Syskonics / Guide
How to Reduce Microphone Feedback
The causes of howling in a PA system, and the fixes in the order you should try them — starting with the ones that cost nothing.
Feedback is the howl or ring that appears when a microphone picks up sound from the loudspeakers it is feeding. The signal goes round the loop — microphone, amplifier, speaker, back into the microphone — gaining a little each time until it runs away.
Almost all of it is preventable, and most of the fixes cost nothing. Work through them in the order below, because the free ones solve the majority of cases.
1. Put the speakers in front of the microphones
This is the single most effective fix and the one most often ignored. If the loudspeakers are behind or beside the microphone, they are firing directly into it and feedback is inevitable at almost any usable level.
In a hall, that means the main speakers should be forward of the lectern, aimed at the audience. In a room with distributed ceiling speakers, it means being careful about which speakers sit directly above a presenter position — and, where possible, turning down or reassigning the nearest one.
2. Use a directional microphone where you can
A directional pattern rejects sound arriving from behind the microphone, which buys real headroom before feedback starts. Unidirectional and cardioid models are the ones to look for: the SYS-ND86 and SYS-U87 handhelds are uni-directional, the SYS-D27 conference microphone is unidirectional, and the SYS-E66 gooseneck is cardioid.
Omni-directional microphones — which includes most headset and lavalier condensers — hear the room equally in all directions. They are used for good reasons, mainly comfort and consistency of level, but they will always feed back sooner than a directional model in the same position.
3. Get close to the microphone
The closer the microphone is to the mouth, the less gain is needed at the amplifier, and gain is what drives feedback. Halving the distance between the mouth and the capsule is worth a substantial amount of headroom.
This is precisely why headset microphones are the standard for teaching and fitness. A headset such as the SYS-60CC or SYS-370Q holds the capsule at a fixed short distance no matter how the wearer moves, so the gain can stay low and consistent.
4. Fix the gain structure
Turn the microphone's own gain up and the master level down, rather than the reverse. Running a channel at low gain and compensating with a high master forces every part of the chain to work harder and brings the whole system closer to the feedback point.
Then use the tone controls to cut, not boost. Feedback usually starts in a narrow band, and gently reducing that region on the amplifier's treble or bass control is more effective than adding level elsewhere.
- Set microphone gain first, master level second.
- Cut problem frequencies rather than boosting around them.
- Mute microphones that are not in use — every open microphone adds another feedback path.
5. When the room is the problem, use a suppressor
Some rooms cannot be fixed by placement alone: hard parallel walls, a temple or auditorium with a lot of reflective stone, or an event where the presenter must be free to roam in front of the speakers.
A feedback suppressor sits between the mixer and the amplifier and uses DSP to detect the frequencies that are starting to ring, notching them out automatically before they become audible. The XTR 6.0 is a 1U rack-mount unit that does this, works with mixers, amplifiers and microphones generally, and runs on AC 220–240V.
It is worth being clear about what a suppressor is and is not. It buys headroom in a difficult room. It does not compensate for speakers pointed at the microphone — fix the placement first, then use the suppressor for what is left.
Products in this guide
XTR-6.0
Audio Feedback Suppressor
- Worship
- PA System
SYS-ND86
Wired Microphone
- Presentation
- Live Stage
- Studio
SYS-E66
Wired Microphone
- Conference
- Presentation
- PA System
SYS-60CC
Wired Microphone
- Classroom
- Presentation
- Live Stage
Common questions
01What causes microphone feedback?
A loop: the microphone picks up sound from the loudspeakers, that sound is amplified and played again, and the microphone picks it up once more. Each pass adds gain until the loop runs away and howls.
02How do I stop feedback without turning the volume down?
Move the speakers so they fire away from the microphone, use a directional microphone, and get the capsule closer to the mouth so less gain is needed. Those three changes usually solve it without losing level.
03Do feedback suppressors actually work?
Yes, for what they are designed to do. A DSP suppressor such as the XTR 6.0 detects ringing frequencies and notches them automatically, which buys usable headroom in acoustically difficult rooms. It is not a substitute for sensible speaker placement.
04Why do headset microphones feed back less?
Because they sit very close to the mouth, so the system needs far less gain to reach a given level — and lower gain means more margin before the feedback loop takes hold.