Rel Subwoofer phase question

I have got brand new speakers that were wired backwards. Yes, it's possible. Don't worry about what things are set at, worry about how they sound. If they sound better out of phase, then run them that way. 

House wiring can be out of phase, the plug can be out of phase, the internal worker can be out of phase. 

Focus on sound, do what sounds good.

Interesting timing on this question for me as I have the same thing going on and it’s got me very confused.  I have the two speakers in identical opposite positions in the room down to just a few millimetres and the subs are in identical positions relative to the speakers.  Even more confusing is if I put one sub at 0 degrees the system sounds best with the other at 180, but if I put the first at 180, the system sounds best with the second at 0.  I’ve double and triple checked everything I can think of down to the wiring on the REL high level connectors and I can’t figure out what is going on.  I will add the room is rectangular but not 100% symmetrical on the walls with windows on one side and not the other and a few other what I thought are minor things going on.  I’d love to have an expert on room modes / acoustics say there is a good reason for this or why it’s happening so I don’t think I’m losing my mind.  

No expert here, but I would say it is the sound waves of one subwoofer interacting with the sound waves of the other subwoofer.  Bass sound waves are very large...easy for them to collide with either a positive or negative way.  Now add this to how the sound waves interact with the room (booming) and adjusting the phase can help augment or nullify these as well.  You are not loosing your mind.

At the most basic level, the phase switch in effect just swaps the two wires feeding the sub. Where the cone was pushing out, it now sucks in.

If you are equidistant between two subs and one is anti-phase to the other, the sounds should exactly cancel at the listening position.  Not what you want.

If you are not equidistant, the exact effect depends on frequency, which affects the wavelengths and hence cancellation / reinforcement of the sounds being played.

At 20-Hz, the cancellation half-wavelength is about 30-feet, dropping to 3-feet at 200-Hz and 18-inches at 400-Hz. So if your speakers are playing a 400-Hz tone and they vary in distance from you by 18-inches you should not hear that tone.