Hmm - some kind of summation of reflections + direct sound I will guess. I will try finding that thread.
The timbral difference I hear can be attributed to room interactions. One thing I am yet to try is EQ only under 1K for example
Those interactions, whether our rooms, studios, or any venue and when you remove them in headphones, as you summarized, things don't "seem" right. Sound is reflected and EQing is necessary in our rooms, just usually not above 400hz unless the speaker has a major issue. The room part is easy to address if necessary with higher frequencies, whether materials or toe in, for example.
