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PIONEETI
MATRIX 4.CHANNEL
DECODER
There are
two
types
of matrix
4-channel systems,
the RM
(regular
matrix)
and
the
SQ
matrix.
Source
information
comes
directly from matrix
4-channel
records
now
available on the market
or indirectly
from FM
broadcasts
of
such records. As
these
methods
are
not compatible, two
decoders
must
be
added
to
obtain
4-channel
reproduction
which
exhibits the inherent features of
each.
Regular
Matrix
As
shown
in
the Fig.23,
signals
L,
and
R,
from
a matrix 4-channel record (or FM broadcast)
pass
through
phase
shifters and appear
as
four
separate
outputs. This figure
also shows
that the o portion
of
signal
R,
is
added
to
signal
L-' to
form front
Ieft
signal
Lu
and
that
the
o portion of signal
L,
is
added
to
signal
R,
to
form front right
signal
Ru.
The
0
portion
of
signal R.,.
with
phase
led 90'
(+jRr ) is
added
to
signal
L-, with
phase lagged
90'
(
-jlr )
to
form
rear
left
sigrrals
L* ,
while the
B
portion
of the
-jL,
signal
is
added
to
the +jRr
signal
to form
rear
right
signal
R*.
LF
(front left,
CH.
1):
Lr
+
eRr
RF
(frontright,
CH.
3):
Rr
+
ql-r
LR
(rear
left, CH.2\:
-jl,r
+
jBRr
RR
(rear
right,
CH.
4):
+jRr -jBLr
Using
this
approach, unnatural images are elimi-
nated and
at the
same
time
realism
is
effected.
Even
if
2-channel stereo records
(FM
broadcasts)
supply the source material, the resultant effect
is
an
improvement over
ordinary
2-channel
stereo
sound.
MATRIX
4.CHANNE
L
RECORD
(OR
FM
BROADCAST) REGULAR
MATRIX
DECODER
LF
/CH.
I
(Lr+aRr)
LA/CH.2
(
jL
r +jBRr
)
RF,/
CH.3
(Rr+aLr)
Ra/CH.4
(+iRr jBLr)
Fig.23
SQ
Matrix
As shown
in
the Fig.24,
signals
L,
and
R-'
from
an
SQ matrix record
(or FM
broadcast)
pass
through
phase
shifters and appear
as
four
separate
outputs. This figure shows
that
signal
L,
becomes
signal
Lu
(CH.
1)
and
that
signal
Rt
becomes
signal
R,
(CH. 3),
without
any
alteration.
A
phase
shifter
lags
the
phase
of
signal
L., by 90,'
after which the
lagged signal is added
to
signal
R..
Level
of
the resultant
signal is dropped bV
1l{2
+
0.7
and
phase
is inverted
to form CH.2
signal
L*.
In
the
same
manner, signal
L'
is
add'ed
to
signal
Rr
with
phase lagged
90". The
level
is
reduced
by Ll.r/-Tlo form
signal
Ro.
LF (CH.l):
Lr
RF (CH.3):
Rr
LR (CH.2):
+j0.7L,
- 0.7Rr
RR
(CH.4):
-j0.7Rr
+0.7Lr
Thus,
it
is
seen
that
separation
in
the
SQ
matrix
system
is
better than
that
in
the
regular matrix
system,
that
is, separation between
L.
and
R..
In
matrk
reproduction
of
2-channel records (FM
broadcasts),
front
(Lr.
,
Re
)
separation theoretic-
ally
becomes
infinite.
At
the
same
time, rear
signals
are
90'
out of
phase
to front (LF,
RF ),
resulting in
a
feeling
of
depth which
corresponds
to
a
large
hall.
LF
,/ CA.
t
(Lr)
LR,/CN.2
(
+io.7L;
o.?Rr)
RF
/CH.3
(Rr)
RRICH
4
(
-jo.7Rr+o.7Lr)
Fig.24
NOTE:
L7
and
R,
are
sigtwls
from
a
record
or
FM
broodcast. Term
-i
denotes
that
the
phase
of
the
signal has been lagged
9f
(with
a
phase
shifter),
while term
+j denotes
that
the
phase
of
the sigrwl
has
been
led
90".
SO
MATRIX
DECODER
PHASE
REVERSE
(180.)
FM
STEREO
TUNER
PHASE
SHIFTER
I
iLl-'s"
l(+J)
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