Bass Management in Blu-ray Player
I double checked with Oppo and confirmed that if you set the subwoofer output to Off and the front left and right speakers to Large, the LFE is redirected equally to the front left and right outputs. Similarly, if you set the center-speaker output to Off, the center channel is divided equally between the front left and right speakers, a configuration known as a phantom center. And if you set the surround speakers to Small and the fronts to Large, the low frequencies in the surround channels is redirected to the front left and right.
As for whether or not you can do all these things simultaneously, the answer is a qualified yes. When the center channel is turned off, the back-surround channels are also disabled because of a limitation in the unit's DSP. The side-surround channels can still be active, so turning off the center channel will support a 4.0 or 4.1 speaker layout, but not 6.0 or 6.1. In this case, the back-surround channels are folded into the side-surround channels, so you won't miss anything in the soundtrack.
I'm curious about why you want a 4.0 system with no center speaker. I know several audiophiles who opt for a phantom center when listening to movie soundtracks, but I strongly prefer a real center speaker, which anchors the dialog to the screen much more than a phantom center. A real center speaker also provides better imaging with movies and multichannel music, though some would argue that a horizontal center speaker is inherently compromised and it is therefore better to use a phantom center for music.
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