Dolby PLII from Freeview box via Denon 2805?

Discussion in 'AV Receivers & Amplifiers' started by jchm, Feb 4, 2005.

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  1. jchm

    jchm
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    Help please!

    I have a Humax PVR-8000T connected via Optical to my Denon 2805. Should I be able to use Dolby PLII (or DTS NEO) to get a surround effect from Freeview?

    I am getting nothing from the rear speakers on any of the PLII or DTS-NEO settings.

    Everything is fine when using all other input sources.

    John :confused:
     
  2. Electric Mayhem

    Electric Mayhem
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    As long as the signal is Stereo it should be ok. Doublecheck that the box isn't outputting a Mono signal instead of Stereo (usual giveway is only the centre speaker will be active in PLII mode if there's a Mono signal).
     
  3. jchm

    jchm
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    Jase - thanks for the suggestion - I have checked that and the Freeview box is in Stereo mode - I'm getting fine front channel outputs, but naff-all from the rears! The amp is showing the rears on the panel display, and the test-tone is ouputting from them...I cant figure it out... :rolleyes:
     
  4. Electric Mayhem

    Electric Mayhem
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    Are they absolutely silent or is there any sort of sound coming out of them when you listen right up close??
     
  5. jchm

    jchm
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    If I crank the volume up, there IS sound from the two rears - but really quiet. The auto-setup shows my rears were set to -2.5Db, so I have whacked that up to +2.5 and there is now audible output at my usual listening volumes....
     
  6. Zacabeb

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    With non-surround encoded content, there is very little audible sound from the surround channels in Dolby Pro Logic II Movie mode. There must be quite distinct out-of-phase content to produce sound in the surround channels, and Dolby Pro Logic II seems a bit tailored to avoid "false" surround as much as possible in the Movie mode, whereas the Music mode is intended to do the opposite.

    Optimally, unless the sound was encoded with surround, there should be no audible sound from the surround speakers at the listening position in Movie mode. That's not the reality, but what's aimed for. The decoder also adds about 15ms extra delay to the surround channel to trick the hearing into ignoring audible leakage from the front channels.

    Dolby Pro Logic II also produces quite different results with Dolby Surround or similarly encoded material, and Dolby Pro Logic II encoded material such as video games. Pro Logic II encoding allows for left-right panning of the surround content while maintaining it 180° out-of-phase in the mix, meaning it can be allowed more distinct surround content with 'real' stereo spread. In Dolby Surround, when sounds are panned from the surround channel to the front, the resulting mix will be only partially out-of-phase and a lot of the sound end up in the front channels, even though the decoder does shift the surround content a bit towards the left or right surround channel.

    Dolby Surround also limits surround content to a frequency range of 100Hz-7kHz, making surround content a bit muffled, whereas Dolby Pro Logic II encoding permits 100Hz-20kHz and has clearer surround. When 5.1 Dolby Digital soundtracks are downmixed to Dolby Surround in DVD players, they lack the bandwidth limitations of studio-encoded Dolby Surround and may appear clearer when decoded with Dolby Pro Logic II.

    Although Pro Logic II-specific encoding was not developed until after the decoding process, and the Movie mode decoding optimized for reproduction of existing Dolby Surround encoded material, Pro Logic II encoded sound does improve on Pro Logic II further. It was originally limited to video games, but is now starting to replace Dolby Surround for adapting 5.1 soundtracks to 2-channel stereo in broadcasting.

    So, in a nutshell the lack of surround content is probably a sign of the decoder doing its intended job respectably, and not really a fault.
     
  7. mjcairney

    mjcairney
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    Might sound a bit obvious, but have you used the 2805 set-up menu to configure the correct Optical Input to the particular source? You can most definitely use Dolby PLII, PLIIx or DTS-NEO to get surround from any stereo source.

    Cheers,

    Martin.
     
  8. jchm

    jchm
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    D
    Thanks all for your responses - particulalrly Zacabeb for your rally informative post :thumbsup:

    I guess I was simply expecting too much from PLII with Freeview!

    I'll concentrate on DVD's!


    Cheers
    John
     
  9. Family Guy

    Family Guy
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    Don't forget to put your surround speakers back to the volume they were. Even with DVD, there shouldn't be sound coming from the surround channels ALL of the time.

    The biggest complaint by clients is that they can't hear the surround channels - even after I have calibrated the set up using a sound pressure level metre (I'm not a great lover of auto set ups...). My answer is always "When did you last go to the cinema?". Or "How would it sound if the talking came out of all the speakers...?" I then reassure them how bad it would sound by putting the amp in 5 channel stereo...then playing the opening battle scene from Gladiator in Dolby Digital. The latter always brings a smile...
     

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