The methods described in this article have been developed for studies of fission-neutron spectra. The range of problems that can be solved with their help can be greatly expanded. For example, a 4 π detector similar to the one described here has been used to separate prompt and delayed fission neutrons and (γ, f) and (γ, n) neutrons [10]. Although macroscopic spectrometers are most effective in situations when the energy distribution can be represented in an easily parameterized form, their application is not at all limited to such cases. In the general case, the problem is solved using a group description of the distributions and reduces to a solution of a system of linear equations with experimentally determined left sides $$\hat M_n $$ .