FROM WIKIPEDIA:
"In the early 1960s, AR conducted a series of over 75 live vs. recorded demonstrations throughout the U.S. in which the sound of a live string quartet was alternated with echo-free recorded music played through a pair of AR-3s. In this ultimate subjective test of audio quality, the listeners were largely unable to detect the switch from live to recorded, a strong testament to Acoustic Research's audio quality."
"In the early 1960s, AR conducted a series of over 75 live vs. recorded demonstrations throughout the U.S. in which the sound of a live string quartet was alternated with echo-free recorded music played through a pair of AR-3s. In this ultimate subjective test of audio quality, the listeners were largely unable to detect the switch from live to recorded, a strong testament to Acoustic Research's audio quality."