The single most effective technique for preventing feedback is proper microphone placement. This fundamental approach requires no special equipment and can dramatically improve your sound system's stability.

Keep Microphones Close to Sound Sources

When a microphone is positioned close to the sound source (such as a vocalist's mouth), the direct sound is much louder than ambient sound or speaker output. This allows you to run lower gain levels while maintaining adequate volume, significantly reducing the risk of feedback.

Best practices for close miking:

• Position vocal microphones 1-3 inches from the performer's mouth
• For instruments, place microphones 2-6 inches from the sound source
• Instruct performers to maintain consistent microphone distance
• Use microphone techniques that maximize gain before feedback

Position Microphones Away from Speakers

Always ensure microphones are positioned away from speakers, particularly monitor speakers. The classic "microphone behind the main speakers" rule is fundamental to feedback prevention.

Speaker placement guidelines:

• Position main speakers in front of performers and microphones
• Angle monitor speakers away from microphone pickup patterns
• Maintain maximum possible distance between microphones and speakers
• Use directional monitors that focus sound toward performers

Use the Microphone's Null Points

Every directional microphone has "null points"—areas in its pickup pattern where it's least sensitive to sound. Understanding and utilizing these null points can significantly reduce feedback.

For cardioid microphones:

• The null point is directly behind the microphone (180° from the front)
• Position monitors directly behind performers, in the microphone's null point

For supercardioid and hypercardioid microphones:

• The null points are at approximately 125° and 235° from the front
• Position monitors at these angles for maximum rejection

Not all microphones are created equal when it comes to feedback resistance. The microphone's polar pattern (directional characteristics) and frequency response significantly impact its feedback susceptibility.

Directional Microphones

Directional microphones, particularly cardioid, supercardioid, and hypercardioid patterns, are designed to pick up sound primarily from one direction while rejecting sound from other directions. This makes them ideal for feedback-prone environments.

Microphone pattern comparison:

• Omnidirectional: Picks up sound equally from all directions. Avoid in feedback-prone situations.
• Cardioid: Heart-shaped pattern that rejects sound from the rear. Good for general use.
• Supercardioid: Narrower pickup pattern with better side rejection. Excellent for noisy stages.
• Hypercardioid: Very narrow pickup pattern with maximum rejection. Best for extreme feedback situations.

Frequency Response Considerations

Microphones with a tailored frequency response can help reduce feedback at problematic frequencies. Look for microphones with:

• Reduced sensitivity in the feedback-prone 250Hz-800Hz and 2kHz-4kHz ranges
• Smooth frequency response without sharp peaks
• Presence boost designed for vocal clarity without feedback

Wireless vs. Wired Considerations

While wireless microphones offer freedom of movement, they can sometimes be more susceptible to feedback due to:

• Potential for wider movement around the stage
• Difficulty in maintaining consistent distance from the sound source
• Compression in the wireless transmission that can affect dynamic range

If using wireless microphones in feedback-prone environments:

• Choose systems with adjustable gain at the transmitter
• Use directional capsules with tight pickup patterns
• Implement proper antenna placement for reliable signal

Proper gain staging throughout your audio system is crucial for minimizing feedback while maintaining adequate volume. A well-structured gain path ensures you're getting the maximum signal-to-noise ratio without pushing the system into feedback.

Start with Proper Input Gain

Begin at the source by setting appropriate input gain on your mixer:

1. Have the performer speak or sing at their loudest expected level
2. Adjust the input gain until the signal peaks around -12dB to -6dB on your meter
3. Avoid the temptation to push input gain too high, as this increases feedback risk

Use Faders for Level Control

Once input gain is set correctly:

• Use channel faders to balance the mix
• Keep the main output fader around 0dB (unity gain)
• Make small, incremental adjustments when increasing volume

Implement a System-Wide Approach

Remember that gain exists at multiple points in your signal chain:

• Microphone preamplifier gain
• Channel EQ and processing
• Auxiliary sends for monitors
• Main output processing
• Amplifier input sensitivity
• Speaker efficiency and placement

"Ringing out" is the process of identifying and attenuating specific feedback frequencies using equalization. This technique allows you to maximize gain before feedback by targeting problematic frequencies.

Manual Ring Out Process

For the most precise results, follow these steps:

1. Start with all graphic EQ faders at center position (0dB)
2. Slowly raise the system gain until you hear the first feedback frequency
3. Identify which frequency is feeding back (this takes practice)
4. Reduce that frequency band by 3-6dB on your graphic EQ
5. Continue raising the gain until the next frequency feeds back
6. Repeat the process until you've