the hall isn't part of the sound system. the power amps, the speaker cabinets, the mixing board, the wiring, etc - those are part of the sound system.
my reading of that quote is that the PA wasn't tuned/eq'ed properly, or it distorted, or crackled, etc.
i'm pretty sure if the writer wanted to say the hall sounded bad, he would have said "the hall sounded bad".