Much cricism has been made about the dispersion of ribbon tweeters. I have a pair of inexpensive 5" monitors with "isodynamic" ribbon tweeters. They are placed about 8' apart, with they're backs on the same plane as the widescreen that is between them. Listening to video in stereo, the sound stretches well the the outside of the speakers, but dialog is rock solid, sounds like it is coming from the TV.
These hivi tweeters do have a sort of shallow waveguide(?) that is gently rounded to the sides, which may help.
A well known DIYer tested ribbons and concluded that, at least on the bench, they didn't fair very well compared to good domes. I have had speakers with soft and metal domes, horns and these ribbons, and the inexpensive hivi ribbons have always been a favorite.
