Using Equalizers

Equalizers

What are the advantages of using E.Q.? Sound travels in three-dimensional waves or vibrations. Our ears can detect these vibrations and they interpret them as sounds. The amount of waves or vibrating air that hit our ears in one second is called frequency. Frequency is measured in Hertz abbreviated Hz. Our ears can hear anywhere from 20 hertz to 20,000 hertz aka 20 kHz a second. The frequency determines the pitch of a note. The lower the amount of hertz per second, the lower the pitch of the note. The higher the number of Hertz per second, the higher the note. The range that the human ear can hear is called the frequency spectrum. This is also known as the audio spectrum.

Frequencies determine note values. A note that vibrates 440 times a second is an A note. When this A note is played on a guitar or a piano a fundamental frequency is generated at 440 times a second. There are other frequencies generated as well that make up the character of the sound. These frequencies are called harmonics. All of these frequencies combine together to produce the note we hear.

Equalization shapes the sound of audio by changing the level of specific areas in the frequency spectrum. These changes in the frequency spectrum are made by using filters. Each filter within an EQ is called a band. An EQ is a collection of filters or bands which either boosts or cuts the audio at different frequencies along the spectrum. EQs can be a single band (one Filter) or a multiband (multiple filters). There are two main concepts for using EQ, Corrective and Creative.

Filters are used to emphasize or suppress frequencies in an audio signal. The end result is a change in the tonal color of the audio. There are many different kinds of filters. EQs are generally used for tonal equalization. Filters, when used outside of EQs, are generally thought of as cut only devices that are used to remove some portion of the audio spectrum.

One of the defining characteristics of filters outside of EQs is their ability to generate harmonic resonance in the frequency region close to the cutoff area. It will boost a part of the frequency spectrum right at the point where it removes the rest of the spectrum. This boosting causes the frequency to oscillate and generates resonance. These filters are used to color the sound rather than equalize it. These types of filters are generally found in Synthesizers.

EQs are specialized filters that allow certain frequencies to pass through unchanged while boosting or cutting the level of other frequencies. EQ changes the phase of the affected frequencies that are being changed relative to the frequencies that are not being boosted or cut. This is why making a sound brighter can make it seem closer in the mix while taking off some of the high end can make it seem more distant.

Use as little EQ as possible to correct a problem. Use subtractive EQ, cut when possible before boosting to correct problems in the mix. The human ear will be more tolerant of EQ cutting rather than boosting. EQ actually begins with the recording of an audio track. Microphone placement, microphone choice, and the equipment that the signal runs through all have an impact on the tonal shape of the recorded audio. You want to get the best sound possible while recording individual tracks. Never think that you will fix bad mic placement or harsh tone in the mix. Fix it before you record the track. This is so you will have minimal corrective equalizing to do in the mix. This approach will give you better results and it will make the music you record sound better.

EQ can also be used creatively to provide some separation of two similar sounds within a mix that are sonically fighting each other for attention and muddying up an area of the frequency spectrum. An example of this can be found in the bass drum and the bass guitar, or the snare drum and the shaker. These are examples of two similar sounds within a mix that sit close to each other in the frequency spectrum. EQ’s used creatively can help provide separation so you can identify each instrument in the mix.

Audio waves are cyclical. They proceed through regular cycles of repetitions. Phase refers to how far along a given cycle the waveform is. EQ will change the phase within a given signal. As I said earlier, EQ begins with the recording environment. The Room acoustics, Microphone choice, Microphone placement, and the proximity effect all have an impact on the tonal color and EQ of the sound being recorded. When EQ is applied it will affect the phase of the signal.

We use equalization in the mix to address some of the following issues

1. Some tracks might jump out at certain frequencies. EQ would be used to highlight those frequencies to either cut or boost those frequencies.
2. A well-balanced mix is one where no specific area of the frequency spectrum is taking up too much headroom or available energy. EQ may be needed to make this happen
3. The combination of tracks and the way they interact with each other can cause areas of the frequency spectrum to build up. EQ may be needed to distribute a broader area of a region
4. EQ may be needed if tracks are not blending well together in a mix. One strategy would be to cut some of the main frequency range areas of the problematic instruments rather than boosting other areas.

These are my top 20 things to be aware of when using EQ

1. Boosting EQ will boost noise too.
2. Deep and narrow EQ boosts sound more obvious and unnatural then deep and narrow cuts.
3. EQ boosts sound more natural over a wider frequency range with just a couple of DB gain.
4. Before boosting a certain area try cutting the frequencies you feel are overpowering the area you want to boost.
5. Sounds will sit better in the mix by using low and high pass filters. This will remove low or high end from the signal in an area that the signal does not occupy. For example, using a high pass filter on a bass instrument will help the bass sit well in the mix. Using a low pass filter on a guitar will help it to sit better in the mix.
6. If you add a lot of EQ boost you run the risk of clipping your signal. This will add unwanted distortion to your sound and ruin your headroom. If you need to significantly boost your signal make sure to reduce the volume level in the mix. If you boost try reducing the output volume of the EQ.
7. The effect of cutting the low frequencies will often make the high frequencies seem brighter. This goes back to the cutting before boosting rule.
8. Changing the EQ will change the level of the instrument in the mix. You may need to readjust the level of the instrument once you have applied EQ.
9. Don’t EQ in solo mode only. Check the way the instrument sounds in the general mix before you move on.
10. Human hearing is not flat. Our ears are more sensitive to the midrange frequencies. Extreme lows and highs in the frequency spectrum are harder for our ears to pick up.
11. For this reason, a Smile shaped EQ curve will promote the illusion of loudness and power. This is done by boosting the low and high ends of the frequency spectrum.
12. In most cases, high and low pass filters have steeper slopes than regular EQ bands.
13. Cut the low end off of instruments that are not meant to be bass instruments. This will open up more headroom.
14. The bypass button is your friend. Do A/B comparisons while applying EQ to your signal. It is easy to lose perspective as you make your adjustments.
15. Use EQ to separate two similar sounds in a mix. The amount of overlap in a given area can make them sound muddy and the ear will struggle to separate the two sounds.
16. The contrast between instruments is a good thing.
17. First, cut then boost.
18. Less is more.
19. Take breaks to give your ears a rest.
20. Check the harmonics of problem frequencies.