Dialog clarity comes up all the time, it seems. The points about center channel placement and acoustic treatment are good, as are the tips on dynamic volume and trim level adjustments.
Some additional thoughts:
- Be alert to any obstructions like chairs, tables, ottomans between the center channel and where you sit. Try moving them to see if it helps.
- The Dolby web site offers guidance on where all speakers should be located, and that can be important. For example, if the L/R channels too close to the center, they can overwhelm the center channel dialog.
- Center channel quality is crucial. If dialog isn't easy to hear and understand when other speakers are idle, well, that's not good. Start with checking the configuration settings, position, etc. But at the end of the day, it could mean the center you have isn't good enough for your needs.
- Source audio quality is all over the map. The best I've heard are some 4k blu rays which can sound great. Other times, not so much. The same is true for other disks, streamed content, cable / sat, and over-the-air broadcast TV. There's even variability in dialog clarity for different shows on the same TV channel, or the same show on two different TV channels. Ugh. This is a pretty common issue without a lot of great options.
- There is also the general problem of hearing loss that many people struggle with that complicates dialog clarity issues. (No specific advice here, just something to consider.)
When approaching this problem, IME many small incremental changes can have a huge impact though it can be time consuming. It took months to do all of this in my system. In the end, it was a worthwhile investment of time.
Just one more upgrade and things will be perfect.