Great if you have a limited footprint.
A-B stereo setup for omnis
Mic distance (cm) Recording angle (degrees)
17 180.0 Healy method
20 116.4
25 85.7
30 69.0
35 58.1
40 50.3
45 44.4
50 39.8
60 32.9
70 28.1
80 24.5
90 21.8
100 19.6
Almost binaural-like over headphones (Healy's original application was to feed in-ear monitors with on stage sound).
It can sound good over speakers in the right conditions, but you'll probably prefer a wider spread for speaker playback if you can get away with a larger footprint.
I did some walk around tests last weekend with various omni spacings calling out the numbers of the clock and shaking a shaker (getting some odd looks in the church parking lot where I set up
). The chart above does apply somewhat (more so from a distance) but not perfectly. Sound will be picked up from any angle of course, but there will be differing amounts of angular distortion - on playback sounds away from center may be clumped at the ether earphone or speaker for wider spacings and spread out wider than normal for sources in the middle. But the stereo separation and spaciousness increases for wider spacings at the same time, so there is a bit of a trade-off. At larger mic spacings close to the source, like on-stage or stagelip, there are level changes between the mics that offset the time-based recording angle chart above.
Another thing to keep in mind is the high frequency directionality of most omnis. To get the high frequency shaker sounds to locate like the lower frequency voice required angling the mics outwards, otherwise the hf were evenly distributed and non-directional. I preferred +- 45deg for wide spacings which provided hf directionality while preserving an even brightness at the center or 12-o'clock. the Healy method with mics angled +-90 deg (180deg opposed) at 17cm gives good hf directionality & ambience for sounds from all around (again what Healy originally designed the congfig for) while getting slightly dull at the center positions (around 12 and 6-o'clock).
Very informative way to spend an afternoon. I highly recommend setting up and doing some walk around tests to get your mind around what happens. Next time I'll get a low frequency source like a drum going too, and try some other configs.