The easiest way to test LFE 10dB boost.
Things you need
247/347 all setup with speakers, display, etc
PS3 (easiest to use - if you have something else that can do it too go ahead)
Video Essentials DVD (the original one - not the DVE).
Set the 247 to bitstream output through HDMI.
Play video essentials DVD. Make sure your 247 is playing plain Dolby Digital 5.1 (turn off all DSP).
Choose the pink noise chapter and just run through all speakers to make sure everything is working properly.
Choose the pink noise chapter and play the subwoofer pink noise test.
Hold the SPL meter from your seated position.
Increase the volume on your receiver so that you can get a good signal on the SPL. May be 75 dB.
Now, keep pressing the rewind button on the PS3 remote so that that chapter does not end - if it ends you have to navigate to it again - big pain!
Now, use the triangle option button on the PS3 to change the AV settings to Linear PCM instead of bitstream. Now the 247 should get PCM 3/2.1 on the front panel.
Check the SPL meter. Does it still read the same level as before when you had the PS3 set to bitstream.
When I tested the 247, the LPCM mode was 10dB lower than the bitstream mode.
With my AVR 745, both are at same levels. The 645 has same levels too.
Hope this helps.
Looks like I was very predictable. I came along with instructions.