Canadian Musician - March/April 2017 | Page 60

LIVE SOUND

Drew Robertson is an audio engineer , live sound tech , and educator . He is based out of London , ON , is the co-owner of Prosperity Audio Works , and also co-hosts The Double Platinum Podcast .
He can be reached at contact @ prosperityaudio . com .
By Drew Robertson

Shooting the Room

A good live sound engineer is often the silent hero of any venue or show . A show can live or die based on how we handle the mix and nothing can ruin anyone ’ s evening faster than feedback . Thankfully , there ’ s a variety of tools readily available to stop the sonic pest before it even begins , the most common being the equalizer . Events can be barely organized chaos , but if you can find yourself a few minutes pre-show , are comfortable with a microphone , and know your way around an equalizer , you will be able to make your life much easier once the band strikes up .

The Concept Feedback in essence is a self-reinforcing signal loop within a system , which in our case happens to be when a mic on stage picks up sound coming from an amp , monitor , or even the mains and continues to feed that sound back into the system . Feedback comes out as high-pitched squeals that can gain enough volume to not only damage hearing , but equipment as well . So , the question is , how do we fix it ?
The first solution , besides physically altering the layout of the stage , is to turn down the volume of the speakers or mics , but that has a few down sides . First of all , if you ’ re lowering the main volume , then your audience is not getting the full experience and the show suffers , or you turn the monitors down and the band cannot hear each other . If you have more than one active mic on stage , tracking down which one is the source of the offending noise can be a nightmare and result in a complete breakdown of the mix integrity , leaving everyone with a terrible experience and you out of a job .
So , how do we tackle the problem without killing the sound ? Easy . You use an equalizer .
Most modern live sound consoles will have a master equalizer – usually as a multiband GEQ or graphic equalizer . These types of equalizers normally appear in the master or mains section of the console and have anywhere from seven to 31 bands . Each band represents a specific frequency between 20 Hz and 20 kHz and can either be boosted or cut . If your front of house system doesn ’ t have a built-in master EQ , I would highly recommend having an external one that can be rack mounted and kept in line with the mains . Some consoles , especially newer digital consoles , offer built-in feedback suppression / detection systems that will aid in locating and eliminating problem frequencies .
The Method The idea is fairly simple . During or before sound check , take a few moments with an audio source and see just how loud you can push the system before feedback or distortion . Once you ’ ve established that base line , you can begin to track down the trouble frequencies in the room .
Simply playing some appropriate music will often create some feedback or highlight some uncomfortable frequencies that you can start reining in . If you have a partner or a wireless control solution , I would recommend getting on stage with a mic and doing your best to create feedback under normal conditions . ( By that I mean don ’ t purposely create a feedback loop by pointing the mic directly at a speaker ; instead , push the gain as loud as you can without clipping and start talking and see what rings out as feedback .)
As sound check progresses , you can get a feel for how loud you will be able to push the sound , adjusting your master EQ as needed to eliminate the trouble frequencies . One thing to keep in mind is that every room will be different . There is no master guide or general rule on what specific frequency a band will need to be adjusted . That said , you can also pair your master EQ with judicious use of each instrument ’ s own EQ . You should never just flat out eliminate all the high end of your system just because it might make a terrible noise . Use good judgment and stage your EQ in context to the music being performed . Basically , use your ears and common sense .
Speed & Efficiency While there is no “ one size fits all ” approach to feedback busting , the more you become accustomed to listening to and tweaking the sound when it happens , the faster you will get at eliminating the problem . As you get faster and use the skill more often , you will be able to draw on past experience to plan out future gigs and give yourself a good reference point for what might need adjusting . You may be in a situation where you do not have the ability to EQ each main and monitor individually . That doesn ’ t mean you can ’ t still put your skills to good use . Follow the same procedures where you can and you will get the most out of your sound systems and stay feedback free . It ’ s never a bad idea to “ shoot ” the room with sound and see what sounds out of place – that knowledge can only lead to a better mix when the band starts playing .
Knowing how to size up and ring out a room for sound is an essential skill for any live sound engineer . It is one of those “ secret bag of tricks ” skills that can come in handy at any show and will certainly be appreciated by everyone involved . As you progress in live sound , you will pick out trouble frequencies and fix the situation before anyone knows there is a problem . The band will sound great and you will look like the pro that you are .
60 • CANADIAN MUSICIAN