JVC RC-828L Service Manual page 3

| RC-828L/LB
Technical Information
BIPHONIC SYSTEM
The BIPHONIC system is the new method of acoustical To decrease the reflected signals, set the speaker systems
reproduction developed by JVC. in a dead room or change the location of speaker
The BIPHONIC means that the BINAURAL program is systems.
reproduced stereophonically through the speaker systems. To cancell the crosstalk b, the signal! -b which is the same
1. BINAURAL SYSTEM level as the crosstalk b at the position of right ear and is
The BINAURAL system is to reproduce programs
recorded by two microphones which are located at the
both ear positions of artificial head acoustically
simulates ahuman head. 'The direction and distance of
sound sources can be distinguished when listening to the
binaural recorded programs through headphones. The
human distinguishes the direction and distance of sound
sources by level difference and time lag of sounds which
propagate to both ears.
Sound Source
: Sy 2%
~
Ear-lap Ear-lap
Fig. 1
The most important thing is that the binaural programs
should be reproduced through the headphones, that is,
the left channel sounds should be heard by left ear and
right sound by right ear.
2. BIPHONIC PROCESSOR
The newly developed BIPHONIC system can reproduce
the binaural programs through the speaker systems.
There exists unwanted signals, when reproducing the
binaural programs through the speaker systems, cross-
talk b and reflected signal c as shown in Fig. 2.
Artificial Head
Ls Rs
Biphonic Processor
"Ta Re
Fig. 2
To improve the binaural effect the crosstalk should be
acoustically cancelled and the reflected signals should
be decreased.
the reverse phase should be emitted from the right
speaker. The new circuitry ''BIPHONIC PROCESSOR"
has been developed by JVC to cancell the crosstalk and
to reproduce the binaural programs through the speaker
systems.
The model RC-828 is equipped with the IC (Integrated
Circuit) of BIPHONIC PROCESSOR.
The block diagram of BIPHONIC PROCESSOR is shown
in Fig. 3.
Fig. 3
Part of signals are added to the opposite channel! through
the equalizer and delay circuit to cancell the crosstalk.
As the level and phase of crosstalk is varied by distance
from the speaker, the listening position at where the
binaural effect is normally obtained is limited.
The optimum listening position of model RC-828 is set
between 60 to 80cm from the speakers.
. EXPANDED PLAYBACK
The BIPHONIC system can expand the sound field of
2-channel stereophonic programs.
Generally, in the 2-channel stereo systems, the sound
field exists between left and right speaker systems.
The sound field expands to the outside area of speaker
systems when the 2-channel stereo programs are
reproduced through the BIPHONIC PROCESSOR.
This effect is named "EXPANDED PLAYBACK".
(St
2-Channel Stereo
Biphonic Processor
Fig. 4
The BIPHONIC PROCESSOR also widens the sound
field of 2-channel stereo programs in listening through
the headphones, this is named "STEREO WIDE PLAY-
BACK".
No. 1344