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Author Topic: Stereo Technique with MK41 or other super-cardioid Microphones  (Read 956 times)

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Offline DSatz

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Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #15 on: June 27, 2018, 02:18:16 PM »
just want to point out that heathen's reply is correct; for Ambisonic decoding to work, the GAIN of each recording channel must be exactly the same. Normally no effort should be made to make the levels equal; it's the gains that count. In any real-world recording the peak levels will almost certainly differ among the four channels, and that is as it should be.
  • Gain is the degree of amplification that occurs between point A and point B in a circuit or system. It can be "unity" a/k/a 0 dB, or it can be some positive number of dB or it can be negative, in which case the minus sign is usually dropped and then the number that remains is the amount of loss.
  • To calibrate the gains of the four channels precisely, if you can record some rehearsal material, make a rough setting so that all four controls are as similar as you can get them "by eye" and the highest individual level obtained via the microphone doesn't quite reach 0 dB. Note which channel had the highest peak levels. Then don't touch that one channel's record level control; we're going to adjust the other three channels to match its gain. Disconnect the microphone, and connect a signal generator to that channel, set the generator to some midrange frequency, and adjust its output level (not the recorder's level) so that the meter on that channel reads exactly 1 dB below full scale (assuming that your meters have a nice, clear marking for that exact level; if not, choose the exact level with the clearest marking available). Then attach the generator to each of the other three channels in turn--or if you can split the signal, do that; either way, don't adjust the generator's level, but instead set the record levels in the other three channels all to exactly the same level as you set the first channel to.
  • If you don't have any rehearsal or "throwaway" material, just set the levels the best you can, but conservatively enough that you definitely won't need to change them during the recording. At the end of the recording, again without touching the recording levels, use a tone generator to record a midrange reference tone on each channel (or on all four at once if you can split it). The level can be anything that's convenient below 0 dB. Then when you go to decode the recording, adjust the decoder's input level controls to make those four recorded signals all have equal levels.
--best regards
« Last Edit: June 27, 2018, 02:35:14 PM by DSatz »
music > microphones > a recorder of some sort


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