LOUDSPEAKERS

Abstract: A loudspeaker comprising a bending-wave panel, an enclosure in which the bending-wave panel is mounted to enclose one face of the panel, a compliant suspension between the panel and the enclosure by which the panel is supported in the enclosure, a vibration exciter attached to the panel to apply bending-wave energy thereto, and an acoustic absorber in the enclosure to reduce standing waves in the enclosure, characterised in that the compliant suspension and the acoustic absorber are integral.

Description: TITLE: LOUDSPEAKERS DESCRIPTION TECHNICAL FIELD The invention relates to loudspeakers and more particularly to bending-wave panel -form loudspeakers, e.g. of the kind described m International patent application WO97/09842. Such loudspeakers are known as 'distributed mode' or "DM" loudspeakers or simply as DML. BACKGROUND ART Bending-wave panels emit acoustic radiation from both sides i.e. are bi-polar and to allow easier positioning of the loudspeaker in a room, e.g. against a wall, the rear radiation from the panel can be blocked by mounting the panel in a sealed box or enclosure with flexible suspension or surround material around the panel perimeter. This prevents any destructive interference from reflecting surfaces to the rear of the panel . The panel suspension or surround material may be a strip of flexible foam rubber or plastics with adhesive tape on both sides so that it can be fixed to both the panel and the box. However m such an arrangement standing waves may be set up m the box or enclosure which can adversely affect the frequency response of the panel . These standing waves can be damped by filling the box or enclosure with an acoustic absorber, e.g. of soft foam which can contact either the bending-wave panel or the back of the box or enclosure. Flexible polyester or polyether foams are suitable for this application. A known set-up for a bending-wave panel of the DML kind in an enclosure uses a strip of flexible foam as a suspension or surround and uses a separate acoustic absorber in the enclosure. DISCLOSURE OF INVENTION According to the present invention, there is provided a loudspeaker comprising a bending-wave panel m an enclosure, wherein the panel surround suspension system and the acoustic absorber are integrated. A soft foam used as the acoustic absorber may thus be compressed to the required thickness around the perimeter of the panel to form the flexible surround whereas the central region of the foam remains uncompressed allowing it to form an effective acoustic absorber. BRIEF DESCRIPTION OF DRAWINGS The invention is diagrammatically illustrated, by way of example, in the accompanying drawings, m which: - Figure 1 is a cross sectional side view of a prior-art bending-wave loudspeaker, and Figure 2 is a cross sectional side view of a bending- wave loudspeaker according to the invention. BEST MODE FOR CARRYING OUT THE INVENTION In Figure 1, there is shown a prior-art bending-wave panel loudspeaker 1, comprising a bending-wave loudspeaker 1, comprising a bending-wave panel 2 mounted in an enclosure or box 3 by means of a surround or suspension 4 e.g. of a resilient foamed rubber or plastics. Thus the outer face 5 of the panel 2 can radiate sound while acoustic radiation from the face 6 of the panel m the enclosure 3 is contained m the enclosure and is absorbed by acoustic absorber foam 7. A vibration exciter 8 is fixed to the panel 2 to launch bending wave energy into the panel to cause it to resonate to produce an acoustic output, e.g. as taught m WO97/09842. In Figure 2 there is shown a loudspeaker generally similar to that of Figure 1, but modified according to the principles of the present invention. Thus the surround/suspension 4 is integral with the acoustic absorber 7. A manufacturing process for the unitary absorber/suspension 4,7 may be as follows: 1. Apply a layer of adhesive (e.g. epoxy, acrylic or cyanoacrylate) around the perimeter of the panel. 2. Cut the piece of uncompressed foam to the required 3. Position the foam m one half of the press tool and the panel m the opposite naif. 4. Apply heat and pressure suitable for the foam material to compress and the surround adhesive to cure and form an effective bond between panel and surround material. 5. Remove part from press tool. 6. The panel surround (including the panel and acoustic absorber) can then, for example, be adhesively bonded or mechanically clamped to the back box to form a complete unit. Compressing the foam around the perimeter changes it from an open-cell foam suitable as an absorber into a compressed version where the cells are squashed to an extent that the perimeter has very little acoustic power transmitted through it. This ensures isolation of the rear radiation from the front. INDUSTRIAL APPLICABILITY The present invention thus provides a new design whereby the foam surround and acoustic absorber are incorporated into a single item which can be easily formed and bonded to the panel m a simple press tool. This new design simplifies the manufacturing process for a DML or the like used m a closed back design.

Claims: CLAIMS 1. A loudspeaker comprising a bending-wave panel, an enclosure in which the bending-wave panel is mounted to enclose one face of the panel, a compliant suspension between the panel and the enclosure by which the panel is supported in the enclosure, a vibration exciter attached to the panel to apply bending-wave energy thereto, and an acoustic absorber in the enclosure to reduce standing waves in the enclosure, characterised in that the compliant suspension and the acoustic absorber are integral. 2. A loudspeaker according to claim 1, characterised in that the integral acoustic absorber and compliant suspension are of a soft foam material . 3. A loudspeaker according to claim 2, characterised in that the soft foam material is compressed in a region defining the compliant suspension compared to the region defining the acoustic absorber.

Inventors: BANK GRAHAM, FORDHAM JULIAN, BANK, GRAHAM, FORDHAM, JULIAN
Applicants: BANK GRAHAM, FORDHAM JULIAN, NEW TRANSDUCERS LTD, BANK, GRAHAM, FORDHAM, JULIAN, NEW TRANSDUCERS LIMITED
Application year: 2000
Main classification: H04R7
IPC codes: H04R1, H04R7, H04R23, H04R31