SCHOEPS VMS 5 U - Manual (Page 11)

11
11. Connecting headphones
Any stereo headphones with an
impedance of 32 to 2,000 Ohms can
be connected to the headphone out-
put of the VMS 5 U. Headphones with
a miniature plug can be used with a
commonly available adapter.
The headphone output is used for
monitoring; a switch <9> selects either
the unaltered "PREAMP" signals (e.g.
for A/B, X/Y or ORTF-style recording)
or the "MATRIX" outputs (left and right
signals derived from an M/S recording
setup).
Please note: When turning phan-
tom power on or off, or when setting
the input selector switch, please turn
the headphone volume control to its
minimum setting.
In the interest of hearing conserva-
tion, do not monitor at high sound
levels. Prolonged listening through
headphones at high levels can damage
your hearing more severely than listen-
ing at what may seem like the equiva-
lent level on loudspeakers.
12. M/S recording / WIDTH
M/S is used primarily when recording
sound for film or television, but is also
useful for music recording. Its advan-
tage is that the stereo image can be
adjusted after the recording has been
made, in post-production.
The principle of M/S: As with other
stereo recording techniques (A/B, X/Y,
ORTF, "Blumlein" etc.) two micro-
phones are used, of which one (the
"side" or "S" channel) must have a
figure-8 directional pattern; the other
microphone (the "mid" or "M" chan-
nel) may have any desired pattern. The
two microphones are placed one
directly above the other, but while the
M-channel microphone is aimed at the
sound source, the S-channel micro-
phone is aimed 90º to the left (see
illustration, top of page 12). Thus the
two microphones do not directly pick
up the left and right channel playback
signals; instead, these signals are
derived by means of a sum-and-differ-
ence matrix circuit such as the one in
the VMS 5 U. The left channel play-
back signal is formed by adding M+S,
while the right channel playback signal
is formed by subtracting M-S. This
works because the two lobes of a fig-
ure-8 microphone’s pattern are in
opposite polarity to one another.
The result is as if two "virtual micro-
phones" had been aimed symmetrical-
ly with respect to the main axis of the
actual M-channel microphone. The
directional pattern of these "virtual
microphones" depends on the actual
pattern of the M-channel microphone
as well as on the setting of the "WIDTH"
control <6>, which determines the rel-
ative gain applied to the M and S sig-
nals fed into the matrix.
The "WIDTH" control sets the width
of the stereophonic image. The useful