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About the AFB Mode
The AFB mode uses a filter with an extremely high Q to
eliminate feedback (howling) occurring in a sound rein-
forcement system that uses a microphone, and keep fluctu-
ations in the sound quality to a minimum.
The AFB mode performs compensation to minimize fluctu-
ations in sound quality, but this does not mean that no
changes at all occur in the sound quality. As the number of
points at which feedback-suppression points increases, the
sound quality also gradually changes. Fluctuations in
sound quality can be kept to a minimum by using the AFB
mode after first positioning the sound reinforcement device
so as to reduce the chance of feedback occurring.
Functions of the AFB Mode
The AFB mode offers the following functions for eliminat-
ing feedback.
e Auto Function
This function is suited to eliminating feedback during
sound checks.
The Auto function automatically searches for the feedback
point (the frequency at which feedback occurs), and sets
up a filter to correct the frequency response at that point
and eliminate feedback.
¢Dynamic Function
This function eliminates sudden feedback occurring
because of changes in the sound production environment,
or other factors such as the microphone being moved. Like
the Auto function, the Dynamic function is automatic.
¢Manual Function
The Manual function can be used to switch filters on or off.
e Diffuse Function
The Diffuse function applies slow, inaudible modulation to
suppress feedback and coloration.
This function is particularly effective in suppressing feed-
back and coloration in the treble range.
e Mute Function
The Mute function can be switched on when you want to
lower the output level. Parameters for setting the mute
level are available.
In addition to these five functions, the AFB mode also
offers the following functions.
e Spectrum Analyzer
This works as a 91-band analyzer, showing the frequency
response of the input sound on the display. Zoom and
Scroll can be used to switch the frequency range or level
being monitored.
eHigh-Pass Filter (HPF) and Low-Pass Filter
(LPF) Settings
These allow the AFB mode to be used more effectively in
the required frequency bands by cutting unnecessary fre-
quency bands.
About the Display on the Analyzer/Filter
Screen
The following information appears on the Analyzer/Filter
screen for the AFB mode.
"AUTO": The Auto function is in operation
"DYNA": The Dynamic function is in operation
"AFB":
A function other than the foregoing
v
two is in operation (AFB mode)
TAFE |
PEAK EL. OOKHz
Cidta:
4749
FILT
Leve
o
(dB) || -12
"24
100
200
S00
ik
2k
Sk
10k 20k
= ———_
OS
Frequency (Hz)
"AUTO"
Example: A-1 1.00 kHz -3.0 dBm 13/14
Filters set by the Auto function, and numbers
of remaining/reserve filters
"DYNA"
Example: D-1 1.00 kHz -3.0 dBm 3/4
Filters set by the Auto function, and numbers
of remaining/reserve filters
"AFB"
Example: PEAK 1.00 kHz [14/14 : 4/4]
Peak point and numbers of
remaining/reserve filters(Auto: Dynamic)
5k
ik 20k
Frequency (Hz)
Peak Point
1
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