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JPH02249398

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DESCRIPTION JPH02249398
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
improvement of a speaker system in which speakers are attached to two baffle boards on the
front and rear sides, respectively. 2. Description of the Related Art A conventional speaker system
of this type is shown in FIG. 6, where SP denotes the front speaker and SP denotes the rear
speaker, and the distance to the listener MIC is Ill and it, respectively. The individual sound
pressure frequency characteristics of the speakers SP, SP are as shown by the dotted line in FIG.
Since the phase difference δ is small in a sufficiently low tone range where the wavelength of
the sound from the speakers sp and SP is h−1, the two sound waves are considered to be in
phase and the combined sound pressure is Is the fd (j! In FIG. 7). If the length of z l + is less than
the half wavelength (the wavelength), it rises. However, at the frequency fd where the frequency
becomes high and the phase difference .delta.-180 degrees, the two are in opposite phase to
cause a dip in the sound pressure frequency characteristic. Furthermore, at the frequency fp
where the frequency becomes higher and the phase difference δ = 360 degrees, both are
synthesized again in the same phase, and the sound pressure makes a round. Thus, as the
frequency rises, the day knob and the peak are repeated, and the sound pressure frequency
characteristic becomes as shown by the solid line in FIG. Conventionally, two methods have been
taken as shown in FIGS. 8 and 11 in order to eliminate such a defect. FIG. 8 is intended to supply
signals to two speakers SP, SP through a low pass filter LPF and operate at a frequency fd or less.
The phase of the speaker SP in this case is indicated by a dotted line, and the phase of the
speaker SPz is indicated by an alternate long and short dash line in FIG. 9, and the synthesized
sound pressure frequency characteristic is indicated by a solid line in FIG. The dotted line in FIG.
10 is a single sound pressure frequency characteristic of the speaker SP +. As apparent from FIG.
10, the reproduction frequency of this speaker device is fd or less, which is not consistent with
the purpose of reproduction up to about IKtlz. FIG. 11 is for supplying a signal to the speaker SP
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through a low pass filter LPF that cuts high frequency at frequencies higher than fd. FIG. 12
shows the phases of the two loudspeakers SP and SP2 in this case by dotted lines and dotted
lines similar to FIG. As a result, the sound pressure frequency characteristic synthesized as
shown in FIG. 13 is shown, and the dotted line in FIG. 13 shows the sound pressure frequency
characteristic of the speaker SP + only, and the dotted line shows the sound pressure frequency
characteristic of the speaker SPz. . Also in this method, as shown in FIG. 13, there is a drawback
that the high frequency of the reproduction frequency is lowered when the dip and peak of the
sound pressure frequency characteristic are reduced.
SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of
this type of speaker device, corrects the phase difference caused by the distance difference by
the electric phase difference of the dividing filter, and has a sound pressure frequency
characteristic without dips and peaks. It is an object of the present invention to provide a speaker
device capable of reproducing to relatively high frequencies. [Summary of the Invention] The
present invention relates to a means of a speaker device for achieving the above-mentioned
object, in which a speaker mounted on a panful port on the front and rear faces has a phase
difference of 180 degrees due to the difference in distance between both speakers. , The cutoff
frequency is supplied through divided filters having different cutoff characteristics of the filter.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present
invention will be described below with reference to FIGS. The low-pass filter LPF connected to the
front speaker SP is a cutoff frequency fc near the frequency fd where the phase difference
corresponding to the distance difference from the rear speaker SP2 is 180 degrees, and its
attenuation characteristic is 1 6 dB 10 ut , -12 dB10 ut may be used according to the need. The
low-pass filter LPF connected to the rear surface speaker SP is set to a frequency [C2, ie, f C = ') r
C 1, which is near the frequency fd and higher than the cutoff frequency fC1 of the low-pass
filter LPF. . The attenuation characteristic has a gentler slope than that of the low pass filter LPF,
and the frequency fc has a steeper slope near the frequency fc. このようなローパスフィルタ
LPF、、LPF。 Transmission characteristics and phase characteristics of FIG. 2, both
speakers SP + -3P! The phase difference due to the difference in distance is shown in FIG. In the
figure, assuming that the front speaker SP has a phase of ψ at the frequency fct, the front
speaker SP has a phase of ψ2 at the frequency fc of the rear speaker SP z. Also, both speakers SP
at this frequency fc. The low-pass filters LPF and LPFg are designed such that ψ1- (ψ2 + ψ) = 0
if the phase difference due to the distance difference of SPz is ψ3. Then, the phase of the sound
wave of the rear speaker SP2 can be made to be the same with respect to the delayed phase of
the sound wave of the front speaker SP, so that the frequency characteristic of the synthetic
sound pressure dip, peak Can be significantly reduced. As an example of such a speaker device, a
low-pass filter is set as a crossover frequency fc = 600 Hz with loudspeakers sp,. LPF.
An example of the LPF is shown in FIG. At this time, L + = 8 mm HC, = 50 μ FL 2 = 3 cylinders l
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(C, = 20 μ F). At this time, the frequency characteristics of the front speakers SP are dotted lines
in FIG. 5 and those of the speakers SP on the rear surface are alternate long and short dashed
lines, and the synthesized sound pressure frequency characteristics are indicated by solid lines.
In this embodiment, two speakers SP, SP. However, even in the case of three or more speakers, it
can be implemented in the same manner. According to the present invention, as described above,
when two or more speakers having different front and rear sound source positions operate
simultaneously in at least a part of the reproduction band, the phase difference due to the
distance difference is respectively By compensating for the phase difference generated by the
divided filter connected to the speaker of the above, and making it the same phase, it is possible
to reduce the dip and peak that occur in the sound pressure frequency characteristic.
Accordingly, the sound pressure frequency characteristics can be made to be flatter, and a
speaker device with good sound quality can be obtained.
[0002]
Brief description of the drawings
[0003]
1 is a block diagram of an embodiment of the present invention, FIG. 2 is a transmission
characteristic and a phase characteristic diagram of each speaker by a low pass filter, FIG. 3 is a
phase difference diagram due to a distance difference between both speakers, and FIG. FIG. 5 is a
circuit diagram of the embodiment, FIG. 5 is a sound pressure frequency characteristic diagram
according to FIG. 4, FIG. 6, FIG. 8 and FIG. 11 are block diagrams of conventional speaker
devices, FIG. The figure is a sound pressure frequency characteristic diagram, and FIGS. 9 and 12
are phase characteristic diagrams of the respective speakers.
LPF、、LPF、・・・ローパスフィルタ、SP。、SP2・・・スピーカ。 First cause
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