Official comment
The DJM-500 is unique in that it has reverse hot-cold pins on the master XLR outputs. This was because the DJM-500 was made at a time when Pioneer was selling amplifiers and speakers (from their karaoke days) which featured reverse hot-cold pins on their inputs.
If you want to use any powered speakers, you will need to open the connector on ONE END of the cable swap the hot and cold wires.
Here's the DJM-500 output:
Here's a standard XLR cable:
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