“At its best, Superunknown offers a more harrowing depiction of alienation and despair than anything on In Utero.” That was part of Rolling Stone‘s take on Soundgarden’s fourth album when it arrived in 1994. And now that the LP is turning 20 — and the band is celebrating with an anniversary reissue and played the record in its entirety at the iTunes fest at SXSW — the Seattle vets’ famous pals are speaking up about the record, too.

Here’s an incredible clip of Dave Grohl waxing philosophical on the impact his fellow grunge gods had on his life when Superunknown was released. Grohl, who directed Soundgarden’s “By Crooked Steps” video from 2012’s King Animal, recalls hearing Superunknown early, when producer/engineer Adam Casper brought the disc to Nirvana’s final recording session before it was released and offered the band a listen.

“He played ‘Black Hole Sun’ and I remember thinking, ‘Holy shit, this is gonna be huge,” Grohl recalls. “Because to me it was that perfect meeting of the Beatles and Black Sabbath, which is what I think we put in our Nirvana bio. But I don’t think that had ever successfully been paired until that record, and in particular that song. It was so much more melodically sophisticated than anything any of the other bands in Seattle were doing. It was a big deal.”

Grohl recalls discovering Soundgarden and being psyched a band that made rock music — not punk — was thriving in an underground scene. “To me they had that punk-rock, underground, do-it-yourself ethic, but they were playing really interesting rock music.”

Ultimately, Grohl remembers Soundgarden as groundbreakers. “Soundgarden were the first band to get out, the first band to sort of break, the first band to do the major-label thing in the underground scene,” he says. “It only made sense they were the first band to write a song like ‘Black Hole Sun.’ And that record really just raised the bar for everyone. Nobody had a voice like Chris. Nobody played drums like Matt. They were an incredible band. Twenty years later, that’s one of those records I honestly feel like your kid or your kids’ kids will discover and say, ‘Wow, dad, did you know about that band Soundgarden?’ 25 years from now.”