Specifications

98
Sphere Surround
Surround Microphone System by Bruck
with KFM 360 and DSP-4 KFM 360
– compact, highly effective arrangement
– extensive capability for post-processing in digital
domain (many important parameters can be adjusted
after the recording has been made)
– digital and analog inputs and outputs
– analog-style controls
– user preference settings can be stored and recalled
The central unit in this system is the KFM 360 sphere
microphone. It uses two pressure transducers and can
also be used for stereophonic recording. Its recording
angle
+
is ca. 120°, thus permitting closer miking than
the pure stereo microphone KFM 6 (90°). The necessary
high-frequency compensation for the pressure trans-
ducers is built into the processor unit.
Surround capability is achieved through the use of
two figure-8 microphones, which can be attached next
to the pressure transducers by an adjustable, detachable
clamp system with bayonet-style connectors (SGC-KFM).
The main axes of these two microphones should be
aimed precisely forward.
The DSP-4 KFM 360 processor derives the four
“corner” channels (L, R, LS, RS) from the microphone
signals. A center channel signal is obtained from the
two front signals. An additional output channel is pro-
vided which carries only the frequencies below 70 Hz.
To avoid perceiving the presence of the rear loudspeak-
ers one can lower the level of their signals, delay them
and / or set an upper limit on their frequency response.
The front stereo image width is adjustable, and the
directional patterns of the front-facing and rear-facing
pairs of “virtual microphones” (see “Operating principle”
below) can be chosen independently of one another.
The processor unit offers both analog and digital
inputs for the microphone signals. In addition to pro-
viding gain, it offers high-frequency compensation for
the pressure transducers as well as low-frequency
com pensation for the figure-8s.
As with M/S recording, matrixing can be performed
during post-production. All matrixing in the DSP-4 is
performed in the digital domain.
Operating principle:
The front and rear channels result from the sum (front)
and difference (rear) of the omnidirectional and figure-8
microphones on each side respectively (see illustration
on the next page). The four resulting “virtual micro-
phones” which this process creates will seem to be
aimed forward and backward, as the figure-8s are.
At higher frequencies, however, they will seem to be
aimed further outward. Their directional pattern can
be varied anywhere from omnidirectional to cardioid
to figure-8; the pattern of the two rear-facing virtual
microphones can be different from that of the two
forward-facing ones. Altering the directional patterns
alters the sound as well, in ways that are not possible
with ordinary equalizers. This permits a flexible means
DSP-4 KFM 360
processor unit with built-in A/D and
D/A converters
+
KFM 360
DSP-4 KFM 360 processor
KS 5 U
5 m
KLY 250/5 SU
5 m
XLR-5 XLR-5 XLR-5
6 × XLR-3
XLR-5 XLR-5
I II I II III
inputs outputs
KFM 360
3 × AK SU/2U
adapter cable
*This is the range within which the sound sources should be
placed, as “seen“ by the microphone.
SGC-KFM
CCM 8Lg
(figure-eight)
250 mm