They blew their ears out. Alex Van Halen is nearly deaf. I remember a lot of concerts in the 70's that were physically painful.to be at, the band was so loud. Im sure I have at least some hearing damage. The worst one I remember was Carlos Santana, mind-bendingly loud. Half the audience walked out. It was like somebody poking your eardrum with an icepick. Inexcusable.
I remember concerts like that and that godawful obnoxiously loud kick drum which hurt which I've always hated even though I love kick drum and play with it, but that's the sound person's fault not the band. I went to a Neighborhoods concert in Worc MA years ago and the sound guy put the kick drum so loud he blew either some of the subs or the sub amp, it was obnoxious.

