Operate a live sound system 6 dB below the feedback threshold to maintain stable gain

Acoustic feedback occurs when the signal from the loudspeaker enters the microphone and is re-amplified in a loop, producing howling. The system reaches feedback when the loop gain equals or exceeds unity at some frequency. The handbook recommends operating 6 dB below the feedback onset as a safety margin. Operating closer than 6 dB risks feedback from mic movement, performer proximity to speakers, or room changes (temperature, crowd absorption). The margin also ensures that the audio quality remains relatively natural — operation near feedback imparts a ringing coloration even before full howl onset. Directional microphones and loudspeakers improve available gain before feedback.

Examples

Ring out the monitor system by slowly increasing gain until feedback begins (howling), then pull back 6 dB. Mark that position as the maximum working level. Further gain is available only if EQ notches suppress the feedback frequency.

Assessment

Why is the 6 dB margin not just a safety cushion but also a sound-quality requirement? What audible artifact appears between the 6 dB point and actual feedback onset?