Properly miked, a quality well-tuned acoustic guitar with new strings should need little equalization. Perhaps to add some frequencies for sheen, or maybe to pull where the sound may mask other instruments.
When equalizing something with as many overtones as an acoustic guitar, pull the un-harmonic overtones and enhance the pleasing harmonics. This is when the musical recording engineer has the advantage. As a starting point, maybe:
– Roll off below around 82 Hz. The lowest note on the standard acoustic guitar is E, around 82 Hz.
– Sweep the low midrange, from 80 Hz to 300 Hz to find the boomy sound, then pull it using a narrow Q setting.
– Add somewhere between 80 Hz and 350 Hz for body, but only if there is room. Holding down the bottom end is normally not the acoustic guitar’s job.
– Add 300 Hz to 1 kHz for early harmonics.
– Add somewhere from 700 Hz to 1.2 kHz for more “wood” or pull here to ease the secondary harmonics.
– Add 1.5 to 3 kHz for presence. Pull for hollowness.
– Add 3 to 5 kHz for presence and attack.
– Add around 10 to 12 kHz for sparkle. It doesn’t take much to go from sparkle to brittle. Adding highs means adding noise.
The characteristics of an acoustic guitar might include wide dynamic range, semi-fast rich initial transients and substantial sustain. The acoustic may not have as many peaks as a snare drum unless the part is percussive, but it has peaks none the less. Closer miked sounds may need more compression than microphones placed a few feet away. Try:
– Attack. 10 to 20 ms. A very fast attack can control the initial attack transients of a sound.
– Release. Medium. Start at 250 ms and raise or lower as needed, depending on the tempo of the song.
– Threshold. Medium to high. A high threshold allows all the natural sounds and dynamics of the guitar to remain intact. A lower threshold might bring out more lower body.
– Ratio. Low, to begin with, maybe 2:1 or 3:1 dB of gain reduction. A higher compression ratio may be needed as a player may tend to move off axis now and again. Play with the ratio until the quiet bits as well as the loud bits can be heard. A higher ratio can increase the sounds density, so it fits in with other compressed tracks.
Choose to use two. If you choose to use two microphones on an acoustic instrument, often the one with more lows – usually the closest microphone – may need more compression than the distant one.
De-ess the guitar. Minimize fret squeaks and noise with a de-esser.
Defeat the proximity effect. Pull low end that may be created by proximity effect before sending the signal into the compressor or risk having the compressor react to the added lows, rather than the program.
Sympathy for the level. When the acoustic instrument is not in use, put it away, or loud levels in the room will cause it to ring out sympathetically.
Tim Crich has over 20 years of experience in the recording studio and has worked on records by the Rolling Stones, Bob Dylan, John Lennon, KISS, Billy Joel, U2, David Bowie, Bon Jovi, Ozzy Osbourne, Cher, Byan Adams and many more. He has engineered for some of the biggest producers in the world. This article is excerpted with permission from his book Recording Tips For Engineers.