I had a very similar experience when I wore Vanderfields (£20 slim profile, over ear protectors): good reduction on the highs abd mids but not much attenuation in the bass so you get a woolly, muffled sound. Good for watching a loud band but I'm not sure it good enough for playing on stage. I'm surprised no one had made a pair of these that you can physically adjust a small opening in the ear cups, thereby adding attenuated high frequencies. That would solve the woolly problem, wouldn't it...?