Sad news that Roy Johnson, speaker designer/proprietor of Green Mountain Audio, has passed away.
Aside from the loss to those who knew him, that's one less Time/Phase coherent speaker on the market. Not many passive T/P speaker brands left (Vandersteen...and?...)
Apparently, like Jim Thiel, he took a fair amount of the knowledge of the designs with him.
It looks like the slack will have to be picked up by active speaker designs, more of which are doing time/phase coherence via incorporating DSP.