Same as Fig. 5 (with logarithmic x-axis here), but showing the results for other varying assumptions (blue lines): (a) the mass threshold for failed SN collapsing onto black holes M_max, ccSN (Models 52, 53, 54 and 29), (b) the wind mass loss efficiency η (Models 25, 26 and 51), (c) the minimum mass for SN, M_max, ccSN (Models 30 and 31) and (d) the slope of IMF α_IMF (Models 32 to 34). These physical parameters influence the whole population, both single stars and in binary systems. The list of values depicted in the upper left corner shows a sequence of the varying distributions (blue lines) spanning from top left to bottom right of each panel.