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JPS6087598

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DESCRIPTION JPS6087598
[0001]
TECHNICAL FIELD The present invention relates to a speaker device aiming to control the sound
pressure characteristic of a speaker by motional feedback (hereinafter referred to as MFB) and to
lower the lowest resonance frequency (hereinafter referred to as fo). It is. The configuration of
the prior art and the problems thereof The MFB in the speaker detects the vibration of the
speaker 13 by some method as shown in FIG. 1 and FIG. 2, and the negative feedback to the
power amplifier 12 on the input side through the feedback circuit 14 It is well known that it is
possible to reduce the fo of the speaker 13 by feeding back a signal proportional to the
acceleration of the diaphragm 7 of the speaker 13. FIG. 1 shows such a conventional MFB
speaker, in which the micro port 7 'is fixed by an IJ fixed pin IJ tag 7' to detect the reproduced
sound pressure. It is fixed on the radiation 11111. In FIG. 1, 1 is a yoke, 2 is a mug kit, 3 is a
plate, 4 is a frame, 5 is a voice coil, 6 is a damper, 7 is a diaphragm, and 1o is an edge. In this
way, it is possible to detect the sound pressure in proportion to the acceleration of the speaker
without contacting the vibrating portion of the speaker 13. However, in the case where the
diaphragm 7 of the speaker is a cone type as shown in FIG. 1, the vibration mode of each portion
of the cone is nonuniform, and the split resonance occurs at the place or place. The distortion
factor of the recomposition in the vicinity of the diaphragm 7 and the distortion factor at the
distant name hot water as the listening point do not match. This situation was actually measured
in Fig. 3 and Fig. 4. The horizontal axis represents the distance between the speaker 13 and the
microphone 11, and the vertical axis represents the distortion factor when the fundamental wave
is O dB. ing. 3 and 4 respectively show FIG. The third harmonic distortion is exhibited, and the
distortion factor clearly does not match in the vicinity of the diaphragm and in the distance. This
is because the wave front of radiation-11 from each part of the diaphragm is not uniform as
described above, and distortion phase sweating is generated, and the divided resonance of the
diaphragm is generated This is because the magnitude and phase of the distortion itself are not
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uniform in each portion of the diaphragm. Therefore, when the microphone 11 is fed back in the
vicinity of the diaphragm 7, the distortion in the vicinity of the diaphragm 7 is reduced, but there
is a problem that the frequency is not reduced at the listening point and conversely deteriorates.
Also, in order to apply negative feedback, the frequency of the feedback signal is limited to a
range of frequencies lower than the frequency at which the distance between the speaker 13 and
the microphone 11 is% wavelength, so if the microphone 11 is moved away to the listening point,
the listening point However, the upper limit frequency of the feedback is very low.
SUMMARY OF THE INVENTION The present invention solves such a problem and provides a
speaker device which detects the vibration without contact with a speaker, improves distortion at
a listening point, and reduces fo of the speaker. According to the present invention, in a speaker
apparatus using a flat diaphragm in which distortion of reproduced sound coincides with the
vicinity of the diaphragm and the listening point, the reproduced sound is detected by the
electroacoustic transducer in the vicinity of the diaphragm to It is something which is made to
return to the input side. In this way, it is possible to feed back to the speaker without attaching a
detector to the vibration system as in the prior art, thereby reducing distortion of the reproduced
sound, including the listening point, and also reducing the io of the speaker. it can. DESCRIPTION
OF THE PREFERRED EMBODIMENT FIG. 5 shows an embodiment of the present invention, in
which the speaker 19 and the nondirectional microphone (electro-acoustic transducer) 11 are
provided on the baffle 16 of the speaker box 15, and the detection signal of the microphone 11
is feedback circuit. The signal is applied to the inverting input of the power amplifier 12 through
the reference numeral 14 to cause the speaker 19 to be negatively fed back. 6 is a sectional view
of the speaker 19. 1 is a yoke, 2 is a magnet, 3 is a plate, 4 is a frame, 6 is a voice coil, 6 is a
damper, 7 is a flat diaphragm, 10 is an edge, 11 is all (all The directional microphone 16 is
baffled. Since the microphone 11 is omnidirectional in this way and the radiation sound of the
speaker 19 is also omnidirectional in the low frequency region, if the distortion factor is the same
as the vicinity of the diaphragm, the microphone 11 is detected If the distortion of the signal is
reduced in proportion to the feedback amount, the distortion at the listening point is also
reduced. As shown in FIG. 6, when the diaphragm 17 has a honeycomb sand-inch structure and is
driven by a drive cone 18 so as to be driven by the drive cone 18, the rigidity of the diaphragm is
high, and the piston motion region is wider than that of the conventional diaphragm. It is well
known that the resonance frequency is high, so the so-called divided vibration is not in the used
frequency band, so the distortion attributed to the divided vibration is small, and the distortion
attributed to the driving unit and the support system is mostly. Therefore, since the diaphragm
17 itself is rigid and the radiation sound is uniform, the sound field and distortion in the vicinity
of the listening point of the hessian force and the diaphragm are uniform compared to the
conventional cone-type diaphragm, and the feedback amount The distortion of the listening point
can be improved in proportion to As is apparent from FIG. 6, the diaphragm 17 of the speaker 19
and the diaphragm of the microphone 11 are provided at the same position in the radiation axis
direction of the sound wave, and 11? Since the distance of the resonance center is sufficiently
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short compared to the wavelength, it can be considered that the wavefront on the diaphragm of
the microphone 11 and the wavefront on the diaphragm 17 of the speaker 19 are the same and
there is no phase difference.
That is, in a low frequency range where the wavelength is long and a plane wave is considered, it
can be considered that there is no time delay between the wavefront on the microphone 11 and
the wavefront on the speaker 19. For this reason, as in the conventional case where the
microphone is fixed by using an angle on the front surface of the diaphragm, the detection signal
of the microphone and the input signal of the speaker 11. There is no problem of delay between
+1 '. In addition, the conventional b4 microbon fixing angle disturbs the radiation of sound, and
the angle is resonated, and the restriction on the membrane can be solved as well as the design is
not excellent. Also, when using a flat diaphragm speaker as described above, the distortion of the
radiated sound is the same near and far from the speaker, so it is not necessary for the microbon
to be able to have several phrases in the speaker frame near the speaker. Instead, an independent
cabinet separated from the speaker can be provided with an adapter incorporating a feedback
circuit and a microphone, and feedback can be given to the speaker at a position away from the
speaker. However, it goes without saying that in this case, the distance between the speaker and
the microphone needs to be within the range not exceeding K of the wavelength of the frequency
at which the feedback is O dB. FIGS. 7 and 8 show the distance versus distortion characteristics
of a loudspeaker using the flat diaphragm according to the present invention, showing second
and third harmonic distortions, respectively, and the horizontal axis represents the loudspeaker
19 and the like. The distance of the microphone 11 and the distortion factor on the vertical axis
are respectively scaled by logarithms. As apparent from this, the distortion factor in the vicinity
of the diaphragm and in the distance is constant. Father In the above embodiment, a flat
diaphragm was shown, but as shown in FIG. 9, the back side of the diaphragm 20 may be in a Qshaped form. That is, if the radiation direction surface 20a of the reproduction sound of the
speaker is a flat surface, the wavefront from each part of the diaphragm is uniform, so distortion
from each part does not occur in phase. Also, it is well known that the so-called acceleration
feedback or the decrease of 5fo decreases because the sound pressure is proportional to the
acceleration when the sound pressure of the speaker is returned as it is. Also, it is possible to
integrate the output signal of the microphone and apply velocity feedback and amplitude
feedback to IJJ et al. Furthermore, it can be used as another control signal such as feed-thruing
that the listening point and detection point coincide Naturally from. Effects of the Invention As
described above, according to the present invention, by making the diaphragm of the speaker
flat, acoustic feedback is realized using the microphone, and improvement of the linearity of the
speaker, which is an advantage of the MFB! A drop of 0 can be realized with a simple
configuration without having to touch the speaker unit. The 1-microphone does not have to be
integrated with the speaker unit, and can be assembled into a baffle or integrated into an adapter
separate from the speaker The present invention can be applied to a speaker used by Corp all at
once, and when the application is included, the degree of freedom for the film is extremely large
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and an excellent effect such as a simple configuration can be obtained.
[0002]
Brief description of the drawings
[0003]
1 and 2 are a sectional view and a block diagram of a conventional speaker device, and FIGS. 3
and 4 are distance versus distortion characteristics of the conventional speaker, and FIGS. 5 and
6 are the present invention. FIG. 7 is a block diagram and a sectional view of an embodiment of
the speaker apparatus of FIG. 7, FIG. 7 and FIG. 8 are distance vs. distortion factor characteristics
of the speaker apparatus in an embodiment of the present invention, and FIG. It is sectional
drawing of an Example.
-Gt, 4 ... frame, 5 ... voice coil, 6 ... damper, 7 ... cone-shaped diaphragm, 8 ... dust cap, 9 ........
Circuit 15 15 Speaker unit 16 Bauffle 17 Flat diaphragm 18 Drive cone 19 Speaker 0 agent
Name of Patent Attorney Nakao Toshio and 1 other person Fig. 5 + q Fig. 6 Fig. 6 Fig. 7 My 711.
Small N 'Jpi% nnm) Figure 9
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