variable bass boost: variable bass boost allows you to adjust the low bass within the boost range to just the way you like it. low-pass crossover: a low-pass filter is an electronic circuit that removes all the notes below the filter's frequency setting. a low-pass filter will primarily keep high notes out of your subwoofer(s). low level inputs: line level inputs, also known as rca inputs or low-level inputs, use rca interconnect cables to link the ac1500.1m with the source unit. most aftermarket radios have multiple pairs of rca outputs that can connect to multiple amplifiers. high level inputs: speaker level inputs are commonly referred to as high-level inputs. this input will be used to connect the ac1500.1m to your factory radio or aftermarket radio that does not have low-level (rca) inputs. power: max power output of 1500 watts at 2 ohms into one channel. maximum power output of 750 watts at 4 ohms into one channel. this amplifier is designed to run your subwoofer(s) giving them the power that they need to perform as they were meant to.