Hi all, I have a Mid 2011 iMac (OS X 10.10.1) in my bedroom connected to a 2 TB external HD. I have it go to sleep every night for quick and easy access in the morning. The problem I'm facing is that at seemingly random times in the night (I notice is most in the early morning), I hear the external drive spool up with a "pop" in my sub-woofer (a completely different issue). This started when I upgraded to Yosemite. I just checked my Energy Saver settings and unchecked "Wake for network access." Not sure if that'll do anything because the iMac is not waking up, just accessing the external HD. - My Time Machine is on the external drive.... could that be it? Is there any way to keep OS X from backing up when the iMac is asleep? - There is no Power Nap option.