I used a Scanspeak D2905/9500 1" textile dome tweeters.
That is indeed a nice tweeter.
The Vifa DG25AG35 is a not good tweeter particularly when driven hard. It has fantastic specifications and is cheap...that is all...it simply does not sound natural. It is a great and cheap tweeter if you want to sell speakers and impress reviewers with an amazing on axis frequency response (no matter how bad it sounds)
One problem is when tweeters are crossed over quite low at 2Khz or less - on a big speaker like that you tend to crank it and the first thing to compress and sound distorted is the tweeter.
A second problem is the dispersion.
FWIW: The D2905/9500 has what looks like a waveguide loading. It is similar to the old tried and true Vifa D27TG-45-06. I suspect that the horn loading helps give it more headroom at lower frequencies before it compresses, as well as creating a more natural dispersion. A waveguide is tehrefore beneficial for TWO reasons. If you look at most pro designs (see Genelec 8050a
) they often use "waveguides" or a slight horn loading on tweeters.
See this interesting link
for some details...