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Feedback. That sharp, piercing howl that cuts through a performance and makes every head in the room turn. Every live sound engineer has experienced it—and every one of them wants to avoid it.
The good news: feedback is almost always preventable. Most cases come down to one root cause—sound from a speaker re-entering a microphone, getting amplified again, and spiraling into that unmistakable screech. Understanding why it happens gives you everything you need to stop it.
This guide breaks down exactly how microphone and speaker placement affects feedback in live sound reinforcement, and what you can do—before you even touch the gain knob—to keep your system clean and controlled.
Feedback occurs when a microphone picks up the output of a speaker it is also feeding into. The signal loops: microphone → amplifier → speaker → microphone → amplifier → speaker, and so on. Each cycle amplifies the signal further until the system saturates and produces that familiar howl.
Several variables determine how quickly and severely this loop develops:
Gain levels — The higher the gain, the less physical distance it takes to create a loop
Microphone polar pattern — Omnidirectional mics pick up sound from all directions; cardioid and supercardioid mics are far more directional
Speaker dispersion — Wide-dispersion systems fill more of the room, including areas behind and beside microphones
Room acoustics — Reflective surfaces like concrete walls and glass bounce sound back toward microphones
The amplifier driving your speakers plays a significant role too. Systems using high-density rack amplifiers or digital power amplifiers with precise output control give engineers more headroom to work with before feedback becomes an issue.
Where you put your speakers matters enormously. The single most effective physical change you can make is ensuring your main PA speakers project sound away from your microphones—not toward them.
Point speakers toward the audience, not the stage. Front-of-house speakers should always be positioned in front of the microphone line. If your mics are on a stage and your speakers are behind the mic line, sound will pour directly into open microphones and feedback is almost inevitable.
Elevate your main speakers. Speakers mounted on stands or flown from rigging can be angled down toward the audience. This keeps high-SPL zones away from stage microphones while still delivering clear, even coverage to the room.
Use delay speakers for large venues. Rather than cranking the volume on your mains to cover a long room, add delay speakers further into the space. This reduces the overall output needed from your live sound amplifier, which directly lowers the risk of feedback.
Keep subwoofers in front of the stage. Low-frequency energy is omnidirectional by nature, but cardioid subwoofer arrays—where two subs face opposite directions—can reduce rear output significantly and improve front-of-house control.
Smart microphone technique does as much work as smart speaker placement. A few key principles apply universally across live sound reinforcement environments.
Use directional microphones. Cardioid and supercardioid microphones reject sound from behind and to the sides. Position them so their null points (the areas of least sensitivity) face your speakers. For a cardioid mic, the null is directly behind the capsule—aim that at your monitors.
Keep mics close to the source. The closer a microphone is to the sound source, the lower the gain needed to achieve the right level. Less gain means more headroom before feedback. This applies to vocal mics, instrument mics, and lectern mics in conference and house-of-worship settings alike.
Minimize open microphones. Every open mic in the room is a potential feedback path. Use mute buttons or automixers to keep unused microphones off when they are not needed.
Watch mic height on podiums and lecterns. A mic placed too low forces the speaker to project over it toward the PA system. Position lectern mics at a 45-degree angle, roughly 15–20 cm from the speaker's mouth.
Your power amplifier does more than drive speakers—it determines how much control you have over the entire signal chain. An amplifier with a high damping factor, low THD, and a flat frequency response gives you clean, predictable output that is far easier to manage at high volumes.
Auway Audio's MT Series transformer power amplifiers are built with exactly this in mind. The MT400, for example, delivers a damping factor of greater than 400 and THD+N below 0.05% across the full 20Hz–20kHz range—specs that translate directly to tighter speaker control and less unpredictable resonance that can trigger feedback loops.
For demanding live events where high output is required, the MT1601 steps up the performance with 2x1600W at 8Ω and a slew rate of 28V/μs, meaning the amplifier responds fast enough to handle the transient-heavy dynamics of live music without smearing or distortion that can cause frequencies to bleed unpredictably through a system.
The table below compares key specifications across both units:
Specification | MT400 | MT1601 |
|---|---|---|
Output (8Ω Stereo) | 2x400W | 2x1600W |
Output (4Ω Stereo) | 2x600W | 2x2700W |
Output (Bridge Mono) | 1200W | 5150W |
THD+N | <0.05% | <0.05% |
Damping Factor | >400 | >400 |
Frequency Response | 20Hz–20kHz (+0/-0.5dB) | 10Hz–20kHz (+0/-1dB) |
Slew Rate | 40V/μs | 28V/μs |
Output Circuit | Class H | Class H |
Input Connector | XLR | XLR |
Output Connector | SPEAKON | SPEAKON |
For installations using a digital power amplifier or Class TD design, built-in DSP features like parametric EQ and output limiting offer additional tools for taming problem frequencies before they cycle into feedback.
Run through this before every show:
Walk the stage with a mic open at low gain. Listen for early feedback warnings—a slight ringing in a specific frequency means that frequency is on the edge
Ring out the system using a graphic EQ to notch down problem frequencies before the performance begins
Check monitor angles—stage wedge monitors should point directly toward the performer's ears, not toward open microphones on the same stage
Test at performance gain levels—not just at low volume. Systems behave differently when driven hard
Confirm speaker delay alignment—misaligned delay speakers create comb filtering that can amplify certain frequencies artificially
Graphic equalizers and feedback suppressors are useful tools, but they are not substitutes for correct placement. Engineers who rely on EQ to fix placement problems are fighting an uphill battle—and often sacrificing sound quality in the process.
The most reliable live sound reinforcement systems are built on clean microphone technique, strategic speaker positioning, and amplification equipment that performs predictably under pressure. When those foundations are solid, feedback becomes the exception rather than the rule.
Auway Audio manufactures a full range of professional amplifiers—from compact background music amplifiers to high-density rack amplifiers built for large-scale touring—designed to give engineers the clean, stable output they need to keep live systems under control. Contact the Auway Audio team at Cony@cn-auway.com or visit cn-auway.com to find the right amplifier for your application.
Feedback occurs when a microphone picks up the amplified output from a speaker it is feeding into, creating a loop. The signal amplifies itself repeatedly until the system produces a loud howl or screech. The root causes are usually excessive gain, poor speaker placement, or open microphones positioned within a speaker's coverage zone.
Cardioid and supercardioid microphones are the best choices for feedback-prone environments. Their directional polar patterns reject sound from behind and to the sides—which, when positioned correctly, means they reject monitor and PA speaker output. Omnidirectional microphones should be avoided in high-gain live sound situations.
A high-quality live sound amplifier with a high damping factor, low THD, and flat frequency response gives engineers tighter speaker control. This results in more predictable output and greater headroom before feedback develops. Amplifiers with built-in DSP, such as digital power amplifiers with parametric EQ and output limiting, offer additional tools for managing problem frequencies.
Main PA speakers should always be positioned in front of the microphone line and angled downward toward the audience. This keeps the high-SPL coverage zone directed away from stage microphones. Flying speakers or using speaker stands to elevate and angle them is one of the most effective physical methods for feedback reduction.
Yes. High-density rack amplifiers that deliver precise, stable output allow engineers to run systems with greater headroom. This means less need to push gain levels dangerously high, which is one of the primary triggers for feedback in large venues. Consistent, low-distortion amplification also prevents erratic frequency behavior that can initiate feedback loops.
