My iMac is just less than 1 year old. I have ran the diagnostic that came with Apple Care and found no problem. Recently, I notice that the max speaker volume of my iMac decreased after I switch on the machine on for quite some time. If I leave the iMac off a few days, the volume will sort of reset again but it is not as loud as before. I believe this problem has nothing to do will software settings in OSX as I have tried all those settings. Any recommendation, send the iMac back to Apple?