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If a sound goes into the mic and arrives back at the mic louder than it was the first time…and then it does it again…and then again…

All microphones in the same room as the PA they are routed through are feeding back all the time. The reason it isn’t normally a problem is that the signal gets quieter each time it goes from the mic, through the mixing console, amplifiers, speakers, air in the room… and back into the mic again.

As you increase the gain* you will reach a point where the signal will go from getting quieter on each cycle to getting louder on each cycle.

*Gain meaning any gain, not necessarily preamp gain.

If it isn’t loud enough before this happens you have a problem. [:)]

If you can get the desired source louder into the mic you can use less preamp gain to achieve the same input level. You can do this by having them produce a louder sound and/or moving the mic closer to whatever makes the sound.

You’ll also want to reduce the amount of sound from the PA picked up by the mic. Because this will be sent back to the PA… back to the PA…back to the PA…

Get the mic out of the coverage pattern of the PA.

Get the PA out of the “coverage” pattern of the mic.*

*Headset and lapel mics are usually omni-directional because using a directional mic very close to the source would produce a lot of unwanted proximity effect. They also generally have a flatter frequency response.

Directional (normally cardiod) headset and lapel mics do exist but have much more handling noise. They aren’t normally needed.

Your handheld mics are very likely cardiod and are probably normally held pointed back towards the person.

After that’s done narrow down a couple of PEQ bands as narrow as they go, I think it’s 1/9th octave. Turn on the “input full range” option in the pull-up tab. Cut them some amount. 9 db if you want but you might not need that much.

Have someone wear the mic as normal, stand in the normal area and speak as normal. Push the fader until the mic begins to ring.

Sweep a band around until the feedback stops. If it’s not loud enough push it until it rings again and cut that frequency too. If it’s the same frequency as before just cut it more.

Only cut as much as is needed to prevent feedback. Any more will harm sound quality for no real benefit.

Compression is nice on speaking mics but it won’t help with feedback. Used so that it only goes into gain reduction on louder peaks won’t be a problem (and it’s nice to have when people sneeze wearing a headset mic). [:p]

If the speech is being compressed at normal speaking volumes you will compensate for this either with the make up gain or with the fader. When the person stops speaking and the compressor releases feedback may start as a result.

Basically you want your system to behave as:


And not: