Unless you're aspiring to be the next Jimi Hendrix or Pete Townsend, feedback on your
loudspeakers is a bad thing! HowToAV takes a look at how to remove those
dreadful squeaks and howls from your next performance.
Here at HowToAV we love feedback - but only when it's posted in the Comments section below!..
But one of the most common audio questions our team gets asked is "How can I eliminate
feedback on my speakers?" - that dreadful howling so loved by rock guitarists and hated
by every sound engineer and presenter speaking into a microphone.
Audio feedback (sometimes referred to as the Larsen effect) is not only a huge annoyance
for the audience and performer, but can also cause damage to your sound system - as well
as your ears! Feedback is produced when the sound from your
speakers is picked up by a microphone, re-amplified and picked up again from the speakers. This
creates a continuous loop and that dreadful unpleasant sound. The sound can vary between
a low frequency rumbling to the most frequently experienced piercing screech or howl.
Feedback can result from a number of factors including microphone placement, speaker placement
and room acoustics. But there are a number of techniques and technologies to avoid the
feedback effect. Firstly, try to avoid placing microphones
in close proximity to loudspeakers. The further away they are from the loudspeakers the better.
If the microphones are being used in a performance, place them behind the main speakers.
If the microphones are not close enough to the sound source, turning up the volume on
the microphone can increase feedback. So place it as close to the sound source as possible.
Using a directional microphone, such as a cardioid or supercardioid will reduce the
amount of unwanted sound picked-up from the microphones and also help to reduce the feedback.
Reducing the number of open microphones on a speech system can also improve the situation
along with the use of an automatic microphone mixer. This is very useful in radio microphone
systems where the presenter or performer is likely to change position a lot and may not
understand the significance of staying within a controlled space.
Before a performance, a graphic equaliser allows a sound system to be setup to prevent
feedback by 'ringing out' the microphones. This allows the sound engineer to effectively
cut out those frequencies at which feedback occurs. A parametric equaliser will do a similar
job as an equaliser but allows for even more precise frequency control.
Alternatively, a feedback eliminator device has the ability to detect when feedback is
about to increase and cut the exact frequency and therefore eliminate feedback.
In the space where the audio system is being positioned or installed, eliminating hard
and reflective surfaces will also help to reduce feedback. Soft furnishings such as carpets
and curtains absorb the sound rather than reflecting it back into the room.
Other simple adjustments such as holding the microphone close to the mouth, using in-ear
monitors instead of speaker monitors on stage and simply training the presenter or performer
where - and where not - to stand on stage or in the room, can significantly reduce the
feedback and ensure a professional, annoyance-free performance or presentation.
For more information on avoiding feedback, loudspeaker placement or microphone options,
contact the HowToAV team by clicking on the screen now. Or leave us your questions in
the Comments section below. And don't forget to Subscribe to the HowToAV
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