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What Is an Equalizer?
An equalizer (also called an “EQ”) is an audio filter that isolates certain frequencies and either boosts them, lowers them, or leaves them unchanged. Equalizers are found on a wide array of electronic devices. These include:
- Home stereo systems
- Car stereo systems
- Via digital software on computers, cell phones, and tablets
- Instrumental amplifiers (guitar, bass, keyboard, etc.)
- Guitar pedals or rack effects
- Studio mixing boards
An equalizer will alter the color of an audio signal. It could make vocals more articulate by boosting the treble frequency range. It could make a song sound “heavier” by boosting bass frequencies. Sometimes, it can be used to remove certain sounds from a recording, like the high pitched buzz of a fluorescent lighting fixture.
What Does an Equalizer Do?
An equalizer will adjust audio output so that certain frequencies are emphasized over others. Most do this through the use of linear filters. How those filters function varies based on the equalizer’s interface.
Here are some popular types of equalizers:
- Parametric equalizer or parametric EQ. This has three controls. The first determines what specific frequencies you want to boost or cut: you zero in on a frequency somewhere between 20 Hz and 20,000 Hz, which you can then boost or decrease. The second, which is sometimes called the Q, determines the sharpness of the bandwidth (meaning “are you zeroing in tightly on one specific frequency, or are you targeting a wider bandwidth surrounding that frequency?”). And the third is the level control—by how much do you want to boost or reduce a frequency? Parametric EQs usually exist in the form of digital software.
- Graphic equalizer or graphic EQ. This is found across a wider range of devices—home sound systems, personal stereos, amps, pedals, mixing boards—but it’s not as precise as a parametric EQ. In a graphic EQ, the audio spectrum is divided up for you, and each band is assigned a specific fader or knob. You can then go through each fader/knob, and boost it, lower it, or leave it alone. Some graphic EQs only have three bands, usually labeled “treble,” “mid,” and “bass.” Some graphic EQs have five bands—this is popular on home stereos. Some graphic EQs have upwards of 30 frequency bands.
- High-pass filters and low-pass filters. These are very simple, and they do what the name implies. A high-pass filter (sometimes referred to as “hi-pass filter”) allows high frequencies to pass through unencumbered while blocking out low frequencies. A low-pass filter does the opposite: low frequencies pass through while high frequencies are blocked.
How to Use an Equalizer: Tips From Timbaland
Since the early 1990s, Timbaland has been one of popular music’s most successful producers. He’s helmed the mixing board for Missy Elliott, Aaliyah, Justin Timberlake, Madonna, Nelly Furtado, Jay-Z, and Beyoncé, and he’s also stretched his boundaries to work with artists like Chris Cornell, Bjork, and Brad Paisley.
He recommends using these five EQ settings to help yourself process what frequencies are associated with what types of sounds:
- Super Low (approximately 20 Hz to 60 Hz). These frequencies are the lowest audible sounds humans can hear. In club music, you’d hear this via a bass, sub-bass, or low-pitched drums. Boosting these frequencies can shake a room or a car and they can be heard from far away. That can be a cool effect, but too much boosting will make your mix muddy and undefined. It’s hard for our ears to pick out individual notes in super low frequencies, so use this region with caution. On an amplifier or speaker system, these frequencies would be heard via a subwoofer.
- Lower Mids (app. 60 Hz to 250 Hz). These frequencies are resonant and pleasing to the human ear. A lot of producers (including Timbaland) boost the lower mids on drums to make them “pop” a bit more. Melodic instruments that fit this range include cello, bassoon, baritone and tenor saxophones, trombone, and the low notes of a guitar. On an amplifier, these frequencies would be controlled with the bass knob.
- Mids (app. 250 Hz to 1500 Hz). These are the frequencies that humans hear the most clearly. As a result, boosting the mids can almost have the same effect as simply boosting the overall volume. If you want a particular instrument to cut through a mix, boost the mids. But be aware that too much mid-boosting will tire the ear and overwhelm the listener. On an amplifier, these frequencies would be controlled with the middle or mid knob.
- Upper Mids (app. 1500 Hz to 6600 Hz). Upper mids should be boosted sparingly because this is the frequency that can be most damaging to the human ear. When boosted correctly, the upper mids will produce a chime-y, bell-like sound. The upper mids are also the frequency that sounds most like distortion. This can be a great effect for intense, fuzzed-out keyboards or guitars. On an amplifier, these frequencies would be controlled with the treble knob.
- Super High (app. 6600 Hz to 20,000 Hz). These frequencies are among the highest that the human ear can perceive. They range from stinging and annoying (in the lower part of this range) to ambient and atmospheric, as though you’re hearing background wind or surf (on the upper end of this range). A lot of producers will dip the upper mids so that nothing sounds too piercing, but they’ll boost the super high frequencies to create atmosphere. On an amplifier, these frequencies would be controlled with the presence knob.
Best EQ Settings for Drums
When it comes to drums, it’s important to boost the lower-mid frequencies of kick drum samples and mostly leave snare drum samples alone. The kick provides energy and the snare provides texture.
If you want to bring out certain parts of the drum kit, consider these frequencies:
- 50-100 Hz boosts the kick drum
- 500-3,000 Hz will boost your snare, depending on what model you’re using
- Cutting mid-range (while leaving your highs and lows relatively boosted) will help bring out your toms. (This is known as a “V curve” because of how it looks on a graphic equalizer.)
- Experiment with the ultra-high end on cymbals. Those frequencies give them their “sparkle” but a little can go a long way
Best EQ Settings for Guitar
Guitar EQ varies quite a bit depending on genre and whether you’re playing rhythm or lead.
- Boosting around 150 Hz will add heaviness to your guitar tone
- Depending on your guitar, pedal, and amp combo, you can get an annoying “honk” in the 1,000-2,000 Hz range. Lower these frequencies to smooth out your tone
- Boosting the guitar around 3,000 Hz will help it cut through the mix, especially on lead lines
- Boosting treble frequencies can create a distortion effect. In fact, some of the earliest electric guitar distortion came from treble boosters. To this day, Queen’s Brian May gets his sound by running a treble booster into a cranked Vox AC30 amplifier
Learn more about music production with Timbaland here.