CN111918181A

CN111918181A - Distributed mode loudspeaker

Info

Publication number: CN111918181A
Application number: CN202010787677.XA
Authority: CN
Inventors: 埃吉迪贾斯·米卡拉斯卡斯
Original assignee: Amina Technologies Ltd
Current assignee: Amina Technologies Ltd
Priority date: 2019-08-08
Filing date: 2020-08-07
Publication date: 2020-11-10
Also published as: GB201911348D0; GB2586959B; CN213126444U; GB2586959A

Abstract

The present disclosure provides a distributed mode loudspeaker (10) for installation within a structure and a method of manufacturing the same. The distributed mode loudspeaker (10) includes a planar panel (12), the planar panel (12) having a front side that faces outwardly when mounted within a structure and a rear side (16) opposite the front side. An exciter (24) is coupled to a rear side of the planar panel (12) and is configured to vibrate the planar panel (12) to generate sound. The support frame (38) has a rear side of the planar panel (12) fixedly mounted to the support frame (38) around a periphery of the rear side of the planar panel (12) such that the periphery of the planar panel (12) is configured to be fixedly mounted relative to the structure when mounted within the structure. At least one groove (30) is defined in the rear side (16) of the planar panel (12) and defines a thinned region of the planar panel (12) relative to a region of the planar panel (12) distal from the at least one groove (30).

Description

Distributed mode loudspeaker

Technical Field

The present disclosure relates to a distributed mode loudspeaker for mounting inside a structure and a method of manufacturing the same.

Background

It is often desirable to have some equipment that occupies an interior space of a room be mounted on walls or other surfaces, such as ceilings, within the room so as to be flush with these surfaces or so as to not substantially protrude from the surfaces. Distributed mode loudspeakers (sometimes referred to as flat panel loudspeakers) are particularly suitable for such applications because they can be mounted in openings defined in a surface of a building, such as a surface of a wall, floor or ceiling. Such distributed mode loudspeakers comprise a planar panel having a front surface which is arranged substantially flush with a surface, such as a wall. One common complaint with distributed mode loudspeakers mounted in this way is that the loudspeakers can be made invisible. Once such a distributed mode loudspeaker is mounted in an opening in a surface, which may be made generally inconspicuous by blending the surface with the boundaries of the loudspeaker, the planar panel of which forms part of the surface (or which defines an opening therein), so that the loudspeaker may be made invisible. For example, a thin plaster coating may be applied on the boundary of at least the front surface of the flat-panel speaker, so that it is difficult (or even impossible) to visually recognize the position or even the presence of the flat-panel speaker on the wall.

A distributed mode loudspeaker typically comprises a resonant panel having a front face which, in use, faces outwardly from the distributed mode loudspeaker, and a rear face opposite the front face. The exciter is generally mounted to a rear surface of the resonance panel through a coupler to cause the resonance panel to vibrate, with which the resonance panel generates sound. In this way, the placement of the exciter and coupler does not interfere with the mixing of the front surface of the resonant panel and the surface on which the distributed mode loudspeaker is to be mounted. The exciter and other components of a flat panel speaker may be protected by mounting in a mounting box or the like.

When a flat-panel speaker is mounted within a structure (e.g., a wall), structural features or other components may be present within the structure. Therefore, a space available for mounting the flat panel speaker may be limited. Typically, the low-frequency audio performance of a flat-panel speaker may be adversely affected by any limitations in the size of the resonant panel of the flat-panel speaker.

It is in this case that the present disclosure was devised.

Disclosure of Invention

According to a first aspect of the present disclosure there is provided a distributed mode loudspeaker for mounting within a structure, the distributed mode loudspeaker comprising: a planar panel having a front side facing outward when installed within a structure and a rear side opposite the front side; an exciter coupled to a rear side of the planar panel and configured to vibrate the planar panel to generate sound; and a support frame having a rear side of the planar panel fixedly mounted to the support frame about a periphery of the rear side of the planar panel such that, when mounted within the structure, the periphery of the planar panel is configured to be fixedly mounted relative to the structure, wherein the rear side of the planar panel defines at least one groove defining a thinned region of the planar panel relative to a region of the planar panel remote from the at least one groove.

The recess defines a thinned region of the panel such that the recess has a depth that extends into the rear side of the panel relative to a region of the panel remote from the recess. By providing one or more grooves in a planar panel, the inventors have discovered that the speaker of the present disclosure is capable of reproducing sound that more accurately replicates an input audio signal than a conventional flat panel speaker having the same dimensions. In particular, the loudspeaker of the present disclosure is capable of improving the sound quality of reproduced audio up to and including substantially 10kHz, particularly for low to mid frequency sounds, as follows: in a conventional flat panel speaker for mounting in a structure, the periphery of the panel is in use fixedly mounted relative to the structure in which it is mounted, such that displacement of the planar panel from its equilibrium position due to low frequency excitation by the exciter is resisted by the fixed mounting of the planar panel relative to the structure, which affects the low frequency audio performance of the flat panel speaker. It has been found that one cause of this phenomenon is the relative rigidity of the planar panel. A relatively rigid planar panel is still required to obtain accurate high frequency audio reproduction. In other words, a panel with a reduced elastic area generally degrades the quality of reproduced audio because the panel cannot be optimally displaced to reproduce the corresponding audio, and thus cannot effectively generate mid-low frequency vibrations. The inventors have found that the recess in the planar panel of the loudspeaker of the present disclosure provides a thinned region that is less resistant to the elasticity required to displace from the equilibrium state; in fact, it will be appreciated that any thinned region of the panel contributes to greater resilience of the panel as compared to a relatively thicker region of the panel. In this way, the panel can be sufficiently displaced from its equilibrium position to generate sound waves, particularly low to mid frequency sound waves, by effectively displacing the panel from its equilibrium position without increasing the area of the panel. Of course, it should be understood that while the present disclosure describes thinned regions provided by grooves, substantially similar effects may be achieved by substantially any planar panel having localized regions of the same location and configuration as at least one groove, which increases the local elasticity of the planar panel without thinning the panel in that region.

The planar panel may be fixedly mounted to the support frame around a periphery of a rear side of the planar panel. When the support frame is mounted into a structure during the process of mounting the flat-panel speaker into the structure, it is to be understood that the planar panel will be fixedly mounted relative to the structure.

The planar panel may include a plurality of layers. The plurality of layers of the planar panel may include a first layer forming a front side of the planar panel, a second layer forming a rear side of the planar panel, and one or more intermediate layers between the first layer and the second layer. The at least one groove may have a depth extending through the second layer. The at least one groove may have a depth extending to the one or more intermediate layers.

In other words, the one or more intermediate layers may provide a planar panel with a core layer having boundaries provided by the first layer and the second layer. The first and second layers may be provided by a surface layer, such as a paper surface layer. The one or more intermediate layers may be formed from one or more prepreg layers. The prepreg layer will be understood to be a woven or non-woven fibrous layer disposed in a resin. The resin may be semi-cured. Typically, the prepreg layer may be fully cured under the application of heat and/or pressure during the manufacture of the planar panel. Any recesses in the planar panel may be formed during manufacture before, during or after curing of the planar panel.

The depth of the planar panel may extend from the rear side to the front side of the planar panel, away from the at least one groove. The depth of the at least one groove may be less than two-thirds of the depth of the planar panel. The depth of the at least one groove may be less than half the depth of the planar panel.

A width of the at least one groove may be defined between a first edge of the at least one groove and a second edge of the at least one groove. The second edge may be spaced apart from the first edge. The width of the at least one groove may be greater than 1 mm. The width of the at least one groove may be greater than 2 mm. The width of the at least one groove may be less than 10 mm. The width of the at least one groove may be less than 5 mm.

The at least one groove may be at least one elongated groove having a groove length greater than a width of the at least one elongated groove. The elongate recess may be arranged to extend substantially parallel to the length of the planar panel. The length of the planar panel may be greater than the width of the planar panel. The groove length of the at least one groove may be greater than 50% of the length of the planar panel. The groove length of the at least one groove may be less than 90% of the length of the planar panel. However, the direction of the groove is not limited; the length of the at least one groove may extend substantially perpendicular to the length direction of the planar panel. In other words, the groove may extend in a direction defined by the shortest axis of the planar panel. In some examples, the at least one groove may be a plurality of grooves extending in a plurality of different directions.

By providing an elongate recess in this manner, the recess may facilitate displacement of the planar panel by bending the planar panel substantially along its long sides, thereby increasing the area of the panel that is subjected to resilience. However, the arrangement of the at least one groove is not limited thereto, and a groove parallel to the short side of the planar panel may be provided instead or in addition. The groove may be substantially straight for efficient manufacturing. However, the groove is not limited to this configuration and may be non-straight, e.g., curved, or any other suitable shape.

In other words, the groove may have one or more of the above-mentioned dimensions (i.e. the above-mentioned depth, width and/or length). Furthermore, the grooves are not limited to all grooves having the same dimensions, but have different depths, widths and lengths between different grooves, for example. By providing a groove having such dimensions (i.e., having the depth, width, and/or length described above), the groove increases the resiliency of the panel while maintaining the structural integrity of the panel and any skin applied thereto. In particular, such a groove size reduces the risk of the thinned region of the panel becoming too fragile and breaking, thereby maintaining the structural integrity of the panel. Furthermore, when the speaker is mounted within a structure such as a wall and the skin is coated to make the speaker "invisible", the skin (typically plaster or the like) is prone to cracking when over-displaced. Thus, by providing the groove dimensions, the structural integrity of the skin in use can also be maintained by reducing the effect of displacement of the panel on the coated skin.

The at least one groove may be defined by at least one wall. The at least one groove may be defined by at least two sidewalls. The at least two side walls may extend substantially straight towards the base. The at least two side walls may extend substantially parallel towards the base. The at least two sidewalls may extend obliquely toward the base. The at least two side walls may be substantially inwardly sloped such that an area of the at least two side walls at the rear side of the planar panel is farther toward the base than an area of the at least two side walls within the planar panel. This configuration of the at least one groove defining the cross-section of the at least one groove may allow for efficient manufacturing of the at least one groove. However, the groove is not limited to the above shape. The at least two sidewalls may be joined together to form a curved or pointed base. Thus, the cross-section of the groove may be substantially U-shaped or V-shaped. Such an inclined wall may provide the advantage of increasing the resilience of the panel by providing a recess wall at an obtuse angle to the rear surface of the panel, as compared to being parallel towards the wall.

The rear side of the planar panel may include at least one recessed region and a non-recessed region. The at least one groove may be defined within the at least one groove region. The non-recessed region may be substantially free of recesses. In other words, there may be no recess in the planar panel outside the at least one recess area. In other words, all of the grooves in the planar panel are contained within the at least one groove area. The at least one groove region may include a first groove region and a second groove region. The second recess region may be spaced apart from the first recess region. The non-recessed region may be between the first recessed region and the second recessed region. In other words, the first groove region, the non-groove region and the second groove region are arranged adjacent to each other. The non-recessed region may provide a central region of the panel, the recess being disposed outside the central region and towards an edge of the panel.

The audio performance of the distributed mode loudspeaker may be further improved by an arrangement in which the panel is divided into at least one recessed region and a non-recessed region. In particular, by providing the recess area towards the edge of the panel in this way, the resilience of the panel is further improved. As mentioned above, the periphery of the panel is fixedly mounted on the structure in use. In conventional loudspeakers this causes the region of the panel near its periphery to resist bending of the panel due to its proximity to the fixedly mounted periphery. In contrast, providing a recessed area towards the edge of the panel may locally reduce the stiffness of the panel, thereby increasing the elasticity of the local area. Thus, the non-recessed areas of the panel can be more displaced in response to a given low frequency audio input signal sent to the exciter. Thus, the panel is able to vibrate to a greater extent, particularly at low to mid frequencies, thereby improving the audio performance of the distributed mode loudspeaker. Furthermore, by providing non-grooved regions between the grooved regions so as to be substantially centrally disposed, the structural integrity of the panel is maintained in the regions most displaced from their equilibrium state, since here the panel is thicker than the grooves, the panel is relatively strong and therefore less prone to breaking or fracturing.

The first groove region may include a plurality of first grooves, and the second groove region may include a plurality of second grooves. By providing a plurality of grooves in the first and second groove regions in this manner, the first and second groove regions help to displace the panel from its equilibrium state while maintaining the structural integrity of the panel. The number of first grooves of the plurality of first grooves in the first groove region may be equal (e.g., exactly equal) to the number of second grooves of the plurality of second grooves in the second groove region.

The at least one groove may include at least two grooves spaced apart from each other by a predetermined spaced distance. The predetermined separation distance may be greater than 1 mm. The predetermined separation distance may be greater than 2 mm. The predetermined separation distance may be less than 10 mm. The predetermined separation distance may be less than 5 mm. The predetermined separation distance may be substantially equal to a width of the at least one groove. By providing a plurality of grooves with such a spacing distance, the grooves may collectively facilitate displacing the panel from its equilibrium state while maintaining the structural integrity of the panel and the surface on which the speaker is mounted. This is because the arrangement of the plurality of grooves ensures that the variation in the angle of any two adjacent portions of the front surface of the planar panel is reduced, the total variation in the angle of the front surface being dispersed over all the grooves. In other words, if the size and/or spacing of the grooves is as described above, the inventors have found that the risk of cracking of the gypsum is reduced because the stress exerted on the gypsum on the panel is distributed over a plurality of discrete areas on the panel, rather than being concentrated on only one area, which reduces the risk of the panel deforming such that the panel and/or any overlying gypsum fails (deforms to an unrecoverable level).

The at least one groove may comprise a plurality of grooves symmetrically distributed about the central axis of the planar panel. By providing a panel with a symmetrical profile of thinned and thickened regions, the weight of the panel can be evenly distributed when installed in use. In this way, the loudspeaker can be more securely supported in the structure in which it is mounted than in a panel in which the weight is asymmetrically distributed. Furthermore, due to the symmetrical form of the planar panel, the audio performance of the distributed mode loudspeaker can be more easily modelled. This is because the panel is less prone to the "rocking" effect that occurs when the panel is unbalanced. In particular, this rocking effect can cause uneven displacement of the corners of the panel, which in turn causes the exciter to bend, causing its component parts to rub against each other. For example, the voice coil of the driver of the exciter may rub against the metal parts of the exciter, which may cause audio distortion, especially at high amplification. In contrast, by providing a panel with a symmetric groove profile as described above, it is facilitated that the panel is displaced substantially symmetrically in response to an audio signal input to the exciter. For example, if a force is applied to a substantially central region of the panel, the displacement of the panel at each opposing corner is substantially similar, or even the same. However, those skilled in the art will appreciate that at least some of the technical effects of the present disclosure may still be achieved by asymmetric grooves.

The at least one groove may be disposed away from a periphery of the rear side of the planar panel. In this way, the periphery of the planar panel may be used to fixedly mount the speaker to a surface. Further, in examples where the front side of the planar panel includes a recessed region around a periphery of the front side of the planar panel, the at least one groove may be disposed away from the recessed region in an area bounded by the recessed region. It will be appreciated that the use of the recessed area allows the front surface of the planar panel to be recessed around the periphery, which facilitates the application of a gypsum skin to the boundaries of the planar panel and to the front surface of the structure to which the planar panel is mounted.

In some examples, the at least one groove may include a first groove extending in a first direction on the panel and then curving back in a second direction substantially opposite the first direction on the panel. In this way, a single groove may function in a similar manner to a plurality of spaced grooves. In some examples, this may be viewed as providing a plurality of grooves, at least because a notional line transverse to the rear side of the planar panel (which substantially traverses a portion of a first groove) will pass through a number of different spaced portions of the first groove.

According to another aspect of the present disclosure, a method of manufacturing a distributed mode loudspeaker for installation within a structure is provided. The method comprises the following steps: a planar panel is provided having a front side facing outward when installed in a structure and a rear side opposite the front side. When manufacturing the distributed mode loudspeaker, the planar panel is fixedly mounted to a support frame around the periphery of the rear side of the planar panel. The method also includes forming at least one groove in a back side of the planar panel, the at least one groove defining a thinned region of the planar panel relative to a region of the planar panel distal from the at least one groove; and coupling an exciter to a rear side of the planar panel. The exciter is configured to vibrate the planar panel to produce sound.

Accordingly, a method of forming the distributed mode loudspeaker disclosed herein is provided. It will be appreciated that the planar panel may be fixedly mounted to the support frame before or after the at least one recess is formed. Similarly, the exciter may be coupled to the rear side of the planar panel before or after forming the at least one groove. In some examples, the at least one groove may be formed during the manufacturing of the planar panel, for example in a stamping operation.

Forming the at least one groove may include using a groove forming tool. The recess forming tool may comprise a saw. The recess forming tool may comprise a routing tool, such as a drill. Thus, the groove can effectively pass through the rear side of the panel.

Forming the at least one groove may include cutting into at least a portion of the rear side of the planar panel.

Forming the at least one groove may include tearing at least a portion of the back side of the planar panel. The tearing may be performed outside the cutting, which is particularly advantageous for reducing the precision required for forming the grooves. Thus, the amount of time and resources required in the manufacturing process may be reduced. The tear is particularly useful for a planar panel formed from a plurality of layers, including a first layer and a second layer providing a front side and a back side, respectively, of the planar panel, wherein the first layer and the second layer are each formed from a sheet of paper, wherein the sheet of paper of the second layer is torn to form a portion of the groove.

Drawings

Embodiments of the present disclosure will be further described with reference to the accompanying drawings, in which:

fig. 1 is a schematic rear view of a loudspeaker according to an embodiment of the present disclosure;

fig. 2 is a perspective cross-sectional view of a second groove region of a panel of a speaker according to an embodiment of the present disclosure;

FIG. 3 is a graph of audio performance of a speaker according to an embodiment of the present disclosure compared to a speaker without a groove;

fig. 4 is a schematic rear view of a loudspeaker according to another embodiment of the present disclosure;

FIG. 5 is a rear perspective view of a support frame for a speaker according to another embodiment of the present disclosure; and

fig. 6 is a flowchart of a method of manufacturing a speaker according to a third embodiment of the present disclosure.

Detailed Description

The inventors have realized that prior art distributed mode loudspeakers or flat panel loudspeakers of the type described in the background section above suffer from poor audio performance because at least some of the low to mid frequency sound between the audio input received by the exciter and the audio output generated by the flat panel is not accurately reproduced. In particular, the inventors have noted that since the distributed mode loudspeaker is fixedly mounted at the periphery of the panel in use, the peripheral region of the panel remains substantially rigid and therefore cannot be displaced enough to vibrate to produce mid-low frequency sound in a relatively small size panel. This is particularly disruptive for accurately reproducing audio with mid-low frequency tones, as such reproduction requires the panel to have regions that can be sufficiently displaced at these low frequencies corresponding to the input audio. In particular, since the panel cannot be optimally displaced to reproduce corresponding audio, the panel having a less elastic region may reduce the efficiency of generating low frequency vibration. This may therefore result in poorer audio performance of the loudspeaker compared to larger distributed mode loudspeakers, so that the reproduced sound may not be an exact replica of the original signal received by the loudspeaker.

Conventional approaches solve this problem simply by increasing the size of the speaker panel to generate these low frequency vibrations in the panel, thereby producing corresponding sounds. If this is not done, the quality of the mid-low frequency audio may be degraded. Therefore, many conventional loudspeakers must be produced in large sizes to obtain high quality audio, but this is not always suitable for installation in structures, especially in domestic structures such as walls, ceilings and the like. In some instances, this can reduce the structural integrity of the structure in which it is located, due to the need to be accommodated in the large cavities of such structures.

The inventors therefore sought a way to improve the audio performance of such distributed mode loudspeakers.

Fig. 1 shows a loudspeaker 10 according to an embodiment of the present disclosure. Specifically, fig. 1 shows a rear view of the speaker 10. The loudspeaker 10 is a distributed mode loudspeaker, also referred to as a flat panel loudspeaker, comprising a panel 12. The panel 12 has a generally flat or planar front side. The panel 12 has a rear side opposite the front side such that the front and rear sides of the panel 12 are arranged substantially parallel to each other. The panel 12 is substantially rectangular parallelepiped in shape having a width W, a length L, and a depth D, wherein the width W, length L, and depth D extend perpendicular to one another as shown in fig. 1 and 2 (fig. 2 will be discussed in detail below). As shown in fig. 1, in this particular embodiment, the length L of the panel 12 is greater than the width W of the panel 12, but the present disclosure is not limited to this shape or orientation and may have a different shape, such as a circle or oval.

The panel 12 includes a plurality of layers to provide a multi-layer panel. The front layer defines the front side of the panel 12, the rear layer defines the rear side of the panel 12, and one or more intermediate layers are interposed between the front and rear layers. The intermediate layer provides the panel 12 with an interior or core layer having boundaries defined by the front and rear layers of the panel 12. However, the present disclosure is not limited to this configuration of the planar panel, and the panel may be formed of a uniform composition, rather than being separated into different composition layers. Typically, the front and back layers are provided by a surface layer (e.g., a paper surface layer). The one or more intermediate layers are formed from one or more layers of prepreg. Prepreg is to be understood as a layer of woven or non-woven fibres embedded in a resin, which hardens when cured. The planar panel 12 is typically formed by curing under heat and/or pressure, with the resin of one or more intermediate layers impregnated into the skin layers to form a strong, lightweight planar panel, well suited for use in distributed mode speakers of the type described herein. Many choices of materials for forming the layers of the panel will be apparent to those skilled in the art. Further, it will be appreciated that alternative structures may be used to provide a planar panel, so long as the panel is formed sufficiently robust to emit an acoustic output when vibrated by an exciter coupled thereto, as described further below.

The loudspeaker 10 also includes at least one driver 24 coupled to the panel 12. As shown in fig. 1, the exciter 24 is disposed on the rear side of the panel 12 and may be coupled to the panel 12 by any suitable means, such as a coupler (not shown). The exciter 24 is a transducer which, in effect, vibrates the panel 12 by an input audio signal applied to the exciter 24 to produce sound. In general, driver 24 is any type of electromagnetic driver commonly used in distributed mode speakers. When the vibration is caused by the exciter 24, the panel 12 outputs the applied displacement by the resonance action in a manner similar to a soundboard of a violin or piano, so that the speaker 10 produces sound. The above description of the operation of the exciter 24 and the panel 12 is provided for the convenience of the reader only. The typical operation of a distributed mode loudspeaker will be known to those skilled in the art. The exciter 24 includes circuitry, inputs and outputs (not shown). An input of the exciter 24 is in wired or wireless communication with a transmitting device (not shown) to receive an input audio signal therefrom, and an output of the exciter 24 is mechanically coupled to the panel 12.

The transmitting means is arranged to send a signal to the exciter 24, wherein the signal comprises audio data corresponding to the audio being reproduced by the loudspeaker 10, such as music or the like. The transmitting means may be arranged outside the loudspeaker 10, as shown in fig. 1, and may comprise any suitable means for transmitting signals to the exciter 24. For example, the transmitting means may comprise smart electronicsTablet computers, and any other suitable portable and/or non-portable computing device. Further, the transmitting means may transmit the signal to the exciter 24 using any suitable transmission means. For example, the exciter 24 may include a wireless communication module to enable wireless communication with a suitable transmitting device having a corresponding wireless communication module (e.g., Bluetooth)

Wi-Fi, etc.). This wireless communication configuration is particularly advantageous for enabling the exciter 24 to receive audio input from a portable device. Additionally or alternatively, the exciter 24 may be in wired communication with the transmitting device.

The circuitry of the exciter 24 is configured to process the received input signal to produce a mechanical output that causes the panel 12 to vibrate. Specifically, the vibrations produced by the mechanical output of the exciter 24 have a frequency corresponding to the received input signal. Those skilled in the art will appreciate that the circuitry of driver 24 may have any suitable topology for processing signals. Once the signal is processed, the exciter 24 outputs a mechanical output to the panel 12. Those skilled in the art will appreciate that more than one exciter may be provided for the panel 12, such that each exciter is tailored to vibrate the panel at a predetermined set of frequencies. For example, one of the exciters may vibrate the panel at a high frequency, while another of the exciters may vibrate the panel at a low frequency. Those skilled in the art will understand where the actuators are arranged on the rear side of the overall panel to obtain the best sound output, and/or how to determine how to tune the audio response of the panel for a given placement position of one or more actuators.

Speaker 10 also includes a plurality of recesses 30 disposed on the rear side of panel 12. Each recess 30 defines a thinned portion of the panel 12 relative to the area of the panel 12 remote from the recess 30. In other words, the groove 30 provides a depression in the rear side 16 of the panel 12 that extends to a depth into the panel 12. Fig. 2 is a detailed cross-sectional perspective view of the rear side 16 of the panel, detailing the groove 30. Specifically, fig. 2 shows the groove 30 as a cut-out area in the rear side 16 of the panel 12. The groove 30 may also be referred to as a channel or slot in the rear side 16 of the panel 12.

By providing the groove on the planar panel, the speaker can reproduce the sound reproducing the input audio signal more accurately than a conventional speaker of the same size. In particular, the loudspeaker of the present disclosure may improve the sound quality of reproduced audio up to and including substantially 10kHz, particularly for low to mid frequency sounds, especially in the range of about 20 to 500 Hz. In a conventional distributed mode loudspeaker intended to be mounted in a structure so as to be substantially invisible, the periphery of the panel is, in use, fixedly mounted relative to the structure in which it is mounted, so that only a relatively small area of the panel remote from the fixed area may be sufficiently resilient to be substantially displaced from its equilibrium position. However, a panel having such a small elastic region generally degrades the quality of reproduced audio because the panel cannot be optimally displaced to reproduce the corresponding audio, and thus cannot effectively generate mid-low frequency vibrations. In contrast, the recess in the planar panel of the loudspeaker of the present disclosure provides a thinned region that is less resistant to displacement from the equilibrium state; indeed, it will be appreciated that any thinned region of the panel contributes to the greater resilience of the panel as compared to thicker regions of the panel. In this way, the panel can be sufficiently displaced from its equilibrium position to generate sound waves, particularly low and medium frequency sound waves, by effectively displacing the panel from its equilibrium position without increasing the area of the panel. Accordingly, one skilled in the art will appreciate that the present disclosure is not limited to having a plurality of grooves. In fact, providing only one groove on the rear side of the panel will also improve the accuracy of audio reproduction compared to a panel without any groove.

In a first embodiment of the present disclosure, the rear side 16 of the panel 12 is divided into a recessed area and a non-recessed area, wherein the recessed area defines the panel area providing the recess 30 and the non-recessed area defines the panel area substantially free of the recess 30. More specifically, as shown in FIG. 1, the rear side 16 of the panel 12 includes a first recessed area 32, a second recessed area 34, and a non-recessed area 36 between the first recessed area 32 and the second recessed area 34, which are arranged parallel to one another. Thus, the rear side of the panel includes a substantially central region without grooves, with grooves 30 being located substantially outside the central non-groove region 36, towards the edge of the panel 12. As shown in fig. 1, a plurality of grooves 30 are disposed in a first groove region 32 and a second groove region 34 and are evenly distributed. In this embodiment, the first groove region 32 includes about 5 grooves 30 and the second groove region 34 includes about 5 grooves 30. In this way, the grooves 30 are distributed substantially symmetrically about the central long axis of the planar panel 12, thereby providing the panel 12 with a symmetrical profile of relatively thin and relatively thick regions. Thus, when installed in use, the weight of the panel may be evenly distributed so that speaker 10 may be more securely supported in the structure in which it is installed than a panel having an asymmetric distribution of weight.

By this arrangement of dividing the panel 12 into a grooved region and a non-grooved region, the reproduced audio quality is further improved. In particular, by providing the recessed

areas

32, 34 towards the edges of the panel in this way, the resilience of the panel is further improved. However, as shown in fig. 2, the groove 30 and the

respective groove regions

32, 34 are disposed away from the periphery of the rear side 16 of the panel 12 when disposed toward the edge of the panel 12. As mentioned above, the peripheral or outer boundary of the panel 12 is fixedly mounted in use to the structure, for example by adhesive or mechanical attachment thereto. In conventional loudspeakers, this makes the area of the panel near its periphery rigid also by virtue of being near the periphery of the fixed mounting. In contrast, providing a recessed area towards the edge of the panel reduces the rigidity of the panel, thereby increasing the resilience. Thus, the panel may vibrate, particularly from low to medium frequencies, to accurately reproduce audio. Furthermore, by interposing the non-recessed regions 36 between the recessed regions so as to be substantially centrally disposed, the structural integrity of the panel is maintained in the region that may be most out of its equilibrium state, since the panel is relatively stronger due to its relative thickness in this region and therefore less prone to breaking or fracturing.

Furthermore, due to the symmetrical form of the planar panel, the audio performance of the distributed mode loudspeaker can be more easily modelled. This is because the panel is less prone to the "rocking" effect that occurs when the panel is unbalanced. In particular, this rocking effect can cause uneven displacement of the corners of the panel, which in turn causes the exciter to bend, causing its component parts to rub against each other. For example, the voice coil of the driver of the exciter may rub against the metal parts of the exciter, which may cause audio distortion, especially at high amplification. In contrast, providing the panel with the above-described symmetrical groove profile facilitates the panel to be symmetrically displaced. For example, if the force is applied to a substantially central region of the panel, the amount of displacement of the panel at each opposing corner is substantially the same. However, those skilled in the art will appreciate that at least some of the technical effects of the present disclosure may still be achieved by asymmetric grooves.

In this embodiment of the present disclosure, the groove 30 is defined to have a predetermined size, which is particularly shown in fig. 1 and 2. As shown in fig. 2, the recess 30 of the first embodiment of the present disclosure has a depth extending to the intermediate layer 22 of the panel 12 that is about half the depth D of the panel 12. Here, the depth D of the panel 12 is defined between the rear side 16 and the front side of the panel 12. The groove 30 also has a width extending substantially orthogonal to the depth in the width W direction of the face plate 12, and is predetermined to be about 3 mm. The groove 30 also has a length extending in the direction of the length L of the panel 12, which is predetermined to be about 70% to 80% of the length L of the panel 12, as shown in fig. 1. In this way, the groove 30 is substantially elongated and narrow and arranged parallel to the long side of the panel 12, i.e. on the long axis of the panel 12. In this embodiment, the length L of the faceplate is about 300 mm, the width W of the faceplate is about 200 mm, and the depth D of the faceplate is about 5 mm.

A groove 30 having the above dimensions is particularly advantageous by increasing the resilience of the panel while maintaining the structural integrity of the panel and any skin applied thereto. In particular, such a groove size reduces the risk of the thinned region of the panel becoming too fragile and breaking, thereby maintaining the structural integrity of the panel. Furthermore, when a loudspeaker is mounted within a structure such as a wall and a skin is applied thereto to make the loudspeaker appear "invisible", the skin (which is typically plaster or the like) is prone to cracking when displaced excessively. Thus, by providing the current groove dimensions, the structural integrity of the skin may also be maintained by reducing the effect of panel displacement on the coated skin. Furthermore, by providing elongated grooves 30 parallel to the long axis of the panel 12, these grooves can facilitate bending of the panel substantially about an axis parallel to its long sides, thereby increasing bending of the panel for a given input force from the actuator 24.

In this embodiment, adjacent grooves 30 are spaced from each other by a distance substantially equal to the width of the grooves 30, i.e., about 3 mm. This is particularly illustrated in fig. 2, where the grooves 30 in the second groove region 34 are arranged consecutively side by side, each separated by a spacing distance or interval. In this way, the spacing separating each groove 30 is provided as a thickened region as compared to a thinned region of the groove to provide a substantially honeycomb or undulating cross-sectional profile. Here, the cross-sectional profile is drawn along the long axis of the second groove region 34 to define in a plane of length L. The grooves 30 in the first groove region 32 are similarly arranged at the above-described intervals. By providing a plurality of grooves 30 with such a spacing distance, the grooves together assist in displacing the panel from its equilibrium state while maintaining the structural integrity of the panel and/or any gypsum covering of the front surface of the panel. This is because the arrangement of the plurality of grooves can reduce the risk of the panel deforming causing the panel and/or any plaster to fail and thereby permanently deform the panel and/or plaster. In other words, providing a plurality of grooves with such spacing improves the ability of the panel and any stucco finish applied thereto to return to a given displaced equilibrium state, as described above.

However, the present disclosure is not limited to the above-described direction and size of the first embodiment of the present disclosure. For example, one skilled in the art will recognize that the panel does not include such an intermediate layer (e.g., if the panel is formed of a uniform composition), the grooves extend only to the rear side of the panel. Further, the size is not limited to the above, and is preferably as follows: the depth of the recess may be up to and including two thirds of the depth of the panel. The width may be equal to or greater than 1mm, preferably equal to or greater than 2mm, equal to or less than 10mm, and preferably equal to or less than 5 mm. The length of the groove may be in the range of 50% to 90% of the length of the panel. Further, the spacing distance is not limited to the above disclosure: the separation distance may be predetermined to be equal to or greater than 1mm, and preferably equal to or greater than 2 mm. The predetermined separation distance may be equal to or less than 10mm, preferably equal to or less than 5 mm.

Furthermore, the direction of the grooves is not limited to the above, and instead or in addition, the grooves may be arranged to extend along the minor axis of the panel instead of the major axis of the panel. For example, the grooves may be arranged parallel to the short sides of the panel, instead of parallel to the long sides as in the first embodiment shown in fig. 1 and 2. The grooves are also not limited to being substantially straight, and may take other configurations, such as wavy.

The benefit of the grooves on audio quality is particularly illustrated in fig. 3, which shows the audio results of the previously described speaker comprising five grooves in each of the first and second groove regions (solid line) compared to the sound reproduced by a conventional speaker without grooves (dashed line). More specifically, the audio results are plotted in a graph showing the levels (i.e., volumes) of the reproduced audio for the various speakers described above. As shown in fig. 3, the audio quality of a speaker without a notch includes multiple volume spikes at a given frequency throughout the audio spectrum. This results in the audio being produced differently from the original input signal, with some frequencies being amplified much more than they should be, and others being quieter than they should be. In contrast, speakers including notches in the faceplate improve overall sound quality by reducing the number of volume peaks and valleys to provide a smoother volume profile throughout the audio spectrum as compared to speakers without notches. Thus, the generated audio more accurately represents the input audio signal up to and including about 10kHz across the entire frequency spectrum, thereby improving the quality of the resulting audio. As particularly shown in fig. 3, the frequency spectrum from about 20Hz to about 500Hz is particularly improved by a smoother volume profile, resulting in better sound quality for the corresponding mid-low frequency audio. In addition, the volume of low-frequency audio (100Hz or less) is particularly increased. It can be seen that in the low frequency region from 20Hz to around 100Hz, the output sound level is increased relative to conventional distributed mode loudspeakers, which means that the low frequency audio performance of the distributed mode loudspeaker of the present disclosure is more similar in level to the audio performance at higher frequencies.

Fig. 2 shows a possible cross-sectional profile of the groove 30. The groove 30 is defined by sidewalls and a base that together form a cross-sectional profile. As shown herein, each groove 30 has two side walls parallel to each other to face oppositely. The two sidewalls intersect at a substantially planar base. The side walls and the base together define a substantially quadrilateral cross-sectional profile, such as a square or rectangle. This is particularly advantageous during manufacture because grooves having such oppositely facing grooves can be formed efficiently.

However, the present disclosure is not limited to such grooves and may provide different cross-sectional profiles. In some embodiments, the groove 30 may have two sidewalls that are substantially inclined toward each other and meet at a substantially planar base to provide a substantially V-shaped cross-sectional profile. In other embodiments, the sidewalls may obliquely intersect each other to form a curved or pointed base, rather than a planar base. By providing an angled side wall, an obtuse angle is defined where the side wall meets the rear surface of the panel. This may increase the resilience of the panel as the obtusely inclined side walls provide a substantially smoother rear surface profile which facilitates bending.

In other embodiments, the groove may comprise a single wall that is curved to provide a substantially U-shaped cross-sectional profile. However, the present disclosure is not so limited, and the grooves may produce a similarly shaped profile by providing two opposing parallel sidewalls that intersect the curved base.

As shown in fig. 2, the grooves 30 all have the same cross-sectional profile, which makes the manufacturing process more efficient without requiring different techniques to form the grooves. However, the present disclosure is not limited thereto, and the grooves may be formed with different cross-sectional profiles.

Fig. 4 shows a loudspeaker 10' according to another embodiment of the present disclosure. The loudspeaker 10 ' comprises a panel 12 ' and a driver 24 ', corresponding to the panel and the driver of the loudspeaker 10 in the first embodiment of the disclosure. Loudspeaker 10 ' further includes a support frame 38, with panel 12 ' fixedly mounted to support frame 38 around the periphery of panel 12 '. The support frame 38 also serves to assist in mounting the speaker 10' in a structure such as a wall. In some examples, the support frame 38 additionally serves to support the exciter 24'.

Fig. 5 shows a perspective view of a support frame 38 of another embodiment of the present disclosure, which includes frame portions that are substantially planar and have substantially the same dimensions as the panel 12'. The mounting frame is arranged parallel to and behind the panel 12'. The frame also includes sides that extend perpendicularly from the peripheral or outer boundary of the rear side of the frame to the peripheral or outer boundary of the panel 12'.

Typically, the support frame is attached to the rear side 16 'of the panel 12' by any suitable attachment means, such as by applying an adhesive coating between the abutting surfaces of the support frame and the rear side of the panel to bond the two together.

The support frame 38 connected to the panel 12 ' defines a cavity or space surrounded by the frame and the rear side 16 ' of the panel 12 '. The space of the frame is sized to receive the exciter 24 ' and support the exciter 24 ' and the panel 12 ' together. When loudspeaker 10 'includes the support frame 38 described above, the front side 14' of panel 12 'defines the front side of loudspeaker 10', the rear side of the mounting frame defines the rear side of loudspeaker 10 ', and the sides of the frame define the sides of loudspeaker 10'. The exciter 24 ' is typically a two-part electromagnetic exciter 24 ' having a first part (not separately shown) fixed to the support frame 38 and a second part (not separately shown) fixed to the panel 12 ', for example by a coupler (not shown). The first portion is moved relative to the second portion by energizing an electromagnet (a ferromagnetic member acting on the other of the first portion and the second portion) on one of the first portion and the second portion in response to an audio signal input to the actuator 24'.

The support frame 38 may be made of metal, such as steel, or other materials, such as carbon fiber.

Of course, those skilled in the art will appreciate that the support frame need not be exactly as described above in use, so long as the support frame is capable of supporting the exciter 24 'and the panel 12'. For example, the frame may include a plurality of sides without a rear side. In some examples, the exciter 24 may be inertially mounted to the panel 12, rather than to the support frame. In such examples, the panel 12 is caused to vibrate by the motion of the exciter 24, which exciter 24 is inertially supported by the mass of the exciter itself.

The loudspeaker 10' may be mounted within a structure in use. More specifically, the speaker 10' may be mounted in a mounting surface. The mounting surface may be provided with openings in the exposed surface of a structural component of a building, such as a wall, floor, ceiling, air conditioning unit, or the like. In an example of the present disclosure, the opening in the mounting surface is defined by one or more cutouts in the mounting surface such that the opening in the mounting surface is deep enough to accommodate the speaker 10'. The openings are generally of the same shape and are slightly larger than the planar panel 12 'to accommodate the panel 12' therein when it is installed in a surface. Optionally, the opening is provided by the configuration of the mounting surface. In other words, the mounting surface may be formed with an opening defined therein and sized to receive the speaker 10'. In an example where the speaker is not rectangular, but another polygonal shape, the mounting surface is sized to substantially match the speaker. Thus, when the speaker 10 'is mounted within a structure, such as within an opening in a wall, the front side of the panel 12' is substantially flush with a surface of the structure (e.g., the surface of the wall that faces outwardly toward the room) so as to face outwardly from the room.

Before the loudspeaker 10 'is mounted in the mounting surface, a box (not shown) with an open front side is first provided in the mounting surface, wherein the box is dimensioned as a loudspeaker 10'. The loudspeaker 10' is then mounted in the cabinet by its support frame 38. In other examples, the speaker 10 'may be provided in a case, and the case in which the speaker 10' has been provided may be mounted on a mounting surface.

In the example where the structure is a plaster wall, once the loudspeaker 10' is mounted within the structure so as to be substantially flush therewith or not to protrude therefrom, a skin (not shown) may advantageously be applied thereto. In particular, a skin for finishing a plaster wall is also applied to the panel 12 'of the speaker 10' so that it finishes substantially the same as a wall flush with it. This means that the loudspeaker 10 'may advantageously be designed to be "invisible" in that it is housed within the structure and is substantially invisible, such that the loudspeaker 10' is flush with the surface or does not substantially protrude from the surface. However, it will be appreciated by those skilled in the art that a coating skin is not always necessary, particularly when other forms of wall construction are used, such as drywall lining, where drywall gypsum board is attached to stud walls to form the wall surface. The drywall board itself provides wall finishing, and therefore does not have a gypsum or finishing skin applied.

The support frame 38, which is disposed in the mounting surface of the wall, provides greater structural integrity to the speaker 10 ' during mounting to the mounting surface, as well as providing a protective enclosure for the exciter 24 ', and in particular the rear side of the exciter 24 '. In particular, the support frame 38 ensures that the outer boundary of the panel 12 'is fixed relative to the mounting surface when the panel 12' is mounted within the mounting surface, and when operation of the exciter 24 'causes the panel 12' to vibrate. This helps prevent any gypsum layer covering the installed speaker 10' from cracking or deforming. In this way, the speaker 10' may remain invisible within the mounting surface. However, the present disclosure is not limited thereto. For example, the speaker may be provided without a support frame as described above. In such an example, the exciter may be inertially mounted to the panel. More specifically, the exciter may be arranged to be supported on the panel with its own mass/inertia to vibrate the panel and produce sound.

The present disclosure also provides a method of manufacturing a speaker. Fig. 6 shows a flow chart of the steps of a method 100 of manufacturing a loudspeaker, which will now be described.

The method 100 comprises a first step 110, wherein a planar panel is provided. The panel has a front side opposite the rear side and facing, in use, towards the exterior of the loudspeaker, wherein a periphery of the rear side of the panel is configured to be fixedly mounted, in use, relative to the structure. The planar panel may be as described above. In some examples, the first step 110 of providing a planar panel may include forming the panel, as described below. A plurality of layers having a predetermined composition are provided and stacked to arrange a front layer to form the front side 14 of the panel 12, a rear layer to form the rear side 16 of the panel 12, and one or more intermediate layers between the front and rear layers. The multiple layers are then secured to one another in a predetermined stacking order to form the panel 12 of the first embodiment of the present disclosure. The one or more intermediate layers may be one or more prepreg layers. The layers may be bonded together by pressing and curing by the application of suitable heat and pressure, sometimes referred to as autoclaving.

The method 100 further includes a second step 120 in which at least one recess is formed in the rear side of the planar panel. The recess may be as described above and may be formed in any suitable manner. For example, the grooves may be formed using a groove forming tool, such as using a saw, cutting tool, or the like. In this way, the groove can effectively and accurately pass through the rear side of the panel. However, the present disclosure is not limited thereto. In some examples of the disclosure, the groove is formed by tearing the back side of the panel, which may be done in addition to or instead of using a groove forming tool. For example, a cutting tool or the like may be used to make an initial cut to the panel, which may then be torn to provide the recess. In this way, the precision required to form the grooves is relatively low, thereby reducing the amount of resources and time required in the manufacturing process. The grooves may be formed in the panel in the same arrangement as described above, for example as shown in figures 1 and 2. The order of these steps is not particularly limited, and for example, any grooves may be formed in the planar panel before, during, or after pressing and curing the planar panel in manufacturing.

The method 100 also includes step 130, wherein the exciter is coupled to the back side of the panel. The actuator may be as described above. This coupling of the exciter and the panel may be achieved in any suitable manner. For example, the method 100 may further include additional steps (not shown), such as providing a coupler configured to couple to the exciter, coupling the coupler to the exciter, and coupling the coupler to the back side of the panel, which may be performed in any order. Thus, the method may be used to manufacture a distributed mode loudspeaker as described herein.

In some examples of the disclosure, the method may comprise an additional step in which a support frame is mounted, the support frame being configured to securely mount the loudspeaker to a structure in use. In particular, the support frame may comprise a frame having a rear portion and side portions as described above. The mounting of the support frame may include attaching the support frame to the periphery of the panel, for example applying an adhesive to the periphery of the support frame, and seating the periphery of the support frame against the periphery of the panel to enclose the exciter within the frame, as described above. In other words, the exciter is enclosed within a space defined between the support frame and the rear side of the panel to support the exciter and the panel together. In some examples of this approach, the rear of the exciter is also attached to the support frame to provide further structural integrity when supporting the exciter to the panel. However, the present disclosure is not limited to mounting the exciter and the panel in the support frame in this manner. For example, in examples of the present disclosure, the exciter is inertially mounted to the panel (see above), and the exciter and panel may be inserted into the mounting surface of the wall housing the speaker, such that the exciter is supported on the panel by its own inertia/mass.

In summary, a distributed mode loudspeaker (10) for installation within a structure is provided. A distributed mode loudspeaker (10) comprises a planar panel (12), the planar panel (12) having a front side which faces outwardly when mounted within a structure and a rear side (16) opposite the front side. An exciter (24) is coupled to a rear side of the planar panel (12) and is configured to vibrate the planar panel (12) to generate sound. The support frame (38) has a rear side of the planar panel (12) fixedly mounted to the support frame (38) around a periphery of the rear side of the planar panel (12) such that the periphery of the planar panel (12) is configured to be fixedly mounted relative to the structure when mounted within the structure. At least one groove (30) is defined in the rear side (16) of the planar panel (12) and defines a thinned region of the planar panel (12) relative to a region of the planar panel (12) distal from the at least one groove (30).

Throughout the description and claims of this specification, the words "comprise" and "comprise", and variations of the words "comprise" and "comprising", mean "including but not limited to", and are not intended to (and do not) exclude other components, integers or steps. Throughout the specification 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.

Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the disclosure 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 and/or steps in which at least some of such features are mutually exclusive. The present disclosure is not limited to the details of any of the foregoing embodiments. The disclosure 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.

Claims

1. A distributed mode loudspeaker for installation within a structure, the distributed mode loudspeaker comprising:

a planar panel having a front side facing outward when installed within a structure and a rear side opposite the front side;

an exciter coupled to a rear side of the planar panel and configured to vibrate the planar panel to generate sound; and

a support frame having a rear side of the planar panel fixedly mounted to the support frame about a periphery of the rear side of the planar panel such that when mounted within the structure, the periphery of the planar panel is configured to be fixedly mounted relative to the structure;

wherein the rear side of the planar panel defines at least one recess defining a thinned region of the planar panel relative to a region of the planar panel remote from the at least one recess.

2. The distributed mode loudspeaker of claim 1, wherein the planar panel comprises a plurality of layers;

wherein the plurality of layers of the planar panel comprise a first layer forming a front side of the planar panel, a second layer forming a rear side of the planar panel, and one or more intermediate layers between the first layer and the second layer;

wherein the at least one groove has a depth extending into the one or more intermediate layers.

3. The distributed mode loudspeaker of claim 1 or 2, wherein the depth of the planar panel extends from the rear side to the front side of the planar panel, away from the at least one groove, and the depth of the at least one groove is less than 70% of the depth of the planar panel, and

preferably, the depth of the at least one recess is less than 60% of the depth of the planar panel.

4. A distributed mode loudspeaker according to any preceding claim, wherein the width of the at least one groove is defined between a first edge and a second edge spaced from the first edge, and wherein the width of the at least one groove is greater than 1mm, preferably greater than 2 mm.

5. A distributed mode loudspeaker according to any preceding claim, wherein the width of the at least one groove is defined between a first edge and a second edge spaced from the first edge, and wherein the width of the at least one groove is less than 10mm, preferably less than 5 mm.

6. A distributed mode loudspeaker according to any preceding claim, wherein the at least one recess is defined by at least two side walls extending substantially straight towards the base.

7. The distributed mode loudspeaker of claim 6, wherein said at least two sidewalls extend substantially parallel toward said base.

8. The distributed mode loudspeaker of any preceding claim, wherein the rear side of the planar panel comprises at least one recessed area and a non-recessed area,

wherein the at least one groove is defined within the at least one groove region;

wherein the non-recessed region is substantially free of recesses.

9. The distributed mode loudspeaker of claim 8, wherein the at least one groove region comprises a first groove region and a second groove region spaced apart from the first groove region, the non-groove region being interposed between the first groove region and the second groove region.

10. The distributed mode loudspeaker of claim 9, wherein the first groove region comprises a plurality of first grooves and the second groove region comprises a plurality of second grooves, wherein the number of first grooves is equal to the number of second grooves.

11. A distributed mode loudspeaker according to any preceding claim, wherein the at least one recess comprises at least two recesses spaced from each other by a predetermined spacing distance, the predetermined spacing distance being greater than 1mm, preferably greater than 2 mm.

12. A distributed mode loudspeaker according to any preceding claim, wherein the at least one recess comprises at least two recesses spaced from each other by a predetermined spacing distance, the predetermined spacing distance being less than 10mm, preferably less than 5 mm.

13. A distributed mode loudspeaker as claimed in claim 11 or 12, wherein said predetermined separation distance is substantially equal to the width of said at least one groove.

14. The distributed mode loudspeaker of any of the preceding claims, wherein the at least one groove comprises a plurality of grooves distributed symmetrically about a central axis of the planar panel.

15. The distributed mode loudspeaker of any of the preceding claims, wherein the at least one groove is at least one elongate groove, the at least one elongate groove having a groove length along the planar panel that is greater than a width of the at least one elongate groove.

16. The distributed mode loudspeaker of claim 15, wherein the planar panel has a panel length greater than a panel width, and wherein the elongate groove extends along a direction of the groove length that is substantially parallel to the direction of the panel length.

17. The distributed mode loudspeaker of any preceding claim, wherein the at least one recess is disposed away from a periphery of the rear side of the planar panel.

18. A method of manufacturing a distributed mode loudspeaker for installation in a structure, the method comprising the steps of:

providing a planar panel having a front side facing outwardly when mounted within a structure and a rear side opposite the front side, the planar panel being fixedly mounted to a support frame around the periphery of the rear side of the planar panel when the distributed mode loudspeaker is manufactured;

forming at least one groove in a rear side of the planar panel, the at least one groove defining a thinned region of the planar panel relative to a region of the planar panel distal from the at least one groove; and

coupling an exciter to a rear side of the planar panel, the exciter configured to vibrate the planar panel to produce sound.

19. The method of claim 18, wherein forming the at least one groove comprises using a groove forming tool.

20. The method of claim 19 wherein the groove forming tool comprises a saw.

21. The method of any of claims 18 to 20, wherein forming the at least one groove comprises cutting into at least a portion of a rear side of the planar panel.