Topic: X/Y choir miking oddness

[rjp]

1½" isn't very different from the capsule spacing in some large diaphragm stereo mics assuming that you mean the capsule centres are 1½" apart, not that there's a 1½" air gap between the two vertically aligned mics?. If it's the latter then you should get them closer - as close as possible without them touching. On closer micing techniques and/or with smaller ensembles or single instruments/voices, then vertical spacing is more of an issue and getting the capsules as physically coincident as possible is much more important. Though the same is true of any coincident technique. Closer and smaller makes for reduced margin for error. Usually, moving one source a foot closer to a mic six feet away makes a huge difference compared to moving it a foot closer to a mic 20' away. It's a game of ratios.

It's the latter - the 1½" is the gap between the mics, which are vertically aligned. The Perception 170 is a small-diaphragm cardioid.

When I got home, and loaded the file into Audacity, I noticed that the instruments were quite clear, while the choir had a strange, distorted sound. Meanwhile, the stereo image left a lot to be desired. However, my purpose in going with X/Y was so that I could convert it to Mid/Side to tinker with the stereo image.

I'm curious what you mean by "the choir had a strange, distorted sound". Without hearing it, it's impossible to be sure but I'm wondering whether it might be a facet of the pair positioning relative to the choir/instruments. At 21' from the front of the choir, I'd guess that unless it's either a large choir or laid out in a very wide arc (which, with rows of 6/7/7, doesn't seem likely), the majority of the singers are being picked up in a relatively narrow portion in the centre of the XY pair acceptance angle. In a 90 degree XY pair of cardioids, the centre of the image is well off axis on both mics, in a region where their frequency responses and polar patterns can be very 'untidy', and I frequently find that the centre stage image produced by such a pair is poor in terms of sounding uneven, too narrow, and 'congested', even distorted. Also I find that it exaggerates the depth and width perspectives between close and far which adds to the perception of distant sources sounding more mono and less clear, when the imaging and clarity on closer sources is proportionally much stronger.

That sounds spot-on to explain what happened.

When I got home, and loaded the file into Audacity, I noticed that the instruments were quite I converted the L/R channels to M/S, and was stunned when I boosted the Side track - the stereo image became vastly better, and the distortion went away. I wound up boosting the Side track by +7 dB, which gave me what I felt was the most realistic imaging. The final result was nothing short of fantastic.

When you say "the stereo image became vastly better, and the distortion went away" how did the image get 'better'?

The squashed perspective opened up, as if the mics were closer to the action, and I no longer heard the distortion that I had been hearing with the unprocessed X/Y track.

At any rate, though I salvaged a bad situation, I think I'll go with ORTF next time, unless I can get a figure-8 mic into my arsenal and record true M/S.