We show how the lag–energy spectrum changes with the BH mass in the frequency band Δf_XMM = (0.9−3.6) × 10⁻⁴ Hz, for a few representative M_BH = (1, 2, 5, 10, 20) × M₆, where M₆ = 10⁶ M_⊙. Note that we show the lags in units of R_g/c, so its magnitude in physical units should be multiplied with M_BH. (a) For the SE disk, the profile of the lag–energy spectrum remains almost constant as the M_BH increases all the way up to 2 × 10⁷ M_⊙. (b), (c) For a thin disk, its lag–energy profile changes substantially with M_BH. Also the lag magnitude does not exactly scale linearly with M_BH.