NORD MODULAR G2 V1.1
12. Synthesis basics: The filter
Page 209
B
B
B
B
A
A
A
AN
N
N
ND
D
D
DP
P
P
PA
A
A
AS
S
S
SS
S
S
S
F
F
F
FIIIIL
L
L
LT
T
T
TE
E
E
ER
R
R
R
This let’s frequencies in a certain range of the spectrum (the band) pass through while dampening fre-
quencies both below and above this range. This accentuates the mid-range of a sound.
N
N
N
N
O
O
O
OT
T
T
TC
C
C
CH
H
H
H
F
F
F
FIIIIL
L
L
LT
T
T
TE
E
E
ER
R
R
R
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.
R
R
R
R
O
O
O
OL
L
L
LL
L
L
L
----
O
O
O
OF
F
F
FF
F
F
F
(
(
(
(
S
S
S
SL
L
L
LO
O
O
OP
P
P
PE
E
E
E
))))
Filters of one and the same type (lowpass, highpass etc.) can have different characteristics. One of the fac-
tors determining the exact filter curve is the
roll-off
, which is measured in
dB/Octave
(“decibels per oc-
tave”) 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.
