I've uploaded a third draft of my crossover demonstration document. This publication includes third order networks as shown on the Pi Speakers schematic, but the table of contents hasn't been modified to include the updated pages. The TOC still only shows first and second order networks.Compensation networks are discussed in some detail, including RC dampeners (Zobels) and Pseudo Butterworths. No new information about dampening resonators (notch filters) or series and series/parallel attenuators is provided, but the document is replete with examples of these types of compensation networks already.
The models shown on this document and the Spice executables are still available in the Spice models distribution on the Pi Speakers website. Also included are models for the third order networks used in Pi Speakers.