GB2544548A

GB2544548A - Flat panel loudspeakers

Info

Publication number: GB2544548A
Application number: GB1520516.4A
Authority: GB
Inventors: Mikalauskas Egidijus
Original assignee: Amina Technologies Ltd
Current assignee: Amina Technologies Ltd
Priority date: 2015-11-20
Filing date: 2015-11-20
Publication date: 2017-05-24
Anticipated expiration: 2035-11-20
Also published as: GB201520516D0; GB2544548B

Abstract

The flat panel loudspeaker comprises a flat panel 230, an exciter 202 coupled to the flat panel and configured to in use generate sound from the flat panel speaker by vibrating the flat panel. A support frame 210 supports both the flat panel and the exciter. The support frame comprises a main wall portion 208 and one or more opposing lip portions 206 rigidly coupled to the main wall portion by a web portion 207. The lip portions support the flat panel 230. One or more vibration damping members 220 are in a channel formed between retained between the lip portions and the main wall portion of the support frame, and they damp vibrations in the support frame 210 caused by vibrations of the flat panel.

Description

FLAT PANEL LOUDSPEAKERS

[0001] This invention relates to flat panel loudspeakers, in particular distributed mode loudspeakers, including a damping insert.

BACKGROUND

[0002] Flat panel loudspeakers provide a number of advantages when compared to dynamic driver design that use a cone-shaped diaphragm. One type of flat panel loudspeaker is a distributed mode loudspeaker (DML). A DML is different to conventional loudspeakers as it uses the pistonic movement of an exciter, or a moving coil drive unit, to excite a flat panel at its resonant modes, causing the sound to be amplified in a manner similar to the soundboard of a musical instrument such as a violin or a piano. The construction of a DML means it has a thin profile, making it suitable for mounting to walls and embedding in wall cavities such that the loudspeakers may be ‘invisible’ in use.

[0003] In designing loudspeakers, there often exists a difficultly in reliably producing spectrally complex sounds through a loudspeaker in a clear manner. When designing and manufacturing any loudspeaker system, acoustic considerations must be taken into account. These considerations may include the materials the loudspeaker is comprised from as well as external factors such as the environment the loudspeaker is placed in, i.e. the material composition and arrangement of the surroundings.

[0004] The performance of a flat panel loudspeaker is sensitive to the position of the exciter, and so the frequency response and the output sound quality and clarity of the loudspeaker depends on the quality of the design and build of the loudspeaker. Thus a significant number of design considerations need to be taken into account when designing and manufacturing flat panel loudspeakers to attain a desired audio response and acoustic performance.

[0005] It is in this context that the present invention is devised.

[0006] BRIEF SUMMARY OF THE DISCLOSURES accordance with the present inventions there is provided a flat panel loudspeaker comprising: a flat panel; an exciter coupled to the flat panel and configured to in use generate sound from the flat panel speaker by vibrating the flat panel; and a support frame supporting the flat panel and supporting the exciter; the support frame comprising a main wall portion and one or more opposing lip portions each rigidly coupled to the main wall portion by a web portion, the lip portion supporting the flat panel; and one or more damping members retained between the lip portions and the main wall portion of the support frame, the damping members being for damping vibrations in the support frame caused by vibrations of the flat panel.

[0007] It has been found that the provision of one or more damping members retained between the lip portions and the main wall portion of the support frame in a flat panel loudspeaker, particularly a DML, can result in improved sound quality and clarity particularly when the flat panel loudspeaker is playing spectrally complex music, particularly at high volumes.

[0008] It has been found that there are two reasons for this improvement. Firstly, the provision of the damping members at this location has been found to reduce the ringing and resonance that would otherwise occur in the support frame by energy transfer from the flat panel to the support frame during operation of the exciter. The presence of resonance in the mounting panel causes relative movement between the exciter core and the moving coil, which causes unwanted distortion and a reduction in quality of the output sound.

[0009] Secondly, the provision of the damping members at this location has been found to reduce the energy transferred from the flat panel to the support frame supporting the resonant panel, and on to the surrounding wall structure. During playback of spectrally complex sounds, excess energy absorption by the surrounding structure may result in distortion of the sound owing to resonance between the of the wall (or ceiling) structure itself.

[0010] In embodiments a flat panel loudspeaker is provided, wherein the main wall portion and the opposing one or more lip portions coupled by respective webs together form a c-shaped channel. This channel enables one or more damping members to be supported.

[0011] In embodiments a flat panel loudspeaker is provided, wherein the portions of the support frame are integrally formed. That is, the main wall, web and lip portions of the support frame are formed as a single unit from a single piece of material, giving a rigid structure.

[0012] In embodiments a flat panel loudspeaker is provided, wherein the one or more damping members is comprises plural compressible inserts. The inserts may be of a range and variety of sizes used to absorb energy and to improve the clarity of the reproduced sound. The compressible inserts, received in the channel or between the lip and main wall portions of the support frame, may be held under compression, or light compression, to facilitate energy absorption and dissipation to reduce energy transfer and unwanted resonance.

[0013] In embodiments a flat panel loudspeaker is provided, wherein a single damping member is provided, formed as a single ring. The single ring may encompass the whole flat panel and be used to absorb energy and to improve the clarity of the reproduced sound.

[0014] In embodiments a flat panel loudspeaker is provided, wherein the one or more damping members is formed from rubber. As a compressible material rubber is suitable, however out materials may be used.

[0015] In embodiments a flat panel loudspeaker is provided, wherein the one or more damping members is a substantially cylindrical rod.

[0016] In embodiments a flat panel loudspeaker is provided, wherein the one or more damping members is sized so as to be held between the lip portions and the main wall portions of the support frame in a compressed configuration.

[0017] In embodiments a flat panel loudspeaker is provided, wherein the flat panel loudspeaker is a distributed mode loudspeaker.

[0018] In embodiments a flat panel loudspeaker is provided, wherein the flat panel speaker is mounted in and supported by a mounting box.

[0019] In embodiments a flat panel loudspeaker is provided, wherein the flat panel speaker is fitted into a wall, optionally a stud wall. A stud wall may allow for easier installation of the flat panel loudspeaker.

[0020] In embodiments a flat panel loudspeaker is provided, wherein the support frame is formed to have stiffening portions that improve the rigidity of the support frame, such one or more ribs or fins. The stiffening member provides rigidity to the flat panel loud speaker [0021] In embodiments a flat panel loudspeaker is provided, wherein the flat panel comprises a mesh pattern. The mesh or honeycomb pattern give the flat panel a lightweight structure and allows air displacement in to and out of the enclosed cavity region of the back of the flat panel loudspeaker, which facilitates free movement of the flat panel during usage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Certain embodiments of the invention are further described hereinafter, by way of example only, and with reference to the accompanying drawings, in which: [0023] Figure 1 illustrates a flat panel loudspeaker in accordance with one embodiment incorporating an exciter coupled to a resonant member thereof to be vibrationally excited in use; [0024] Figure 2A illustrates a view of a flat panel loudspeaker of one embodiment from the back; [0025] Figure 2B illustrates a view a the flat panel loud speaker of Figure 2A from the top shown cut away along line A-A; [0026] Figure 3A illustrates measured sound pressure or energy against frequency in the support frame at the fixing point of the flat panel for 1 W and 32 W of power; [0027] Figure 3B illustrates energy against frequency in the surrounding support structure (i.e. wall) of the flat panel for 1 W and 32 W of applied power; [0028] Figure 4A illustrates energy against frequency in the support frame at the fixing point of the flat panel at 1 W of applied power for no rubber damping and with rubber damping; [0029] Figure 4B illustrates energy against frequency in the support frame at the fixing point of the flat panel at 32 W of applied power for no rubber damping and with rubber damping; [0030] Figure 5A illustrates energy against frequency in the surrounding support structure at 1 W of applied power for no rubber damping and with rubber damping] and [0031] Figure 5B illustrates energy against frequency in the surrounding support structure at 32 W of applied power for no rubber damping and with rubber damping.

DETAILED DESCRIPTION

[0032] As shown in Figure 1, in an embodiment of the present invention, the flat panel loudspeaker is provided as a distributed mode loudspeaker 100. The distributed mode vibrating panel loudspeaker 100 has a flat panel 104, mounted to a support frame 106 at fixing positions so as to be vibrationally excitable by a carefully positioned electro-dynamic exciter 102 also mounted to the support frame 106 (or alternatively inertially mounted). The flat panel 104 has a front surface and a back surface. The front surface of the panel 104 faces outwards opposite the support frame 106. A cylindrical ‘foot’ (not shown) of the exciter 102 is coupled to the back surface of the flat panel 104, for example by bonding, to ‘excite’ the panel by pistonic movement to cause the panel 104 to resonate in use. The flat panel 104 is typically formed from to have a homogeneous structure, such as a lightweight honeycomb sandwich, across the whole flat panel 104. The exciter 102 is driven by an electrical signal received at terminals thereof from, for example, an audio amplifier unit (not shown), via conductive cables 108. When caused to vibrate by exciter 108, the flat panel 104 acts to amplify these vibrations in a similar manner to a soundboard of a violin or piano such that the distributed mode loudspeaker 100 produces sound from the electrical signal. To embed the flat panel loudspeaker 100 in a wall, the loudspeaker 100 is inserted into a mounting box (not shown) which is placed in a wall such as a stud wall (either during construction of the wall or by retro-fitting through a hole formed in the wall) such that the flat panel 104 is flush with the surface of the wall and surrounded by the plasterboard. Jointing tape may be used to cover any gaps between the flat panel 104 and surrounding wall and the wall surface may be finished by skimming over the top, including over the top of the flat panel 104, such that the loudspeaker 100 is ‘invisible’ in use and the flat panel which creates the sound actually forms part of the wall surface.

[0033] Reference will now be made to Figure 2A which is an illustration of a rear view of a flat panel loudspeaker 200 similar to that shown in Figure 1 in accordance with an embodiment of the present disclosure, and Figure 2B, which shows a view of the loudspeaker 200 from the top, cutaway through the dotted line marked A-A in Figure 2A. In particular the flat panel loudspeaker 200 for the production of sound comprises an exciter 202, an electrical conductor 204 and a support frame 210. The exciter 202 and the electrical conductor 204 are affixed to the support frame 210. The support frame 210 has fixing points 212 at which the flat panel 230 is coupled to the support frame 210. The support frame 210 also comprises a plurality of open holes 214 which are arranged in a honeycomb structure in order to provide a lightweight structure that allows the free movement of air to the back of the flat panel 230, to allow the flat panel 230 to vibrate unimpeded. The support frame 210 is formed from a single piece of material to have stiffening ribs extending orthogonally away from the major extent of the frame 210, so as to provide an overall rigid structure, which aids the quality of acoustic reproduction.

[0034] The exciter 202 is driven by an electrical signal received at terminals thereof from, for example, an audio amplifier unit (not shown), via the electrical conductor 204. When caused to vibrate by exciter 202, the flat panel 230acts to amplify these vibrations in a similar manner to a soundboard of a violin or piano such that the distributed mode loudspeaker 200 produces sound from the electrical signal. The exciter 202 comprises a moving coil drive unit further comprising a magnet assembly and coil assembly which is in turn coupled to the flat panel 230. Preferably the speaker 200 is of the DML type, however it will be appreciated that the present invention may be suitable for any type of vibrating flat panel loudspeaker.

[0035] Referring now in particular to Figure 2B, as previously described, the exciter 202 and the electrical conductor 204 can be seen affixed to the support frame 210.

[0036] The support frame 210 comprises a main wall portion 208, and plural lip portions 206 extending along each of the four edges at the periphery of the support frame, wherein each lip portion 206 is joined to the main wall portion 208 by a respective web portion 207. The main wall portion 208, web portions 207 and respective lip portions 206 are integrally formed. In alternative embodiments, the support frame 210 may be formed to have a single lip portion extending unbroken around its periphery, or to have plural lip portions provided at intervals along the edges. As can be seen from Figure 2B, the lip portions 206 of the support frame 210 support the flat panel 230 in use by the flat panel 230 being mounted to the support frame 210 such that the rear surface of the flat panel 230 is held against and rests on the lip portions. While being held against the lip portions 206, the flat panel is caused to move and vibrate by the exciter 202.

[0037] As shown in Figure 2B, the lip portions 206, the web portions 207 and the main wall portion 206 each together define a channel or cavity into which a damping member 220 is inserted. Plural discrete damping members 220 may be provided at intervals around the periphery of the support from 210, or the damping member 220 may be formed as a single ring (which is dimensioned and shaped appropriately) to extend around the periphery of the support frame 210 in the channels defined by the or each lip. The damping member (or members) 220 is formed of a resilient and compressible material, such as rubber or silicone rubber.

[0038] The damping member 220 acts to in use absorb energy or excess energy generated whilst reproducing sound which would otherwise be transferred to the support frame 210 and contribute to relative motion between the exciter components and distortion of sound, and to the surrounding support structure of the wall or ceiling into which the flat panel speaker may be embedded (or mounted), vibration of which would cause a deterioration of sound quality.

[0039] It will be appreciated that the damping member may comprise of many different shapes and sizes of other compressible material, indeed it will also be appreciated that more than one damping member may be used.

[0040] It will also appreciated that the flat panel loudspeaker does not have to be installed inside a wall, indeed it may be installed in a ceiling, floor, or any other suitable structure.

[0041] A distributed mode loudspeaker 200 incorporating a damping member arranged as shown in Figures 2A and 2B has been constructed and embedded in a stud wall to be ‘invisible’ therein, such that the flat panel 230 forms a part of the wall surface, and to illustrate the effect of the invention, tests were performed to measure the sound pressure -or energy - created in use on the support frame at one of the fixing points, and at a point on the wall 1 metre away from the fixing points. To improve the perceived sound quality, the provision of the damping member should reduce the measured sound pressure at both these locations. The results of these tests will now be described with reference to Figures 3, 4 and 5.

[0042] Figures 3A and 3B are illustrations of graphs showing the frequency response for a flat panel loudspeaker like in 200 but without having any damping members provided as shown in Figure 2 in accordance with the embodiments of the invention. Figure 3A shows the frequency response of the measured sound pressure in the support frame 210 at the fixing point for both 1W (shown by line 304) and 32W (shown by line 302) of applied power. Figure 3B is an illustration of a graph showing the frequency response for the flat panel loudspeaker at a point in the surrounding support structure (i.e. wall) 1 metre away from the fixing point for both 1W (shown by line 308) and 32W (shown by line 306) of applied power.

[0043] To illustrate the effect of the provision of the damping members 220 as in the embodiment of Figure 2, Figure 4A is an illustration of a graph showing the frequency response for the flat panel loud speaker in the support frame 210 at the fixing point for 1W of applied power with no rubber damping (shown by line 402) and with rubber damping inserted into the channel around the periphery of the support frame 210 (shown by line 404). It can be seen from the graphs that at lower applied power the damping member generally reduces the energy transfer to the support frame 210 across the frequency spectrum particularly so above around 100 Hz and in the high frequency range of 7kHz -20kHz.

[0044] Figure 4B is an illustration of a graph showing the frequency response for the flat panel loud speaker in the support frame 210 at the fixing point for 32W of applied power with no rubber damping (shown by line 406) and with rubber damping (shown by line 408). It can be seen from the graph that at higher applied power the damping member generally reduces the energy transfer to the support frame 210 for the 100Hz - 20kHz frequency spectrum, particularly so at frequencies from 30-1000Hz and in the high frequency range of 7kHz - 20kHz.

[0045] Thus it can be seen from Figures 4A and 4B that the damping member is particularly effective in reducing the energy transfer to the support frame 210, hence improving the clarity and perceived quality of the produced sound.

[0046] [0047] Figure 5A is an illustration of a graph showing the frequency response for the flat panel loud speaker in the surrounding support structure (i.e. wall) at a location 1 metre away from the fixing point for 1W of applied power with no rubber damping (shown by line 502) and with rubber damping (shown by line 504). It can be seen from the graph that at lower applied power the damping member generally reduces the energy transfer to the surrounding structure across the frequency spectrum particularly at 50Hz - 500Hz and 4kHz-20.

[0048] Figure 5B is an illustration of a graph showing the frequency response for the flat panel loud speaker in the surrounding support structure at a location 1 metre away from the fixing point for 32W of applied power with no rubber damping (shown by line 506) and with rubber damping (shown by line 508). It can be seen from the graph that at higher applied power the damping member generally reduces the energy transfer to the surrounding structure across the frequency spectrum, particularly so in the high frequency range of 4kHz - 20kHz.

[0049] Thus it can be seen from Figures 5A and 5B that the damping member is particularly effective in reducing the energy transfer to the surrounding support structure (i.e. wall), hence improving the clarity and perceived quality of the produced sound.

[0050] 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 moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0051] Features, integers, characteristics, compounds, chemical moieties 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.

[0052] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

1. A flat panel loudspeaker comprising: a flat panel; an exciter coupled to the flat panel and configured to in use generate sound from the flat panel speaker by vibrating the flat panel; and a support frame supporting the flat panel and supporting the exciter; the support frame comprising a main wall portion and one or more opposing lip portions each rigidly coupled to the main wall portion by a web portion, the lip portion supporting the flat panel; and one or more damping members retained between the lip portions and the main wall portion of the support frame, the damping members being for damping vibrations in the support frame caused by vibrations of the flat panel.

2. A flat panel loudspeaker as claimed in any preceding claim, wherein the main wall portion and the opposing one or more lip portions coupled by respective webs together form a c-shaped channel.

3. A flat panel loudspeaker as claimed in any preceding claim, wherein the portions of the support frame are integrally formed.

4. A flat panel loudspeaker as claimed in any preceding claim, wherein the one or more damping members is comprises plural compressible inserts.

5. A flat panel loudspeaker as claimed in any preceding claim, wherein a single damping member is provided formed as a single ring.

6. A flat panel loudspeaker as claimed in any preceding claim, wherein the one or more damping members is formed from rubber.

7. A flat panel loudspeaker as claimed in any preceding claim, wherein the one or more damping members is a substantially cylindrical rod.

8. A flat panel loudspeaker as claimed in any preceding claim, wherein the one or more damping members is sized so as to be held between the lip portions and the main wall portions of the support frame in a compressed configuration.

9. A flat panel loudspeaker as claimed in any preceding claim, wherein the flat panel loudspeaker is a distributed mode loudspeaker.

10. A flat panel loudspeaker as claimed in any preceding claim, wherein the flat panel speaker is mounted in and supported by a mounting box.

11. A flat panel loudspeaker as claimed in any preceding claim, wherein the flat panel speaker is fitted into a wall, optionally a stud wall.

12. A flat panel loudspeaker as claimed in any preceding claim, wherein the support frame is formed to have stiffening portions that improve the rigidity of the support frame.

13. A flat panel loudspeaker as claimed in any preceding claim, wherein the flat panel comprises a mesh pattern.

14. A flat panel loudspeaker configured as hereinbefore described, with reference to Figures 2A and 2B.