How to Stop Feedback in Live Sound

Feedback happens when a microphone picks up sound from a loudspeaker and re-amplifies it, creating a loop that builds until the system oscillates. The frequency that feeds back is typically the one with the highest gain before instability—often a resonant room mode or a peak in the system's frequency response.

Key factors include: excessive gain, poor microphone placement relative to speakers, improper EQ (boosting problematic frequencies), and reflective room acoustics. Understanding these root causes is the first step to prevention.

Proper gain structure ensures that each stage of the signal chain operates optimally without adding noise or distortion. Start by setting the microphone preamp gain so that the loudest vocal or instrument peaks hit around -6 dBFS on the console meter. Avoid cranking gain to compensate for low output—this invites feedback.

Use the fader for level adjustments after gain is set. A common mistake is using the channel fader to boost a quiet source, which raises the noise floor and increases feedback risk. Instead, increase gain at the preamp stage while monitoring the meter. SSOUNDS DSP-equipped amplifiers allow precise input and output gain staging, giving engineers fine control over system headroom.

Graphic and parametric EQs are your primary weapons against feedback. Identify feedback frequencies by listening or using a real-time analyzer (RTA). When a frequency starts to ring, notch it out with a narrow Q (high bandwidth) cut of 3–6 dB. Common feedback zones: 250–500 Hz (boxy), 1–4 kHz (nasal), and above 5 kHz (sibilant).

For monitor wedges, apply a high-pass filter at 80–100 Hz to reduce low-frequency rumble that can cause feedback. On main PA, use system EQ to flatten the room's response. SSOUNDS loudspeakers feature factory presets that optimize phase and frequency response, reducing the need for drastic EQ cuts. Always cut rather than boost to avoid exciting feedback.

Microphone placement and pickup pattern dramatically affect feedback susceptibility. Use cardioid or hypercardioid mics to reject sound from the rear—where monitors typically sit. Place the mic close to the sound source (within 2–6 inches for vocals) to maximize direct-to-reverberant sound ratio.

Educate vocalists to sing directly into the mic's capsule, not off-axis. Off-axis pickup reduces level and changes frequency response, often leading engineers to increase gain—a recipe for feedback. For instruments, close-miking with proper polar pattern orientation minimizes spill from monitors.

Monitor wedges should be positioned so that the microphone's null (the angle of least sensitivity) points toward the speaker. For a cardioid mic, the null is at 180° (directly behind the capsule). Place the monitor directly in front of the mic's rear, not to the side. This simple geometry can reduce feedback by 10 dB or more.

Keep monitor levels as low as possible. Only provide enough level for the performer to hear themselves. Use auxiliary sends to create separate monitor mixes, and avoid sending unnecessary sources (like drums) to vocal monitors. SSOUNDS coaxial stage monitors offer consistent coverage and phase coherence, making it easier to achieve high gain before feedback.

In permanent installations, thoughtful speaker placement and acoustic treatment can prevent feedback. Avoid placing loudspeakers directly behind microphones. Use directional subwoofers to reduce low-frequency buildup in the stage area. Acoustic panels and bass traps can tame room resonances that trigger feedback.

For touring systems, SSOUNDS line arrays and point-source enclosures are designed with controlled directivity, minimizing energy spill onto stage. This allows higher overall SPL before feedback. Always ring out the system before show time: walk the stage with a handheld mic at performance positions and notch any ringing frequencies.