Digital mixers use parametric equalizers - which is a god-send for those who are used to a graphic equalizer with an analog system. Parametric EQ allows for so much more flexibility.

Considering it is one of the most popular digital mixers in churches today, I will use the Behringer X32 for all visuals in this post. However, the principles will translate to most digital mixers.

Parametric EQ Types

There are several different types (or modes) of EQ available with a parametric equalizer:

• High & Low Cut Filters allow you to completely cut the frequencies above or below a specific threshold. The low cut filter is most useful on vocals as you can cut out all the unnecessary low frequencies that cause popping, feedback and muddiness.
• Shelving Filters allow you to boost or cut all frequencies over or under a specific threshold. This is similar to high & low cut filters except you have the freedom of choosing how much to cut or boost the frequencies (instead of cutting them out completely).
• Peaking Filters (PEQ) allow you to target specific frequency bands to cut or boost. Although shelving filters have their place, peaking filters will generally be the best option when solving a frequency problem.

1. Low cut filter
2. Peaking filter (PEQ)
3. Peaking filter (PEQ)
4. High shelving filter

Gain, Frequency & Q

The ‘gain' and ‘frequency’ knobs are exactly what you would expect them to be. Gain controls how much you cut or boost the frequency while the frequency knob allows you to choose which frequency to target.

The ‘Q’ is a bit more mysterious. It is only available when using peaking filters (PEQ) and allows you to set the bandwidth of frequencies to be affected. The lower the Q value, the more frequencies are affected. On the other hand, higher Q values affect fewer frequencies.

1. Low Q value (1) = wider range of frequencies affected
2. High Q value (7.1) = narrow range of frequencies affected

Finding the Right Q Value

Prior to digital mixing, 31-band graphic equalizers were the best way to dial in your sound. To help give some perspective, a Q value of 4.3 will give you the same result of adjusting one of the knobs on a 31-band graphic EQ.

Therefore, in most cases, I find it best to start with the Q value at 4. This starts the process at a place most people are familiar with, especially if you transitioned from analog to digital mixing. Then, the goal is to find the most narrow bandwidth (higher Q value) that achieves the desired result. After all, there is no reason to cut out neighboring frequencies if you don’t have to.

A Few Examples

Keep in mind, there is no one-size-fits-all approach to frequency problems. All I can give you is a starting point and then you have to dial it in from there.

Fixing Feedback Problems

Let’s say you have a feedback problem on one of your vocal mics and find that the problem is at 600Hz. The fix here is a peaking filter (PEQ) starting with the following settings:

• Q: 8
• Frequency: 600Hz
• Gain: -6dB

You may need to cut more (lower gain) to get rid of the feedback problem or you may need a wider frequency band (lower Q value) to get the job done. The goal is to find the most narrow bandwidth (highest Q value) along with the least amount of gain cut that still solves the problem.

Cutting Lows out of Vocals

Every vocal mic should have a low cut filter. When using a low cut filter, you do not have to worry about the Q value or gain - the frequency placement is the only option available. I recommend starting at 100Hz and increasing until the vocal sounds too thin. Then, dial it back a bit.

Currently, I have the low cut filter set around 220Hz on vocals at our church. Our room reverberates terribly around 250Hz, so this cleans up the muddiness without making them sound too thin. Keep in mind, your situation is probably different, so like I said above, start at 100Hz and go from there.

Getting Rid of Annoying Frequencies

There are times when you need to bring a vocal or instrument up in the mix but when you do, it is irritating to the ear. Then, you bring it down and it gets lost. This is the sign of a frequency problem.

To fix it, use a peaking filter (PEQ), start with your Q value at 4 and set your gain to +6dB. Then, sweep through the frequency spectrum slowly until you find the irritating frequency range. Then, cut the gain to about -3dB. If this fixes the problem, awesome! However, you will most likely need to dial it in even more, experimenting with the Q and gain values.

How to Become an EQ Genius

Trial and error is the best way to get good at EQ. The purpose of this post is to help form a foundation, and now it’s your turn to build the house. Don’t be afraid - dive in and try some things. At first, most of them won’t work and you will get frustrated. But, keep at it. Eventually you will get to a point where you can hear the problematic frequency range before you even go searching for it.