Hi..
I have a MTX 801D mono amp and my sub is solobaric 12" L7 dual 4 ohm.
I wired the sub into 2 ohm. and on the amp,there are speaker 1 and speaker 2 with + and - sign. and it's mono on the centre of the bottom between the + sign of speaker 2 and - sign of speaker 1.
here is the manual...