Arnold Nudell has resigned as president of...

Arnold Nudell has resigned as president of Infinity Systems, a stereo loudspeaker producer in Chatsworth, which he co-founded 21 years ago with Cary Christie, the company announced Monday.

Christie, 44, who had been executive vice president, was named to succeed Nudell, 52. Infinity, which is one of the biggest loudspeaker manufacturers in the nation, is owned by Harman International Industries, an audio products concern based in Washington.

Christie said Nudell’s reasons for leaving “are personal and we’re leaving them that way.” But he said his departure did not stem from an internal management struggle. “Arnie and I are still friends,” he said.