Hi dbowker,
yes, the procedure is very expensive. But never in past was inhibited by that reason an advantaged procedure.
If you want to build a sophisticated plant, you need more as thousand single steerable speakers. The cost for first systems tops a luxory class car undoubted. But that doesn

Imagine you are situated in the Scala of Milan opera house, best place, great tenor sings. Suddenly unexpected some bricklayers come in, build up a little housing around you. You are angrily, 256$ for the ticket and now you can hear nothing!

But help is coming. One of the masons made holes into all walls, 10 cm in diameter, each on the other. Super, you hear Caruso as good as without the house. But now the electricians coming, sticking each hole by a loudspeaker. The sound is blocked again, but then, suddenly you hear likely the holes would be open. The electricians have supplied each speaker by a small amplifier and a microphone just on the outside of each hole. Nothing is changed, speakers and microphones working well today.

The problem is only; you need one discrete channel for each micro, if you want to build the speakers into your living room walls. The second, mostly bigger problem is your wife, if you want to load all walls around in your living room by loudspeakers.

The linked side does nothing else as describing a solution for those two problems. It describes a way for build up all different signals for the direct wave from a dry recorded mono track for each singer. The same signal is able for generate the first strong reflections in the recording room, which hit the listener from all different directions. Its temporally and spatial behavior is the core of each acoustic, but by conventionally loudspeaker reproduction we are far away from the goal, to be able for reproducing this spatial distribution roughly correct. The reverberation tail then becomes created from the impulse response, that's common practice in all studios today. The impulse response becomes suppressed for the early reflection time, so that the first reflections don't produce again. The reverberation is coming from all directions by such approach, likely in the opera house.

By including of the reflecting playback room walls, as it is known from the directed radiation used in the sound projectors, you can resign the loudspeakers all around, only those behind the picture screen remain. Your wife shouldn't' be able for discover that, the signal of each single speaker (holes) are hardly louder as the sound by the listener place.

But the speaker field isn't producing virtually loudspeakers, as doing in the sound projectors. The speaker field simulates the source itself. Nothing else is described on the website a little more elaborated.