ortf question
Nate Najar wrote:
hypothetically speaking of course, if you were to do ortf with a pair
of mk41's, about how far apart should the capsules be?
with cardioid I do my best to get them at 110 degrees and they end up
around 6.5" apart. with the supercardioids, at 90 degrees, how far?
ORTF is traditionally cardiods at 110 degrees and a certain spacing, I think
it is 17.5 centimeters. Over here we say X-Y whenever we have microphones at
a short distance, from 0 to 25 centimeters between capsules. In the US of A
it is only X-Y if the capsule distance is 0 centimeters. Consequently the
wording ORTF gets used a lot of times when it shouldn't be and the wording
"intensity+time de-correlated" should.
It is all about de-correlation:
intensity decorrelation: coincident stereo, in USA called X-Y, capsule
distance zero.
intensity+time decorrelation: ORTF and similar, in Europe called X-Y,
capsule distance zero (remember zero == coincident) to 30 centimeters.
time decorrelation: A-B, capsule distance typically 30 centimeters to 2
meters, if you are very far from the source the distance can be
increased/needs to be increased.
thanks!
So the answer to your question is that it depends on how far from the sound
source you are. I mostly use an angle between 45 and 80 degrees when using a
standard K&M crossbar. For the ORTF angle of 110 degrees to work well you
have to remove the chais in the middle of row 4,5 and 6 so that you can
place the mic stand there and to me it would sound too distant due to too
much reflected sound anyway and audience noise might be a problem because
not behind the mic pair.
In the real world of live recording you determine which 5 square feet of
real estate you can place the mic stand on and adjusts mic angle and height
to get a good panorama with good tonal balance also for the rearmost guys.
Usually that implies aiming the mics vertically at the rearmost sound
sources. Doing that comes with an image advantage: mic PAIR off-axis
behaviour pulls extreme left and right of front row musicians toward the
center, thus at best changes the usual trapezoid orchestral image to a
rectangular.
Find and read that "Stereophonic Zoom" paper!
Kind regards
Peter Larsen
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