13
FEEDBACK DESTROYER PRO DSP1124P
5. DSP1124P ARCHITECTURE: PRESETS, FILTERS, OPERATING
MODES
In order to avoid confusion, let us give you a concise description of the DSP1124Ps operating principle, so as
to make the three relevant points clear right from the start. Example: You have set up your P.A. system and
connected all signal sources to the console. The DSP1124P has been inserted into the monitor path (see
fig. 2.1) or in single channel or sub-group inserts (see fig. 2.2); after power-up preset 1 was loaded with the
JOG WHEEL. Now, you can start to purposefully produce feedback, as described in chapter 3. Depending on
the room acoustics, various feedback frequencies can occur. What exactly does the DSP1124P do?
As can be seen from table 11.3, each of the ten presets on your DSP1124P comprises 24 separate filters,
which can, however, be set to different operating modes: In our example, the first nine filters of the selected
preset are set to
Single-Shot
mode (SI, see chapter 6.3). This mode is designed to detect feedback
frequencies at fixed resonance values, and to suppress them consistently. So, these filters cannot be
unlocked (status LO (locked)). Their bandwidth and gain reduction can be adapted if required, however, the
frequency setting remains the same. In our example, the DSP1124P is used to prevent nine fixed frequencies
from making trouble.
The three remaining filters (all set to
Auto
mode AU, see chapter 6.3) are used to detect and suppress new
feedback frequencies, which can be produced, e.g. when the singer moves around the stage with the vocal mic
in his/her hand. Since the DSP1124P can by no means know whether or not the risk of feedback has been
eliminated (e.g. when the singer moves to another position), the first AU filter of the unit locks to the detected
frequency, while the remaining two AU filters are used to suppress any new trouble frequencies that may
occur. Only when all AU filters have been used, will the first AU filter used (here: 10) be unlocked, so as to be
able to detect new feedback frequencies.
Basically, all active filters (both in AU or SI mode) are represented by flashing LEDs in the STATUS
INDICATOR
. When feedback has been detected and is being suppressed, the associated filter LED lights
up constantly. Filters set to
Parametric EQ
mode (see chapter 6.2) also have constantly lit LEDs.
+
Please read the detailed description of all operating modes (chapter 6)!
5.1 Priming the DSP1124P for P.A. and monitor applications
With the DSP1124P you can improve the protection against feedback even before the show begins, by tuning
in your sound reinforcement system. We already dealt with this in chapter 3. But now its not about using a
preset, but about how to determine in which modes the filters are used: Set some of the filters to
Single-Shot
mode (see
).
First, lets take a look at the monitor path: Open all microphone channels, turn up the Aux Send controls on all
channels you wish to route to the monitor mix, then slowly move up the monitor master faders. For the front
mix do as follows: Slowly move up the channel and master faders. In both cases, the first feedback frequencies
can be heard after some time.
Without the FEEDBACK DESTROYER PRO you could not increase the volume level of your system any
further. With the DSP1124P, however, you can considerably enhance the system headroom! Let the
Single-Shot
filters on the DSP1124P suppress feedback as it occurs. Then cut back the volume to the level
required for the show. In this way, you can be sure that there is enough system headroom should it become
necessary to raise the volume level during the concert.
Experience has shown that musicians want to have the volume of their instrument increased on the monitor as
the concert goes on. With the FEEDBACK DESTROYER PRO you can turn up the volume without having to
fear feedback problems. When the show begins you should set several filters to
Auto
mode, in order to
suppress feedback produced by moving (vocal) microphones. More information on
Auto
mode can be found
in chapters 5 and 6.3.
5. DSP1124P ARCHITECTURE: PRESETS, FILTERS, OPERATING MODES
Downloaded from www.g7syw.com
www.g7syw.com
