Tricky mic position create random response mesure

[B&KMan]

Hi everybody,

After small controverse in regards of position mic for evaluation calibration SPL, I perform for members, a small experience of danger of mic in near field for coherent response and amplitude value.

I put my microphone in near field : exactly same space mic-driver of all 3 mesures but just keep mesure in arroud top edge of driver center of driver and low edge of driver...

Ok if you look pict the change position is really small maybe 2 inch for all 3 position in vertical and no in deep and no in lateral...