Mix Minus; Why Remove A Source's Own Input From Its Foldback Mix; Mix Minus Output - Calrec SUMMA User Manual

MIX MINUS

Summa's mix minus system allows a comprehensive foldback mix to be sent to multiple listeners. Using the auto minus
bus along with mix minus outputs allows you to provide to listeners a complete mix with their own input automatically
removed.
Foldback is a term used to refer to audio mixes used to feed communications systems, usually from control rooms into
studios, to allow presenters and performers to hear all audio content which is relevant to them.

Why remove a source's own input from its foldback mix?

Scenario one: Field reporters or presenters communicating via long distance systems e.g. satellite links.
Field reporters need to hear a live mix of the program to which they are contributing in order to hear cues and
communicate with other presenters. The inherent delay in the system means that it may be a number of seconds before
the live audio stream reaches the reporter.
It can be very difficult to speak whilst hearing your own voice even with only a slight delay. Using an auto minus feed for
the reporter solves this problem as their own contribution to the audio mix is removed before it is fed to their headphones
or monitoring system.
Scenario Two: Eliminating feedback when using loudspeakers for communication.
If a presenter is monitoring their foldback feed using a loudspeaker, the sound from the loudspeaker signal may be picked
up by the presenter's microphone, thus creating a feedback loop. By using the auto minus bus to remove the presenter's
own contribution to the foldback bus, this feedback loop is broken.

Mix Minus Output

Each channel and group has a dedicated mix minus output available for patching to external communications devices to
create foldback feeds. Each mix minus output can be fed by either the auto minus bus, an aux or a track bus.
CALREC
Putting Sound in the Picture
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