This paper presents an improved method for characterizing integrated microphone arrays for Device‑Related Transfer Function (DRTF) synthesis. A probe‑array extension of the IMPro technique is introduced to measure all device microphones simultaneously, eliminating unknown timing offsets that arise in asynchronous device–probe recordings. A custom four‑element probe array; modular test jig were developed to evaluate relative inter‑channel propagation delay (RIPD) accuracy across varied microphone‑port geometries. Hybrid free‑field DRTFs were synthesized by combining IMPro data with Boundary Element Method (BEM) acoustic scattering simulations, demonstrating that the probe‑array measurements capture small delay variations essential for precise spatial‑audio modeling. The extended IMPro method offers a practical, scalable alternative to anechoic‑chamber measurements for modern multi‑microphone devices.