atom4dATOM amplifiers adopt the most exemplary Korean Class-D performance, reliability, and footprint of the orinal ATOM and iOn platforms. At first glance, you’ll notice several key improvements.Model: AAB-400.4D Atom: Class: D: Number of the channels: 4: Frequency response: 10-20000 Hz: 1 Ohm RMS Power (14.4 V) 430 W x 4: 2 Ohm RMS Power (14.4 V) 265 W