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I am looking at doing some M-S recording for some of the live shows I produce for audience reactions. This isn't dependant on a camera as most of the audio is generally used in podcasting and radio formats.
The plan is that I will use a omni for the mid channel, a figure 8 in the side channel which is fairly standard. Then also mix in wireless handhelds in mono from the presenters that will be wondering around the audience (think about the audience in a circle). The whole thing will be done to a stereo file, not separate channels.
Will having the handhelds directly put into the mix screw up the M-S recording? My logic says no, and the stereo image should be fine and collapse to mono without any issue. Am I missing anything here?
If you're recording the decoded M-S tracks as stereo, and add the handhelds in dead center there will be no problems with the mix, and mono-compatibility will be retained.
I don't know if it is an option, but you could think about recording the M-S channels without decoding, and adding the handhelds to the M-channel. That way you have control over the stereo image of the audience afterwards, while the handhelds will remain in the center no matter what you do.
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There should not be any problems if you decode the m/s before adding the extra voice channels.
However there will be the normal phase problems if the presenter ever comes close to the m/s mics and his or her voice is picked up by both. The general rule for radio is if the mics are close try and only have one open mic at a time.