DS18 ZR500.1D ZR Class D 1-Channel Monoblock Amplifier 500 Watts RMS @ 1 Ohm DS18’s ZR series of amplifiers are guaranteed to supercharge your sound system to deliver brilliant sound and bulky bass frequencies. The ZR series was designed to pump up the bass and help your speakers reach their maximum potential as a part of your sound system. The ZR500.1D offers a surplus of tuning options: such as Lowpass, and Subsonic frequency adjusters, as well as Gain Knob and Bass Boost Switch Selector to help tune any song to your frequency