Surface scattering and diffuse reflections from acoustic diffusers have recently become a significant topic of research for room acoustics. An acoustical goniometer can be implemented to create a circular microphone array to characterize the polar response for various types of diffusers. Particular areas of interest include validating the Physical Theory of Diffraction (PTD) through the use of finite-sized diffusers. In order to properly describe this phenomenon, a microphone array must achieve a fine enough angular resolution in addition to fulfilling the far-field requirements. This talk will discuss the implementation and results of a portable goniometer with a radius of 5 m and an angular resolution of 1.25 deg. This design is intended to be easily deployed in empty, indoor spaces of sufficiently large dimensions for a full 360-deg diffraction response measurement.