most accurate loudspeakers....

Reference 3A is the most pure by far ,if you know what a real instrument sounds like then one listen and you
will know. The critical Midwoofer driver is completely made by hand in house the tweeter is far better then the stock ring radiators out there If your electronics are not bleached out like Naim for instance than go out of your way
to locate a dealer .

no speaker is accurate, period. most speakers state their frequency response within 3 db. that is not accurate.

at best one can a speaker is less inaccurate than another.

a speaker is either accurate or it isn't. it can't be incredibly accurate. it can't be slight;ly accurate. it is not accurate and not perfect.

there is no way to assess a speaker's accuracy. there does not exist a definition of accurate nor a way to objectively measure or calculate an inaccuracy score.

since we are expressing opinions, i would say the quad 57 is the least inaccurate of all speakers, within its range.

the thiel speakers sound top heavy, i.e., peaky in the upper midrange/lower treble.

Most of the producers and big studios use ATC while they record and mix. For home use I believe they are toooooooo flat. No salt, no sugar, no spice. Simply flat. But professionals like ATC because they give them confidence for the final product. For ex. Pink Floyd used ATC for all their recordings and band members use ATC in their homes.

I would vote for any speaker that:

(1) Has ruler-flat frequency response, at all power levels;
(2) Is completely phase coherent, at all frequencies and at all power levels;
(3) Has a completely resistive load at all frequencies, in order to present an entirely benign load to any amplifier;
(4) Has very high sensitivity, so "detail" is not lost at low SPLs;
(5) Does not interact with the room.

Trouble is, this is impossible with current technologies. Closest you'll find is an actively biamplified line array with a DEQX.

ATC and/or PMC are anything but flat and accurate. One more myth that some clever marketing guys had manage to sell the public. If you look at the history of ATC you realize why it is popular in studios. It has nothing to do with the way they sound.