RCF HD 35-A Powered Speaker. The neodymium compression driver with a titanium dome provides exceptional vocal clarity and sound projection on the On the HD 35-A, the 3.0" voice coil neodymium compression driver with a titanium dome provides exceptional vocal clarity and sound projection. A very linear response and a focused, deep low-frequency control are features of the 15" woofer. The DSP that manages crossover, equalisation, FiRPHASE, soft limiting, and speaker protection controls the 1400 watt amplifier.