How we Prevent Feedback at Your Event

Feedback occurs when a microphone's signal is routed through the sound system loud enough that it forms a loop: Sound goes into the microphone, which comes out of the speaker, which goes into the microphone, which comes out of the speaker, and so on.

At some frequency:
speaker → room → microphone → preamp → speaker
The loop becomes unstable when the product of all those gains reaches 1 (0 dB) and the phase around the loop is appropriate.

Our goal as audio engineers is to set up the system and mix such that we have the highest "gain-before-feedback", which means we have the most ability to turn the volume up for the audience before you start that loop. This doesn't mean we always want more volume, it just means the engineer has a higher dynamic range to work within before the system limits them.

There are 4 main ways we set up and engineer a sound system that help minimize feedback:

  • Microphone choice, placement, and technique

  • Speaker choice and placement

  • System Tuning

  • Microphone processing

Microphone Choice, Placement, and Technique

The various kinds of microphones that exist have differences in how they pick up sound and reject sound from other directions. To have the lowest chance of feedback at a live event, we need to select the right kind of microphone depending on where it is going and how it will be used.

First is the capsule, the thing inside the microphone that moves and creates a voltage pattern we can turn into a sound. There are four main types: dynamic, small diaphragm condenser, large diaphragm condenser, and ribbon mics. These all have their own characteristics to how they pick up sound, and we pick the right one to fit the use case. In live sound, that's mostly dynamics and some condensers.

The second consideration is the pickup pattern of the microphone - which directions it picks up sound most clearly, and which it rejects sound from. Some microphones pick up sound from all directions equally (omnidirectional), some mostly pick up sound from in front of them (cardioid, super-cardioid, hyper-cardioid), some have narrow patterns (shotgun mics, for example), and some have more complex patterns such as 'figure-eight' or 'mid-side'. We always try to choose the one that fits each situation best.

Third, where the microphone is placed and pointed matters a lot. Many know from experience that if you point a live mic right at a speaker, it will quickly start a loop with said speaker and cause awful feedback. Aiming the mics opposite from the speakers' horns helps to increase the available gain.

Fourth is simple - using the microphone well. Generally, the closer you can hold the mic to your mouth, the better (up to about 1" away). The more level coming directly into the mic, the less our engineer has to gain it up to achieve the same audience volume. It also helps to slightly angle the mic from your lips, such that breathing and plosives go over the mic's capsule instead of right into it, reducing loud, startling or distracting sounds.

Speaker placement

Speakers are not simply sources of “more sound,” but tools for directing sound where it needs to go (see our article Live Sound Reinforcement Explained). Designing a sound reinforcement system that keeps as much sound away from the microphone pickups as possible can do a great job of reducing feedback before any settings on the mixer have been touched.

System Tuning

Once a PA system is set up, our engineers can do something called 'tuning the system'. Essentially, this means that we look at how accurately our speakers produce the sound that we send them, and how they interact with each other in the room. We apply filters to correct any overall imbalances and also find frequencies that resonate unusually strongly in the venue. Cutting those frequencies out, combined with having an overall balanced and accurate system, can increase the gain we have before feedback occurs.

Microphone Processing

Once the system is set up and tuned, there are various controls we have on each microphone that can help control the sound while preserving natural speech.

  • Appropriate Gain Structure is maintained so that our available gain isn't being wasted and that there is no distortion.

  • Equalization is used to remove any immediate resonances so that they don't feedback.

  • Dynamics Processing and Gating is used to reduce ambient noise on each mic and provide a smoother, more consistent sound.

  • Automix can be applied to a series of microphones to automatically open the active speakers' mics, and close unused ones, lowering the total open gain at any given moment.

Venue Considerations

Other common problems can contribute to high chances of feedback, such as excessive room reverberation ("wet" rooms), flutter echo in a space, and inconsistent output volume. Selecting a venue with a dryer acoustic and few direct reflections or echoes not only helps support feedback reduction but also improves attendee experience and intelligibility regardless of sound system quality.

What This Means for Your Event
The goal isn't simply to prevent embarrassing feedback. It is to give the engineer enough margin to provide clear, comfortable, reliable sound reinforcement throughout your event. Given the right venue, well-placed speakers and select microphones, tuned and processed by a skilled engineer, we can make sure that your event's sound doesn't get ruined by squeals and rings.

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