What "Mono Mode" to Use on Onkyo 605?

[Linksys2.4]

I believe this has been covered a long time back in a different thread where a member asked questions about "stereo mono" or something to that effect, and Casual Killer had mentioned "mono is not one channel"...I believe this is incorrect, as normally, DVD (or some Blu-ray) soundtracks are encoded as "1.0" or "2.0" mono (the 2.0 version seems to collapse into the center speaker via PLII processing when a surround system is being used...) and the essence of mono is one channel, even though some "experts" and "purists" claim old theaters would pump out a mono sountrack from ALL speakers in the array...but this is an argument for another day that we can get back to.

My question is regarding a suitable listening mode for playing back mono tracks on my equipment, because I have a great deal of old films in the collection which carry these 1.0 and 2.0 tracks -- right now, I have my Onkyo 605 set, under the listening mode presets (for the DVD input), as follows: Digital Format 2 Channel: PLII MOVIE and Digital Format Mono: MONO MOVIE. The thing is, when a DVD soundtrack carries a "2.0 mono" (or "Big Fat Mono" as its known in the industry), my Pro Logic II circuit kicks in and sends the entire track to the center speaker, as it senses identical information on the "two channel" encoding and drops the sum into the center. Now, with TRUE 1.0 mono soundtracks on discs, the receiver senses this and utilizes Onkyo's "MONO MOVIE" mode (based on what I picked as a listening mode preset) and this is SUPPOSED to drop the signal into the center channel while adding reverb-like effects to the other channels...

The problem is, using MONO MOVIE, I hear nothing coming from any of the other speakers, and the whole soundtrack comes from just the center -- of course, when it's a 2.0 MONO soundtrack, the receiver drops the whole thing into the center, as well. I have been told over the years that the ONLY way to watch an old film and to listen to its mono soundtrack is to let it come from the center position only -- but I'm wondering if there's another mode I should be using for these old mono soundtracks; the Onkyo receivers also have a "MONO" mode which simply puts the track into the two main speakers (which I've tried with 2.0 mono tracks, but it doesn't sound right at all -- there's a weird comb filtering effect from between the speakers) or a FULL MONO mode, which is like ALL CHANNEL STEREO, which forces the sound from all speakers in the system. I've tried this too, but it really sounds odd with dialogue coming from all channels; the soundfield is all screwed up this way. And then there's MONO MOVIE, which is supposed to add "reverb" to the other channels with an old 1.0 track, but the "effect" doesn't seem to work although the main mix stays in the center.

Anyone have any thoughts on the mono debacle? Again, please keep in mind: 2.0 Mono means the SAME signal is encoded in two channels (it's not stereo, and it really SHOULDN'T be coming from the two mains) and when my 605 sees a 2.0 Mono signal, it drops the whole thing into the center channel via Pro Logic II Movie circuitry...is a center-only position the "correct" way to listen to old film soundtracks that carry mono mixes?