|
The TLM 50 is a
studio microphone with an unusual omnidirectional characteristic.
The same way as in the legendary M 50, the capsule is mounted flush
into the surface of a sphere.
This unique design gives the microphone a smooth rise in frequency
response and an increased directivity in the upper frequency range.
There the directional characteristic is almost comparable to a
pressure gradient microphone. In the lower audio spectrum it
performs more as a pressure transducer with a linear response down
to the lowest frequencies.
In 1991 the TLM 50 received the MIX MAGAZINE TEC-Award. It is
supplied with a swivel mount cable and an auditorium hanger.
Applications
The design of the TLM 50 is based on the legendary M 50 and has
very unique acoustic features. It provides a tool for capturing
both direct sound from the instruments and a balanced image of the
reverberant environment and is therefore especially suited for
stereo recordings with two main microphones.
Acoustic features
The diaphragm of the pressure capsule is 12 mm in diameter and is
only 5 µm thick. As a result it has a remarkably fast
transient response. The diaphragm is made out of titanium,
manufactured by Neumann in a proprietary electroplating
process.
The headgrille is acoustically very transparent. Even extreme sound
pressure levels do not at all affect the transducer's response. Of
course, the headgrille also protects the microphone capsule from
mechanical shock and serves as wind and pop screen.
Electrical features
The letters TLM stand for "transformerless microphone". The usual
output transformer is replaced in the TLM 50 by an electronic
circuit. As with traditional transformers, this technique ensures
good common mode rejection, and prevents RF interference, that may
influence the balanced audio signal. The transformerless microphone
amplifier provides low self noise, fast transient response, and
high output capability.
To protect the capsule from hum pickup through the gauze mesh, it
is designed as an "active capsule": The capsule housing contains
the impedance converter built as a hybrid module. The resulting
audio signal is fed with low impedance to the filter and output
stage in the housing.
Filter and attenuation
A -10 dB switch and a high-pass filter for the attenuation of
frequencies below 100 Hz are located at the rear of the microphone.
In the position LIN, the cutoff frequency is 30 Hz. Its purpose is
to protect the following equipment from subsonic interference (for
example strong air currents).
The -10 dB function is achieved by reducing the capsule polarizing
voltage from 60 V to 23 V. It helps to avoid overloading the
following units during very high sound pressure levels. The switch
does not extend the dynamic range of the microphone amplifier, but
shifts it upward by 10 dB.
Cable suspension
The recommended accessories, such as cables and connectors, provide
sufficient stability and therefor allow suspending the TLM 50 eg.
from the ceiling of a concert hall with the included MNV 87
auditorium hanger freely from its own cable.
|
