Polycom SoundStructure C16 Design Manual page 133

● 10 parametric equalizers
Submix Equalization Process
To enable a filter, click the check box next to the filter. This makes the filter the active filter and allows the
parameters to be changed as shown next.
The cut off frequency can be adjusted between 0 Hz and 20,000 Hz, the order can be adjusted from 2
th
8 , and either a Butterworth or Linkwitz-Riley filter may be selected.
For each of the 1 parametric filters, the designer can choose from:
● Parametric filter
● Notch filter
● Allpass filter
Parametric filters emphasize or de-emphasize the center frequency with a gain and bandwidth setting. The
user can specify the bandwidth (in octaves), center frequency (in Hz), and gain (from 0 to 20 dB).
Notch filters eliminate energy (attenuate only) at the center frequency. The amount of attenuation for the
signal is determined by the bandwidth (in octaves) selected. The bandwidth is defined as where the gain is
-3 dB.
Allpass filters do not modify the gain of the signal, but change the phase. For a second order allpass filter,
the phase shift is 0 degrees at 0 Hz, 360 degrees at high frequencies, and 180 degrees at the center
frequency. The bandwidth is defined as the bandwidth (in octaves) where the phase shift is 90 degrees and
270 degrees.
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