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FEEDBACK DESTROYER PRO DSP1124P
6. OPERATING MODES OF THE DSP1124P
The individual filters on the BEHRINGER FEEDBACK DESTROYER PRO can operate in four different modes
(see
). An additional mode called Locked mode will be described specifically.
Basically, each of the
2 x 12 filters on the DSP1124P can be set to any of the four operating modes.
To meet more complex
requirements with regard to flexible signal processing, these modes can be combined in a program and stored
in a preset.
6.1 Off mode OF
In
Off
mode, the corresponding filter is deactivated and can be activated by selecting one of the modes
described below.
6.2 Manual filters (PA) / parametric equalizer
To raise or lower specific frequencies in level, you can select these frequencies directly by setting the manual
filters to
Parametric EQ
mode. Each filter has the functionality of a fully parametric EQ, i.e. you can set the
center frequency (FREQUENCY key
), the bandwidth (BANDWIDTH key
) and the amount of boost/cut
(in dB) using the GAIN key
.
6.3 Automatic filters (SI and AU)
Automatic filters operate in two modes:
Single-Shot
(SI) and
Auto
mode (AU). In order to find a feedback
frequency, the FEEDBACK DESTROYER PRO divides the entire frequency band into 1/60 octave steps
(20 Hz to 20 kHz) and determines the respective level of these individual bands. The unit then compares this
value to the level of the entire signal. The difference between these levels determines whether a filter is set or
not. The FEEDBACK DESTROYER PRO gives you the unique possibility of adapting this parameter according
to your own needs. You can edit the feedback sensitivity (i.e. the difference value) within a range from -3 to
-9 dB, in 1-dB steps: Simultaneously press the FILTER MODE and GAIN keys, then use the JOG WHEEL to
select a value. The standard value for this parameter is -6 dB, which provides for an optimum detection of
feedback in most applications.
Example: During a pure speech transmission, the feedback sensitivity can be lowered to -9 dB. In this way, the
algorithm would recognize and suppress feedback even faster. On the other hand, a higher setting, e.g. -3 dB,
allows you to leave those signals unaffected which you dont want to suppress (e.g. guitar or keyboard
signals).
Filters in
Single-Shot
mode automatically analyze the music signal to detect feedback frequencies. Having
detected such a frequency, the filter automatically configures its parameters to suppress feedback as
efficiently as possible. As the filter is locked to the detected frequency, this mode is ideally suited to suppress
feedback of constant frequency. Possible applications are fixed-position microphones (e.g. on the drums).
After the filter has adjusted itself automatically, it enters a special
Locked
mode (see chapter 6.4), which
means that although the frequency remains fixed, the width and depth of the filter are still being adapted to the
feedback frequency, i.e. the width is increased as soon as the feedback frequency begins to shift, and the gain
is cut if feedback prevails. The gain is not reduced to prevent feedback from recurring.
All microphones that are moved during a performance (e.g. vocal mics) very often have varying feedback
frequencies. This type of feedback should be suppressed in
Auto
mode. As in
Single-Shot
mode, the filter
automatically selects an ideal setting for feedback suppression. However, in Auto mode the first AU filter set is
unlocked to suppress new feedback. The optimum frequency is selected automatically and the filter is set to
narrow-band mode, so as to influence the music signal as little as possible. If your music contains wanted
feedback elements (e.g. guitar feedback), it is highly probable that these will be suppressed too in Auto mode,
because it is impossible from a physical point of view to distinguish wanted from unwanted feedback.
Please read chapter 2.3 to find some information on how to work around this situation.
6. OPERATING MODES OF THE DSP1124P
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