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EQ Fundamentals and the Frequency Spectrum

Updated on May 9, 2017
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Jay Helmus is the author of this article, with exclusive rights and privileges belonging to Florida Guy.

EQ Fundamentals
EQ Fundamentals

We can use EQ to apply it to our vocal and instrument tracks in order to augment their sound. Before we start using EQ, let’s review some situations where using EQ can be useful.

- To make an instrument or vocal brighter and more clear.

- To make an instrument or vocal sound darker.

- To make fit better in the mix.

The concept of the ‘mix’ is extremely important. Have you ever noticed that listening to two vocal parts in a song can sometimes be distracting? Or have you ever noticed that a recording a spoken word vocal is very difficult to hear overtop of music with lyrics in it?

Frequencies Fight!

The reason for this is not necessarily because two people are talking at once (although that is a large contributing factor). Rather, the reason is because two instruments that exist in the same frequency spectrum are operating at once.

For example, the human voice largely operates in the mid frequencies. Therefore in theory, any other instrument that also exists in that frequency range will often ‘fight’ with a vocal and make it difficult for the human ear to differentiate between the two different sounds. This results in an inability to isolate the instruments in the mix, which makes the overall tracknoisier to the brain. In a sense, the two elements in the same frequency range end up ‘fighting’ with each other.

Agreat example of an instrument that fights with vocals are horned instruments like trumpets,french horns, trombones and other brass instruments. Horns exist in much the same frequency spectrum as the human voice, so whenever you have horned instruments in your arrangement, EQ will play an important role to help ‘place’ the two elements in the mix in a such a way so that they do not conflict with each other. There are two main ways to accomplish this:

You can use EQ to boost or cut certain frequencies in either the horns or vocals in order to minimize the extent at which they fight with each other. This will help the human ear better isolate and separate them in the mix, which results in a less noisy and more pleasurable listening experience.

Frequency Spectrum
Frequency Spectrum

Frequency Spectrum Breakdown

For this exercise, refer to the picture below of the frequency spectrum. The location of frequency discussed is on the x-axis. As we discuss each frequency range, try boosting or cutting the frequencies on a song and listen to how it changes. This is important because it helps to train your ear. After all, a nicely trained ear will be your biggest asset throughout your music career!

Sub Bass: 16Hz to 60Hz

These sounds are extreme bass sounds that you might actually feel more than you hear. It’s the booming bass sounds that you can sometimes hear in the pit of your stomach. This frequency range will often include loud bass rumbles, and the booming sound of drums. Increasing too much of these frequencies can cause an instrument to sound muddy and less clear.

Bass: 60Hz to 250Hz

These are the bass sounds that make up the meat of your drums, bass guitars and any other bass rhythmical instruments. Decreasing these frequencies can result in a dramatic ‘thinning’ of the sound, while increasing them too much can create an overly boomy sound.

Low Mids: 250Hz to 2kHz

This frequency range contains many of the sub-harmonic elements of many instruments. Many guitars, keyboards and others can also exist here. It is also where the human voice begins to appear in the frequency spectrum. Increasing these frequencies too much can create a telephone-like sound or possibly a tinny sound.

High Mids: 2k to 4kHz

This area is where the human voice mostly exists on the frequency spectrum, especially with females. Too much of a boost in these frequencies can bring out some piercing qualities to your instruments that may contribute to listener fatigue and sibilance. A slight dip around the 3k range on your instruments accompanied with a slight spike in the 3k range on your vocals can create a nice ‘pocket’ where the vocals can sit nicely in the mix. It can often make the vocals easy to hear in situations where they would otherwise be buried, and comes without too much of a sacrifice in clarity on your instruments.

Music Frequencies
Music Frequencies | Source

Highs: 4k to 6kHz

Much of the human voice and many guitars, keyboards and other instruments will exist here as well as in the previously discussed High-Mids. This area of the frequency spectrum often controls clarity and brightness. Boosting these frequencies around the 5kHz area can bring out the clarity of the instrument or vocal in the mix, and can also make the affected audio sound closer to the listener, while decreasing these frequencies can produce a more distant sound.

Extreme Highs: 6k to 16kHz

This area is all about brilliance, clarity, and brightness on all your instruments. A lot of the crisp sounds that come with your drums can exist here as well. I quite often boost these frequencies to gain a brighter sound, however be careful not to over indulge, for you can run into severe listener fatigue at this range. You can also produce some undesirable sibilance, airiness and piercing sounds that can lead to a very unpleasant listening experience.

Tips and Tricks

1. It’s natural to assume that by boosting certain frequencies, you can enhance the sound of an instrument or vocal considerably. And usually, this is true. But sometimes, it can be just as effective (or more) to cut frequencies instead of augmenting them. This is called subtractive EQ.

When boosting frequencies, it’s possible to gain a slight amount of artifactingcalled “phase shift” that comes from EQ machines. By cutting frequencies instead of augmenting them, you can avoid this side effect completely. It takes quite a lot of practice do this and still retain a high quality and clear mix, but if done properly, subtractive equalization can reach levels of smooth quality that would be otherwise unobtainable.

2. Some microphones can add an unnatural amount of bass frequencies to a vocal or instrument that comes as a by-product of proximity. Depending on the quality of mic, this may or may not be such a bad thing, but if you’re recording multiple instruments with the same mic, these frequencies will start stacking and begin to create a very messy sounding mix. Be mindful of this and reduce these stacking frequencies as needed.

3. If you ever run into problems with two instruments clashing with each other, EQ may be your problem (and answer). The reason they are clashing is likely because the foundation of their sound exists in the same frequency range. You can try cutting or boosting these frequencies to separate the two instruments.

For example, if you have a vocal clashing with a guitar, try a narrow boost in the 2-3k Hz range on the vocal, and then cut those same exact frequencies in the guitar. This may cause one or both to sound awkward when solo’d, but that’s ok. As long as they sound good within the mix, that’s all that matters.

4. Extreme low frequencies in many instruments will sometimes fight with each other, and in truth, don’t add much to the sound anyways because these are some of the frequencies that will be difficult to hear with the human ear. With the exception of bass guitars and drums, if you roll off the low frequencies (anything below 150 Hz), you’ll often find that this cleans up the mix quite dramatically without much sacrifice.

Additional Golden Principles

  • The fewer instruments in your arrangement, the bigger and more powerful each of those instruments will often sound.
  • If it sounds too muddy, try cutting the lows, rather than boosting the highs.
  • If you want things to sound clearer, cut frequencies. If you want them to sound different, boost them.
  • You can’t boost a frequency that wasn’t there in the first place.
  • If you want something to cut through the mix, roll off the bottom. If you want something to blend in, roll off the top.


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