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6. Equivalent directional characteristics combinations

Physically seen, the XY and MS recording techniques are equivalent under certain circumstances. As we have already seen, there is a simple relation between the signals L, R, M and S; they can be converted into each other. this conversion is also called stereo conversion.

M = L+R L = M+S
S = L-R R = M-S

Since M and S can be converted into L and R in the same way as L and R into M and S, both conversions can be done with the same device (sum-difference transformer or differential transformer).
Due to this equivalence, certain XY-combinations correspond theoretically to certain MS-combinations. But in practice one will find some differences between equivalent XY-MS combinations. Since the microphone voltages are frequency dependant, all MS-combinations reproduce the higher frequencies better in the range of the symmetry axis for example, the XY-combinations better in the lateral ranges.


Coincident microphone
Coincident microphone
Fig. 12


Coincident microphone
Fig. 13


Definition of terms for upright standing coincident microphones

1. fixed capsule channel I delivers in XY-Technique: L signal
delivers in MS-Technique: M signal
 
System I (below)
 
2. revolving capsule channel II delivers in XY-Technique: R signal
delivers in MS-Technique: S signal
 
System II (above)
 
3. angle of displacement: angle at which the main sensitivity directions of the microphone capsules are turned away from the symmetry axix (mechanically)
Adjustment: XY-combination: freely selectable
MS-combination: M = 0 ; S = 90
 
 
4. recording range: range, that at replay will be represented inside the "Stereo Basis"
 
5. recording angle: angle that includes the recording range

 

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BackNextUp Stereo recording techniques