Five directional characteristics can be selected using a rotary switch. In the sixth position "R" of the switch, the directional characteristics can be switched by means of the N 248 power supply without requiring a special cable.

The microphone also features a switchable 10 dB pre-attenuation for very high sound levels and a shock filter with an operating frequency of 100 Hz.

Application

The TLM 170 R condenser microphone is a switchable large-diaphragm microphone, distinguished by its transmission characteristics and its various switching options. It is used in a wide range of applications in broadcasting, film and television, as well as in the semi-professional field.

The directional characteristics can be switched directly on the microphone as well as remotely from a dedicated power supply.

Acoustic characteristics

The dual-diaphragm capsule in the microphone's wire mesh basket exhibits particularly flat frequency characteristics for all adjustable polar patterns. This is true not only for sound coming from the front, but also for sound arriving laterally within an angular range of more than ± 100°.

Consequently, the diffuse-field frequency responses up to 10 kHz are also parallel to the 0° curves. In practice, this affects the portions of sound reaching the microphone indirectly via reflections in the recording space.

This also means that the microphone does not alter the sonic characteristics. Since no resonance effects are used to achieve the microphone characteristics mentioned above, the impulse response of the microphone is excellent. It is therefore capable of transferring all equalisation processes in music and speech without any distortion. The capsule is elastically mounted to protect it against structure-borne noise.

Directional characteristics

In addition to the usual directional polar patterns: omnidirectional, cardioid and figure-8, we have added a hypercardioid and wide-angle cardioid characteristic. Compared to the standard cardioid pattern, the hypercardioid characteristic suppresses lateral sound more effectively. The wide-angle polar pattern is particularly useful for recording large sound sources.

Remote control

Remote control of the directional characteristics using the N 248 power supply is achieved by varying the phantom power in the range 48 V ± 3 V (the corresponding standard allows a range of ± 4 V).

In the "R" position of the switch (= Remote control), the TLM 170 R microphone evaluates the absolute level of the phantom power and adjusts to the associated directional characteristic. As in conventional operation, the standard 3-pin microphone cable is used, with cable lengths of up to 300 m permitted.

Electrical properties

The letters TLM stand for "transformerless microphone". The TLM 170 R normally replaces the commonly used output transformer with an electronic circuit which — like a transformer — ensures good unbalancing. As a result, interference signals acting on the balanced modulation line are suppressed as usual.

Tripod use
For tripod mounting, the TLM 170 R features a laterally mounted swivel mount that effectively protects the microphone against low-frequency mechanical vibrations thanks to integrated rubber elements. It can be removed if necessary or mounted on the other side of the microphone.

To use the IC 4 cable (for example, to suspend the microphone from above in conjunction with the MNV 87 tilt device), the swivel mount with its bracket must be removed from the microphone. A thread for screwing on the cable is then exposed at the connection section of the microphone.

Filter and pre-attenuation

To avoid overloading the input of the downstream amplifier, a 10 dB pre-attenuation can be activated at the rear.

A further switch allows the frequency response below 100 Hz to be lowered in order to suppress low-frequency interference.

Operational safety

The capsule surface, including the diaphragms, is at ground level and is therefore insensitive to electrical and atmospheric influences as well as to dirt.