I certainly experience the best sound late at night. However, the problem during the day is often not that my system is too bright but just the opposite--that the system sounds dull and lacking in clarity and "aliveness." This is in fact the biggest "issue" I have in my continuing pursuit of good sound: the balance between brightness and whatever is the opposite of brightness.
When I am seeing live music, say a jazz group, and I leave the room, step out into the hall, I still can tell there is live music happening in the room. But I don't get that sense of aliveness that I get when I'm in the room, and I think the primary difference is a loss of higher-frequency energy, particularly the bite of cymbals. Like when you cover your ears or wear earplugs. You may indeed want it quieter, but you don't want to lose that high frequency energy, which is why conventional earplugs are so unsatisfactory.
I am constantly struggling with this balance in my stereo system,and often the problem is not enough of that energy (sometimes I get too much, too). The cymbals don't sound like I'm in the room, if you will, and without that, it just ain't happening for me. I have tried silver cables, solid state and tubes, PS Audio and Hydra and power cords and the whole nine yards.
And here's the most frustrating thing: I'll get it just right, only to find a week later that it sounds all wrong again. For example, a couple of weeks ago I removed the Hydra PLC from my system and--voila--got the energy back. But now it's gone again, and putting the Hydra back in doesn't hurt at all (it seems to help, in fact). This drives me crazy!
Sorry for angst-ridden post. :-)
Dan