Industrialist Sidney Harman, who co-invented the high-fidelity stereo in the 1950s and became a dominant arts patron in Washington, died April 12 at George Washington Hospital. He was 92 and had complications from acute myeloid leukemia.

In a career that spanned seven decades and moved among business, education and politics, Dr. Harman was widely regarded as a polymath and a man of boundless vigor. In August, Dr. Harman became a media mogul with his purchase of Newsweek magazine from The Washington Post Co.

He had served as a ranking Commerce Department official under President Jimmy Carter and bankrolled the campaigns of his second wife, former congresswoman Jane Harman (D-Calif.).

In Washington, Dr. Harman — who had a fortune estimated at $500 million — shaped the city’s cultural landscape. He donated $20 million to build the 775-seat Sidney Harman Hall, which houses productions by the Shakespeare Theatre Company and the Washington Ballet. He also started the Harman Family Foundation, a charitable organization that gives money to benefit the arts, and was a major benefactor to the Phillips Collection in Dupont Circle.

Often described as a Renaissance man, Dr. Harman was a fitness maven — he walked 18 holes of golf into his 90s — and harbored diverse academic interests. He was chairman of the Academy for Polymathic Study at the University of Southern California, where he lectured on architecture, economics and law. Referring to his advanced age, he often joked he was “a smash in the school of gerontology.”

At social gatherings he would impress friends by reciting from memory Shakespeare’s “band of brothers” soliloquy from “Henry V” and sections of President Abraham Lincoln’s second inaugural address.

Although seldom shy about displaying his knowledge of literature and history, it was his skill in science and technology that launched his lucrative early career.

He had gone to work in the late 1930s for David Bogen & Co., a New York firm that manufactured public address system loudspeakers. He and a fellow engineer, Bernard Kardon, found that with slight modifications, Bogen amplifiers could be used to play 78-rpm records with astounding clarity.

In 1953, they left Bogen and founded a stereo business, Harman Kardon, with an initial investment of $5,000 each. Their invention, the first integrated high-fidelity receiver, became an enormous success and made top-quality home sound systems available to the masses.

By the mid-1950s, Dr. Harman bought Kardon’s half of the company and later expanded the business into the manufacture of speakers, amplifiers, microphones, recording equipment, touch-screen entertainment systems and automobile dashboard navigation devices.

Today, Harman products — including brands JBL, Mark Levinson and Infinity — are found in Chrysler minivans and Mercedes-Benz coupes, the Kennedy Center, the Sydney Opera House and Madonna’s recording studio. The Apple iSub, a transparent Harman Kardon subwoofer that resembles a plastic jellyfish, is in the permanent collection of the Museum of Modern Art in New York.

By the time he retired as executive chairman of Harman International in 2008, Dr. Harman’s stereo business had 11,000 employees and a yearly reported sales of $3.5 billion.

‘We opened Camelot’

Sidney Mortimer Harman was born on Aug. 5, 1918, in Montreal, where his father was a regional manager for a hearing aid company. The family moved to New York, where the younger Harman earned extra money with a paper route and sold discarded magazines to candy shops.

He was a graduate of City College in New York and received a doctorate from the Cincinnati-based Union Institute and University, where he wrote his thesis on innovation in the workplace.

After starting his stereo company, Dr. Harman spent more time pursuing a deep interest in education. In the 1960s, he helped Robert Kennedy open the Prince Edward County Free School in Virginia after county officials closed public schools rather than desegregate.

“Four thousand black kids were without school,” Dr. Harman told the Philadelphia Daily News in 2001. “We opened Camelot. I went down there every week for two days to teach and help out . . . putting my soul and money where my mouth is.”

Later that decade, he served three years as president of the Long Island-based Friends World College, an experimental Quaker institution. He worked at Harman in the morning, ate lunch and changed clothes before commuting to the campus. He stayed until after midnight seven days a week.

Respect for workers

At his factories, Dr. Harman constantly sought new ways to improve employee morale and efficiency and said productive workers are those who are treated “respectfully, fairly and ethically.”

At one plant in Bolivar, Tenn., Dr. Harman offered incentives to workers who made quotas early and gave employees more freedom on the work floor. The factory’s output more than doubled, and, for several years, the plant was a case study in innovative management. Certain perks, including a program that allowed employees to leave work early for increased productivity, stewed tensions among workers and the experiment did not survive. Dr. Harman eventually sold the factory.

The Bolivar project, however, caught the attention of Carter, who appointed Dr. Harman undersecretary of commerce in 1977.

He sold his stereo company to Beatrice Foods the same year for $100 million to avoid conflicts of interest. Beatrice, which was new to the audio business, ran the company into the ground. Dr. Harman bought it back three years later after his government service for $55 million.

“There are two ways to get rich,” Dr. Harman told The Post in 2001. “One is to sell your company to Beatrice Foods. The other is to buy it back.”

While in Washington, Dr. Harman met a young lawyer, the former Jane Lakes, at a Cabinet meeting at the White House.

“The main thing I take credit for is bringing them together in a Cabinet room,” Carter told The Post in 2001. “How proud I was when they fell in love and were married.” They wed in 1980.

Jane Harman served nine terms in Congress. In 1998, Dr. Harman financed his wife’s unsuccessful California gubernatorial bid. She resigned from Congress this February and is now director of the Woodrow Wilson International Center for Scholars.

Dr. Harman’s first marriage, to Sylvia Stern, ended in divorce.

Besides Jane Harman, of Washington and Los Angeles, survivors include four children from his first marriage, Lynn Harman, Gina Harman and Paul Harman, all of New York, and Barbara Harman of Needham, Mass; two children from his second marriage, Daniel Harman and Justine Harman, both of New York; and 10 grandchildren.

In lieu of flowers, the family has asked that contributions be made to the Catalogue for Philanthropy: Greater Washington, which the Harman Family Foundation founded.

‘Not in this for the money’

In August, Dr. Harman — saying he wanted to stop “misspending my youth” — came out of retirement to make a bid for Newsweek. Founded in 1933, it was purchased by The Post Co. in 1961. By the mid-2000s, its circulation was failing and it had lost money. The idea of a weekly publication in the era of 24-hour news propelled by the Internet seemed to many an anachronism.

Dr. Harman won over Post executives with his charm and work ethic. He purchased Newsweek for $1 and $47 million in assumed liabilities.

When Dr. Harman announced he would take over Newsweek, critics were quick to point out that he had no background in publishing.

“I’ve been preparing for this for nearly a century,” Dr. Harman told New York magazine in 2010, adding that he told Post Co. Chairman Donald E. Graham, “I’m in this to have a helluva good time. . . . I’m not in this to make money.”

He merged Newsweek with the Daily Beast, a news Web site owned by Post Co. board member Barry Diller and edited by vet­eran magazine editor Tina Brown.

Many media observers were surprised at Dr. Harman’s late-life career change, including his own spouse.

“My wife, remarkable woman, was at first resistant,” Dr. Harman told New York magazine. “She said, ‘You are naive about this city. It waits for somebody like you to pratfall and then it jumps. I’m concerned that after a lifetime during which you’ve built a sterling reputation, if this fails, they’ll be all over you.’ ”

Dr. Harman listened intently and responded: “I want to tell you something. If you think I have the reputation you summarize, then it arises from the fact that I have never paid attention to my reputation. It’s not what I worry about.”