I do not own RAAL-ribbon speakers (yet?), but the following video shows how to replace a RAAL ribbon and how to tighten a new or existing ribbon.

http://youtu.be/bvylZF9eJOA

The video is interesting in that it shows some of the internals of the ribbon tweeter.

Hopefully no one needs to do this other than in very unusual circumstances, but it's fun to watch (for me, anyway).