Hi Mordante , where did you listen the Raidho D1 speakers? I too have spent 2-3 hours with them last friday (in Amsterdam at A10 audio).
Bo1972 make two very good points:
1) How the tweeter is made is very important (probably as important as the material), e.g. to me the Focal beryllium tweeters always sounded better than the B&W diamond ones.
2) There are ribbon tweeters (quite a few in fact) that are at least as good as the best dome ones. The Raidho ribbon tweeters are among the best tweeters available at the moment, and chances are that no dome tweeter can touch them.