Last week I received a new V6 box (replacing TiVo).
The audio level is way low (vs Freeview) via HDMI on my very standard Sony TV.
When I first got a TiVo box (years ago), I had the same problem, but some smart person said change the audio output away from Dolby (as the Dobly level has to be low to allow for its extra dynamic range). That suggestion worked a treat - audio level identical to Freeview.
Now I have resurrected that same issue on the V6, and changing the audio output to PCM makes no difference.
Googling shows many people with the same problem. I suspect all people, but not all know about this or live with it. One of the posts suggests it is about 10dB down (massive), which I think sounds about right.
I feel pretty sure this is a real problem. Can't it be fixed by an "over the network" V6 software update? My TV volume is cranked up really high.