Wayne Parham Messages: 18883 Registered: January 2001
Illuminati (33rd Degree)
You might check out the formula in the PiAlign document. It shows what calculations are used. You might also be interested in the write-up of various alignments in the post called "Response curves of closed vs. vented systems".
About T/S specs, Eminence changes them periodically without changing model numbers. They have just recently gone through another revision for several of their speakers. Some models of π Speakers were originally designed for an earlier version Eminence driver with different specs.
This has happened several times over the years. Eminence has made many changes, a search through the archives will show several notices to that effect. If a driver change results in a non-viable system design, I modify the cabinet or drop the model altogether. But if the response isn't worsened by the driver spec change, I usually don't.