From the Oade board: The Streicher - Healy Method
There are two more interesting coincident techniques we would like to cover.
One developed by Ron Streicher as a soloist pickup, uses omnidirectional microphones, which exhibit some directional characteristics at higher frequencies. This technique used with an included angle between 60 and 90 degrees yields a very stable center image with a good sense of space. The use of a pressure transducer (omnidirectional microphone) eliminates the pops and breath blasting problems associated with pressure gradient (directional microphones).
A variation of this technique, developed by Mr. Dan Healy, the living GOD of live sound, and a convenient segue into our next topic, is the near coincident 180 degree omnidirectional microphone method. Here a pair of omnidirectional microphones are placed approximately ear distance apart and oriented at 90 to the sound source, facing outward.
While the Streicher technique is suited only to close sound sources or binaural playback (headphone listening) the Healy method produces a recording suitable for playback on stereo speakers as well as headphones. We did some of these at the Greek Theater, they are labeled as "critically spaced omnis", enjoy !
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I never tried either of these methods, but those Greek recordings are the best I've ever heard. I've always been to chicken to run omnis, either in the above configs or spaced. Although if I ever make it back to Red Rocks or any similar outdoor venue, it will be omnis.