The shares gained 9.6% at one stage, in Copenhagen, valuing the Danish maker of high-end home electronics at about 3.2bn kroner (€429m).
The potential offer is 85 kroner a share, the Berlingske newspaper reported.
B&O’s board considers the bid as too low, Berlingske said, without saying how it obtained the information.
A B&O spokesman declined to comment on the offer value, as did a spokesman representing the suitor in Denmark.
Billionaire Qi Jianhong, the largest shareholder of Chinese luxury-goods distributor, Sparkle Roll Group, is in talks to acquire the Danish company.
Sparkle Roll clarified on Wednesday that it was Qi, not the Hong Kong-traded company itself, making the offer.
New ownership would allow B&O’s management to focus on turning around the company and increase sales, Qi said.
B&O, which makes €7,000-plus TVs, has struggled to win buyers for its products, as prices for flat-screen sets tumble and more people listen to music on smartphones, rather than on home hi-fi systems.
Qi’s private company is negotiating the acquisition of B&O, and none of Sparkle Roll’s directors have been involved in talks to buy the company, Sparkle Roll said.
Bang & Olufsen had said it was in talks to be bought by Sparkle Roll, its Chinese distribution partner.
Qi had incorporated a wholly-owned company, also called Sparkle Roll Group Ltd., in the British Virgin Islands and that is the entity negotiating with B&O, according to the Hong Kong-listed company.
Qi is also the sole owner of Sparkle Roll Holdings Ltd., currently B&O’s third-biggest shareholder, with a 5.6% stake.
A sale of B&O would mark the end of an era for a 91-year-old electronics maker known for its simple, clean, Nordic designs.
As one of the last of the larger makers of hi-fi systems in Europe, the sale would leave behind mainly niche players, like UK-based Naim Audio, and Cambridge Audio.
Ole Andersen, the chairman of B&O, told Berlingske, in 2014, that the company is too small to stay independent and needed to either scale back business areas or seek partners.
Qi was ranked 422nd on Hurun Report’s 2015 Rich List in China, which put his wealth at 8 billion yuan (€1bn).
Sparkle Roll distributes top-end cars, watches, wine and cigars in China, ranging from Bentleys and Bugattis to 100,000-yuan bottles of French wine.
Like others in the luxury industry, Sparkle Roll has been hit by President Xi Jinping’s anti-corruption crackdown.