SIGMA EQ Station - Manual (Page 18)

16
GRAPHICAL EQ TYPES IN THE EQ STATION
Hybrid parallel/cascade structure
A compromise between the pure parallel and the pure
cascade structure is possible too. By implementing the
even-numbered bands in one parallel-type EQ and the
odd-numbered bands in another and then connect the two
in cascade, we get the cascade-structure type of gain
build-up between adjacent bands, and other bands with an
odd number of band steps between them, and the parallel-
structure type of gain build-up between bands with an even
number of band steps between them.
Figure 10 - Six-band all-boost (i.e. feed-forward only)
extract of Hybrid structure EQ. The hybrid structure is
used in EQ Station's 'Classic960' algorithms.
Structure comparison with 3 adjacent bands set to +3dB
Let's see what response these three structures will produce
if we set 3 adjacent 1/3 octave bands with Q = 2 to +3dB:
Figure 11 - Examples of inter-band gain build-up with
identical settings and Q but 3 different implementation
structures
With all bands set to +3dB the difference between
implementation structures becomes even more
pronounced:
Conclusion
Figure 12 - Extreme example of inter-band gain build-
up: All bands set to +3dB
Filter structure consequences with a 3dB boost on all
bands
• The TC 1128 (Parallel) type adds
a total of approx: 7dB
• The 960 (Hybrid) type adds a total of approx: 8dB
• The Classical 27 (Cascaded type) ads a total of
approx: 10.5dB
As we have seen, a graphical equalizer is characterized
not only by its center frequencies and gain range but also
by its boost/cut symmetry, its Q (or bandwidth) as a
function of gain setting and its inter-band gain build-up
which depends on the implementation structure.
The EQ Station facilitates the commonly used graphic EQ
types in the recent past and should therefore be easy and
straight forward to use for anyone no matter your level of
experience.