Just realized you wrote Brylliom in your post, but not title. did you mean Berrylium?
Berrylium is a very light metal and if fabrication was not an issue, would probably be good for those liking metal dome tweeters....I have always found them a little....metallic, if you will. Berrylium is difficult to fabricate because of some allergic / or poisonous reactions to it in some forms, like powders or filings.
Design / execution / fabrication trump any simple material choice concerns.
a properly executed silk dome is better than a poor metal dome.
