Filter - Waldorf MicroWave XT Bedienungsanleitung

Filter

Once the audio signal leaves the mixer, it is sent to the filters. The MicroWave II/XT/XTk has
two independent filter units, each with its own individual settings. Both filters are routed in
series. The filters are components that have significant influence on the MicroWave
II/XT/XTk's sound characteristics.
The filter type most commonly used in synthesizers is a low pass filter. This 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 MicroWave II/XT/XTk's filter
dampens frequencies in the stop band with a certain slope. The slope is selectable between
12dB and 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 diagram shows the basic principle of a low pass filter:
Level
To give you an idea of the extent of damping, consider this: A reduction of 24dB reduces
the original level by approx. 94%. The damping factor two octaves above the cutoff point
reduces the original level by more than 99%, which in most cases means this portion of the
signal is no longer audible.
The MicroWave II/XT/XTk's filter also features a resonance parameter. Resonance in this
context means that a narrow frequency band around the cutoff point is emphasised. The
following diagram shows the effect of the resonance parameter on the filter's frequency
curve:
If the resonance is raised to a great extent, then the filter will begin self-oscillation, i.e. the
filter generates an audible sine wave even when it does not receive an incoming signal.
User's Manual MicroWave II • MicroWave XT • XTk
Level
Resonance
24dB/Oct
Cutoff
Cutoff Frequency
12dB/Oct
Frequency
51