PF: Bring the Boys Back Home

Left.

Speakers being wired out of phase would manifest itself by a lack of bass rather than the left and right channels being swapped.

Easy to check. Just swap over the red and black speaker leads on one of your speakers.

I concur left, and that speaker phase would not alter that, only channel swapping at some point in the chain.

Who has told you speakers out of phase, and on what basis? As SJAbbey said, it is easy to check, and the out of phase way round would reduce bass and likely have somewhat muddled imagery. 

Ok cheers, so before I do this - this evening - I do this on just ONE speaker and listen for improved or reduced bass?

(I found out they’re out of phase through my new and cheap AV processor which uses a microphone and beeps to set up speaker levels.)

Out of phase is one speaker reversed in ‘polarity’ compared to the other. So it is just one channel on which to switch the polarity of the cable, the wire currently connected to red or + swapped with the one currently on black or - . You can do it either at the speaker connection, or at the amp end of the speaker cable (just one or the other), and it does not matter on which channel you do it.  

Ideally you would check the connecrions at both ends of both speaker cables to verify that red/+ on the a p is connected to the red/+ speaker wire the other end of which is connected to the red/+ speaker connector, doing that on both cables, and check that the speaker cable plugs have been fitted correctly (the wire from red/+ at one end is indeed connected to red/+ at the other end, as it is not impossible for the cable manufacturer to miss-connect one. But the check you’re doing is quicker and simpler, especially when everything is installed in a rack, and the two wires of each speaker cable indistinguishabe apart from by the plug fitted.

Ok cheers IB!