Chess,
I'd love to have a true, blind A/B set-up to remove all the biases like you say.
The very first time i had an A/B blind speaker test, i couldn't tell the speakers apart.
Of course, that is also the point where i learned about critical, focussed listening. Then it is not unlike seeing that picture in the mosaic.
It was a very eye opening experience about the true subtleties of audio.
I suppose if all I wanted to do was A/B tests between 3 speakers, I could use a standard 7.1 receiver and place it into 7-channel stereo mode, right?
Mono mode, using the individual speaker setups to modify the gains with a switcher on the backside before the speakers in the chain might do it.
In the past i've only done matchups two speakers at a time.
Placed two speakers, one of each brand, ideally 12 feet to 15 feet in front of the listener location (helps to reduce L & R localization during playback but as a secondary test, i had turned my head to the left and right only to discover that what i heard with each ear was slightly different as well!).
The listener is blindfolded though the grille cloth idea works well too.
Single chair, limited width so the listeners cannot shift it around or exchange places and be sitting in a different location, even by a foot.
Volume matched speakers using the external amp with individual channel gain controls.
The listener could use the cdp control to reverse, restart or change tracks at will.
After that, things are variable how to proceed.
The switch person would begin with one speaker and then switch to another for a direct, a/b comparison with the blind part being the listener doesn't know which speaker is playing.
You could start with one speaker and then switch randomly such that the listener never knows which speaker is playing.
Or you could even have a third person setup the whole thing such that neither the listener nor the switcher knows if any, all or no speakers are up front whatsoever!!
This is where that third person can really play tricks on the listeners by swapping in some Bose Acoustimass stuff, Grandma's ten dollar Dollar Store receiver and so forth when they think the two speakers that SHOULD be in front of them are their high priced, quality gear.
It makes things very interesting.
