Biamp LTR User Manual
Page 136
Nexia Manual LTR
Feed the "ambient" signal into the Ambient Input (bottom left, marked with an "A") of the
ANC block. This signal should be derived from either a single dedicated sensing
microphone, or from a dedicated array of sensing microphones feeding a common Mixer
block. Setup of the ANC block is best done when the ambient noise in the room(s) is
minimal, but the Ambient Meter should read at least -60dBu.
Connect the output of the ANC block to its destination. Keep in mind that the ANC
should be the last block in the program signal path, with no form of level control provided
at the outputs, amplifiers, or speakers.
Setting Min and Max Gain
Adjust the Min Gain and Max Gain settings for the desired amounts of minimum and
maximum gain to be applied to the program signal. Remember that Min Gain is the
constant gain that the ANC block will apply while the Ambient Input signal level is below
the Ambient Threshold. Remember that Max Gain is the maximum amount of gain that
the ANC block will ever apply to the program input.
If Min Gain and Max Gain are not known, these settings may be determined by listening to
the ANC output, as follows:
Set the Ambient Threshold to its maximum setting (+24dBu) to ensure the Ambient
Input level is below threshold. This ramps the ANC to the Min Gain setting. Keep in mind
that the speed of this ramping is determined by the Gain Time setting.
Adjust Min Gain until you have the desired minimum program level comining out of the
ANC block. Note this value for later.
Adjust Min Gain until you have the desired maximum program level coming out of the
ANC block. Set Max Gain to this value. Set Min Gain to the value determined in the
previous step.
Setting Response Times
Adjust the Gain Time to determine how quickly the ANC gain changes. Gain Time is the
amount of time it takes for the ANC block to ramp from Gain Min to Gain Max, or vice
versa.
Adjust the Ambient Response time to determine how quickly the Ambient Input detector
responds to changes in the Ambient Input signal. Ambient Response should be set fast
enough to track important ambient level changes (e.g. an approaching train in a depot),
but slow enough to ignore unimportant ambient level changes (e.g. someone popping
their bubble gum).
Note:
The overall responsiveness of the ANC output is determined by the larger (slower) of
the two aforementioned times: Gain Time and Ambient Response time.
Setting Thresholds
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