These series are now improved with special cooling tunnel and optimized protection circuits for more safe and dependable performance. BUILT-IN CROSSOVER IN CX6000PRO & CX4000PRO The CX Series design provides economical access to the premium sound quality of the NX Audio MT Series. Professional power-handling capabilities and exceptional low-end response make this amplifier an ideal choice for installations and touring applications that demand the finest audio quality.Auditoriums, churches, regional tour sound companies and mobile DJs are all ideal candidates for the CX's combination of value and sonic quality. With 4 H-class and One AB-class designs.