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Chapter 11 Special 151
The simplest application of the SubBass plug-in is as an octave divider, similar to
“Octaver” effects pedals for electric bass guitar. A simple frequency division circuit in
such pedals requires a monophonic input sound source, with a clearly defined pitch.
This type of device is only capable of producing an output signal which is one or two
octaves lower than the input signal. An octave is a frequency division by two. A ratio of
four means two octaves, and a ratio of eight equals three octaves.
As opposed to a pitch shifter, the waveform of the signal synthesized by the SubBass
plug-in has nothing to do with the waveform of the input signal. It’s shape is
sinusoidal—but a pure sine wave is rarely achievable in complex arrangements. It is
mixed together with the original signal. The mix ratio is defined by the Mix parameter.
SubBass creates two bass signals, derived from two freely definable portions of the
incoming audio signal. Therefore, you are not limited to monophonic signals with a
defined pitch, but complex summed signals may be processed as well. Center High and
Center Low define the center frequency of the band that the transposed signal will be
derived from. Bandwidth sets the bandwidth of the frequency band.
Within these frequency bands, the filtered signal should have a reasonably stable pitch,
in order to be analyzed correctly. The graphic shows the frequency bands of a typical
boom box, which transposes two frequency bands, with the width of a fifth, by one
octave each. If you set the analyzed frequencies a little higher, the SubBass plug-in
plays these frequencies, much like a bass guitar player doubling the lower notes of a
guitar player.
In real life, narrow bandwidths lead to the best results as they avoid unwanted
intermodulations. Set Center High a fifth higher than Center Low, which means a factor
of 1.5 for the Center Frequency. Derive the sub-bass to be synthesized from the existing
bass portion of the signal, and transpose by only one octave in both bands (Ratio = 2).
Do not overdrive the process, or you will introduce distortion. If you recognize
frequency gaps, move the Center Frequencies, or widen the Bandwidth a little.
Be prudent when using the SubBass plug-in, and compare the extreme low frequency
content of your mixes with other productions.