I generally find the sound of most systems I listen to: Lifeless, stifled, subtractive(to what I know to be there), sat-upon dynamically, untrue to the tone of instruments, muddled, congealing individual elements together along with leaving elements out.
The biggest antidote to correcting all of that was to devise a means of isolating my turntable from the support it sat upon. The closer I got to optimising that goal, the more all of those problems faded away. In my system at least, the acoustic impingement in the form of acoustic feedback was not the great problem. Even though the floor in my listening room(my living room) is tile over concrete slab, the problem is what is coming up from the floor. It took me years to figure out just how to optimise it. Wrong turns in experiment were needed to reach correct conclusions. Understanding fundamental principles I had previously unconsidered also helped to consolidate gains. Each step forward was reflected in the lessening of limitations to the sound along with clarification of what was on the record. I could use the recordings as my compass.
The two rock solid sonic guide points I use are dynamics and instrumental tone. All of the things I spoken of have to be across the board with all types of recordings. Not just a handful of select recordings. True progress in system resolution will yield true improvement in all recordings. It will also reveal the difference between recordings to a greater degree. I have seen that improvement across the board does not incur the penalty that the best recordings are compromised. The best is gained from whatever is played, even if the gap between the not so good, the good and the great is better discriminated.
One of the sonic revelations I've become more aware of is the change in tone that a given instrument displays as the instrument is played up and down its frequency range. This is one of the biggest indicators that the playback is moving towards truth rather than a sound tailored toward a preconceived notion of what is correct. An analogy I'd make is: If one had only heard the sound of a grand piano played on its uppermost two octaves alone, one would be surprised at the sound of the entire keyboard and the marked difference that is evident when the entire range of the instrument is utilised. Great recordings and well sorted systems reveal more of this multiple personality trait that wide range instruments display. This is how tone can be utilised to reveal whether truth is being tapped by a system.
Dynamics also are another way in which truth, actual truth to the captured sound, can be assessed. One of the major short-fallings of recorded sound is the inability to present convincing dynamic contrast and within small shifts in dynamics the ability to discriminate dynamic modulation. With deficiency in these areas we lose a lot of the emotional impact and emotional nuance. One of the effects that I've noticed when the fine tuning of my system has garnered real gains, is that detail which was formerly in the apparent sonic forefront of the presentation, now is there in proportion not dominating. Nuanced details that were seemingly swamped by the previously in the apparent sonic forefront detail are able to be detected. This may give the disconcerting feeling that previously apparent detail is less audible, but in the view of the overall picture, much more is now apparent even if some details appear less apparent than previously detected.
I have noticed along with dynamics and tone that bass and stereo soundstage improve. I have concluded however that one has to be very careful when isolating these two elements as indicators of truthfulness. There are many sources of resonance which increase apparent bass. This can lead to a very satisfying effect and provide a pseudo reality-enhancing confabulation. The same can apply to stereo soundstage. There can be a departure from verity which inflates the apparent soundstage. I can't say why it happens, but it can occur without truer tone and truer dynamics. In fact in many of the instances when it does occur, tone differentiation is diminished and dynamic discrimination is also diminished. One should listen for better bass resolution and better soundstage resolution which is always an accompaniment of truer tone and truer dynamics. My feeling is that in the absence of the two faceted truer tonal differentiation/truer dynamic discrimination 'improvements' to bass and soundstage are indicators of increased distortion/resonance. They are departures from truth when they seem better in isolation from truer tonal differentiation coupled with truer dynamic discrimination.