I am another one of those students who worked at Hegeman Labs in East Orange and came away with a pair of Model 1As that I still have. My dad grew up with Stewart Hegeman, which is how I got involved with him. At the time I was there he was also building a larger version, Model 2 or 2A, and later tried his hand at some bookshelf speakers in an attempt to make money. I don't believe business was his calling. I did most things involved with assembling the speakers, but nothing to do with the electrical components. The high frequency diffusor mentioned above was just a ping pong ball filled with plastic and sliced. I spent a lot of time in a hot loft in the "Lab" mixing plastic to pour in molds for the tweeter housing. I recall his son going by "Pete" not "Phil", but that was 42 years ago, so who knows.
I don't use my 1As much, but they still sound fine and I never had any problem with the aluminum speaker cone. The foam grill covers long ago disintegrated, though.
Pat