Just as multiband compression gives more precise control over how to apply compression to different frequency bands, multiband distortion does the same thing for distortion. Splitting a signal into different bands, and distorting each band individually, minimizes some of the intermodulation distortion that occurs from the interaction between high and low frequencies as they’re distorted. The result is a “smoother,” more controllable sound that’s very relevant to keyboards because of their wide frequency range.
HOW IT WORKS
The first step is to split the incoming signal into multiple frequency bands (typically three or four). These usually have variable crossover points, so each band can cover a variable frequency range. This is particularly important with drums, so the low band can zero in on the kick and distort it a bit, while leaving higher frequencies (cymbals etc.) untouched.
After distorting each band, it’s common for each to have a volume control so you can adjust the relative levels. For example, you might want to pull back on the highs a bit to avoid “screech,” or boost the upper midrange so the instrument being processed “speaks” a little better.
TAKING OUT THE TRASH
iZotope Trash lets you create up to four bands (see Figure 1), and for each band, choose a distortion algorithm, compressor, pre- and post-distortion filtering, “cabinet” model, and “buzz” — sort of a lo-fi processor with options like tape, digital, lo-fi digital, and so on. So you could, for example, create a really bright sound for the lowest band with lots of harmonics, dull the highest band to keep it from getting too bright, and add a midrange peak (or two) to bring out definition. Other per-stage controls include input gain, overdrive, mix, and output gain. Also note there are lots of additional presets on the iZotope website, both from the company and users.
ROLL YOUR OWN TRASH
While Trash is a highly-desirable plug-in, you can also create multiband distortion in a DAW. The basic idea is to use EQ to isolate different frequency bands, and follow each EQ with distortion.
To create the different bands, you can copy the same track to create multiple tracks and insert effects into each track, or send one track to several buses, insert the effects into the buses, and sum the buses into the master output.
Figure 2 shows how the response curves of three Sonitus EQs are set to create three different frequency bands for the source signal: A lowpass response provides the low band, a highpass the high band, and to cover the middle, a combined highpass and lowpass response (where the lowpass frequency is higher than the highpass frequency) creates a bandpass response.
Of course, one of the coolest aspects of this approach is you can “weight” the crossover points to change the response, as well as pan each track to a different location in the stereo field. So, check out multiband distortion for yourself — you may never go back to the normal kind.
REAL-WORLD EXAMPLES
The first multiband distortion was the Quadrafuzz, a hardware do-it-yourself project I designed that debuted in Guitar Player magazine. It became a kit for PAIA Electronics (www.paia.com) and the schematic is also in the book Do It Yourself Projects for Guitarists (BackBeat Books). Later on, Steinberg virtualized it as a plug-in that eventually ended up being bundled with Cubase SX. (Although it’s not included with Cubase 4, if you have Cubase SX, you can simply copy the Quadrafuzz DLL into your VSTplugins folder and it will work.) Currently, iZotope’s “Trash” is the most versatile multiband distortion plug-in available, and is the subject of our article. Other options include MDA’s Bandisto, and Ohm Force’s excellent Predatohm.
Fig. 1. iZotope’s Trash is a feast for distortion fans, particularly because of how it handles multiband distortion.
Fig. 2. Three EQs are set up on different tracks in order to restrict those tracks to specific frequency ranges.