era 300 sound lower with streaming tv

Does the TV program you are watching have much audio in the surround channels? 

Many have little or none even when showing as 5.1 or better on the Sonos now-playing screen.

Certainly if they’re set up as surround speakers, there should be no ‘center/voice’ channel to them. You can, in the room settings, turn up the volume for the surrounds, though. 
 

If they’re ‘grouped’ as a separate room, there are different dynamics involved. 

Is DirectV an app or a settop box? Are there any settings in the app or box? What sound format does the Sonos app say you are getting from DirectV?

It’s the streaming service, an app. 

Adjusting the volume on the TV / Music Level doesn’t change the volume of the surrounds. I don’t believe you can group Era 300s on a stand alone basis.

DIrecTV Stream is notorious for having lower volume.  I usually have to lower other apps by 4 notches when I switch to them after watching the DirecTV streaming app.

Did  you really set the Era’s up as surrounds? If so, the volume should work for the surrounds too - provided they get any sound (so 5.1, not 2.0).

Does having the Arc Ultra connected to the TV by Bluetooth rather than HDMI impact the era 300’s performance?