I gre out of Be Tweeters

I also like the AMT tweeter in the recent versions I've heard; they seem to integrate well with other drivers, something that is tough to do with ribbon-type tweeters.  

I have recently been wondering about what I really want a tweeter to do in a system.  I've heard some systems with full or extended range drivers with and without a tweeter.  The main benefit of cutting in the tweeter in these systems was not an extension of the frequency range, but primarily a smoothing out of the overall frequency response.

I have been listening to old and new (reproductions) versions of field coil compression tweeters (Western Electric 597) and I have been taken by how little one actually notices the tweeter--one just hears a smooth and natural sound.  It is not a tweeter that adds much obvious sparkle on top, but the systems I've heard just sound better with this tweeter.  The really bad news is the cost.  These things go from about $13k a pair to near $60k (souped up G.I.P. version), and they also need a power supply for the electromagnets.

I hate all modern hard and light material tweeters including beryllium, diamond, Spendor LPZ, Tannoy super-tweeters ...
All of them sound not natural, scratchy, itchy, intrusively, whistling, tiresome.

I have recently been wondering about what I really want a tweeter to do in a system.

This is true for many. I have grown out of sparkle, and air, and that seems to correlate well with smoother FR and lower distortion (when I've been able to measure them).

That doesn't mean you should. My point here is there's something like what I call a residual sound. Like scented body wash, and in the right music, environment that can be a lot of fun.

The most natural tweets, like Troels Graveson has said, to me, disappear. They sound like they are simply not there. The best AMT's can be there, as can the best diamond, and Be, and there are a lot of soft domes and ring radiators which are not bad in these terms.

The AMTs in Alta Audio speakers don't call overly attention to themselves.  I wonder what brand he's using.

Ultimately a large percentage of the final sound all comes down to implementation.  Even Be dome can sound very natural if implemented properly.  Inversely, one can have a pair of speakers with soft domes that can sound harsh and unpleasant if not properly implemented.