While I was learning to engineer audio, it always seemed like a crap-shoot when it came to my EQ moves. There are so many different instruments and they each have their own unique sonic qualities, it wasn't until I had a lot of experience under my belt that I started to see consistencies in the optimal frequency bands for each of the instruments I was mixing.
For example, if you neglect the 1-3k area of a vocal recording, you may find no matter where else you adjust the EQ, the performance just won't stand-out in the mix. For my voice, I usually have too much 1.5k, so it needs to be tamed. All the same, there are sweet spots on every instrument that we can use as a basis for making our EQ moves.
And to back-up even further, knowing these frequencies is key, but knowing what you will be adding or cutting from the instrument is even more critical. Adding 100-250hz to a piano gives it body, but adding 250-1k makes it muddy. If your piano is already muddy, cutting it above 250 will likely fix it, but below 250 you may find you lose a lot of body.
So when it comes to EQ, it is more important to understand the nature of the sound you are looking to boost or cut, than it is the frequencies. Of course after time both of these things become second nature. But it is important to be able to describe the desired impact before we start spouting frequencies. "Wow! The vocal is cutting hard into the mix, perhaps cut __________" is what we are talking about here.
EQ TERMINOLOGY
There are a lot of words used to describe frequencies in the full spectrum. And while some of them may be magic to one instrument, they can be ugly to another. So before we get into the math, here are some terms that are commonly used to describe sounds:
Body - is associated with the low-end of the spectrum and includes sub-lows and lows typically under 200k. Body is considered a value you would typically boost although some instruments can present too much body (Kicks or Bass) that need to be cut or sculpted.
Muddy - frequencies associated with an instrument that are within the low and low-mid end of the spectrum - under 1k - that add little to no quality low-end material. Muddiness is typically cut from the frequency spectrum when it is present.
Boxiness / Basketball Effect - Similar to Muddiness, this effect is typically found in the low-mid band and is usually described as not complimenting the mids, or bass that is unnecessarily creeping into the mids.
Presence / Cuts Mix / Clarity - is purely an upper mid-range frequency term (i.e., above 1khz). For most instruments, presence is additive, you would boost a guitar around 2.5 to get it to cut through the mix, or add 1.5khz to a vocal to give it clarity. This is also an area where too much presence can be easily manufactured. Of all your EQ moves, this is both the most critical and most dangerous one!
Punch / Attack / Slap / Crack - is usually used to describe how percussive instruments or predominantly bass-heavy instruments cut through a mix, like Presence or Clarity, but different. We wouldn't typically say that vocal needs more "crack" or "punch", but these terms are used pretty frequently to describe a snare or kick.
Air / Brightness / Sheen - is used to describe highs usually in the 5k+ end of the spectrum. Giving vocals some "air" brings-out the breathy qualities of the recording. Adding "sheen" to crash cymbals allows you to wash the spectrum with lush high-end that is very noticeable when it appears and disappears.
Harshness - is typically associated with high-mids or highs. Dirty electric guitars with too much 10k+ may sound way too fizzy. Room mics that are not tamed above 8k may have way too much washed-out highs that just don't sound good at all. These are variations of harshness that we try to avoid by cutting either using a shelf or a high-cut filter.
EQ FREQUENCY BANDS
In my guide, I will concentrate on 5 key bands:
0-300Hz - Low Cut Filter
30-250hz - Lows
150-2.5khz - Low-Mids
600-7khz - High-Mids
1.5-16khz - Highs
Each of these bands corresponds with a parametric EQ like an SSL. If your Parametric EQ does not have 4-5 bands, you may need to employ more than one. If the bands do not necessarily line-up with what I have outlined in the EQ Guide, you may need to make some adjustments. Chances are your EQ will line-up for the most part. Otherwise, I recommend using a multi-band EQ like FabFilter Pro Q or Logic's Channel/Linear Phase EQs.
One last thing before we get to the actual EQ moves. I don't discuss Q (i.e., Bandwidth Quality) here for one reason, that's a job for your ears. Q or Quality is the width of the frequency band you are adjusting. Some EQs allow you to adjust the Q or Bandwidth, while others are fixed. On the Logic PulTech (Vintage Tube EQ) some of the frequency bandwidths can be adjusted, same goes for the mid-frequency bands on the SSL. I will however not make any recommendations here with regards to Q because just as the EQ moves we are going to discuss below are very much dependent on the impact of the adjustment, and not necessarily the exact frequency where it occurs, Q cannot be prescribed.
TIP: I setup my Channel/Linear Phase EQs in Logic so they open by default with the following Qs and frequencies already configured. I usually leave the Shelves and Filters turned-off. This just makes my workflow faster so I don't have to reset the default settings that come out of the box.
THE EQ GUIDE
In the link below, I have a 2-page PDF that outlines a number of EQ moves you can make to either boost key frequencies or cut well known, troublesome frequencies from your respective tracks.
Before you get started here are a couple more suggestions to help you in your engineering:
Review the desired impacts before you make any EQ move - If you hear any boxiness in your snare, chances are an adjustment will improve it. But don't boost or cut for the sake of making an EQ move. If the change benefits the instrument, then proceed. But if you find no value in the adjustment, it is perfectly fine to make no change.
Frequencies identified are considered a general range - The exact frequency you choose to boost or cut may be somewhat different from what is described in the EQ Guide, but the general idea is the same. For tight ranges like 50-100hz, you may find 110hz is just right, or 40hz. Either way, if you start in the general area, you will already have a huge head-start.
Go big, then pull it back - I would never prescribe how many dB to boost or cut from a frequency band, that is up to your own ears. But what really helps me is first I will select the approximate frequency band I want to edit, add 10-20dB to it so I can hear the frequency well over all others, and then sweep the applicable frequency range looking for the sweet spot. Once I get there I will pull back to 0dB gain and then boost or cut to taste.
Use Solo for surgery, but make final adjustments in the full mix - Making these adjustments in purely Solo mode will leave you with poor results. You need to make the final adjustments within the full mix, otherwise you run the risk of boosting or cutting too little or too much.
The Crowe EQ Guide - Happy EQ'ing!
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