I have opht 1.6.2 (and before that every release from plex i can think of) installed now. I have plex on my intel NUC 5’th generation and a HDMI kable to my Sony 2015 model. The TV does not support any 5.1 and I have to set the TV in night mode to get the center volume to normalize (hear the talking).
I can see in the opht (and I’ve tried this a million times with previous opht and plex official) the audio output settings. No matter what I put in there, the movie/series with 5.1 sound will have their center sound lowered because the TV can’t handle 5.1.
Why can’t I get plex to downsample properly to 2.0 only and have normal volume on my tv? What am I doing wrong here?
I have truggeled with this for years and perhaps I don’t see the solution that is right before me, but please if someone could help me 
Take a look at the attached PDF file: https://forums.plex.tv/discussion/181255/rasplex-guide-to-audio-settings-updated/p1#top
I think the settings shown right on page 1 are appropriate for your use case.
Ok thank you very much for fast reply!
Got it to work now. What is output configuration, stereo upmix and Maintain original volume on downmix do? I tick and try all of those and sound never change.
@cloudstrife78 said:
Got it to work now. What is output configuration, stereo upmix and Maintain original volume on downmix do? I tick and try all of those and sound never change.
This I don’t know. You might be able to find some info about them either in the linked PDF or in the Kodi documentation.
@cloudstrife78 said:
Ok thank you very much for fast reply! 
Got it to work now. What is output configuration, stereo upmix and Maintain original volume on downmix do? I tick and try all of those and sound never change.
See the Kodi Settings page for more information:
http://kodi.wiki/view/Settings/System
Maintain Original Volume on Downmix
Maintains volume level of the original audio source however the dynamic range is compressed.[CR][Disabled] Maintains the dynamic range of the original audio source when downmixed however volume will be lower. Note: Dynamic range is the difference between the quietest and loudest sounds in an audio source. Enable this setting if movie dialogues are barely audible.
Output Configuration
[Fixed] - output properties are set to the specified sampling rate & speaker configuration at all times
[Optimized] - output properties are set at the start of playback and will not change if the properties of the source changes
[Best Match] - output properties are set to always be as close a match to the source properties as possible
Stereo Upmix
Select to enable upmixing of 2 channel audio to the number of audio channels specified by the channel configuration
