Invert ?

@OP, there's no way to tell except by listening. MWH777's post explains it well. To the extent that it is audible, the effect is likely to be more obvious by playing some simply mic'd recordings .

 You can hear it. Fortunately, when two signals are badly out of phase, it’s easy to hear. When two similar tracks are mixed, they can sound thinner, tinnier, or harsher, indicating that they have a phase problem.

@yogiboy  Thanks. That makes sense. 

To get a baseline of what phase inversion sounds like, push the invert switch on your preamp for any song you are currently playing and listen if you hear a difference.  If you do, you will know what to listen for in inverted tracks.

That invert switch is a nice feature. My gear does not have that so if I wanted to check out the correct phase I would have to reverse the pos and neg on both speakers. I would have to shut off my amp every time and that’s just not worth the inconvenience of doing that!!