Electrical audio signal processing systems and devices – Including frequency control – Having crossover filter
Reexamination Certificate
2002-06-10
2004-10-12
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
Including frequency control
Having crossover filter
C381S097000, C381S061000, C381S307000
Reexamination Certificate
active
06804361
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sound signal playback machine and method thereof for playing back multichannel sounds.
2. Description of the Related Art
Concerning the sound signal playback machine for playing back multichannel sounds, for example, a sound signal playback machine to realize 5.1 surround playback is well known.
FIG. 10
is a block diagram showing an example of such a sound signal playback machine. In
FIG. 10
, the signal input terminal
101
, to which sound signal S
L
of L-channel (left channel) is supplied, is connected to the speaker
131
, which is arranged at the front on the left, via HPF (high-pass filter)
111
and the amplifier
121
. At the same time, the signal input terminal
101
is connected to the signal adder
151
via LPF (low-pass filter)
141
. The signal input terminal
102
, to which sound signal S
R
of R-channel (right channel) is supplied, is connected to the speaker
132
, which is arranged at the front on the right, via HPF
112
and the amplifier
122
. At the same time, the signal input terminal
102
is connected to the signal adder
151
via LPF
142
. The signal input terminal
103
, to which sound signal S
SL
of SL-channel (surround left channel) is supplied, is connected to the speaker
133
, which is arranged at the rear on the left, via HPF
113
and the amplifier
123
. At the same time, the signal input terminal
103
is connected to the signal adder
151
via LPF
143
. The signal input terminal
104
, to which sound signal S
SR
of SR-channel (surround right channel) is supplied, is connected to the speaker
134
, which is arranged at the rear on the right, via HPF
114
and the amplifier
124
. At the same time, the signal input terminal
104
is connected to the signal adder
151
via LPF
144
. Further, the signal input terminal
105
, to which sound signal S
C
of C channel (central channel) is supplied, is connected to the speaker
135
, which is arranged at the front center, via HPF
115
and the amplifier
125
. At the same time, the signal input terminal
105
is connected to the signal adder
151
via LPF
145
. On the other hand, the signal input terminal
106
, to which sound signal S
LFE
of LFE channel (channel exclusively used for the low frequency band) is supplied, is connected to the signal adder
152
to which the above signal adder
151
is connected. This signal adder
152
is connected to the speaker
136
, which is arranged on the side, via the amplifier
126
. In this case, the speakers
131
to
135
respectively compose a speaker system for playing back sounds of middle low frequency and higher frequency than that. In general, they are referred to as a satellite speaker system. The speaker
136
is a speaker system for playing back sounds of low frequency. In general, the speaker
136
is referred to as a sub-woofer.
In this connection, the above conventional sound signal playback machine is designed so that the frequency response can be flat when signals on the low frequency side and those on the high frequency side are electrically synthesized with each other. Further, in the above conventional sound signal playback machine, it is necessary to use a filter of the high order so that the band width, in which the frequency response on the low frequency side and that on the high frequency side cross each other, can be reduced. Accordingly, the following problems may be encountered. The frequency response of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, are flat as shown in
FIG. 11
, however, as shown in
FIG. 12
, a group delay in the low frequency band is increased, which causes such a problem that sounds of low frequency can not be faithfully played back and further a nuance of sounds of a musical instrument of low frequency is changed. In the case where sound signal S
LFE
of channel LFE and sound signals S
L
to S
C
of the other channels (main channels) are correlated with each other, a group delay is increased in the low frequency band when sound signal S
LFE
in channel LFE is added.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above circumstances. It is an object of the present invention to provide a sound signal playback machine and method thereof capable of making a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are synthesized with each other, flat so that sounds of low frequency can be faithfully played back and a nuance of sounds of a musical instrument of low frequency can be improved.
In order to accomplish the above object, first, the present invention provides a sound signal playback machine comprising: a high frequency pass filter for extracting a predetermined high frequency component from a sound signal in a main channel; a first speaker for playing back the high frequency component extracted by the high frequency pass filter; a low frequency pass filter for extracting a predetermined low frequency component from the sound signal in the main channel; a signal adder for outputting an addition signal in which the low frequency component extracted by the low frequency pass filter is added to a sound signal in a channel exclusively used for a low frequency band; and a second speaker for playing back the addition signal outputted from the signal adder, wherein the degree of the low frequency pass filter is set higher than that of the high frequency pass filter, the sound signal playback machine further comprising a phase matching means for matching the phase of the high frequency component extracted by the high frequency pass filter with the phase of the low frequency component extracted by the low frequency pass filter. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Secondly, the present invention provides a sound signal playback machine according to the above item 1, wherein the phase matching means is a delay circuit for delaying the high frequency component extracted by the high frequency pass filter. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Thirdly, the present invention provides a sound signal playback machine according to the above item 2, wherein delay time T1 (sec) of the delay circuit is set at a value calculated by the equation of
T
1=(&phgr;1−&phgr;2
+&pgr;·n
)/(2
&pgr;Fc
)
(n=. . . −2, −1, 0, 1, 2 . . . )
where &phgr;1 (rad) is a phase angle at a cut-off frequency Fc (Hz) of the high frequency pass filter, and &phgr;2 (rad) is a phase angle of the low frequency pass filter. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Fourthly, the present invention provides a sound signal playback machine according to the above item 1, wherein the phase matching means is to set the first speaker by moving it in a direction so that the first speaker can be separated from a listener. According to the sound signal playback machine composed as described above, it is possible to make a group delay characteristic of signals, which are obtained when signals on the low frequency side and signals on the high frequency side are electrically synthesized with each other, substantially flat.
Fifthly, the present
Hamada Hiroyuki
Hosoi Shintaro
Grier Laura A.
Mei Xu
Pioneer Corporation
Sughrue & Mion, PLLC
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