In the 1970s, back in the Advent days, I'd heard Henry Kloss tell stories about well-intentioned people designing speakers with the goal of a perfectly flat frequency response curve. It turns out that speakers that look perfect on paper often sound lifeless and flat. And while measurements certainly had their place, they were only part of the process.
A good speaker designer -- like Henry Kloss or Winslow Burhoe -- will do so much voicing work, with so many different speaker/cabinet/crossover variables, that they can predict how a speaker will sound without ever having played music through it.
Anyway, back to 1997. I finally cornered (literally) Henry back in his work area, told him about the article I wanted to write, and asked him what he thought was the secret to designing great-sounding speakers. He scowled (I think it was a scowl, it may have been his "normal" face that day), turned around, walked away 10 feet, and stood there thinking. About a minute later he turned around and said, "Fussing, fussing and fussing." Then he went back to work, without another word.