Is oscillation bad for an active audio filter?

A Butterworth filter has a flat response to near the corner frequency then a sharp corner that you want.
A Bessel begins dropping its response far from the corner frequency causing a droopy response and a gradual corner that you do not want.

To make a "perfect" Butterworth filter with a gain of 1, put two of the same same capacitors for a lowpass or two of the same resistors in parallel for a highpass in parallel since many values are not exactly doubles.

Super-Dave said:

Let me see if I get this straight, the big difference from Bessel & Butterworth are mainly dependent on the ratios of the caps or resistors in the feedback loop vs ground? A ratio of 2:1 or better is Butterworth, less is Bessel? Then what is a sub-Bessel?

Click to expand...

Super-Dave, you should try to become somewhat familiar with a very important filter parameter: Pole-Q.
This parameter desrcibes the position of the second-order pole pair in th s-domain - and it has a very direct relation to the magnitude and phase response of the filter.
This parameter (pole-Q) is the only one which numerically characterizes the various response alternatives for a second-order filter ("lowpass approximations" to an ideal "brickwall" lowpass response).

Examples: Critical damping (Q=0.5), Bessel (Q=0.5773), Butterworth (Q=0.7071), , Chebyshev (0.9565 for 1dB ripple),