What component is responsible for dynamics ?

Csontos,
Ralph answered your question the same as I have offered before in other threads.
Hifi=the ever present awareness that I'm listening to a stereo system. There's nothing that leads me to believe that the sound is from living people playing instruments, increasing the volume doesn't change this perception(it just becomes louder hifi). In other words, it sounds canned and simply re manufactured.
Realistic=A natural/organic awareness that live musicians are present and this is quite believable and one is able to convincingly established and maintain a emotional connection(thoroughly engaged and drawn into the musical performance). The sense of music from stereo system is much diminished. As Ralph said, it seems other people are in your room, it's very tactile and provokes startle reactions.
Regards,

Oh. I thought Hi-Fi was the highest rating. Thank you.

Hi Csontos,
You asked for my definition and I gave it.You certainty don't have to agree and may have your own interpretation which is fine.I just expressed how I categorize components based on what I hear and the resulting effect and reaction they provoke.
Regards,

In that case I would have to rate my system as 'Hi-Fi' since I am not fooled by it. However having said that, I can't help referring to a statement I made on another thread about a Charles Mingus true direct to disc vinyl recording I have that 'will' fool you. So where is the dividing line between source and gear? It seems potentials are at the center of this issue, no?

Last two posts are not in order. Charles, I truly did think that. I concur with your definition. It's just vernacular.