What is EQ and why is it an important factor in improving sound?

I remember it like it was yesterday: sitting in my car cranking up Van Halen’s 5150 and spending the entire album fiddling with the 10-band EQ I’d installed to get the best sound possible.

You don’t see a lot of physical equalizers these days, which is sad because they were always so cool to have. Instead, most everything is software-driven now. And that’s fine. It may not be “audiophile-level fine” but at least it’s something.

For those who didn’t spend their youth trying to tweak every knob and button on a stereo rack to get the best sound possible from their speakers, you might be wondering, “What is this EQ of which he speaks?”

Let me explain.

What’s the frequency…

One of the ways sound is measured is in periodic vibrations, which is hertz (or Hz), which is the property of sound that determines pitch. Humans have a finite range of frequencies they can hear, specifically, 20 to 20,000 Hz. Those frequencies are broken into octaves which are:

16 – 32 Hz – the lowest notes humans can hear.
32 – 512 – the frequencies of rhythm (lower and upper bass notes)

512 – 2,048 – the range where the human voice is located

2,048 – 8,192 – the range where labial and fricative sounds are

8,192 – 16,384 – the range of brilliance, bells, cymbals, and sibilance

16,384 – 32,786 – nebulous sounds passing the upper range of human hearing

How does that work out in a way that’s better understandable? To break frequency down into simplest terms, you have:

Lows – the first two entries in the list above
Mids – the third and fourth entries in the list above
Highs – the final three entries in the list above

What an equalizer does is allow you to raise or lower the levels of specific frequencies and different EQs offer different amounts of adjustments. For example, you might some cheaper earbuds with an included app that offers a custom EQ option but the EQ is limited to three bands. Usually, three-band EQs allow for adjustments of lows, mids, and highs. The problem with three-band EQ is that you have zero precise control. In other words, if you raise the “lows” in a three-band EQ, your raising everything from 16 – 512 Hz. What is that a problem? Say you want more kick drum in the mix. If you bump the lows up in a three-band EQ, you’re not only boosting the sound of the lowest frequencies but also the higher end of the lows, so the sound can get a bit muddy.

Bump that three-band EQ to a five-band EQ and you get a bit more control. A typical five-band EQ might give you the ability to raise specific frequencies, such as 60 Hz, 230 Hz, 910 Hz, 3,600 Hz, and 14,000 Hz. Now you can bump up 60 Hz and get a bit more kick drum in your mix. At the same time, you can lower 910 Hz to lose a bit of that tinny sound (too much midrange and the sound gets very tinny).

A ten-band EQ might be broken down into:

31.25Hz
62.5Hz
125Hz
250Hz
500Hz
1kHz
2kHz
4kHz
8kHz
16kHz

Note: kHz is kiloherz

Now, we’re talking.

I’ve used 32-band equalizers and you can imagine how much time I’ve spent tweaking those. In larger EQs sound is typically broken down into low, low/mid, high/mid, and high. Every EQ is different but they all do the same thing… raise or lower specific frequencies to change the overall sound produced by a device.

Why use EQ?

Let’s say you just purchased a pair of earbuds and out of the box they sound cheap. Usually, cheap headphones and earbuds share similar sonic palettes – little bass, overamped mids, and dull highs. You’ve heard them before; everyone has. 

That’s where EQ can come in handy. Many Bluetooth earbuds suggest you download and install the accompanying app, which often includes EQ. Install the app, connect it with your earbuds, and make the following adjustments:

Increase the lows
Decrease the mids
Increase the highs

Make it a nice sloping curve down to the mids and a rising curve to the highs. Now, play your favorite song and see how those inexpensive earbuds sound now. Vast improvement, right?

You might also find the app has a few presets to choose from, which are often categorized into music genres. As you might expect, the sound of different musical genres is improved by adjusting certain frequencies. For example, if metal is your jam, you’ll want to boost lows and highs but be careful about bumping up mid/lows, otherwise, the sound will get muddy. If you listen to a lot of podcasts, you’ll want to boost the mids, because the human voice is front and center. Classical music tends to benefit from a fairly flat EQ when listened through headphones or earbuds but can really come alive with some added bass and highs when listening through speakers.

EQ is a personal matter

The thing about EQ is that it’s very personal. You can talk to 100 sound nerds or audiophiles and hear 100 different opinions. The most important thing for you is to find out what EQ curve best suits your needs. And because everyone’s hearing is slightly different (for example, I’ve lost about 50% of the hearing in my right ear, so I have trouble hearing highs unless they’re bumped a bit more than usual). I know exactly how to set an EQ to perfectly fit my taste. 

It’s not just about your hearing either. You also have to take into consideration your equipment, the room in which you are listening, ambient noise, etc. All of those things play into how you’ll adjust the equalization to get the most out of what you’re listening to. And if you have an attached subwoofer, you’re talking about yet another layer of consideration (do you let the crossover only send the lowest frequencies to the sub or do you give it a bit more?).

After using EQ long enough, you’ll have the same understanding and can quickly adjust the sliders of your EQ (be they physical or digital) to achieve the best sound possible.

Any chance I can get to improve the sound I hear, I’ll take it. If that means using an EQ, I’ll do it… and happily so. The only word of warning I’ll give you is that EQ is a deep rabbit hole to dive into. At the same time, it’s a very rewarding chase for perfection.