Annual headphone sales worldwide in 2014 will nearly reach $10 billion, as consumer's audio experiences are becoming increasingly mobile and personal. Premium headphones ($100+) now account for 90% of the annual revenue growth, suggesting consumers want better sound quality. Yet, the science behind what makes a headphone sound good and how to measure it is poorly understood. This talk summarizes some recent Harman research into the subjective and objective measurement of headphone sound quality. Using controlled, double blind listening test methods, Harman Research developed and tested a new headphone target response against current popular headphones, as well as headphones calibrated to the recommended diffuse and free-field standards. More recently, the new headphone target response was tested against three popular headphones using 238 listeners from four different countries. This allowed measuring the extent to which age, listening experience and culture influences taste in headphone sound quality. The results show that when headphone brand, price, visual appearance, and celebrity endorsement are removed from the test, most listeners agree on which headphones sound best, and this can be predicted based on their acoustical performance.