Yea, sound from the board for something like this is rarely good for the video.. the purpose of the soundboard is to set the levels for optimal sound ‘in that room’.
There’s a few ‘BUT’s’ in that statement, but I’m skipping them..
I agree that setting up at least 2 zoom like recorders is the way to go, unless someone else is recording, the just ask to do a film slate ‘CRACK’ at the end of the recording and have them include that in the final audio files they give you.. I’ve done that before and it mostly works…
the bigger issue there is syncing the audio, for that have some b-roll of the audience or something 🙂 Have you asked the guy before you how he got his audio? That’d be the first thing I did. Good luck.
