Appendix
198
Iridium Manual
A Short Introduction to Granular Synthesis
Granular synthesis is based on a simple idea: instead of
playing back an entire sample, only short portions of the
sample – the so-called grains – are played. These grains
can be played back in any order. Each time a grain ends, a
new one starts. To avoid discontinuities in the playback,
and to minimize artefacts, envelopes are applied to the
grains. Granular synthesis can be used to extract interes-
ting spectra from all kinds of samples creating sound
effects by completely scrambling a sample, or for low-
fidelity time stretching, for example.
Very short grains produce sounds with an individual pitch.
For that reason you can also use samples without a distinct
pitch – such as drum loops and sound effects – to extract
pitched spectra from them. Sounds with longer grains
usually play back with the pitch of the original sample.
If you play back the same portion of a sample over and
over again, the sound may become too static. You can use
the Particle Generator parameters to compensate for this
and bring more liveliness into the sound. By adding more
grain streams (kernels) the grain and sound density can be
increased to produce a richer sound.
Filter Introduction
Once the oscillator signal leaves the mixer it is sent to the
filters (Dual Filters and Digital Former). The Iridium offers
two filter units, each with its own individual settings. The
signal flow in the filters can be controlled via the Routing
function on the Filter page. The filters are components that
have significant influence on the Iridium’s sound charac-
teristics.
Now,we’ll explain the basic function of a filter discussing
the type used most commonly in synthesizers: the lowpass
filter.
The lowpass filter type dampens frequencies that lie above
a specified cutoff frequency. Frequencies below this
threshold are hardly affected. The frequency below the
cutoff point is called the pass band range; the frequencies
above are called the stop band range. The Iridium’s filter
dampens frequencies in the stop band with a certain slope.
The slope can be 12dB or 24dB per octave. This means that
the level of a frequency that lies an octave above the cutoff
point will be 12dB or 24dB less than those frequencies of
the signal that fall into the pass band. The following image
illustrates the basic principle of a low pass filter:
