STOP Audio Feedback: 5 Effective Techniques

audio feedback really is a worst case scenario of what can go wrong at an event it's loud it's distracting it makes everybody wonder if the audio engineer knows what they're doing you can damage the hearing of yourself the performers the talent the audience plus you can actually damage equipment you can damage your audio mixer your microphones your power app or your speakers if the audio feedback is too bad at an event in this video we're going to walk through the five steps that I go through if I'm asked to come in and solve audio feedback issues at a live event whether it's on a festival stage a concert a corporate event a religious event a school event anything like that the same five steps are what I go through in order to solve all these audio feedback issues so you can have a more professional high quality high production value event and people aren't wondering if the audio engineer really knows what they're doing behind the board first of all if you are looking for pricing respect for anything that you see in this video I do have links down in the description below of everything you see in this video and everything that we use to make videos like this next what is audio feedback let's we need to quickly cover what it is so we can discuss how to solve audio feedback in its most basic form audio feedback happens when a microphone can hear the output of the speaker so if you have sound coming from the speaker goes into the microphone goes through your audio mixer comes back out through the speaker back through your microphone back through the speaker this can happen many many times in a second and it causes what's known as a feedback loop audio Loop audio feedback loop there's all types of different terms for it but basically the sound goes around so fast and gets so loud so fast because the microphone can hear the speaker and that is a really big problem and that's at the core of what we're trying to solve with these five steps an important thing to note on how audio feedback works is that it doesn't apply to all frequencies in the same way some frequencies will be more susceptible to feedback and this isn't something that you can just memorize if you're an out outdoor environment your microphones and your speakers will react completely differently than if you're in a small Ballroom or a church or a large Ballroom or any type of other venue a gym anything like that so do keep in mind that these aren't just settings that you can memorize to cancel out feedback it will very much depend on the environment that you're in that's why we have this five-step process to solve all your feedback issues okay now this isn't the first step if you're planning an event but if there's an ongoing event that has feedback issues this is the first thing that I'm going to do to resolve them you're going to need to get control of all the channels on your board you can do this by muting setting up noise Gates or using an auto mixer I'm going to run through all these now I'm sure if you've ever heard audio feedback at a small event like a wedding or something like that you'll look back at the audio mixer and the engineer will be doing something like this they're just trying to mute channels to figure out which microphone is causing the most problems this is what I do if you're trying to solve a problem you need to get control and only use the microphones that you need at any given time if there's a presenter speaking at the podium on stage all of your other microphones should be muted you shouldn't have your drum mics open you shouldn't have anything like that you should just have your one Podium microphone open same thing if you have a keynote speaker with a lapel mic that should be the only microphone that's not muted sometimes audio Engineers will be sleeping at the wheel they'll miss this they'll have them you know a drum overhead mic or something like that on and as soon as they unmute the lapel mic on the presenter then you'll get two hot mics on stage that are both very sensitive and you'll get a feedback loop so get in control of your muting another part of this is using noise Gates effectively a big one is on the drum kit how a Noise Gate works is you basically set a threshold say on the snare or kick drum and once you hit that snare that threshold is exceeded and the microphone will unmute so if nobody's playing the drums by default all six seven or eight drum microphones should be muted in theory but generally speaking you want to use noise Gates because like I said if the drummer's not playing then it automatically mutes all those microphones and you have a much lower chance of getting audio feedback now the last one I do want to touch on although it's less popular but it's more popular in the corporate world is I used to use Auto mixers a lot for corporate events if you're in a mastermind group or something like that where you have one or two presenters with clickbond lapel mics and then you have four Wireless handheld microphones around a boardroom table or something like that you're recording the vents you want everybody to always be speaking in the microphone so you can't like not use a microphone but you're in a small room and all these microphones in a small space have a ability to cause all kinds of feedback problems but if you use an auto mixer on most digital audio mixers they'll have an auto mixer built in now it solves this problem you can also get it at outboard Dugan audio mixer they're really helpful you can do it after in post-production as well basically if you you can apply an auto mixer to a certain number of channels on a digital audio mixer and it will basically figure out who needs to be the loudest if two people are talking at once it'll set them both at fifty percent and if one person speaking it'll automatically mute the rest of the microphones it works really well in a lot of environments like corporate environments but I would not recommend it for like a house of worship or a concert or a festival stage or something like that it is used quite a bit in theater as well it can be as well okay so muting helps good if you're in a pinch you can mute and control all your audio sources and this can help you get control over an event if you have a lot of feedback issues but what happens if you have a bit more time and you can plan things out properly at the beginning of this video we said that you get audio feedback when your microphone can hear your speaker so what comes to mind in terms of solving this problem let's get the speakers out in front so the microphone can't hear it this is extremely popular at all types of different events if you've ever been to a large concert or wedding or anything like that you'll see that the big speakers are hung above the corners of the stage on the front left and right and if you're at a wedding you'll see floor stands for your speakers or speaker stands on the front left and right corner of the stage now this is very very intentional you want your speakers out in front of the stage so the microphones can't hear the speakers as easily same thing goes for microphone placement just back up your microphone just a couple feet so you're not right on the front of the stage sometimes it's four feet or something like that and this will help prevent a lot of feedback you're separating your speakers from your microphone so your microphone can't hear itself coming out of the speaker this again is one of the easiest things that you can do and with a little bit of pre-planning this solves a lot of your feedback issues okay so now you're muting all the microphones that you're not you using and your speakers are out in front of your microphone and you're still getting audio feedback what could be causing this depending on the room or environment that you're in you may have some frequencies that are reverberating or resonating more than others a very well known fact is if you're in a ballroom medium or large Ballroom somewhere around 300 to 500 Hertz typically around 400 is going to be exceptionally prone to getting audio feedback if you can reduce that 400 Hertz just by 6 DB or something like that that will knock out one of your biggest feedback issues the same thing goes in a gym but you there is some variability to do this so how do you dial it in and you don't just want to memorize it because it's not always the same for every room so how do you figure this out so there's two methods that you can EQ your audio mixer in order to remove some more feedback if you've done some of the other steps that we talked about one is that the channel level and the other is at the main stereo output level so say you have five lav mics at a corporate event they're all the same microphone and you have this panel discussion I wouldn't EQ each one individually if I knew that this is all the event was it was just this corporate meeting or interview or something like that I would just EQ the main and solve the problem and be done with it like I say the channel EQ for optimizing each presenter's voice but if you're at an event and there's a choir performance and the choir mics are the problem and the rest of your sound system sounds great then I would just EQ the feedback out of those choir mics for example let's take a look at what that looks like and how I actually do it in practice okay first of all let's look at doing this at the channel level so say you have one microphone like a Podium microphone or a lapel microphone that is really susceptible to feedback you don't want to EQ your main output you just want to do this one microphone the first thing I would do on that microphone is I would high pass it so on an analog audio mixer like this one you can just click the high pass filter or on a digital audio mixer you would click the high pass filter and then sweep it to where you want it to be basically what you're trying to do is you're trying to take this microphone or the problem microphone out of the subwoofer of your event you don't need a microphone like this responding in the subs below 80 100 or 120 hertz you can just high pass it and that removes some of the problem frequencies if you're getting low rumbles or if you're hearing stage Stomps or something like that next thing that you can do if you're on analog audio mixer is you can try turning these knobs so say you have a little bit of high feedback and then a little bit of low now this is a trap that a lot of people fall into is they start up here removing a little bit of gain from the higher frequencies around 10K then they remove a little bit of 2.5 k with the mid and then they remove a little bit of the 100 Hertz with the low now when you look at this have you eq'd anything nope you've just actually turned your whole microphone channel down you've turned all frequencies down so if you're going this way try to just do one or two pots something like that will usually solve some feedback issues now that's something that you can do if you have a three-pot analog audio console but what happens if you have a mid sweep a midsuit makes it actually quite a bit easier what I do is I make sure the microphone is on I bring it up until it starts to ring a little bit then I reduce the mid by minus 15 DB and then I do the sweep this mid-sweep knob I aim for around that 400 Hertz in the area because I know that's usually a problem and then you'll hear the audio resolve you always keep one finger on the main fader of your audio mixer because then you can you know reduce the feedback if it's becoming too big of a problem but as you find the problem frequency you'll find that you can actually turn up the fader on the problem frequency back to where you were at zero or unity and then you can reduce the amount that you reduced of that you know 400 Hertz dip that we're doing here a little bit if you want some of those other surrounding frequencies back but a lot of the times this is something that you can do and it'll take less than 10 seconds and solve your feedback issue in a lot of different environments okay so that works for one or two channels but what happens if you have just a wide frequency spectrum that's affecting all microphones and your feedback is just totally out of control then you can use your main output run it through a 31b band EQ or if you're using a digital audio mixer it'll have a 31 band EQ built in so how does this work in practical application I would unmute all the microphones on the Yamaha instead of a mute you have an on button so you turn them all on make sure that your mix is set your microphones are hot and then you put one finger usually my thumb on the main output you drive that main output until you start to get feedback and then you go over to your 31 band EQ and you start notching out various frequencies now how this works is you generally will find three or four frequencies that are causing the problem and you can reduce them by about 6 DB or so if that doesn't work for you then you can reduce a couple more frequencies by maybe -3 DB or so and you might be wondering how do you figure this out how do you know which ones to turn down do I need sophisticated ears actually you can do this All by sight now if you're doing this on a digital audio mixer you'll be using your faders as your 31 band EQ and your red Peak lights will light up at whatever the problem frequency is so you just bring that down by 6 DB same thing on an outboard 31 band EQ there's some sort of light on a lot of them now so if you just see where the problem frequencies are and reduce those frequencies accordingly and then hopefully you can get your main fader back to zero DB and you have no feedback you can use the same technique on your main speakers or your floor monitors it's exactly the same way you unmute the mics you crank it up keep one thumb on your main output and then reduce the problem frequencies on your 31 band EQ now the next thing that you can do sometimes is you can control the types of microphones that are getting used the reason I say sometimes is because sometimes you don't have any control you're hired as an audio engineer and you don't get to pick the microphones that are on the stage maybe you're just being brought in for the day maybe the band has a tech Rider where their microphones are already specified maybe there's just certain go-to microphones like condenser microphone at the podium that you have no control over but generally speaking in a live event if you get free choice you want to use as many Dynamic microphones as possible if you know how a dynamic microphone works you're literally pushing a coil around a magnet it's a really physical process that responds better to voice sources that are right in front of the microphone condenser microphones are a lot more sensitive and they're a lot more prone to picking up room noise and that reverberation of certain frequencies in the room but ultimately you still use condenser microphones on things like live pianos symbols some types of guitars so you really don't get a choice but if you do get a choice try to use as many Dynamic microphones like the Shure sm58 as possible now the last thing that you can do is reduce your overall volume both out in the main house and on the stage you can reduce that volume out in the house if that's an option to you you can do that and that will solve your feedback audio issues but in a lot of cases you need to still reach a minimum SPL in order to be effective and having a sound system so you really can't turn it down too much you still need to be heard from the stage so a couple other things that you can do is you can turn down the volume of your floor wedges for the musicians you can give them a little bit less than they want and hopefully they can do deal with it or you find some compromise that is workable where they can hear themselves enough to monitor but you're not getting feedback now the other easy option was not easy but it is a best case situation is put your musicians or everybody on the stage on in-ear monitors that gets rid of all the other you know floor wedges and monitors on the stage and the stage is much quieter and much much less prone to feedback so if you have the option and the budget going to in-ear monitoring system really is a good situation in terms of reducing your overall volume giving you more control over the audio mixer and giving you a higher quality production value out for the guests that are watching or viewing the event I hope this video has been helpful I hope I explained these five tips in a way that makes sense for you and your workflow if you have any questions or comments about this please leave a comment down in the comment section below again if you do want to see more videos like this in the future please like And subscribe thank you for watching foreign

Channel: Kettner Creative

Views: 38,147

Keywords: 31 band eq, audio engineering, audio feedback, audio mixer, condenser microphone, dynamic microphone, eq, equalizer, event profs, feedback, feedback loop, live sound, microphone feedback sound effect, microphone placement, sound design, speaker placement, squeeling

Id: pfqPiQupaIA

Length: 15min 31sec (931 seconds)

Published: Thu May 04 2023