HI all, I was watching Overlord and noticed that my sub was making a buzzing sound along with the base from the movie. This was about 23 minutes into the movie. I put my ear right to the driver and its definitely coming from the driver. I have the Denon AVR-X3400H and had the master volume at around -12 and the sub was at +3 but it even happens at 0. the gain on the back of the sub was at the 1 o'clock position, so a little past half way. I went to http://onlinetonegenerator.com/ and played a sine wave test tone at 40hz and it also happens to that. I played Star Wars 9 during the scene where Ray fights Kylo Ren at the old death star and it was also making that buzzing sound. I'm playing the movie from a windows 10 machine using Plex. The PC is hooked up to the AVR using an HDMI cable. This is not normal right?