– Or: Frequency manipulation CAN BE FUN with more tools

Ahh yes, back to the equalizer.  Effective, and my job to make it effable.  Aye, he’s (she’s) a tricky one, eh?  Getting a handle on how equalizers work is an endeavor that will leave you laughing or crying, one or the other with not much middle ground. Another topic might be more fun for a boy or a girl and it’s not for the faint of heart.


Once you’re over that initial hump?  Playing with an equalizer is another way to fill your heart with joy.  Placing that first EQ high up in your effects rack raises the stakes in making music reach the minds and hearts of listeners all over the world.  The ache of inexperience of the average engineer is something he’s (or she’s) going to eventually let go of.  Pretty soon they’ll be telling you how much they loved learning all about these wonky things.

In case you need a few more examples – or seven – and you feel like equalizers are still like foreign languages, hopefully this blog is a diamond in the rough and your life as a budding audio engineer (read: lover of tweaking knobs) is about to sprout and blossom.  Boy howdy. We are going to move on in the direction of more complicated concepts to fill the space your keto-compatible fatty computer made of meat with minimum waste and maximum know-power. Maybe even a little bit of joy along the way.

Let’s dim the city lights and get down to business!

The Equalizer Band Pass Filter

Band nights are not as fun when you filter out all their passes and require them to pay for their own tickets.  They typically can’t even afford a ride on the streetcar. But that’s another story. The band pass filter!  If you have a desire for hearing only a range of some higher frequencies without the heights of the air range and you’ve said “No” to the bass range, band pass is the place for you.

To be implementing this concept, you’ll be starting to ramp up at a specific frequency and then ending at another one, cutting not one side but both.  It looks an awful lot like two filters in one: high pass somewhere to the left, and low pass somewhere to the right.  Once you start messing with this concept, there’s no need to ask for much more. Except maybe for a side of bacon. Nueske’s preferably.  Because dang.

You could just get some other engineer to do it for you; she’s (or he’s) probably delighted to do so.  But if your goal is to be all smooth and suave in the studio, you’re going to have to learn to be the operator of these fancy things.

Boring trivia note: we’ll get later into how the coast to coast differences between LA and New York impact some of the creative uses of compressors (don’t even mention Chicago. midwest ain’t got nuthin on the ocean shores) but equalizer usage is pretty western / eastern agnostic.  Male and female alike.

Please align your vision to this north star of a video linked below for an example and reference.

The Equalizer Notch Filter

Notch filters are great.  They look like a giant dip to the south pole (or Australia?) where frequencies just drop off and cease to exist.  As an aside, if they could make a filter that sends me to Key Largo?  That would be grand and I am here for that.

I personally love the notch filter in an equalizer for the single purpose of how it’s the opposite of the Band Pass Filter from above: High pass to the right, Low Pass to the left. Frequency in the middle for sale: sold. Like two pass filters face to face, each jockeying for supremacy.  A classic case of the black hole of frequency cutting.  We find the dip in the shadow of two passes.  Sorry, I’m waxing all poetic in this box of text. Pardon my silliness and wonkification.

Double up those pass filters and you get a valley where they don’t cross and just eliminate completely.  Yet why would we need this?  Electrical hum can be a problem in some cases, and in others the problem isn’t easily found and we chase after it sweeping back and forth like we have a license to fly that thing.  Gotta love it, eh?

(it’s a good thing we don’t need insurance to do these things.  nobody would let me ever hold that card!)

If solving an electrical hum challenge isn’t possible, this notch melts all your cares away, with only bad memories of a refrigerator interfering with your recording process and mixing practice.

In what is absolutely NOT a change of pace, I present to you a video to dive into.  There might be some gold contained within.

(be gentle with the author: his eyes are still kinda glazed over like a cheap doughnut after staring at the screen recording videos all evening.)

The Equalizer Bell Shape

Oh look!  Little town, it’s a quiet village.  Wait. No.  Reset.

The bell shape of equalization.  Unfortunately, no angels will descend from the heavens just for using one of these things, but the artist listening to your work might think you are one and her (or his) opinion is the only one that counts.

But seriously, this is one of the more common equalizer shapes at the heart of boosting and cutting frequencies. This is the bread and butter of the cold hard equalizer and probably the shape that I use the most when all is said and done.  While a high pass filter goes on almost every channel I’m mixing that doesn’t require low end signals, after that it’s all bell shapes all the time.  That’s where the real surgical work gets done.  Boosting the low end to emphasize a kick drum or the air frequencies of the human voice? Cutting out all that mud we have been talking about or scooping out some mid range interference to make room for something else?  All of it bell shapes.

The level of versatility available in a bell shape – once you start messing around with Gain and Q – is so vital to everything we do here.  Gain and Q are coming up in a second, but fore now take a goose at the example video below.

Gain and Q

As much as I’d love for the rest of this blog post to be about weight lifting and Star Trek: The Next Generation, we’re going in a different direction.

In this context, Gain is all about amplitude.  Volume at specific frequencies in this case.  When you are interested in boosting the effect of just one bit of the range, you add amplitude – in the positive – to it and the shape will rise and lo and behold, you have increased the impact of those frequencies.  The same thing applies to cutting.  You go into the negative and remove that influence.  Visually using the bell shape as an example, it would look like you’re pushing up or pulling down.

After that is where Q comes in.  Q is short for Quality in this case.  Within the context of an equalizer bell shape again, when you modify the Q of the shape it’s going to either grow broader and wider, or pinch in and go very narrow.  The Q will define just how MUCH of the frequency range you’re going to tweak out.  So say your room has a really obnoxious resonant frequency at around 247hz.  Everything else sounds great but because of the way the room is designed you still have a weird and obnoxious buildup of 247hz in everything you do.  You can add a bell shape, go into the negative of gain and pull it down, and then narrow down the Q until it’s pretty much just reducing the impact of that one frequency right there.  Problem solved!

Ideally, you’d fix the room.  In the absence of being able to fix the room, you get to “fix it in post” as the saying goes.

Once again!  Another video demonstrating visually and audibly what on earth it is that I am trying to write about in text.  The last one for this entry!

That’s it for this one!

That concludes this section of the audio engineering obsession that I like to call The Equalizer.  At some point, I’d like to do one more follow-up where I take examples of something that either sounds off or sounds great and I want to enhance and make a video demonstrating the differences.  It’s a fun exercise to watch and listen to how some very subtle changes can completely remap the framework of a sound. Demonstrating with extreme curves and amplitudes, setting at very subtle, and then comparing what they sound like both on and off.  It’s eye-opening!  Mind blowing!  Finger snapping!  Insert different metaphor here!

So either that is going to be next or I’m going to instead dive into Compressors.  Can’t decide which.  It’ll be a surprise!

For both of us!

Hope you’ll come back next time!

-= george =-



Are we having fun yet?

About the Author

Straddling the line between the arts - voiceover, music composition, session performer, album mixing - and the world of durable medical equipment. Probably should have spent more time playing on the balance beam as a kid instead of obsessing over Commodore 64 games.

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