We’ve all seen music producers, engineers, and recording artists huddled around mixing boards, adjusting nobs and sliders to reach the exact sound they’re after, but such fine-tuning isn’t exclusive to the recording studio. In eras past, the equalizer (EQ) was adjusted using component-style graphic EQs, but for most devices you’ll encounter these days, it’s all done digitally.
EQ settings can now be found in everything from phones to wireless speakers, and even streaming services such as Spotify, but too often in the form of safe presets. Understanding how exactly an EQ works and using it properly is a much more elusive concept, and digital options with more depth than your typical “hip-hop” setting can be just as intimidating or confusing as rows of physical sliders.
Equalizers put the power of sound sculpting at your fingertips, and as they say, with great power comes great responsibility. And while an EQ isn’t a superpower, it can get you closer to the sound you want from your gear … if you know what you’re doing, and you will once you comb through our top-to-bottom guide to EQ.
Why do I want to use an EQ?
Electronics manufacturers have their own ideas about what a piece of gear should sound like, but EQ lets you have your say. Also, we don’t always get to listen to music in ideal environments. Many of us listen to music while commuting or exercising, where the shape of the room or ambient noise can each have a nasty effect on how our music sounds. An EQ can help.
The music you’re listening to also plays a factor. Not only do the natural sounds of the track respond uniquely to different EQ levels, but in the case of digital music, you may also need to cover imperfection introduced by certain file compression formats that can affect the overall audio quality. With these variables in play, an EQ serves an invaluable role for anyone serious about their jams. With it, you could pull out the distinctive shimmer of high-hat cymbals otherwise drowned by a dominant vocal track, or even help mellow out the narrator’s voice in an audiobook.
Maybe you have a bass-heavy pair of headphones that you need to tone down a bit. Or perhaps you listen to a lot of EDM, but the treble is too sharp and needs to be pulled back. Whether you’re looking for more punch, a warmer sound, or bass that will rattle your insides, an EQ can help you dial in the sound that suits you best.
What does an equalizer do?
At its most basic definition, an equalizer manipulates frequencies. The technology first took off as a piece of analog electronics that was initially used in recording studios before making its way into the home. Whether analog or digital, an EQ is used to adjust different elements of sound to achieve an end result that appeals to the listener.
You may associate EQ with effects like reverb or echo, or popular EQ presets like “Rock,” “Jazz,” or “Concert,” among others built into popular devices and headphones. But the kind of EQ we’re talking about simply offers control over the different sound registers to achieve a refined result. If used properly, EQ can smooth out audio for just the right touch, whether that means adding some beef to the low end, taking away some bite from the treble, or anything in between.
The graphical EQ — which is what we’re going to focus on for most of our walkthrough — looks like a graph (no kidding!) with frequencies on one axis and decibels (dB) on the other. From left to right, you’ll find “sliders” that allow you to adjust certain frequency bands up or down along the dB scale. Bass frequencies start on the left, with midrange frequencies in the middle and treble on the far right (like a piano).
If you’ve already got a firm grasp of what frequencies and decibels are, feel free to skip ahead to the “Playing with your EQ” section, or even our “Parametric EQ” examination (if you’re a heavy hitter). If not, the following little snippet of Acoustics 101 will probably come in handy.
All sounds — everything you hear — are essentially vibrations that we can visualize as waves moving up and down at different speeds, or frequencies. The faster the wave moves, the higher the pitch. For example, bass frequencies — such as those you hear in a hip-hop groove — move very slowly, while higher pitches (treble) like the chime of a triangle move very quickly.
Every pitch a musical instrument plays has a core frequency measured in hertz (Hz), which can be likened to a speedometer reading for the waveform. Hertz measures how many times (i.e., the frequency) a wave completes an up-and-down cycle in 1 second. If the wave moves up and down 50 times in a second, that’s expressed as 50Hz. At the theoretical limit, a human can hear from 20Hz to 20kHz (20,000 cycles). In reality, though, most human hearing tops out around 15kHz or 16kHz — the older you are, the less treble you can hear.
All of the sound you’ll ever hear lives in this 20Hz to 20kHz zone, and thus those are the numbers that will border your typical EQ. Most of the pitches your ears really focus on fall between 60Hz and 4kHz — that’s the meat of the sound. A piano’s highest note, for instance, lives at 4,186 Hz (around 4.2kHz). There are also sounds called overtones, and an EQ will affect them, too. These sounds — which primarily reside in the 10kHz to 14kHz range — aren’t something that your ears naturally hear, but they have an effect on the sound as a whole, so it’s important to keep this in mind when messing around with that section of the treble band.
The decibel (dB) is the unit of measurement used to express volume level or loudness. When you move a slider up or down on an EQ, you are increasing or decreasing the loudness of that particular frequency. It’s important to know that small dB adjustments can have a big effect on the sound, so tread lightly. It’s wise to start with a 1 dB to 2 dB change and move up or down from there. Since decibels use a logarithmic scale, a 5 dB or 10 dB change represents a dramatic increase or decrease to a particular frequency band.
Playing with your EQ
Finally, the fun part! Now that you’ve got a grip on what your EQ does, it’s time to start playing around with making adjustments. Go ahead and start playing some music that you are familiar with, pull up your EQ, and move some sliders up or down to hear in action what you’ve been reading about. You’ll soon find out that small adjustments can have a pretty wild effect on how things sound. Below, we’ll give some direction on how to approach things.
Almost any pro sound engineer will tell you the first thing you want to try with EQ is to decrease the level of a frequency, rather than increase others around it. Expanding too many frequencies can make the music sound muddled, and with a little shift here and there, you can subtract a bit of the irksome sound and get closer to what you’re looking for. That’s not to say an increase in a frequency range isn’t necessary at times, but you should always start with subtraction. Remember, too, that any change in EQ will not only affect the frequency range you’ve chosen but also how the rest of the frequencies interact with each other.
You may notice that it takes a moment after making an adjustment to hear the result. This is normal. It’s also normal that you may have to boost the overall volume after reducing any frequencies. For instance, if you want more bass and treble in general, you can pull down some of the midrange sliders, then boost the volume a bit and see what you think of the result. Not exactly right? Then it’s time to get more targeted with your adjustments, and for that, you’ll need to know what each frequency sounds like. We’ve got a guide for you at the end of this article that spells things out pretty nicely.
What about EQ presets?
EQ presets like “Rock” and “Jazz” are a quick-and-dirty way to get to a different kind of sound without a ton of effort. While these probably won’t give you the exact sound you’re looking for, they can be handy for getting you started. You might want to start with a preset, then customize it until it is just right. Some equalizers, such as the one built into iTunes and desktop versions of Apple Music (but only if you’re on Mac OSX Catalina, as the iOS version only has presets), will actually show you what the frequency curve looks like when you select a preset. This can help you understand what different EQ settings can do for you.
Parametric EQs are tricky, involved, and not for the faint of heart or inexperienced user. They’re generally reserved for recording/mixing, but they do show up in apps for speakers or headphones from time to time. Using a parametric EQ involves targeting frequencies with a band of around five to seven movable control points set along the happy 20Hz to 20kHz frequency spectrum mentioned above. Each of the points is visualized along the X/Y axis; the vertical plane represents loudness (in decibels), the horizontal is for frequency. In the digital realm, a parametric EQ looks a bit like the old arcade game Galaga, with the moveable EQ points acting like your cannon. (Luckily, there are no descending aliens.) With us so far?
Q — it’s not just the Star Trek guy
Each of those EQ points is fitted with three controllable parameters: Primary frequency, gain or boost of the frequency, and bandwidth of the frequency, also referred to here as “Q.” We’ll start with the simplest and work our way up.
The primary frequency is, quite simply, the actual frequency you’re affecting. Normally, you’ll find whichever EQ point is closest to the frequency you want to boost or reduce, and then simply move it to the exact spot you’d like for the desired effect. Turning the boost or gain knob up or down determines how much you are boosting (or reducing) your chosen frequency in decibels.
Bandwidth, or Q, is the most technically challenging parameter to understand, but it’s quite simple in practice. (Technically, bandwidth and Q are defined differently in the wider scheme, but for our purposes, they may as well be one and the same.) In the simplest terms, Q (as we’ll refer to it from here out) reflects how wide the swath of the frequency spectrum you’ll be affecting is. A wider Q affects a wider swath of frequencies, a narrower one offers more focused equalization.
When you turn the Q knob, you can see your frequency point swell or shrink. Narrower Q is great for boosting or reducing a very specific frequency — this is what you’d use when trying to eliminate an unwanted resonance, for instance. Conversely, a wider Q affects a greater amount of frequencies — usually as much as 10Hz above and below — making it more like a hatchet, versus a scalpel. That said, the primary frequency is always the most highly affected. Generally, a narrower Q is best for cutting frequencies and a wider Q is better for boosting, but there are no hard-and-fast rules.
Shelf or notch?
In addition (see, we told you it’s involved), some EQ points in a parametric equalizer can be switched from Notch (the default for most control points) to Shelf. Shelf essentially eliminates all frequencies below or above the point you select, sort of like a frequency cliff. As such, Shelf is reserved for the lowest and highest control points on your equalizer.
In practice, Shelf allows you to set a point, say, on the low end of your EQ in which only frequencies higher than that point can pass through it (that’s called a high-pass filter). You can also set a point on the high end in which only frequencies below your selected point can pass through (a low-pass filter). Confusing, right? It may help to just think of it like Gandalf from Lord of the Rings stabbing his staff at the Shelf EQ point. For the high-pass filter, Gandalf stops the bass from getting through: “Bass shall not pass!” For the low-pass filter at the other end, he stops all frequencies above your selected point from getting through: “Treble shall not pass!”
It’s highly involved, but the best way to learn is to simply experiment. The freedom allotted by a parametric EQ is extremely useful in certain situations, letting you customize your equalization and your sound.
Hands-off headphone EQ
Now that your head is likely spinning with the complexities of parametric EQ, we wanted to finally discuss an automagic solution from Sonarworks. Sonarworks’ studio sound-processing engine is already in use in more than 20,000 recording studios, and more recently, the company has branched into headphones.
Like Sonarworks’ studio software, True-Fi — and SoundID, the natural artificial intelligence-powered evolution of the tech — is designed to adjust for any frequency dips and peaks in your headphones’ specific sound signature to create flatter, more linear sound reproduction. Dial your perfect sound in even further with a short series of audio tests that can tune your audio based on your individual hearing ability.
Custom-designed to each pair of headphones, True-Fi is always updating its bank of supported headphones, set up to work with more than 360 different brand-name models at the time of publication. While it’s mostly hands-off, you can adjust the settings to a degree, including bass control and even adjust for your age to account for hearing loss.
We want to stress that we generally still prefer to tailor our own EQ by hand, but we’ve also been thoroughly impressed with True-Fi in practice, and for those looking to simply set it and forget it, this is a viable option for your headphones. Even better, the mobile app is now in early access, and ditto for SoundID, so you can preview the benefits on the world’s most popular tune-playing devices and your favorite pair of headphones.
Targeting your efforts
As promised, we’ve provided a breakdown of the frequency spectrum to help you get your head around which sounds live where. If you’re ever stumped, this guide can help you drill down to the offending (or lean) frequency to help you make a more effective adjustment. Below are guidelines, not steadfast rules, and your own auditory input is what makes this process all the more personal and enjoyable. And that’s the point: Have fun!
Sub-bass: 20Hz to 50Hz
While humans can technically hear down to the depths of this register, most of these frequencies are less cerebral and more gut. Somewhere in the middle of this register is where your subwoofer will make that eerie sound of deep space in sci-fi movies, and these frequencies can add some serious, unearthly power. However, you would very rarely want to add more of this sound, and taking away from here can help give the music more overall clarity.
Bass: 50Hz to 200Hz
The majority of the time, a stalwart hip-hop groove will start at or around 60Hz. The foundational, big-hitting lower register that spouts forth from your subwoofer rests in this domain, including the heavy punch of the kick drum, and even lower tom drums and bass guitar. Moving up toward the 200Hz line begins to affect the very lowest boom of acoustic guitars, piano, vocals, lower brass, and strings. If the music is too darn heavy, or not heavy enough down low, a bit of an adjustment here will help.
Upper bass to lower midrange: 200Hz to 800Hz
Rising above 200Hz starts to deal with the lighter side of the low end. This region is where the meatier body of an instrument hangs out. Adding EQ volume around the middle of this spectrum can add a bit of oomph to richer tones, including the lower end of vocals, deeper notes from synthesizers, low brass and piano, and some of the golden tones from the bottom of an acoustic guitar. Lowering the level a bit here can clear up some space, and open up the sound. Moving to the 800Hz region, you’ll start to affect the body of instruments, lending more weight with addition, or lightening the load with subtraction.
Midrange: 800Hz to 2kHz
This area is a touchy one that can change the sound quickly. Putting on the brakes in this region can take away the brittle sound of instruments. Adding some juice, especially toward the top end, can give things a metallic touch, and can wear down your ears quickly if pushed.
Upper mids: 2kHz to 4kHz
As mentioned above, this register is where your ears aim a lot of their focus. Adding or subtracting here can raise or lower the snap of higher instrumentation quickly. Sounds like the pop of snare, and the brash blare of a trumpet can all be affected here. Adding a little push here can give more clarity to vocal consonances, as well as acoustic and electric guitar and piano.
Presence/sibilance register: 4kHz to 7kHz
This is commonly referred to as the presence zone and includes the highest range of pitches produced by most natural instruments. Boosting the lower end of this scale can make the music sound more forward, as if pushed a little closer to your ears. Backing it off can open the sound and push instruments away for more depth. The upper end of this region is also responsible for the sharp hissing “s” of vocals, known as sibilance. If sharp consonants are popping out at you like the bite of a snake, cutting a few dB from around 5kHz to 7kHz can solve the issue, and save you some pain and suffering.
Brilliance/sparkle register: 7kHz to 12kHz
Raising or decreasing the level at the lower end of this register can help bring some vibrancy and clarity, adding a tighter attack and a more pure sound. If things are a little too sharp or causing some pain after listening for too long, lowering the bottom end of this register can help out quite a bit. Toward the top is where things start to space out into less tangible definition, moving away from what you can hear and more toward what you can feel. That shimmering resonance at the tip of a cymbal crash floats around in the regions of this space.
Open air: 12kHz to 16kHz
Once you get up here, things become more subjective. The bottom registers continue to affect the higher overtones of instrumentation, and synth effects from electronic music can pop around in that region as well. Moving further up, it becomes more about creating a spacier, more open sound. There are very few points in which you’d want to affect the sound much around 14kHz or above — many older listeners won’t be able to even hear these sounds. If you want to boost a bit of space in the belfries of the music, you can add some level here. Too much, however, will make things start to sound synthetic.
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