Today I went to a guest lecture by Marije Baalman on WaveFieldSynthesis (a spatial sound reproduction principle based on the Huygens principle) over at Concordia. I heard a demonstration of WFS at IRCAM a couple of years back, and it was good to (finally) get a good theoretical introduction to the field.
They are usually testing it with 24 speakers, but they are now going to make a permanent 900 speaker setup at the Technical University in Berlin for creating a surround WFS setup. Just imagine cabling that