David Satz wrote on Sat, 31 July 2004 12:15
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Klaus, Have you ever tested a KM 86 with its wire grille removed? If the off-axis weirdness were caused by the wire mesh, why is hardly any such weirdness apparent in the cardioid setting of the microphone?
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David,
You cannot remove the outer grille from a KM86 because of stray hum. You would have to test the mic inside a Faraday cage that would need to have room for the listener and the mic and the sound source.
But you can, and this is part of my KM86 modification, remove the tightly woven mesh in front of the KK84-type capsules in that mic. This mesh is completely useless and without any function in the KM86. This is not a do-it yourself job, as the capacitance of the capsule systems has to be recalibrated after removal of the mesh and reinstallation of the diaphragm plate!
Please do not remove the mesh from a KM84 capsule when used in a KM84 mic! The mesh is very much needed to protect the capsule's diaphragm from particles and air movement;
As mentioned earlier in another thread regarding some of the shortcomings of the KM86, the removal of this mesh which forms a sound barrier, opens the mic's sound up considerably.
Regarding the off axis weirdness (which in this mic I find just as phasey and weird in cardioid as in all other patterns): You are of course right that a screen at close proximity to, and parallel with, the diaphragm would not have an effect on the off-axis performance, as measured with a sine wave sweep.
What the four screens in the KM86 introduce, and which a lay person could describe as a "phasing" effect , is actually generated by cumulative comb filtering and standing waves: the comb filtering comes from the wire meshes of varying thickness which are frequency discriminating; the standing waves come from the circular grille surrounding the capsule heads and the two parallel surfaces of tight-screen KK84 mesh and diaphragm.)
The phasing is not discriminating per se to angle of arrival, but is maybe more noticeable off axis, when certain frequencies are more or less prominent, through resonance or filtering, as described above.
Long story short: Even without any additional electronic improvements, the KM86 mic is a more useful, lively, musical tool once the innermost screens from the two capsule heads have been removed.
Kind regards,