Sirius Investors Slam Perplexing $3.5 Billion Pandora Takeover

Sirius XM Holdings Inc.’s $3.5 billion deal to acquire Pandora Media Inc. struck a wrong note with investors.

Sirius suffered its worst stock plunge in more than three years Sept. 24 after the satellite-radio broadcaster announced the all-stock acquisition, which would put the company in more direct competition with Spotify Technology SA.

On a conference call with analysts, Pandora and Sirius offered little detail about how they would work together after the merger. Sirius CEO Jim Meyer spoke vaguely about “optimizing cross-promotion” between platforms. “My gut tells me — that’s where I see the biggest opportunity,” he said.

Sirius, backed ...