Dynamics control for guitar used to be easy. You put a compressor stompbox like an MXR Dyna Comp in the signal chain, and hit the footswitch for more sustain. Now, plugins provide several flavors of dynamics control, but which is the right tool for the right job?
HEADS AND TAILS
Guitar strings have high peak levels from the pluck attack, and low average levels from the rapid decay. Dynamics processors can affect both the attack and decay.
A limiter is like an engine’s governor—no matter how much signal you put into it (within reason), the limiter clamps signals above a threshold to a specific output level. This has three main uses.
• Control spikes and transients (such as slap bass or heavy picking) that could overload subsequent gain stages.
• Provide an overall louder signal without altering the note’s decay shape. For example, if you set the threshold at -3dB, signals below that won’t be affected, but higher-level signals will be clamped to -3dB. This opens up 3dB of headroom, so now you can amplify the entire signal by 3dB to make it louder without distortion.
• Put an “audio magnifying glass” on your signal, as the lower-level decay signal will be louder.
A compressor is more complex, but mainly lowers high-level signals while raising low-level signals. This keeps peaks under control while providing more sustain. Unlike the limiter, which doesn’t affect the decay’s shape, compression flattens the decay more.
Multiband limiters and compressors separate a signal into several frequency bands (typically four or five), each with its own dynamics section. Because the dynamics control affects only frequency ranges that need it, the effect is more transparent. For example, with a standard limiter, if you hit the low E string really hard, the limiting action will affect other strings, too. A multiband limiter would limit in the frequency range of the low E note, but not the higher strings.
Fig. 1 (above) shows four loudness curves. The black one is an unprocessed E chord. Green adds 3dB of limiting, which reduces the peak. The decay curve level is higher than the unprocessed sound, but has the same shape. The blue curve applies 6dB of limiting. Again, the decay curve tracks the unprocessed signal, but is simply louder. The peak has a much gentler slope.
Fig. 2—The color of each waveform’s solid line corresponds to the curve color in Fig. 1. Note how the compressor resembles the unprocessed waveform, but with a lot more sustain. The signal with 6dB of limiting has a very high average signal level.
The red line shows multi-band compression. The peak doesn’t go down as far, and the level starts evening out to a flatter shape that increases sustain. At around -20dB, the curve tracks the unprocessed curve’s signal, but note that its level remains higher. Fig. 2 relates these loudness curves to waveforms.
THE BOTTOM LINE
Each method provides more sustain, but with different characters. Limiting gives more presence, a bigger sound, and squashes the peaks more so the guitar isn’t as percussive.
Multiband compression retains more of the guitar’s characteristic peak, coupled with more sustain and a flatter decay. You’ll still need to decide what dynamics control to use on a case-by-case basis, but this info should help point you in the right direction.
Craig Anderton has played on or produced more than 20 major label releases, mastered hundreds of tracks, and written dozens of books. Check out some of his latest music at youtube.com/thecraiganderton.