Information on how to properly connect your speaker with regards to polarity can be found on the rear of the unit by the outputs.

Please note: Output B(Right/Bridge) provides either the right stereo main signal, the main mix signal (Mono) or the bridged mono signal depending on the operating mode selected. In Bridge mode always connect only one loudspeaker with an impedance of at least 8ohms to the output B jack, never use output A in Bridge mode.