The RSM 191 is a stereo microphone system consisting of the microphone and the MTX 191 A matrix amplifier. It has an adjustable pick-up angle and high directivity. The microphone has two separate capsule systems, a hypercardioid element and a figure-8, both in a short shotgun. Together they generate the mid and the side signals.

The matrix amplifier controls the width of the stereo image by changing the gain of the side signal relative to the middle signal in six 3 dB steps. The output signals of the matrix amplifier are either mid-side (MS) or left/right (XY). The signals are converted through transformerless sum-and-difference circuitry.

The balanced, transformerless technology permits the use of long cables between the microphone, the matrix amplifier and the following mic input of other signal processing equipment.

Applications

The RSM 191 system is an ideal microphone system for:

Outdoor stereophonic news coverage, even in extremely noisy surroundings;

Stereo recordings for film and television where the actors are recorded simultaneously with acoustic ambiance, or an orchestra;

Stereophonic motion picture sound where the width of the sound image must match the camera viewing angle.

Construction

The RSM 191 consists of a capsule head containing two separate transducer systems and an amplifier section with two independent transformerless microphone amplifiers.

An interference tube system with a hypercardioid characteristic generates the middle signal, while a horizontal figure-8 assembly provides the side signal.

Acoustic features

The RSM 191 achieves its high directivity and special acoustic features through a unique construction. The microphone capsule assembly is mounted inside a housing tube that is acoustically open but has a high flow resistance.

This results in a high driving force for the diaphragm, even with a low pressure gradient factor of the capsule. Therefore, the microphone can suppress unwanted off-axis interference to a considerably higher degree than other microphones without such an interference tube.

The middle system (M-signal) combines high attenuation of lateral sound incidence, similar to a hypercardioid characteristic (which is about 10 dB), with the large front-to back ratio of the super-cardioid characteristic.

Therefore, sound from the rear is likewise attenuated by approximately 10 dB. This design approach makes the microphone less sensitive to wind or pop noise than other shotgun microphones.

The side system (S-signal) consists of two single capsules arranged back to back, closely behind the interference tube (M-signal) capsule. Arrows engraved on the microphone housing show their orientation.

The uniform and balanced performance characteristic of the microphone system is achieved without resorting to corrective resonance effects. Therefore, the microphone maintains an excellent impulse response, reproducing all transient phenomena in music and speech without coloration. The entire internal construction is decoupled from the housing to avoid structure borne and handling noise.