Crazy Audio Thoughts #1: How cutting “air” frequencies can make you a better mixer

Every now and then I stumble across something that not only changes the way I work, but my entire outlook.

I remember the first time I used an “air” band on an eq. It was 2003 and I had just started the masters program at McGill. Amongst the units I had only dreamed of using was the famed GML eq. And to the right edge of the front panel…the elusive 26 kHz setting.

Humans can only hear up to 20 kHz, so why bother boosting above that? By centring the EQ above 20k, you can affect the audible band with the left part of the EQ curve. In effect, creating a gentle high shelf — not dissimilar to a Baxandall curve.

And boy did it sound good. Whatever I would EQ would open up beautifully. At the time, there were no EQ plugins that offered anything above 20k, so this was like opening a door into a magical new universe of sound. I used it on everything. And I didn’t stop.

For most of my career, these air boosts (anywhere from ~ 12k to 30k) became common practice for me. It didn’t matter if I was recording, mixing or mastering. This was the magic sauce — or so I thought.

A year ago, I analyzed some masters by Howie Weinberg. And recently, Brian “Big Bass” Gardner and Mike Marsh. These some of the best mastering engineers in the world and they produce extraordinary results.

I spent hours comparing their masters to the mixes. Surprisingly, all three were cutting air. Cutting!?!? Before, the idea of cutting there wouldn’t have occurred to me.

This is when I had my epiphany. EQ is yin and yang. Every move has an opposite effect somewhere else in the spectrum.

For instance, boosting the lows is equivalent to reducing the highs. Cutting the low mids is equivalent to boosting the high mids (and lows for that matter). Or…boosting the air frequencies has the same effect as reducing the lows and mids. Ah-ha!

All these years, I thought I was opening up my tracks. Actually, I was killing the ranges where the energy and excitement resides. Balls!

So why was I doing it? And for the record, it wasn’t just me. This is a common issue I hear on client mixes. And if you read any of the mastering forums, you’ll see many people asking about the best EQ’s for “air”.

When we boost air, it provides instant gratification. As we do it, the track seems to sound better. The reason is we’re adding energy. In other words, we’re making the track louder.

Since we perceive louder sounds as better, it might sound like we’re improving the track. But if you were to compensate for the volume boost, you might find you’re damaging the music.

This applies to all boosts, which is why they can be dangerous. But unlike low boosts that can get muddy, or mid boosts that can get harsh, air frequencies are more forgiving. It’s easier to boost air without realizing that we’re weakening the sound.

For the last year or so, I’ve been conscious about the air range and have started cutting often. But today I went further.

I spent some time analyzing a Brian Gardner master. The amount he was cutting shocked me. Especially since this was on an impeccable Serban Ghenea mix. After hearing this, I tried revisiting some of my old work.

I brought up a couple old tracks. With fresh perspective, it was clear that ALL could use a reduction.

So, I did quick masters with that in mind and compared them to my previous work.

Boom! Each track was better. More exciting and powerful. And none felt dull. If I wanted to brighten the track, I concentrated on the 5–10k range instead.

So, how could you apply this to your work?

Don’t boost the top end on every track. Think about it this way. Lets say you have a track or mix where the bottom end feels great. Would you then take a low shelf and cut it out?

Of course you wouldn’t! But that’s what you’re doing when you thoughtlessly boost top end.

I’m not saying you should never boost air. But try listening to how it affects the rest of the spectrum.

And if you want to add presence or brightness, boosting in the 5–10kHz range will usually sound more powerful than 10–30kHz.

If you still need to open up your mix, try boosting air on one or two tracks only.

You’ll find a little goes a long way.

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