Clavia nord lead, Owner'S Manual

Page: 83 / 114

About Subtractive Synthesis Page 81
Bandpass filter: This let’s frequencies in a certain range of the spectrum (the band) pass through while
dampening frequencies both below and above this range. This accentuates the mid-range of a sound.
Notch filter:
This filter type (also known as Band Reject) can be seen as the opposite of a band pass filter.
It cuts off frequencies in a “mid-range” band, letting the frequencies below and above through.
In the Nord Lead the Notch filter is combined with a 12 dB Lowpass filter, for greater musical versatility
(see page 44).
Roll-off
Filters of one and the same type (lowpass, highpass etc) can have different characteristics. One of the
factors determining the exact filter curve is the
roll-off , which is measured in dB/Octave (“decibels per
octave”) or poles . The simplest possible filter has a roll-off of 6dB/octave, which is referred to as “1 pole”.
The next step up is 12dB (2 poles), 18db (3 poles) etc.
The most common synth filters are the 12dB and 24dB lowpass filters. The difference between the two
can be studied in the graph below. The 12dB filter let’s more of the high frequency pass through which
gives the sound a brighter and “buzzier” character than the 24dB filter does.
In the Nord Lead, the lowpass filter can be switched between 12 and 24dB modes. For sounds with high
resonance (see below), similar to those in the Roland TB-303, we recommend the 12dB variation. For
most other sounds we recommend 24dB.
Amplitude
Frequency
Fc (Cutoff Frequency)
Amplitude
Frequency
Fc (Cutoff Frequency)
Amplitude
Frequency
Fc (Cutoff Frequency)
12dB (2-pole)
24dB (4-pole)