Model number of the two most common varieties of speaker cable connectors by Neutrik. See Speakon Connector for more information.
NL4, from http://www.neutrik.com/fr/en/audio/203_324141/Speakon%C2%AE_Lockable_Loudspeaker_Connector_group.aspx.
NL4, from http://www.neutrik.com/fr/en/audio/203_324141/Speakon%C2%AE_Lockable_Loudspeaker_Connector_group.aspx.