The Delicate Art of Killing Squeal
~ as Published in Rockstar Magazine July 2014 ~
By: Christopher Jordan
So there you are. The stage is set in the corner, everybody is tuned up and the natives are getting restless. You step up to the microphone to say your howdys and introduce yourself for the evening when suddenly, louder than a banshee and faster than a typhoon it comes at you. The loudest, most shrill noise you’ve ever heard. As you turn away from the microphone and wipe the blood away from your ears, you curse your non-existent sound man, the guy who brought him here and whoever it was that booked this gig. Oops, only one problem…all those people are you!
This is the all too common issue facing a great percentage of you who are just starting out and even quite a few of you veteran weekend warriors of the stage. Hey let’s admit it, not all of us are gear heads, not all of us are audio engineers and we’ve all had the problem of the anticipatory grimaced face as we approach the microphone. In case you haven’t cued onto it by now this article is about feedback. Not the honest open criticism type that you wish people would give you; but the kind that kills ears, shows and the evening’s fun for everyone around you. By the time you finish this you by far won’t be a pro. Sorry, it’s just really not as simple as 2+2=4. In fact if we wanted to we could get into the calculus and physics involved with calculating the resonant frequencies of the room and the slap-back delay of the far wall in proportion to the front of the main speakers and the rear of stage and dial it into perfection like the uber-pros. Heck even the humidity factors into it. But I think I just saw a couple of eyes glaze over, so in this article we’ll keep it instead to some super simple pointers that will help you with a general 8 input PA head or soundboard setup in a small venue environment. Honestly once you find and master your sweet spots in a small space it’s quite a bit easier to scale it up for larger venues.
Let’s start with the first likely culprit, stage volume. It’s a cascading chain of events that leads to what is technically known as a regenerative feedback loop. Here’s the scenario. You want to turn up your amp to rock out. When you do that, the singer now needs more vocals in the monitor because now his voice is buried and he can’t hear himself properly. He turns up the auxiliary monitor send on the lead microphones channel on the sound board to get a little more pepper in his mix and…SQUEEEEEEEEE. There you have it, a regenerative feedback loop arises and you’ve just given birth to a thirty year old deaf guitarist. The diagram below gives a very simple break down of the contributing factors involved in the creation of a typical regenerative feedback loop on stage.
Let’s get another perspective of what a feedback loop is. Imagine yourself in your local clothing store dressing room. You put on a pair of pants, turn to take a look and there is one mirror to your left and mirror to your right. Stand at just the right angle and you can see your front and your back individually, take one step to the left or right and whammo, there’s you and your new britches a thousand times over fading off to infinity in both directions. The exact same principle applies to audio. When you have the microphone gain coming into the board set just right the monitor speaker will sound perfect and your singer will be able to hear himself without a whole lot of effort. The less he can hear himself the louder he will have to sing. Again louder is not better. Singing in this way is how you miss notes and strain voices, neither of which is good for your singer or band as a whole. I know I harp on it, but stage volume truly makes such a huge difference to everything in a room mix. I don’t even mean that figuratively, literally everything starts with stage volume. Think about it, if you can’t hear the dude next to you talking without screaming your head off or using the microphone you my friend are entirely too loud. Quality of sound, not quantity of sound makes the difference here. “So short of having a sound guy in my back pocket and turning down a notch or two is there anything else that helps?”
I have mentioned in previous articles and will emphasize again here the many advantages to and importance of early arrivals. This extra time gives you the chance to “sus out” your system as we in the engineers say. This basically means finding the peak point at which the monitor speakers sustain the microphone signal on their own and begin to feedback. This is done for each microphone on stage. That’s right boys and girls, the audio engineer’s dirtiest secret is that we know exactly how to break things “just right” as were. Yeah you heard me. We make the speakers feedback on purpose. This is a tedious and yes dangerous process, but a good one and essential to know if you gig regularly and value your ears. You begin by setting the channel EQs to center and the volume fader or knob to unity. Then you begin to ever so slowly increase the channel input gain from the zero point until you hear the microphone start to swell with feedback. At this point you back off the gain until the squeal stops and you now have a gain level that you should consider your new “maximum” gain for that channel because you now know that if you go higher you will start feeding back. At this point you can set EQs to sweeten the mix and repeat the process a second time for good measure. From there it’s wash, rinse repeat for every channel on the board that will incorporate a microphone. It may take some time, but practice regularly with your system in your rehearsal space and get it down there. Just like playing an instrument, learning to “sus out” a system takes time and practice.
Another tip is to strip inputs. Yeah you heard me, strip ‘em! Everything in your band need not be running through every monitor. If this is the case please refer back two paragraphs and re-read the part about turning stage volume down. When it comes to monitors it all makes an incremental difference. If you don’t need a microphone in front of the bass amp then for goodness sake don’t put one there. Every microphone on stage is one more opportunity for the demon of feedback to raise his vile head and wreak havoc on you and your audience. Try to only have what you absolutely need present in the monitors. Inputs such as vocals, soft acoustic instruments, cue points such as backing tracks that are played to and perhaps a bit of kick, that is after all what I think we are all following. Anyway, you get the point, when it comes to monitor mixes less is more.
Finally a couple of simple notes for the singers, the front men, the faces, the ones whom everyone immediately goes gaga for and recognizes eight blocks away. I cannot emphasize to you enough the importance of proper microphone technique. It starts with as I said previously, singing. If you are screaming real loud undesired frequencies can tend to be emphasized vocally and things can be muddled and unintelligible. Add to this a microphone and all you get is well, amplified unintelligible. You must as any musician care for your instrument properly and practice, practice, practice. Proper singing comes from the diaphragm and not the lungs. Once learned singing with proper projection is actually worlds easier than screaming really loud. Work your core and build endurance by jogging or taking a bike ride with some regularity, really any exercise works. Every little bit helps when it comes to hitting and sustaining the high notes. Also, remember when I said how we audio engineers make the speakers feedback on purpose? Well to do that we physically hold the microphone in a semi-cupped hand and point it down toward the monitor speaker. Sound familiar?
Cupping the microphone blocks the sound frequencies from passing all the way past the diaphragm of the microphone. Instead they are directed back the very short distance to your face and reprocessed by the diaphragm of the microphone. This results in a mild rippling effect on the diaphragm of the microphone instead of a clear forward and back motion resulting in a muddied almost woofy sound and when pointed at the speaker…well like I said before, that’s our secret to making them feedback. It’s called a resonant chamber and this effect is generally undesirable and does not provide for clean clearly distinguishable frequencies. I know, I know. It looks epic. But hey, think of it this way. You are such a freakin’ rock star that when you hold your microphone properly it’s going to set a trend that will take the world by storm and ROCKSTAR magazine will want to interview your band about your new trend setting sound. As a result every band coming up will want to emulate you and will begin to hold their microphones as you do and you and your band will have eliminated the regenerative feedback loop on stage for all future generations and let’s be real, we all want that.
So until our next installment spend some quality time to get more intimate with your gear guys and gals. It’s the easiest way to find the sweet spots on your amps, trouble frequencies in speakers and that perfect stage volume that allows the speakers to do the work for you. Happy hearing and may your stage now be freed of the infernal squeal.
~Christopher Jordan has been a live audio/video engineer and recording artist for over 15 years and owns AustinHotMods.com an Austin,TX based pedal modification and repair company.~