When using the 24db/oct. hi/lo pass filters, I find the frequency stated on the frequency control-knob counterintuitive.
In most equalizers, there's a gentleman agreement to state the frequency for hi/lo pass filters as the cut-offs 3-db down point - mostly at the Q/BW setting that gives the steepest curve (relative to the number of poles in the specific filter) without ringing.
It seems that the steepest curve without ringing for GlissEQs hi/lo pass filters, is at a bandwidth of about 1.90 (as also stated in the manual).
At this bandwidth, the 12db/oct. filters stated frequency indeed matches the 3-db down point.
The 24db/oct. filters stated frequency is - however - from the 6-db down point.
So, the cut-off point I would expect when stating a 80Hz 24db/oct. hi-pass filter in most EQs, is in GlissEQ equivalent to a 24db/oct. filter at 64Hz.
I would very much appreciate an option to have the cut-off frquency stated at the 3-db down point, instead of the 6-db down point. While this is an inconvenience only, it would make it a lot faster to use the 24db/oct. filters (for me, at least) - and give the result one would expect compared to the 12db/oct. filters.
I am by the way very pleased with GlissEQ. Regarding the hi-pass filters, it is one of the few EQs where it is possible to change the cut-off frequency in real time without any obvoius artifacts.
The -6 dB point for -24 dB/oct (Linkwitz-Riley) filter was chosen to simplify use of GlissEQ as cross-over filter. This won't be changed in the future.
-3 dB cutoff point convention is mainly an engineering convention, it has little to do with music.
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