And the solution for high frequency echoes is easy with acoustic panels anyway. So we have an easy inexpensive and not taking too much space tools for both - the low frequencies (electronic) and high frequencies (acoustic panels, they needn't be as thick as for low frequencies).
Igor, I think you make it sound a little too easy. To tame the modal region, I had to add a number of bass traps in addition to room equalization. And trying to find and eliminate spectral reflections was not exactly easy--it took a lot of measuring and experimenting.