Waldorf microQ Keyboard User Manual

Contents

Waldorf microQ Keyboard User Manual Manual pdf 71 page image

Sound Parameters – Filter IntroductionWaldorf microQ User´s Manual 72Filter IntroductionOnce the audio signal leaves the mixer, it is sent to the filters. The microQ has two independent filterunits, each with its own individual settings. The signal flow in the filters can be controlled via theRouting function. The filters are components that have significant influence on the microQ’s soundcharacteristics.For a detailed description of the different filter types that are available in the microQ, see the section“Filter Types” on page 78. For now, we’ll explain the basic function of a filter discussing the type usedmost commonly in synthesizers: the low pass filter.The low pass filter type dampens frequencies that lie above a specified cutoff frequency. Frequenciesbelow this threshold are hardly affected. The frequency below the cutoff point is called the pass bandrange, the frequencies above are called the stop band range. The microQ’s filter dampens frequenciesin the stop band with a certain slope. The slope can be 12dB or 24dB per octave. This means that thelevel of a frequency that lies an octave above the cutoff point will be 12dB or 24dB less than thosefrequencies of the signal that fall into the pass band. The following picture shows the basic principleof a low pass filter:FrequencyLevelCutoffPicture 18: Low Pass Filter principleTo give you an idea of the extent of damping, consider this example of a low pass filter: A reductionof 24dB reduces the original level one octave above the cutoff point by approx. 94%. The dampingfactor two octaves above the cutoff point reduces the original level by more than 99%, which in mostcases means this portion of the signal is no longer audible.The microQ’s filter also features a resonance parameter. Resonance in the context of a low, band orhigh pass filter means that a narrow frequency band around the cutoff point is emphasized. Thefollowing picture shows the effect of the resonance parameter on the filter’s frequency curve: