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Operating Manual - nX, nXe, and nXp Power Amplifiers
ANC Setup Procedure
1) In the control software, assign the ANC function to the channel to be used for background music or voice paging
(program audio). Set the ANC controls to the "typical" settings described above, which is also the default settings of a new ANC
function when it is first placed in the signal processing block.
2) Open the ANC control window and select the noise-sensing microphone input channel in the drop-down box labeled
Mixer Input Channel.
3) Physically locate the noise-sensing microphone in the room by pointing it toward the noise sources such as groups
of people talking, HVAC equipment etc., yet pointed away from the sound system speakers.
4) Add microphone preamp gain (external preamp) and level control functions (software) on the noise-sensing mi-
crophone signal path before the matrix mixer and adjust the microphone gain so that you can see the ambient noise input level
meter start to show a level when the room noise starts to increase. To adjust the ANC controls for good-sounding operation
without people present, a pink noise source or even a boom box can be used placed near the expected noise location to simulate
the expected noise.
5) Adjust the ANC's Noise Threshold control to the ambient noise input level at which you would like the program
audio gain to start to increase. Increase the room noise source so that you see the ambient noise input level meter rise above
your Noise Threshold setting. You should see the Program Audio Gain meter slowly rise above the Min Gain setting.
6) Slowly increase the noise source and adjust the Program/Ambient Gain Ratio for the desired amount of noise
compensation.
7) Continue to increase the noise source to the highest level you would expect. Adjust the Max Gain to a level which
limits the maximum gain which the ANC applies to the program audio so that it will not become too loud or clip.
8) The Gain Change Rate can be adjusted according to how fast you would like the gain changes to take place in
response to changes in ambient noise.
9) Be aware that an improperly setup ANC can result in runaway gain where the program audio is picked-up by the
noise-sensing microphone as background noise. The result is not necessarily feedback squeals, but the gain of the program audio
could ramp up to the Max Gain value even with no ambient room noise. Usually the best remedy for this problem is to locate the
noise-sensing microphone closer to the expected noise sources and further away from the sound system speakers. Sometimes
a baffle may be helpful, located between the speaker and microphone to block direct sound pickup. Also, the ANC Program/
Ambient Gain Ratio can be lowered to reduce the susceptibility to gain runaway.
2)
Gain
Functions
Gain
The Gain block allows the user to modify a signal's level by either applying gain
or attenuation. The Polarity of the signal may also be inverted. The Level control allows
for gain adjustment b12db and -50dB and OFF. The LEVEL fader can be adjusted
in 0.5dB increments. Finer adjustment (0.1 dB increments) may be made by typing in the
value into the provided text box below the fader.
The Gain block may be Linked with any other Gain block via Protea
ne
Software. This will
force all parameters (level and polarity) to be the same across the Linked blocks. Note that
changes to a Linked Gain block do not affect a VCA Gain block.
For a more powerful linking of gains consider using the Gain with VCA block.
Parameters
Level
- Off, -50dB to +12dB in 0.1dB increments
Polarity
- Normal or Inverted.
