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JPS59153398

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DESCRIPTION JPS59153398
[0001]
The present invention relates to a sound reproducing apparatus, in particular, a diaphragm
elastically supported by positioning a base in a magnetic path, a voice coil mounted on the base,
and a sound current supplied to the voice coil to vibrate the diaphragm. The present invention
relates to a sound reproduction apparatus provided with an amplifier. Heretofore, there has been
one shown in FIG. 1 as an equivalent circuit representing this kind of sound reproducing
apparatus. In FIG. 1, the signal input terminal 10 is connected to the positive input terminal of an
amplifier 12 and the output terminal of this amplifier 12 is connected to the input terminal of the
speaker 14 and feedback provided in series between the output terminal and the ground 16 A
connection point P of the resistors 18a and 18b is connected to the negative input terminal of
the amplifier 12. With the above configuration, the amplifier 12 amplifies the input signal and
supplies audio power to the speaker 14 while the output voltage is divided by the feedback
resistors 18M-18b and input to the negative input terminal of the amplifier 12. Therefore, if the
gain of the amplifier 12 is sufficiently thick, the above feedback can significantly improve the
distortion and frequency characteristics of the amplifier I2. That is, the feedback improves the
characteristic between the input and output of the amplifier and generates a voltage at the
output of the amplifier that is proportional to the input voltage. However, since the impedance of
the speaker 4 supplied to the amplifier 12 fluctuates considerably depending on the frequency,
the sound pressure finally generated from the speaker 4 must be necessarily proportional to the
input voltage. Therefore, at present, it is necessary to take measures such as sharing the output
for each frequency using a plurality of speakers. The present invention has been made in view of
the above-described conventional problems, and an object thereof is to provide a sound
reproducing apparatus having an overall improved sound quality. In order to achieve the above
object, the present invention vibrates the diaphragm by supplying the diaphragm to a diaphragm
supported elastically by positioning the base in a magnetic path, a voice coil mounted on the
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base, and the voice coil. A sound reproducing apparatus comprising an audio current amplifier,
wherein a sound pressure sensor for detecting a sound pressure is provided on the diaphragm or
in front of the diaphragm, and an output signal of the sound pressure sensor is input to the
amplifier It is characterized by feedback. Hereinafter, preferred embodiments of the present
invention will be described based on the drawings. FIG. 2 is a very schematic enlarged view
showing the structure of a speaker applied to the sound reproducing apparatus of the present
invention. In FIG. 2, the speaker horn 20 has a V-shaped longitudinal cross section, and the
opening peripheral edge portion 20a is overlapped with the opening peripheral edge 22 & of the
diaphragm 22 forming the V-shaped vertical cross section. The base of the speaker horn 22 is
inserted into the yoke 32 having the permanent magnet 3o, and the cylindrical base 22b of the
diaphragm 22 is inserted between the magnetic paths 34 of the yoke. It is done.
Then, when an audio current flows to the audio coil 36 mounted on the cylindrical base 22b,
interference occurs with the magnetic field between the magnetic paths 34 to generate a force to
move the audio coil 36, thereby vibrating the diaphragm 22. Sound is generated. At this time, the
sound pressure sensor 38 attached by a support member (not shown) substantially in front of the
center of the diaphragm 22 converts the sound generated from the speaker into a voltage. FIG. 3
is an equivalent circuit diagram showing the sound reproducing apparatus of the present
invention in which the same parts as those in FIG. 1 are denoted by the same reference numerals
using the speaker having the configuration shown in FIG. In FIG. 3, the output end of the sound
pressure sensor 38 is connected via the feedback resistor 180 to the connection point P of the
feedback resistors 18a and 181) or to the negative input end of the amplifier 12. The circuit
representing the sound reproducing apparatus of the present invention has the above-described
configuration, and the operation thereof will be described below. Now, the resistance values of
feedback resistors 18a, 18b and 18C are Ra, Rb and Rc, the gain of amplifier 12 is A1 sound
pressure conversion efficiency of sound pressure sensor 38, B1 speaker impedance is RL,
amplifier input voltage is vl, speaker generation Assuming that the sound pressure is P and the
speaker sound pressure conversion efficiency is C (ω), the speaker generated sound pressure P
is P = C (ω) □ 11 + Rb / (Ra + Rb) A in the case of the conventional configuration of FIG. It can
be expressed. Here, since the speaker sound pressure conversion efficiency C (ω) is a function of
the frequency ω, the speaker generated sound pressure P was not necessarily in proportion to
the amplifier input voltage v1. However, in the configuration of the present invention shown in
FIG. 3, the equation (1) is obtained, and the right side of the equation (2) has C (ω) in the
denominator and numerator. By largely selecting it, it becomes an approximation, the frequency
dependency of the speaker sound pressure conversion efficiency C (ω) disappears, and the
characteristic is improved so that the speaker generated sound pressure P becomes a size
proportional to the amplifier input voltage V1. . Although the sound pressure sensor 38 is
provided in front of the diaphragm 12 in the above embodiment, a sound pressure sensor such
as an accelerometer may be provided on the diaphragm 12. As described above, according to the
present invention, the sound pressure sensor is provided in front of the diaphragm and the
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branch diaphragm, and the output signal of the sound pressure sensor is fed back to the input
side of the amplifier for amplifying the audio current. The effect of reducing the frequency
dependency of the speaker and improving the distortion and frequency characteristics of the
amplifier can be obtained. 1,
[0002]
Brief description of the drawings
[0003]
FIG. 1 is an equivalent circuit diagram showing a conventional sound reproducing apparatus, FIG.
2 is a very schematic cross-sectional view showing the structure of a speaker applied to the
sound reproducing apparatus of the present invention, and FIG. 3 shows the sound reproducing
apparatus of the present invention. It is an equivalent circuit schematic.
In the drawings, the same members are denoted by the same reference numerals, 10 is a signal
input terminal, 12 is an amplifier, 14 is a speaker, 16 is a ground, 18a-18b-18 (! Is a feedback
resistor, 20 is a speaker horn, 22 is a diaphragm, 24 is a baffle plate, 26 is an aperture, 28 is a
screw, 30 is a permanent magnet, 32 is a yoke, 34 is a magnetic path, 36 is a voice coil, 38 is a
sound It is a pressure sensor. Agent Patent Attorney Shino Nono-(Other 1 person) Fig. 1 Fig. 3
Fig. 26
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