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.
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M100,VP160,QS10HPx2,EP800,M5HP,M3,M50 v4
M80,VP150,QS8x4,EP600 v2
ADA-1000-2,3,1500-3
Air N2