The easiest way to check for phase inversion is to use any of the "Test and Demo" disks out there. If you hear a difference. act upon it. Otherwise you just need to try your system with a certered vocalist and then try it with the phase inverted at the speaker outputs of your amp. Keep the connection that sounds best, but remember that what is best for one source is not always best for another, and for your own sake - trust your own judgement and just enjoy the music!
Regards,
Ray
Regards,
Ray