Astell&Kern Rosie In-Ear Monitors By Jerry Harvey Audio - 8 Drivers per channel, 4th Order Crossover, and Full Metal Housing Custom-made Proprietary Balanced Armature Drivers (6BA per side) Powered by soundrIVe technology : Dual low, Dual Mid and Dual High balanced armature drivers per side Variable bass output, adjustable from cable : user controlled low frequency drivers with the adjustable bass (0 - +15dB). Integrated 4th Order crossover Noise Isolation -26dB