U.S. patent application number 09/985781 was filed with the patent office on 2002-03-14 for loudspeakers.
This patent application is currently assigned to NEW TRANSDUCERS LIMITED. Invention is credited to Bank, Graham, Fordham, Julian.
Application Number | 20020029925 09/985781 |
Document ID | / |
Family ID | 10853417 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020029925 |
Kind Code |
A1 |
Bank, Graham ; et
al. |
March 14, 2002 |
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, wherein the compliant suspension and the acoustic
absorber are integral. A method of making such a loudspeaker is
also disclosed.
Inventors: |
Bank, Graham; (Suffolk,
GB) ; Fordham, Julian; (Cambridgeshire, GB) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
NEW TRANSDUCERS LIMITED
|
Family ID: |
10853417 |
Appl. No.: |
09/985781 |
Filed: |
November 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09985781 |
Nov 6, 2001 |
|
|
|
PCT/GB00/01666 |
May 11, 2000 |
|
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Current U.S.
Class: |
181/148 ;
181/151; 181/171 |
Current CPC
Class: |
H04R 1/22 20130101; H04R
7/20 20130101; H04R 31/003 20130101; H04R 7/045 20130101 |
Class at
Publication: |
181/148 ;
181/151; 181/171 |
International
Class: |
H05K 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 14, 1999 |
GB |
9911156.9 |
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, wherein the compliant suspension and the acoustic
absorber are integral.
2. A loudspeaker according to claim 1, wherein the integral
acoustic absorber and compliant suspension are of a soft foam
material.
3. A loudspeaker according to claim 2, wherein the soft foam
material is compressed in the region defining the compliant
suspension as compared to the region defining the acoustic
absorber.
4. A loudspeaker according to claim 3, wherein the soft foam
material in the region defining the acoustic absorber is
substantially uncompressed.
5. A loudspeaker according to claim 1, wherein the density of the
compliant suspension is greater than the density of the acoustic
absorber.
6. A method of making a loudspeaker sub-assembly having a bending
wave panel, a flexible surround suspension for the panel and an
acoustic absorber for filling the space between the panel and an
enclosure to which the panel will be mounted via the suspension,
comprising the steps of: applying a layer of adhesive to one face
of the panel along the perimeter thereof; placing a piece of
uncompressed foam on said one face of the panel so as to cover said
one face and contact the adhesive; applying heat and pressure to
the panel and the foam along the perimeter thereof to compress the
foam and cure the adhesive so as to form a surround suspension that
is bonded to the panel and is denser than the acoustic absorber
foam bounded by the surround suspension; and removing the heat and
pressure from the panel and the foam.
7. A method of making a loudspeaker having a bending wave panel
mounted to an enclosure, a vibration exciter fixed to the panel for
launching bending wave energy into the panel, a flexible surround
suspension for the panel, and an acoustic absorber for filling the
space between the panel and the enclosure, comprising the steps of:
applying a layer of adhesive to one face of the panel along the
perimeter thereof; placing a piece of uncompressed foam on said one
face of the panel so as to cover said one face and contact the
adhesive; applying heat and pressure to the panel and the foam
along the perimeter thereof to compress the foam and cure the
adhesive so as to form a surround suspension that is bonded to the
panel and is denser than the acoustic absorber foam bounded by the
surround suspension; removing the heat and pressure from the panel
and the foam; and assembling the panel, with integral surround
suspension and acoustic absorber, to the enclosure.
8. A method according to claim 7, wherein the step of assembling
the panel to the enclosure comprises adhesively bonding the
surround suspension to the enclosure.
9. A method according to claim 7, wherein the step of assembling
the panel to the enclosure comprises mechanically clamping the
panel to the enclosure with the surround suspension between the
panel and the enclosure.
Description
[0001] This application is a continuation of International patent
application No. PCT/GB00/01666, filed May 11, 2000, and published
in English.
TECHNICAL FIELD
[0002] The invention relates to loudspeakers and, more
particularly, to bending wave panel-form loudspeakers, e.g. of the
kind described in International patent application WO97/09842 and
U.S. counterpart application Ser. No. 08/707,012, filed Sep. 3,
1996. Such loudspeakers are known as "distributed mode" or "DM"
loudspeakers, or simply as DML.
BACKGROUND ART
[0003] 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.
[0004] However, in such an arrangement standing waves may be set up
in 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 setup 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.
SUMMARY OF THE INVENTION
[0005] According to the present invention, there is provided a
loudspeaker comprising a bending wave panel in 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. In other words, the density of the
foam in the perimeter region is higher than that in the central
region.
[0006] According to another aspect of the invention, there is
provided a method of making a loudspeaker sub-assembly having a
bending wave panel, a flexible surround suspension for the panel
and an acoustic absorber for filling the space between the panel
and an enclosure to which the panel will be mounted via the
suspension. The method comprises the steps of applying a layer of
adhesive to one face of the panel along the perimeter thereof;
placing a piece of uncompressed foam on the one face of the panel
so as to cover the one face and contact the adhesive; applying heat
and pressure to the panel and the foam along the perimeter thereof
to compress the foam and cure the adhesive so as to form a surround
suspension that is bonded to the panel and is denser than the
acoustic absorber foam bounded by the surround suspension; and
removing the heat and pressure from the panel and the foam.
[0007] According to yet another aspect of the invention, there is
provided a method of making a loudspeaker having a sub-assembly
made as above, comprising the further step of assembling the panel,
with integral surround suspension and acoustic absorber, to the
enclosure.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The best mode of carrying out the invention is described in
detail below and diagrammatically illustrated in the accompanying
drawing, in which:
[0009] FIG. 1 is a cross-sectional side view of a prior art bending
wave loudspeaker, and
[0010] FIG. 2 is a cross-sectional side view of a bending-wave
loudspeaker according to the invention.
DETAILED DESCRIPTION
[0011] In FIG. 1 there is shown a prior art bending wave panel
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 in the enclosure 3 is contained in 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 in WO97/09842 and U.S. Ser. No. 08/707,012.
[0012] In FIG. 2 there is shown a loudspeaker generally similar to
that of FIG. 1, but modified according to the principles of the
present invention. Like but primed reference numerals are used in
FIG. 2. Thus the surround/suspension 4 is integral with the
acoustic absorber 7.
[0013] A manufacturing process for the unitary absorber/suspension
4,7 may be as follows:
[0014] 1. Apply a layer of adhesive (e.g. epoxy, acrylic or
cyanoacrylate) around the perimeter of the panel.
[0015] 2. Cut the piece of uncompressed foam to the required
size.
[0016] 3. Position the foam in one half of the press tool and the
panel in the opposite half.
[0017] 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.
[0018] 5. Remove the part from the press tool.
[0019] 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.
[0020] 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.
[0021] 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 in a simple
press tool. This new design simplifies the manufacturing process
for a DML loudspeaker or the like used in a closed back design.
* * * * *