Six methods to solve microphone howling, from simple to professional equalizer debugging step by step teaching (part 2)

he second part: advanced professional scheme (performance standard, equalizer step-by-step practical teaching)
Method 4: Graphic equalizer EQ sweep frequency suppression (31-segment equalization universal, full-text core step-by-step tutorial)
Suitable for fixing banquet halls, bars and indoor theatres, it is Andhadhun's core skill to restrain howling for a long time without sacrificing the overall volume.

Preposition
1, empty the stage, on-site open-pit debugging (sound absorption by the audience will change the frequency point, and open-pit debugging will reserve a safety amount);
2. Turn off all effectors and feedback suppressors, except the vocal microphone channel;
3. The microphone is placed in the standing position commonly used in the performance, and the power amplifier and microphone fader are slowly pushed to the critical point where they are about to whistle.

Complete sweep attenuation step
1. Slowly increase the volume of the main output until a single sharp whistle appears in the field, and immediately stop the volume knob;
2. Slide 31 balanced faders left and right, and pull them up and down one by one, and find the fader whose howling is obviously weakened/disappeared after pulling. This frequency point is the feedback peak;
3. The frequency point attenuates downward by 3-6dB, and it is forbidden to attenuate it by more than 8dB at one time. Excessive attenuation will make people's voice dry and stuffy;
4. Continue to increase the main volume, wait for the next howling frequency point to appear, repeat the previous operation, and mark 3-5 feedback peaks at most;
5. After the attenuation of all frequency points is completed, increase the overall volume by 15%-25%. At this time, the system is stable and does not howl, and the loudness is greatly improved;
6. Fine-tune and balance the high and low frequencies, make up for the lack of transparency of human voice, and finally turn on the reverberation and the effect device for normal performance.

High frequency knowledge point
Reference of fixed frequency point for whistling in conventional site:

1. Intermediate frequency howling: 1.6kHz, 2.5kHz (human voice with teeth, harsh ears)
2, high-frequency scream: 4kHz, 6.3kHz, 8kHz (sharp metal sound, the most common)
3, low-frequency muffled noise: 125Hz, 250Hz (resonant roar of closed empty room)

Method 5: Automatic feedback suppressor can prevent noise with one button (Shang Yan and wedding mobile devices are preferred).
Aiming at the mobile performance and multi-microphone rapid debugging scene, the automatic frequency sweep captures the howling point, and the novice has zero threshold.

1. Equipment link connection: main output of mixer → input of feedback suppressor → equalizer → power amplifier;
2. All microphones are turned on and the volume is pushed to the normal performance loudness;
3. Turn on the "automatic detection/AUTO FEEDBACK" mode of the equipment, and let it stand for 30 seconds to complete the full-field frequency scanning;
4. The device will automatically generate narrow-band notch points and lock the feedback frequency points, which will not damage the vocal quality in a large area;
5. Note: large-scale music festivals and band performances should not rely on the automatic mode of the suppressor. Automatic notch trapping will lose the high-frequency details of the instrument, so manual balanced debugging is preferred.

Method 6: Acoustic reconstruction+directional microphone optimization (long-term stadium radical plan)
The first five are all electronic debugging methods. In order to eliminate howling from the root, optimizing the pickup and sound field environment is the ultimate solution.

1. Replace the cardioid/hypercardiac directional microphone.
Heart-shaped microphone has extremely strong attenuation of pickup on the back and side, which can greatly isolate the sound of the speaker from the rear, and double the howling prevention ability of omnidirectional microphone. Super-heart-shaped microphone is preferred for stage vocal microphone.
2. Optimization of stage echo system
Small narrow directional speakers for actors are selected and placed on the ground, covering only the foot area of the performer, reducing the volume of the microphone picking up and listening; If the budget is sufficient, the in-ear monitor can be replaced, and the ground echo can be cancelled directly, thus completely eliminating a source of howling.
3. Transformation of room acoustics.
Sound-absorbing sponge and diffuser are installed on the wall, and sound-absorbing curtains are attached to the glass doors and windows to reduce the hard reflection of sound waves; Add seats and green plants in the empty hall to increase the sound absorption volume and reduce the sound circulation reflection from the source.

On-site emergency summary (save mobile phone, perform rollover quick rescue)
1. The first time of sudden howling: lower the main volume+keep the microphone away from the speaker, and give priority to the physical method of first aid;
2. Long-term stable sound reinforcement sequence: optimized placement → gain control → equalizer frequency sweeping, and finally assisted by feedback suppressor;
3. Pit avoidance reminder: Don't simply madly attenuate the overall treble, which will lead to a thin and ugly voice. Accurate attenuation of the whistling point is a professional operation;
4. The core of multi-microphone scene: The less the number of turns on, the more stable it is. Idle microphones are directly muted to prevent hidden feedback.