What is the lowest voltage acceptable ?

I agree 114 should be the minimum, but the other really hot night Con Edison had some outages a couple of miles away from me and my voltage went down to 109 in the evening. I unplugged my system. The next day it went up to 119 and 115 at night . I emailed my provider ( Con Edison )  and am waiting for a reply.

I want to thank everyone for the valuable information. It's cooler today and the power is back to 120 volts. I use a Shunyata Venom PS8 with the plug in power filter, but I'm going to look into a Furman or Tripp Lite unit. 

I’ll also check out the PS Audio unit. 

Thank again.

Thanks again.