Yep! Brain burn-in (or whatever you call it) is real for me too. It's really bizarre stuff, I felt foolish for not immediately noticing better sonic fidelity but I guess it's a completely natural phenomenon.
It would be brilliant to have a proper scientific study in the future, on why our brains need time to adjust and what exactly is happening chemically/emotionally in our heads. But it would probably take a lot of funding and a lot of MRI scans from many people for years to get any kind of meaningful result.
It gets really weird....you mood, energy (tired or not...nothing mystical), health, can make major changes in what you perceive. I've even noticed brain burn in when not listening. Remember your brain does a lot of "offline processing" at night, things are reordered, assimilated to make sense.
Very similar phenomena are why eye witness testimony is very unreliable. I was in the NTSB crash investigation course and we did some tests (most of us were engineers) and it was amazing how our minds manipulated what the eyes and ears took in to create a picture that made sense. Sorry I am going a bit off course....
Brain burn in was so extreme for me that after listening to the X2 for hours over a couple days, I though my pair of RHA MA-750s were actually broken (thought I had handling damage). This can be exceptionally powerful and almost always favors whatever your baseline is. I think it is why many people become company "X" people. Changes are slight, but not wholesale.
X2 was immediately amazing to me...I think because it followed my baseline home system well. To me that is a good sign because I have a many thousand $$ system which has been calibrated, including the bass region. Note that the bass is calibrated about 3dB hot (not exact that would be an average as it is a slope with room gain). When placed right into a room, flat full range speakers have the same rise before cal. If you call flat in a room...sounds dull. X2 sounds like you calibrated in a room, the added the room gain curve back in (standard practice). If you listen to "flat" headphones that do not have this gain back in, the X2 will sound a bit bass bloated or loose until you adjust.
I would argue a bass bump to relfect a normal room gain is most representative of how things are meant to sound. Bass travels further without attenuation, concerts (rock and otherwise) add even more of a boost typically....put the actual instruments in nearly any circumstance outside of (true anechoic chamber) and that is how the sound as well (all in degrees).
I don't think the X2s are perfect, I've stated in other posts that I can notice some grain in the treble when I A/B, with things like cymbal decay presenting slightly artificial. I do find them to be extremely enjoyable and as a complete package at $300, absolutely love them (with no amp required).
