Polycom SoundStructure C16 Design Manual page 114

Design Guide for the Polycom SoundStructure C16, C12, C8, and SR12
C-Series Sound Reinforcement Input Processing
Mic or Line Analog A/D Parametric
Input Converter Equalization
Gain
Parametric
Equalization
5 - 32
Selecting the Edit button will open the equalization user control where param-
eters for the feedback eliminator may be specified as shown in the following
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
AGC Dynamics
Automatic Dynamics
Gain Control Processor
Automixer
Automatic Dynamics
Automixer
Gain Control Processor
Automatic Dynamics
Automixer
Gain Control Processor
Automatic Dynamics
Automixer
Processor
Gain Control
Fader Delay Mute
Input to
Fader Delay
Matrix
Input to
Fader Delay
Matrix
Input to
Fader Delay
Matrix
Fader Delay
Mute
Recording/
Ungated
Conferencing
Sound
Reinforcement