How to send ARC regular tv audio on ERA 300 surrounding speakers?

I can't work out what the Dolby level is on the Sony Bravia 4K GB ATV3 television. In any case, the PCM audio option instead of Audio1 or Audio2 (compressed multichannel sound) greatly reduces the volume of sound emitted by the ARC soundbar.
When I play a Dolby DV, the TV allows surrounding. But the sound of the ERA 300 remains very weak, almost inaudible.
Is there any way of increasing the volume of the ERA 300 independently of the ARC soundbar?

On the other hand, when I want to listen to the radio, the Soundbar and ERA 300 work together. Why can't I have the same thing with terrestrial TV.

well, it seems that depending on the source (terrestrial TV, film recorded on the box, etc.) surround diffusion works, but not as well as I would like in the ERA 300s, the surround adjustment making little difference...
So I'll settle for this...

Too bad, considering the price of these units...

It’s not the speakers that are at fault, from what you’ve posted: it’s your expectations.
 

As we keep telling you, the Eras are rear effects speakers in a DD/Atmos setup. They will sound, for example, when the movie has a plane flying overhead. But for general dialogue the Arc has responsibilities. 
 

I believe you can get programs that are test tones that play to each speaker in turn. Try playing that and see how your setup is. 

you're very probably right, so the best thing is that when I'm listening to TV, which is quite a distance away, I unmute the ERA 300s and switch them from surround to coupled to the ARC.
That's the best way to comfortably hear the TV, isn't it?