Pandora co-founder and CEO Tim Westergren plans to step down from his position running the 17-year-old streaming music pioneer. The company has yet to select a replacement. Earlier this month, satellite company Sirius XM announced it would invest $480 million in the web radio service for a 19 percent stake in the company and three board seats. Despite a user base of 80 million, “Pandora has struggled to generate enough advertising revenue to cover the cost of the free service,” reports Recode. “Meanwhile, music listeners have begun gravitating to the on-demand subscription services of Spotify, Apple and others, which offer ad-free access.”