Are my " diamond " tweeters really diamond

@helomech 

I fully agree with you but I see where this is going... Well, there are many non-diamond speakers out there as expensive (or more expensive) than their diamond competitors. Manufacturers are always looking for improvements and pushing each other. Call
it hype if you will, but my ears never heard as good speakers as we have nowadays (diamond or not) and the best ones are unfortunately big, heavy and quite expensive, regardless of the material used for their drivers. Such is life...

@luizfcoimbria,

Sure,  there have been advancements in some areas. IMO, the greatest gains have been in small, budget speaker performance. It's easy to make a large, heavy, cost-no-object speaker sound great. It doesn't have to push the boundaries of physics. 

The best speakers I've heard to date don't use any esoteric materials or cabinets. In fact, they're simply updates of 30+ year old designs. For example, Stirling Broadcast's LS3/6. They use a plastic dome super tweeter with a published frequency roll-off point of 17kHz. Many audiophiles would see that number and immediately dismiss the speaker as inferior. They'd assume these speakers lack detail or "air" compared to those equipped with a diamond or beryllium tweeter. Yet, IME, these speakers have greater resolution and detail than the B&W Diamond series and other highly regarded brands. 

So true. Not all soft dome tweeters are good. Speakers have to be voiced. Makes me wonder who they are voicing these things for. Certainly not me.

I am fond of electrostatic tweeters, myself.

Breakup is important. You don’t want to drive a transducer close to or beyond breakup. This is something the designer must take into account.

The key to soft domes is that they are intrinsically damped - doped fabric! This is the key! It means that the dome adds minimal coloration to the music. This is why they are so revealing - you hear the detailed music after a transient rather than the cone vibrations after a transient. Some folks are more critical listeners than others, so not everyone will appreciate this. You can see this on a waterfall plot, the excel millenium fabric dome tweeter has the cleanest waterfall plot I have ever seen. Some metal or rigid domes come close but the extra frequency extension of rigid domes is totally at the expense of clarity where it is more important - at upper mid range frequencies.