LOUDSPEAKER DRIVER

Abstract: A module for attachment to a rigid panel and adapted to apply bending wave energy at audio frequencies to the panel can radiate an audio output, comprising a housing adapted to be secured to the panel, foot means on the housing and adapted to fix the housing securely to the panel, an electro-mechanical transducer in the housing, means supporting the transducer in the housing the transducer being adapted to contact the panel to apply bending wave energy thereto when energised with an electrical audio signal, and audio signal amplifying means in the housing.

Description: TITLE: LOUDSPEAKER DRIVER DESCRIPTION TECHNICAL FIELD The invention relates to loudspeakers and more particularly to loudspeaker drivers. BACKGROUND ART The invention particularly relates to the class of loudspeakers known as bending wave speakers, e.g. of the kind described in O97/09842. It is a specific object of the invention to enhance the utility of display signs such as point of purchase or sale advertising display boards. It is a more general object of the invention to provide an inexpensive and even disposable drive unit, which may be self-contained, for objects such as toys, novelties and merchandising, such as point of sale or point of purchase advertising display boards . DISCLOSURE OF INVENTION According to the invention there is provided a module for attachment to a rigid panel and adapted to apply bending wave energy at audio frequencies to the panel whereby the panel can radiate an audio output, comprising a housing adapted to be secured to the panel, foot means on the housing and adapted to fix the housing securely to the panel e.g. with the aid of adhesive means, an electromechanical transducer in the housing, means supporting the transducer in the housing the transducer being adapted to contact the panel to apply bending wave energy thereto when energised with an electrical audio signal, and audio signal amplifying means in the housing. The foot means may be providing with pressure sensitive adhesive pads to fix the housing to the panel. The foot means may be continuous or may comprise a plurality of spaced feet. The transducer may be piezoelectric or of the magnet and coil variety. The transducer may be inertial, in which case it is compliantly mounted on the housing, or may be grounded on the housing. The transducer means be adhesively fixed to the panel . Thus where the transducer is an electrodynamic device, it may be compliantly mounted, via its magnet to the housing, and may be adhesively fixed, e.g. via a pressure sensitive panel and via its voice coil to the panel . Preferably the mounting of the housing on the panel is compliant. Thus the portion (s) of the housing in the region of the pressure sensitive adhesive means may be resilient. This can be achieved by forming the housing with peripheral inwardly directed resilient flanges to form the foot means . The audio signal amplifying means may be resiliently mounted in the housing. The housing may be perforated to allow audio energy from the panel to pass through the housing. The housing may carry one or more electric dry cell batteries to power the signal amplifying means. These batteries may be substantially symmetrically disposed around the transducer to help equalise force distribution on the transducer suspension. BRIEF DESCRIPTION OF DRAWINGS The invention is diagrammatically illustrated, by way of example, in the accompanying drawings, in which: - Figure 1 is a cross-sectional side elevation of a first embodiment of module for converting a display board to produce an audio output, and Figure 2 is a cross-sectional side elevation of a second embodiment of module. BEST MODES FOR CARRYING OUT THE INVENTION In Figure 1 there is shown a module (12) e.g. for converting a rigid panel in the form of a display board (9) , e.g. a point of purchase advertising display which are normally made of cardboard or the like rigid lightweight material, to provide an audio output to enhance the display. The module (12) comprises a housing (6) in the form of an dished member e.g. of a rigid plastics formed with foot means in the form of a plurality of spaced peripheral inwardly turned resilient flanges (11) carrying pressure sensitive adhesive pads (5) whereby the housing can be firmly affixed to a face of the display board (9) , with the flanges (11) providing a compliant suspension of the housing (6) on the panel (9) . The housing (6) carries an electro-acoustic transducer (1) of the inertial kind comprising a magnet assembly (15) and a voice coil assembly (16) . The transducer is coupled to the housing (6) by a resilient suspension (2) and the voice coil assembly is rigidly fixed to the board (9) by a pressure sensitive adhesive pad (13) . In this way the transducer can apply bending wave energy to the board (9) to cause it to radiate an acoustic output. The resilient or compliant mounting of the housing on the board is to prevent the housing from hindering the propagation of bending wave energy and to help prevent unwanted or unintended vibration of the housing. Thus the housing may also provide damping or mass loading to improve the performance of the panel . The housing (6) carries signal amplifying electronics (18), e.g. a PWA or pulse width amplifier, mounted on a printed circuit board (3) and electric batteries (8) for powering the power amplifier. The printed circuit board (3) is mounted on a compliant mounting (4) in the housing. The module housing (6) also carries audio signal storage means (19) connected to the audio amplifier electronics (18) . The audio signal storage means may, for example, be a tape player or compact disc player or the like. The housing is formed with apertures (10) to allow acoustic energy from the board (9) to pass, substantially unimpeded, through the housing. The printed circuit board (3) on which the electronics (18) is mounted may similarly be apertured for the same purpose. Power supply connectors (7) to the amplifier (13) , can be provided as an alternative to the use of internal batteries. In Figure 2 there is shown a module (12) generally of the kind shown in Figure 1 for application to a display board (9) to convert the display board into a loudspeaker. In this embodiment the module housing (6) is mounted to the display board (9) by a self adhesive means (not shown) provided on a peripheral plinth (17) with a corrugated resilient suspension connected between the plinth (17) and the housing (6) . The batteries (8) in the housing are equally disposed about the transducer (1) to assist in equalising force distribution on the transducer suspension. The module incorporates an external sensor (20) fixed to the board (9) at any convenient location, to allow the assembly to respond to proximity or voice input from a passer-by, e.g. the sensor being in the form of a PIR or passive infra red movement detector, a photocell, or a sensing microphone. The module may be selectively placed on the display board to apply bending wave energy thereto and for beneficial coupling to the available or desired modal distribution and operable frequency range, e.g. as described in our International application WO97/09842. In board electronics, memory and signal processing for storing, receiving, selecting and decoding audio data may be provided in the module. The amplifier to supply audio power to the exciter may for example be from 0.1 to 10W in output, and is preferably of good efficiency to reduce the need for a bulky heatsink, e.g. it may use digital or switching technology if of higher power, say above 1W. The module may include control circuitry e.g. to adjust level or the data channel. The processor may have a data input to receive audio data/programme . A lamp or LED or form or data display, e.g. visual or complementary readout of the audio data may be included to show operational states or to convey additional information, and this may be directed through an aperture in the display board or panel or by the choice of a part or wholly translucent or transparent display panel. The display board or panel used with module may be advantageously be of distributed mode principle/design to further maximise sound quality e.g. as described in WO97/09842. The module may be designed to have adhesive surfaces exposed by peel-off covers for both the module and the exciter coupling to the panel for rapid, non skilled assembly of the complete speaker/sound reproducing system. The module may be designed to be dust/splash proof or waterproof with a continuous adhesive sealing around its perimeter. INDUSTRIAL APPLICABILITY The invention thus provides a convenient and self contained module for increasing the functionality of display boards and the like, as well as providing a self contained speaker driver for other rigid panels in toys, novelties, and merchandising generally.

Claims: CLAIMS 1. A module for attachment to a rigid panel and adapted to apply bending wave energy at audio frequencies to the panel whereby the panel can radiate an audio output, comprising a housing adapted to be secured to the panel, foot means on the housing and adapted to fix the housing securely to the panel , an electro-mechanical transducer in the housing, means supporting the transducer in the housing the transducer being adapted to contact the panel to apply bending wave energy thereto when energised with an electrical audio signal, and audio signal amplifying means in the housing. 2. A module according to claim 1, wherein the foot means is providing with pressure sensitive adhesive pads to fix the housing to the panel. 3. A module according to claim 1 or claim 2 , wherein the foot means comprises a plurality of spaced feet . 4. A module according to any one of claims 1 to 3 , wherein the transducer is of the magnet and coil variety. 5. A module according to claim 4, wherein the transducer is inertial, and is compliantly mounted on the housing. 6. A module according to any preceding claim, wherein the transducer means is adhesively fixed to the panel . 7. A module according to any preceding claim, wherein the mounting of the housing on the panel is compliant. 8. A module according to claim 7, when dependent on claim 2, wherein the portion (s) of the housing in the region of the pressure sensitive adhesive means are resilient. 9. A module according to claim 8, wherein the housing is formed with peripheral inwardly directed resilient flanges to form the foot means . 10. A module according to any preceding claim, wherein the 5 audio signal amplifying means is resiliently mounted in the housing. 11. A module according to any preceding claim, wherein the housing is perforated to allow audio energy from the panel to pass through the housing. 10 12. A module according to any preceding claim, wherein the housing carries at least one electric dry cell battery to power the signal amplifying means. 13. A module according to claim 12, comprising a plurality of batteries which are substantially symmetrically disposed 15 around the transducer to help equalise force distribution on the transducer suspension. 14. A module according to any preceding claim, comprising audio signal storage means connected to the audio signal amplifying means. 20 15. A module according to any preceding claim, comprising motion or proximity sensing means adapted to activate the audio signal amplifying means. 16. A bending wave loudspeaker comprising a rigid panel and a module as claimed in any proceeding claim attached to 25 the panel to apply bending wave energy thereto. 17. A signboard comprising a bending wave loudspeaker according to claim 16.

Inventors: COLLOMS MARTIN, MACFARLANE IAN DAVID, COLLOMS, MARTIN, MACFARLANE, IAN, DAVID
Applicants: COLLOMS MARTIN, MACFARLANE IAN DAVID, NEW TRANSDUCERS LTD, COLLOMS, MARTIN, MACFARLANE, IAN, DAVID, NEW TRANSDUCERS LIMITED
Application year: 2001
Main classification: H04R7
IPC codes: H04R1, H04R3, H04R7, H04R9