Axiom Home Page Forums General Discussion Home Theater Stereo Sound

I need to understand stereo sound. So far I understand that stereo sound is availabe to a pair of speakers driven by a stereo amplifier.
So does this mean that stereo sound will only be available to the two main speakers of lets say a 5.1 system and the other speakers aren't utilised. Will it be the same for other stereo input sources like fm tuners, cassete decks, vcrs... etc.

Not necessarily, clovis. All receivers doing 5.1 or more have one or more processing abilities to take stereo material(all those you mentioned) and extract some information which is then sent to center and surround speakers. Examples are Dolby Pro Logic II(new DPLIIx just out)and Logic7. The result isn't fully equal to 5 or 6 channel recordings, but it's pleasant in many cases. Some prefer not to use it and listen to stereo material only through the 2 main speakers; it's a matter of choice.

Depending on your amp and settings, a 2-channel source played on a 5.1 channel system may "bleed" into the other speakers even if you are not using a 5CH stereo matrix. I have a Denon AVR-1802 and I have observed a small amount of bleeding into the surrounds with stereo sources and Dolby decoding. Switching the input mode to "stereo" stops the bleeding. Quite honestly, the bleeding is so faint that I rarely bother to make the change. Still, forewarned is forearmed!

robdarst,
What mode is your receiver in when you hear this "bleeding"?
-curtis

Hi Curtis,

I have a Denon AVR-1802 and a Pioneer DV-563A as sole transport. Bleeding from a 2-channel source (e.g., CD) into the center and surrounds occurs when the receiver is in "Dolby PLII C" mode, which is the mode the receiver automatically goes to when it detects a digital CD signal. I can stop the bleeding by selecting either "PCM" as the "input mode" or "stereo" as the surround mode.

Up until now, I had assumed this was "normal" (though undesirable) receiver behavior. Has anyone else experienced this phenomenon, or do I have a buggy receiver?

does your receiver have a auto format button or setting that can determine weather its a 2 channel or other recording? or a setting to assign to a pcm mode when it detects a stereo signal without having to switch it manualy?..ron

Rob,

Um? Isn't the "Dolby PLII C" mode that you described, essentially the Dolby ProLogic II? If so, what you've heard from the center and surround channels is not a bleeding, but legitimately matrix-synthesized center and surround sounds.

Rob, as sushi points out, the "bleeding" you describe would appear to be the usual DPLII Cinema processing. The DPLII Music mode is generally suggested for listening to music and you should try it if you haven't already done so to see if you get a more favorable impression of DPLII. If not, then you may simply be one of those who don't care for it and should use the stereo mode.

Also, depending on receivers, the Dolby ProLogic II Music mode allows you to adjust several matrix-decoding parameters, such as the center width (essentially center-channel level) and soundstage depth.

Hi all,

That bleeding is correctly termed "crosstalk." Old-fashioned analog Dolby Pro Logic's separation figures weren't so great--a maximum of about 30 dB of separation between channels--but still a huge improvement over the Dolby Surround matrix, which yielded a maximum of 3 to 6 dB if memory serves.

The separation figures for DPLII are much improved but without consulting my contact at Dolby Labs I'm not sure by how much.

Regards,

Live and learn! Thanks for the information. It's always na relief to find that something unexpected (I've only had my surrounds for a few weeks) is "by design" not "a bug." As for my receiver, sadly, it does not automatically recognize PCM stereo signals sent from the universal player (as opposed to my now-disconnected ancient CD player), but switching to PCM or stereo (or PLII "music" mode) is a simple business.

Hey, sushi, love the totoro avatar. That's one of my family's favorite movies!