This project is a cross-site investigation with the university of Oldenburg. 14 participants were measured at both sites in terms of HRTFs and HpTFs at two different positions: at the ear drum using probe tube microphones and at the blocked ear canal entrance using mems microphones. The cross site measurements are used to verify whether measurement uncertainties are origin of a calculated mismatch. Addressing the long known effect of the „missing 6 dB“ a loudness balancing test was performed in 4 different rooms using two different headphone types. While the physical mismatch is investigated here the collaboration partner investigated phase effects of the mismatch.