A deal to sell Newsweek to a 91-year-old stereo equipment magnate will be announced later this afternoon, a move that will signal the end of a half-century of ownership by the Washington Post Company.

One person familiar with the sale process confirmed that the Post Company was preparing to make the news public, having formally wrapped up its discussions with Sidney Harman, the magazine’s new owner.

The sale to Mr. Harman, who started a business selling FM radios in the 1950s and built it into one of the largest audio equipment companies in the world, shows just how particular the Post Company has been in choosing a buyer.

As the sale process played out over the last two and a half months, The Post and its chairman Donald E. Graham have turned away several potential buyers whom they believed would lead the magazine in a markedly different editorial direction or make deep staff cuts. Mr. Graham, who is said to be concerned not only with the magazine’s legacy but the legacy of his family’s stewardship of the magazine, wanted the sale to be as nondisruptive as possible.

According to several people who have been briefed on the process, Mr. Harman’s bid appealed to Mr. Graham and the Post Company because Mr. Harman has said he would retain a significant number of the magazine’s 325 employees. The financial details of the sale were not known, though one person with knowledge of Mr. Harman’s bid said last week that he would pay $1 in exchange for absorbing Newsweek’s considerable financial liabilities.

Newsweek has struggled through the recession more than most weekly news magazines, losing nearly $30 million last year alone. It was earning that much a year as recently as 2007.

And the longer it remained on the market, the less tenable its financial situation became. It has been an expensive product for the Post Company to produce, with its various international editions and separate back-office positions that were specific to the magazine. Instead of sharing a general counsel and accounting staff with the Post Company, for example, Newsweek has its own employees in those positions.

The magazine’s top editors and managers redesigned it last year in hopes of attracting more readers and advertisers. But the updated magazine, which contained more commentary and analysis on the news of the week, failed to catch on.

What a sale to Mr. Harman would suggest, perhaps more than anything else, is that the right owner for a struggling media property like Newsweek is someone who can afford to lose tens of millions of dollars a year while the magazine tries to find a more successful approach.

News of the imminent deal was first reported by Politico.

In its new owner, Newsweek will most likely have an engaged and active steward. Mr. Harman, who turns 92 this month, appears unwilling and unready to have a quiet retirement. He stepped down as the chief executive of Harman International Industries, which makes JBL and Infinity audio equipment, at age 88. He has continued to teach a business class at the University of Southern California and has said that when he plays golf, he walks all the way through 18 holes, and occasionally more.

He is married to Jane Harman, a congresswoman who represents Southern California. He is also active in the Aspen Institute, a nonprofit, public policy research organization led by Walter Isaacson, the former editor of Time.