Audiophiles are quick to name the umpteen flavors of Dolby, but when you go back to basics, there are just three types of surround sound today -- each easily identified by their plug. Virtual surround uses just a single stereo jack, emulating multiple channels from two, while digital surround travels across optical or coaxial S/PDIF cables (or HDMI) and has to be decoded. Finally, there's analog surround sound -- the cheapest solution of all -- where you basically just plug a pair of dumb speakers into each of front, rear and center 3.5mm sockets on your existing PC sound card. Unsurprisingly, the $100 Logitech Z506 speakers use this last technique to deliver their true 5.1 sound
