I heard the same a couple of weeks ago from my new AVR after room calibration. I adjusted the house curve, and improved it but couldn't get rid of it.
Then I came back to it a couple of days later, and just listened instead of "listening for differences" and the harshness/roughness had gone. Sounds lovely and smooth now. I promise you nothing had changed in the sound, just my perception. But it was a very obvious harshness before.
See also my post in this very thread, for an illustration of how the perception of sound changes while carefully listening for non existent break-in. This post is from more than two years ago - when I had been conned into thinking I had to break in my new speakers.
I sooo wish I had kept all the notes from college days when we did a bunch of experiments including on speaker break-in. Bottom line is it was easily measurable, practically never audible, and generally completed within seconds or minutes with a tail that might last for hours but wasn't worth...
audiosciencereview.com