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JPH0593199

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DESCRIPTION JPH0593199
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
cone speaker for use in an audio apparatus or the like, and more particularly to a cone speaker in
which distortion of sound output with respect to an input signal is minimized.
[0002]
A cone speaker is also called a direct radiation speaker because it directly transmits the vibration
of the diaphragm to the air and listens as a sound. A typical structural example of a conventional
cone speaker is schematically illustrated in FIG. There, a voice coil 17 is wound around the center
of a conical diaphragm 12 called a cone, and an audio electrical signal from an acoustic signal
line 22 is given to the voice coil 17 through a terminal plate 18 attached to the speaker frame
11. Be The permanent magnet 20 and the center pole 21 and the yoke 19 made of a
magnetically permeable member surrounding the permanent magnet 20 form a closed magnetic
path, and in the figure form a so-called external magnetic magnetic circuit.
[0003]
Also, a damper 16 is used to properly hold the voice coil 17 in the magnetic field between the
center pole 21 and the yoke 19, and an edge 13 is used to support the periphery of the cone. The
center cap 15 at the center of the cone is for the purpose of dustproofing the magnetic circuit.
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Now, when an audio electrical signal from the acoustic signal line 22 is given to the voice coil 17,
a cone according to Fleming's left-hand law in relation to the magnetic field between the center
pole 21 and the yoke 19 and the current of the voice coil 17. Moves up and down according to
the signal, and its vibration generates an acoustic output.
[0004]
However, the above-described conventional cone speaker driving method involves one-point
driving by the voice coil 17 at the center of the cone 12 and the damper 16 at the central portion
of the cone 12 and the edge 13 at the peripheral portion. It is by point support. Conventionally,
in order to vibrate the cone 12 in a linear manner with respect to an input signal, improvement
of materials such as the cone 12, the damper 16 and the edge 13 and corrugation of a waveform
concentrically formed thereon is continued. However, as described above, in the method of onepoint drive by the voice coil 17 and by the two-point support by the damper 16 and the edge 13,
the improvement is structurally limited.
[0005]
FIG. 4 shows an example of distortion factor frequency characteristics of a conventional cone
speaker. In the figure, the characteristic curve 23 shows a so-called sound pressure frequency
characteristic, which applies an audio frequency of constant voltage to the voice coil of the
speaker placed in the anechoic chamber and a standard microphone at a constant distance on the
axis of the speaker. It arranges, the said audio frequency is changed continuously, the output
voltage is measured, and it converts into a sound pressure level. The sound pressure frequency
characteristic 23 is maximized at the lowest resonance frequency determined by the mass of the
cone or voice coil, the inertia mass during their vibration, and the elastic force of the edge or
damper in the low frequency range, The sound pressure characteristic approaches a constant,
and it attenuates in proportion to the square of the frequency above the reproduction limit
frequency determined by the cone shape, the opening angle, the material, the mass of the voice
coil, etc. When
[0006]
Characteristic curve 24 indicates the strain rate. This is expressed as a percentage of the ratio of
the total sound output from the speaker to the total harmonic component different from the
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2
input frequency in the speaker sound output, but the distortion is caused by the voice coil
coming out of the even flux distribution In the case of magnetomotive force reduction that occurs
when there is a problem, there is also a significant increase in non-linear distortion due to the
fact that the amplitude of the cone increases in proportion to the square of the frequency as
distortion in the bass region of the figure. In addition, non-linear change with respect to
displacement of the edge or damper also causes distortion when the amplitude is large. The
distortion in the middle and high range is often caused by high-order resonance in which the
entire edge of the cone resonates to oscillate in antiphase with the cone, or local excessive
vibration due to split vibration. Further, the distortion increases near the reproduction limit
frequency due to nonlinear distortion in which the amplitude of the cone is attenuated in
proportion to the square of the frequency.
[0007]
FIG. 5 shows how the entire edge 13 mentioned above resonates and vibrates in the opposite
phase to the cone 12. In the figure, the vibration direction of the cone 12 and the vibration
direction of the edge 13 are opposite to each other at the point of intersection of the solid line
and the dotted line. become. This is due to the basic structure of a cone speaker such as driving a
single point of the voice coil 17 in the central portion of the cone 12 and fixing the edge 13 in
the peripheral portion of the cone 12 and the shape and material of the cone 12 and the edge 13
, Thickness, weight, and the influence of the aforementioned corrugation etc.
[0008]
Therefore, in view of the above problems, the object of the present invention is to drive the
central portion of the cone 12 by the voice coil 17 in addition to the peripheral portion of the
cone 12 in order to reduce the acoustic output distortion due to the resonance characteristic of
the edge shown in FIG. The drive means corresponding to the voice coil is used without fixing the
part as in the prior art so that the vibration (drive) directions of the voice coil in the central part
of the cone 12 and the drive means in the peripheral part are opposite in phase. Thus, it is an
object of the present invention to provide a cone speaker in which only a uniform force is always
applied to the cone 12 itself regardless of the input signal frequency, the amplitude, etc., and the
force for bending the so-called cone 12 does not work. According to this, the above-mentioned
resonance characteristic near the edge does not occur, and hence the acoustic output distortion
due to it does not occur either.
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[0009]
According to the present invention, according to the present invention, as shown in FIG. 1, a cone
1 consisting of a conical diaphragm, said cone 1 by converting an electric signal from an acoustic
signal source 5 into an acoustic vibration. First electric-acoustic conversion means 2 for driving
the central portion of the second electric-acoustic conversion means, the electric signal from the
acoustic signal source 5 is converted into acoustic vibration, and the cone is opposite phase to
the drive by the first electric-acoustic conversion means 2 From the speaker frame 4 supporting
the second electro-acoustic transducing means 3 for driving the peripheral portion of 1 and the
cone 1, the first electro-acoustic transducing means 2 and the second electro-acoustic
transducing means 3 A constituent cone speaker is provided.
[0010]
The first electro-acoustic conversion means 2 converts the electric signal from the acoustic signal
source 5 into the acoustic vibration of the central portion of the cone 1.
The second electro-acoustic conversion means 3 disposed at the periphery of the cone 1 converts
the electric signal from the acoustic signal source 5 into the acoustic vibration of the periphery
of the cone 1. The sound is converted in the opposite phase to the sound conversion means 2.
Therefore, when one of the two electro-acoustic conversion means 1 and 2 pushes the cone 1
during the vertical vibration of the cone 1, the other pulls, and when one pulls the other, the
other pushes. In this case, even if the frequency and amplitude of the input signal change, a
substantially uniform force is applied, and in particular, no force for bending the cone 1 acts.
Therefore, the edge resonance distortion shown in FIG. 5 does not occur in this state.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 2 schematically shows an
embodiment of a cone speaker according to the present invention. The same reference numerals
as in FIG. 3 denote the same parts in FIG. Also, in relation to FIG. 1, the first electro-acoustic
conversion means 2 corresponds to the above-mentioned magnetic circuits 16 to 22 in FIG. 2,
and the cone 1 and the speaker frame 4 in FIG. Each corresponds to 11. The second electroacoustic transducer means 3 of FIG. 1, which characterizes the present invention, comprises the
permanent magnet 31 of FIG. 2, the yoke 32, the projecting portion 33 of the cone and the
second voice coil 34 wound thereon.
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[0012]
The parts other than the part corresponding to the second electro-acoustic conversion means 2
in FIG. 2 are not replaced with the conventional example (FIG. 3) already described, and therefore
will not be described again here. The permanent magnet 31 of FIG. 2 and the yoke 32 formed of
a magnetically permeable member form a so-called internal magnetic magnetic circuit. As
described above, in the present embodiment, the magnetic circuit at the center of the cone 12
uses an external magnetic type magnetic circuit. The inner magnetic type has the advantage of
less magnetic leakage and the disadvantage that the magnetic resistance is increased because a
long magnet is required to obtain large magnetic energy, while the external magnetic type has
large magnetic leakage. Since the cross-sectional area of the magnet can be taken large, it is
characterized in that a high magnetic force such as ferrite and a high magnetic resistance can be
used. Therefore, in the present embodiment, an external magnetic circuit is provided in the
center of the cone 12 requiring a large driving force, and an internal magnetic field is provided
for the magnetic circuit in the peripheral portion of the cone 12 by a large shape or a plurality of
installations. Shape is used.
[0013]
The cone projections 33 provided on the inside of the edge 13 around the cone 12 of FIG. 2 are
inserted in the air gaps between the yokes 32 of the magnetic circuit according to the invention.
The second voice coil 34 connected to the acoustic signal line 22 is wound around the cone
protrusion 33. In this case, as described above, in order to cause the force acting on the
conventional voice coil 17 and the force acting on the second voice coil 14 according to the
present invention to act in opposite directions, the connecting direction of the acoustic signal line
22 to the coil 14; The winding direction of the coil 14 and the polarity of the permanent magnet
31 are adjusted. Therefore, in the case of the cone 12 of this example, the state in which the
force in the same direction is always uniformly applied to the central portion and the peripheral
portion of the cone 12 regardless of the input frequency and input amplitude is maintained. The
force does not work, and the acoustic output distortion due to the edge resonance described
above does not occur.
[0014]
In the case of the embodiment of FIG. 2, the case where the donut-shaped magnetic circuit is
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disposed on the outer periphery of the cone 12 is shown, but, for example, local arrangement
such as 4-point arrangement of the magnetic circuit on the outer periphery is shown. The
magnetic circuit according to the present invention may be arranged in In that case, it is obvious
that the same effect as described above according to the present invention can be obtained.
[0015]
As described above, the cone speaker according to the present invention does not in principle
generate an acoustic output distortion due to the resonance characteristic of the edge, and even
if the acoustic output distortion occurs in a real speaker, it does not The second electro-acoustic
conversion means according to the present invention may be provided in the form of a donut
around the entire circumference of the cone, or may be arranged locally at several points on the
circumference. In addition, the second electro-acoustic conversion means according to the
present invention can be incorporated into a conventional loudspeaker with almost no change in
its shape, while being able to flexibly cope with manufacturing requirements due to the
application, shape, performance and cost of the loudspeaker. Because it is possible, only the
speaker inside the audio device can be easily replaced by the speaker according to the present
invention.
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