In my personal opinion and from listening experiences, I would not touch that DQ25 tweeter with a 39.5 foot pole. I know it measured well for John and is why he used it in his line of kits, but there is something that has not been quantified in its measurements. It has this 'broadband glare' (a peers words) that comes through when in use that is not apparent during sweeping style measurements. Give it sine waves, and it seems okay. When played above xover full spectrum it really does sound broken to me, and some other builders.
FWIW, PSB used it in a line of their speakers, and I could immediately tell it was that tweeter. I turned around and left the demo room.
Rumor mill says it might be on Tymphany's chopping block in the near future, and I welcome its demise.
Interesting, as I have never heard it.
On a more general note, I wonder if time hasn't passed a lot of the Zaph designs by.