Found some old literature from my employer back in the 70's. I am still digging thru those binders and I think there were a few others.
These are the cut sheets for the JBL made compression drivers that were sold to Dukane for their line of install products. At the same time JBL was selling to Heath, RCA, Fender, Sunn, Peavey ( yes..! ), General railway, tideland signals and of course, the military ( shhh ).
After 1981 or so, when the alnico was kept in-house by JBL, Dukane changed the driver source to a japanese company ( panasonic heavy industries?? ) and these are the vast majority that show up on ebay ( with the SAME number - thanks a lot ). They can be ID'ed by the METRIC hardware and recessed allen bolts on the rear cap.
Speculation is common about the types of diaphrams that were made and for who. Check with the "goes into" list on JBL's website for a little more info BUT I am sure that a lot of NLA material has been purged.
NOTE that if JBL made a component, it SAYS SO on the foilcal. That will end all arguments.
SP350 = 175HP ( pro number 2460 then became 2461 )
SP355 = 275HP ( no pro number until 2470 )
5A360 = 375 / 2440 with STAINLESS STEEL diaphram ! )
The "transducer" is the venerable slot ( 077 ) that had removable wedges inside the horn so it could be tailored to a specific intersection. More on that in the definitive " ring radiator rodeo and revue " coming up in about 2 weeks. Gonna need photoshop for this one.
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