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:

Sound…Sound…Sound…

And not:

Sound…Sound…Sound

Chris

All the other posters have the real answers, but sometimes that just can’t be done. We have children’s choirs in front of the mains and are forced to use EQ to notch out the offending frequencies. Like someone else said, use an RTA. If I read the release notes correctly, there is an RTA with the GEQ. During a sound check, SLOWLY bring up the fader (or gain) until you just hear feedback. The RTA should peak and you can take that frequency down a little. After that you might find another. We can usually get much better gain before feedback after dropping a couple of the offending frequencies.

Rick Kohrs
Good Shepherd Lutheran Church – West Campus
Verona, WI

You might be able to knock out the frequency using one of the 4 channel eq’s. As most have said, use a narrow Q, bring up the volume for frequency level and then slide the frequency up and down until you find the offending frequency. The touch screen view of the EQ will be more helpful as you can see the Q value better.

This might be a waste of a group, but you could assign the pulpit to a group. Doing this, you have a 1/3 octave GEQ for a single channel. We do this for our 3 choir mics.

Don’t do this with the LR GEQ, you can loose important room frequencies.

Rick Kohrs
Good Shepherd Lutheran Church – West Campus
Verona, WI

Podium mics under speakers – very tricky. The podium itself is a fantastic audio reflector that can focus energy onto the mic itself (even it is not directly in the path of the speaker, the lower frequencies – even mids, still hit pretty hard). One thing that has helped is some type of “cushy” or heavy cloth covering on the podium to help absorb some of the energy. Change the angle if possible too. Using a group as discussed earlier and apply GEQ (try the different types) along with an RTA (AudioTools is great) to assist in identify the frequencies is also good. The big problem will remain though in not removing too much “content” so that the speakers voice still sounds close to the actual speakers voice.

Bob

GLD80, AR2412, 2xAR84, Dante