The PLMR20PA is a complete marine audio solution. It allows you to pass your amplifier's signal through and act as a crossover network, so you can separate your signal into high and low signals for multiple speaker types. It also includes a balanced microphone input, so you can use your boat's stereo system as a PA system. Adjust the crossover frequency, input gain, and mic input gain using the built-in controls. This unit and cables are waterproof.