Oh these tweeters go way back. When they were in a Radio Shack model (probably a rebrand of what you have) they were considered a best buy by audio magazines (you needed a little something to address the boomy bass, but even so.) Lineaum was a speaker brand in and of itself back in the day.
Overall there's a tendency for soft domes to not be hard as nails, while metal tweeters fall more in the aggressive territory.
The main problem with most tweeters are the capacitors used. They are usually electrolytic, the worse possible choice. They simply behave very badly from an electrical standpoint, and replacing them almost always makes the speaker far more pleasing without losing any highs. Some people may perceive of losing harshness as losing highs, but that's not the case. (As much as you like yours Neil, what if it got that much better?)
There are many capacitors that will do a far better job and they may cost $3 to $5 each. For a small bookshelf speaker that single capacitor may be the entire crossover network. Why do they do this? Well you don't put a $3 cap in a $100 retail speaker. Such a speaker needs to cost $20 in labor and materials, so $3 is way over the top. That's the nature of business.http://forum.audiogon.com/cgi-bin/fr.pl ... &zzlinaeum
Frankly due to availability and personal choice I would choose a ribbon tweeter over anything else, and a full blown ribbon speaker if money and space allows. http://www.aurasound.com/index.php
Nothing at this site suggest they still deal with this tweeter. Such designs come and go, no matter how good they are, due to demand. The capabilities are frankly a bystander of their success, not the cause. Recall betamax? Posts referring the tweeter date back to 2005.
Ceramic tweeters are still in rage right now. A really interesting design I've seen is the powered driver, and by that I mean it doesn't use conventional magnets for the magnetic field it uses a coil with current flowing through it to create the magnetic field, and it's far stronger than anything in use today. There's only 1 manufacturer currently doing this, and you don't want to know what such a driver costs (I wonder if they make a dozen a year at this point) but I believe sound and speaker efficiency are through the roof, allow low powered class A electronics to make loud and wonderful music.
This speaker company also uses a unique tweeter in many of their models.http://www.roundsound.com/reference-35-speakers.html
Here the tweeter is in the middle:http://www.roundsound.com/reference-strada.htm
The world is full of interesting people, I'd enjoy talking to this guy.http://jeffsplace.me/wordpress/?p=914