Six methods to solve microphone howling, from simple to professional equalizer debugging step by step teaching (part one)

Shang Yan, wedding, campus party, KTV, the most collapse of the scene accident, nothing more than the microphone opened the moment sharp whistle, light to interrupt the performance, harsh ear injury, but also instantly burned loudspeakers. 90% practitioners will only blindly lower the volume, which will not only lose the loudness of human voices, but also treat the symptoms rather than the root cause. In this paper, according to zero-cost simple operation → basic setting of mixer → balanced debugging and sorting of professional hardware, six schemes are upgraded step by step, from temporary first aid to long-term radical coverage, which can be directly applied by novices, resident singers and full-time Andhadhun.

Understand first: how did the howling come about?
Core principle: sound positive feedback closed-loop microphone picks up the sound emitted by the speaker → the signal is amplified by the mixer and power amplifier → the speaker plays the same-frequency sound wave again → the microphone repeatedly picks up the cyclic superposition, and when the gain exceeds the critical value, it will burst into a shrill scream. High-frequency 2kHz-8kHz is the most sensitive and easily triggered howling frequency band for human ears; Closed empty rooms, a lot of glass on the wall, and the microphone facing the speaker will double the howling problem.

Part I: 3 sets of zero-cost simple schemes (no equipment, first aid for novices, priority)
Method 1: physically cut off the feedback path (radical basis, the first step in all scenarios)
No need to adjust any knob, it will take effect in 10 seconds at the scene, which can directly reduce the howling probability by 60%.

1, speaker placement rules
The main amplifier is raised towards the audience, and it is forbidden for the treble unit to face the stage microphone area; The stage echo speaker is inclined to the actor's feet, so don't aim at the microphone pickup.
2, microphone use specification
When singing and speaking, the microphone is close to the mouth (2-5cm away), so there is no need to raise the gain when the sound source is close; It is forbidden to point the microphone at the speaker and listen to the speaker test.
3. Distance safety threshold
The horizontal distance between the microphone and the speaker in the small banquet hall is ≥ 3m; Outdoor, auditorium ≥5 meters, the noise reduction effect of horizontal distance is much greater than the vertical height.
4. Low-cost acoustic optimization
The wall and glass of the empty room have strong reflection, and carpets and curtains are temporarily laid to reduce the reflection of sound waves back and forth to form secondary feedback.

Method 2: Control the gain and volume to prevent the system from entering critical self-excitation.
Many people push the microphone fader and turn up the treble crazily for the sake of loud voice. The system has been at the critical point of howling for a long time, and it will explode when the environment changes slightly. Practical steps:

1. All human voice microphone faders are reset to zero, and the main output volume of the power amplifier is first pulled to 1/3;
2. Speak and sing normally, slowly push the fader in the microphone channel, and immediately fall back by 20% at the first sharp sound;
3. The volume used on site should always be controlled within 80% of the critical howling volume, and a safety margin should be reserved;
4. When multiple microphones are turned on at the same time, the overall main volume will be reduced by 3-5dB for each additional microphone, and the superposition of multiple microphones will easily trigger feedback.

Method 3: attenuation of basic timbre of microphone channel (mixer comes with knob and no extra equipment)
Each microphone in the mixer comes with three EQs of high, middle and low, which can weaken the easy-to-scream frequency band without professional equalizer.

1. turn on Qualcomm HPF(80Hz low cut).
All vocal microphones must turn on the 80Hz high-pass filter, cut off the floor and wall resonance low frequency, reduce the hidden feedback caused by low-frequency resonance, and at the same time, the human voice is cleaner and not turbid.
2, moderate attenuation high frequency knob
Reduce the TREBLE of the channel by 1-3 squares. The high frequency of 2-6kHz is the hardest hit area for howling. A small attenuation will not lose the clarity of human voice, but it can greatly suppress the screeching.
3, reduce excessive reverberation
The greater the reverberation, the more delayed reflections of sound, and the easier it is to howl; The total reverberation of the performance voice is controlled at 20%-35%, and it is directly halved when the howling is serious.