Like Bill said, I've always sort of considered any speaker built around the ideas found in the "Pi Alignment" paper to be a π Speaker. There have been some other configurations I've done that I'm proud of and that aren't in that paper, like the new eight π loudspeaker. There are also other documents you'll find here that describe ideas integral to most π Speakers too, like crossover designs and what-not.

So really, in my mind, a π Speaker is one of a handful of loudspeaker configurations that are commonly discussed here. It's a style or design type based on procedures outlined in the documents posted on the π Speakers website and discussion forum. But in the truest sense, a π Speaker is one that we've built or licensed to be built using information provided here.