This type of technology was
discussed in Popular Science a few years ago. I'm unsure of the implementation that Yamaha is using, but the technology goes way beyond HT apps. Marketers, for instance, are planning on using it to direct aural "sales messages" in a very narrow beam to shoppers. O, for instance, when you walk in front of the B&M beans, you'll hear about a special or why those beans are the best. Someone just three feet away to the side of you won't hear a thing. Scary when you think how you can be bombarded with marketing in that way… or how someone playing poker can get a "feed of a read" whispered in their ear from 20' away and no one else hears it.
If I remember right, the technology is based on matrixing or interweaving sounds in our spectrum to very, very high (and therefore directional) frequencies. Yamaha's implementation for HT follows what was mentioned in the article for that application: A single set-top box that reflects your sources so you hear sound as originating from different locations. I haven't read any reviews of the Yamaha, though.
