U.S. patent number 3,717,218 [Application Number 05/130,086] was granted by the patent office on 1973-02-20 for loudspeaker.
This patent grant is currently assigned to Nippon Columbia Co., Ltd., Hisao Sato. Invention is credited to Yoshihide Arakawa, Hisao Sato, Takeo Shiga, Toshihiko Takagi.
United States Patent |
3,717,218 |
Shiga , et al. |
February 20, 1973 |
LOUDSPEAKER
Abstract
A loudspeaker having a cone suspension system which is formed of
materials such as collagen fiber, a mixture of collagen fiber with
other fiber, collagen fiber impregnated with asphalt or latex, or
other fibers impregnated with asphalt or latex to improve the
frequency response characteristic.
Inventors: |
Shiga; Takeo (Kawasaki,
JA), Takagi; Toshihiko (Kanagawa-ken, JA),
Arakawa; Yoshihide (Kita-ku, JA), Sato; Hisao
(Tokyo, JA) |
Assignee: |
Sato; Hisao (Tokyo,
JA)
Nippon Columbia Co., Ltd. (Kanagawa-ken, JA)
|
Family
ID: |
12283145 |
Appl.
No.: |
05/130,086 |
Filed: |
April 1, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Apr 7, 1970 [JA] |
|
|
45/29692 |
|
Current U.S.
Class: |
181/167 |
Current CPC
Class: |
H04R
7/20 (20130101) |
Current International
Class: |
H04R
7/00 (20060101); H04R 7/20 (20060101); G10k
013/00 (); H04r 007/00 () |
Field of
Search: |
;181/32R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Tomsky; Stephen J.
Claims
What is claimed is:
1. A loudspeaker having a cone with a cone suspension means made of
a sheet of randomly aligned collagen fibers and polyvinyl alcohol
as a binder.
2. A loudspeaker having a cone with a cone suspension means
according to claim 1 wherein said randomly aligned collagen sheet
includes wood pulp.
3. A loudspeaker having a cone with a cone suspension means
according to claim 1 wherein said randomly aligned collagen sheet
includes rayon and cotton.
4. A loudspeaker having a cone with a cone suspension means
according to claim 1 wherein said randomly aligned collagen sheet
is impregnated with latex.
5. A loudspeaker having a cone with a cone suspension means
according to claim 4 wherein the amount of latex in said sheet of
randomly aligned collagen fibers is about 10 to 50 percent by
weight with respect to said sheet.
6. A loudspeaker having a cone with a cone suspension means
according to claim 1 wherein said randomly aligned collagen sheet
is impregnated with asphalt.
7. A loudspeaker having a cone with a cone suspension means
according to claim 1 wherein said randomly aligned collagen sheet
has about 50 to 100 percent by weight of collagen with respect to
the weight of the sheet.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a loudspeaker, and more particularly to a
loudspeaker with a cone suspension system for supporting the cone
of the loudspeaker.
2. Description of the Prior Art
For the suspension of the cone in conventional loudspeakers a free
edge is employed which is formed of oxhide or cowhide, kid skin or
synthetic foam rubber. Leather is a natural product and it is
difficult to obtain uniform quality and is expensive and unsuitable
for mass production. Synthetic foam rubber is also expensive and
has a frequency characteristic which causes a decrease in the
damping effect, and the synthetic foam rubber is used only in
high-grade or special loudspeakers.
SUMMARY OF THE INVENTION
One object of this invention is to provide a loudspeaker having a
cone suspension which provides for improved response in the
low-frequency band and lowers the Q in the vicinity of the
resonance frequency of the low-frequency band.
Another object of this invention is to provide a loudspeaker having
a cone suspension which provides for improved response in the
middle-frequency band and prevents anti-resonance due to the
suspension.
Another object of this invention is to provide a loudspeaker having
a cone suspension which has uniform characteristics in the
middle-frequency band and compensates for distortion in the
high-frequency band.
Another object of this invention is to provide a loudspeaker with a
cone suspension made of collagen fiber or of material containing
collagen fiber.
Still another object of this invention is to provide a loudspeaker
with a collagen cone suspension containing latex or asphalt.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows, partly in cross-section, one example of a loudspeaker
of this invention;
FIG. 2 is a graph illustrating the frequency response
characteristics of the loudspeaker of this invention and a
conventional loudspeaker; and
FIG. 3 is a graph similar to FIG. 2, showing the frequency response
characteristics of a modified form of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
For a better understanding of this invention, the characteristics
of a loudspeaker will be discussed.
"Q" is defined for a loudspeaker by the equation Q= F.sub.2
-F.sub.1 /F.sub.0 where F.sub.0 is the resonant frequency of the
speaker and F.sub.1 is the frequency below F.sub.0 where the
response is 3dB below the response at F.sub.0 and F.sub.2 is the
frequency above F.sub.0 where the response is 3dB below the
response at F.sub.0.
Generally, the frequency response characteristics of a loudspeaker
is divided into the low-, middle- and high-frequency ranges
according to the vibration modes of the loudspeaker. For the
low-frequency response characteristic in the vicinity of the
resonance frequency, the speaker should have a Q of about 0.7. With
Q greater than 0.7, the low-frequency characteristic abruptly rises
in the vicinity of the resonance frequency and deteriorates the
transient response. With Q smaller than 0.7, the reproduction of
low-frequency sound is not adequate and the transient response is
excessively damped. Since the cone performs a piston movement as a
substantially unitary structure with the cone suspension over the
low-frequency range to the middle-frequency range, the response
characteristic in the middle-frequency range is substantially flat.
However, the cone and the cone suspension (edge) vibrate in
opposite phase at a frequency higher than a certain frequency in
the middle-frequency range. This introduces a dip or trough in the
frequency response which increases distortion and deteriorates
quality of sound. When the width of the cone suspension is great,
the sound wave radiated from the suspension is large and the dip or
trough in the characteristic is deep. When the width of the cone
suspension is small, on the contrary, the dip or trough in the
characteristic is shallow. However, the narrow cone suspension
causes non-linearity in the low-frequency range when the amplitude
of the cone is great, and non-linear distortion increases and
resonance in the low-frequency range increases. This makes it
necessary to decrease the trough in the characteristic in the
middle-frequency range which depends on the material, shape and
size of the cone suspension.
The material of the cone may be a mixture of Japanese paper as of
"mitsumata," a mulberry paper or the like or foreign paper as of
pulp or the like with other fibers or porous foam synthetic resin.
The fixed edge of the cone suspension is formed generally of the
same paper fiber as that used for the cone and is hard and stiff
which causes non-linear distortion. Attempts to remove this
drawback introduces anti-resonance in the middle-frequency range
and causes a deep trough in the frequency characteristic. To avoid
this, the cone suspension is often coated with damping material
such as viscolloid or the like but the characteristic of the coated
damping material deteriorates with time and is effective only for a
short time.
Thus the object of the present invention is to provide a
loudspeaker with a cone suspension which has excellent
low-frequency characteristics and prevents anti-resonance in the
middle-frequency characteristic.
Collagen is the material used in the cone suspension in this
invention. Collagen is contained in the skins of animals and is
obtained by the following method. The first step is to immerse a
chrome-tanned hide for about 16 hours in about 500 percent by
weight of water (with respect to the chrome-tanned hide) which has
a temperature of 50.degree. to 60.degree.C and which contains about
0.05 percent by weight of non-ionic activator relative to the
chrome-tanned hide. Then, the chrome-tanned hide is rinsed with
water in a drum for one hour, after which the hide is subjected to
a neutralization treatment for one hour in about 200 percent by
weight of water relative to the chrome-tanned hide which has a
temperature of about 40.degree.C and which contains approximately
1.0 percent by weight of soda dicarbonate relative to the hide.
Then the hide is rinsed with water for thirty minutes. Next, the
hide is treated with about 2.5 percent by weight of sulfonated
olive oil relative to the hide together with approximately 200
percent by weight of water relative to the hide which has a
temperature of about 60.degree. C for 30 minutes. Then the hide is
dehydrated by a centrifugal hydroextractor and dried by a hot-air
blower at about 50.degree.C to adjust the water content to about 35
to 45 percent. The hide is then tapped with a stamp mill for about
thirty minutes and is pressed against a cloth provided with needles
5 mm. long and wrapped around the peripheral surface of a wooden
roll which is driven at a speed of 1,300 rpm and is 3 inches in
diameter and 5 inches wide. Thus, the fiber of the hide is frayed
to obtain collagen fiber.
The collagen fiber thus obtained is a cluster of very thin fibers
and many thin monofils are divided from one fascicule. The fiber is
very soft but strong. The collagen fiber substantially dampens
vibrations and is effective for attenuating sound vibrations.
FIG. 1 illustrates one example of a loudspeaker according to this
invention.
In FIG. 1 reference numeral 1 indicates generally a loudspeaker, in
which a frame 3 is supported by a yoke 2 which has a magnet
disposed centrally thereof. An edge or cone suspension member 5 is
fixed between the periphery of the frame 3 and an annular gasket 4.
The making of the edge or the cone suspension member 5 will be
described later. A cone 6 is connected to a voice coil disposed in
a magnetic gap between the magnet and the yoke 2. The contact faces
of the edge or cone suspension member 5 and the cone 6 are bonded
together with a suitable adhesive binder.
The cone suspension member 5 is manufactured in the following
manner:
E X A M P L E I
Material collagen 70% (by weight) wood pulp 28% (by weight)
polyvinyl alcohol (as a binder) 2% (by weight)
The above materials are mixed and formed into a sheet having a
thickness of 0.25 mm. The sheet is molded by a press at a
temperature of 120.degree. to 130.degree.C under a pressure of 1
Kg/cm.sup.2.
E X A M P L E II
Material collagen 50% (by weight) rayon 30% (by weight) cotton 18%
(by weight) polyvinyl alcohol 2% (by weight)
The sheet is formed and molded under the same conditions as in
Example I.
FIG. 2 is a graph showing frequency response characteristics of a
loudspeaker having a diameter of 20 cm and provided with the cone
suspension member 5. Curve a is for a speaker produced constructed
according to Example I. Curve b is for a loudspeaker similar having
a cone suspension member 5 constructed according to Example II.
Curve c illustrates the response of a conventional loudspeaker of
the prior art. In FIG. 2, the abscissa represents frequency in KHz
and the ordinate represents response in dB.
As will be apparent from FIG. 2, in the conventional loudspeaker a
trough 9 is produced in the characteristic c (solid line curve) at
about 500 Hz in the middle-frequency. However, in loudspeakers
according to this invention, the characteristics curves a and b
(curve a in dotted line, curve be in dash-claim line) are flattened
and the characteristics in the low-frequency range are gentle and
the characteristics in the high-frequency range are improved. In
other words, the dip or trough has been substantially reduced.
Another embodiment of the invention comprises a cone suspension
such as produced by the methods of Examples I or II which is
impregnated with latex or asphalt. For example, the sheet produced
in the Examples of I or II is impregnated with latex or asphalt and
is dried at 70.degree. to 80.degree.C, then is molded in a
press.
The amount of latex or asphalt impregnated into the sheet is about
10 to 50 percent by weight relative to the sheet. The frequency
characteristic of a loudspeaker employing such a cone suspension
member is as shown in FIG. 3.
In FIG. 3, the ordinate represents response in dB and the abscissa
frequency in KHz. A dash-dot line curve d is the frequency
characteristic of a loudspeaker employing a cone suspension
impregnated with about 25 percent by weight of latex. A dotted line
curve e is the frequency characteristic of a loudspeaker employing
a cone suspension impregnated with less than 10 percent by weight
of latex. A solid line curve f is the frequency characteristic of a
loudspeaker using a cone suspension impregnated with more than 50
percent by weight of latex. We have found that the optimum value of
latex is 25 percent.
In the foregoing Examples, the amounts of collagen used are
respectively selected at about 70 and 50 percent but, in practice,
the softness of the cone suspension can be variously selected by
selecting the amount of collagen in the range of 50 to 100 percent.
An increase in the amount of collagen used causes an increase in
the softness of the cone suspension.
The amount of latex or asphalt impregnated into the sheet for the
cone suspension (in Example III) can be selected at will. An
increase in the amount of latex or asphalt used causes an increase
in the hardness of the cone suspension.
It will be seen that the loudspeaker of this invention compensates
for the lowering of response due to anti-resonance in the
middle-frequency range.
In the invention a natural hide is not used but a hide is processed
into collagen fiber and then used after being shaped into a desired
form. This ensures uniformity in the quality of the edges or cone
suspensions produced. Collagen fibers may be produced from waste
hides. Accordingly, the present invention provides speakers of low
cost and improved performance.
It will be apparent that many modifications and variations may be
effected without departing from the scope of the novel concepts of
this invention.
* * * * *