Through a series of practical tests students of the Tonmeister Institute of the Berlin University of the Arts
found out a stereo microphone system, which results in a fairly uniform distribution of the phantom
sound sources on the stereo speaker base as angle of incidence, at an effective recording range of the
microphone system by
θ ' = ±45° = 90°. This system was set up empirically with two small cardioid
microphones. It was found in this case, an overall axis angle with α = ±45° = 90° which is angled
outwards and has a microphone base (distance between microphones) of a = 25 cm (!). For the chosen
word"axis angle" we find in the literature opening angle, offset angle, and receiving angles, which can
be partially mixed with SRA = Stereo Recording angle and which often represent only half the angle.
The sometimes cited ear distance of the human head is in stereophony of no matter, because this
distance has absolutely no relevance to the loudspeaker signals.
In the formation of the respective frequency-neutral direction of listening the interchannel level
differences Δ L and in the the same sense acting interchannel time differences Δ t act together as
loudspeaker signals. This recording technique is called mixed stereo or equivalence stereophony.
Thus simultaneously the intensity stereophony and the time-of-arrival stereophony is applied. This signal
differences is denoted by the word equivalence.
Usually, the sound engineer must compose the special microphone system of two single-miniature
microphones. Large double-diaphragm microphones should be avoided because of their unbalanced
directional characteristics and the larger phase transitions. It seems advisable to experiment with the
two parameters, the axis angleα for Δ L and the microphone base forΔ t.
A sound recording with a main microphone system is often supplemented by additional spot or support
microphones. |
