Great issue. How to rebuild a Quad, room correction and Keith Howards Down Deep article. Technical data. Love it.
But could Keith explain the definition of "phase distortion"? Is he refering to simply phase shift vs frequency? Not to infer that phase shift is not important. I understand phase shift caused by a electrical circuit such as a crossover, but I am having trouble grasping the concept of phase distortion caused by a speakers inherent bass rolloff.
Especially if the speaker is flat down to the lower frequencies of hearing.