This contribution presents a novel approach for coherence-based signal enhancement. An estimator for the coherent-to-diffuse ratio (CDR) is devised, which exploits the concept of generalized magnitude coherence and thus, unlike common state-of-the-art schemes, can simultaneously take advantage of more than two microphones. Moreover, the speech enhancement by CDR-based spectral weighting is not performed as a post-filtering step, but by enhancing the most appropriate microphone signal. This signal is implicitly determined as part of the CDR estimation such that the presented technique does not depend on an estimation of the direction-of-arrival (DOA) or similar side-information about the desired source. The application of the new approach to binaural hearings aids shows that it achieves a consistently better speech enhancement performance than comparable state-of-the-art approaches.