Am shooting a wedding this upcoming weekend, and am thinking, to be safe, of using multiple microphones, one on the groom, the other on the minister. But I'm worried about feedback--what causes it? How can I prevent it?
Feedback occurs when you have an audio input feeding into an audio output that is feediing back (hence the name) into the original audio input. An endless loop, if you will, that creates a nasty shriek. Picture a microphone plugged into an amplified speaker, with the two facing each other.
Put each mike on a separate channel and you should be fine.
Will the mics be going into the PA system? If so going from 1 to 3 mics will reduce your volume before feedback by about 5db, which should be tolerable. If the mics don't go into the PA no problem. Usual caveats like don't walk in front of the speakers etc.