My Stereo Sounds Better & Worse At Time... Any Theories Why ?

[1KW]

I have noticed that sometimes I go down to listen and am disappointed with the sound, it is almost like the magic is gone, music almost sounds flat. The imaging is still there but the bass is not how I rememebered it ? Other times I go down and everything sounds wonderful. This occurs without any physical changes to the speakers or system configuration. The other day I went down to listen and again something sounded wrong. I ended up moving my speakers a few inches here and there, leaning forward in my listening chair, sitting back, trying to see if I could capture a better listening level but it was not to be, so I shut everything down and have not been back down for a few days. I am going to give it a try later on today. Anyone else experience this phenomenon ?