Troubleshooting guide

Modular Processors
SHURE
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P4800 System Processor Software Guide Page 58 of 108
Basic DFR Setup
There are two basic ways in which to set-up the DFR to reduce feedback; the Ring-Out Method and
the Insurance Policy Method, as described below. Each is valid for different situations.
Note: The DFR (or any other notch filter system) helps reduce feedback, but cannot
entirely eliminate it. In a typical system, you reach a point of "diminishing returns"
after 4 to 8 notch filters are set. You can expect a 6 to 9 dB improvement of gain-
before-feedback in a typical system. To achieve greater sound system
performance, you may need to improve your sound environment.
§ Ring Out Method −
−−
− With this method, you use the DFR as a preemptive measure against
feedback for input channels that operate near the feedback point and need an extra
margin of stability. Using this method, you raise the input channel's gain beyond its
normal setting to deliberately make the system feed back. The DFR will then set the
proper filters. Then, when you reduce the input gain to an appropriate level, the system is
stable and useable.
§ Insurance Policy Method −
−−
− With this method, you use the DFR as added insurance
against unexpected feedback in an otherwise stable system. Simply placed the DFR
processor in the signal path, without defining any settings. This method is used for
systems which already have sufficient gain-before-feedback, but need protection from
occasional feedback occurrences due to non-stationary microphones or user-adjustable
gain controls.
To ring out the system:
1. Remove any active filters by clicking the [Clear] button.
2. Open all mics.
3. Monitor the DFR window while slowly increasing the system gain. As the DFR detects acoustic
feedback, it deploys new filters, indicated in the DFR window as yellow dots.
4. Continue to increase gain 3 to 6 dB beyond the gain level at which you will operate the system, or
until 4 to 8 filters have been deployed. Lower the gain 3 to 6 dB to the desired setting to stabilize
the system.
5. Allocate the deployed filters as "fixed" (see Fixed and Dynamic Filter Allocation on the following
page). The remaining dynamic filters will deploy as needed when the system is in use.
Note: You can copy the fixed filters to a PEQ block to allow for more dynamic filters in
the DFR window.
Hold Mode
By default, the DFR saves the state of all of its filters during a preset change or power cycle. However,
you can configure the DFR to clear certain filters when a power cycle or preset change occurs. After
setting all of the filters you want to be permanent, enable the hold mode. Any filters deployed after hold
mode has been selected will be cleared upon a preset change or power cycle.
To enable hold mode:
1. Ring out the system as described in the previous section.
2. Select the [Options>Hold Mode] menu command.