Accuracy of test discs

Discussion in 'Archived Threads 2001-2004' started by Stephen Dodds, Feb 22, 2003.

  1. Stephen Dodds

    Stephen Dodds Second Unit

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    Following on from the Pioneer Bass Management thread, is there a truly accurate test disc.

    I have an AIX DVD-A test disc, and a Telarc SACD test disc, plus the internal tones on the Pioneer and they are all slightly different.

    The Telarc one has the biggest difference, with the LFE tone set so low it is virtually unusable.

    I can drag out my full mic and test equipment, but I would much rather do it with the RS meter.

    Does any have any favourite discs which are accurate?


    Steve
     
  2. Brian L

    Brian L Cinematographer

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    Stephen,

    I assume your thread was triggered by a similar complaint I made in the 45A thread.

    FWIW, I have AVIA, VE, Chesky, Ultimate DVD, Telarc, Delos Surround Spectacular (a CD) and Delos DVD Spectacular. And of course my receiver, an older external DD decoder, and two of my DVD players have their own internal test tones.

    Yes, I have been screwing with this stuff a while, and yes I am a sucker for test discs! No two produce the same results when measured with the venerable RS Analog meter.

    I think some of the difference lies in the fact that the tones themselves do not contain the same group of frequencies. As such, you will tend to get different results from disc to disc, depending on your system and speaker/room interaction.

    There may also be level differences, which I guess could be confirmed with voltage measurement of the pre-amp level outputs.

    I guess the bottom line is that there is no gold standard for this stuff. Pick a disc that you hope is accurate, and stick with it.

    I like the Chesky disc because its got a really good sub phase test, and it is keyed to the exact crossover frequency that you are using. AVIA does it with a broader frequency range to cover a host of possible crossovers.

    I would think that using your exact crossover would be the most accurate, but I would accept that there may be good arguments to the contrary.

    BGL
     
  3. Keith Mickunas

    Keith Mickunas Cinematographer

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    Considering most of these discs tell you to use the Radio Shack meter, it certainly would be nice if they mentioned the error affecting the range of frequencies covered by their tones.

    I found the S&V disc and VE gave me similar enough readings I didn't need to fuss with it. However when I calibrated my sub for DVD-Audio with the Chesky disc I found the sub to be to high. Then again, I'm using the Yamaha S2300 for DVD-Audio and there could be some bass doubling going on with the bass management.
     
  4. Stephen Dodds

    Stephen Dodds Second Unit

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    Yep, I have many of those as well, plus an Infinity Rabos, Stryke Bass, Stereophile and a few others.

    None are the same, even using my TrueRTA and calibrated mic, let alone the RS meter.

    What I would like is pretty simple, full range pink noise in all six channels, plus 20-20 tone burst for each channel.

    The thing that worries me is that I have no idea which is out... the test tones, the decoders or what.

    It can't be too hard.

    Steve
     

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