Dolby Surround vs Dolby Digital 5.1

Discussion in 'Beginners, General Questions' started by Thomas Willard, Nov 3, 2003.

  1. Thomas Willard

    Thomas Willard Stunt Coordinator

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    I gave my nephew my older Radio Shack receiver that is several years old and has the old Dolby Surround (two front and two back speakers, no center channel and no LFE channel). I remember hearing good surround from VHS movies I rented encoded in Dolby.

    Here is the question. I also gave my nephew a DVD player and it is hooked up to the receiver with the regular left and right channel output. When he plays a movie with Dolby Digital 5.1 is there also the old Dolby Analog signal present? Will he hear Dolby Surround or just stereo?
     
  2. ChrisWiggles

    ChrisWiggles Producer

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    It will be transmitted via stereo plugs. One of two things can happen. Many discs have separate tracks, a regular stereo track(usually mixed with pro-logic in mind, and often labeled as such), and also a DD 5.1 track. You, where possible, will want to select the 2-channel mix. If only 5.1 mix is available, your DVD player will downmix it on the fly to two channel, which you then feed to the receiver, and apply prol-logic processing to get matrixed surround, or leave it in plain stereo if you only have 2 speakers (or prefer it that way).

    Hope that explains things, if not I can clarify further.

    Oh and to clarify further, there isn't an inherent difference between stereo and Pro-logic. ANY and ALL stereo sources can have pro-logic, pro logic II, circle surround, neo6, logic 7, or whatever other matrix processing you want applied to them. Sources, like older DVDs, VHS tapes, TV programs, whatever that are labeled expressely "Pro-Logic" or Dolby Surround, etc, are just mixed with this in mind, but are still 100% stereo.

    Well, so I clarified further anyway for you. [​IMG]

    If I made you more confused, then ask and I'll try to clarificate my confusification. [​IMG]
     
  3. John Garcia

    John Garcia Executive Producer

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    In the DVD player's menu there should be an option to select the downmix option for DD. I believe mine has "normal" (I'm guessing Dolby) and "stereo", in which case I would try normal first.
     
  4. Thomas Willard

    Thomas Willard Stunt Coordinator

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    Chris:

    Thanks for the information. I do see that on some DVD's they give you the option of selecting Dolby 5.1 or Dolby 2.0, which I assume is what the old receiver can decode and send to the two rear speakers. However most DVD's don't provide for that option.

    If I understand you correctly, you are telling me that the DVD play will decode the Dolby 5.1 to stereo and feed that to the receiver. I know from experience with my newer receivers that do have pro logic, etc, that the receiver will produce surround from the stereo source. In fact when I play my old tapes and CD's the pro-logic II mix is very impressive.

    However the old receiver does not have pro-logic but only the old analog Dolby. If it does not detect a Dolby signal then it only can play stereo. So the question is do the DVD's without the Dolby 2.0 option listed feed the old analog signal to the receiver which would then go ahead and decode it for four channel surround? I think you are telling me, the answer is no, the older receiver will only produce stereo when feed with such a signal from gthe DVD player.
     
  5. ChrisWiggles

    ChrisWiggles Producer

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    This just means that there are two totally separate tracks on the DVD, one in 5.1, one in stereo. The stereo one is usually mixed with PLI (or II) in mind.

    If there is not a dedicated stereo track on the disc, the DVD player will downmix it to stereo on the fly. You just feed the mix to your receiver, and then apply pro-logic/dolby surround to that. Again, there is not inherent difference between any stereo sources whether labeled pro-logic, or not. Just turn on the processing, and you're good to go.
     
  6. Jeff Gatie

    Jeff Gatie Lead Actor

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  7. John Garcia

    John Garcia Executive Producer

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    PL and PLII will sound better with a Dolby encoded track, but will still simulate surround with varying results with a stereo only track.

    The receiver without PL should still be able to get some form of surround from the stereo inputs.
     
  8. Thomas Willard

    Thomas Willard Stunt Coordinator

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    Gentlemen:

    Again thanks for taking the time to educate me on this topic. From all that I have read it seems to boil down to the fact that the old analog Dolby receivers (prior to the days of PC and PCII, which take a stereo signal and apply digital processing to simulate Dolby 5.0) also take a stereo signal and decode it so that something is fed to the rear surrounds.

    My Radio Shack vintage 1990 has a Dolby level control, which controls output to rear speakers, and two switches marked Dolby and Hall. I know the Hall setting is basically a reverb setting. If I am understanding the thread correctly, ANY stereo signal will receive analog Dolby processing and come out the rear speakers with a volume dependent upon the setting of the level control.

    I always assumed the movie soundtrack had to be recorded in Dolby to be played back in Dolby, just as it must be recorded in Dolby 5.1 or DTS 5.1 to be played back in those modes. And that without such a signal the Dolby output to the rear speakers would be silent. The reason for the Hall setting was to provide output to the rear speakers (if desired) when no Dolby encoded signal was present.
     
  9. ChrisWiggles

    ChrisWiggles Producer

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    John is correct, but just to make quite clear, you can apply pro logic, or pro logic II (or any other processing formate for that matter, neo6, circle surround, etc) to ANY and EVERY stereo track. You will, however, get mixed results, with tracks that are not expressly designed to be used with pro-logic.

    You can use ANY music CD, VHS, DVD, anything with stereo, and apply pro logic to it. The only inherent difference with things that have the pro-logic, or dolby surround label, is they were expressly mixed on a pro-logic setup, so what you get is what is intended. Applying pro-logic to other things, like most other movies is still usually better. For music, that's hard to say. I leave music in 2-channel always, but some people like a little ambience sometimes.
     

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