U.S. patent number 6,700,987 [Application Number 09/934,225] was granted by the patent office on 2004-03-02 for loudspeaker.
This patent grant is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Mitsukazu Kuze, Shuji Saiki, Hiroyuki Takewa.
United States Patent |
6,700,987 |
Kuze , et al. |
March 2, 2004 |
Loudspeaker
Abstract
A loudspeaker includes: a frame; a vibrating section including a
diaphragm having an internal periphery and an external periphery, a
voice coil attached to the internal periphery of the diaphragm, a
spider which connects the voice coil to the frame, and a dust cap
attached to the internal periphery of the diaphragm; and a surround
which connects the external periphery of the diaphragm to the
frame, wherein the ratio between the weight of the vibrating
section and the weight of the surround is 0.9:1 to 1.5:1.
Inventors: |
Kuze; Mitsukazu (Osaka,
JP), Saiki; Shuji (Nara, JP), Takewa;
Hiroyuki (Osaka, JP) |
Assignee: |
Matsushita Electric Industrial Co.,
Ltd. (Osaka, JP)
|
Family
ID: |
18743914 |
Appl.
No.: |
09/934,225 |
Filed: |
August 21, 2001 |
Foreign Application Priority Data
|
|
|
|
|
Aug 25, 2000 [JP] |
|
|
2000-255062 |
|
Current U.S.
Class: |
381/398; 181/172;
381/396 |
Current CPC
Class: |
H04R
7/12 (20130101); H04R 7/20 (20130101); H04R
2307/201 (20130101) |
Current International
Class: |
H04R
7/12 (20060101); H04R 7/20 (20060101); H04R
7/00 (20060101); H04R 025/00 () |
Field of
Search: |
;381/396,398,400,403-404,420,423,432,426
;181/167,169,171,172,173,174 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Kuntz; Curtis
Assistant Examiner: Dabney; P.
Attorney, Agent or Firm: RatnerPrestia
Claims
What is claimed is:
1. A loudspeaker, comprising: a frame; a vibrating section
including a diaphragm having an internal periphery and an external
periphery, a voice coil attached to the internal periphery of the
diaphragm, a spider which connects the voice coil to the frame, and
a dust cap attached to the internal periphery of the diaphragm; and
a surround which connects the external periphery of the diaphragm
to the frame, wherein the ratio between the weight of the vibrating
section and the weight of the surround is 0.9:1 to 1.5:1.
2. A loudspeaker according to claim 1, wherein the ratio between
the diameter of the diaphragm and the height of the diaphragm is
(1:0.2) or greater.
3. A loudspeaker according to claim 1, wherein the vibrating
section further includes a connector for connecting the diaphragm
and the spider to the voice coil.
4. A loudspeaker according to claim 2, wherein: a cross-section of
the surround has a generally half-circle shape; and at least one
protrusion is provided on the surround.
5. A loudspeaker according to claim 4, wherein the at least one
protrusion is provided on the surround according to a predetermined
pattern along a periphery of the surround.
6. A loudspeaker according to claim 4, wherein the at least one
protrusion is provided on the surround at random.
7. A loudspeaker according to claim 4, wherein at least one of the
at least one protrusion has a circular shape.
8. A loudspeaker according to claim 4, wherein the at least one
protrusion is formed of a same material as that of the
surround.
9. A loudspeaker according to claim 4, wherein the at least one
protrusion is formed of a material different from that of the
surround.
10. A loudspeaker according to claim 9, wherein an internal loss or
viscosity of a material used in the protrusion is higher than that
of a material used in the surround.
11. A loudspeaker according to claim 4, wherein the at least one
protrusion is filled with a material which has a specific gravity
greater than that of the surround.
12. A loudspeaker according to claim 2, wherein: the surround
includes a first film having a cross-section of a generally
half-circle shape, a second film having a cross-section of a
generally half-circle shape, and at least one weight formed of a
material whose density is higher than those of the first and second
films; and the at least one weight is sandwiched by the first and
second films.
13. A loudspeaker according to claim 12, wherein: a gap is provided
between the first and second films; and the gap is filled with a
liquid, a liquid in the form of gel, or a viscoelastic body.
14. A loudspeaker according to claim 2, wherein the surround has a
cavity which has a cross-section of a generally circular shape.
15. A loudspeaker according to claim 14, wherein the cavity of the
surround is filled with a liquid, a liquid in the form of gel, or a
viscoelastic body.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a loudspeaker wherein the weight
ratio between a vibrating part and a surround of the loudspeaker is
adjusted to be within a predetermined range so that the loudspeaker
reproduces sound of improved quality. Specifically, the present
invention relates to a thin loudspeaker having a diaphragm whose
height is relatively lower than its diameter so that the
loudspeaker reproduces sound with improved quality.
2. Description of the Related Art
Recently, there have been increasing demands for thinner and
lighter loudspeakers. In general, a loudspeaker includes a frame, a
surround, a magnetic circuit section, a vibrating section, etc.
FIG. 24 is a cross-sectional view showing a structure of a
conventional loudspeaker 100. The conventional loudspeaker 100
includes a voice coil 101, a diaphragm 102, a spider 103, a
surround 104, a frame 105, and a dust cap 110. The voice coil 101,
the diaphragm 102, the spider 103, and the dust cap 110 form a
vibrating section of the conventional loudspeaker 100.
The voice coil 101 is attached to the internal periphery of the
diaphragm 102 and connected to the frame 105 through the spider
103. The external periphery of the diaphragm 102 is connected to
the frame 105 through the surround 104. The dust cap 110 is
attached to the internal periphery of the diaphragm 102.
In the conventional loudspeaker 100, the weight ratio between the
vibrating section (formed by the voice coil 101, the diaphragm 102,
the spider 103, and the dust cap 110) and the surround 104 is 4:1.
The diaphragm 102 has a diameter of 120 mm and a height of 12 mm
(diameter:height =1:0.1).
FIG. 25 shows a sound pressure frequency characteristic of the
conventional loudspeaker 100 having a structure shown in FIG. 24.
In the graph of FIG. 25, the horizontal axis represents the
frequency, and the vertical axis represents the sound pressure
level. As seen in a region X encircled by a broken line, in the
conventional loudspeaker 100, a large turbulence of the sound
pressure level occurs in a middle frequency band of 200 Hz to 1
kHz. (Hereinafter, such a turbulence is referred to as "turbulence
of the sound pressure level in the middle band".)
In order to improve a space factor of a loudspeaker, it is
effective to reduce the height of the loudspeaker so as to obtain a
thin loudspeaker. For obtaining a thin loudspeaker, it is necessary
to reduce the height of a diaphragm of the loudspeaker. However,
when the height of a diaphragm is reduced, the strength of the
external periphery of the diaphragm decreases. In the case where an
electric signal is applied to a loudspeaker which uses such a
diaphragm of reduced height so as to allow the diaphragm to
vibrate, a large resonance occurs at the surround of the
loudspeaker and the external periphery of the diaphragm. This
resonance causes a turbulence of the sound pressure level in the
middle band of 200 Hz to 1 kHz.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a loudspeaker
includes: a frame; a vibrating section including a diaphragm having
an internal periphery and an external periphery, a voice coil
attached to the internal periphery of the diaphragm, a spider which
connects the voice coil to the frame, and a dust cap attached to
the internal periphery of the diaphragm; and a surround which
connects the external periphery of the diaphragm to the frame,
wherein the ratio between the weight of the vibrating section and
the weight of the surround is 0.9:1 to 1.5:1.
In one embodiment of the present invention, the ratio between the
diameter of the diaphragm and the height of the diaphragm is
(1:0.2) or greater.
In another embodiment of the present invention, the vibrating
section further includes a connector for connecting the diaphragm
and the spider to the voice coil.
In still another embodiment of the present invention, a
cross-section of the surround has a generally half-circle shape;
and at least one protrusion is provided on the surround.
In still another embodiment of the present invention, the at least
one protrusion is provided on the surround according to a
predetermined pattern along a periphery of the surround.
In still another embodiment of the present invention, the at least
one protrusion is provided on the surround at random.
In still another embodiment of the present invention, at least one
of the at least one protrusion has a circular shape.
In still another embodiment of the present invention, the at least
one protrusion is formed of a same material as that of the
surround.
In still another embodiment of the present invention, the at least
one protrusion is formed of a material different from that of the
surround.
In still another embodiment of the present invention, an internal
loss or viscosity of a material used in the protrusion is higher
than that of a material used in the surround.
In still another embodiment of the present invention, the at least
one protrusion is filled with a material which has a specific
gravity greater than that of the surround.
In still another embodiment of the present invention, the surround
includes a first film having a cross-section of a generally
half-circle shape, a second film having a cross-section of a
generally half-circle shape, and at least one weight formed of a
material whose density is higher than those of the first and second
films; and the at least one weight is sandwiched by the first and
second films.
In still another embodiment of the present invention, a gap is
provided between the first and second films; and the gap is filled
with a liquid, a liquid in the form of gel, or a viscoelastic
body.
In still another embodiment of the present invention, the surround
has a cavity which has a cross-section of a generally circular
shape.
In still another embodiment of the present invention, the cavity of
the surround is filled with a liquid, a liquid in the form of gel,
or a viscoelastic body.
Thus, the invention described herein makes possible the advantages
of providing a thin loudspeaker where the height of a diaphragm is
relatively small with respect to the diameter of the diaphragm and
which can produce sound with a small turbulence of the sound
pressure level in the middle band.
These and other advantages of the present invention will become
apparent to those skilled in the art upon reading and understanding
the following detailed description with reference to the
accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing a structure of a
loudspeaker according to embodiment 1 of the present invention.
FIG. 2 shows a mechanical equivalent circuit of a loudspeaker for
illustrating a mechanism of generation of a turbulence of the sound
pressure level in the middle band.
FIG. 3 is a cross-sectional view showing a structure of another
loudspeaker according to embodiment 1 of the present invention.
FIG. 4 shows a sound pressure frequency characteristic of the
loudspeaker according to embodiment 1 of the present invention.
FIG. 5 shows a sound pressure frequency characteristic of the
loudspeaker according to embodiment 1 of the present invention when
the weight ratio between a vibrating section and a surround of the
loudspeaker is changed within a range of 0.5:1 to 2:1.
FIG. 6 is a cross-sectional view showing a structure of a
loudspeaker according to embodiment 2 of the present invention.
FIG. 7 show a sound pressure frequency characteristic of a
conventional loudspeaker when the ratio between the diameter p and
the height h of a diaphragm is changed within a range of 1:0.1 to
1:0.3.
FIG. 8 show a sound pressure frequency characteristic of the
loudspeaker according to embodiment 2 where the weight ratio
between a vibrating section and a surround is 1.2:1 when the ratio
between the diameter p and the height h of a diaphragm is
changed.
FIG. 9 is an upper view of a surround of a loudspeaker according to
embodiment 3 of the present invention.
FIG. 10 is a cross-sectional view of the surround of the
loudspeaker shown in FIG. 9.
FIG. 11 is a cross-sectional view showing a variation of the
surround of the loudspeaker shown in FIG. 10.
FIG. 12 is an upper view showing another example of the surround of
the loudspeaker according to embodiment 3 of the present
invention.
FIG. 13 is a cross-sectional view of the surround of the
loudspeaker shown in FIG. 12.
FIG. 14 is a cross-sectional view showing a variation of the
surround of the loudspeaker shown in FIG. 13.
FIG. 15 is an upper view showing still another example of the
surround of the loudspeaker according to embodiment 3 of the
present invention.
FIG. 16 is a cross-sectional view of the surround of the
loudspeaker shown in FIG. 15.
FIG. 17 is a cross-sectional view showing a variation of the
surround of the loudspeaker shown in FIG. 16.
FIG. 18 is a cross-sectional view of a surround of a loudspeaker
according to embodiment 4 of the present invention.
FIG. 19 is a cross-sectional view showing a variation of the
surround of the loudspeaker shown in FIG. 18.
FIG. 20 is a cross-sectional view of a surround of a loudspeaker
according to embodiment 5 of the present invention.
FIG. 21 is a cross-sectional view showing a variation of the
surround of the loudspeaker shown in FIG. 20.
FIG. 22 is a cross-sectional view of a surround of a loudspeaker
according to embodiment 6 of the present invention.
FIG. 23 is a cross-sectional view showing a variation of the
surround of the loudspeaker shown in FIG. 22.
FIG. 24 is a cross-sectional view showing a structure of a
conventional loudspeaker.
FIG. 25 shows a sound pressure frequency characteristic of the
conventional loudspeaker shown in FIG. 24.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, embodiments of the present invention will be described
with reference to FIGS. 1 through 23.
(Embodiment 1)
FIG. 1 is a cross-sectional view showing a structure of a
loudspeaker 200 according to embodiment 1 of the present
invention.
The loudspeaker 200 includes a vibrating section 1000, and a
surround 4a. The vibrating section 1000 includes: a diaphragm 2
having internal and external peripheries; a voice coil 1 attached
to the internal periphery of the diaphragm 2; a spider 3 which
connects the voice coil 1 to the frame 5; and a dust cap 10
attached to the internal periphery of the diaphragm 2. In FIG. 1,
the extent of the vibrating section 1000 is represented by a region
A. The external periphery of the diaphragm 2 is connected to the
frame 5 through the surround 4a.
A bridging part between the external periphery of the diaphragm 2
and the frame 5 is defined as the surround 4a. The extent of the
surround 4a is represented by a region B. A bridging part between
the voice coil 1 and the frame 5 is defined as the spider 3. The
extent of the spider 3 is represented by a region C. The
definitions of the surround and the spider are also the same in
embodiments 2-6 which will be described later.
The loudspeaker 200 further includes a magnet 6, a center pole 7, a
yoke 8, and a magnetic gap 9. The magnet 6, the center pole 7, and
the yoke 8 form a magnetic circuit. The magnetic circuit generates
a magnetic flux in the magnetic gap 9. The voice coil 1 is inserted
in the magnetic gap 9. When an electric signal is applied to the
voice coil 1, the voice coil 1 vibrates, due to the magnetic flux
in the magnetic gap 9, by a power which is relative to the applied
electric signal. The vibration of the voice coil 1 is transmitted
through the diaphragm 2, the spider 3, and the dust cap 10 to the
surround 4a. The loudspeaker 200 vibrates up and down in a vertical
direction integrally with the voice coil 1. As a result, the
loudspeaker 200 reproduces sound.
In the loudspeaker 200, the weight ratio between the vibrating
section 1000 and the surround 4a is set within a range of 0.9:1 to
1.5:1. Setting of the weight ratio between the vibrating section
1000 and the surround 4a is achieved by, for example, adjusting the
weight of the surround 4a. The adjustment of the weight of the
surround 4a can be achieved by, for example, changing the thickness
or density of the surround 4a. Specific examples of the weight
adjustment of the surround 4a will be described later in
embodiments 3-6. Of course, according to the present invention, the
weight ratio between the vibrating section 1000 and the surround 4a
may be set within a range of 0.9:1 to 1.5:1 by adjusting the weight
of the vibrating section 1000. Alternatively, the weight ratio
between the vibrating section 1000 and the surround 4a may be set
within a range of 0.9:1 to 1.5:1 by adjusting both the weight of
the surround 4a and the weight of the vibrating section 1000.
Furthermore, in the loudspeaker 200, the cross-section of the
surround 4a has a generally half-circle shape which protrudes
downward as shown in FIG. 1. However, according to the present
invention, the cross-section of the surround 4a may have a
generally half-circle shape which protrudes upward or may have an
undulated shape which is generally employed in many loudspeakers.
In order to set the weight ratio between the vibrating section 1000
and the surround 4a within a range of 0.9:1 to 1.5:1, the thickness
of the surround 4a may be increased, or a high-density material may
be used in the surround 4a.
In a design of a conventional thin loudspeaker, there is no
suggestion of setting the weight ratio between a vibrating section
and a surround of the loudspeaker within a predetermined range.
This is because it is conventionally believed that it is only
necessary to use a material having a large loss factor for the
surround in order to suppress a turbulence of the sound pressure
level in the middle band, and that the weight of the vibrating
system (vibrating section) of the loudspeaker should not be
modified in view of improvement in the conversion efficiency of the
loudspeaker.
Differences in design concept between a conventional thin
loudspeaker and a thin loudspeaker of the present invention are now
described with reference to FIG. 2.
FIG. 2 shows a mechanical equivalent circuit 2000 of a loudspeaker.
The mechanical equivalent circuit 2000 includes: an electrodynamic
resistance, B12/Re 500; a mechanical resistance of a diaphragm and
a spider, Rms 501; a compliance of the spider, Cspider 502; mass of
a vibrating system including the diaphragm, the spider, and a voice
coil, Mdiaph 503; a mechanical resistance of a surround, Rsurround
504; a compliance of the surround, Csurround 505; mass of a
vibrating system of the surround, Msurround 506; and a driving
force of the loudspeaker which is generated by an electric input, F
507. In FIG. 2, a region M denotes a vibrating system (vibrating
section) including the diaphragm, spider, and voice coil. A region
N denotes a vibrating system of the surround. Furthermore, in the
region N, a resonance caused by the Msurround 506 and the Csurround
505 is a surround resonance.
Conventionally, it is believed that in order to suppress a surround
resonance in the region N, it is preferable to increase the
Rsurround 504, i.e., to use a material having a large loss factor
in the surround of the loudspeaker. However, in the case of a thin
loudspeaker having a reduced height, a very large resonance occurs.
Actually, there is no material having such a large loss factor that
can suppress such a very large resonance. When the Msurround 506 is
increased, i.e., the weight of the surround is increased, the mass
of the vibrating system of the loudspeaker is increased, and such
an increase in weight of the vibrating system may cause
deterioration in the conversion efficiency of the loudspeaker.
Thus, conventionally, the weight of the surround is not changed.
Furthermore, in view of the purpose of reducing the weight of the
loudspeaker, it is believed that a factor related to weight should
not be changed.
However, the present inventors found that the surround resonance
can be reduced to a very small resonance by optimizing the weight
ratio between the region M and the region N. Such an idea, i.e.,
suppressing the turbulence of the sound pressure level in the
middle band by adjusting the weight distribution among specific
components of the loudspeaker, is completely novel and cannot be
seen in any conventional loudspeaker, and this idea itself is the
essence of the present invention.
FIG. 3 is a cross-sectional view showing a structure of a
loudspeaker 300 according to embodiment 1 of the present
invention.
The loudspeaker 300 of FIG. 3 is different from the loudspeaker 200
of FIG. 1 in that a vibrating section 3000 of the loudspeaker 300
includes a connector 20 in addition to the components of the
vibrating section 1000 of the loudspeaker 200. The extent of the
vibrating section 3000 is represented by a region D.
The connector 20 connects a diaphragm 2 and a spider 3 to a voice
coil 1. The connector 20 is formed integrally with the vibrating
section 3000.
The components of the vibrating section 3000 are not limited to the
voice coil 1, the diaphragm 2, the spider 3, and a dust cap 10. Any
element can be a component of the vibrating section 3000 as long as
the element is formed integrally with the vibrating section 3000.
Also in the loudspeaker 300, the weight ratio between the vibrating
section 3000 and the surround 4a is set within a range of 0.9:1 to
1.5:1, whereby the same effect as that produced by the loudspeaker
200 (FIG. 1) can be obtained.
FIG. 4 shows a sound pressure frequency characteristic of the
loudspeaker 200 when the weight ratio between the vibrating section
1000 and the surround 4a is set to 1.1:1. In the graph of FIG. 4,
the horizontal axis represents the frequency, and the vertical axis
represents the sound pressure level. In FIG. 4, the sound pressure
level in the middle frequency band is shown in a region Y encircled
by a broken line. As seen from the region Y, a turbulence of the
sound pressure level in the middle band is very small, i.e., the
sound pressure level in the middle band is a generally "flat"
characteristic. Herein, "flat" may not be exactly flat, but is flat
in a practical use.
Parts (a)-(j) of FIG. 5 show a sound pressure frequency
characteristic of the loudspeaker 200 when the weight ratio between
the vibrating section 1000 and the surround 4a is changed within a
range of 0.5:1 to 2:1. In part (a), the weight ratio is 0.5:1; in
part (b), 0.8:1; in part (c), 0.9:1; in part (d), 1:1; in part (e),
1.1:1; in part (f), 1.2:1; in part (g), 1.3:1; in part (h), 1.4:1;
in part (i), 1.5:1; in part (j), 2:1.
Herein, in the case where the peak-dip difference of the sound
pressure level in the middle band of 200 Hz to 1 kHz is within
.+-.6 dB, the sound pressure frequency characteristic is "flat" in
a practical use. As seen from parts (c)-(i) of FIG. 5, when the
weight ratio between the vibrating section 1000 and the surround 4a
is be within a range of 0.9:1 to 1.5:1, a "flat" sound pressure
frequency characteristic can be obtained. When the weight ratio is
1.1:1 or 1.2:1, a "flattest" sound pressure frequency
characteristic can be obtained. In the examples illustrated in
parts (a)-(j), the sound pressure frequency characteristic is shown
for each of a plurality of preselected weight ratios. However, it
is needless to say that the sound pressure frequency characteristic
continuously changes between adjacent two of the preselected weight
ratios. Thus, a practically "flat" sound pressure frequency
characteristic can be obtained at any weight ratio within a range
of 0.9:1 to 1.5:1.
(Embodiment 2)
FIG. 6 is a cross-sectional view showing a structure of a
loudspeaker 400 according to embodiment 2 of the present
invention.
The loudspeaker 400 includes a vibrating section 4000, and a
surround 4b. The vibrating section 4000 includes: a diaphragm 2
having internal and external peripheries; a voice coil 1 attached
to the internal periphery of the diaphragm 2; a spider 3 which
connects the voice coil 1 to the frame 5; and a dust cap 10
attached to the internal periphery of the diaphragm 2. In FIG. 6,
the extent of the vibrating section 4000 is represented by a region
E. The external periphery of the diaphragm 2 is connected to the
frame 5 through the surround 4b.
The loudspeaker 400 further includes a magnet 6, a center pole 7, a
yoke 8, and a magnetic gap 9. The magnet 6, the center pole 7, and
the yoke 8 form a magnetic circuit. This magnetic circuit generates
a magnetic flux in the magnetic gap 9. The voice coil 1 is inserted
in the magnetic gap 9. When an electric signal is applied to the
voice coil 1, the voice coil 1 vibrates, due to the magnetic flux
in the magnetic gap 9, by a power which is relative to the applied
electric signal. The vibration of the voice coil 1 is transmitted
through the diaphragm 2, the spider 3, and the dust cap 10 to the
surround 4b. The loudspeaker 400 vibrates up and down in a vertical
direction integrally with the voice coil 1. As a result, the
loudspeaker 400 reproduces sound.
In the loudspeaker 400, the weight ratio between the vibrating
section 4000 and the surround 4b is set within a range of 0.9:1 to
1.5:1. Setting of the weight ratio between the vibrating section
4000 and the surround 4b is achieved by, for example, adjusting the
weight of the surround 4b. The adjustment of the weight of the
surround 4b can be achieved by, for example, changing the thickness
or density of the surround 4b. Alternatively, the weight ratio
between the vibrating section 4000 and the surround 4b may be set
within a range of 0.9:1 to 1.5:1 by adjusting the weight of the
vibrating section 4000 or by adjusting both the weight of the
surround 4b and the weight of the vibrating section 4000.
Furthermore, in the loudspeaker 400, the ratio between the diameter
p of the diaphragm 2 and the height h of the diaphragm 2 is set to
(1:0.2) or greater.
Further still, in the loudspeaker 400, the cross-section of the
surround 4b has a generally half-circle shape which protrudes
downward as shown in FIG. 6. However, according to the present
invention, the cross-section of the surround 4b may have a
generally half-circle shape which protrudes upward or may have an
undulated shape which is generally employed in many loudspeakers.
In order to set the weight ratio between the vibrating section 4000
and the surround 4b within a range of 0.9:1 to 1.5:1, the thickness
of the surround 4b may be increased, or a high-density material may
be used in the surround 4b.
Thus, the loudspeaker 400 has substantially the same structure as
that of the loudspeaker 200 shown in FIG. 1 except that in the
loudspeaker 400, the ratio between the diameter p of the diaphragm
2 and the height h of the diaphragm 2 is set to (1:0.2) or
greater.
Parts (a)-(e) of FIG. 7 show a sound pressure frequency
characteristic of the conventional loudspeaker 100 (FIG. 24) where
the weight ratio between the vibrating section and the surround is
4:1 when the ratio between the diameter and the height of the
diaphragm is changed within a range of 1:0.1 to 1:0.3. In part (a),
the ratio between diameter and height is 1:0.1; in part (b),
1:0.15; in part (c), 1:0.2; in part (d), 1:0.25; in part (e),
1:0.3. In parts (a)-(e) of FIG. 7, shown in each of regions C1-C5
is a turbulence of the sound pressure level in the middle band of
200 Hz to 1 kHz which is caused by a resonance of the surround and
the external periphery of the diaphragm.
As seen in parts (a)-(c) of FIG. 7, when the ratio between the
diameter p and the height h of the diaphragm is (1:0.2) or greater,
the peak-dip difference of the sound pressure level in the middle
band of 200 Hz to 1 kHz is .+-.6 dB or more. Thus, in the case of
using a thin diaphragm where the ratio between the diameter p and
height h of the diaphragm is (1:0.2) or greater, it is necessary to
remove the turbulence of the sound pressure level in the middle
band.
According to the present invention, even in a loudspeaker which
uses a thin diaphragm where the ratio between the diameter and
height of the diaphragm is (1:0.2) or greater, a turbulence of the
sound pressure level in the middle band, which results from a
resonance of the surround of the loudspeaker, can be reduced by
setting the weight ratio between the vibrating section and the
surround so as to be within a range of 0.9:1 to 1.5:1.
Parts (a)-(c) of FIG. 8 show a sound pressure frequency
characteristic of the loudspeaker 400 (FIG. 6) where the weight
ratio between the vibrating section 4000 and the surround 4b is
1.2:1 when the ratio between the diameter p and the height h of the
diaphragm 2 is changed within a range of 1:0.1 to 1:0.2. In part
(a), the ratio between diameter and height is 1:0.1; in part (b),
1:0.15; in part (c), 1:0.2. In parts (a)-(c) of FIG. 8, shown in
each of regions D1-D3 is a turbulence of the sound pressure level
in the middle band of 200 Hz to 1 kHz which is caused by a
resonance of the surround 4b and the external periphery of the
diaphragm 2.
According to the present invention, the turbulence of the sound
pressure level in the middle band seen in each of regions C1-C3 in
parts (a)-(c) of FIG. 7 is reduced as shown in each of regions
D1-D3 in parts (a)-(c) of FIG. 8. That is, according to the present
invention, a generally "flat" sound pressure frequency
characteristic can be obtained.
(Embodiment 3)
FIG. 9 is an upper view of a surround 4c of a loudspeaker according
to embodiment 3 of the present invention. FIG. 10 is a
cross-sectional view of the surround 4c. The upper surface of the
surround 4c has protrusions 11.
In the loudspeaker of embodiment 3, the ratio between the diameter
and the height of a diaphragm of the loudspeaker is set to (1:0.2)
or greater.
Furthermore, the weight ratio between the vibrating section and the
surround 4c is set so as to be within a range of 0.9:1 to 1.5:1 by
providing the protrusions 11 on the upper surface of the surround
4c. With such a method for setting the weight ratio, a turbulence
of the sound pressure level in the middle band, which occurs in a
conventional loudspeaker using a thin-shaped diaphragm with a
reduced height, can be removed, whereby a "flat" sound pressure
frequency characteristic can be obtained. This effect is the same
as those produced by the loudspeakers of embodiments 1 and 2.
Furthermore, by providing the protrusions 11 on the surface of the
surround 4c, the weight ratio between the vibrating section and the
surround 4c can be adjusted without increasing the thickness of the
surround 4c or using a high-density material in the surround 4c.
Thus, in the loudspeaker of embodiment 3, the compliance of the
surround can be freely designed as compared with the loudspeaker of
embodiment 1. As a result, adjustment of a minimum resonance
frequency of the loudspeaker can be readily performed.
If the cross-section of the surround has a uniform thickness as
shown in the loudspeaker 100 of FIG. 24, a single resonance occurs
along a radial direction of the surround, and this resonance
deteriorates the quality of sound reproduced by the loudspeaker.
However, in the loudspeaker of embodiment 3, the thickness of the
cross-section of the surround 4c is not uniform, and accordingly,
an undesirable resonance which may occur in the surround can be
dispersed. Therefore, an adverse effect by the surround resonance
on the characteristics of the loudspeaker is reduced, whereby the
quality of sound reproduced by the loudspeaker can be improved.
In the example illustrated in FIG. 10, the protrusion 11 is
provided on the concave surface of the surround 4c. However, the
protrusion 11 may be provided on the convex surface of the surround
4c as shown in FIG. 11.
Furthermore, the protrusions may be provided according to a
predetermined pattern along a periphery of the surround. (For
example, in FIG. 9, the protrusions 11 are provided at equal
intervals along the periphery of the surround 4c.) Alternatively,
as shown in FIG. 12 (upper view of a surround 4d) and FIG. 13
(cross-sectional view of the surround 4d), protrusions 11b may be
provided on the surround 4d at random. In such an arrangement, the
thickness of the cross-section of the surround 4d is not uniform,
and accordingly, an undesirable resonance which may occur in the
surround 4d can be dispersed. As a result, the quality of sound
reproduced by the loudspeaker can be improved. In the example
illustrated in FIG. 13, the protrusions 11b are provided on the
concave surface of the surround 4d. However, the protrusions 11b
may be provided on the convex surface of the surround 4d as shown
in FIG. 14.
Furthermore, as shown in FIG. 15 (upper view of a surround 4e) and
FIG. 16 (cross-sectional view of the surround 4e), a protrusion 11c
in the shape of a circle is provided on the surround 4e
concentrically with the surround 4e. In such an arrangement, an
undesirable resonance in the surround 4e is dispersed. As a result,
the quality of sound reproduced by the loudspeaker can be improved.
In the example illustrated in FIG. 16, the protrusion 11c is
provided on the concave surface of the surround 4e. However, the
protrusion 11c may be provided on the convex surface of the
surround 4e as shown in FIG. 17.
Furthermore, the protrusion may be formed of a same material (e.g.,
foamed rubber) as that of the surround and formed integrally with
the surround. Alternatively, the protrusion may be formed of a
material different from that of the surround and then attached to
the surround. In the latter case, if the protrusion is formed of a
high-density material (e.g., a metal), the weight of the surround
can be readily adjusted. If the protrusion is formed of a material
having a high internal loss or a material having a high viscosity
(e.g., butyl rubber), an effect of suppressing an undesirable
resonance in the surround can be obtained.
(Embodiment 4)
FIG. 18 is a cross-sectional view of a surround 4f of a loudspeaker
according to embodiment 4 of the present invention. The loudspeaker
of embodiment 4 has substantially the same structure as that of the
loudspeaker 200 according to embodiment 1 shown in FIG. 1 except
for the surround 4f. In FIG. 18, a reference numeral 11d denotes a
protrusion, a reference numeral 12 denotes a surface of the
protrusion 11d which is formed integrally with the surround 4f, and
a reference numeral 13 denotes a filling material having a specific
gravity larger than that of the material of the surround 4f.
Furthermore, in the loudspeaker of embodiment 4, the ratio between
the diameter p and the height h of a diaphragm 2 is set to (1:0.2)
or greater.
In the loud speaker of embodiment 4, the surround 4f has the
protrusion 11d, and the protrusion 11d is filled with the filling
material 13 which has a specific gravity greater than that of a
material of the surround 4f such that the weight ratio between the
vibrating part and the surround 4f is set so as to be within a
range of 0.9:1 to 1.5:1. With such a setting of the weight ratio, a
turbulence of the sound pressure level in the middle band, which
occurs in a conventional loudspeaker using a thin-shaped diaphragm
with a reduced height, can be removed, whereby a "flat " sound
pressure frequency characteristic can be obtained. This effect is
the same as those produced by the loudspeakers of embodiments 1 and
2. When a material having a high internal loss or a material having
a high viscosity (e.g., silicon or the like), an effect of
suppressing an undesirable resonance in the surround 4f can be
obtained, whereby the quality of sound reproduced by the
loudspeaker can be further improved.
In the example illustrated in FIG. 18, the protrusion 11d is formed
so as to protrude from the convex surface of the surround 4f.
However, the protrusion may be formed so as to protrude from the
concave surface of the surround as shown in FIG. 19. The filling
material 13 stuffed in a protrusion 11e of a surround 4g does not
drop from the protrusion 11e so long as a material having a
relatively high viscosity is used as the filling material 13. Thus,
a loudspeaker which provides a stable performance can be easily
fabricated.
The shape and material of the surround of the loudspeaker shown in
each of FIGS. 9 through 19 are appropriately selected in view of
the design of a compliance of a surround, easiness of production,
the appearance of the loudspeaker, etc.
(Embodiment 5)
FIG. 20 is a cross-sectional view of a surround 4h of a loudspeaker
according to embodiment 5 of the present invention. The loudspeaker
of embodiment 5 has substantially the same structure as that of the
loudspeaker 200 according to embodiment 1 shown in FIG. 1 except
for the surround 4h. In FIG. 20, a reference numeral 14 denotes a
first film, a reference numeral 15 denotes a second film, and a
reference numeral 16 denotes a weight made of a material different
from those of the first film 14 and the second film 15. The weight
16 is sandwiched by the first film 14 and the second film 15. The
cross section of each of the first film 14 and the second film 15
has a generally half-circle shape. In the loudspeaker of embodiment
5, the ratio between the diameter p and the height h of a diaphragm
2 is set to (1:0.2) or greater.
In the loudspeaker of embodiment 5, the first film 14, the second
film 15, and the weight 16 which is provided so as to be sandwiched
by the films 14 and 15 form the surround 4h. The weight ratio
between a vibrating section and the surround 4h is set so as to be
within a range of 0.9:1 to 1.5:1. With such a setting of the weight
ratio, a turbulence of the sound pressure level in the middle band,
which occurs in a conventional loudspeaker using a thin-shaped
diaphragm with a reduced height, can be removed, whereby a "flat"
sound pressure frequency characteristic can be obtained. This
effect is the same as those produced by the loudspeakers of
embodiments 1 and 2.
Furthermore, the weight 16 for adjusting the weight of the surround
4h may be made of a high-density material (e.g., a metal) in view
of the easiness of adjustment, or may be made of a material having
a high internal loss or a material having a high viscosity (e.g.,
butyl rubber) for the purpose of improving an effect of suppressing
an undesirable resonance in the surround 4h.
Furthermore, the weight 16 may be shaped in the form of one or more
circles and provided in a gap between the first film 14 and the
second film 15 concentrically with the surround 4h. Alternatively,
the weight 16 may be shaped in the form of a plurality of lumps and
provided in a gap between the first film 14 and the second film 15
according to a predetermined pattern or at random.
Since the surround 4h is structured such that the weight 16 is
sandwiched by a plurality of films, there is no possibility that
the weight 16 is dropped off from the surround 4h, and thus, a
highly reliable structure is realized in the surround 4h.
Further still, as shown in FIG. 21, a surround 4i may be structured
such that the gap between the first film 14 and the second film 15
is filled with a damping material 17, such as a liquid, a liquid in
the form of gel, or a viscoelastic body. In this case, an effect of
suppressing an undesirable resonance in the surround 4i can be
further improved for the sake of a damping effect produced by the
damping material 17.
(Embodiment 6)
FIG. 22 is a cross-sectional view of a surround 4j of a loudspeaker
according to embodiment 6 of the present invention. The loudspeaker
of embodiment 6 has substantially the same structure as that of the
loudspeaker 200 according to embodiment 1 shown in FIG. 1 except
for the surround 4j. The cross section of the surround 4j of the
loudspeaker according to embodiment 6 has a generally circle shape,
and the surround 4j has a cavity 18. In the loudspeaker of
embodiment 6, the ratio between the diameter p and the height h of
a diaphragm 2 is set to (1:0.2) or greater.
In the loud speaker of embodiment 6, the surround 4j is shaped such
that a cross-section thereof has a generally circle shape, so that
the weight of the surround 4j is greater than that of the surround
104 of the conventional loudspeaker 100 (FIG. 24) whose
cross-section has a generally half-circle shape. Thus, if the
weight of the half-circular surround is insufficient, by using such
a surround structure having a circular cross-section, the weight
ratio between the vibrating section and the surround can be
adjusted so as to be within a range of 0.9:1 to 1.5:1. With such a
setting of the weight ratio, a turbulence of the sound pressure
level in the middle band, which occurs in a conventional
loudspeaker using a thin-shaped diaphragm with a reduced height,
can be removed, whereby a "flat" sound pressure frequency
characteristic can be obtained. This effect is the same as those
produced by the loudspeakers of embodiments 1 and 2.
Furthermore, in the loudspeaker of embodiment 6, it is not
necessary to provide a protrusion (as described in embodiments 3
and 4) or a weight (as described in embodiment 5) to the surround
4j. Therefore, the fabrication of the surround 4j is easier.
Furthermore, as shown in FIG. 23, the cavity 18 of a surround 4k
may be filled with a damping material, such as a liquid, a liquid
in the form of gel, or a viscoelastic body. In this case, an effect
of suppressing an undesirable resonance in the surround 4k can be
further improved for the sake of a damping effect produced by the
damping material. Furthermore, if the weight of the surround 4j
(FIG. 22) is insufficient, the weight ratio between the vibrating
section and the surround can be adjusted with such a filled
material so as to be within a range of 0.9:1 to 1.5:1.
According to the present invention, the weight ratio between a
vibrating section and a surround of a loudspeaker is adjusted so as
to be within a range of 0.9:1 to 1.5:1, whereby a turbulence of the
sound pressure level in the middle band which occurs in a
conventional loudspeaker can be removed. As a result, a "flat"
sound pressure frequency characteristic can be obtained. The
present invention is especially effective for a thin loudspeaker
where the ratio between the diameter p and the height h of a
diaphragm is (1:0.2) or greater.
Furthermore, the surround is provided with at least one protrusion;
the surround is formed by first and second films each having a
generally half-circle cross-section and a weight interposed
therebetween; or the surround is structured so as to have a
generally circular cross-section and is filled with a damping
material, such as a liquid, a liquid in the form of gel, or a
viscoelastic body. With such a structure, an undesirable resonance
in the surround is suppressed, and accordingly, the quality of
sound reproduced by the loudspeaker can be improved.
Various other modifications will be apparent to and can be readily
made by those skilled in the art without departing from the scope
and spirit of this invention. Accordingly, it is not intended that
the scope of the claims appended hereto be limited to the
description as set forth herein, but rather that the claims be
broadly construed.
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