Larsen, Feedback and Saturation - The Guide to Never Suffer These Audio Nightmares Again
That horrible, sharp, piercing noise that drills through your ears. The crackle that ruins the key moment of a speech. Or the hissing that makes the singer inaudible. These dreaded acoustic phenomena—larsen, feedback, saturation—are among the worst experiences an event can suffer. And contrary to popular belief, they are not inevitable accidents caused by "bad luck." They are well-understood physical phenomena with identifiable causes and concrete solutions. Understanding these three problems will allow you to prevent them and choose the technical providers who truly master them.
Larsen: The Piercing Noise That Kills the Atmosphere
What Exactly Is Larsen?
Larsen (or "acoustic feedback") is a noise resulting from a positive feedback loop: a microphone picks up the sound from a speaker, that amplified sound returns to the microphone, gets re-amplified, and creates an oscillation that generates that characteristic, infernal noise.
Here is the simple causal chain:
- A microphone picks up sound from a speaker
- That amplified signal passes through the mixing console
- The amplified signal comes out of the speaker
- The microphone picks up that louder amplified sound
- Infinite loop: the signal amplifies continuously, creating an oscillation
The frequency of this oscillation depends on the room's geometry and the equipment used. It is typically a very high-pitched sound (between 2 kHz and 8 kHz) that pierces your eardrums.
Why It Happens
The main causes are:
- The microphone too close to the speaker: a microphone placed directly facing a monitor speaker creates larsen within seconds
- Gain set too high: excessively increasing the gain at the microphone or console creates conditions favorable to larsen
- A problematic room: some rooms with a specific frequency resonance promote larsen
- Acoustic echo: when the back-and-forth sound from a distant wall reaches the microphone with a delay, it creates larsen conditions
How to Prevent It
A professional sound engineer prevents larsen through:
The equalizer: by slightly reducing the problematic resonance frequency (identified during testing), it becomes physically impossible for the oscillation loop to form.
Positioning: microphones and speakers are positioned so that the microphone minimally picks up the amplified source.
Appropriate levels: gain is set so that even the maximum signal remains comfortable and never flirts with larsen conditions.
Isolation: using directional (cardioid) microphones rather than omnidirectional ones prevents the microphone from picking up sound from behind.
A professional tests all of this before your event. An amateur waits for larsen to occur and then tries to react—usually too late.
Feedback: When the Sound Cracks
Feedback vs. Larsen: The Difference
Many people confuse feedback and larsen. They are not the same thing.
Larsen is an audible oscillation—a piercing, infernal noise.
Feedback is a crackling distortion or a crunch that occurs when a signal exceeds its level limit. It is subtler than larsen but equally unpleasant.
What Is Feedback Exactly?
Audio feedback occurs when a signal exceeds the maximum processing capacity of a device (microphone, console, amplifier, speaker). At that point, the device can no longer process the signal correctly, and you hear distortion.
For example:
- A microphone with an input level that is too high produces crackling
- A console with faders set too high saturates the main output
- An amplifier receiving too strong a signal produces distortion
The sound becomes crunchy, harsh, and uncomfortable to listen to.
When It Happens
Typical situations:
- A singer shouting into a microphone designed for normal speech
- A band gradually increasing its volume while the sound engineer fails to keep up
- A DJ sending a very hot signal without the engineer reducing the input gain
- A recorded drum track that, when activated in the background, causes an overload
How to Prevent It
A qualified sound engineer:
- Uses compressors to limit signal peaks without reducing overall volume
- Adjusts input levels so that even the maximum signal stays below the saturation threshold
- Uses limiters on the main outputs to prevent amplification beyond a threshold
- Stays vigilant throughout the event and adjusts gains as the performance evolves
Saturation: The Physical Limit of the Equipment
What Is Saturation?
Saturation is the point at which a speaker, an amplifier, or any electronic device reaches its maximum capacity. Beyond that point, it cannot produce more volume or power. The sound becomes distorted, crunchy, and unpleasant.
This is different from feedback: it is a physical limitation, not a positive loop.
When Saturation Occurs
Typical scenarios:
- A small speaker used for a large, loud band
- A PA system undersized for the number of people
- An old or low-end amplifier pushed to its maximum
- Too many devices sharing the same power supply, causing general degradation
How to Prevent It
Prevention requires:
- Appropriate sizing of equipment relative to your event
- Redundancy: having spare speakers or backup amplifiers
- Acoustic measurements before the event to verify that the chosen system can reach the required sound pressure levels
- Proper maintenance of the equipment
How to Identify a Good Provider vs. a Problematic One
Best Practices to Expect
A professional sound engineer:
- Arrives 3-4 hours early for testing (soundcheck)
- Specifically tests larsen and feedback prevention
- Uses professional-grade equipment with built-in equalizers and limiters
- Stays at the console throughout the entire performance, vigilant
- Quickly corrects any problem that arises
- Uses directional rather than omnidirectional microphones to reduce risks
Red Flags
- "We'll see how it sounds"
- "If there's larsen, we'll turn the gain down"
- No testing before the event
- Use of downgraded or very old equipment without maintenance
- No limiter on the main outputs
Real-World Cases
Wedding: The Best Man's Speech
Problematic scenario: Standard cardioid microphone, monitor speaker directly behind. The best man gets excited, raises the volume of his voice. Larsen hits within 30 seconds.
Professional solution: Quality cardioid microphone with an inline compressor, monitor speaker positioned at 90 degrees from the microphone, equalizer slightly reducing frequencies at 3-4 kHz (the range where larsen occurs). No chance of larsen regardless of how loud the best man gets.
Corporate Event with a DJ
Problematic scenario: The DJ plugs in their laptop directly. The signal is very hot, causing visible saturation on the console's meters. The sound is unpleasantly crunchy.
Professional solution: A direct injection (DI) box with a passive attenuator solves the problem. The level is adapted to the console's input without saturation. Adding a compressor ensures that even if the DJ boosts the bass, the system never saturates.
Outdoor Concert
Problematic scenario: Undersized system. The band starts without issues, then the volume increases. At 75% of the band's maximum volume, the system saturates and crackles.
Professional solution: Prior acoustic measurements to size a system capable of reaching 100 dB SPL with headroom. In practice, the system can reach 105 dB SPL, so 100 dB SPL is achieved easily and without saturation.
Conclusion
Larsen, feedback, and saturation are three distinct nightmares, each with its own causes and specific solutions. A professional technical provider prevents all three through a combination of good equipment, good positioning, proper settings, and vigilance throughout the event.
When you hire a sound engineer, explicitly ask: "How do you prevent larsen, feedback, and saturation?" A good answer demonstrates real competence. At PraiseHub, all our partner sound engineers master these three phenomena. Contact us for an event free of acoustic incidents.
