Legendary audio engineer Joseph Grado died on Friday at age 90. The second-generation Italian immigrant founded Grado Labs — which is now known for its headphones — but when Joseph Grado ran the company it was about one thing: phonograph cartridges.

Grado is credited with inventing the stereo moving-coil cartridge, and he held over 48 patents. To turntable laymen, the cartridge is the "needle" assembly — it's responsible for converting the analog grooves in the vinyl into an electric signal, and is key to the sound quality.

Legendary headphones made on a quiet Brooklyn street

Before entering the high-end audio business, Grado was a watchmaker who worked for Tiffany & Co. In 1953, he started making phono cartridges on the kitchen table, and two years later he took over his father's Brooklyn grocery store and turned it into a factory. That modest three-story building on a quiet street in Sunset Park is still the company's home today — many of its products are handmade under that roof.

While Joseph Grado spent most of his life creating devices that could reproduce music, in 1981 his dream to sing Italian opera on the big stage came true. He performed as a tenor at the prestigious Lincoln Center in New York City, and was quite good at it, according to The New York Times. "There was a grace and delicacy in the quieter moments of Mr. Grado's singing," reads a review from the time, "and an attractive richness when he ventured to sing out."

In the late ‘80s, towards the end of his run at the company, Grado and his nephew, John, produced some of the very first high-end headphones to hit the market. Joseph retired in 1990 when he sold Grado Labs to John Grado. He and his son, Jonathan, run the company today.