Speaker wire polarity on a powered subwoofer

My Cary SLP 50 B preamp is inverting so I reverse the polarity on my speaker cable. If I run rca line level out from my preamp to the sub I obviously can't access the internal wiring on my powered sub to reverse the polarity. Does it really matter on a sub? What do I do?
Polarity of the sub vs main speakers is important. The output of the sub and the speakers will overlap over a portion of the bass spectrum, and relative polarity of the subs and mains affects the mix. If they are in phase then the outputs add together to produce more bass in the overlap. If they are out-of-phase you get partial cancellation, which can thin out the bass in the overlap.

Try it with the speaker polarity reversed,and normal and see which way sounds better. Sometimes, depending on room, speakers, and placement having the sub and mains out-of-phase sounds better.

Some subs have adjustable polarity to allow for experimentation.

Can you invert polarity of your source? If so just go back to normally wired speakers. BTW its almost 50-50 odds whether a given recording's polarity is normal or inverted, so you might not lose much by reverting to normal wiring anyway.

Note also that some multitracked recordings have inconsitant polarity across tracks so that niether polarity is really correct for the the mixdown (your source).

Thanks so much for the accurate information.