hi
I recently bought the MM-HLSO, which should take about the same SPL, and they distort like hell even at moderate loud concerts. I'm very disappointed, too. I built a 9v battery box to see if it's because of lacking powering (an R-09 does provide plug-in power, though not as much as 9v) - but the distortion is the same, only that levels are now higher...
regards
nicola