Agreed! I try not to rely on my "acoustic memory" but more on mental notes I made during critical listening. For example, on the brand new beige model I had for a month, I NEVER heard any annoying sibilance, not even on day one, and I played hudreds of different songs on them. Sibilance is something I'm very sensitive to and can't stand. If the beige model exhibited ANY annoying sibilance, I would have noticed it. The new SE's I have definitely have some annoying sibilance that the beige ones didn't. Also, electronic handclaps sound aggressive on the SE's, especially at louder volumes. Speaking of louder volume, the SE's hurt my ears at higher volumes, whereas the beige ones never did. Simply put, these new SE's sound brighter and more aggressive to me, then I ever recall the beige ones sounding. During my entire time with the beige ones, I never complained of any of these issues. To me, they sounded superb. I was in awe of how detailed they sounded while still being so relaxed.
Yesterday I did a short comparison of a couple of other phones I'm trying out right now -- the Q701 and the HE400S -- to the SE's. Both exhibited no annoying sibilance, but both had less bass. When I first compared the beige 598 to these 2 phones, I preferred the neutral/slightly warm tone of the 598 to the Q701's more clean, crisp, analytical, and bass light sound, as well as the HE400S's more natural lifelike midrange, but unimpressive bass and treble. Both those cans sounded brighter to me than the beige 598. Comparing them to the SE, I actually prefer the sound of the other 2 phones, even though bass is lighter. The new SE simply sounds too bright and sibilant compared to the beige 598 I had. I have no doubts about it.
Now, I'm only at about 7 hours of use on the SE, so I'm hoping that break-in fixes these issues. I think the bass has blossomed somewhat during the first few hours. Also when I first started listening to them, I had to turn the volume way up. Now, I find myself turning the volume down. Is this another phenomenon of break-in, that is they open up and play louder given the same power, or is this a mental thing? If I recall, I had to do the same with the beige 598.