What causes feedback and how do I stop it?
Quick answer
Feedback occurs when a microphone picks up sound from a speaker, creating a loop that amplifies a specific frequency. To stop it, reduce microphone gain, move mics away from speakers, and use EQ to cut the offending frequency.
Feedback is caused by an acoustic loop: sound from a loudspeaker enters a microphone, gets re-amplified, and repeats, building up at a resonant frequency. This typically happens when the microphone is too close to the speaker or the gain is too high. Room acoustics, such as reflective surfaces, can worsen it.
To stop feedback immediately, lower the microphone volume or mute it. For prevention, position microphones behind the main speakers (using the speaker's null) and keep them close to the sound source. Use a graphic or parametric EQ to identify and notch out the feedback frequency—cut 3–6 dB at that band. SSOUNDS DSP systems include feedback suppression tools that automatically detect and notch problematic frequencies.
For permanent solutions, invest in directional microphones (cardioid or hypercardioid) and proper system tuning. SSOUNDS line arrays and point-source systems are designed with controlled directivity to minimize spill into microphones. Always ring out the system before a show by slowly raising gain until feedback occurs, then EQ it out.
Key things to consider
- Feedback is a loop: mic picks up speaker sound, re-amplifies it, builds at one frequency.
- Immediate fix: reduce gain or mute the offending mic.
- Prevent by placing mics behind speakers and using directional mics.
- Use EQ to notch out feedback frequencies (cut, not boost).
- SSOUNDS DSP offers automatic feedback suppression for quick tuning.
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