ETF horn link is here:

European Triode Festival - ETF 2010 Shootout


I should add that the Klangfilm horns are often used with diffusers which look like air duct vents. They call them "acoustic lenses":

See here under "documentations" Klangfilm Home!

Although this might be a beneficial addition for the intended theater application, I didn't find these horns to be objectionably beamy without the acoustic lens.