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JPS63193698

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DESCRIPTION JPS63193698
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
motional feedback type speaker system which detects movement of a diaphragm of a speaker
and converts it into an electric signal and feeds this signal back to an amplifier for driving the
speaker. [Background Art] There is known a speaker apparatus using a motional feedback
(hereinafter abbreviated as MFB) system to improve the characteristics of the speaker in the low
frequency range. This has various advantages such as distortion is reduced by feeding back the
signal from the speaker to the amplifier as well known. FIG. 4 (a) is a side cross-sectional view of
the conventional speaker system shown in, for example, Japanese Utility Model Publication No.
60-25194, and FIG. 4 (b) is a configuration diagram of its feedback system. In the figure, (1) is a
speaker box as a speaker housing, f2), (31 is a high sound and low sound speaker attached to the
front baffle (4) of the speaker box (1), (5) Is an amplifier for driving the bass speaker (3), 翰 is a
frame attached to the front of the speaker box (1), 0 is a net attached to the frame, (2) is a net Q
υ The acoustoelectric converter attached at a position corresponding to the front substantially
central portion of the above-mentioned bass speaker (3), @ is a lead wire having one end
connected to the acoustoelectric converter (c). 34, (c) are provided at the upper and lower
portions of the above-mentioned frame ■. The plug is a plug for attaching the frame rod to the
speaker box (1). Among them, the other end of the lead wire (c) is connected to the plug CI4. (C),
(5) are jacks provided at the upper and lower portions of the above speaker box (11, to which the
above plug, + 249 are connected). One end is connected to this jack, and the other end is covered
by the net in the front of the spies (2) and (3), and the acoustoelectric converter (company) is a
speaker for bass It will be installed at the front of the center of (3). Furthermore, since the plug
and jack simultaneously serve as mechanical connection and electrical connection, the electric
signal generated in the acoustoelectric converter @ by the sound radiated from the bass speaker
(3) Is. It is fed back to the amplifier (5) through the lead (c), the plug C14, the jack (d) and the
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lead (d) to form a feedback loop. Therefore, distortion of the bass speaker (3) can be reduced.
[Problems to be Solved by the Invention] Since the present invention is configured as on the
conventional MFB-type loudspeaker speaker system, the acoustoelectric converter for converting
sound into an electric signal takes noise other than the sound from the speaker. In addition, it
may cause a phase difference in the feedback signal due to the distance from the speaker.
There is a problem that the feedback system can not be obtained because it can not obtain a
feedback signal that faithfully detects the moving state of the diaphragm. The present invention
has been made to solve the above-mentioned problems, and its object is to present a highperformance MFB-type loudspeaker speaker system by obtaining a faithful feedback signal
without being influenced by external noise. [Means for Solving the Problems] A displacement
detection means for outputting an electric signal according to the vibration displacement by
optically detecting the vibration displacement of the diaphragm of the MFB type loudspeaker
speaker system speaker according to the present invention The electric signal is fed back to the
amplifier. [Operation] In the present invention, the displacement detection means optically
detects the vibration displacement of the diaphragm, outputs an electric signal according to this,
and this signal is fed back to the amplifier to form a feedback loop, and the speaker The low
frequency characteristics of the system are improved. FIG. 1 (a) is a perspective view of a speaker
system according to an embodiment of the present invention, FIG. 1 (b) is a side sectional view
thereof, and (1) to (4) are the prior art examples described above It is similar. (6) optically detects
the vibration displacement of the low frequency speaker (3). A displacement detector that emits
an electrical signal, (7) is a lead that feeds this electrical signal back to the amplifier, and (8) is a
DC power supply. Fig. 2 enlarges the vicinity of this displacement detector (6). FIG. 3 is an overall
block diagram of this embodiment, FIG. 3 is a reed of the embodiment, (9) is a diaphragm of the
bass speaker (3), tll is the loudspeaker (3). Or a support appropriately provided in the speaker
box (1). αυ is a light emitting diode which is provided on the support Ql and emits light toward
the diaphragm (9), and has a lens @ for narrowing the light so that the light hitting the imaging
plate 19) is spot-shaped . a3 is a drive circuit for driving the light emitting diode C1. A light
receiving lens which converges a part of the light from the light emitting diode αυ irregularly
reflected by the diaphragm (9) into a spot shape. 1L! A photoelectric conversion element 9 is
fixed in the support Q1 and receives the light converged by the light receiving lens Q4 and emits
an electric signal according to the position where the light hits, and u8 is an electric signal from
the photoelectric conversion element (c). It is an amplification circuit which current amplifies a
signal. A current voltage amplifier 0 converts a current signal from the amplification circuit 1J19
into a voltage, and a comparator H uses a feedback signal from the current voltage amplifier αη
to the input of the amplifier (5).
Next, the operation will be described. When the light emitting diode αυ is driven by the drive
circuit α 謙 and turned on, the light is converged by the lens U) and irradiated to the diaphragm
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(9) in a spot shape. This light is diffusely reflected by the diaphragm (9) so as to be diffused, but
the reflected light incident on the light receiving lens a4 is converged here, and a part of the
photoelectric conversion element ae is irradiated in a spot shape. Be done. This light is converted
into an electrical signal according to the irradiated position in the photoelectric conversion
element and output. Here, as can be seen from FIG. 2, the photoelectric conversion element U!
The spot-like light irradiated to 9 changes the irradiation position according to the position of the
diaphragm (9). For example, when the diaphragm (9) is stopped (solid line), light irregularly
reflected light that enters the light receiving lens + 141 and converges has an optical path as
shown by a solid arrow in the figure. 9. At a certain moment (dotted line) of the speaker (3) when
the drive diaphragm (9) is displaced, light entering the light receiving lens has an optical path as
shown by a dotted arrow in the figure. In each case, the incident angle of light to the light
receiving lens I is different, so the irradiation position of light on the photoelectric conversion
element housing is also different. Therefore, the electric signal output from the photoelectric
conversion element μ field corresponds to the vibration displacement of the diaphragm (9). This
electrical signal is current amplified in the amplifier circuit tank. It is converted into a voltage
signal by the current voltage amplifier αD, and is input to the comparator α barrel as a
feedback signal. Therefore, feedback looseness is realized to improve low frequency
characteristics. In addition, since the vibration displacement of the diaphragm (9) is optically
detected, it is not affected by external noise, and good performance can be obtained. In the above
embodiment, although the displacement detector (6) is attached to the outside, the vibration
displacement of the diaphragm (9) can be detected on the back side even if it is provided in the
speaker box (1) It produces the same effect as the example. In the present invention, since the
displacement detector does not have to be disposed at the center of the front face of the speaker
(3), there are few structural restrictions. In particular, when the displacement detector (6) is
provided in the speaker box (1) as described above, the appearance does not deteriorate. As
described above, according to the present invention, the displacement detection means for
optically detecting the vibration displacement of the diaphragm of the speaker and outputting an
electric signal is provided, and this electric signal is fed back. Therefore, a feedback signal which
is not affected by external noise and does not cause one phase difference can be obtained, and
there is an effect that an MFB type loudspeaker speaker system with good performance can be
realized.
[0002]
Brief description of the drawings
[0003]
1 (a) is a perspective view of a speaker system according to an embodiment of the present
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invention, FIG. 1 (b) is a side sectional view thereof, and FIG. 2 is an enlarged view of the vicinity
of a displacement detector in FIG. 1 (b). FIG. 3 is a block diagram showing the electric system in
this embodiment, and FIG. 4 (aJ is a side sectional view of the conventional motional feedback
type speaker system.
FIG. 4 (b) is the electrical system diagram. In the figure, (1) is a speaker box, (3) is a bass speaker,
(5) is an amplifier, (6) is a displacement detector, (9) is a diaphragm r ul is a support, aυ is a
light emitting diode, tla Is a lens, α 謙 is a drive circuit, u4) is a light receiving lens, US is a
photoelectric conversion element, αQ is an amplifier circuit, and a is a current voltage amplifier.
Alpha barrel indicates a comparator. The same reference numerals in the two drawings indicate
the same or corresponding parts.
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