Fig 1: Scooped mids (artist’s conception).
Don’t Touch That Dial! No, Do Touch It! No, Wait—Don’t!
Naturally, the players who post those words usually refer to turning down the midrange knob on your amp. This is probably in reaction to sort of mid-scooped rock guitar tones that predominated in the ’80s and into the ’90s. Some engineers refer to this tone profile as a “smile curve,” because if you call it up on a graphic EQ with multiple sliders, the result looks like a grin. (I prefer a less common—but funnier—moniker: “stoner vee.”)
That ’80s sound—strong lows, hyped highs, and super-scooped mids—provides a certain cheap thrill, much like cocaine, the era’s studio drug of choice (or so I’ve been told). The sound can certainly grab your attention, though it isn’t a faithful depiction of a guitar’s innate sonic proportions (see artist’s conception in Fig. 1).
You can modify mids before the guitar signal hits the recording input, or after. We’ll look at precision DAW-based midrange sculpting in a future column. For now, let’s focus on upstream adjustments, especially amp knob settings. But first, a quick-and-dirty review of the relevant EQ lingo.
Frets and Frequencies
The hearing range of a healthy young person is 20 Hz to 20 kHz. The A = 440 Hz we tune to corresponds to the A at the 1st string’s 5th fret. Double or halve the frequency to shift by an octave: 220 Hz corresponds to the A at the 3rd string’s 2nd fret.
Amp tone controls are machetes, not scalpels.
The fundamental of the open 5th string is 110 Hz. The A string on a bass sounds at 55 Hz, as does the lowest note of a 7-string guitar dropped to A. Moving in the opposite direction, the 1st string at the 17th fret rings at 880 Hz. Meanwhile, the lowest frequency emitted by a standard-tuned guitar is E = 82.41 Hz.
Note that the scale isn’t linear: 110 Hz and 220 Hz are only 110 Hz apart, while there’s a 10,000 Hz difference between 10 kHz and 20 kHz. But both 110/220 Hz and 10/20 kHz are exactly one octave apart.
And remember, there’s more to EQ than target frequencies. Equally important is the bandwidth of the slice. Removing a narrow sliver at 500 Hz is a far cry from a broad swath that’s centered at 500 Hz, but which extends by multiple octaves in either direction.
One more thing: Electric guitar amps put out little signal above 4 or 5 kHz, as opposed to, say, pianos or cymbals, whose overtones extend to the top of our hearing range. Boosting or cutting highs above that point does nothing—unless the bandwidth is wide enough to affect frequencies below 4.5 kHz or so.
So what sorts of cuts and boosts do you get when you adjust a typical amp’s mid knob?
Midrange According to Jim and Leo
Let’s turn to a cool bit of free software: Duncan Tone Stack Calculator. (No relation to Seymour D.) It’s for PC only, but Mac users can run it via a Windows shell program such as the $59 Crossover from Codeweavers. It provides visualizations of such common tone controls as those on Fender and Marshall amps, plus that mother of all stoner vee curves, the original Big Muff.
Fig. 2: The tone profile of a typical Marshall amp, with the midrange at 5, 0, and 10.
Fig. 2 shows the frequency curve of a typical Marshall amp with its mid control an noon, fully scooped, and cranked to the max. Lookit! There’s a big-ass scoop at around 800 Hz even when it’s “flat.” Hell, there’s even a scoop when it’s dimed! And when you lower the mids all the way, the distorted discus thrower in Fig. 1 starts to look like an understatement. It’s a wide scoop, too, affecting frequencies from about 100 Hz to 4 kHz — practically the guitar’s entire range.
Fig. 3: The mid cut on a typical blackface-style Fender amp is even more extreme than on a Marshall.
The typical Fender midrange profile in Fig. 3 is centered lower, around 500 Hz. Check out the middle image with its -35 dB cut, which also splashes across the guitar’s entire frequency range. It’s the Marianas Trench of midrange cuts! In fact, if you want to fake an amp sound using a direct-recorded guitar signal, your first needed adjustment is probably a similarly deep and wide EQ cut centered between 500 Hz and 1 kHz, even if you’re aiming for a fat-sounding tone.
Are Scoops for Poops?
So should you avoid scooping mids on your amp? Not necessarily. It depends on the context—duh! Judge with your ears, not the Duncan Tone Stack Calculator. But be mindful that if you nix major mids, it’s not just a bit of EQ nip-and-tuck—you’re disemboweling your tone like it’s a corpse on an autopsy table. Except amp tone controls are machetes, not scalpels.
Fig. 4: Even a humble EQ pedal provides more precise midrange sculpting than most amp EQ knobs.
There’s another way to sculpt midrange upstream from the recording input: using an EQ pedal or similar device. Some of these provide parametric EQ (which means you can specify the bandwidth of the boost or cut). Even a humble Boss GE-7 Graphic Equalizer is surgical compared to amp controls. Here the fixed bandwidth spans about an octave, as opposed to the four octaves or more affected by typical amp midrange pots. (See Fig. 4, with the resulting EQ curve approximated in Logic Pro’s EQ plug-in). Even a maximum -15 dB cut at 800 Hz (roughly the Marshall midrange frequency) is far, far subtler than zeroing an amp’s mid control.
The real precision midrange sculpting is likelier to happen within your DAW—and we’ll explore those techniques in an upcoming column. Till then—it depends on the context!
[Updated 1/13/22]
Photo 1
It’s tough to talk about—let alone teach—EQ techniques, because almost nothing is true 100 percent of the time. Take the common sentiment that the less EQ you use, the better: Yeah, that’s good advice in most cases—adding overstated EQ tends to make tracks sound artificial and/or harsh. But what if “artificial” and “harsh” are the best expressive choice?
What about all those great ’60s guitars mixed with blistering high-end EQ? (Beatles and Byrds spring to mind.) Or parts engineered to sound as small and claustrophobic as possible? (Think Pink Floyd or PJ Harvey.) Or the eerie, not-found-in-nature equalization used by Nine Inch Nails and other noisemakers? There are countless exceptions to the so-called rules.
So instead of dealing in rules, we’ll talk options. We’ll cover some common EQ techniques, and then venture into more radical scenarios. But first, here’s the quickest and dirtiest intro to EQ principles ever. (If you know this stuff already, you might want to bail now and tune in next month, when we get into some interesting case studies.)
Good news for old guitarists with bad ears: You can have severe hearing loss and still perceive the entire frequency range of an electric guitar.
Basic EQ lingo.
To gain a thorough understanding of EQ, Google “equalization” (or “equalisation” if you’re a Brit), the word from which the letters “EQ” are plucked. To gain a superficial understanding that can get you through most situations, read on!
- Equalization means adjusting specific frequencies within a sound—adding or subtracting treble or bass, or emphasizing/deemphasizing specific frequencies in the middle.
- We measure musical frequency—how high-pitched or low-pitched a sound is—in Hertz (Hz). The hearing range of a healthy young person is approximately 20 Hz to 20,000 Hz (20 kHz). If you’re middle-aged, a Motörhead roadie, or both, your upper limit is probably much lower.
- Most musical sounds contain many individual frequencies. The lowest-pitched frequency is called the fundamental. The fundamental of a standard-tuned low E string, for example, is approximately 82 Hz, but there are other frequencies—overtones—that ring out far above the fundamental. If you filter that 82 Hz fundamental from a recording of that low E, the sound gets thin and tinny, but doesn’t vanish.
- If you transpose a note up an octave, the frequency of its fundamental doubles. Drop it an octave, and the frequency is halved. Example: The 440 Hz tone we tune to is the same pitch as the A at the 5th fret of your 1st string. The A at the second fret of the G string is 220 Hz. The open A string is 110 Hz. And a bassist’s open A is 55 Hz, below the guitar’s range. The fundamental of your high E string at the 17th fret is 880 Hz.
- Good news for old guitarists with bad ears: The frequency range of an amplified electric guitar extends from somewhere around 80 (depending on how you tune your low string) to somewhere around 4.5 kHz—typical guitar speakers simply don’t transmit higher frequencies. You can have severe hearing loss and still perceive the entire frequency range of an electric guitar. The range of an acoustic guitar extends much higher, however.
- Loudness (or amplitude, to use the more science-y term) is measured in decibels (dB). Gently rustling leaves might measure 20 dB, while a jet takeoff can reach 150 dB. The threshold of pain is approximately 130 dB. The loudest rock concerts on record exceed it. In mixing, most EQ adjustments are of only several dB, though they sometimes reach ±20 dB or more.
- Bandwidth refers to the breadth or narrowness of the affected frequency range. Most guitar and amp tone controls have relatively wide bandwidths. Narrow bandwidths are sometimes called notches. Bandwidth is also called “Q.”
- Filtering is the process of removing particular frequencies. A low-pass filter (LPF) cuts highs, letting lows pass through for a darker sound. A high-pass filter (HPF) does the opposite, cutting lows. A band-pass filter affects a particular “slice” of frequencies. The width of the slice varies according to the filter’s—wait for it—bandwidth.
- An EQ tool that lets you select the target frequency and its bandwidth is said to be parametric. If you can select the frequency, but not the bandwidth (as on many active bass guitar tone controls), we call it quasi-parametric.
Take the EQuiz!
After reading the above, do real-life EQ utterances like these make sense?
“My guitar sounds a little dark—can you give me +2 dB at 2.5k?”
“Yow! I get howling feedback when I step near the monitor. Can you notch out a little 1k?”
“The bass player just went into anaphylactic shock! If I drop my low E to A, and you pump up that 50 Hz, maybe no one will notice.”
Cool. Now you can talk EQ like a pro.
EQ in your tone chain.
Where do the EQ stages in your guitar’s tone chain fit into the picture? Standard guitar tone controls are low-pass filters. Same with most distortion pedals that have a single tone control. The nature of amp tone controls varies from model to model, but a high-pass bass control, a low-pass treble control, and a band-pass mid control is a typical arrangement. Many electric basses employ quasi-parametric midrange controls, with separate boost/cut and frequency-select controls.
In other words, the EQ controls on guitars, effects, and amps are wide-bandwidth filters that produce broad effects. In the recording/mixing realm, the tools tend to be more subtle and complex. If your guitar’s tone knobs are butcher knives, studio EQ tools are scalpels.
Let’s sharpen our scalpels.
A typical EQ plug-in.
The recording guitarist can choose from a vast array of hardware and software equalizers. But for all their variation, most provide the same basic functionality. I use the EQ plug-in from Apple’s Logic Pro as my example here (Photo 1), but you’ll find similar features on many equalizers.
This particular plug-in is an 8-band EQ, which means it offers eight independently adjustable filters, though you seldom need that many. Note the three rows of numbers below each color-coded band. The top one is the active frequency in Hz. The middle is the amount of boost or cut in dB. And the lowest number represents bandwidth.
Let’s check out the effect they have on the sound of a distorted guitar track. Ex. 1 has no EQ — it’s the sound from the amp as heard by the mic.
In Ex. 2, I’ve activated the leftmost band, a high-pass filter that chops everything below a specific frequency.
Photo 2
Here, set to 150 Hz (Photo 2), it thins out the sound in a big way.
Photo 3
The rightmost band is a low-pass filter that works the opposite way. Set to cut everything above 1.1 kHz (Photo 3), it makes the guitar sound dark and dull.
Recording Guitarist: ABCs of EQ -- Audio 3 by premierguitar
Listen to Recording Guitarist: ABCs of EQ -- Audio 3 by premierguitar #np on #SoundCloudBands 2 and 7 are shelving filters. They too affect everything above or below a particular frequency, but they can boost levels as well as cut them.
Photo 4
Cranking the lows as in Photo 4 creates a rumbling, bottom-heavy sound.
Photo 5
A high-shelving filter (Photo 5) is often used to broadly brighten a guitar track.
Photo 6
The middle four bands are the most powerful. These fully parametric EQ bands can cut or boost any audible frequency at any bandwidth. Set to a narrow bandwidth (Photo 6), they can add a honking, wah-like resonance.
Photo 7
Set to a wider bandwidth (Photo 7), it brightens a much larger swath of sound.
Photo 8
Finally, I’ve combined multiple EQ bands for a fairly typical crunch-guitar EQ adjustment (Photo 8).
Recording Guitarist: ABCs of EQ -- Audio 8 by premierguitar
Listen to Recording Guitarist: ABCs of EQ -- Audio 8 by premierguitar #np on #SoundCloudWhich sounds best?
Heard in isolation, probably the first example, with no EQ. But guitar tracks seldom exist in isolation. The “right” setting always depends on the context. And that’s where we’ll pick up the thread next month, when we look at real-life EQ adjustments in real-life studio contexts.
[Updated 1/11/22]