From: John Ouzts <jouzts@mc...> - 2005-05-05 21:31:50
I record with a stereo mic that uses a pair of co-incident figure-eight mics
set at 90 degrees to each other (from Blumlein's original 1931 EMI patent for
stereo, where he also patents the Mid-Side form of stereo). In addition to
being able to switch back and forth between stereo and MS (a turn of 45
degrees), you can also rotate the direction in which the pair of mics "faces"
by any number of degrees. (Since the mics are figure-eights, the back
hemisphere is identical to the front hemisphere, however.)
In those cases where the musicians don't stay put, or where a hanging stereo
mic rotates on its cable, I have been using my two channels to create a fake
Ambisonic B Format 4 channel file, then using Richard Furse's B Format rotate
plugin to rotate Ambisonic channels X and Y, and finally throwing out the W
and Z channels to leave me with the rotated right and left channels I want.
This works, but it is painfully slow, especially when working with a 3 GB
recording, which becomes a 12 GB ReZound working file before all is said and
Then I noticed that Richard had already set up his plugin so that it would
work with a 3 channel pantophonic B Format signal, since most people don't
use the Z vertical difference signal anyway. I emailed Richard to see if he
would allow his Ambisonic plugin to be further abused by dropping the
requirement for the W (omni, pressure) channel. He sent me a completely new
plugin, called rotblumxy.c, custom-made for rotating _true_ Blumlein X/Y. (By
true I mean two figure-eight mics with good polar response set at 90 degrees
to each other, not latter-day crossed cardioids.)
Richard was most helpful and I'm sure he would not mind sharing this plugin
with anyone else who records in this antique but glorious fashion.
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