I think by now after reading many review I understand most of those terms that are used when describing sound but I'd like some more precise explanation, not some abstract talk:
Soundstage As I understood it's the feeling of how far something is, sense of space.
Imaging Don't exactly understand,
Depth Didn't get this one totally either.
Separation Separation of what? left and right channel? Don't understand exactly.
Warmth (warm sound) As I understood it's more mid range and bass focused with laid back highs?
So is there exact explanations of those terms? Thanks!
Just to add to the glossaries:
Soundstage : The "space" where the performance is recreated by the system
Imaging : How well the system creates that space above: how wide and how deep (towards the rear) the boundaries are, how each instrument is placed relative to each other, how easy it is to pick out where one sound is coming from, etc
Depth : How far back instruments that are supposed to be towards the rear are, relative to the vocals - for example there are sources/systems where the vocals and the drums are imaged along the same line on the Z-Axis of the 3D environment, which is to say, not really 3D at all
Separation : Separation of each instrument. Some systems can't sort out the rhythm and lead guitar, sometimes even the bass, from each other; or difficult to pick out in a string quartet for example which string instrument is doing what (or where), despite their varying tone and even notes
-----------
Further notes:
1) In a really good system, if you play a properly recorded symphonic performance, you should be able to tell where each section is: strings over there, brass off to one side of it, etc.
2) If your system is too far from neutral, it can cause issues in the imaging as well as the other aspects - eg too much bass response can put the bass drum farther out front (despite some sense of having the drums clearly behind the vocals), while insufficient bass can make the bass drum sound like a snare with a pillow in it; too much treble and on top of glare you can have easily localizable cymbals, which isn't the same as "easy to pick out location" but is more "you hear it right where the speaker is (likely irrespective of where the other percussion isntruments are)." In headphones, that can mean an image where it feels like having the cymbals by your temples, even if the other drums might not be.
3) Number 2 may be caused by any number of factors: headphone/speaker response (none with absolutely perfectly flat response exists yet), amp distortion characteristics if having trouble driving a given headphone/speaker, deliberately "colored" source (analog output section EQs the signal from the DAC)
4) Speaker/headphone location can affect the response and hence imaging as well; that is why some headphones have angled driver mounts or earpads to mimic speaker toe-in angles and also to prevent having them directly over the ear canals. Only in cars do you have the speakers on the flanks and directly pointed at that angle, the solutions to which involve basically doing the same thing, as in competition-quality custom audio systems (no, it's not all about who can blow his windshield off with a subwoofer).
5) Look up technical explanations on Crossfeed, particularly the ones that have illustrations - they will cover the points raised above in detail, as well as the realities with headphone listening.