When I adjust the phase, one setting is fractionally louder than the other - it can be registered in the SPL meter as a db or so difference - if the meter is say swaying between 74 and 75, out of phase may keep the reading more in the 74db, in phase it would read consistently more time in the 75db. This could be BS, but the louder phase also appears to me as being more focused. I have digital speakers front and analogue rear.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).