Blindjim, your question is in reference to Ralph's comment to me about the
impedance curve of the Sonata III, yes?
For full explanation of how he came to his conclusion about what he suspects
is the Sonata III's minimum impedance, he would need to chime in here. He
did not describe to me the method of how he determined this, and
therefore I cannot answer your question.
Ralph shared only his opinion with me based on what he saw on the Silverline
website about the speaker's design, and what he knew already of the drivers
utilized. Apparently, he is familiar with Silverline speakers, and has recommended them in the past for use with his OTL amplifiers, although Silverline Audio is no longer on his
speaker manufacturer list. I believe he still recommends certain Silverline models due to their more benign impedance curves than the Sonata III, but I do not know which models.
I have emailed Ralph with a link to this thread. Perhaps, he'll share how he
came to his conclusion.
Hope that helps.