Is stereo an analog of diplopia (vision)?

Yesterday 2 Pleiades linoleum Auratone 5C type monitoring speakers were connected in series in phase.


For the setup, signal path please see yesterday's  posts.


So both were reproducing the same audio signal.


So both speakers were reproducing the singer.


So 2 singers were heard in the room. Or even worse the interference effect of 2 acoustic wave signals originating from different points in space.


No wonder that when only one speaker was connected the sound became natural, realistic, clear, impressive. Both male, female listener agreed. Vicky used the term diplopia.
A Dionna Warwick CD was used for the tests.


Of course stereo can do any things if for example a Blumlein recording is made. But if the vocal is the same on each speaker as is usually the case then one speaker mono should sound better.