View "Fbc; Static Filters - Monacor DRM-884DTM Instruction Manual

7.10 View "FBC" (fig . 24)
The FBC function is used to automatically suppress feedback noise .
Feedback noise may occur when a speaker signal is picked up by a
microphone, amplified and reproduced again by the same speaker .
When setting up microphones, always make sure that a microphone
is not directed towards a speaker or placed too close to the speaker .
Feedback noise is often an annoying and loud howling . The FBC func-
tion will automatically detect feedback frequencies and systematically
attenuate these frequencies by using up to 24 notch filters .
The FBC channel is in parallel to the connections defined in the
view "Matrix" . The inputs and outputs designed for the FBC function
must therefore not be interconnected in the view "Matrix" .
The view "FBC" (fig . 24) offers the following options:
[58] "FBC Input Select"
input channels of microphones whose signals are routed via the
FBC channel to automatically suppress feedback noise
"Local Input":
1 – 8 are analog inputs of DRM-884
9 – 12 are inputs of extension modules
"Network Input" are the inputs of the Dante interface (Dante
receiver) and only available when the extension module DRM-
884DTM has been installed .
[59] "FBC Output Assign"
output channels to the speakers involved in feedback
"Local Output":
1 – 8 are analog outputs of DRM-884
9 – 12 are outputs of extension modules
"Network Output" are the outputs of the Dante interface (Dante
transmitter) and only available when the extension module DRM-
884DTM has been installed .
[60] "FBC Mode": type of signal
Speech
Music
[61] "Filter Release": release time of the dynamic filters
Fast
Mid
Slow
[58]
[63] [64]
[67]
Fig. 24 View "FBC"
40
[60] [61]
[65] [66]
[62] curve representation of the filters in amplitude frequency response
[63] "Static Filter Setup" to set up static filters (
[64] "Clear Dynamic Filters" to delete all dynamic filters
[65] "Clear All Filters" to delete all dynamic and static filters
[66] "Bypass" to deactivate the FBC function
[67] indication of the filters set up:
red = static filter
green = dynamic filter
Example: An announcement via a microphone at the input IN 03 is to be
reproduced by a speaker at the output OUT 04 . The FBC function is used to
prevent feedback:
In the view "Matrix", deactivate the connection (the intersection point of row
IN 03 and column OUT 04 is grey) .
In the view "FBC", activate (green) the "3" of "Local Input" [58] and the "4"
of "Local Output" [59] .

7.10.1 Static filters

Usually, the filters for the feedback frequencies found are set up
dynamically, i . e . when there is feedback during operation (for
example because the person speaking into the microphone holds the
microphone too close to a speaker), a filter will be set up automatically
and deleted after the time defined . In some cases, however, it may
be desirable to find the frequencies that tend to cause feedback in
this combination of room and amplifier system before the event and
to set up static filters to prevent feedback . The function "Static Filter
Setup" can be used for this:
1) Set the levels of the corresponding inputs and outputs to the values
☞
intended ( chapter 7 .6) .
2) Activate the function "Static Filter Setup" [63] . The additional slider
control shown in figure 25 will appear .
3) To increase the gain, carefully set the slider control to the right
until feedback starts . The first filter will be set up automatically and
suppress feedback . On the filter indication [67], the filter is red . It
also appears on the frequency curve [62] .
4) Set the control further to the right until the next feedback starts .
Proceed in the same way to set up further filters, if required .
5) Deactivate the function "Static Filter Setup" [63] . The red fields in
the filter indication [67] show the static filters that have been set up .
[59]
[62]
☞
chapter 7 .10 .1)