Yes, I've heard them. In 1983.There used to be a place on Madison Ave (NYC) that advertised whole-house sound systems in the Sunday New York Times. An audio-minded friend of mine were walking past, had some spare time, so we went in.
They looked way better than the photos of them do, and imaged very well for the time. Unfortunately, they didn't have anything to play that we were familiar with (I remember being very frustated - they had Copland, but not the recordings I had, and it just went on from there). But I remember being very impressed - and JBL's as a group have never been favorites of mine.
There was also a "slightly larger than bookshelf" JBL that worked on the same principle. I heard them in the late 60's. My other favorite JBL.