Fig 1: Scooped mids (artist’s conception).
“Don’t scoop your mids!”
It’s probably the most frequently dispensed pearl of tone wisdom on guitar forums—and one of the most vague. Midrange is a broad topic, literally and conceptually, and those words can signify many things. So let’s unpack the meanings of midrange in search of deeper understanding of how amp midrange settings affect your recorded tones.
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.
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.
(Sneaky soundcheck trick: If the P.A. feeds back, locate the corresponding pitch on your guitar neck and round if off to the nearest A. Then you can say intelligent-sounding things like, “Whoa! You might want to dial back that 1.5k!”)
Every guitar note has many overtones ringing out above its fundamental (the lowest frequency of a musical sound, and the one we refer to when tuning). So when you lower the EQ at, say 500 Hz, you’re not just dialing back notes around the seventh and eighth fret of the first string—you’re decapitating those frequencies from any notes whose overtones fall into that register, including those from your guitar’s lowest pitches. It’s far from surgical—unless by “surgical,” you mean scraping out all the guts and dumping them on the floor.
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?