Dr Dre and Jimmy Iovine are being sued by Noel Lee, a former business partner who co-designed their Beats headphone range.
Noel Lee, whose firm Monster helped launch Beats by Dr Dre in 2008, says his company was betrayed and its technology “pirated”.
He alleges he “lost millions” after Dr Dre and Jimmy Iovine “improperly took control” of Beats through a “sham” transaction.
After severing ties with Monster, Beats was purchased by Apple for $3 billion.
In legal papers filed in California, Noel Lee alleges rap producer Dr Dre was barely involved in creating the headphones that carried his name.
The range quickly became a highly desirable brand with celebrities and music fans, and Dr Dre’s endorsement was key to its success.
When the company was sold to mobile phone manufacturer HTC in 2012, Dr Dre and Jimmy Iovine made $100 million each, Forbes estimated.
However, Noel Lee claims the deal forced him to cut his share in the company from 5% to 1.25%. He says he then had no other option but to sell his remaining stake for $5.5 million near the end of 2013.
His legal case describes the HTC deal as “fraudulent” and “a sham” intended to shift ownership of Beats to Dr Dre and Jimmy Iovine.
HTC later sold its shares back to the Beats.
Noel Lee says if he’d still had his 1.25% stake, he would have received more than $30 million in the Apple deal.
His original 5% stake would have been worth around $150 million.
A statement from Monster’s law firm Cotchett, Pitre & McCarthy says that Dr Dre and Jimmy Iovine “made millions off the work of Monster and Lee, while the plaintiffs lost millions”.
There’s been no response yet from Dr Dre’s lawyer – or from Beats.
It’s the second lawsuit against the company since Apple bought it last year.
The first was brought by the Bose Corporation over patented technology for cancelling noise in earphones.
That case was settled under undisclosed terms in October.
Dr Dre and Jimmy Iovine are also being sued by David Hyman, who sold his music streaming service MOG to Beats in 2012.
That court case, filed shortly before the Apple deal was sealed, is taking place now in Los Angeles.
Dr Dre has topped Forbes list as the highest paid hip-hop artist, ousting Sean “Diddy” Combs from the top spot.
Dr Dre’s $620 million earnings in the last 12 months are the highest of any musician ever evaluated by Forbes magazine.
His total eclipses the mere $60 million earned by Jay-Z, 44, and Diddy, 44, who tied in second place with earnings from drinks, clothing and television deals.
In fact, Dr Dre’s takings are more than the combined income of all the other 24 names on the list.
Dr Dre has topped Forbes list as the highest paid hip-hop artist
Much of the 49-year-old’s earnings this year came thanks to the $3 billion sale to Apple of the Beats high-end headphone company he founded with music executive Jimmy Iovine and other financial ventures, including cognac and vodka brands.
Drake came in fourth with $33 million which will keep him happy, having told Forbes “if I’m not on your list, I’d be gravely disappointed” in 2013.
Seattle duo Macklemore & Ryan Lewis’s $32 million takes the last slot in the top five, edging out Kanye West’s $30 million.
Birdman’s $24 million, Lil Wayne’s $23 million and the $22 million wealth of Pharrell Williams place them above Eminem who earned an estimated $18 million to complete the top 10.
Nicki Minaj is the only female on the list having taken an estimated $14 million despite her departure from American Idol and lack of tour dates.
To form the list, Forbes considered income from touring, record sales, publishing, merchandise sales, endorsements and other ventures.
A number of Olympic swimmers are walking out to the pool wearing headphones – and keeping them on right up until the last seconds before they climb onto the blocks.
Athletes are said to favor them because they allow them to stay focused on the race in the moments before they take them off to swim and not be distracted by the crowd.
But the practice has divided opinion, with a number of people criticizing the swimmers for ignoring the fans, as the headphones block out their cheers.
Sun Yang, who went on to win a gold medal, was one of several seen wearing the “Beats by Dr. Dre” headphones at the swimming finals on Saturday night.
They are designed to block out all background noise.
A number of Olympic swimmers at London Games are walking out to the pool wearing headphones
US swimming star Michael Phelps – who has 14 Olympic gold medals – keeps his headphones firmly in place until the last minute as he stays focused.
But fans expressed dismay on Twitter, with Ella McSweeney writing: “If I was a fan who travelled to support a swimmer who then appeared with headphones on, I’d feel like being a bit quiet.”
Another wrote: “Why are these swimmers coming out wearing headphones? Take them off and soak up the atmosphere you idiots.”
But they did find some support. Spectator Mari Fotherby told the Independent: “Why shouldn’t they wear them? They train hard 364 days of the year. If they want to use music to stay calm as they get ready to race then they should.”
As well as disappointing the fans, the swimmers who wore the headphones are likely to have left Samsung, the official technology sponsor of the games, somewhat miffed.
Beats by Dre headphones are owned by one of their fiercest corporate rivals, HTC.
Last night a LOCOG spokesperson confirmed that Beats by Dre were not an official sponsor.
“It must be that the athletes just like them,” a spokesman said.
Nobody at the company Beats by Dre was available to comment on whether the headphones had been given to athletes for free.