It was a massive logistical & financial burden -- but it was reported to sound excellent. Full but not loud. It had a short run with the band due to the cost and complexity (and some other mitigating circumstances in the early/mid '70s).
The idea was the band heard themselves on the same array that the audience did. The array's
behind the band -- no stage monitors! They employed some sort of phase cancellation via two mics per vocalist to stop feedback. It was a remarkable piece of lysergic engineering.

It was, unfortunately, before my time (in terms of live concert attendance). I am not sure how much the Wall of Sound was used, if any, on the East Coast, any way.