Polycom SoundStructure C16 Design Manual page 476

Design Guide for the Polycom SoundStructure C16, C12, C8, and SR12
On the channels page, set the AEC reference for all the Room 1 microphones
as "Amplifier 1" and for the room 2 microphones as "Amplifier 2" as shown
in the following figure.
The routing for Room 2 is done in the matrix without use of the submixes to
make it easier to mute or unmute different crosspoints depending on the room
combine state. Another approach would have been to create additional sub-
mixes for the Room 2 microphones and loudspeaker outputs.
Once the matrix settings are configured, the next step is to save these settings
to the "Combine" preset by selecting "Save To New" on the preset page and
set the power on preset to be the "Combine" preset.
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