Irvine-based Incipio LLC’s bid for Skullcandy Inc. was rejected by the audio equipment manufacturer’s board of directors, in favor of a “superior proposal.”

The Skullcandy board accepted Mill Road Capital Management’s $6.05 per share offer—valuing the company at about $174 million. Incipio’s $5.75 per share bid, set to expire Aug 2, included a “go-shop” period until July 23 that enabled Skullcandy to solicit alternative proposals.

Rick Alden founded Skullcandy in 2003 in San Clemente, and moved it to Park City in 2013. It makes headphones, earphones and video gaming products under the Skullcandy and Astro Gaming brands. It had $5.8 million in earnings on $266 million in sales last year.

Skullcandy shares are traded on the Nasdaq and have risen by about 30% to a market value close to $175 million since Incipio in June announced plans to buy the company.

Incipio makes and markets cell phone cases and other mobile device accessories. It sold a minority stake to New York-based private equity investor Goode Partners LLC on undisclosed terms in January.

Chief Executive and Founder Andy Fathollahi at the time described Goode Partners as having “extensive experience in high growth consumer strategies and will be a great asset in helping us carry out our core business objectives, including support in identifying and executing future acquisitions.”