Flat panel loudspeaker

Abstract

Circular flat panel loudspeaker comprising a resonant with a rear surface opposite the front surface. An exciter is provided at an axial centre of panel and coupled to the rear surface of the panel to cause the panel to vibrate, on operation of the exciter, to generate sound. A frame is provided for mounting in the surface and having the rear surface of the panel fixed thereto around the whole of the outer boundary of the panel, such that when mounted in the mounting surface and when the panel is caused by the exciter to vibrate on operation of the exciter, the outer boundary of the panel is fixed relative to the mounting surface. Means are provided to induce non-circularly symmetric distortion of natural modes of oscillation of the panel, the support frame and the exciter absent the mode distribution means

Claims

1. A flat panel loudspeaker adapted to be mounted in a mounting surface, comprising: a resonant panel insertable into a circular opening in the mounting surface and including opposing front and rear surfaces, wherein the front surface has a substantially circular outer boundary and faces outwardly when the flat panel loudspeaker is mounted in the mounting surface; an exciter coupled to the rear surface of the resonant panel substantially at an axial center of the resonant panel and operable to cause the resonant panel to vibrate to generate sound; a support frame for mounting in the mounting surface, wherein the rear surface of the resonant panel is coupled to the support frame around substantially the outer boundary of the resonant panel, and wherein when mounted in the mounting surface and when the resonant panel is caused by the exciter to vibrate, the outer boundary of the resonant panel is fixed relative to the mounting surface; and a component coupled to the resonant panel near the exciter, proximal to the axial center of the resonant panel, to add weight to the resonant panel to induce non-circularly symmetric distortion of natural modes of oscillation of the resonant panel in response to operation of the exciter in an assembly of the resonant panel, the support frame, and the exciter that occur absent the component.

2. The flat panel loudspeaker as claimed in claim 1, wherein the component is configured to induce non-rotationally symmetric distortion of natural modes of oscillation of the resonant panel in response to operation of the exciter in the assembly of the resonant panel, the support frame and the exciter absent the component.

3. The flat panel loudspeaker as claimed in claim 1, wherein the one or more components are formed from non-toxic metal.

4. The flat panel loudspeaker as claimed in claim 1, wherein the one or more components are coupled to the resonant panel away from the center of the resonant panel in a direction along the rear surface of the resonant panel.

5. The flat panel loudspeaker as claimed in claim 4, wherein the component includes at least two components, and wherein each of the at least two components is differently spaced from the center of the resonant panel.

6. The flat panel loudspeaker as claimed in claim 5, wherein the at least two components are spaced apart over a region of at least 60 degrees relative to the center of the resonant panel.

7. The flat panel loudspeaker as claimed in claim 5, wherein the at least two components is at least four components, and wherein a maximum angular spacing between any two components of the at least four components, relative to the center of the resonant panel, is less than 180 degrees.

8. The flat panel loudspeaker as claimed in claim 1, wherein the one or more components are coupled to the rear surface of the resonant panel.

9. The flat panel loudspeaker as claimed in claim 1, wherein a center of mass of an assembly of the resonant panel and the component is away from a center of the resonant panel in a direction along the front surface of the resonant panel.

10. The flat panel loudspeaker as claimed in claim 1, wherein the exciter is coupled to the rear surface of the resonant panel via a foot, and wherein the component is provided at one or more regions of the resonant panel outside the foot.

11. The flat panel loudspeaker as claimed in claim 1, wherein the component is arranged to be asymmetric relative to any line of symmetry through the center of the resonant panel.

12. The flat panel loudspeaker as claimed in claim 1, wherein the resonant panel includes at least one selected from among: an outer diameter of less than about 30 centimeters (11.81 inches), and a maximum thickness of the resonant panel is less than about 3 millimeters (0.118 inches).

13. The flat panel loudspeaker as claimed in claim 1, wherein the resonant panel has a substantially constant density per unit area across the front surface of the resonant panel.

14. The flat panel loudspeaker as claimed in claim 1, wherein the resonant panel has a stiffness that is sufficient to cause at least one selected from among: sound having a high frequency over 10 kHz to be emitted from the resonant panel when the exciter is operated at substantially the high frequency, and sound having a low frequency below 100 Hz to be emitted from the resonant panel when the exciter is operated at substantially the low frequency.

15. The flat panel loudspeaker as claimed in claim 1, wherein the resonant panel includes an inner region and a boundary region surrounding the inner region and extending to the outer boundary of the resonant panel, and wherein the front surface of the resonant panel in the boundary region is defined by a depression relative to at least a portion of the front surface of the resonant panel in the inner region.

16. The flat panel loudspeaker as claimed in claim 1, wherein the resonant panel is a pressed panel.

17. A method of mounting a flat panel loudspeaker in a mounting surface, the flat panel loudspeaker including a resonant panel insertable into a circular opening in the mounting surface and having opposing front and rear surfaces, wherein the front surface has a substantially circular outer boundary and faces outwardly when the flat panel loudspeaker is mounted in the mounting surface, and the resonant panel further having a rear surface opposite the front surface, an exciter coupled to the rear surface of the resonant panel substantially at an axial center of the resonant panel and operable to cause the resonant panel to vibrate to generate sound, a support frame for mounting in the mounting surface, wherein the rear surface of the resonant panel is coupled to the support frame around substantially the whole of the outer boundary of the resonant panel, and wherein when mounted in the mounting surface and when the resonant panel is caused by the exciter to vibrate, the outer boundary of the resonant panel is fixed relative to the mounting surface, and a component coupled to the resonant panel near the exciter, proximal to the axial center of the resonant panel, to add weight to the resonant panel to induce non-circularly symmetric distortion of natural modes of oscillation of the resonant panel in response to operation of the exciter in an assembly of the resonant panel, the support frame and the exciter that occur absent the component, the method comprising: forming a circular opening in the mounting surface having a diameter greater than a diameter of the outer boundary of the resonant panel; inserting the flat panel loudspeaker in the circular opening; and securing the support frame at the mounting surface, wherein the front surface of the resonant panel faces outwardly and is substantially flush to the mounting surface.

18. The method as claimed in claim 17, after the step of securing the support frame at the mounting surface further comprising applying a covering to the mounting surface, wherein the covering extends over at least an interface between the mounting surface and the resonant panel.

19. The method as claimed in claim 18, wherein the covering is plaster.

20. The flat panel loudspeaker as claimed in claim 1, wherein the resonant panel includes a skin layer composed of a fibre-based material and a core layer formed from a matrix construction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a simulated frequency response for a resonant panel of a circular flat panel loudspeaker, with and without a mode distribution means;

(3) FIGS. 2A to 2D are schematic representations illustrating the displacement at two different resonant modes for each of two different resonant panels;

(4) FIG. 3 is an illustration of a circular flat panel loudspeaker;

(5) FIG. 4 is a further illustration of the flat panel loudspeaker of FIG. 3;

(6) FIG. 5 is an illustration of a cross-section through the flat panel loudspeaker of FIGS. 3 and 4;

(7) FIG. 6 is an illustration of an underside of the resonant panel of the flat panel loudspeaker of FIGS. 3 to 5;

(8) FIG. 7 is a schematic illustration of a resonant panel for use with the flat panel loudspeaker of FIGS. 3 to 5; and

(9) FIG. 8 is an illustration of an underside of a further example of a resonant panel for the flat panel loudspeaker shown in FIGS. 3 to 5.

DETAILED DESCRIPTION

(10) The present disclosure describes a flat panel loudspeaker which is easy to install and suitable for mass-market use.

(11) FIG. 3 is an illustration of a circular flat panel loudspeaker. The flat panel loudspeaker 1 is for mounting in a mounting surface (not shown) and comprises a resonant panel 10, an exciter 30 (see FIG. 4) to cause the resonant panel to vibrate to generate sound on operation of the exciter, a support frame 20 (see FIG. 4) and mode distribution means 50 (see FIG. 6) to induce non-circularly symmetric distortion of natural modes of oscillation of the resonant panel 10 in response to operation of the exciter 30 in an assembly of the resonant panel 10, the support frame 20 and the exciter 30, absent the mode distribution means 50.

(12) The resonant panel 10 is insertable into a circular opening in the mounting surface. Thus, in this example, the resonant panel 10 is formed to be substantially circular. The resonant panel has a front surface 10a and a rear surface 10b (see FIG. 6) opposite the front surface 10a. The front surface 10a has an outer boundary formed to be substantially circular. The front surface 10a is arranged to face outwardly in the mounting surface when the flat panel loudspeaker 1 is mounted in the mounting surface. In this example, an outer boundary region 12 of the resonant panel has defined therein a plurality of mounting points in the form of mounting holes 14. An inner region 16 of the resonant panel 10 is defined within the outer boundary region 12

(13) FIG. 4 is a further illustration of the flat panel loudspeaker of FIG. 3. As can be seen, the flat panel loudspeaker 1 further comprises a support frame 20 and an exciter 30. The resonant panel 10 is mounted to the support frame 20. In particular, the rear surface 10b of the resonant panel 10, opposite the front surface 10a of the resonant panel 10 is mounted to the support frame 20 around substantially the whole of the outer boundary of the resonant panel 10. In other words, the resonant panel 10 is mounted to the support frame 20 in the outer boundary region 12. The support frame 20 is configured to be mounted in the mounting surface in use, such that the front surface 10a of the resonant panel 10 is arranged to be mounted substantially flush with the mounting surface. The exciter 30 is located substantially at an axial centre of the circular resonant panel 10. The exact configuration of the exciter will be explained further with reference to FIG. 5 below.

(14) As can be seen in FIG. 4, in this example, the inner region 16 of the resonant panel 10 is formed to protrude outwardly from the outer boundary region 12 of the resonant panel 10. Thus, when the flat panel loudspeaker 1 is to be mounted in the mounting surface, a surface finish, such as plaster, can be applied to the mounting surface and extend over the outer boundary region 12 of the resonant panel 10. The difference in relief between the outer boundary region 12 and the inner region 16 is substantially identical to the thickness of the surface finish to be applied. Thus, the inner region 16 may be substantially flush with the mounting surface when the flat panel loudspeaker 1 is installed in the mounting surface. In this example, the surface finish of at least the inner region 16 of the resonant panel 10 may be predetermined to be substantially similar to a surface finish to be finally applied to the mounting surface when the flat panel loudspeaker 1 is mounted in the mounting surface.

(15) FIG. 5 is an illustration of a cross-section through the flat panel loudspeaker of FIGS. 3 and 4. As can be seen, the support frame 20 has the rear surface 10b of the resonant panel 10 fixed thereto around substantially the whole of the outer boundary of the resonant panel 10. In this example, a first part 32 of the exciter 30 is mounted to the support frame 20. A second part 34 of the exciter 30 is coupled to the rear surface 10b of the resonant panel 10. In this example, the second part 34 of the exciter is coupled to the rear surface 10b of the resonant panel 10 via a foot 40. Thus, when the resonant panel 10 is caused by the exciter 30 to vibrate on operation of the exciter 30, the outer boundary region 12 of the resonant panel 10 remains fixed to the support frame 20 and substantially only the inner region of the resonant panel 10 vibrates relative to the support frame 20. In other words, the outer boundary region 12 of the resonant panel 10 is fixed relative to the mounting surface. This ensures that the plaster or other surface covering of the mounting surface is not damaged by operation of the flat panel loudspeaker 1. Although the description above described that the first part 32 of the exciter 30 is mounted to the support frame 20, it will be understood that in some examples, the exciter may be an inertial exciter. That is, the first part 32 of the exciter 30 may have sufficient inertial mass such that operation of the exciter 30 causes movement of the resonant panel 10 even when the first part 32 of the exciter 30 is not mounted to any support frame 20.

(16) It will be understood that the rear surface 10b of the resonant panel 10 can be fixed to the support frame 20 in a variety of ways. For example, as shown in FIG. 3, the plurality of mounting holes 14 can be used to secure the outer boundary region 12 of the resonant panel 10 to the support frame 20. Alternatively or additionally, an adhesive fastening means can be used to fix the outer boundary region 12 of the rear surface 10b of the resonant panel 10 to the support frame 20. In examples, the adhesive may extend substantially around the whole of the outer boundary of the rear surface 10b of the resonant panel 10. In other examples, the adhesive may be provided in a plurality of distributed locations around the outer boundary of the rear surface 10b of the resonant panel 10.

(17) The exciter 30 is located substantially at an axial centre of the resonant panel 10 such that a shortest distance from the second part 34 of the exciter 30 to the outer boundary of the resonant panel 10 is substantially the same anywhere around the second part 34 of the exciter 30 at the foot 40.

(18) In this example, the first part 32 of the exciter 30 comprises an electromagnet which can be activated and de-activated by an input electronic signal. The second part 34 of the exciter 30 comprises a metal component, such as a coil, which can be attracted and/or repelled by the electromagnet of the first part 32 when the electromagnet is activated. Thus, the resonant panel can be caused to vibrate and produce sound in response to operation of the electromagnet of the first part 32 of the exciter 30 by the input electronic signal. The exciter 30 as described may be termed a moving coil exciter. It will be understood that the skilled person is aware of other exciters which can be used in flat panel loudspeakers, including methods for their construction and operation. Other examples of exciters include moving magnet exciters, magneto drivers, and piezo-electric exciters.

(19) The foot 40 provides an interface between the second part 34 of the exciter 30 and the rear surface 10b of the resonant panel 10. In this example, the foot 40 is substantially cylindrical and provides a circular interface between the exciter 30 and the rear surface 10b of the resonant panel 10.

(20) FIG. 6 is an illustration of an underside of the resonant panel of the flat panel loudspeaker of FIGS. 3 to 5. As has been described with reference to previous figures, the rear surface 10b of the resonant panel 10 of the flat panel loudspeaker 1 is mounted to the exciter 30 via a foot 40 in contact with the rear surface 10b of the resonant panel. Owing to the circular geometry of the resonant panel 10 and the central mounting of the foot 40 and the exciter 30 on the resonant panel 10, the resonant panel 10 is provided with mode distribution means in the form of one or more components 50 coupled to the resonant panel 10 to add weight thereto. The one or more components 50 are arranged such that the resonant panel 10 in combination with the one or more components 50 is non-circularly symmetric. In other words, the natural modes of oscillation of the resonant panel in response to operation of the exciter in an assembly of the resonant panel, the support frame and the exciter, absent the mode distribution means are distorted. Thus, it has been found that significant notches and/or peaks in the frequency response of the flat panel loudspeaker, which would otherwise be present due to the circular shape of the resonant panel and central mounting of the exciter, can be lessened in intensity. In some examples, the notches and/or peaks can be substantially eliminated from the frequency response by careful positioning of the mode distribution means. Viewed in another way, audio energy from peaks in the frequency response for the flat panel loudspeaker in the absence of the mode distribution means can be redistributed to heavily damped areas of the frequency response.

(21) In this example, the arrangement of the one or more components 50 is non-rotationally symmetric. In this example, the one or more components 50 are in the form of metal weights. In this example, the metal weights are formed from a non-toxic metal. Suitable non-toxic metals include stainless steel. In this example, the one or more components 50 are mounted on the rear surface 10b of the resonant panel 10.

(22) Although the presently described example uses four metal weights 50 to provide the mode distribution means, it will be understood that the mode distribution means may be provided in any other suitable way. For example, the resonant panel 10 could be provided with one or more depressions defined in the front surface 10a thereof and arranged to be filled-in, for example with plaster, during installation of the flat panel loudspeaker 1 in the mounting surface. The one or more depressions could be arranged such that, when filled in, the natural modes of oscillation of the resonant panel in response to operation of the exciter in an assembly of the resonant panel, the support frame and the exciter, absent the mode distribution means are distorted.

(23) FIG. 7 is a schematic illustration of a resonant panel for use with the flat panel loudspeaker of FIGS. 3 to 5. The resonant panel 10 is formed from a plurality of layers 11a, 11b. The front surface 10a of the resonant panel 10 is provided by a skin layer 11b which is supported on a core layer 11a. In examples, the rear surface 10b of the resonant panel 10 is provided by a surface of the core layer 11a, opposite the skin layer 11b. In other examples (not shown), the rear surface 10b of the resonant panel 10 is provided by a further skin layer. The skin layer 11b is typically formed from fibre-based sheet, such a paper. The core layer 11a is typically formed from a matrix construction. In this example, the resonant panel 10 may be manufactured by pressing and curing an assembly of the core layer 11a, in a pre-preg condition, and the skin layer 11b at sufficient heat and pressure to cause the skin layer 11b to bond to the core layer 11a, resulting in a strong, lightweight, stiff resonant panel 10. The core layer 11a in this example is formed from a composite material.

(24) FIG. 8 is an illustration of an underside of a further example of a resonant panel for the flat panel loudspeaker shown in FIGS. 3 to 5. The resonant panel 10 is substantially as described hereinbefore apart from the hereinafter noted differences. In particular, the mode distribution means is provided by a plurality of components 51, 52, 53, 54, at least one of which has a different size and shape to another of the plurality of components 51, 52, 53, 54. In this example, a first component 51 is positioned substantially opposite a second component 52, though the first component 51 has a depth greater than the second component 52 and the first component 51 is a different size and shape to the second component 52. A third component 53 is positioned on the rear surface 10b of the resonant panel 10, rotationally spaced from the first component 51 and the second component 52. A fourth component 54 is positioned substantially opposite the third component 53. The fourth component 54 has a depth less than the third component 53. The fourth component 54 has a size and shape different from the third component 53. Further, the first, second, third and fourth components 51, 52, 53, 54 are specifically positioned to distort the natural modes of oscillation of the resonant panel 10, substantially as described hereinbefore.

(25) In summary, there is provided a flat panel loudspeaker (1) for mounting in a mounting surface. The flat panel loudspeaker (1) comprises a resonant panel (10) insertable into a circular opening in the mounting surface and having a front surface (10a) having an outer boundary (12) formed to be substantially circular. The front surface (10a) faces outwardly in the mounting surface when the flat panel loudspeaker (1) is mounted in the mounting surface. The resonant panel (10) further comprises a rear surface (10b) opposite the front surface (10a). The flat panel loudspeaker (1) further comprises an exciter (30) located substantially at an axial centre of the circular resonant panel (10) and coupled to the rear surface (10b) of the resonant panel (10) to cause the resonant panel (10) to vibrate, on operation of the exciter (30), to generate sound. The flat panel loudspeaker (1) further comprises a support frame (20) for mounting in the mounting surface and having the rear surface (10b) of the resonant panel (10) fixed thereto around substantially the whole of the outer boundary (12) of the resonant panel (10), such that when mounted in the mounting surface and when the resonant panel (10) is caused by the exciter (30) to vibrate on operation of the exciter (30), the outer boundary (12) of the resonant panel (10) is fixed relative to the mounting surface. The flat panel loudspeaker (1) further comprises mode distribution means (50) configured to induce, in use, non-circularly symmetric distortion of natural modes of oscillation of the resonant panel (10) in response to operation of the exciter (30) in an assembly of the resonant panel (10), the support frame (20) and the exciter (30) absent the mode distribution means (50).

(26) 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 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.

(27) Features, integers, characteristics or groups 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.