I can tell you my v2 tweeters were breaking up on my QS8s and my M80 with concerts and PLII music. I always thought it was the recordings. When I got my v4, all that breaking up disappeared and I was left with beautiful sound.
M100,VP160,QS10HPx2,EP800,M5HP,M3,M50 v4
M80,VP150,QS8x4,EP600 v2
Air N2