Mix-minus is a particular setup for a mixing console, such that the output to a specific device contains everything except the input from that device. The advantage of a mix-minus is the elimination of echoes and feedback.
A mix-minus signal is sometimes also known as a ‘clean feed’ or a ‘Select Audio Return’ (SAR).
How is it used?
Back in my broadcasting days, I did some remote broadcasts from county fairs. "I’m broadcast live from the ___ County Fair…" You get the idea. During these broadcasts, I had a monitor so I could hear what was broadcast over the air. This way, I knew when to talk and when to stop talking. However, I never heard my own voice. If I had, due to the communications, I would have heard a slight delay which would have been super distracting.
You might have a situation where you have an outdoor event that is broadcasting into a sanctuary, such as a pool baptism or other outdoor activity. You might have a youth rally with events indoors and outdoors where you are showing outdoor activities within the church. Using a mix-minus setup, you can get the sound you need into the church without the issues that would be caused by repeating the input signal back out to the source.
Thought? Questions? Comments?