SCHOEPS
GmbH · Spitalstr. 20 · D-76227 Karlsruhe (Durlach) · Tel: +49 721 943 20-0 · Fax: +49 721 943 2050
www.schoeps.de · [email protected]
Filters
18
English
But using them still only makes most sense
when they are already close enough for direct
sound to predominate in the result. For out-
door recording this will not be an issue when
there is little or no reflected sound energy – but
indoors, even a shotgun microphone should
generally be kept fairly close to the intended
sound source.
5. The usefulness of shotgun microphones for
stereophonic recording is limited by the fact
that their polar patterns differ at low vs. high
frequencies. X/Y stereo recording with two
shotgun microphones cannot really be recom-
mended, but M/S stereo recording with a
SCHOEPS CMIT 5 U with a small figure-8 con-
denser micro phone or capsule (such as the
SCHOEPS CCM 8 or MK 8) mounted on it can
produce very good results.
When mounting a figure-8 microphone or
capsule on a shotgun microphone, one should
be sure to place their diaphragms one directly
above the other, remembering of course that
the diaphragm of a shotgun microphone is at
the base of the interference tube, not at its tip.
Filters
The CMIT 5 U has three switchable filters. Each
is activated or deactivated by pressing a button.
They can be used to suppress low frequencies
or to boost high frequencies.
The two low-frequency filters start working
from 80 Hz and 300 Hz. However, even when
these are both switched off, there is another
low filter active below 40 Hz at a slope of
6 dB/oct. The steep low-cut filter below 80 Hz
(18 dB/oct.) suppresses wind and boom noise.
The filter below 300 Hz (6 dB/oct.) is a gentle
roll-off that compensates for proximity effects
(elevation of low frequencies by directional
microphones in near-field use). They also pro-
tect against disturbing, inaudible (infra-)sound
that can be caused by ventilation systems,
track vehicles and wind. What is tricky about
this is that although it is hardly noticeable,
infrasound can cause strong audible distortions
in the connected equipment when it leads to
an overload. This would make it impossible to
produce a useable record.
A high-frequency emphasis compensates
80 Hz, 18 dB/oct.
300 Hz, 6 dB/oct.
+5 dB at 10 kHz
M/S arrangement with shotgun microphone
(shown here: CMIT 5 U with CCM 8 and KMSC
double clip.)
The membranes of the two microphones
must be aligned one above the other; the black
line indicates their location.
Make sure all of the slits in the tube (sound
inlet openings) are free and uncovered when
using the microphone. Covering slits can alter
the sound and directivity of the microphone.
* Reverberation radius (”critical distance”): A sound
source generates a certain level of direct sound energy
which diminishes strongly as a function of distance.
If the sound is occurring in a room, some amount of
diffuse sound energy will be built up by repeated
reflections from acoustic barriers (mainly walls).
The level of diffuse sound in any given part of the
room will depend less on the distance from the sound
source than is the case for the level of direct sound.
In the theoretically ideal case, the level of diffuse sound
would be the same everywhere in the room.
The distance at which the reflected sound reaches
an equal level to the direct sound is called the rever-
beration radius. (”Radius” is used because we assume
that sound from a point source will spread out in a
spherical manner.)
