Damn, if you don't learn something new every day

Corbett | September 27, 2004 1:56 PM

For some reason this sound geek stuff completely appeals to me...

Lately I've been experimenting with a "near coincident pair" method for placing microphones in a stereo configuration. The one I'm testing these days is called ORTF and is named after the Office de Radiodiffusion-Television Francaise, who figured it out for live broadcasts. Two cardiod microphones are spaced 17 cm (6.7" - which is approximately the distance between a pair of ears) apart and are angled outwards 55deg from each other (110deg total - about the same angle that your ears are angled.)

But the fun stuff comes when you start trying to figure out how to play with the stereo field of vision.

The logic: "If you want to adjust the stereo spread, you change the angle of the microphones. Pointing them farther away from each other centers the signal. Pointing them more toward the center widens the stereo field."

This of course is completely counter-intuitive...

...until you think of the arc covered by the microphones as the range of sounds that will sound centered between the channels.

If you point both microphones near the middle (say 30 degrees), then almost everything to the left is left of the left channel and almost everything to the right is right of the right channel. The stereo field is much wider than the microphone spread.

If you spread the mics wide (say 135 degrees) nearly everything in the stereo field is between the microphones (right of left and left of right) effectively narrowing the stereo field leaving the speakers.

Hmmm, that's pretty geeky.

---

Category: Music

---