Thanks for explanation - but:A guitar speaker cuts at 5 kHz or so, depending on the type, and the sound is then absorbed by the room acoustics, surface etc. That's what your ears hear.
A mic close to the speaker captures the sound of the (same) speaker, which is very brittle, and adds mic coloring, which then is amplified through a FR system, which is typically closer to you than a guitar amp.
So the speaker is the same, but not the techniques.
The Speaker can´t produce higher frequences than maybe 4-5khZ, but they are there ? who produces this frequences ?