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DESCRIPTION JPH08307987

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DESCRIPTION JPH08307987
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker drive circuit, and more particularly to a speaker drive circuit of a compact speaker
system.
[0002]
2. Description of the Related Art In a small speaker system, miniaturization is achieved, for
example, by reducing the size of the speaker box using one wide-band speaker. Therefore, the socalled baffle plate is also small, and the level of the bass region is reduced due to the reduction of
the baffle effect, that is, the midrange is raised. Therefore, in order to obtain flat frequency
characteristics over the entire band, for example, it is necessary to round the corners of the
rectangular baffle plate so as not to make the sound wave interference between the front and
back of the speaker clear. In the plastic speaker box. It is easy to round the corners, but with
wooden speaker boxes, there is the problem of increased cost due to the difficulty of processing.
[0003]
By the way, when a tubular one is provided on the front of the speaker, a so-called dent effect is
known in which the midrange is raised. Therefore, in a small speaker system, it may be possible
to prevent the midrange from rising by attaching the speaker on the front side of the baffle plate,
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but the so-called grille net provided on the front of the speaker can be removed, Attaching the
speaker to the front side of the baffle plate increases the cost.
[0004]
As described above, in the conventional small speaker system, it is difficult to prevent the
midrange from rising without increasing the cost.
[0005]
The present invention has been made in view of the above-described circumstances, and it is an
object of the present invention to provide a speaker drive circuit capable of preventing the rise of
the midrange without much cost, for example, in a small speaker system. Do.
[0006]
A speaker drive circuit according to the present invention comprises a drive circuit for driving a
speaker, and a band attenuation filter provided between the drive circuit and the speaker.
[0007]
The band attenuation filter attenuates the mid-range component of the speaker drive current
from the drive circuit and supplies it to the speaker.
[0008]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a speaker drive
circuit according to the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a specific circuit configuration of a speaker drive circuit to which the
present invention is applied.
[0009]
As shown in FIG. 1, the speaker drive circuit to which the present invention is applied amplifies a
signal from the signal source 11 to drive the speaker 13, and between the constant voltage
amplifier 12 and the speaker 13. And a band attenuation filter 20 provided in
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[0010]
In this speaker drive circuit, the band attenuation filter 20 attenuates the mid-range component
of the speaker drive current amplified by the constant voltage amplifier 12 and supplies it to the
speaker 13, thereby causing a problem in the conventional small speaker system. It is designed
to prevent the upsurge of the midrange that has been done.
[0011]
Specifically, the constant voltage amplifier 12 amplifies a signal from the signal source 11 to
generate a speaker drive current, and supplies the speaker drive current to the band attenuation
filter 20.
[0012]
For example, as shown in FIG. 1 described above, the band-pass attenuation filter 20 includes a
capacitor 21 and a resistor 22 connected in series, and a coil 23 connected in parallel to these.
Then, the band attenuation filter 20 attenuates the speaker drive current from the constant
voltage amplifier 12 in the vicinity of the resonance frequency thereof and supplies it to the
speaker 13.
[0013]
For example, in a so-called bass reflex type speaker system using two speakers with a diameter of
65 mm as the speaker 13, the capacitance of the capacitor 21 is 10 μF, the resistance value of
the resistor 22 is 2.35 Ω, and the inductance of the coil 23 is 0 Assuming that .39 mH, for
example, as shown in FIG. 2, the input impedance of the band attenuation filter 20, that is, the
impedance of the band attenuation filter 20 and the speaker 13 is synthesized as compared with
the input impedance of the speaker 13 alone (indicated by a broken line). The impedance (shown
as a solid line) increases near 2 kHz.
As a result, the drive current supplied to the speaker 13 is attenuated at around 2 kHz, and the
band attenuation is compared with, for example, the frequency characteristic when the band
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attenuation filter 20 shown in FIG. For example, as shown in FIG. 4, the frequency characteristic
provided with the filter 20 is such that there is no swell in the midrange.
That is, by providing the band attenuation filter 20 between the constant voltage amplifier 12
and the speaker 13, it is possible to prevent the midrange from rising.
[0014]
By the way, in the above-mentioned FIG. 2, the frequency characteristic of the impedance at the
time of using the zone | band attenuation filter 20 which does not provide the resistance 22, ie,
only by the capacitor | condenser 21 and coil 23 which were connected in parallel, is shown with
the thin line.
As is apparent from FIG. 2, the resonant frequency can be adjusted by the values of the capacitor
21 and the coil 23, and so-called Q can be adjusted by the value of the resistor 22. Desired
attenuation characteristics can be obtained.
[0015]
Next, in a so-called closed speaker system using, for example, one speaker having a diameter of
90 mm as the speaker 13, the capacitance of the capacitor 21 constituting the band attenuation
filter 20 is 15 μF, and the resistance value of the resistor 22 is 2.35 Ω. Assuming that the
inductance of the coil 23 is 0.39 mH, for example, as shown in FIG. 5, the rise of the midrange
can be suppressed to some extent.
[0016]
The present invention is not limited to the above-described embodiment. For example, each value
of the capacitor 21, the resistor 22, and the coil 23 may be determined according to the
frequency characteristic of the speaker, the size of the speaker box, etc. The frequency
characteristic can be set to a value that achieves desired flatness.
Also, for example, the resistor 22 may be inserted in series with the coil 23.
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Also, for example, the resistor 22 may not be provided.
[0017]
The speaker drive circuit according to the present invention comprises an amplifier for driving
the speaker and a band attenuation filter provided between the amplifier and the speaker, and
the speaker amplified by the amplifier by the band attenuation filter By attenuating the midrange component of the drive current and supplying it to the speaker, it is possible to prevent the
mid-range swell that is noticeable in a small speaker system without much cost.
[0018]
Brief description of the drawings
[0019]
1 is a block diagram showing a specific circuit configuration of a speaker drive circuit to which
the present invention is applied.
[0020]
2 is a diagram showing the frequency characteristics of the input impedance of the band
attenuation filter constituting the speaker drive circuit.
[0021]
FIG. 3 is a diagram showing the frequency characteristics when using two speakers of 65 mm
diameter and without the band attenuation filter.
[0022]
4 is a diagram showing the frequency characteristics when using two speakers of 65 mm
aperture and the above-mentioned band attenuation filter.
[0023]
5 is a diagram showing a frequency characteristic when using a 90 mm diameter speaker and
providing the above-mentioned band attenuation filter.
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[0024]
Explanation of sign
[0025]
Reference Signs List 11 signal source 12 constant voltage amplifier 13 speaker 20 band
attenuation filter 21 capacitor 22 resistor 23 coil
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