In this paper, the performance analysis is carried out for farfield wideband beamformers with microphone mismatches, from the perspective of variance analysis of array response. Some insightful properties on farfield wideband beamformers have been revealed, which are helpful to better understand the robustness of farfield wideband beamformers. The comparative study is performed, regarding the effects of microphone position errors, and of microphone gain and phase errors on farfield wideband beamformers. It is found that the effects of microphone position errors depend on source angle of arrival as well as the temperature in homogeneous environments, while these factors have little impact on the effects of microphone gain and phase errors. Several numerical examples are presented to further confirm the theoretical results.