Originally Posted by sdurani
Yes, according to the instruction manual, the 1009 gives you three options when configuring for 9.1: SB/FH, SB/FW and FH/FW. That last option uses in no SB (surround-back) speakers, which means that 6.1 and 7.1 source material will have their 3 or 4 surround channels downmixed to 2 surround channels.
Keep in mind that of the 9 amp channels built into the 1009 we are only using 7, just to power the front soundstage (Heights, Wides, L/C/R). The 2 surround channels will be sent as a line level stereo signal to the second receiver for upmixing into 4 outputs. The second receiver will then power the surround field using 4 of its built in amps.
Ah very good then.
Regarding the bass management scenario:
The HDMI chaining is what caused you the trouble; in Sanjay/Roger's solution the "master" receiver is performing all bass management, and the "slave" receiver is getting a managed signal input. I would set the "slave" receiver's speakers to "large" or otherwise bypass it's management (you don't want it setting a higher xover point and filtering the signal is the point). Essentially you're just using the "slave" as additional amplification, and it has to process a bit as well. It can still apply Pro Logic II to a bass managed signal.
In your HDMI chained solution, both receivers are "peers" and processing the same data. In theory you could calibrate them to work together nicely, but it's probably more trouble than it's worth.
Back to your original question: There isn't anything being "extracted" unless you've got a Dolby EX or DTS-ES soundtrack or downmixing happening. With a 5.1 input, Pro Logic IIx is simply simulating 7.1 playback. It's not the same as a 7.1 input (it isn't the same as a 5.1 output either). The Ls/Rs outputs should be untouched going through the decoder - if there's EX/ES matrix data, it can be acted upon, and if there's discrete data (from DTS-ES or from a 7.1 TrueHD/DTS-HD track) it will be downmixed into Ls/Rs - able to be acted upon as well.
I can't imagine what this would sound like with a mono input...