One has to wonder what they did to compensate for the natural roll off of the highs that would exist. Cone speakers droop fairly fast as the distance increases. Not so much for panels/electrostats I think. I recall many years ago trying to get FFR at the listening position with some cone speakers that were +/- 2db a 2 meters. It took an equalizer and sounded way too bright and unnatural.
What type of speakers were they?
What type of speakers were they?