Pi Alignments are for any type of speaker. They are not for a specific brand or type or characteristic. In fact, the formula describes an alignment that is very, very similar to Davies' 1982 optimal implementation of Thiele/Small analysis.As for usage, it's a general pupose alignment for full range speakers. Other alignments are generally better suited for subwoofers and other specialized applications. PiAligned speakers tend to be fairly small and slightly overdamped. This alignment works very well for woofers used in full range loudspeakers.