A single mic on an acoustic guitar that sounds phasey is due more to the environment or to the poor off-axis response of the mic itself. All mics are NOT the same. That's why I keep mentioning the Schoeps cmc641. Somehow they have managed to make its off-axis response sound very coherent (less phasey).
It has been long held that SD mics are superior to LD mics for acoustic guitars because of off-axis problem on the wider diaphragms LD mics. Once more transparent headgrilles were used, e.g. Neumann TLM 103 and TLM 149, it became apparent that the headgrille itself was part of the problem. Sound passing through the headgrille would bounce around inside the capsule before and after it hit the diaphragm because the headgrille was stopping it from exiting. Reflected sound intermingling with the direct sound results in phase cancellation.
The TLM 103 and TLM 149 mic grilles are visually and, as it turns out, acoustically more transparent. While grille transparency itself is not the only factor, having a transparent headgrille makes a big difference.
Some mics are more "beamy." In that case, the diaphragm and capsule are creating frequency response anomalies where a frequency or frequencies are more (or less) linear depending on the specific angle that the sound strikes the mic and diaphragm. These are sometimes, but not always, more apparent around the edge of the pattern of a directional mic. It's weird, but I have heard them.
I learned about this by the generosity of mic design engineers at Neumann, Gefell and Schoeps whom I met while reviewing mics for trade magazines.
Regards,
Ty Ford
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