'Not sure, but doesn't brickwalling imply clipping?
Brickwalling and clipping are two different things from what i have read anyways.
yes, brickwalling and clipping are two distinct things. Brickwalling is when the analog circuitry overloads before the A/D reaches 0dBfs (the digital clipping point). Brickwalling can be hard to notice during a show, because your digital levels never clip or reach zero, so you might think you are OK.
In this case, my guess is that the brickwalling was caused by an underpowered mic. Typically, when mics have less power than they should, the max SPL that they can handle decreases.