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SPL Meter & Me

Discussion in 'Archived Threads 2001-2004' started by Brian Johnson, Jan 6, 2002.

  1. AbelM

    AbelM Second Unit

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    Ok, so I have a question about this. I have Cast Away, so should I use this disc or not to calibrate my speakers? Also when I use Cast Away, do I need an SPL Meter to do this? Or does it do it by it self?
    Please help soon, and THANX!! [​IMG]
     
  2. Brian Bunge

    Brian Bunge Producer

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    Abel,

    I personally would use the test tones in your receiver first. Then use some sort of disc for verification. If there's a big discrepancy then I'd stick with the receiver's test tones.

    Brian
     
  3. RobY

    RobY Auditioning

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    I'm with Mark on this. Educate me, please.
     
  4. Charles L.

    Charles L. Agent

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    I beleive it was 2 db off. I set it to 75 db by my test tones and later checked it with VE and got 77db or something like that. Its been too long ago. My third test was sine waves from MCM Electronics. It looks like my opinion on VE's test tones are in the minority here.
     
  5. ColinM

    ColinM Cinematographer

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    But if each channel is the same level, balanced that is, what's the harm?

    I'm skeptical about the TT generator in my HK, so I use VE.

    I think this may be the most analyzed part of HT.....
     
  6. Brian Johnson

    Brian Johnson Supporting Actor

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    Well. I seem to have a hot little thread going here. I went out & bought VE last night. I may sound like the minority here but I think my reciever test tones were correct(well close enough for me) and the video test patterns were nearly useless(my tv options/setting menu blocks out 1/2 of the screen.) So i think media play is getting this one back. I dont think it was worth the 25 bucks I paid. Am I missing something on the disc. I was expecting more than just test tones in the audio dept. Sure there were some neat demonstrations, but hardly worth its weight. And as I mentioned before the video was difficult to deal with.

    Like I said, am I missing something?

    EDIT:

     
  7. ColinM

    ColinM Cinematographer

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    No, that's about it.

    I hope they take it back for you...
     
  8. Brian Johnson

    Brian Johnson Supporting Actor

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    Me Too [​IMG]
     
  9. Vin

    Vin Supporting Actor

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  10. ColinM

    ColinM Cinematographer

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    Jimmy has speaker set 'X' calibrated at 70db on the meter all around.

    Bobby has the same set, calibrated at 80db on the meter all around.

    Each using the same source chain all the way down to the software.

    Both ok?

    - CM
     
  11. Vin

    Vin Supporting Actor

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  12. Rick Radford

    Rick Radford Supporting Actor

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    I have both VE and Avia and have calibrated with both. I found ~2 dB difference between the 2 reference discs.
    Sometime back, Guy Kuo (of Avia fame) explained to me why that difference exists.. and it made sense.. but I do NOT remember what he told me!
    IAC, 2 dB diff between your receiver's test tones and a reference DVD may not be unusual and may not violate any standards. One reason you may find a difference between calibration with the receiver's test tones vs the DVD is because the DVD signal is coming from the player via the associated interconnects, etc. while the receiver's test tones are internally generated.
    One of the reasons to calibrate is so that you can listen at a volume based on a known reference standard. You may not like to listen at reference level and may prefer 10-15 dB under ref. I like to use 10 dB under ref (when I can get away with it!) and at night we frequently use 15 to 25 dB under ref.
    There was a lengthy thread on HTF sometime back that got into calibration using built-in test tones on the receiver vs a calibration DVD like Avia or VE. I think the thread started out dealing with reference level. Best I recall, there was a camp on both sides and no consensus as to which was correct.
    Here's the thread.
     
  13. ColinM

    ColinM Cinematographer

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    I crank the VE test tone through the left channel, trim at 0db, to 75db on the meter.
    Then I adjust up or down as the tone goes around on each channel.
    Winds up like this -
    L) 0db
    R) -1db
    C) -4db
    SL) -3db
    SR) -3db
    Sub) Flat from 20hz to 75 or so, after correction, set to +3db.
    They all (except the sub) wind up within .5db of each other.
    End of story, enjoy the movie.
    If I am missing something, I don't need it.
    [​IMG]
     
  14. Mark Fitzsimmons

    Mark Fitzsimmons Supporting Actor

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    Hmmm, I may be failing to understand still.

    Reference is 110db right? Does this mean that if I have my reciever set to -10db and I play the tones from Avia, it will come out of my speakers at 75db? However, when I play a DVD on my system with my reciever set to -10db it will play at 110db?

    So the importance of knowing how loud your test tones play is only to know where referance is, right?
     
  15. AbelM

    AbelM Second Unit

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    SO are you saying that Fight Club and Cast Away have the best Optimode? If so, and after you use your own receivers test tones, should I use this Optimode off of Cast Away? Do I need an SPL meter or not fo rthis job??
     
  16. BruceD

    BruceD Screenwriter

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    Actually the whole point of using a known calibrated test tone, like VE's 75dB, is precisely to set the entire HT speaker volume to a known reference standard. Typically these test tones (like VE) are -30dB less (quieter) than full "Reference Volume".
    This means if I play the movie at a volume setting of Zero "0" (typically referred to as "Reference Volume") I will be receiving 105dB SPL levels at my seat from the main speakers (75dB test tone + 30dB) and 115dB at my seat from the LFE bass (75dB test tone + 30dB + 10dB).
    This means I'm listening to what the director intended me to hear exactly the way he intended me to hear it, although I actually may prefer to listen at a lower volume like -10dB or more on my receiver's volume control.
    If you use the test tones and SPL meter to calibrate the speaker's SPL output to something other than 75dB (like 60dB or 80dB), you won't have a common reference point to compare with other people's impressions. Will it actually alter the soundscape, I don't really know, but . . .
    Our ears don't have a linear response to all frequencies, that means when we lower the overall volume we lose more volume in the lower bass frequencies than in the higher frequencies.
     
  17. Kevin C Brown

    Kevin C Brown Producer

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    Yeah, yeah! [​IMG]
    If I don't care what the reference is, and just make sure that all my speakers match at *some* sound level pt, should be OK, right?
    And, in actuality, usually ends up to be middle 70's-ish anyway!
     
  18. Rick Radford

    Rick Radford Supporting Actor

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    Just a minor input on this:
     
  19. Mark Fitzsimmons

    Mark Fitzsimmons Supporting Actor

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    I have the Terminator 2 DVD which has the TXH Optimode test tones, it says on screen they are 75db, but is this right? Should I use these to calibrate my speakers or just use the test tones on the receiver?
     
  20. BruceD

    BruceD Screenwriter

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    Thanks for clarifying that for me Rick.

    I get writing and my head gets ahead of my fingers.
     

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