I've been playing my 5500's with the h1212 replacements in them and they sound amazing now, better than the other I speakers I have - I don't detect any abnormalities to the sound - the air, and transparently is there now.
I'm going to put the original tweeters back in the speakers later today to see if they now sound as good as the h1212
Looking at the tweeter upon taking it apart I don't see anything that is super special about it that would be different from a replacement (h1212) especially if the electrical plot is comparable - sound wise they are a ton better than the old originals...
... later that same day...
I'm intrigued. What were the results of testing?
Cheers
Mike