Hifiman - I also have a basement listening room. I love the quiet of being underground. Mine is a walkout, so I do get some outside noise, but I also get natural light and a door to the outside where I can go light some incense. A fair trade. I definitely noticed how the sound image snapped into focus once I got my toe in correct. I’d never toed my previous speakers in as much as these. But it sounds right.
Now I’m working on the room. I just bought a calibrated mic and have been using REW to take measurements. I’ve definitely found the problem frequencies I was hearing. Now that I have some measurements, it’s time to decide on some bass management..
I can’t wait to hear it when it’s fixed. I remember how good everything above 200Hz sounded when I sorted out absorption in that range.
But bass seems more difficult