[sdiy] Filters

[Theo]

This hold true for LP and HP filters too, more ringing (higher section Qs)
allows for steeper slopes with the same number of sections.
(compare Bessel <> Chebyshev)
But with BP or notch it is easier to increase the Q without too much side
effects.

Cheers,
Theo

From: Grant Richter <grichter at asapnet.net>

> Bandpass filters get a little confusing. For example, a state variable or
> biquad has a theoretical 6dB/Oct slope, but with undamping (resonance) the
> actual slope near the resonant peak is much steeper. But the resonant peak
> has a tendency to "ring" adding holdover time.
>
> An unresonant (maximally damped) 36dB/Oct bandpass filter would require 12
> integrators (six for lowpass and six for highpass) but nearly the same
> effect could be achieved by a smaller parts count filter with some
> resonance. So it is a balance between parts count and the amount of
resonant
> "ringing" that can be tolerated.
>