It is one of most expensive tweeters on the planet - the 2" pure diamond membrane tweeter Accuton BD51-6-585. The tweeters are being sold directly from Thiel & Partner GmbH (Germany) company to OEM producers only. The oriented price near $11300/pair with VAT included.
These tweeters are used in the top loudspeakers such companies, as:
Due that cosmic price of the product and the lack of any desires to take risks we did the measurements at safe 2.83 and 5.6 Voltage levels only. The measurements are given for the best sample from the pair