Have you ever used a separate speaker selector unit to audition speakers? Would you?

@dbphd Is this what you mean? https://sites.google.com/view/pine-tree-audio/devices/transparent-selector

Thanks, @jetter  I do think you're right -- it's another tool to use. I guess what I've learned is that it's not to be considered a primary tool. 
That said, I have read some interesting things about the ephemerality of aural memory from sources which are bona fide scientific and rigorous. It's not just me, questioning what I just heard. It's well-documented that aural memory is subject to many physical and mental sources of error.

This will certainly degrade the entire sound.

@ebm I think we’re agreed on that.

If it's just being used to audition/compare speakers, rather than use them in-house long-term, if the different speakers are all hooked up to it, doesn't that level the playing-field?

@twoleftears 
I think it does level the playing field. However, what I take is being asserted as common wisdom means that is not so important.

This is what I gather the common wisdom is:

(a) speaker selectors degrade the sound. The question becomes "how much"? If they don't degrade either too much, then there is something to be learned by using the selector as *one factor.* (We have all compared this way, and I know from my experience that I heard some differences of a general kind worth heeding.)

(b) longer term listening is the primary way to make the comparative judgment. This kind of critical listening takes practice and patience and should not be sidelined by the urge to switch quickly.

(c) longer term listening renders sufficiently solid judgments that it makes what can be learned by quick switching negligible.