Shure VP88 User Manual page 3

Stereo Output Mode
In Stereo Mode, the VP88 uses its internal matrix to mix the
Mid and Side signals and provide Left and Right stereo out-
puts. The three settings (H, M, and L), determine the strength
or width of the stereo effect, as described below. Nominal Left
and Right pickup patterns are shown in Figure 3.
NOTE: The mono sum (Left + Right) in any Stereo position is
always equal to the Mid signal, ensuring mono compatibility.
L (Low): Side level 6.0 dB lower than Mid level. The ste-
reo image spread of the stereo images is small. Use this
setting for distant miking, or in situations where the micro-
phone directionality cannot be well controlled, such as
hand-held use.
LOW STEREO (L)
0
o
30
o
60
o
90
–20 dB
–15 dB
o
120
–10 dB
–5 dB
o
150
o
180
MS Output Mode
In MS mode, the VP88's internal stereo matrix is bypassed.
The signal from the mid cartridge is sent to the red connector
on the Y-splitter cable (M) and the side cartridge output is sent
to the green connector (S). The Side on-axis sensitivity (90°
from the front axis of the microphone) is 1.6 dB higher than
the on-axis sensitivity of the Mid output. The sensitivities of
the Mid and Side outputs are equal at 45° off the front axis of
the microphone. The polarity of the left lobe of the Side output
matches the polarity of the Mid output. The right lobe of the
Side output is opposite polarity. See Figure 4.
EXTERNAL MATRIXES
When using an external stereo matrix, such as a matrix
transformer or active matrix circuitry, set the VP88 to MS
mode (refer to the Output Mode paragraph).
The Mid and Side outputs can be processed through a
sum-and-difference matrix to produce Left and Right stereo
signals as follows:
Left = Mid + Side
Right = Mid – Side
A 1:1 ratio of Mid to Side produces stereo signals identical
to those obtained with Stereo Output switch set to High (H).
o
30
o o
60 60
o o
90 90
o o
120 120
o
150 150
NOMINAL PICKUP PATTERNS FOR STEREO OUTPUT MODE
In the L position, the microphone also picks up the least
amount of ambient sound from the side, and can be used to
reduce high ambient noise or reverberation. The L setting
can be useful if the area being miked is already very wide.
However, the degree of stereo effect may be compromised
in narrow performing areas.
M (Medium): Side level is 1.9 dB lower than Mid level.
The increased side ambience pickup and stereo spread
make the M setting ideal for most applications.
H (High): Side level is1.6 dB higher than Mid level. The H
position provides the most side ambience pickup and the
greatest amount of stereo spread. This setting is only ap-
propriate if a high degree of ambience pickup is acceptable
and the performing area is not excessively wide.
MEDIUM STEREO (M)
0
o o
30 30
o
60
o
90
–20 dB
–15 dB
o
120
–10 dB
–5 dB
o o
150
o
180
FIGURE 3
NOMINAL PICKUP PATTERNS FOR MS OUTPUT MODE
Results similar to the Medium (M) and Low (L) settings can
be obtained by attenuating the side signal before matrixing.
NOTE: An external matrix can be useful when recording,
because decisions on stereo imaging are deferred to the
post-production stage. Two suggested matrix boxes:
Model MS38 DM Dual-Mode Line-Level MS Matrix
or
Model MS380 TX Stereo Microphone Preamplifier with
Dual-Mode MS Matrix and Line Driver.
Both are manufactured by Audio Engineering Associates,
1029 N. Allen Ave., Pasadena, CA 91104 U.S.A.
3
HIGH STEREO (H)
0
o
30
o
60
o
90
–20 dB
–15 dB
o
120
–10 dB
–5 dB
o
150
o
180
0
o o
30 30
o
60
o
90
–20 dB
–15 dB
o
120
–10 dB
–5 dB
o o
150 150
o
180
FIGURE 4
o
30
o
60
o
90
o
120
o
150
o
60
o
90
o
120