Unbalanced interconnects should absolutely not be re-wired to invert polarity. If that were done the signal provided by the sending component would be connected to the circuit ground of the receiving component, and the circuit ground of the sending component would be connected to the signal input of the receiving component. In addition to not working properly that could conceivably even result in damage to the sending component in some cases.
If the interface is balanced in both of the interconnected components, interchanging the connections to pins 2 and 3 of the XLR connector at one end of the cable would do the trick.
HOWEVER, I agree with Stringreen, Stereo5, and Lowrider that all you need to do is to interchange the + and - connections to the speaker terminals, on both speakers. The currents going into and out of the + and - speaker terminals are identical (they have no place else to go!), and so the cable wouldn’t know the difference.
It seems remotely conceivable to me that interchanging wire types between + and - at the amp end might make a slight difference in some circumstances, for example by affecting the characteristics of RFI the cable might pick up and introduce into the feedback loop of the amplifier, if the amp has a feedback loop. But even that seems far-fetched, and in any event I can’t envision a means by which interchanging + and - at the speaker end would affect the behavior of the cables, the speakers, or the amplifier.
Regards,
-- Al
