Study Hall

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EQ Boot Camp: A Regimented Approach To Effective Equalization

In a properly designed audio system, EQs are like nuts and bolts: each one has a specific job to do.

Avoiding The Spiral

Here’s the part where people get very nervous: to start things off, input and output EQs should be flat. Get rid of all those wacky cuts. What usually happens is that people add them one at a time to deal with who knows what, until we look down one day and realize we’ve had it set that way for years and no one knows what the original problem was.

It’s considered bad manners (apparently) to add salt to a meal before tasting it – how do you know if it needed salt? We’re often guilty of the audio equivalent. Don’t add a filter to correct for something until you’ve listened to see if something needs to be corrected.

The other day I used my “standard” Shure SM58 EQ curve on a vocal mic from a different manufacturer, and the result was awful. This was my fault because I was just guessing, not basing my EQ decision on anything I heard. Don’t guess.

Listen, and then make an adjustment if, and only if, one is warranted. The layers of “this is what I always do” EQ stack upon the “it’s always been that way” EQ and next thing you know we’re back to trying to tune the PA with input channel EQs.

Don’t be scared to zero everything out. If it’s digital, save a file. If it’s analog, snap a photo on your phone. Now if we really goof things up, we can always put it back the way it was. EQ is a functional part of the sound system that’s there for a reason, so ignoring it is not helpful. Don’t let that equalizer boss you around. Make it work for you.

Now let’s get the outputs right. Using a familiar CD and a pair of quality headphones, adjust the output EQ until the playback in the room is a good tonal match to the headphones. Focus on broad strokes, not minor details. It helps to envision a tilting see-saw: too much LF, too much HF, or just right?

Remember, we’re not optimizing the system’s coverage over the space; that’s a job for the system tech. We’re just making basic tonal adjustments to the system as a whole, as you do in your car.

Dialing It In

Imagine using the house music to do this at a festival or club, when your act doesn’t get a sound check. By confirming the proper tonal balance of the “downstream” half of the system – everything after the console outputs – we’ve effectively ensured that the inputs will sound pretty much the same as they do in our headphones, allowing us to dial in adjustments on key channels with the house music still playing. And, of course, since we used the output EQ to tune the output, our input EQs are available for the task. (A nod to Dave Rat for this trick.)

From a touring perspective, this also means the specifics of the PA and room should have a minimal effect on how we treat our input channels. Compensate for day-to-day variations using the output EQ, and the mix should be relatively undisturbed.

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If monitors feed back, use the proper output EQ to reduce the offending frequency. I use very narrow parametric filters in the digital realm to minimize collateral damage to the mix – wider filters affect a larger frequency range than necessary. With analog, trusty old 31-band graphic EQs will do the job. This is better than dealing with the problem at the input because input EQ filters are generally much wider, and this would produce an unwanted tonal change to the sound of that input for everyone, not just the problematic mix.

In the church environment, an important exception is for pulpit/podium mics. The goal is maximum gain before feedback in the house, and pulpit mics will almost always feed back in the mains before the monitors. In this case, I’ll insert a graphic EQ or a second parametric on this input so I can ring it out without chopping up my main output EQ.

It’s reasonable to ask, “How do I know which frequencies to cut?” The disappointingly realistic answer is “experience.” A more helpful answer: if something sounds funky, dial in a gentle boost and sweep it through the frequency range until it sounds really funky, and then cut there.

Over time you’ll build mental association between certain tonal problems and the relevant frequency ranges. You can develop this ability by sweeping EQ filters through recorded music and pink noise, and considering the effect, you may also find a spectrum analyzer (FFT or RTA) helpful to train your ears, but don’t come to rely on it, especially when it comes to feedback. If feedback is visually obvious on an analyzer, it’s likely intolerably bad in the room.

Feedback “suppressors” have the same problem – they’re reactive. If you train your ears properly, you can be proactive and catch it while it’s still just “ringing.”

Keeping It Minimal

Once, at a show, a crew member asked me what I was doing in terms of input EQ. At this particular gig, there were great musicians on nice instruments, good mics in the right spot, and a good PA, so the answer was “not much.” I had high-pass filters and a handful of parametric filters in place, but nothing crazy. If you do everything else right, there’s not much to correct for!

You’ll notice that we spent relatively little time discussing the act of actually adjusting EQ. That’s because I’ve found that most of the problems in worship audio arise from operators being unsure which EQ to adjust, or being told not to adjust an EQ, or trying to use one EQ to compensate for another EQ that was poorly adjusted by someone else.

In most cases, once you’ve gotten all your equalization ducks in a row, you’ll be shocked at how little EQ you actually need to get things sounding good.

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