Off Axis Response

Buzz here.

Take a not good microphone and place it one hand span away from the 12th fret of an acoustic guitar. Obviously the direct response will come from the 12th fret area. Not so obviously the off axis response will provide high frequency sound from the strings.

What if the off axis response of the mic is horrible?

Your guitar will probably sound like crap.

Small diaphragm condenser mics like Shure's SM81 and Neumann's KM184 have fairly uniform off axis responses, so you can place them fairly close to the source at an angle and not worry about off axis issues.

You will probably notice that these mics have a presence in almost every major recording studio.

What about large diaphragm mics?

It's very difficult to design a large diaphragm mic with a uniform off axis response considering it has an element that has a half wavelength resonance in the 6.7 kHz range. It is for this reason that large diaphragm mics are generally used an arm's length or further from the guitar. This will allow more of the room into the sound and lessen the sense of intimacy though. There are large diaphragm mics that have excellent off axis responses.

They are generally made by people who speak German and are very expensive.

We generally use either the Shure (flat and neutral) or the Neumann (slightly glassy 8 kHz bump) for close mic'ed acoustic guitars, hi-hats and cymbals.

They both give excellent results.