Sorry for rambling thenThanks for the thorough answer, but my question was, what does it look like on the waterfall chart There's a lot of ways to set graph borders for display too, besides not knowing what it should look like, idk what range to look at either.
I think the presence region is said to be between 4khz and 6khz, but I don’t know what this is based on. I think everything above 1khz is relevant for the sound stage. I look for timing accuracy, meaning the waterfall chart shows similar attack/decay times over a broad frequency range.
Having a neutral frequency response curve is not very necessary for soundstage. Some headphones (eg Arya) fake soundstage with a double peak in the frequency response at 3khz and 5khz but other than that I think the ear gets used to the frequency response and it’s not that important and more a matter of taste.