More research is needed. I still have a contact at Dolby Labs, and at H/K, so I'll send off an email and see what comes back. I think I read about this in a thread on another forum.
There will be an update. . .
Thanks for taking an interest in this, I’m very curious as to what’s happening so I hope you come up with something.
That could be an indication (if the difference is THAT big), that your sub-woofer might be configured too "hot" to match your mains only.
I was thinking the same thing which is why when I ran my test I reset all crossovers to 80Hz (had my mains set to 60Hz) in both 2ch direct + subwoofer and multi-channel. I also reset all the speakers to the base calibration so nothing was running hot.
To reiterate when I switch between 2ch direct + sub and DPLllx music the overall SPL at the listening position stays the same but the subwoofer‘s output goes up 8-10dB in DPLllx music, in DPLllx cinema there is an overall increase of about 2dB at the listening position. There’s a corresponding drop from the main’s woofers.
I knew there was a reason I exclusively use Neo6.
I Just tested Neo6 and it’s doing the same thing only it’s upping the subwoofer by 10-12 dB vs Dolby’s 8-10 but just like Dolby the overall SPL is staying the same.
