But don't forget, the best thing to do to control feedback is turn everything down. So long as the performers are careful to always keep their mics pointed away from the monitors, or specifically to point that tail end of the mic at the monitor at all times, that shouldn't be an issue. A common technique used by sound engineers is "ringing out" a sound system by using a graphic equalizer to reduce the level of the frequencies that feedback:.
As a musician and an audio tech, I'm a sound guy's worst nightmare. During rehearsal, my headset mic was feeding back and the audio tech kept turning my volume down and telling me that I couldn't move around.
I knew the problem was midrange feedback, so I explained to him that if he just lowered the midrange on the EQ, the problem would go away. He 'passionately and firmly' explained to me that the only way to get rid of feedback was for him to lower the volume and for me to stand still. After enduring the first song, I walked back to the board, reached over his shoulder and dropped the midrange. I sang a couple notes, looked at him, smiled and walked back onstage.
Did I mention I was wireless, too? The problem was solved and we didn't talk after the set, but I know he learned something that night. My last bad feedback incident was caused by gain stage being manipulated by the engineer without telling us - after we'd gotten to a good place.
The resulting, shrieking feedback changed everything - there was nothing but pain filling up space between our ears. Many people forget that EQ'ing something can cause a volume change - right in that frequency. Of course, EQ can remedy volume problems quite easily. Just take a moment to ferret out the offending frequency or cluster of frequencies - band members protecting their ears, of course - and "forensically" attenuate, which will immediately solve the problem.
A hall of mirrors, isn't it? Remember that microphone placement is crucial to eliminating feedback, and the temptation to wander away from the ideal microphone position when using a wireless is great. If the performer gets too close to a loudspeaker, feedback will result; a good feedback reducer will be able to catch and eliminate the feedback faster than a sound engineer.
Learn to identify the ringing frequency by doing blind 'what is that frequency? Have someone dial up a tone and see if you can identify what frequency it is. This is great training to identify the problem frequency during feedback howl and how I learned how to tame feedback. You probably won't get the results you need. A Shure associate since , Davida Rochman graduated with a degree in Speech Communications and never imagined that her first post-college job would result in a lifelong career that had her marketing microphones rather than speaking into them.
This post is all about the most important tool for these scenarios: windscreens. The foam or fur cover of a microphone is called a windscreen. A windscreen protects the microphone diaphragm from gusts of air.
Without a windscreen, wind or breathing can cause loud pops in the audio signal. Windscreens break up gusts of air before they interact with the microphone diaphragm.
There are some obvious reasons to use a windscreen and some not-so-obvious reasons. This section will explore the uses of windscreens. Whether it be for a concert, a film shoot, or an interview, recording outside presents unpredictable circumstances. A windscreen is an essential part of this toolkit. Have you ever listened to a video recorded outdoors? Often, the soundtrack of an outdoor video contains the distracting sound of wind.
This noise is a low- to-mid-frequency sound that sometimes makes it difficult to hear the words being spoken. If you have, you know that removing this noise without destroying the sound quality of your recording is nearly impossible. A windscreen will redirect the wind away from the microphone diaphragm, while allowing sound waves to pass. Even indoors, wind can be an issue. Heating and air conditioning systems can create air currents. Fans can also cause indoor wind.
If you are recording indoors, be sure not to place the microphone near any source of forced air. However, if you are installing a system that will be used throughout the day without supervision, such as a conference room or public address system, you will have no control.
Users may choose to use a fan in the room, not knowing the issues it might create. You can use a windscreen as an insurance plan for unexpected drafts that might occur indoors. Keep in mind that wind moving past a stationary microphone is no different from a microphone moving through stationary air. If the microphone will be moved while in use, use a windscreen.
If you are using a boom pole for a film shoot, you might need to move the microphone to capture a moving source or multiple sources. You may be recording a scene in a vehicle or from a vehicle. In any case, windscreens can help protect the microphone from the air resistance created while in motion.
Most speak too far away from the microphone, but some speak far too close to the microphone. Prevent these pops by using a windscreen. This image shows the waveform of a microphone pop created by a plosive. The best way to address popping in a microphone is through the use of a pop filter. A pop filter is a mesh or wire screen placed between the microphone and the person speaking. Pop filters diffuse the air created by plosive sounds that would normally directly hit the microphone diaphragm.
If you are trying to prevent the p-pops caused by plosive sounds, you may want a pop filter instead of a windscreen. Check out this other article I wrote about the best pop filters for any budget. Windscreens can be used in these situations, although they are less effective. Although the primary function of windscreens is to prevent wind noise, they are also somewhat effective in protecting microphones.
This acts as a windscreen to prevent noise from bursts of air and as a screen to protect the capsule from saliva and dirt. When the microphone inevitably becomes dirty from years of use, simply replacing the windscreen will restore the microphone to a like-new state.
A useful strategy is to place the speakers on stands above the heads of those standing near the front which prevents the people from soaking up all the sound and also avoids deafening them! Some speakers have angled tilt mounts built in, and if yours don't, it may be worth investing in stands that have tiltable heads. Assuming, then, that you have the best gear you can afford, and that it's set up in the best place in the room, what else can you do?
The usual setup procedure for a PA system involves a process called 'ringing out' the room. This means turning up the gain on each mic until feedback just starts, and then backing it off by a few dBs.
Once this has been done for all the mics individually, you do it again with them all turned up and, if you hear ringing or feedback, reduce the master level slightly. My quick and dirty way of ringing out for small gigs is to set all the mic channel faders to 0dB, then turn up each mic trim one by one, until feedback starts, after which I back it off until the feedback just stops.
I do this for each mic in turn, check again with all the mics turned up, then pull the master mix fader down by 5dB. This not only checks for feedback problems but also leaves all the faders in more or less the same position, with room to go both up and down in level. The situation will probably get better when the audience starts filing in bodies are very good at soaking up sound which might otherwise be reflected back! Where feedback is particularly troublesome at one or two specific frequencies, a third-octave graphic equaliser may be used to reduce the gain by a few dB at those frequencies.
The process for setting these up is much as described earlier: turn up the master level until feedback starts, then try to identify the frequency at which it is taking place and turn that frequency down on the EQ. Then turn the master fader up again until a different frequency starts howling, and notch that one down too!
Graphic EQs can be useful for dealing with feedback at specific frequencies. Just turn up the main speakers until the feedback starts, identify the feedback's frequency, and turn that slider down. Repeat until the most troublesome frequencies have been identified and pulled back. Be aware, though, that the overall tonality of the system will be affected as the graphic EQ bands are far wider than the feedback spots they're trying to notch out, so use as little cutting as you can get away with.
Unless you're dealing with a very specific problem, you shouldn't be cutting more than a handful of decibels from any band, and boosting is generally considered pretty unwise if you're suffering from any feedback problems! Graphic EQs may also be used in the monitor feeds, which can be 'rung out' like the main speakers.
Do these first in isolation, to check that everything is coming through OK, then check them again with the front-of-house system turned up, and fine-tune as necessary. Feedback suppressors, such as this popular Behringer model, work by automatically detecting feedback and then re-tuning their filters to cut the relevant frequency. They're not a substitute for proper engineering, but they can obtain you a few extra decibels of level before feedback starts to set in.
In recent years, there's been a lot of interest in automatic anti-feedback devices. These use filters, just as a graphic EQ does, but they're able to identify the precise feedback frequencies and then retune their own filters to exactly match those frequencies. The filters are very much narrower than those in a third-octave graphic equaliser — usually just a fraction of a semitone wide — so their effect on the overall tonality is significantly less.
The usual way of using these devices is to turn up the system gain slowly until feedback occurs, then to wait for the filter to lock on and notch it out.
Then the gain can be turned up a little more until a new feedback frequency starts up, and again it will be notched out. If you do this for the first four or five main feedback frequencies, you can then set any remaining filters to 'roam', so that they can pounce on any feedback that occurs during the performance but that isn't covered by one of the fixed bands — for example, if a singer accidentally points their mic at a monitor. Such systems can claw back a few more decibels of usable headroom and also eliminate the ringing that occurs near feedback, but they're not a complete cure.
They'll make life easier and give you a few more dB to play with, but that's about it. While stereo feedback killers can be placed across the entire mix and maybe others across the monitor mixes , there are also personal vocal pedals, such as those made by TC, that include feedback suppression, although, of course, these only provide benefits to the individual performers using them.
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