I would say that the relative levels of the individual channels and how closely they match one another has absolutely nothing to do with the system's ability to provide flat frequency response. That would be a whole different topic and to measure it you'd need test tones recorded at identical volume throughout the audible frequency range, and an SPL meter to chart the results.
Most combinations of rooms and speakers virtually guarantee that the frequency response arriving at your ears will deviate quite a bit from "flat." Then again, if it actually measured flat (nearly impossible without EQ) it would sound way too bright to those with normal high-frequency hearing ability.
A gradual rolloff in the lower high frequencies (probably with some degree of boost in the upper highs) sounds "natural" to most people. And that's a whole different topic unto itself, as well. :)
Most combinations of rooms and speakers virtually guarantee that the frequency response arriving at your ears will deviate quite a bit from "flat." Then again, if it actually measured flat (nearly impossible without EQ) it would sound way too bright to those with normal high-frequency hearing ability.
A gradual rolloff in the lower high frequencies (probably with some degree of boost in the upper highs) sounds "natural" to most people. And that's a whole different topic unto itself, as well. :)