VO Software Tools: Filters, EQ, Equalization

“Equalization” could make things “Equal”…
But it might not sound very good

Equalization can seem like a tricky topic. That’s not helped by its relatively vague name. After all, what exactly are we trying to make “equal”? Confusion often compounds as this is one of those situations where several different terms are used to talk about the same thing. 

For example, there is an audio tool called a “High Pass Filter” which lets the higher audio frequencies pass through and cuts the low frequencies. There is also a tool called a “Low Cut Filter” which cuts the low frequencies and lets the high frequencies pass through. Those two different terms are describing the same process.

Just like in math, where 7+3 is the same as 3+7, these two “different” Filters create identical results. They are different names for the exact same tool. Low Cut is the same as a High Pass.  

Once you start paying attention to different filtering terminology, you’ll hear “bandpass,” “shelf,” “band stop,” “notch,” and all kinds of other specialty phrases getting thrown around. 

The first thing to understand is that Equalization is simply the process of Filtering. If we say Filter, we are talking about Equalization, and “EQ” is shorthand for that term. 

Filtering = Equalization = EQ

When we use a Filter or EQ, we are using that tool to increase or decrease a specific part of the frequency range. Different types of Filters can make that easier. 

If we wanted to reduce things at 440 Hz (the frequency of an “A” in music), a Graphic EQ has fixed frequency bands where you can increase or decrease the signal. A 31 Band Graphic EQ has a band at 400 Hz. That wouldn’t line up exactly with 440 Hz, but it would be pretty close. Below I’ve reduced the 400 Hz band by -9 dB.

A Parametric EQ lets you position the filter frequency band anywhere you want, so you could make a cut right at 440 Hz. In the image below, I’ve made a very narrow cut which you can see on the screen.  

One of the nice things about a Parametric EQ is that you can also control the “Width” or “Q” of the filter you apply – below you’ll see that same 440 Hz position with a much wider curve. That wider curve will affect more frequencies to either side of the chosen position. 

The Graphic EQ (and some other types) have a preset width (which varies by the band you choose). It doesn’t show it onscreen, so you need to listen for overall changes to your audio. 

One of the most commonly recommended practices for raw VO recording is to use a High Pass Filter. This will often drop the noise floor of your recordings and should reduce any rumble present in your recordings. A good place to start would be around 60-80 Hz for average male voices and 70-90 Hz for most female voices. You could create a High Pass Filter with both a Graphic EQ or a Parametric.

And there is often a specific “High Pass Filter” tool (the Apple AU-Highpass is shown below) which does this.

Filters/EQ/Equalization – How do we best use these tools?

For most of my clients, I’ll first set up a High Pass filter. Almost everyone’s studio has some sort of low frequency rumble. That’s really the sound of the environment, transmitted through the structure. 

If their recording space sounds good and they end up with good audio, I’ll stop. That’s ideal.

⁠Frequently though, there are imperfections in the space or input chain that have me making EQ adjustments up into the higher frequencies in order to let them achieve their best sound. (I’ll then save those into Presets or Stacks as I’ve discussed before). Precisely what corrections depends upon the space they are in, the microphone they are using, and the timbre of their voice. Generally, I’m using Equalization to make them sound more like them. In other words, I’m using it prescriptively to balance the tone rather than as an Effect to make them sound radically different. 

In the end, Equalization can combine multiple Filter steps (i.e. High Pass, Low Pass, other cuts) into a single EQ step – so you might see a Parametric set up with both a High Pass and selective cuts. EQ behaves really well with multiple passes, so you can break out those individual steps or combine them and things should sound the same. I do generally like a High Pass step first, as it removes stuff that’s just going to get in the way later  – and I’d prefer a Filter rather than using Noise Reduction or other more complex tools. 

As I mentioned above, even though these things are being shown on your screen, we always want to run the audio through our ears. After a while of working with these tools, you will get a better sense of how the visuals might suggest a result, but the best practice is to always listen for the specific changes a filter makes to your audio. 

The NOVA EQ from Tokyo Dawn Records – a serious tool available for free

I’ve been using this free EQ for years – if nothing else it provides and excellent 4 section parametric EQ with separate High Pass and Low Pass filters. But if you poke around under the hood, you’ll find all kinds of uses for the dynamic Threshold (like a solid de-esser).
Download it here – https://www.tokyodawn.net/tdr-nova/

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