Iron filtered neutron spectra were measured for benchmark assemblies of three types: Fe spheres of 30, 50 and 100 cm diameter with a 252 Cf neutron source placed in the center; WWER-1000 reactor pressure vessel mock-up (Fe slab 20 cm); and Fe slabs 67 and 120 cm thick in the reactor beam. Monte Carlo simulations with the MCNP-4c code using different evaluated data libraries ENDF/B-VII.1, BROND-3, JENDL-4.0, JEFF-3.2T2, CENDL-3.1 and TENDL-2012 were performed for spherical assemblies focusing on the neutron energy range of 0.06 to 1.3 MeV. Considerable discrepancies with experimental data were observed for all libraries.