[en] In the framework of cooperation on investigations in the field of fast neutron reactor physics between the USSR and the GDR at the Institute of Physics and Nuclear Power (FEI Obninsk) and the Central Institute of Nuclear Research (ZfK Rossendorf) during the period from 1970 to 1975 spectrometers using proton recoil proportional counters have been created. The spectrometers allow neutron spectra to be measured in fast critical assemblies in the energy range from 2 up to 1200 keV. They were used for measuring neutron spectra in three critical assemblies of the BFS-1 facility in Obninsk. The results obtained with both spectrometers agree well for the energy region above 10 keV. The experimental data are compared with those calculated by standard reactor computational codes using different constants sets