Waldorf Nave - Manual (Page 59)

Sound Synthesis Basics
59 Nave User Manual
widths create peaks or troughs at certain frequencies.
Another special case is a pulse wave with a very narrow
pulse width, in the above picture labelled as <1%. An
infinitely thin pulse creates a spectrum that has all har-
monics with equal magnitudes. In a digital synthesizer,
"infinitely" necessarily means one sample.
The pulse wave is an artificial wave, which means that it
doesn’t occur in nature. It was built into synthesizers
because it can create a lot of different timbres with a
minimum of technical effort. However, certain pulse
widths sound very close to the timbres of acoustic (or
semi-acoustic) instruments, i.e. a guitar or bass guitar, an
e-piano or even a flute.
The most powerful feature of the pulse wave is the ability
to change its width while sounding. This is called pulse
width modulation. When the pulse width is changed, the
waveform starts to sound thicker. This happens because
the effect is very similar to what you hear when you have
two oscillators running with slightly different frequencies.
They interfere and create irregular troughs in the resulting
waveforms.
Filter Introduction
Once the audio signal leaves the oscillator, it is sent to
the filter. The filter is a component that has significant
influence on Nave’s sound characteristics.
For now, we’ll explain the basic function of a filter dis-
cussing the type used most commonly in synthesizers:
the low pass filter
The low pass filter type dampens frequencies 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. Nave’s filter dam-
pens frequencies in the stop band with a certain slope.
The following picture shows the basic principle of a low
pass filter: