The Notch Filter - Hughes & Kettner BassBase 600 Manual

5
Even though you handle the VARIMETRIC the same way you would a conventional semi-parametric EQ with
its fixed filtering, it is a much more sophisticated sound-shaping tool. The filters, rather than being geared to a
fixed frequency range, are variable, enabling you to fine-tune your tone for a truly musical result.
This frequency diagram depicts the effects of the VARIMETRIC EQ on the lower-midrange. As clearly
illustrated, the boost of a complete octave range is very well-rounded and even, ideal for clearly establishing
the basic sound character. Attenuation occurs at a much narrower bandwidth to allow you to accurately target
undesirable frequencies. If you amplify a given frequency range, the frequencies bordering its outer
parameters are smooth out with a touch of attenuation, and if you attenuate a given frequency range, the
frequencies bordering its outer parameters are gently amplified, achieving an audio contour which intensifies
the overall EQ effect.
Mid/Treble equalization: The higher the frequency, the broader the bandwidth processed by the VARIMETRIC
EQ, much in the way the human ear registers the upper end. Attenuation occurs at a much narrower
bandwidth so you can accurately target undesirable frequencies and avoid the dreaded broad-band hollow
midrange effect.

4.3 THE NOTCH FILTER

Undesirable frequencies such as those caused by resonating objects in the room or floor boards in the stage
can be suppressed via the NOTCH FILTER. The NOTCH FILTER operates in extremely narrow bandwidths
to avoid altering the overall sound. Adjust the NOTCH FILTER as follows: