Significant discovery

[Steve Schell]

Lately I have been building some new field supplies to power some old Lansing Iconics that have been silent for far too long. While in the process of setting up a couple of them for stereo, one of the Lansing 801 field coil compression drivers was misbehaving a bit, so I substituted another one. When the noisy one was opened for inspection this morning, my friend and I were astonished to find that it has a radial slit phasing plug! This driver is early, likely built in 1937 or 1938, though its nameplate has unfortunately been removed. The dividing network used in the same system has serial #70.

The Lansing 801 was the original 1.75" diaphragm, 1" exit driver, ancestor of all later Lansing, Altec Lansing and JBL 1" exit small format compression drivers. It now appears that in its earliest version it was built with a fourteen slit radial phasing plug. In over ten years of collecting old speakers and studying their history, I cannot recall a more exciting discovery.

I began a thread with more detailed discussion and pictures over on the Lansing Heritage forum:

http://audioheritage.org/vbulletin/s...ad.php?t=16973

[Tom Brennan]

That's very interesting. I love your history articles Steve.

And you write well too.

[Todd W. White]

Steve,

Dr. John K. Hilliard & Dr. Blackburn designed a radial phase plug for the Shearer System, as shown in John's book from that era. It was far too expensive to machine (no injection-molded plastics or CNC-machines like we have today), so they opted for the circumferential style when in production mode.

It is possible that Jim Lansing, who built the parts for the Shearer System and worked with Blackburn, put the radials in there at his instruction (Blackburn would have had to design it, as Lansing was not an engineer), and some of them got "out there" before it got too expensive and, as Lansing slowly went nearly bankrupt, cost-saving measures, such as using the less expensive to manufacture circumferential phase plug, became increasingly important.

[bfish]

Regardless of the "facts" I respectfully submit that I find the continual dissing of anyone or anything non-Altec to be in bad taste, and particularly unbecoming of a leader.

This includes barroom jargon like "Extra-Vicious", "Just Big and Loud", and "Pukane".

Either get even, or get over it. Vinegar just gets more sour with age, eventually it'll make you really sick.

Respectfully,

[Davidg]

I've just re-read this thread over about 4 times to try an figure out who you feel is dissing who, and I still don't know

I did find the information and history very interesting tho. Thank you gentlemen for you dedication and hard work

[Todd W. White]

Bfish - what are you talking about?

[bfish]

Elaboration would just blow it out of proportion to the intent. If you don't get it, you don't get it. I don't intend to make it worse, and I can't edit it to make it better.

Just an oversized bit of grit in my craw I've needed to cough up for some time. I coughed it up and feel much better now. Carry on.

[Todd W. White]

OK - will do.

[Steve Schell]

Todd and I have in the past, I think, agreed to disagree on the merits and accomplishments of Jim Lansing as an engineer. I am just trying to figure out how this very early 801 compression driver with its radial slit phasing plug fits into the history of these drivers.

What we do know is that the original 2.84" voice coil compression driver built by Lansing for the initial Shearer System prototype systems used an annular three slit phasing plug. The Academy Research Council published a Technical Bulletin dated March 3, 1936. Written By John Hilliard, it was called "A Study of Theatre Loudspeakers and the Resultant Development of the Shearer Two-Way Horn System." I have an original example of this publication. In this bulletin a high frequency driver identified as the 284E is shown in sectional view, and an arrow pointing to an exit on the phasing plug surface is captioned "Annular exponential openings."

The model 284 as it was called in production used the three slit phasing plug, virtually identical in shape to that used in the later Altec 288. My Lansing Monitor 500A system, likely built in 1936, was fitted with 284 serial #176. By this time Lansing was building his commercial version of the Shearer Horn, and several hundred examples of the 284 driver were built.

At some point Western Electric objected to Lansing's use of the annular slit phasing plug, claiming that it violated their patent. This appeared to be true, as the 284 was a downsized version of Wente's compression driver (U.S. Patent #2,037,187) developed for the Fletcher System of 1933, and was similar in most other respects. Lansing asked Dr. Blackburn, his employee at the time, to seek a solution. Blackburn designed a twenty slit radial phasing plug (U.S. Patent #2,183,528), and Lansing's driver continued in production otherwise unchanged as the model 285.

In 1938 the Academy Research Council published a book titled "Motion Picture Sound Engineering." John Hilliard's 1936 Technical Bulletin was reprinted as one of the book's chapters, with revisions. The revised compression driver sectional view depicts the Lansing 285 driver with radial slit phasing plug, and the text describes the plug as a good performer which is easier to construct than the annular slit plug. No mention is made of any legal difficulties.

On September 1, 1937 a consent decree was signed with the government which removed Western Electric from the supplying and servicing of sound equipment in motion picture theatres in the U.S. About this same time Lansing disproved W.E.'s patent infringement claim, citing prior art By Bell and Tainter in acoustical phonograph design. Now freed from the threat of legal action by Western Electric, Lansing soon returned to the use of an annular slit phasing plug in his driver. The 285 was replaced by the 284B, which used the same three slit annular design as his prior 284.

The Lansing Iconic two way system was introduced in 1937. The earliest advertisement we have seen for it appeared in the October 1937 issue of Electronics magazine:

http://www.lansingheritage.org/image...lectronics.jpg

The Iconic equipped with this remarkable 801 driver with the tangential phasing plug is an early one; the dividing network is marked serial #70. I had always wondered why the Lansing Bulletin on the Iconic described the high frequency driver as an 801, yet almost every example I have seen was labeled 801B. I believe that we now have the answer to this question. The Iconic was introduced at the tail end of the period when Lansing was building the radial slit phasing plug. When the legal concerns were removed, both large and small format drivers were converted to annular slit plugs and given the "B" designation.

[Todd W. White]

Steve,

When I read "Motion Picture Sound Engineering", I got a different impression - it looked to me as though Hilliard was stating that the radial was, in fact, a superior design which they had wished to use, but was more expensive and difficult to make (machine), thus the reason they built the circumferential model.

I'll have to go back and re-read Hilliard's writing on that - well, actually, I'll have to call Dave Read, because he borrowed all of my Hilliard papers for an article on John and book he's writing on the history of Altec - I'll see what his take is, but I remember Hilliard being reported as holding up the very book I have (loaned) with the radial phasing system when Altec introduced the Tangerine and saying, "Gentlemen! It's all been done before!"

I'll talk to Dave Read tomorrow and see what I can find out - he also has all of the actual articles Hilliard preserved (and catalogued in binders), so we may be able to find out more...