Ok here it is:
"The Wall of Sound was an enormous public address system designed specifically for the Grateful Dead's live performances by legendary audio engineer and LSD chemist Owsley "Bear" Stanley.
The Wall of Sound fulfilled the band's desire for a distortion-free sound system that could also serve as its own monitoring system."
"The Wall of Sound consisted of eighty-nine 300-watt McIntosh model MC 2300 solid state and three 350-watt McIntosh model MC3500 vacuum tube amplifiers, driving the JBL speakers with a total of 26,400 watts RMS. This system projected high quality playback at six hundred feet with acceptable sound projected for a quarter of a mile, at which point wind interference degraded it. The Wall of Sound was the largest portable sound system ever built."
"The output was measured with an output capability of a clean 5hz at 120db"