Hearing does not need to be subjective and can become objective if you have a standard to go by and a language to convey your preceptions.
One particular high end magazine caters that the standard is an acoustical instrument playing unamplified in an open space and they have worked to put a language in place that allows one to objectively describe what they are hearing. Once you have heared instruments this way you can now use this language to objectively compare what you hear coming from stereo or surround sound. If music and the sound of music is important to you then this become a natural thing to do. Granted that this is not perfect and it takes a bit of training of oneself and ones ears to elimiate bias and external factors (like a change in lighting of the room changing preception) but it is entirely possible and not that hard (though it needs continued dillegence).
Keep in mind that to the common person doing summersaults in gymnastics or doing a layup in basketball would be impossible if they didn't see people doing it. How quickly people tend to sell their ears short and think they can't hear differences or that there can't possibly be a difference amazes to me.
Also, let me add in that the decay in hearing and its effect when it comes to hearing normal voice or instruments is very over rated. Hearing declines at the high extremes of what is felt to be upper range of hearing (20khz but in fact varies quite a bit with asmatics, as one example of a particular population, being shown to easily hear to 30k). Most instruments top out in the 10khz range.