Using the S curve 131 to Remove Feedback
One of the most important applications for the S curve 131 is removing feedback from an onstage monitor system. This procedure is sometimes called “ringing out,” since feedback usually begins with a slight ringing sound at the resonant frequencies where the loop between microphone and speaker is loudest. The advanced Constant Q circuitry ensures that adjacent program frequencies which may not be causing any problems are unaffected even when attenuating problem frequencies by their maximum amount.
To ring out a monitor system, start by setting up the stage exactly as it will be used during perfor- mance, preferably with the performers themselves standing in front of the mics they will be using (this is important since the physical placement of
Next, power up all audio equipment (turning on the amplifiers last) and, using one monitor output only, gradually turn up the volume while a performer is speaking or singing into the primary mic for that monitor. Continue slowly increasing the volume until a feedback howl just begins. Using your ears or an RTA (Real Time Analyzer), identify the approximate frequency at which this feedback occurs. Lower the corresponding Equalizer slider until the feedback disappears. Then continue slowly turning up the volume until another feedback howl just begins. Again identify the approximate frequency of this feedback and lower the corresponding Equalizer slider until the feedback disap- pears. Repeat this procedure until you reach the point where many different frequencies begin to feedback at once or when you find that you’ve already attenuated most of the feedback frequencies that are occurring. This is the point at which the process
When done successfully, “ringing out” (which should be done before every performance) can add another 3 to 15 dB more of usable gain to your monitor
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