For many beginner sound technicians, the concept of an audio crossover unit can be confusing. To simplify the concept, think of your Behringer CX3400 as a frequency manager. Its main function is to ensure the right frequencies are coming from the appropriate speakers in your sound system. Without a dedicated crossover unit, your sound system is likely to produce too much of a single frequency.
Place the crossover unit into an empty space in your rack-mount system. Fasten the unit inside the rack-mount with the Phillips screws included with the crossover.
Connect the main power cable to the connector on the back of the CX3400, and to an available receptacle on your surge protector system.
Connect two balanced XLR cables to the main right and left outputs on your mixing console. Run those XLR cables to your crossover unit, and connect the balanced cables to the corresponding right and left input connectors on the back of the crossover.
Connect two balanced XLR cables to the high-input connectors on the back of the CX3400. Run the cables to the inputs on your sound system's power amplifier.