Arti, Audyssey is an automated speaker calibration(sets levels and distances for balanced sound at the listening position)and room correction(modifies the frequency and time envelopes to partially overcome the distortions that all listening rooms impose on all speakers)system. Several such systems are available on various makes of receivers, but many(including me)consider it to be the most advanced system currently available on receivers. It's featured by makes such as Denon, Marantz, NAD and Onkyo. An included microphone is set at one or more positions to measure responses to test tones for the data needed for the calibration and room correction.
The 608 has the simplified Audyssey 2EQ, which measures from only two positions besides the central listening spot, and doesn't equalize the sub channel. The Audyssey MultEQ measures six or more positions for greater accuracy in the room corrections and also equalizes the sub channel for corrections in the important low bass frequencies. I consider that this easily justifies moving up to the next model level, which can be had, as I mentioned, for just a bit more.
