to the second radiating surface of the acoustic radiator (via the attachment portion).
Preferably, the magnet assembly is rigidly attached to the frame from which the acoustic radiator is suspended.
A drive unit according to the fifth or sixth aspect of the invention is particularly well suited for use in a dipole loudspeaker because its construction is such that it can obstruct a smaller area of the radiating surface of the acoustic radiator to which it is attached compared with some of the prior art examples discussed above (see e.g. [13], which requires a frame).
An eighth aspect of the invention provides:
The method may include pre-assembling the coil assembly, before suspending the magnet assembly from the coil assembly by the at least one suspension.
The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.
Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:
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.
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
A first inertial exciter 101a that exemplifies an inertial exciter of the inner magnet type is shown in
The inertial exciter 101a of
The magnet assembly 102a includes a magnet unit 110a and a frame 120a to which the magnet unit 110a is attached.
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.
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.
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.
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.
In this example, the washer 114a and U-yoke 116a may be made of steel, though other materials are possible.
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.
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.
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.
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).
In this example, the voice coil former 132a and tubular member 140a are cylindrical, though other shapes are possible.
Two planes are depicted in
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.
A second plane 109a is perpendicular to the movement axis 106a and extends through the air gap 116a.
The rim 124a of the frame 120a includes:
The tubular member 140a similarly includes:
The inertial exciter 101a includes:
Each suspension 160a, 165a in this example is a spider including multiple corrugations. Such suspensions are well known in the art.
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.
As can be seen from
In this example, the first and second suspensions 160a, 165a are each shown as a respective spider having multiple corrugations.
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.
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.
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.
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.
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.
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
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.
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
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
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.
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.
A second inertial exciter 101b that exemplifies an inertial exciter of the inner magnet type is shown in
The coupling element 150b of the inertial exciter 101b is shown in
The above-described bayonet feature could facilitate assembly and replacement of the inertial exciter 101b to the acoustic radiator 190b.
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.
A third inertial exciter 101c that exemplifies an inertial exciter of the inner magnet type is shown in
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.
A fourth inertial exciter 101d that exemplifies an inertial exciter of the inner magnet type is shown in
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.
A fifth inertial exciter 101e that exemplifies an inertial exciter of the inner magnet type is shown in
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).
The tubular member 140e could be made of paper, cardboard, Kapton, aluminium, kevlar, PE, ABS etc.
A sixth inertial exciter 101f that exemplifies an inertial exciter of the inner magnet type is shown in
The inertial exciter 101f is the same as the fifth inertial exciter 101e shown in
A seventh inertial exciter 101g that exemplifies an inertial exciter of the inner magnet type is shown in
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.
An eighth inertial exciter 101h that exemplifies an inertial exciter of the inner magnet type is shown in
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°.
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.
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.
A ninth inertial exciter 101i that exemplifies an inertial exciter of the inner magnet type is shown in
This example is essentially the same as the first inertial exciter 101a shown in
Example dimensions are drawn on
A tenth inertial exciter 101j that exemplifies an inertial exciter of the inner magnet type is shown in
The inertial exciter 101j shown in
The alternative form of suspension used for the first and second suspensions 160j, 165j is shown in more detail in
As can be seen most clearly from
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.
An eleventh inertial exciter 101k that exemplifies an inertial exciter of the inner magnet type is shown in
The inertial exciter 101k shown in
Note, that in this case the inertial exciter 101k has:
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.
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.
In this example, the first suspension 165k is a roll suspension including only one corrugation.
A twelfth inertial exciter 101l that exemplifies an inertial exciter of the inner magnet type is shown in
The inertial exciter 101l shown in
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.
A first inertial exciter 201a that exemplifies an inertial exciter of the outer magnet type is shown in
The inertial exciter 201a shown in
The magnet assembly 202a includes a magnet unit 210a and a frame 220a to which the magnet unit 210a is attached.
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.
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.
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).
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.
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.
The inertial exciter 201a includes:
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.
As can be seen from
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.
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.
In this example, the lead wire 234a extends through the frame 220a.
In this example, the coupling element 250a is similar to that shown in
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.
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.
A second inertial exciter 201b that exemplifies an inertial exciter of the outer magnet type is shown in
This example is that same as that shown in
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.
A third inertial exciter 201c that exemplifies an inertial exciter of the outer magnet type is shown in
This example is that same as that shown in
Note, that in this case the inertial exciter 201c has:
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.
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.
A fourth inertial exciter 201d that exemplifies an inertial exciter of the outer magnet type is shown in
This example is that same as that shown in
A drive unit 301a that exemplifies a drive unit of the inner magnet type is shown in
The construction of the drive unit 301a is essentially the same as the inertial exciter 101a of the inner magnet type shown in
A key difference from the inertial exciter 101a shown in
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.
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.
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.
A drive unit 401a that exemplifies a drive unit of the outer magnet type is shown in
The construction of the drive unit 401a is essentially the same as the inertial exciter 201a of the outer magnet type shown in
A key difference from the inertial exciter 201 shown in
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.
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.
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.
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 inventor does 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%.
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.
The entirety of each of these references is incorporated herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1820557 | Dec 2018 | GB | national |
| 1908461 | Jun 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/084950 | 12/12/2019 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/126847 | 6/25/2020 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4354067 | Yamada et al. | Oct 1982 | A |
| 4506117 | Fresard | Mar 1985 | A |
| 4550428 | Yanagishima et al. | Oct 1985 | A |
| 4675907 | Itagaki et al. | Jun 1987 | A |
| 4750208 | Yamada et al. | Jun 1988 | A |
| 5734132 | Proni | Mar 1998 | A |
| 6088466 | Proni | Jul 2000 | A |
| 6095280 | Proni | Aug 2000 | A |
| 6618487 | Azima et al. | Sep 2003 | B1 |
| 6965679 | Lopez Bosio et al. | Nov 2005 | B1 |
| 7372968 | Buos et al. | May 2008 | B2 |
| 8247930 | Yamagishi | Aug 2012 | B2 |
| 9621994 | Bongiovi et al. | Apr 2017 | B1 |
| 20040197007 | Onuma | Oct 2004 | A1 |
| 20050111690 | Onuma et al. | May 2005 | A1 |
| 20050180587 | Lopez Bosio et al. | Aug 2005 | A1 |
| 20050271241 | Watanabe | Dec 2005 | A1 |
| 20060280330 | Watanabe | Dec 2006 | A1 |
| 20170280216 | Lee | Sep 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 102004009902 | Feb 2005 | DE |
| 0912072 | Apr 1999 | EP |
| Entry |
|---|
| ISA/EP, International Search Report and Written Opinion for corresponding PCT Patent Application No. PCT/EP2019/084950, dated Jan. 31, 2020, 9 pages. |
| IPO; Examination Report for UK Patent Application No. GB1908461.5, dated Apr. 22, 2022, 5 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220038824 A1 | Feb 2022 | US |
