Audio engineer Joseph Grado, founder of Grado Labs, dies at age 90

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, ...