Many BEHRINGER power amps and powered mixers utilize NL4 style Speakon outputs, and must have this style connector to operate in Bridge Mode.  The NL4 is differing from the NL2 in that it has four contact points in which the cable can be attached to.  

These contact points on the NL4 connectors are labeled on the connector in various locations, depending on the model of the NL4 connector, and can be difficult to read because the labeling is fairly small.  Sometimes, they are partially obscured by set-screws, but the labeling is as follows:
  • 1+
  • 1-
  • 2+
  • 2-

These are the pin configurations for NLF4P SPEAKON connection on BEHRINGER amps:
  • In mono bridge mode, the SPEAKON pins are always set at 1+/2+.
  • In 2 channel mode, the SPEAKON pins are always set at 1+/1- on both output 1 and output 2.