M CUBE Microphone System
The M Cube is a 9-channel microphone system for time-delay based 3-dimensional recordings. The nine microphones are arranged in the shape of a cube with a length of approximately one metre each side. The positions of the microphones are adjustable – so the dimensions of the microphone arrangement can be adjusted to the dimensions of the room and the sound source. The mounting bars have distance markings, so that any setting can easily be repeated.
The M Cube is set up as a 5.0 array with another four microphones for height information. Five M 102 capacitor microphones are used for the lower plane and four M 221 capacitor microphones are used for the upper plane. All the microphones are omni-directional pressure microphones. Because of this, the frequency response in independent from the distance to the sound source and there is no proximity effect; sensitivity to wind noise is very low.
The use of certified WS1F- and WS2F- measurement microphone capsules, combined with a 48V phantom powered pre-amplifier (that internally raises the capsule bias voltage to the required 200V) reaches a constant magnitude and phase response according to the tight tolerances of DIN EN 61094-4 and with transmission properties that are long-term stable. Only the diameters of the capsules and the noise level of the M 102 and the M 221 are different, all other transmission properties and the construction of both microphones are identical.
Because of the high 50mV/Pa sensitivity of the microphones, a lower level of pre-amplification is necessary. This results in a lower noise level in the recording. The optional use of the acoustic equalisation balls KA 3 and KA 4 for the M 221 results in an additional acoustic amplification in the high frequencies. Due to the use of metal diaphragms, the microphones are very insensitive to changes of humidity in the air. All parts of the capsule – including the diaphragm – are made of nickel, so they are very insensitive to temperature changes.
A standard sound calibrator can be used to supply the microphones with an accurately defined sound pressure level. Thereby all the microphones can be adjusted to an equal amplification and also the following equipment (EG: amplification or A/D converters) can be optimally adjusted to the expected sound pressure level at the microphone position.
Practical 3D Audio Recording – Christian Birkner, HTWK Leipzig – University of Applied Sciences