Any ideas on armature gap settings for 1920's horseshoe drivers? Cleaned up a badly rusted one and now not sure how much gap is correct. This driver attaches to the cone with a soldered joint so trial and error might be difficult. It's from a '28 Mohawk Pyramonic. --Matt

Over the years, I have had to reset many armature driven cone speakers and Utah/Baldwin armature speaker drivers for horn speakers. Dead center is really the best setting to go for the armature.

I just wedge two pieces of dense paper or cardboard (1 mm thick or less) between either side of the vain/armature and the poles. The paper that I use is paper that I tear off from the packets of NTR resistors that I buy. Once the wedges are in place, I solder the connection between the armature and the driving rod until it either clicks or settles in place. When the solder joint is cool enough, I remove the wedges. That's all there is to it.