WO2021260339A1

WO2021260339A1 - Biasing magnet

Info

Publication number: WO2021260339A1
Application number: PCT/GB2021/051094
Authority: WO
Inventors: Egidijus Mikalauskas; Richard Mark Newlove
Original assignee: Amina Technologies Limited
Priority date: 2020-06-26
Filing date: 2021-05-06
Publication date: 2021-12-30
Also published as: CN115735364A; GB2585762A; GB202009771D0; GB2585762B

Abstract

There is provided a flat panel loudspeaker for mounting inside a structure, the flat panel loudspeaker comprising: a panel having a front to face outwardly when mounted inside a structure, and a rear opposite the front, the panel being a resonant planar panel; a drive unit for exciting the panel into a vibrational state, the drive unit comprising one or more magnets and a foot arranged concentrically with the one or more magnets, wherein the foot is substantially cylindrically shaped having a front coupled to the rear of the panel, and a rear opposite the front of the foot, wherein a cross-sectional area of the foot defines an inner region of the panel, and wherein, in use, the one or more magnets are configured to drive the foot to move axially relative to the one or more magnets so as to cause the panel to vibrate; a support frame having a periphery of the panel fixedly mounted thereto, such that the periphery of the panel is configured to be fixedly mounted relative to the structure, when mounted inside the structure; and a biasing magnet supported in the inner region of the panel, wherein the biasing magnet is configured to repel the one or more magnets so as to bias the panel away from the one or more magnets, or wherein the biasing magnet is configured to attract the one or more magnets so as to bias the panel toward the one or more magnets.

Description

l

Biasing Magnet

[0001] The present disclosure relates to a flat panel loudspeaker for mounting inside a structure, a kit of parts for manufacturing a flat panel loudspeaker, and a method thereof.

BACKGROUND

[0002] It is often desirable to mount devices that would otherwise be taking up space within rooms in the walls or in other structures such as ceilings in those rooms so as to be flush with, or substantially not protruding from the surfaces. Flat panel loudspeakers (sometimes referred to as distributed mode loudspeakers) are particularly suited to this application, because they can be mounted in an opening defined in a surface of a building, such as a surface of a wall, a floor, or a ceiling. Such flat panel loudspeakers include a planar panel having a front surface that is arranged to be substantially flush with, for example, the surface of the wall. One general appeal of flat panel loudspeakers installed in this way is that such flat panel loudspeakers can be made to look invisible. Once such a flat panel loudspeaker is mounted in the opening of the surface, the flat panel loudspeaker can be made “invisible” by blending the surface with a boundary of the flat panel loudspeaker insofar as it is generally not apparent that the flat panel of a loudspeaker forms part of the surface (or that the surface defines an opening therein). For example, a thin plaster coat can be applied over at least a boundary of the front surface of the flat panel loudspeaker to make it difficult, if not impossible, to visually identify the location or even presence of the flat panel loudspeaker in the wall.

[0003] Flat panel loudspeakers typically comprise a resonant panel having a front surface to face outwardly from the flat panel loudspeaker in use, and a rear surface opposite the front surface. A drive unit is generally provided mounted to the rear surface of the resonant panel to cause the resonant panel to vibrate, whereby the vibrations cause the resonant panel to generate sound. In this way, the placement of the drive unit does not interfere with the blending of the front surface of the resonant panel and the surface in which the flat panel loudspeaker is to be mounted. Generally, the drive unit is protected by being mounted within a mounting box or similar.

[0004] It is in this context that the present disclosure has been devised.

BRIEF SUMMARY OF THE DISCLOSURE

[0005] According to a first aspect of the present disclosure, there is provided a flat panel loudspeaker for mounting inside a structure. The flat panel loudspeaker comprises a panel having a front to face outwardly when mounted inside a structure, and a rear opposite the front. The panel is a resonant planar panel. The flat panel loudspeaker further comprises a drive unit for exciting the panel into a vibrational state. The drive unit comprises one or more magnets and a foot arranged concentrically with the one or more magnets. The foot is substantially cylindrically shaped having a front coupled to the rear of the panel, and a rear opposite the front of the foot. A cross-sectional area of the foot defines an inner region of the panel, and, in use, the one or more magnets are configured to drive the foot to move axially relative to the one or more magnets so as to cause the panel to vibrate. The flat panel loudspeaker further comprises a support frame having a periphery of the panel fixedly mounted thereto, such that the periphery of the panel is configured to be fixedly mounted relative to the structure, when mounted inside the structure. The flat panel loudspeaker further comprises a biasing magnet supported in the inner region of the panel, wherein the biasing magnet is configured to repel the one or more magnets so as to bias the panel away from the one or more magnets, or wherein the biasing magnet is configured to attract the one or more magnets so as to bias the panel toward the one or more magnets.

[0006] The panel is a resonant planar panel. In other words, the planar panel is configured to resonate at predetermined frequencies. This is typical in distributed mode flat panel loudspeakers, and ensures sound reproduction can be achieved by movement of an drive unit mechanically coupled to the resonant panel.

[0007] The present inventors have realised that flat panel loudspeakers of the prior art, of the type described in the background section hereinbefore, can suffer from suboptimal audio performance because at least some high frequency sounds are not accurately reproduced between the audio input received by the drive unit and the audio output generate by the planar panel. In particular, the inventors have noticed that a region of “drum skin” resonance arises from an exaggerated displacement of an inner region of the panel when it is vibrated, where the vibrations of the inner region can detrimentally interfere with those in the region surrounding the inner region, particularly impacting the amplitude of the response in the distributed mode flat panel loudspeaker for certain high frequencies. This detrimental interference can result in a frequency response of the whole distributed mode vibrating panel loudspeaker, whereby the inner region is over vibrated in comparison to the outer regions, because the energy is not uniformly distributed through the panel. This causes the resulting audio to be especially quiet or loud at particular high frequencies, as compared with its intended volume. It will be understood that the frequencies that are affected will depend on the properties of the loudspeaker that determine the drum skin resonance of the loudspeaker, including and not limited to, the size of the inner region of the panel, the stiffness of the panel, the mass of the panel and/or the position of the drive unit relative to the panel. Accordingly, this can reduce the resulting sound quality that is produced by the speaker, such that the reproduced sound may not be an accurate replication of the original signal received by the speaker. The present inventors have thus sought a way to improve the audio performance of such flat panel loudspeakers.

[0008] By providing a biasing magnet supported in the inner region of the panel, the biasing magnet introduces a nonlinear force upon the panel that acts to damp the “drum skin” resonance effects of the panel response when driven by the drive unit. In particular, when the biasing magnet repels the one or more magnets of the drive unit, the biasing magnet rapidly damps the negative sinusoidal response (i.e. inward displacement) of the panel. Similarly, when the biasing magnet attracts the one or more magnets of the drive unit, the biasing magnet rapidly damps the positive sinusoidal response (i.e. outward displacement of the panel. In doing so, oscillations in the inner region of the resonant panel can be rapidly damped by the provision of the biasing magnet. Rapid damping of the oscillations in the inner region of the resonant panel reduces the risk of overly large oscillations experienced at the inner region from unallowably interfering, either constructively or destructively, with those in the outer region. The biasing magnet effectively causes the inner region of the panel to be more resistant to oscillations than a region of the resonant panel outside the inner region, whilst allowing the outer regions of the panel to continue to oscillate. The biasing magnet thus facilitates in distributing energy more uniformly over the surface of the panel, so as to give rise to an improved frequency response of the panel, as compared with loudspeakers of the prior art that do not include a biasing magnet. Accordingly, high frequency audio may be accurately reproduced in flat panel loudspeakers of the present disclosure, thereby improving the performance of the flat panel loudspeaker as compared with flat panel loudspeakers of the prior art that do not include a biasing magnet.

[0009] The biasing magnet may be configured to damp a response of the panel to a vibration caused by the drive unit.

[0010] The biasing magnet may be supported at the rear of the panel and configured to repel the one or more magnets. In doing so, when the panel is driven by the drive unit, the biasing magnet reduces the amplitude of oscillations particularly in the inner region of the panel, by damping the negative sinusoidal response of the panel. In doing so, high frequency audio may be accurately reproduced. When the biasing magnet is arranged at the rear of the panel and repels the one or more magnets of the drive unit, the size and weight of the biasing magnet may be advantageously reduced. This is because the biasing magnet is arranged relatively close to the one or more magnets of the drive unit and may therefore efficiently damp the response of the panel to the drive unit being driven. Furthermore, since the biasing magnet is arranged inside the flat panel loudspeaker, the front of the flat panel loudspeaker is provided by the front face of the panel, which is substantially flat and planar. As such, when installing the speaker into a mounting surface of a structure (such as a wall), a skim can be efficiently applied to the front of the speaker to make the speaker look “invisible”, i.e. substantially imperceptible to viewers.

[0011] The biasing magnet may be rigidly attached to the panel. For example, the biasing magnet may be adhered to the rear of the panel, using adhesive. The biasing magnet may be attached to the rear of the panel, using an overmolding process, whereby the biasing magnet and the panel are moulded together. By engaging the biasing magnet with the panel in this manner, the biasing magnet can be secured within the flat panel loudspeaker efficiently and precisely positioned. Moreover, the position of the biasing magnet may be held stably relative to the panel and the one or more drive units. In particular, affixing the biasing magnet in this manner reduces the risk of the biasing magnet being placed inaccurately and also of moving out of its intended position when the panel is driven by the drive unit, which would otherwise give rise to unintended distortion of the panel.

[0012] The flat panel loudspeaker may further comprise a coupler configured to couple the foot to the panel, and to support the biasing magnet at the rear of the panel. The biasing magnet may be attached to the coupler. The coupler may include an aperture to accommodate the biasing magnet. The coupler may include a coupling body and a support body, wherein the aperture is formed in the support body. The coupling body may be generally annular. The support body may include a plurality of support arms extending inwardly from the coupling body to the aperture. The biasing magnet may reside in the aperture and be adhered to the coupler, using adhesive. Alternatively, the biasing magnet and coupler may together provide an integral structure. For example, the biasing magnet may be integrally formed with the coupler using an overmolding process, whereby the biasing magnet and coupler are moulded together. By providing a coupler to support the biasing magnet at the rear of the panel, the separation distance between the biasing magnet and the drive unit may be further reduced, thereby reducing the size of the biasing magnet. Moreover, since the coupler has a two-fold purpose of coupling the drive unit to the panel and supporting the biasing magnet at the rear of the panel, the weight of the loudspeaker may be reduced because additional support structures are not required to support the biasing magnet. Furthermore, the biasing magnet may be arranged precisely and efficiently, since the position of the biasing magnet may be held stably relative to the one or more drive units. In particular, affixing the biasing magnet in this manner reduces the risk of the biasing magnet being placed inaccurately and also of moving out of its intended position when the panel is driven by the drive unit, which would otherwise give rise to unintended distortion of the panel.

[0013] The biasing magnet may be supported at the front of the panel and configured to attract the one or more magnets. In doing so, when the panel is driven by the drive unit, the biasing magnet damps the positive sinusoidal response of the panel and thus reduces the amplitude of oscillations particularly in the inner region of the panel. In doing so, high frequency audio may be accurately reproduced. By arranging the biasing magnet at the front of the panel, the biasing magnet may advantageously be used as an indicator for determining the depth of plaster/skim to be applied when the loudspeaker is being installed in a mounting surface, such as a wall.

[0014] The biasing magnet may be rigidly attached to the panel. For example, the biasing magnet may be adhered to the front of the panel, using adhesive. By engaging the biasing magnet with the coupler in this manner, the biasing magnet can be secured within the flat panel loudspeaker efficiently and precisely positioned. The biasing magnet may be attached to the front of the panel, using an overmolding process, whereby the biasing magnet and the panel are overmolded together.

[0015] A position of the biasing magnet being supported in the inner region of the panel may be predetermined, based on a magnetic flux density imparted by the one or more magnets. As such, the biasing magnet may be advantageously positioned to efficiently bias the panel against the distorted displacement enacted by the drive unit, for damping the response of the panel.

[0016] The biasing magnet may be supported substantially centrally in the inner region of the panel. This is particularly beneficial for a flat panel loudspeaker including a relatively high power drive unit, which imparts a substantially uniform magnetic flux density across the inner region of the panel. Generally speaking, relatively high power drive units can cause the panel to be displaced outwardly and inwardly by more than approximately 3mm with respect to its non-vibrational state, whereby the non-vibrational state of the panel is when the panel is not being excited by the drive unit. As such, positioning the biasing magnet substantially centrally in the inner region of the panel may efficiently damp the distorted displacement enacted by the drive unit, when the panel is driven.

[0017] The biasing magnet may be supported substantially non-centrally in the inner region of the panel. For example, the biasing magnet may be supported toward an edge of the inner region of the panel. This is particularly beneficial for a flat panel including a relatively low power drive unit, in which the magnetic flux density produced by the one or more magnets of the drive unit is substantially concentrated toward the edges of the inner region of the panel. Generally speaking, relatively low power drive units can cause the panel to be displaced outwardly and inwardly by approximately 3mm or less with respect to its non-vibrational state. As such, positioning the biasing magnet substantially non- centrally and particularly toward the edge of the inner region of the panel may efficiently damp the distorted displacement enacted by the drive unit, when the panel is driven.

[0018] The drive unit may further comprise a voice coil wound around the rear of the foot. The one or more magnets may be configured to provide an annular magnetic gap. The voice coil may be suspended in the annular magnetic gap.

[0019] The biasing magnet may be smaller than the one or more magnets. In doing so, the biasing magnet efficiently damps the response of the panel to the drive unit, whilst allowing the drive unit to still drive the panel so that the loudspeaker may still operate, and does not require structural changes to be made to the drive unit. Furthermore, providing a relatively small biasing magnet means that it can be efficiently supported in the inner region of the panel, without significant structural changes required to support the biasing magnet therein, whilst providing a lightweight loudspeaker. The biasing magnet may be a permanent bar magnet. In doing so, the biasing magnet may be efficiently and cost- effectively manufactured and installed in the flat panel loudspeaker.

[0020] The support frame may be configured to support the drive unit at the rear of the panel. In doing so, the support frame may be multifunctional in supporting both the panel and the drive unit, thereby providing greater structural integrity without requiring additional structural components.

[0021] According to a second aspect of the present disclosure, there is provided a kit of parts for manufacturing a flat panel loudspeaker, the kit of parts comprising: a panel having a front to face outwardly when mounted inside a structure, and a rear opposite the front, the panel being a resonant planar panel; a drive unit for exciting the panel into a vibrational state, the drive unit comprising one or more magnets and a foot arranged concentrically with the one or more magnets, wherein the foot is substantially cylindrical^ shaped having a front for coupling to the rear of the panel, and a rear opposite the front of the foot, wherein, when coupled to the rear of the panel, a cross-sectional area of the foot defines an inner region of the panel, and wherein, in use, the one or more magnets are configured to drive the foot to move axially relative to the one or more magnets so as to cause the panel to vibrate; a support frame for having a periphery of the panel fixedly mounted thereto, such that the periphery of the panel is configured to be fixedly mounted relative to the structure, when mounted inside the structure; and a biasing magnet for being supported in the inner region of the panel, wherein the biasing magnet is configured to repel the one or more magnets so as to bias the panel away from the one or more magnets, or wherein the biasing magnet is configured to attract the one or more magnets so as to bias the panel toward the one or more magnets. The panel, the drive unit, the support frame and the biasing magnet may each be as described hereinbefore.

[0022] The kit of parts may further comprise a coupler as defined hereinbefore.

[0023] The kit of parts may further comprise adhesive. The adhesive may be for adhering the biasing magnet to the front or the rear of the panel in the inner region. The adhesive may be for adhering at least a portion of the coupler to the biasing magnet. The adhesive may be for adhering the biasing magnet to the coupler inside the aperture. By engaging the biasing magnet with the panel or the coupler in this manner, the biasing magnet can be secured within the flat panel loudspeaker efficiently and precisely positioned. In the kit of parts, the adhesive may be provided ready-applied to one of the coupler and the planar panel. In some examples, the adhesive in the kit of parts may be provided separately from the biasing magnet, and the coupler.

[0024] According to a third aspect of the present disclosure, there is provided a method for manufacturing a flat panel loudspeaker, the method comprising: providing a panel having a front to face outwardly in use, and a rear opposite the front, the panel being a resonant planar panel; providing a drive unit for exciting the panel into a vibrational state, the drive unit comprising one or more magnets and a foot arranged concentrically with the one or more magnets, wherein the foot is substantially cylindrically shaped having a front for coupling to the rear of the panel, and a rear opposite the front of the foot, wherein a cross-sectional area of the foot is for defining an inner region of the panel when coupled to the panel, and wherein, in use, the one or more magnets is configured to drive the foot to move axially relative to the one or more magnets so as to cause the panel to vibrate; providing a support frame for having a periphery of the panel fixedly mounted thereto, such that the periphery of the panel is configured to be fixedly mounted relative to the structure, when mounted inside the structure; and supporting a biasing magnet in the inner region of the panel, wherein the biasing magnet is configured to repel the one or more magnets so as to bias the panel away from the one or more magnets, or wherein the biasing magnet is configured to attract the one or more magnets so as to bias the panel toward the one or more magnets.

[0025] The method may further comprise, prior to the step of supporting the biasing magnet, providing a coupler for coupling the foot to the rear of the panel and for supporting the biasing magnet at the rear of the panel, wherein the step of supporting the biasing magnet at the rear of the panel may be performed using the coupler. Thus, the coupler may provide a two-fold function of supporting the biasing magnet and coupling the drive unit to the panel, without requiring additional support structures and thereby leading to a lightweight loudspeaker. [0026] The method may further comprise securing the biasing magnet to the coupler by attachment means. For example, this may include using adhesive to adhere the biasing magnet to the coupler. The biasing magnet may be attached to the panel, using adhesive.

[0027] The step of providing the coupler may further comprise, prior to the securing the biasing magnet to the coupler, forming the coupler to include an aperture in the coupler, the aperture for accommodating the biasing magnet.

[0028] The step of securing the biasing magnet to the coupler may comprise inserting the biasing magnet into the aperture and securing the biasing magnet within the aperture using adhesive. [0029] The step of providing the coupler may further comprise providing the coupler and the biasing magnet as an integral unit. The coupler and the biasing magnet may be integrally formed, using an overmolding process.

[0030] The biasing magnet may be supported at the front of the panel. The biasing magnet may be attached to the front of the panel. This may include using adhesive or an overmolding process to attach the biasing magnet to the front of the panel.

[0031] The method may further comprise providing a layer of plaster to the front of the panel, such that the biasing magnet extends into the layer of plaster.

[0032] A position of the biasing magnet being supported in the inner region of the panel may be predetermined based on a magnetic flux density imparted by the one or more magnets when the panel is driven.

[0033] The biasing magnet may be supported substantially centrally in the inner region of the panel.

[0034] The biasing magnet may be supported substantially non-centrally in the inner region of the panel. [0035] It will be understood that the flat panel loudspeaker described herein need not necessarily be mounted inside a surface, but could in some examples form part of a speaker product such as for mounting on a surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Fig. 1 is a cross-sectional and partial side view of a speaker according to a first example of the disclosure; Fig. 2 is a graph showing the measured frequency response of the flat panel loudspeaker in Fig. 1 compared with a flat panel loudspeaker of the prior art;

Fig. 3a is a cross-sectional and perspective view of a biasing magnet and coupler assembly according to the first example of the disclosure;

Fig. 3b is an exploded view of Fig. 3a;

Fig. 4 is a cross-sectional and partial side view of a speaker according to a second example of the disclosure;

Fig. 5 is a cross-sectional and partial side view of a speaker according to a third example of the disclosure; and

Fig. 6 is a flow chart of a method of manufacturing a speaker according to the first example of the disclosure.

DETAILED DESCRIPTION

[0037] Fig. 1 shows a speaker 10 according to a first example of the disclosure. In particular, Fig. 1 illustrates a cross-sectional side view of the speaker 10. For the sake of illustration, the speaker 10 is illustrated in Fig. 1 in an x-y-z axis. The speaker 10 is a flat panel speaker or loudspeaker, which comprises a panel 12 having a front 14 that is substantially flat or planar. The panel 12 has a rear 16 opposite the front 14, such that the front 14 and rear 16 of the panel 12 are disposed in the x-y plane and arranged substantially parallel to one another, as shown in Fig. 1. The panel 12 of the first example is rectangular in shape having a width extending in the x direction, a length extending in the y direction and a depth extending in the z direction. The length of the panel 12 may be longer than the width of the panel 12. The depth of the panel 12 is in a range of 2 mm to 8 mm, and more particularly, in a range of 2 mm to 6 mm, and may be in a range of 3 mm to 4 mm. Flowever, the present disclosure is not limited to this shape or orientation, and may have a different polygonal shape, such as a circular shape or an oval shape, and any suitable dimensions.

[0038] The panel 12 is formed to be a resonant panel, and configured to resonate at predetermined frequencies, as is typical in flat panel loudspeakers. The panel may be provided as a multilayer panel having different composite layers. Such panels may be formed by any suitable means, for example by curing under heat and/or pressure. The panel may alternatively be formed of a uniform composition so as to provide a monolithic structure, rather than split into different composite layers.

[0039] The speaker 10 further includes a drive unit 24, which is coupled to the panel 12 via a coupler 26. The drive unit 24 is an electro-dynamic inertial vibration exciter that is used as a transducer, which, in practice, causes the panel 12 to vibrate and generate sound by virtue of the resulting vibrations encoded in an input audio signal. When caused to vibrate by the drive unit 24, the panel 12 acts to amplify received vibrations in a similar manner to a soundboard of a violin or piano such that the speaker 10 produces sound. The above description of the operation of the drive unit 24 and the panel 12 is provided merely for the convenience of the reader. The skilled person will understand the typical operation of flat panel loudspeakers. As shown in Fig. 1, the drive unit 24 is provided at the rear 16 of the panel 12. The drive unit 24 of Fig. 1 comprises a coil assembly and a magnet assembly adapted to move axially relative to each other.

[0040] The magnet assembly includes one or more magnets. In the first example of the disclosure, the magnet assembly includes a driving magnet 30, a top plate 31 and a bucking magnet 32. The drive unit 24 further includes a cup 33. Specifically, the driving magnet 30, top plate 31 and bucking magnet 32 are contiguously arranged so as to be stacked, whereby that the top plate 31 is interposed between the driving magnet 30 and the bucking magnet 32. The magnet assembly 30, 31, 32 is arranged substantially parallel to the panel 12 in an x-y plane, whereby the bucking magnet 32 is arranged to face the panel 12. As shown in Fig. 1, the panel 12 and the bucking magnet 32 are separated from one another. A magnetic gap is defined between the ends of the magnet assembly and the cup 33. It will be understood however that the disclosure is not limited to the magnet assembly of this example, and that the magnet assembly would be operable including one magnet only, such as the driving magnet.

[0041] The coil assembly comprises a coil 28 and a former 29. The coil 28 is a voice coil e.g. of wire. The former 29 is cylindrical so as to be tubular and arranged so as to be substantially perpendicular to the panel 12 and extend from the panel 12 via the coupler 26 into the magnetic gap. More specifically, the former 29 has a front connected to the panel 12 via the coupler 26, and a rear arranged in the magnetic gap, so as to surround the magnet assembly. The front end of the former 29 may be connected by means of an adhesive or the like to the coupler 26. In this way, the former 29 provides a foot by which the coil assembly is secured. The disclosure is not limited to a foot being provided by the former 29 of Fig. 1 , however, for example the drive unit could be secured to the resonant panel by fixing means, e.g. fasteners. Such fasteners may be releasable. Thus, a bayonet connector may provide a foot, one part of which is fixed to the resonant panel and the other part of which is formed integrally with the drive unit.

[0042] The coil 28 is wound around a rear region of the former 29, such that the coil is suspended in the magnetic gap. The cup 33 is arranged as a housing over the magnet assembly and coil 28. Typically, the coil assembly 28, 29 and magnet assembly 30, 31 , 32 are formed separately and then coupled together for later use through a suspension component or assembly.

[0043] The drive unit 24 further comprises circuitry (not shown), which is in wired or wireless communication with a transmitting device (not shown). The transmitting device is for transmitting a signal to the drive unit 24, whereby the signal includes audio data corresponding to audio for being reproduced by the speaker 10, such as music, etc. When caused to vibrate by drive unit 24, the resonant panel 12 acts to amplify these vibrations in a similar manner to a soundboard of a violin or piano such that the distributed mode vibrating panel loudspeaker 10 produces sound from the electrical signal. In practice, when the transmitting signal transmits a signal that is received by the circuitry of the drive unit 24, the circuitry drives the coil 28 within the magnetic gap via the magnet assembly, causing the former to axially move in the z-direction so as to cause the panel 12 to vibrate. The cup 33 and the bucking magnet 32 together advantageously reduce stray magnetic fields, so as to improve the efficiency of the energy transfer from the magnet 30 to the panel 12. However, the drive unit of the disclosure is not limited to this, and may be any suitable transducer for causing the panel to vibrate.

[0044] The drive unit 24 shown in Fig. 1 is a relatively high power drive unit which imparts a substantially uniform magnetic flux density across the inner region of the panel 12. The drive unit 24 can cause the panel to be displaced outwardly and inwardly by more than approximately 3mm with respect to a non-vibrational state of the panel 12. The nonvibrational state of the panel 12 is when the panel 12 is not being excited by the drive unit 24, so that the panel 12 has a substantially flat and non-distorted profile. It will however be understood that the disclosure is not limited to the drive unit 24 of Fig. 1 , and that in some examples of the disclosure, a relatively low power drive unit may be implemented, which imparts a substantially non-uniform magnetic flux density that is substantially concentrated toward the edges of the inner region of the panel. Such low power drive units may cause the panel to be displaced outwardly and inwardly by approximately 3mm or less with respect to the non-vibrational state of the panel. It will of course be appreciated that in examples of the disclosure whereby a plurality of drive units is included, the plurality of drive units may all be a low power drive unit, a high power drive unit or include a mix of both high and low power drive units.

[0045] The transmitting device can be disposed externally of the speaker 10, and may include any suitable device for transmitting the signal to the drive unit 24. For example, the transmitting device may include a smart phone, tablet, computer, and any other suitable portable and/or non-portable computing devices. Furthermore, the transmitting device may transmit the signal to the drive unit 24 using any suitable transmission means. For example, the drive unit 24 may include a wireless communication module to enable wireless communication (e.g. Bluetooth®, Wi-Fi, etc. communication) with a suitable transmitting device that has a counterpart wireless communication module. Such wireless communication configurations are particularly advantageous for enabling the drive unit 24 to receive audio input from portable devices. The drive unit 24 may otherwise, or additionally, be in wired communication with the transmitting device.

[0046] The circuitry of the drive unit 24 is configured to process the received input signal to generate a mechanical output for causing the panel 12 to vibrate. In particular, the vibrations generated by the mechanical output of the drive unit 24 have frequencies corresponding to the received input signal. It will be understood by the person skilled in the art that the circuitry of the drive unit 24 can have any suitable topology for processing the signal. Once the signal has been processed, the drive unit 24 outputs the mechanical output to the panel 12 via the coupler 26.

[0047] It will be understood by the skilled person that more than one drive unit may be provided for the panel, whereby each drive unit is tailored for causing the panel to vibrate at a predetermined set of frequencies. For example, one drive unit from among the drive units may cause the panel to vibrate at high frequencies, while another drive unit from among the drive units may cause the panel to vibrate at low frequencies. The person skilled in the art will understand where to dispose the drive units across the rear of the panel for optimal sound output. It will also be understood by the skilled person that in examples of the disclosure whereby a plurality of drive units is provided, a plurality of couplers is provided so that a coupler is provided for each drive unit. Typically, the drive unit 24 is an electromagnetic exciter, of any of the types commonly used in flat panel loudspeakers.

[0048] The drive unit 24 is adapted to be fixed in any convenient fashion to the resonant panel 12 of a distributed mode vibrating panel loudspeaker 10 to be excited to impart bending wave energy to the resonant panel 12 when an electrical signal is applied thereto. For example, the drive unit 24 may be coupled only to and supported only by the resonant panel and so the magnet assembly itself 30, 31, 32 forms an inertial mass to cause the coil assembly 28, 29 and resonant panel 12 (in this case a flat panel) to vibrate in use and so produce an amplified sound.

[0049] The speaker 10 also includes a support frame (not shown). The periphery of the panel is fixedly mounted to the support frame, so that when the flat panel loudspeaker is installed in a surface such as a wall, the panel is fixedly and stably mounted relative to the wall. In this way, movement of the panel 12 relative to the support frame is constrained around a boundary of the panel 12. [0050] In some examples of the disclosure, in addition to supporting the panel, the support frame may also support the drive unit. In such examples, the support frame is box shaped including a rear and four sides that extend perpendicularly from a periphery or outer boundary of the rear of the frame to a periphery or outer boundary of the panel in the z direction. The rear of the support frame can be substantially planar having approximately the same dimensions as the panel, and is arranged parallel to the panel in the x-y plane and rearward of the panel, while the sides of the support frame extend from the periphery of the rear of the support frame to the periphery of the panel. The support frame may be attached to the panel by any suitable means, for example using an adhesive coating or fastening means. The support frame as attached to the panel defines a cavity or space that is enclosed by the frame and the rear 16 of the panel. The space of the frame is dimensioned to accommodate the drive unit and the coupler, and supports the drive unit, the coupler and the panel together. The support frame may be formed from metal, for example steel, or from another material, such as carbon fibre.

[0051] In some examples, the speaker 10 can be for mounting inside a structure (not shown). More specifically, the speaker 10 can be mounted in a mounting surface. The mounting surface can be provided with an opening in an exposed surface of a structural component of a building, such as a wall, floor, ceiling, air conditioning unit, or the like. In examples of the disclosure, the opening in the mounting surface is defined by one or more cuts in the mounting surface, resulting in the opening in the mounting surface which is sufficiently deep to contain the speaker 10. The opening is typically of the same shape and slightly larger than the planar panel 12 to accommodate the panel 12 therein when mounted in the surface. Alternatively, the opening can be provided by means of the construction of the mounting surface. In other words, the mounting surface can be formed to have the opening defined therein, and its dimensions are predetermined to accommodate the speaker 10. In examples where the speaker is not rectangular-shaped, but is of another polygonal shape, the mounting surface is tailored such that its dimensions substantially match the speaker. In doing so, when the speaker is mounted inside the structure, such as within the opening of a wall, the front 14 of the panel 12 is disposed substantially flush with the surface of the structure, such as the wall surface that is facing outwards into a room, so as to face outwardly from the room.

[0052] In examples where the structure is a plastered wall, once the speaker 10 is mounted inside the structure so as to be substantially flush or not protruding therewith, a skim (not shown) can then advantageously be applied thereto. In particular, the skim that is applied to finish the plastered wall is also applied over the panel 12 of the speaker 10, thereby giving it substantially the same finish as the wall with which it is flush. This means that the speaker 10 can advantageously be made to look “invisible”, by virtue of its being accommodated and substantially hidden from view inside the structure, such that the speaker 10 is flush with, or not substantially protruding from the surfaces. It is however understood by the skilled person that applying a skim may not always be necessary, particularly when other forms of wall construction are used, such as drywall lining, in which drywall gypsum boards are attached to stud walls to form the wall surface. The drywall boards themselves provide the wall finish, and so no plastering or finishing skim is applied.

[0053] The support frame facilitates in the periphery of the panel being fixedly mounted relative to the structure, when mounted inside a structure. When further supporting the drive unit 24, the support frame as provided in the mounting surface of the wall provides the speaker 10 with greater structural integrity, as well as a protective casing for the drive unit 24, particularly for the rear of the drive unit 24 during installation in the mounting surface. In particular, the support frame ensures that when the panel 12 is mounted in the mounting surface, and when an operation of an drive unit 24 is causing the panel 12 to vibrate, the outer boundary of the panel 12 is fixed relative to the mounting surface. This helps to prevent any plaster layers covering the mounted speaker 10 from cracking or distorting. In this way, the speaker 10 can remain invisible in the mounting surface. However, the disclosure is not limited to this. For example, the periphery of the panel may be fixedly mounted to the support frame, without the support frame supporting the drive unit as described hereinbefore. In such examples, drive units may be inertially mounted to the panel. More specifically, the drive units may be arranged to brace against the panel using their own mass/inertia to cause the panel to vibrate and generate sound.

[0054] The speaker 10 further includes a biasing magnet 40 supported in an inner region of the panel 12, whereby a cross-sectional area of the former 29 of the drive unit 24 defines the inner region of the panel 12. As described above, the former 29 provides a foot that is axially driven by the magnetic assembly 30, 31, 32. The former 29 has a substantially cylindrical profile, whereby a cross-sectional area of the former 29 defines an inner region of the panel 12. In other words, the cross-sectional area of the former 29 bounds the inner region of the panel 12, and the inner region of the panel 12 faces the magnetic assembly 30, 31, 32.

[0055] In the first example of the disclosure and as shown in Fig. 1 , the biasing magnet 40 is supported at the rear 16 of the panel, so that a front of the biasing magnet 40 faces the rear 16 of the panel 12, and a rear of the biasing magnet 40 faces the magnetic assembly of the drive unit 24. Specifically, the biasing magnet 24 faces the bucking magnet 32. The biasing magnet 40 is configured to repel the magnet assembly 30, 31 , 32, whereby the rear of the biasing magnet 40 has an opposite polarity to the bucking magnet 32. It will of course be understood that in examples of the disclosure where the drive unit includes a different number of magnets, for example only one magnet, then the biasing magnet 40 faces that magnet and has an opposite polarity thereto. As can be seen from Fig. 1, a separation distance is provided between the biasing magnet 40 and the bucking magnet 32, whereby the separation distance is in the range of approximately 3 to 12 mm. The biasing magnet 40 is a permanent bar magnet and may comprise any suitable material such as neodymium. The biasing magnet may therefore be efficiently and cost- effectively manufactured and installed in the flat panel loudspeaker. However, the biasing magnet may be provided with any suitable shape in other examples of the disclosure.

[0056] By repelling the drive unit 24, this means that when the panel 12 is driven by the drive unit 24, the biasing magnet 40 reduces the negative sinusoidal response of the panel 12, by introducing a nonlinear force upon the panel 12, particularly in the inner region of the panel 12 which suffers from an exaggerated displacement as compared with the surrounding regions of the panel. In particular, the biasing magnet 40 repels the magnet assembly, 30, 31 , 32 of the drive unit, to accelerate the outward displacement while decelerating the inward displacement of the inner region of the panel.

[0057] In doing so, the biasing magnet 40 effectively causes the inner region of the panel 12 to be more resistant to oscillations than a region of the resonant panel outside the inner region, when the panel 12 is being driven by the drive unit 24. This damps the resonance effects of the panel in the inner region. In particular, the biasing magnet facilitates in distributing energy more uniformly over the surface of the panel, so as to give rise to an improved frequency response of the panel, as compared with loudspeakers of the prior art that do not include a biasing magnet. Specifically, oscillations in the inner region of the resonant panel can be rapidly damped by the provision of the biasing magnet. Rapid damping of the oscillations in the inner region of the resonant panel reduces the risk of overly large oscillations experienced at the inner region from unallowably interfering, either constructively or destructively, with those in the outer region. This can be particularly seen from Fig. 2, which illustrates the measured frequency response of the flat panel loudspeaker 10 of Fig. 1 (indicated by the solid line), as compared with a loudspeaker that includes all the features of the loudspeaker 10 of Fig. 1 except for the biasing magnet (indicated by the dotted line). More specifically, the flat panel loudspeaker used to generate the graph of Fig. 2 is the speaker 10 shown in Fig. 1, having the following specific dimensions. The panel has a length of 250 mm, a width of 200 mm, a depth of 2 mm, and an area density of 0.32 kg/m². One drive unit 24 is centrally positioned relative to the surface area of the rear 16 of the panel 12 and has the arrangement shown in Fig. 1. A layer of plaster having a depth of 2 mm was applied to the front of the panel 12. The inner region of the panel has a diameter of 30 mm. As discussed above and further below, it will be understood however that the disclosure is not limited to these dimensions, and that loudspeakers according to the present disclosure may have any suitable dimensions.

[0058] As shown in Fig. 2, when the biasing magnet is absent, the loudspeaker suffers from suboptimal audio performance because at least some high frequency sounds are not accurately reproduced between the audio input received by the drive unit and the audio output generate by the planar panel. In particular, the inventors have noticed that a region of “drum skin” resonance arises from an exaggerated displacement of the inner region of the panel when it is vibrated, where the vibrations of the inner region can detrimentally interfere with those in the region surrounding the inner region, particularly impacting the amplitude of the response in the distributed mode flat panel loudspeaker for certain high frequencies. This detrimental interference can result in a frequency response of the whole distributed mode vibrating panel loudspeaker, whereby the inner region is over vibrated in comparison to the outer regions, because the energy is not uniformly distributed through the panel. Frequencies above approximately 4 kHz are particularly impacted when the biasing magnet is absent from the loudspeaker 10 of Fig. 1 , with a dip in frequencies around 6 kHz being overly quietened due to destructive interference and a notch in frequencies around 12 kHz being amplified from constructive interference.

[0059] By contrast, when the biasing magnet 40 is present, the magnitude of the interference is reduced, so that the frequency response is more uniform, with high frequencies of above approximately 4 kHz being improved. As shown in Fig. 2, when the biasing magnet 40 is present, the dip at frequencies around 6 kHz in the absence of the biasing magnet is reduced, with those frequencies being significantly louder. Similarly, when the biasing magnet is present, the notch of amplified volume at frequencies around 12 kHz in the absence of the biasing magnet is also reduced, with those frequencies being significantly quieter and of a similar magnitude to the average across the frequency spectrum. Accordingly, audio may be accurately reproduced in flat panel loudspeakers of the present disclosure. With reference to Fig. 2, the presence of the biasing magnet 40 accurately reproduces high frequency audio above approximately 4kHz and particularly around 6 kHz and 12 kHz, thereby improving the high-frequency performance of the flat panel loudspeaker 10 as compared with when the biasing magnet 40 is absent.

[0060] It will however be understood that the disclosure is not limited to the above frequency bands, and that the biasing magnet may smooth different frequency bands depending on the drum skin resonance of the loudspeaker in question. In particular, the drum skin resonance of a loudspeaker will depend on its specific properties, including and not limited to for example the size of the inner region of the panel, the stiffness of the panel, the mass of the panel and the position of the drive unit relative to the panel. Accordingly, in other examples of the disclosure including loudspeakers having different properties, such as different panel dimensions, mass, stiffness properties, etc., different frequency bands to those shown in Fig. 2 may suffer dips and notches in the frequency response of the loudspeakers, as the exaggerated inner oscillations interfere with those in the outer surrounding regions. For example, if a loudspeaker having the same properties as that used in Fig. 2, but differing in that the panel has an inner region of approximately 19 mm, the drum skin resonance gives rise to dips and notches in the frequency response of the panel in the range of approximately 30 to 40 kHz. Similarly, a panel having an inner region of approximately 50 mm has a drum skin resonance giving rise to dips and notches in the frequency response of the panel in the range of approximately 2 to 6 kHz. In the same manner discussed above in relation to the loudspeaker 10 of Figs. 1 and 2, providing a biasing magnet in loudspeakers having different drum skin resonances acts to improve the frequency response at the affected frequency bands by reducing the exaggerated displacement of the inner region of the panel.

[0061] In the first example of the disclosure shown in Fig. 1 , by arranging the biasing magnet 40 at the rear 16 of the panel 12, the size and weight of the biasing magnet 40 may also be reduced due to the relative proximity of the biasing magnet 40 to the magnet assembly 30, 31, 32.

[0062] Furthermore, since the biasing magnet is arranged inside the flat panel loudspeaker, the front of the flat panel loudspeaker is provided by the front face of the panel, which is substantially flat and planar. This is particularly advantageous when installing the speaker into a mounting surface of a structure (such as a wall), since a skim can be applied efficiently to the front of the speaker to make the speaker look “invisible”, i.e. substantially imperceptible to viewers.

[0063] As can be seen from Fig. 1, the biasing magnet 40 is arranged substantially centrally within the inner region of the panel 12. However, the disclosure is not limited to this, and it will be understood that the position of the biasing magnet within the inner region may be determined based on the magnetic flux density in the inner region of the panel, caused by the magnets of the drive unit, and specifically, at the points of highest magnetic flux density imparted on the panel by the magnetic assembly. In the first example of Fig. 1, the biasing magnet 40 is arranged substantially centrally within the inner region of the panel 12, because the drive unit 24 imparts a substantially uniform magnetic flux density across the inner region of the panel 12. As such, placing the biasing magnet 40 generally centrally efficiently reduces the magnetic flux density in the inner region of the panel. [0064] However, in examples of the disclosure including a relatively low power drive unit which imparts a less uniform magnetic flux density across the inner region of the panel, the biasing magnet can be beneficially supported at a region of concentrated magnetic flux density, which may be at or toward an edge of the inner region of the panel. In doing so, the biasing magnet may efficiently repel the magnet assembly of the drive unit. The skilled person will understand how to determine where to position the biasing magnet most efficiently according to the magnetic flux density experienced at the panel.

[0065] In the first example of the disclosure, the biasing magnet 40 is supported by the coupler 26, such that the coupler has a two-fold purpose for coupling the drive unit 24 to the panel 12, as well as supporting the biasing magnet 40. The coupler 26 and biasing magnet 40 are shown in more detail in the perspective cross-sectional views of Figs. 3a and 3b, whereby Fig. 3a shows the coupler 26 assembled with the biasing magnet 40, and for illustration purposes, Fig. 3b shows an exploded view of the coupler 26 and biasing magnet 40 disassembled.

[0066] The coupler 26 comprises a coupling body 42, a support body 44 and an aperture 46. The coupling body 42 is generally annular with a peripheral lug connected to the former 29 of the drive unit 24. The coupling body 42 has an internal diameter approximating the diameter of the former 29, and may therefore be considered to approximate to the diameter of the inner region of the panel 12. The coupler used in the loudspeaker 10 to generate the graph of Fig. 2 is as shown in Figs. 3a and 3b, whereby the coupling body has an inner diameter of 30 mm to give rise to the inner region of the panel discussed above. However, the disclosure is not limited to this, and the coupler may have any suitable dimensions. The coupling body 42 may be connected to the former 29 by any suitable means, for example using adhesive such as glue. The support body 44 comprises a plurality of support arms that are substantially coplanar and extend inwardly from the annular coupling body 42 and converge together at a central portion that is substantially central within an area defined by the annular coupling body 42. The central portion includes the aperture 46, which is for accommodating the biasing magnet 40, and is dimensioned to the biasing magnet 40. The aperture 46 has a base and at least one side, and may not penetrate through the central portion of the coupler 26, which may improve the structural integrity of the coupler 26. Whilst Figs. 3a and 3b show the aperture 46 to be generally cylindrical, it will be understood that in other examples where the biasing magnet takes on a different shape, the aperture will dimensioned to accommodate the biasing magnet appropriately. The biasing magnet 40 is fitted into the aperture 46 by any suitable means, for example using adhesive such as glue. Alternatively, the biasing magnet may form an integral part of the coupler, for example by using an overmolding process to mould the biasing magnet integrally in the coupler. It will be understood that the coupler 26 may support the biasing magnet by any suitable means.

[0067] As shown in Figs. 3a and 3b, the support body 44 is for suspending the biasing magnet 40 via the aperture 46 substantially centrally within an area defined by the annular coupling body 42. In doing so, when the coupler 26 is mounted in the flat panel loudspeaker 10, the biasing magnet 40 may be substantially centrally supported in the inner region of the panel 12. The support body 44 may be reinforced at the annular coupling body 42 via its support arms, using a plurality of nails as shown in Figs. 3a and 3b. However, it will be understood that the support arms may be connected by any suitable manner, for example using adhesive, or using an overmolding process to mould the coupling body and support arms together to provide an integrally formed coupler. The coupler may comprise any suitable material, such as hard plastics. The plurality of support arms may include any suitable number, and may be evenly distributed around the periphery of the annular coupling body 42.

[0068] The disclosure however is not limited to the above described first example of the disclosure, with further examples now described.

[0069] Fig. 4 shows a loudspeaker 110 according to a second example of the disclosure. The loudspeaker 110 includes a panel 112 having a front 114 and a rear 116, and a drive unit 124 comprising a coil assembly 128, 129 and a magnet assembly 130, 131, 132, and a cup 133, each of which are substantially as described in the first example of the disclosure.

[0070] The loudspeaker 110 also includes a coupler 126 and a biasing magnet 140. The biasing magnet 140 is supported at the rear of the panel 112 in the inner region, and configured to repel the magnet assembly 130, 131, 132 of the drive unit 124. Whilst the description of the biasing magnet 40 of the above first example applies to the biasing magnet 140 of Fig. 4, the biasing magnet 140 differs from the biasing magnet 40 of the first example in that the biasing magnet 140 of the second example is not supported by the coupler 126, but is rather supported by the panel 112 itself. Specifically, the biasing magnet 140 is supported at the panel 112 by being connected to the panel rear 116 using adhesive, such as glue. However, it will be understood that the biasing magnet 140 may be connected by any other suitable means, for example using an overmolding process to integrally form the biasing magnet as part of the panel.

[0071] The coupler 126 comprises a coupling body that is generally annular shaped in substantially the same manner as the coupling body 42 of the coupler 26 of the first example of the disclosure. However, since the biasing magnet 140 is supported by the panel itself 112, the coupler 126 does not include the support body and aperture described in relation to the first example of the disclosure.

[0072] With the biasing magnet 140 being supported at the rear 116 of the panel and configured to repel the magnet assembly 130, 131, 132, the loudspeaker 110 of Fig. 4 also improves the quality of audio reproduced therefrom in a similar manner as the loudspeaker 10 of the first example described above. It will of course be understood that the biasing magnet may be supported in the inner region of the panel at a region of relatively high flux density, for example towards the edges of the inner region of the panel.

[0073] In the first and second examples of the disclosure, the biasing magnet is supported at the rear of the panel. However, the disclosure is not limited to this arrangement, with further examples described below.

[0074] Fig. 5 shows a flat panel loudspeaker 210 according to a third example of the disclosure. The flat panel loudspeaker 210 includes a panel 212, and a drive unit 224. The panel 212 has a front 214 and a rear 216, and the drive unit 224 comprises a coil assembly 228, 229, a magnet assembly 230, 231 , 232, and a cup 233. The panel 212 and drive unit 224 are substantially as described in the corresponding features of the first example of the disclosure. The loudspeaker 210 also includes a coupler 226, whereby the description in relation to the coupler 126 of the second example of the disclosure equally applies.

[0075] The loudspeaker 210 also includes a biasing magnet 240, which is supported at the front 214 of the panel 212 in the inner region, so that a rear of the biasing magnet 240 faces the front 214 of the panel 212, and a front of the biasing magnet 240 forms a front of the loudspeaker 210. Specifically, the rear of the biasing magnet 240 is connected to the front 214 of the panel 212 so as to be supported by the panel 212 itself using adhesive, such as glue. In doing so, the biasing magnet 240 may be held stably with respect to the panel 212. However, it will be understood that the biasing magnet 240 may be connected by any other suitable means, for example using an overmolding process to integrally form the biasing magnet as part of the panel.

[0076] The biasing magnet 240 shown in Fig. 5 is configured to attract the magnet assembly 230, 231 , 232 of the drive unit 224, whereby the rear of the biasing magnet 40 has an opposite polarity to the bucking magnet 232. It will of course be understood that in examples of the disclosure where the drive unit includes a different number of magnets, for example only one magnet, then the biasing magnet 240 faces that magnet and has an opposite polarity thereto. The biasing magnet 240 is a permanent bar magnet and may comprise any suitable material such as neodymium. The biasing magnet may therefore be efficiently and cost-effectively manufactured and installed in the flat panel loudspeaker. However, the biasing magnet may be provided with any suitable shape in other examples of the disclosure.

[0077] By attracting the drive unit 224, this means that when the panel 212 is driven by the drive unit 224, the biasing magnet 240 reduces the positive sinusoidal response of the panel 212 by introducing a nonlinear force upon the panel 212, particularly in the inner region of the panel 212 which suffers from an exaggerated displacement as compared with the surrounding regions of the panel. In particular, the biasing magnet 240 attracts the magnet assembly, 230, 231, 232 of the drive unit, to decelerate the outward displacement while accelerating the inward displacement of the inner region of the panel. By damping the resonance effects of the panel in the inner region are reduced, the biasing magnet 240 improves the quality of the audio to be reproduced in a similar manner as the loudspeaker 10 of Fig. 1.

[0078] In the third example of the disclosure as shown in Fig. 5, by arranging the biasing magnet 240 at the front 214 of the panel 212, this can advantageously facilitate in providing a tool for users to determine the depth of the plaster skim to be applied when installing the loudspeaker 210 in a surface such as a wall. In particular, a depth of the biasing magnet 240 defined between its front and rear and extending in the z direction can be predetermined by manufacturers as an intuitive means for users to approximate efficiently and accurately how thickly the skim should be applied. In doing so, the biasing magnet may be substantially flush with the applied skim.

[0079] The present disclosure further provides a method of manufacturing a speaker.

Fig. 6 shows a flow chart of the steps of a method of manufacturing a speaker, which will now be described. Broadly, the method comprises manufacturing a flat panel loudspeaker by supporting a biasing magnet in an inner region of a panel. In particular, the method comprises a first step 410 of providing the panel having a front and a rear opposite the front, a second step 420 of providing a drive unit and a third step 430 of providing a support frame. Each of the panel, the drive unit and the support frame may be as described hereinbefore, whereby the drive unit defines the inner region of the panel. The method includes a fourth step 440 of supporting a biasing magnet in the inner region of the panel. The biasing magnet may be as described hereinbefore. The method may include additional steps (not shown) of coupling the drive unit to the panel, which may be performed using a coupler. The coupler may be as described hereinabove.

[0080] Therefore, the method can be used to manufacture the examples of the flat panel loudspeaker as described herein.

[0081] A first example of the method is for manufacturing the loudspeaker 10 according to the first example of the disclosure. The first method includes supporting the biasing magnet 40 at the rear 16 of the panel 12. In this first example, the coupler 26 is provided for both coupling the drive unit to the panel, as well as supporting the biasing magnet 40, as described above. Providing the coupler 26 may include forming the coupler 26. In some examples, the biasing magnet may be integrally formed within the coupler, using for example an overmolding process. More particularly, a coupling body 42 and a support body 44 may be provided as described hereinabove, and form the coupler 26 by overmoulding polycarbonate so that the coupling body and support arms are provided as an integrally formed coupler 26. Of course, other suitable materials may be used, and the support body may itself be first provided as the individual support arms before being moulded together. The first example of the method may include forming the aperture 46 during the over-moulding process, while the support arms are all being moulded together. As described hereinbefore, the aperture 46 is for accommodating the biasing magnet 40, and has a base and at least one side, and may not penetrate through the entirety of the central portion of the coupler 26 as shown in Figs. 3a and 3b. The dimension of the aperture 46 is typically predetermined according to the biasing magnet 40. For example, if the biasing magnet 40 is substantially cylindrically shaped, the aperture 46 is correspondingly dimensioned to be cylindrically shaped. The person skilled in the art will understand that in some examples of the method, the coupler 26 may be provided premanufactured with or without the aperture 46 disposed therein. Furthermore, it will be understood that the disposition of the aperture 46 in the coupler 26 may be predetermined, for example based on where the magnetic flux density will be concentrated in use. The first example of the method may also include a step of applying an adhesive coating to the sides of the biasing magnet 40, prior to inserting the biasing magnet 40 into the aperture 46. In doing so, the biasing magnet 40 can be engaged with the aperture 46 via the adhesive disposed therein. However, the biasing magnet 40 may be secured to the aperture 46 by any suitable means. For example, the adhesive coating may instead be applied inside the aperture 46 rather than to the biasing magnet 40, prior to inserting the biasing magnet 40 into the aperture 46.

[0082] A second example of the method is for manufacturing the loudspeaker 110 according to the second example of the disclosure. In the second method, the biasing magnet 140 may be supported at the rear 116 of the panel 112 by using an adhesive, such as glue, or an overmolding process so that the biasing magnet 140 is supported by the rear of the panel 112 itself.

[0083] In a third example of the method for manufacturing the loudspeaker 210 according to the third example of the disclosure, the biasing magnet 240 may be supported at the front 214 of the panel 212 by using an adhesive, such as glue, or an overmolding process so that the biasing magnet is supported by the front of the panel 212 itself.

[0084] In some examples, the flat panel loudspeaker can be assembled from a kit of parts. The kit of parts typically includes the panel, the drive unit, the support frame and the biasing magnet described above, for example in isolation from one another, or partially assembled such that at least some further assembly is required to manufacture the flat panel loudspeaker.

[0085] In other examples of the disclosure, the coupler may be provided together with a drive unit that is configured to cause the panel to vibrate and generate sound, as in the first example of the disclosure. In particular, the method may include connecting the rear of the coupler to a corresponding mechanical output of the drive unit. The rear of the coupler may be connected to a front of the drive unit by any suitable means. However, in some examples of the method of the disclosure, the coupler is integrally formed with the drive unit so as to extend from the drive unit.

[0086] In examples of the disclosure where the support frame is a mounting box for housing the drive unit, the method further includes mounting the coupled drive unit and the panel in the support frame, so that the drive unit is enclosed in the space defined between the rear and sides of the support frame and the rear of the panel for supporting the drive unit and the panel together. In some examples of the method, a rear of the drive unit is also attached to the support frame so as to provide further structural integrity in supporting the drive unit to the panel. However, the disclosure is not limited to the mounting of the drive unit and the panel in the support frame in this way. For example, in examples of the disclosure whereby the drive unit is inertially mounted to the panel, the drive unit and the panel may be inserted within the mounting surface of the wall receiving the speaker, such that the drive unit is braced against the panel by its own inertia/mass.

[0087] In further examples of the disclosure, the support frame may be provided together with the panel, whereby an edge of the panel is bonded to the support frame.

[0088] Following the step of mounting the loudspeaker in a wall, the method may additionally include a step of applying a layer of plaster to the front of the panel as described hereinabove.

[0089] In the second example of the method, the layer of plaster may be applied to the front of the panel until the layer of plaster lies substantially flush with the front of the biasing magnet 240. In doing so, the biasing magnet 240 acts as a reference indicating the amount of plaster that is to be applied, since the layer of plaster is dimensioned according to the depth of the biasing magnet 240 protruding from the front 214 of the panel, such that the depth of the layer of plaster corresponds to the depth of the biasing magnet 240.

[0090] In summary, there is provided a flat panel loudspeaker (10) for mounting inside a structure, the flat panel loudspeaker comprising: a panel (12) having a front (14) to face outwardly when mounted inside a structure, and a rear (16) opposite the front, the panel being a resonant planar panel; a drive unit (24) for exciting the panel into a vibrational state, the drive unit comprising one or more magnets (30, 31, 32) and a foot (29) arranged concentrically with the one or more magnets, wherein the foot is substantially cylindrically shaped having a front coupled to the rear of the panel, and a rear opposite the front of the foot, wherein a cross-sectional area of the foot defines an inner region of the panel, and wherein, in use, the one or more magnets are configured to drive the foot to move axially relative to the one or more magnets so as to cause the panel to vibrate; a support frame having a periphery of the rear of the panel fixedly mounted thereto, such that the periphery of the panel is configured to be fixedly mounted relative to the structure, when mounted inside the structure; and a biasing magnet (40) supported in the inner region of the panel, wherein the biasing magnet is configured to repel the one or more magnets so as to bias the panel away from the one or more magnets, or wherein the biasing magnet is configured to attract the one or more magnets so as to bias the panel toward the one or more magnets.

[0091] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0092] Features, integers and characteristics described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0093] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

1 . A flat panel loudspeaker for mounting inside a structure, the flat panel loudspeaker comprising: a panel having a front to face outwardly when mounted inside a structure, and a rear opposite the front, the panel being a resonant planar panel; a drive unit for exciting the panel into a vibrational state, the drive unit comprising one or more magnets and a foot arranged concentrically with the one or more magnets, wherein the foot is substantially cylindrically shaped having a front coupled to the rear of the panel, and a rear opposite the front of the foot, wherein a cross-sectional area of the foot defines an inner region of the panel, and wherein, in use, the one or more magnets are configured to drive the foot to move axially relative to the one or more magnets so as to cause the panel to vibrate; a support frame having a periphery of the panel fixedly mounted thereto, such that the periphery of the panel is configured to be fixedly mounted relative to the structure, when mounted inside the structure; and a biasing magnet supported in the inner region of the panel, wherein the biasing magnet is configured to repel the one or more magnets so as to bias the panel away from the one or more magnets, or wherein the biasing magnet is configured to attract the one or more magnets so as to bias the panel toward the one or more magnets.

2. The flat panel loudspeaker of claim 1, wherein the biasing magnet is configured to damp a response of the panel to a vibration caused by the drive unit.

3. The flat panel loudspeaker of any one of the preceding claims, wherein the biasing magnet is supported at the rear of the panel and configured to repel the one or more magnets.

4. The flat panel loudspeaker of any one of claim 3, wherein the biasing magnet is rigidly attached to the panel.

5. The flat panel loudspeaker of claim 3, further comprising a coupler configured to couple the foot to the panel, and to support the biasing magnet at the rear of the panel.

6. The flat panel loudspeaker of claim 5, wherein the biasing magnet is attached to the coupler.

7. The flat panel loudspeaker of claim 6, wherein the coupler includes an aperture to accommodate the biasing magnet.

8. The flat panel loudspeaker of claim 1 or claim 2, wherein the biasing magnet is supported at the front of the panel and configured to attract the one or more magnets.

9. The flat panel loudspeaker of claim 8, wherein the biasing magnet is rigidly attached to the panel.

10. The flat panel loudspeaker of any one of the preceding claims, wherein a position of the biasing magnet in the inner region of the panel is predetermined based on a magnetic flux density imparted by the one or more magnets.

11. The flat panel loudspeaker of claim 10, wherein the biasing magnet is supported substantially centrally in the inner region of the panel.

12. The flat panel loudspeaker of claim 10, wherein the biasing magnet is supported substantially non-centrally in the inner region of the panel.

13. The flat panel loudspeaker of any one of the preceding claims, wherein the drive unit further comprises a voice coil wound around the rear of the foot, and wherein the one or more magnets are configured to provide an annular magnetic gap, the voice coil being suspended in the annular magnetic gap.

14. The flat panel loudspeaker of any one of the preceding claims, wherein the biasing magnet is smaller than the one or more magnets.

15. The flat panel loudspeaker of any one of the preceding claims, wherein the support frame is configured to support the drive unit at the rear of the panel.

16. A kit of parts for manufacturing a flat panel loudspeaker, the kit of parts comprising: a panel having a front to face outwardly when mounted inside a structure, and a rear opposite the front, the panel being a resonant planar panel; a drive unit for exciting the panel into a vibrational state, the drive unit comprising one or more magnets and a foot arranged concentrically with the one or more magnets, wherein the foot is substantially cylindrically shaped having a front for coupling to the rear of the panel, and a rear opposite the front of the foot, wherein, when coupled to the rear of the panel, a cross-sectional area of the foot defines an inner region of the panel, and wherein, in use, the one or more magnets are configured to drive the foot to move axially relative to the one or more magnets so as to cause the panel to vibrate; a support frame for having a periphery of the panel fixedly mounted thereto, such that the periphery of the panel is configured to be fixedly mounted relative to the structure, when mounted inside the structure; and a biasing magnet for being supported in the inner region of the panel, wherein the biasing magnet is configured to repel the one or more magnets so as to bias the panel away from the one or more magnets, or wherein the biasing magnet is configured to attract the one or more magnets so as to bias the panel toward the one or more magnets, wherein the panel, the drive unit, the support frame and the biasing magnet are as defined in any preceding claim.

17. The kit of parts of claim 16, further comprising a coupler as defined in any preceding claim.

18. The kit of parts of claim 16 or 17, further comprising adhesive.

19. A method for manufacturing a flat panel loudspeaker, the method comprising: providing a panel having a front to face outwardly in use, and a rear opposite the front, the panel being a resonant planar panel; providing a drive unit for exciting the panel into a vibrational state, the drive unit comprising one or more magnets and a foot arranged concentrically with the one or more magnets, wherein the foot is substantially cylindrically shaped having a front for coupling to the rear of the panel, and a rear opposite the front of the foot, wherein a cross-sectional area of the foot is for defining an inner region of the panel when coupled to the panel, and wherein, in use, the one or more magnets is configured to drive the foot to move axially relative to the one or more magnets so as to cause the panel to vibrate; providing a support frame for having a periphery of the panel fixedly mounted thereto, such that the periphery of the panel is configured to be fixedly mounted relative to the structure, when mounted inside the structure; and supporting a biasing magnet in the inner region of the panel, wherein the biasing magnet is configured to repel the one or more magnets so as to bias the panel away from the one or more magnets, or wherein the biasing magnet is configured to attract the one or more magnets so as to bias the panel toward the one or more magnets.

20. The method of claim 19, further comprising, prior to the step of supporting the biasing magnet, providing a coupler for coupling the foot to the rear of the panel and for supporting the biasing magnet at the rear of the panel, wherein the step of supporting the biasing magnet at the rear of the panel is performed using the coupler.

21. The method of claim 20, further comprising securing the biasing magnet to the coupler by attachment means.

22. The method of claim 21 , wherein the step of providing the coupler further comprises, prior to the securing the biasing magnet to the coupler, forming the coupler to include an aperture for accommodating the biasing magnet.

23. The method of claim 22, wherein securing the biasing magnet to the coupler comprises inserting the biasing magnet into the aperture and securing the biasing magnet within the aperture using adhesive.

24. The method of claim 20, wherein the step of providing the coupler further comprises providing the coupler and the biasing magnet as an integral unit.

25. The method of claim 19, wherein the biasing magnet is supported at the front of the panel.

26. The method of claim 25, further comprising providing a layer of plaster to the front of the panel, such that the biasing magnet extends into the layer of plaster.

27. The method of any one of claims 19 to 26, wherein a position of the biasing magnet being supported in the inner region of the panel is predetermined based on a magnetic flux density imparted by the one or more magnets when the panel is driven.

28. The method of claim 27, wherein the biasing magnet is supported substantially centrally in the inner region of the panel.

29. The flat panel loudspeaker of claim 27, wherein the biasing magnet is supported substantially non-centrally in the inner region of the panel.