Microphones 551suspension and the DSP-4 KFM 360 processor,
Fig. 16-129.
The central unit in this system is the sphere micro-
phone KFM 360. It uses two pressure transducers and
can, even without the other elements of the system, be
used for stereophonic recording. Its recording angle is
about 120°, permitting closer micing than a standard
stereo microphone. The necessary high-frequency boost
is built into the processor unit.
Surround capability is achieved through the use of
two figure 8 microphones, which can be attached
beneath the pressure transducers by an adjustable,
detachable clamp system with bayonet-style connectors.
The two microphones should be aimed forward.
The DSP-4 KFM 360 processor derives the four
corner channels from the microphone signals. A center
channel signal is obtained from the two front signals,
using a special type of matrix. An additional channel
carries only the low frequencies, up to 70 Hz. To avoid
perceiving the presence of the rear loudspeakers, it is
possible to lower the level of their channels, to delay
them and/or to set an upper limit on their frequency
response, Fig. 16-130.
The front stereo image width is adjustable and the
directional patterns of the front-facing and rear-facing
pairs of virtual microphones can be chosen indepen-
dently of one another.
The processor unit offers both analog and digital
inputs for the microphone signals. In addition to
providing gain, it offers a high-frequency emphasis for
the built-in pressure transducers as well as a
low-frequency boost for the figure 8s.
As with M/S recording, matrixing can be performed
during post-production in the digital domain.
The system operates as follows: the front and rear
channels result from the sum (front) and difference
(rear) of the omnidirectional and figure 8 microphones
on each side, respectively, Fig. 16-131. The four
resulting virtual microphones that this process creates
will seem to be aimed forward and backward, as the
figure 8s are. At higher frequencies they will seem to be
aimed more toward the sides (i.e., apart). Their direc-
tional pattern can be varied, anywhere from omnidirec-
tional 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 direc-
tional patterns alters the sound as well, in ways that are
not possible with ordinary equalizers. This permits a
flexible means of adapting to a recording situation—to
the acoustic conditions in the recording space—and this
can even be done during postproduction, if the unpro-
cessed microphones signals are recorded.
This four-channel approach yields a form or
surround reproduction without a center channel—
something that is not what everybody requires.16.7.7.2 Holophone® H2-PRO Surround Sound
SystemThe elliptical shape of the Holophone® H2-PRO
emulates the characteristics of a human head, Fig.
16-132. Sound waves bend around the H2-PRO as they
do around the head providing an accurate spatiality,
audio imaging, and natural directionality. Capturing the
directionality of these soundwaves translates into a very
realistic surround sound experience. The total surface
area of the eight individual elements combines with the
spherical embodiment of the H2-PRO to capture the
acoustic textures required for surround reproduction,
Fig. 16-133. The embodiment acts as an acoustic lens
capturing lows and clean highs.
A complete soundfield can be accurately replicated
without the use of additional microphones—a simple
point-and-shoot operation. The Holophone H2-PRO isFigure 16-129. Schoeps KFM 360 sphere microphone.
Courtesy Schoeps GmbH.