All-pole filters matched to specifications

We present a new, general class of all-pole low-pass prototype filters that contain, as special cases, the most commonly used all-pole filters, and show how to design all-pole low-pass prototypes that are exactly matched to frequency domain specifications. This permits the design of filters with a continuous range for selectivity and passband ripple magnitude. For audio engineering applications the consequences are that for most practical applications, Butterworth filters can be replaced by filters of a lower order. Copyright © 2013 by the Audio Engineering Society, Inc.