Any differences between speaker location(s) will enable room to change the outcome [of the comparison]. That’s why multiple speakers on a demo floor are just for visual display.
Setting one speaker on top of the other doesnt work either, as tweeter dispersion differences to your lcoation can alter results. You almost always hearing location differences + speaker differences and it is difficult to tell as a listener whether its location or speaker causing the differences. Replicating the exact location is the only way to compare A to B,
Flawed location may favor one design over another, so this is the other issue. A narrow dispersion vs wide dispersion in highly refelctive environment could favor the narrow dispersion speaker. This could lead one to believe that narrow is better- when that is not true EXCEPT in that one environment. Example is In a normal environment with first reflections controlled, wider is better. So there are a myriad of small technical issues that play a role.
Brad
Lone Mountain