Velodyne wiring harness

I have a 10" velodyne that has a cluster of multicoloured, +/- 22gge wires bundled inside a grey jacket coming out of the sub, intended to connect to the servo. I got the sub used and the wires are not terminated into connectors (I don't know if this is normal). I notice that there are seven wires - white, red, orange, green, blue, brown, and black, whereas the servo only has connections for six wires (all but the black). Does anyone know what I should do with the black wire coming from the sub? I have the manual and it says nothing of it. I think maybe there was a factory harness where the black just grounded to the unit. Please help if you can.