To me, the Wall of Sound was the giant wall with speakers stacked up to 32’ high (I’ve been told the 32’ stack was for Phil’s E string which put out a 32’ foot wave, crest to crest, and Phil wanted to put out the whole wave, not just a piece of it. I don’t know if that’s true, but it sure is a great story). The Wall served as both FOH and stage monitors with all speakers behind the band, and employed the double mics. The band continually experimented with sound both pre and post Wall, but the systems included floor monitors or, later, IEMs, and no double mics. But when the great majority of Deadheads refer to the “Wall of Sound”, they are specifically referring to the 1974 system.
Bill, tgo (who, as Peter reminded me, certainly “felt” the Wall as well as heard it).