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ULTRACURVE PRO DEQ2496 User Manual

The first page shows a graphic representation of the filters. It is structured and 

operated in the same way as the first page in the PEQ menu. Since this menu 

can only be used to cut signals, the 0 dB line is located in the upper part of the 

display. The differences here are the settings ranges for the GAIN and BW(OCT) 

parameters. In order to achieve extremely narrow-band filters with high 

attenuation factors, the bandwidth ranges from 1/10 to 1/60 oct. and the GAIN 

from 0 to -60 dB.

◊ 

At least one filter must be activated on page 2 to be able to access the 
first page of the FBD menu.

Fig. 3.9: FBD menu (page 2)

Page 2 provides a table showing the ten memory locations available. 

If parametric EQs have been activated in the PEQ menu, these will be shown here 

too, because the memory locations are intended for both FBD and PEQ settings. 

◊ 

Any parametric EQs activated in the PEQ module cannot be edited in 
the Feedback Destroyer menu (FBD)—and vice versa.

In general, you can select two types of feedback filters: SNGL mode (single shot) 

and AUTO mode. To be able to identify feedback frequencies, the Feedback 

Destroyer splits up the entire frequency spectrum (20 Hz to 20 kHz) into bands of 

1/60 octave and measures their respective levels. The resulting values are then 

referenced to the level of the complete signal. The difference between these 

levels determines whether a filter is activated or not. As soon as a filter is set 

to AUTO or SNGL mode, the unit automatically tracks feedback frequencies and 

assigns the active filters to them.

AUTO mode

Microphones that are moved around during a performance (e.g. vocal mics) 

often suffer from varying feedback frequencies as a result of the changing 

positions on stage. This kind of feedback is best suppressed in AUTO mode. 

A filter in AUTO mode automatically identifies the optimum parameter settings 

for feedback suppression. If the feedback frequencies change, the AUTO filter 

can track them and keep suppressing them. It always selects the respective 

frequencies and a very narrow-band filter configuration to affect the wanted 

signal as little as possible. When all filters are locked in to a specific frequency, 

and a “new” feedback frequency occurs, then the filter with the “oldest” or 

first feedback frequency detected is released and used for the new one. If new 

feedback occurs very close to or even at an already identified frequency, 

the parameters of the filter already in use will be adapted, for example by 

widening its bandwidth or raising the amount of signal attenuation.

SNGL mode

Filters in SNGL mode (single shot) also searches feedbacks automatically. 

If feedback is identified, the filter parameters are configured optimally for 

feedback suppression. Contrary to filters in AUTO mode, filters in SNGL mode lock 

in firmly to the identified frequency (LOCK FBD), however, their width and depth 

are still being adapted to changes in the feedback frequencies. The bandwidth is 

enlarged, if the feedback frequency shifts slightly, and the amount of attenuation 

is raised if feedback persists. To prevent a feedback frequency from recurring, 

the amount of attenuation is not reduced. Thus, SNGL mode is ideally suited to 

suppress constant feedback frequencies, as they are typically produced by fixed 

or permanently installed microphones.
Use the 

LOCK FBD

 function (B key in the left bottom part of the display) to lock 

the frequency of the SNGL filter manually (SNGL 



). This means that the filter can 

only be modified in its bandwidth and amount of attenuation. With UNLOCK FBD 

(B key) it can be unlocked again.

Fig. 3.10: FBD menu (page 3)

The third page provides three additional dynamics parameters for all FBD filters. 

SENS

 (upper data wheel) allows you to determine the point of onset for feedback 

suppression (describes the difference between feedback signal and overall 

level). When a signal reaches this difference, it gets reduced in level. The setting 

range here is from -3.0 to -9.0 dB. Use 

THRESHOLD

 (large data wheel) to select 

the threshold from which a certain frequency is considered to be feedback. 

The 

MAX. DEPTH

 parameter below determines the maximum attenuation of a 

filter (-18 to -60 dB) in 6 dB steps, and thus the GAIN setting range as displayed 

on the first and second page (lower data wheel). 

LEARN MODE

 is activated with the A key. This function generates additional 

short pulses and raises the overall gain to provoke feedback. Subsequently, 

the feedback signals arrive at the input of the DEQ2496, are identified and 

suppressed. LEARN MODE is ideal for use before a live event, for example to 

automatically configure the SNGL filters (“tuning-in” of a P.A. system).
The following symbols inform you about the current status of the filters:



   In this setting, an AUTO or SNGL filter is “on duty” (RUN) to react to the 

incoming signal and effect the necessary settings.



   This symbol refers to an AUTO or SNGL filter (SNGL filter in LOCK mode), 

which is currently suppressing an identified feedback frequency.



   This symbol indicates that the AUTO and SNGL filters are in STOP mode. 

The settings already made remain active. However, “new” feedback 

frequencies are not eliminated.



   This symbol refers to the filter assigned to the last feedback 

frequency identified.

The selection and editing of parameters is largely the same as in the 

PEQ menu, one exception being the B key: With a long key press you can 

reset all filters (menu page 2) or just the AUTO filters (menu page 3).

3.3  WIDTH menu

The WIDTH function gives you a stereo imager for processing stereo signals and is 

active in stereo LINK mode only.
A signal whose stereo basis has been enlarged sounds much more interesting, 

because you can hear more pronounced differences between the two stereo 

sides. If used moderately, a stereo imager can clearly enhance the overall 

impression of your music.
On both pages of the WIDTH menu, the parameters to be edited appear on 

the right-hand side. On the left you’ll find the RESET IMAGE-function (B key), 

which allows you to undo the previously made entries by means of a long key 

press. In the center of the display, a diagram shows both the stereo width of 

the signal (triangle) and the mono signal (line).

Fig. 3.11: WIDTH menu (page 1)