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Using a SPL without a calibration disc...

Discussion in 'Archived Threads 2001-2004' started by Ted Lee, Sep 17, 2001.

  1. Ted Lee

    Ted Lee Lead Actor

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    watch out guys...i just got my spl and now i'm going to flood you all with questions. i guess it'll be easier to post new questions each time...
    unfortunately, i don't have a ve or avia yet. so, after searching prior posts it seems like most people use their spl in conjunction with one of these discs.
    since i don't have one, how does that change what my levels need to be? since both calibration discs use either 75 or 85 db as the calibration point, in order for me to calibrate without it, do i need to go to 105...meaning put the dial at 100 instead of 90, then read +5 on the meter?
    hope that makes sense...
    tia
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  2. Ken Chan

    Ken Chan Producer

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    Many receivers/preamps have internal tones that can be used for calibration; check your manual.
    You will almost certainly NOT calibrate at 105db. That's just too loud. You need a continuous test signal, and you need to know what it's supposed to be (e.g. a -30db signal should be 75db). Even if you were to calibrate against a five-minute drum solo (not that you would, but just as an example), those drums would not be at max volume.
    //Ken
     
  3. Ted Lee

    Ted Lee Lead Actor

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    so, what should my levels be at when not using any sort of calibration disc? i guess that's my basic question.
    i know all about the test tones, calibrating the levels, etc.
    thanks again...
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  4. Jack Gilvey

    Jack Gilvey Producer

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    The basic answer would be: there's no way to know. Unless you know the level of your receiver's internal tones, there's no way to tell if you're calibrated to "reference". That's an advantage of those discs, the levels are known.
    The most important thing, though, and you don't need a disc for this, is to have accurate channel-matching. You should be able to do that just fine with the built-in tones.
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  5. Patrick Sun

    Patrick Sun Studio Mogul

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    Do you have Fight Club on DVD? There's some minor test tones on that DVD (and some of Fox DVDs) that would allow you to set your speaker levels to get them all balanced now that you own a SPL meter.
     
  6. Guy Kuo

    Guy Kuo Supporting Actor

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    Just don't use Fight Club for calibrating your video.
     
  7. Ted Lee

    Ted Lee Lead Actor

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    thanks for the info guys.
    i don't have the fight club dvd (yet) but i do have t2-ue. i know it has the thx optimode. would that work?
    i do intend to get ve soon...i think i can get it from the net for under 20 bucks.
    [​IMG]
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  8. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    I have compared the Optimode found on Toy Story 2 to Avia and found the following:
    Optimode is recorded at 85dB (Reference -20dB) just like Avia.
    After calibrating with Optimode, Avia showed that the surround right and left speakers were running 1 1/2 to 2dB hot (too loud). The Optimode surround signals must not have been recorded correctly. All other channels were within 1dB of Avia.
    So if you use Optimode from TS2, do as you would with Avia (calibrate at 85dB) and when you're done just turn down the surrounds 2dB. I have no idea if Optimode is consistent between movies (T2 vs. Toy Story 2).
     
  9. Ted Lee

    Ted Lee Lead Actor

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    thanks all! [​IMG]
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  10. Vin

    Vin Supporting Actor

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    Ted, I've used Optimode from Fight Club to calibrate my system with the RS meter. Upon doing so I found that the test tones from my receiver (Kenwood VR-507) that I had used previously were not accurate.....I believe this has been this case with receivers from other manufacturers as well.
     
  11. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    NOTE: The THX Optimode test tones are specific to the movie in question. In other words, calibrating with the T2:UE disc will NOT put each speaker at the proper level for all movies... just T2:UE. THX Optimode is meant to calibrate your system to make it compliant with the sound mix and video for that particular movie, not to set overall reference levels.
    However, you can get pretty close with these tests until you can get either VE or AVIA.
     
  12. Jack Gilvey

    Jack Gilvey Producer

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  13. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    Jack, calibration isn't supposed to be the end-all be-all setting for your speakers. Different movies have different mixes, which may require you to manually adjust levels for particular movies (or the dreaded PERSONAL PREFERENCE). Discs like Avia and VE calibrate so that all speakers are at equal levels, which is usually good for most any movie you throw in. The THX Optimode tones initially came under fire for exactly what we're discussing here, since each one is matched to the mix on the disc (as are the video tests to each particular transfer). Optimode is to bring out the best presentation of THAT particular movie, not as a general purpose system calibration.
    That being said, most of the newer discs with THX Optimode have roughly the same levels and come closer to general purpose calibration. T2:UE, however, is specific to the 5.1 mix on that disc. Personally, I calibrated with Avia and haven't had much need to tinker with my levels since.
     
  14. Jack Gilvey

    Jack Gilvey Producer

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    I never knew that about Optimode, thanks Jeremy.
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