SACD/DVD-A Players - LFE Channel Level

Discussion in 'Playback Devices' started by Brian L, Oct 21, 2002.

  1. Brian L

    Brian L Cinematographer

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    If you own a SACD and/or DVD-A player, and use the 5.1 channel analog outputs, I would appreciate if you might take a minute and comment on your experience with the output of the .1 (LFE channel) when balancing your player.
    Some of you perhaps have noted the threads related to LFE channels levels on the Pioneer DV45A and the 47Ai players. That thread can be found here:
    http://www.hometheaterforum.com/htfo...hreadid=100035
    Specifically, the .1 channel level, when balanced with test tones is significantly below that of the main channels, such that some users are unable to dial in the bass level properly. In cases where there is enough gain on the 5.1 inputs or sub amp to get the LFE to match the mains, the system may then be imbalanced with regard to other formats (Pro Logic or Stereo decoded by the Pre/Pro or receiver).,
    There have been other posts here and elsewhere that mentioned other players (Sony and Denon come to mind) that have the same issue. My purpose with this post is to try to get a handle on which players exhibit this behavior, and which do not.
    If you have such a player, please post the model and whether or not the LFE output was below that of the main channels when balanced with Avia, Video Essentials, or other set-up discs.
    Given that other players from other vendors have this issue leads me to think that this is "the way it is", although I have yet to here any kind of explanation as to why there should be a difference.
    Lastly, to really know if the problem exists would require that the analog outputs of the player be measured with a voltmeter. This is very easy to do (assuming you have a voltmeter!), and will remove the rest of the system from the equation.
    Even if you can not take such measurements, I would still be interested in your experience.
    Thanks!
    Brian
     
  2. Jeff Savage

    Jeff Savage Second Unit

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    I don't know if this is what you are looking for but I will post this information anyway.

    I own a Pioneer 47A. When I use VE to calibrate the system using the digital output the subwoofer level on my AVR is at -5dB (about 84dB on the Radio Shack meter yes I like bass and the 3 SVS's can handle the boost no problem). When I use VE and switch over to the 6 Channel Analog output I have to crank the AVR up to +4dB (a difference of +9dB) to get the same output level.

    I don't have and DVD-A or SACD test discs. I would like to try one though. If anyone knows if they exist please let me know.

    Laters,
    Jeff
     
  3. Brian L

    Brian L Cinematographer

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  4. Myki Cantero

    Myki Cantero Stunt Coordinator

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    I have the Pioneer DV-633A and it is the Asian version of the DV-47a but without SACD. I only use my 5.1 analog inputs when I listen to DVD-Audio. So, I tuned speaker levels on the 633A using its built-in test tones, and an SPL meter in my AVR's 7ch mode (analog). After that, I use Avia to tune my levels, in AVR's digital mode, using my AVR's level settings.

    I prefer the Dolby Digital and DTS decoding of my Marantz SR-7200 rather than the DVD player's.

    If I have time, I'll try what you did and report on it. :)

    Myki
     
  5. Espen Braathen

    Espen Braathen Stunt Coordinator

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    My experience is mainly with the Sony SACD/DVD-Video players, but as far as I know the findings are the same for basically all INTERNAL 5.1 decoders regardless of format (i.e. Dolby Digital, DTS, SACD or DVD-Audio):

    Firsdt of all the standard level for the analogue outputs is 2 volt at 0 dBFS (full scale digital signal).

    The +10 dB in band LFE channel gain is missing from internal decoders builtr into DVD-players because this would drive the analogue subwoofer output to approx 6 volts.

    There is also the problem of mixing in the bass from the other channels (if set to small) without overdriving the subwoofer output. So both the LFE channel as well as the bass from the main channels are lowered with approx 5 dB before summation.

    This results in a LFE signal which is -15 dB to low!!!
    Bass from the other channels will be -5 dB to low if the bass management is used. Of course if you actually use the internal bass manager theres no way to adjust both these level errors at the same time baecuase the LFE and main channel bass are mixed together.

    The Denon AVR-5803 aka AVC-A1SR is the only amplifier I know which has a selectable correction for this problem; on this amplifier you can activate a +15 dB gain to the subwoofer input on the multichannel analogue input. This will correct the +15 dB LFE gain problem, and the internal bass manager in the Denon will take care of the rest.


    Espen Braathen
     
  6. Dan Stone

    Dan Stone Stunt Coordinator

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    It is extremely interesting to read the information that Espen has posted, but it leaves me with two questions:

    1) If it's simply a matter of the internal decoder having the bass down by 10 or 15 decibels, then why wouldn't Pioneer say something about this in the manual and why wouldn't they be aware of it when Brian has contacted their tech support department?

    2) If there's danger of overdriving the subwoofer analog output, then how are people getting away with using an Outlaw ICBM to adjust the output levels to the proper amount? Wouldn't that also pose the same risk of overdriving the analog sub output going into the receiver?

    This is all good information and hopefully with everyone working together some insight can be gained and solutions found.
     
  7. Brian L

    Brian L Cinematographer

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    Espen,

    Thanks for you very informative post. In my experience, however, I have made some different observations.

     
  8. Espen Braathen

    Espen Braathen Stunt Coordinator

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    My intial investigation into this subject;
    "bass management in internal decoders"
    was initiated by the fact that a particular SACD disc sounded extremely bass shy while playing connected to the analogue input multichannel input on a recent Pioneer THX Select receiver.

    I made measurements of the LFE/subwoofer output levels using the "Dolby DVD Demo and Test Disc" (not available to consumers) which has all the necessary test signals.

    The finding was that the LFE output was approx 14 to 15 dB to soft compared to the main channels. And that bass from the other channels sendt to the subwoofer output was scaled down by approx 4 to 5 dB before summation.

    I had a private email dscussion with a representative from Dolby which confirmed that this behaviour where per Dolbys own recommendations for bass management in multichannel decoders built into DVD-players.

    In short; this is done to assure that signal at the subwoofer output never exceeds 2 volt when both the LFE and main channels are at peak level.

    I made a further inquire to Sony Europe and got a confirmation from their engineering department which confirmed my findings regarding their DVD-Video/SACD-players.


    PLEASE NOTE: SACD don't actually use the standardized +10 dB LFE gain, however the Sony engineers chosed to lower the SACD LFE output by -10 dB compared to LFE from Dolby Digital/DTS to keep all formats at the same relative LFE level. The end result is the same, however if you buy a pure SACD/CD-player from Sony you will not experience the same problem!


    My own solution when playing SACD discs:
    The bass manager inside the Sony SACD/DVD-Video-player is not used. Instead I use the Denon amplifiers ADC and digital bass management (THX specs) and activate the default +15 dB LFE correction on the analogue 5.1 input.


    In any case I can not recommend anyone to use the internal bass management in a Sony SACD/DVD-Video player i.e. because of these facts:

    X-over is fixed at 120 Hz (way to high).
    High pass slope is -6 dB/octave.
    Low pass slope is -12 dB/ocatev.

    The THX specs require x-over at 80 Hz, with -12 dB and -24 dB slopes.


    Espen Braathen
     
  9. Sach

    Sach Stunt Coordinator

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  10. Sach

    Sach Stunt Coordinator

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  11. Brian L

    Brian L Cinematographer

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  12. TanD

    TanD Stunt Coordinator

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  13. Lewis Besze

    Lewis Besze Producer

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    Interestingly this doesn't "apply" to DVD-A at least in my experience,of course I'm talking about DVD-V/A players only,not SACD/DVD-A players.
    I wonder why,what so "special" about MC SACD,that it leads to this problem?
     
  14. TanD

    TanD Stunt Coordinator

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  15. Lewis Besze

    Lewis Besze Producer

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  16. Espen Braathen

    Espen Braathen Stunt Coordinator

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    "I have a pure SACD/CD player Sony 555ES SACD player, but it has the same problem -10db lower than the other channel."

    Strange.

    Afaik, I have no personal experience with other SACD-players than the Sony SACD/DVD-Video hybrids.


    Espen Braathen
     
  17. Ryan Spaight

    Ryan Spaight Supporting Actor

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  18. LanceJ

    LanceJ Producer

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    Excuse me for butting in here but, why all this sweaty hand-wringing over this? Why not just NOT use the player's decoder if it's causing all these problems???
    A piece of advice, after having some miscommunication with Panasonic over whether or not their DVD-XP50 player had bass management for dvd-audio (it doesn't-damn!):
    MAKE 100% SURE the person you are talking to (phone and e-mail) knows you are talking about bass management for DVD-AUDIO and not Dolby Digital or DTS.
    It took two long phone calls and a series of e-mails to make this clear (the e-mail thing also involved a slight foreign language issue). Dvd-audio, and SACD, are still relatively unknown formats to non-audio/video people but they share much of the same terminology with DD and DTS. That can easily lead to confusion.
    Note to dvd-audio and especially SACD owners: running these signals through any digital-based bass management system has a potential for negatively effecting those player's high quality signals. From an earlier post of mine about this subject:
    "More dvd-audio/SACD weirdness rears its confusing head.........
    If you use PCM-based bass management (from now on: "b.m.") and it's NOT based on 192kHz/24bit chips, then sort-of bad things will happen:
    1) Your dvd-audio's pristine signals will undergo ANOTHER analog-to-digital-to-analog conversion. Nothing earthshaking but this doesn't help signal purity.
    2) If you are running an analog signal derived from a super hi-rez 192/24 bitstream, the b.m. circuitry will convert it to whatever bitstream system IT uses, wiping out any advantage of that finely detailed 192/24-based waveform. I.e., if your receiver uses 96/24 b.m. chips--->you get a 96/24 quality analog signal. Not exactly trash, but not what you paid for either!
    And if you are running an SACD player through those b.m. circuits-oh God, over on AudioAsylum's Hi-Rez forum they would have fainting spells! [​IMG] Even with 192/24-based b.m., most of SACD's advantages (ahem) over PCM would vaporise.
    Outlaw's "ICBM" bass-management gizmo doesn't use any digital circuitry: it's all analog. So it's "safe" to use with any type of player."
    LJ
     
  19. KevinQ

    KevinQ Stunt Coordinator

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    What about the SONY SCD-#775? Does anybody observe the same problem with that player?
     
  20. Ryan Spaight

    Ryan Spaight Supporting Actor

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