Thanks for the info, Cassroy. Sorry for the delay in getting back to you.
As a point of interest for others out there who are curious about the Sig III tweeters, all I can say is, these tweeters are what brought me back into the fold of dynamic speakers. Because I could always "hear" the tweeters in box speakers, I had long sworn off of them and opted for planers. After years of listening to Acustat IIIs and IVs, and Martin Logan speakers, thinking I had the ultimate in transparency, I learned to live with their short comings. Then one night I visited a friend of a frend and heard the Sig IIIs for the first time. He was driving them with a modified Dyna-70 and the sound was spectacular! I put my Martin Logans up for sale the next day and the rest is history. The tweeters on the Sig IIIs consist of a small dome tweeter and also a small ribbon tweeter. With them working together, I honestly cannot detect the tweeters at all. The highs are sweet and very extended. Honestly, with the tweeters working as they do, and the lack of a "box" sound, the Sig IIIs are everything I had with the planers ... but so much more. These speakers MOVE AIR! Again, they do their best with tube amps.