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6.1 Bell Filters
Q Definitions
P – 3dB – Classical definition that means Q is measured 3dB below peak for boost or 3dB above peak for cut.
0 – 3dB – Definition used for bells in some US products, the bandwidth for Q calculation is measured 3dB below 0dB line for
cut or 3dB above for boost. Q in both definitions correct only for +6dB boost/cut.
P/2 – New “musical” definition based on the bandwidth measurement in the middle of a bell filter, between peak and 0dB line.
Normalisation – All 12 equalisers are normalised to have exactly the same bell shape for +6dB boost.
Classic Symmetrical
The most popular parametric EQ shape used in various mixing
consoles and outboard gear. Almost constant Q characteristic.
P – 3dB
Classic
Asymmetrical
Often features in older equalisers. Boost as above but much
narrower cut characteristic.
P – 3dB boost
0 – 3dB (x2) cut
6. X-EQ Filter Types