Sennheiser HD 660S2: audiophile favorites get improved bass response Posted on February 7, 2023 By Charlielikes Sennheiser’s audiophile open-back HD 600-series lineup has a new flagship, which promises better bass and a smoother overall sound. Tech Tags:660s2:, audiophile, bass, favorites, get, hd, improved,, response, sennheiser, tech, technology