Backstage Technical Services | Sound Guide | Behringer DSP 1100P Feedback Destroyer

Sound Guide - Behringer DSP 1100P

Tutorials & Info --> Sound Guide --> Behringer DSP 1100P

Behringer Feedback Destroyer Pro DSP 1100P

Introduction

This piece of equipment is designed to prevent feedback and so is usually used in a monitor system. Made by Behringer, it is used between the desk and amplifiers or as an insert on a channel, cutting any loud frequencies which it receives. This filter is saved and operates to prevent and future feedback on that frequency. Unlike graphic equalisers, the frequency selection is very precise so the overall sound is affected as little as possible. It can operate on up to 12 frequencies per channel and can also be MIDI controlled as well as storing the settings in 10 different program slots.

The DSP 1100 operates over two channels, which can be modified separately (mono) or together (stereo) and can be set to continually search for feedback or use preset settings. This versatility, coupled with the ability to operate as a parametric EQ, allows the DSP 1100 to be used in a wide variety of conditions.

Things you need to look out for

A guitar player may want to produce feedback but the DSP 1100 won't be able to distinguish between wanted and unwanted feedback, simply cutting it all out. Think carefully about what mode you use and where you connect up the feedback destroyer.

A basic users guide

The manual for this device is pretty difficult to decipher, so here's a shortened translation of how to use the Feedback Destroyer.

Connect so that it can recieve and send a signal back somewhere apropriate
Errm, switch on
If all the red LEDs start flashing, the Feedback destroyer is searching for feedback on all filters in both channels. So if you start producing feedback, it will now start to cut it out, saving each filter in turn.

The DSP 1100's filters can operate in one of three modes:

Mode	Display	Description
Auto	AU	Continually searching for feedback. When feedback occurs, the DSP 1100 will use the next frequency filter (red horizontal LEDs) and will save the frequency cut in that filter. When all 12 filters are used, it will start back at the oldest filter, saving over the older setting. This mode is useful for singers moving about on stage and producing unpredictable feedback whilst on stage.
Single-shot	SI	Single frequency search. After a particular filter is set to SI mode, it will store the frequency and will stop searching, entering locked mode. This setting is useful for fixed instruments and microphones and the feedback destroyer can be set up during the sound check.
Locked	LI	The DSP 1100 has found a feedback frequency (after using single-shot mode) and is currently suppressing it. To get out of locked mode, change the filer mode to single-shot (SI).
Parametric EQ	PA	The filter is acting as an equaliser and can be manually altered by using the jog dial and the frequency, bandwidth and gain buttons.
Off	OF	The filter is currently not operating, to change this, select AU, SI or PA mode.

Each of the 2x12 LEDs represents a filter which operates on that particular channel.

Flashing	The filter is searching for feedback
On (Red)	The filter is operating, acting on a particular frequency.

To change one of the filters:

Press the FILTER SELECT button and use the jog dial to select which of the 12 filters you want to change
Select the channel you would like to change by pressing either ENGINE R or ENGINE L. Pressing both buttons together will affect both channels and is best used when working with stereo signals.
Press the FILTER MODE button and use the jog dial to select which mode you would like that filter to use.

Further information

Behringer Feedback Destroyer Pro DSP 1100P Manual (1,476k, PDF).

Backstage Technical Services, University of Bath Students' Union, Claverton Down, BATH, BA2 7AY
Generously supported by the University of Bath Alumni Fund.