We consider the speech enhancement problem in a moving car through a blind source separation BSS scheme involving two sensors. To correct the distortion brought by this structure we have proposed in previous work (Djendi et al., 2007) two frequency-domain methods to compute the post-filters placed at the output of the forward BSS structure (FBSS). In this work, we consider the case where the noises at the sensor inputs contain coherent and non-coherent components. We provide an analysis of the performance (output SNR and the distortion criterion) of the FBSS structure with post-filters as a function of two new parameters: the coherent to diffuse ratio (CDR) andhe speech to coherent ratio (SCR). Simulation results show perfect agreement between theoretical and experimental results.