This system projected high-quality playback at six hundred feet with an acceptable sound projected for a quarter mile, at which point wind interference degraded it. The Wall of Sound was the first large-scale line array used in modern sound reinforcement systems, although it was not called a line array at the time. The Wall of Sound was perhaps the second-largest non-permanent sound system ever built. The Wall of Sound can be seen in "The Grateful Dead Movie", a documentation of the series of shows played October 16–20, 1974 at the Winterland Ballroom.