Polycom SoundStructure C16 Design Manual page 111

C-Series Sound Reinforcement Input Processing
Mic or Line A/D Parametric
Analog
Converter
Input Gain Equalization
Parametric
Equalization
figure.
There is a safe mode attenuation that defines the amount of attenuation that
can be applied to the signal if the feedback eliminator filters are all engaged
and there is still feedback. The safe mode attenuation can be set from 0 to 20
dB of attenuation and has a default value is 3 dB.
The Filter Decay control allows the adaptive filters to relax as the feedback is
reduced in the system.
During operation, if there are persistent frequencies which appear, the filter
settings from those offending frequencies can be made fixed by clicking on the
Make Fixed control. This will transfer the settings of the adaptive filter to one
of the fixed parametric filters.
To utilize the feedback processing, the feedback processing must be enabled
on the EQ page for the desired inputs and the sound reinforcement signal pro-
cessing path must be selected. Recall that the input processing has different
types of audio processing available for the input signals. The sound reinforce-
ment signal path for the C-series products is shown in the following figure.
Non Linear
Acoustic Echo Noise
Processing
Cancellation Cancellation
Feedback
Cancellation
Acoustic Echo Noise Feedback
Cancellation Cancellation Cancellation
The sound reinforcement signal path is selected at the matrix crosspoint by
AGC Dynamics
Automatic Dynamics
Gain Control Processor
Router
Automixer
Automatic Dynamics
Automixer
Processor
Gain Control
Automatic Dynamics
Automixer
Gain Control Processor
Automatic Dynamics
Gain Control Processor
Customizing SoundStructure Designs
Fader Delay Mute
Fader Delay
Fader Delay
Fader Delay
Automixer Fader Delay
Input to
Recording/
Matrix
Ungated
Input to
Conferencing
Matrix
Sound
Input to
Matrix Reinforcement
Mute
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