Originally Posted by Mungam
thank you very much for your explanation.
My system consists of 2 front and 2 side surround and wired as you suggested. I am happy with surround output (with LFE mixed in), my question for better audio output was just for 2 channel sources. If I understand you right, as long as I have the sub configured as OFF in the audio setup, the fronts volume will be reduced regardless of the setting of the dedicated stereo output (FR/RF - Down Mix) and regardless of the audio source?
I will give it a try with the Sub configured as on and not connected tomorrow.
Again, many thanks for your help. It is great to really know how the Oppo works and why the engineers implemented the things the way they are.
Not quite. The 105 is clever enough to adjust according to the content you are playing at the moment. When playing stereo content using the configuration I outlined above, there is no LFE, there is no possibility of bass steering from the Surrounds into LF/RF, and there is no down-mixing possible. So there will be no down mix attenuation at all.
Turning the Sub ON or OFF would not change that so long as LF/RF are Large and the content being played is 2.0.
When playing 5.1 or 7.1 content, there IS LFE to deal with, there is the potential for bass steering from Small speakers, and there is down-mix happening for Center into LF/RF or Rear Surrounds into Side Surrounds. So down mix attenuation has to happen. With Sub ON the LFE goes out the unconnected Sub jack, and so the LARGEST requirement for down mix attenuation goes away. There is still down mix attenuation (read on), but it is nowhere near as much as would be needed if headroom has to be made in LF/RF to mix in LFE. The 4 speakers will receive down mix attenuation as needed for the down mix itself (Center speaker into LF/RF and Rear Surrounds into Side Surrounds). With Sub OFF the down mix attenuation for all the speakers is increased (they all have to match, since otherwise you'd have to keep adjusting the volume trims all the time) to account for LFE going to LF/RF as well as Small speaker bass steering into LF/RF in addition to the actual, missing speaker down mix already going on.