The Zero 1, made by the German company Avantgarde Acoustic, contains a complete digital audio system within the speakers’ polyethylene cabinets. AirPort Express can be used to connect the speakers to a source. Each cabinet contains a DAC (digital- to-analog converter), allowing direct connection to digital sources; the signal is then routed through a digital crossover network and DSP (digital signal processing), which can correct for room acoustics. The three speaker drivers each have their own power amplifers, and the two speakers communicate via radio link. $18,500 per pair.