Head-Related Transfer Functions (HRTFs) are commonly measured at the blocked ear canal entrance, assuming that the ear canal transfer function is direction-independent. While this assumption holds well at low and mid frequencies, its validity at high frequencies has been questioned. A recent pilot study on a single pair of 3D-printed ear replicas found evidence of directional effects above 9 kHz, but was limited in scope. This study extends that work using 3D-printed ear replicas of ten subjects from the IHA database, mounted on a dummy head. Ear canal transfer functions were measured across a full spherical grid of 1944 incidence angles. Results reveal significant directional variability above 6–7 kHz, with standard deviations of 6 –8 dB at resonant frequencies. High measurement repeatability confirms these are genuine directional effects rather than measurement artifacts. The directional behavior is consistently observed across all subjects and appears linked to the second and higher ear canal resonances. These findings suggest that the current state of the art blocked-canal HRTF measurements may omit spatially relevant spectral information above 7 kHz.
