Comparison between the time-averaged SEDs of the secondary cascade output (pair echo emission, color solid, or dashed lines) and the MAGIC (black dash-dotted lines) and the CTA-North (black dotted lines) sensitivity curves for three different observational times (respectively from left to right: 3 h, 6 h, 9 h). Three different cases have been considered: GRB 190114C, with a redshift of z = 0.42 (upper panel), a scaled GRB 190114C with z = 0.2 (middle panel), and a scaled GRB 190114C with z = 1.0 (bottom panel). The GRB intrinsic (red dotted lines) and observed (red dash-dotted lines) spectra are also shown. Values of the IGMF strengths and maximum energy for primary photons considered are shown in the legend.