What speaker has the best high frequencies?

I have a Spatial Audio X5 with a wide band horn loaded AMT (Air Motion Transformer) which handles high frequencies (1k and up?). It is big, about 6” x 1”. I feel it is much better than the 1” tweeter found in most speakers.  I honestly don’t know how this AMT is different from, say, ribbon tweeter.  This leads me to think, who or what speaker has the best high frequencies?  I heard good things about the B&W diamond tweeter, but it is still a 1” tweeter.  What else is out there?  I think size makes a difference.  In this case, is it a larger ribbing tweeter better than most 1” tweeters?  
Tastes vary, but I would say it would have to be the one playing Jennifer Warnes.
I has to do with what you like. I’ve used AMT. Some are very well behaved, some can drive you nuts. The reason for the lower XO point, some can go pretty low, for tweet duty. The problem is the higher range they can be tough to manage..

I Normally used them as a mid more than a tweeter. 300-12 khz or so.
Then I use a true ribbon and/or a planar, depends..12 khz up..

No hard domes for me. A lot of the manufactures use them.. they suck.. simple..
I don't care who makes them...

Aurum Cantus is one of the best tweets top to bottom...Either Striction or Ribbon

I try to only use round speakers from 300 hz and down. It makes for a
VERY fast system...Ribbons, planars and domes, are all faster than any round/cone style speaker...

theoretically the ones with a super tweeter 
While I have never heard one, I believe that some would say speakers with a plasma tweeter have the best high frequencies.  
The one with all the cables and fuses in the correct direction. 🤗
Sorry, no dice. 🎲🎲 Jennifer Warnes is digital. 🙀
Lansche or Acappela with ion tweeters give the best extension and clean treble.

Vintage Western ion tweeter sounds even better to me ( I have a friend who own them) but they are almost unobtainable.

ESS was a good one too. Actually a great topper for the older boxes
Didn’t JBL used something like that too. Not real savy on JBLs.
AMT an older JBLs? 45 years ago, or more..

I know, I like the sound of JBL. Just I couldn’t afford what I really liked.

+ 1 more for Mrs Jennifer Warnes can we add a few more? 

I've not heard it, but if that's the Beyma AMT I've read from many a DIY'er it is among the best performing tweeters in the world.  Great dynamic range without compression, very low distortion, and the horn adds controlled dispersion, guaranteeing a clarity at the listening location you are unlikely to find anywhere else.

While not AMT's are created equal, some manufacturers use really awful versions, they all share in low stored energy, the equal or better of Be or diamond tweeters in this specific regard.

B&W diamond tweets are not nearly as natural.  If you've ever walked into a store and said "Oh, I hear a B&W speaker!" you know what I mean.
The usual people posting their usual dribble!
Hey Mr. palbrecht1, the word you're looking for is "drivel". The other word is for your personal problem, or your puppy.
Always here to help...
Post removed 
Maybe we can agree that a tweeter that goes in when it should go out is not great ?????
The ribbon tweeter (raal) specially made for ascend acoustics in their sierra towers has an amazing amount of clarity. 
I’ve tamed the Heils and they sound great with plenty of top end extension. I use them in a 2.5 way with JBL 2241H 18" and JBL 2251J 10". My own design crossovers.

I created acoustic lenses for them and insert a piece of foam to the rear to reduce reflections improving imaging. Here you see the RTA on the couch where I sit. There is no eq or digital processing of any kind being used here nor is the room acoustically treated in any way

Curve is actually a bit smoother at the top than shown due to additional crossover mods I’ve made since. Ignore the "floor/wall bounce depressions" at the low end.

Note this is ~+-5 dBA from ~32 Hz to beyond audibility (with a nice smooth curve) on the couch with no eq or room correction being used! And no woofer foams to ever replace.

http://www.audioheritage.org/photopost/data//500/medium/DSC_00171.JPG http://www.audioheritage.org/photopost/data//500/medium/DSC_00151.JPG

Take a listen:

Amps/preamps with tone controls would have come in very useful right now. You could have just turned up the treble and voila. Simple.....
Well, since size of the tweeter is your criterion, then the "best" would be the three panels in the Kingsound King III electrostatic speaker, of course. (reviewed for Dagogo.com) 

An AMT tweeter is like a bellows it’s surface area is 3-4 x it total
dispersion area that is why it too has a wave guide .The Spatial use a huge AMT to cover midrange on up ,where others use a specific driver just for midrange which ion a $$ speaker is more costly like a Accuton driver, which also use a diamond particle tweeter which is $$ but very accurate. The spatial is very good 
upgrading or requesting a Xover upgrade will bring Huge results most everyone skimps In capacitors resistors , Path audio best made period but $30 each , vs $3 ,and many upgrade capacitors available. Inductors like a Jantzen great quality,value not too costly 
but many use cheap bobbin type or called sledge hammer coil of 
wire around a magnet 🧲 you see this often in many under $10 k 
just to save under $100. Just for the record when ordering ask to 
have Xover upgrade options  humble homemade Hifi capacitor test gives a very good comparison for modt caps.
Spatial uses a Beyma AMT made in Spain which is very good 
other companies use a smaller AMT just for upper frequencies like Monitor audio for  example Their pl500 can go up to 100 k which is class leading ,even their studio can go to 60 kHz which is like a super tweeter. 

Nola Metro Grand Gold 2. Nola uses a 4 inch ribbon tweeter sourced from Raal. They reach high frequencies like I’ve never heard. Very detailed but never harsh

X3-06 EXOTIC T35

But I have heard them also with a solid copper modified baffle.

The brass terminals were replaced with copper tubes, and the leads crimped and soldered.

There is no one speaker that has the best high frequencies.
Electrostatic is my choice followed by Plasma tweeter
Having heard several variants on plasma and ion speakers back in the very early days of HP's Absolute Sound evaluations (back when the "magazine" was little more than a dozen pages, stapled and folded). I'd have to say that they reign supreme; however, they have never been practical commercially.

Of those designs that have survived as commercial products, electrostats (martinlogan, dayton-wright, others) and magnetic ribbons (Heil, Magnepan - different, yet similar in principle) are probably the best.

I fell in love with the original CLS speakers playing string quartets when I first heard them. And, I owned a pair of Monolith III's that I bi-amped using the Dahlquist DQ-LP1 active crossover.
I've been following this thread with interest but waited to comment.  I was wondering when and if the Magnepan true ribbons would be mentioned.   I have never owned any of the top tier speakers.  I've auditioned just a few speakers that retail north of 10K.  So I'm not really in a position to speculate on "the best" tweeter.   But I will say without hesitation that the best tweeter I have heard is the Maggie true ribbon.  It is the one thing I really miss since moving away from Maggies.  The tweets in my MG 3.7s were heavenly.  They never got overly aggressive.  They were very resolving, free of grain and breakup, sweet as honey and smooth as silk.  
 Magnepan 3.7 WOW I forgot about that speaker. That is a really good speaker.  I heard the 3.7i with Mac C50 and SS MC601s (I think). He was selling the C50. I was really impressed.  Did't buy the C50, sure was tempted to make an offer on the MG 3.7i though..

We listened to Strunz & Farah "Rainmaker". WOW! Top 5 best production speakers I've ever heard, excellent indeed.