This issue has become apparent to me after upgrading my AVR and TV. The DD source from the X1 is arond 12 to 13 dB too low. This is rather significant as it's over 1/2 drop in preceived volume.
I have an LG B7 connected through ARC to a Denon AVR. The Denon has been room calibrated with Audessey. On the X1 I have DD 5.1 configured in the audio settings. The TV passes through all the internal apps and other HDMI inputs (xbox, HEOS, Blu-ray) at roughly the same volume levels. The X1 sounds weak and hevily compressed in comparison to every other source. The receiver is configured for direct source input and no additional DSP applied.
I can't find any trim level settings or audio compression settings in the X1's setup menu. If I set the X1 to stereo the volume level is around where it should be.