Yesterday I set up a pair of Lansing Iconics to listen to in stereo for the first time. I have blathered on about this in another thread:
At one point a slight buzz was evident in the high frequency driver of the left speaker. This Iconic is the oldest one I have seen, and uses the early style dividing network (serial #70) as pictured in the Lansing Iconic bulletin of 1937:
Anyway, I swapped out the 801 driver for another one and set the buzzing one aside for later inspection. This morning my friend Robert (who was collecting Lansing field coil stuff before I ever heard of it) took the ailing driver out to the shop to disassemble it. Shortly after, he ran into the house proclaiming a major discovery... this 801 has a radial slit phasing plug!
Considering the history of the Lansing drivers, this discovery actually makes sense. Jim Lansing had been warned by Western Electric (probably in 1936 or 1937) that his 284 large format compression driver (developed for the MGM Shearer Horn) was being built in violation of their patent on the circumferential slit phasing plug. W.E. was apparently beginning to produce their 594A at the time, a 4" diaphragm driver based closely on E.C. Wente's U.S. Patent #2,037,187. Lansing had his engineer Dr. John Blackburn seek a solution to this dilemma. Blackburn designed a 20 slit radial phasing plug for the large driver and it continued on otherwise unchanged as the model 285.
The Lansing Iconic was introduced in 1937; the earliest ad we have seen appeared in October of that year:
On September 1st, 1937 Western Electric signed a consent decree with the government to cease the supply and servicing of sound systems in theatres in the U.S. This evidently relieved Jim Lansing of the threat of legal action, and he soon resumed manufacture of his large format driver with circumferential phasing plug, calling it the 284B.
I had always wondered why the Lansing Bulletin on the Iconic referred to the high frequency driver as an 801, yet almost every example I have seen is labeled 801B. I believe that we now have the answer. Both large and small format drivers were likely converted to circumferential slit phasing plugs as soon as the threat of litigation was removed.
Unfortunately the label from this historic 801 was crudely removed by someone long ago, but it would have had a low serial number judging from the dividing network fitted to the same system. Another unusual feature is the rear cap, which was formed from heavy copper sheet and chrome plated. Most 801Bs have a painted cap which was formed from thinner aluminum sheet. Some later Altec era 801Bs have a die cast cap with the star pattern, as also seen on the field coil Altec 601 Duplex and early 604 Duplex.
The Lansing 801 is the direct ancestor of all the later Altec and JBL 1.75" diaphragm small format compression drivers. We now have evidence that the earliest commercially produced version used a 14 section radial slit phasing plug. Wow!