I took a couple days off of social media to focus on work. Glad to see the thread continues in informative and constructive ways.
@perkri -- just added the Charlap. Thank you!
@dodgealum My streaming service doesn't have the Uchida! I'm bummed.
@mahgister Thanks for the comments about the importance of room. I totally agree, and it's only because I have done enough work on the room that I am comfortable comparing speakers. The factor of the room has been neutralized (enough).
Thanks to others for the suggestions of additional instruments. I have added cello and also some woodwind quintets to my listening repertoire.
A speaker audition is a complex problem that is best solved by simplification. Piano is a single, more or less full range instrument, whose harmonics are well known to most of us. You can get to issues like tonal correctness across the audible spectrum and coherence/integration of drivers within a minute or two. If a speaker fails this, you move on and haven't wasted 2 hrs on a speaker that might seem ok with other types of music, but 6 months and 20K later you want to get rid of. I've personally not auditioned a speaker that passed the piano test and failed the voice test. My guess is there are none. But piano won't tell you a lot that you need to know.
@brownsfan Your recent post is a powerful brief answering the OP question, "Why is piano helpful?" It may also answer the (unasked question), "If you could only evaluate using one instrument, which would it be and why?" and "What provides the fastest assessment tool in the relatively rushed and untreated environment of the brick and mortar store?"
Of course, we are typically *not* forced to use just one instrument, and you're right to reaffirm that piano is not the *only* way -- let's all acknowledge he said that! -- but it is (perhaps) a uniquely powerful way.
I completely agree about reflective surfaces. This is a powerful tool that you've taught me about and which most people don't fully understand. In conjunction with room measurement tools, it is possible to sharpen the soundstage imaging without throwing too much deadening absorption at the room. The system remains focused and lively with the right kind of 12ms-50ms reflections that create the sound of space without smearing the images on the soundstage or creating too much brightness.