neumann.berlin
the microphone company
KM 66 - The Figure-8 for an Even Sound Field
Occasionally, by combining elements of existing products,
previously unknown possibilities are discovered. One example of this in Neumann’s product history is the KM 66,
a switchable-pattern miniature microphone first produced
in 1966.
In developing this microphone, Neumann combined two cardioid capsules from the KM 64 in a
special way: the diaphragms face away from
each other with a spacing
of 10 mm; the backplates
are separated by an elliptical divider. The result is
a capsule combination producing excellent polar pattern characteristics, even
in the extreme low-frequency range. Even at
40 Hz, the rear-to-front
differential for each single capsule is 20 dB!
In an even (diffuse) sound field, no appreciable change in
on-axis (0 degrees) response occurs when switching from
omni to cardioid pattern. Also, when the backside capsule
is added (for omni), there is less than a 10% increase in
output voltage from the microphone.
In contrast, polar diagrams
of typical dual-diaphragm
microphones indicate that
the reverse attenuation of
the cardioid pickup pattern decreases remarkably
towards the low frequencies. When the two capsule halves are activated at
the same time, the backside part adds a much
higher share of the whole
signal. This generates an
narrower figure-8 pattern
in the low frequencies and
an uneven response due to
changes in distance.
In the KM 66, the cardioid and figure-8 patterns
feature an accurate representation of low frequencies, even
in such a case where the microphone is used at a greater
distance from the sound source. This near-ideal carioid capsule with its unique attributes is a great asset to other microphones utilizing it: the KM 64, U 64, KTM, KM 74 and
the legendary KM 84.
Loading...