I could be mistaken but I used to take apart many old radios that would have these, back when the electromechanical speaker would weigh like 25 lbs, with a big auto-transformer driving the speaker.
Doug,
In some of the radios of that era, the matching transformer on the speaker had more than one function, hence the wieght.
I have seen a bizzare set-up in an old Bell radio-gram here that had a single (E-I) laminated steel core and the audio windings were on one side of it and on the other side was a single winding that acted as a choke for the power supply section, for smoothing purposes.
This is not an un-usual thing, considering the layout of radios of the day, there wouldn't have been room for a decent sized choke, it is strange that it was put on the same core of the audio output transformer, without any interference.
It worked like a charm though, them radios sold like hot cakes here in their day.
