Avia DVD calibration and the Radio Shack SPL meter?

Discussion in 'Speakers & Subwoofers' started by Lee-c, Nov 6, 2003.

  1. Lee-c

    Lee-c Second Unit

    Joined:
    Sep 2, 2000
    Messages:
    497
    Likes Received:
    0
    Trophy Points:
    110
    I'm going to be getting one of the well-known Radio Shack SPL meters and I have the Avia DVD
    for Dolby Digital reference DVD calibration. I was wondering if someone could please tell me
    what, if any, correction needs to be applied to the dB readings on the SPL meter when
    calibrating the main speakers, as well as the surround speakers when using Avia.

    I know that the SPL meter has a certain insensitivity to bass frequencies, and thus corrections need
    to be applied when calibrating a subwoofer. But we don't have a subwoofer yet, so we'll just be
    dealing with the main speakers and surrounds for now. What frequency are the notes played by Avia
    for Dolby Digital DVD reference level calibration of the mains and surrounds, and is there any
    correction needed to get accurate readings when doing the calibration?

    Also, what settings should the Radio Shack SPL meter be set to when calibrating the main speakers
    and surrounds with Avia to get accurate readings?

    Thanks for any help! [​IMG]
     
  2. GeorgeJM

    GeorgeJM Agent

    Joined:
    Nov 4, 2003
    Messages:
    41
    Likes Received:
    0
    Trophy Points:
    0
    10Hz add 20
    12.5Hz add 16.5
    16Hz add 11.5
    20Hz add 7.5
    25Hz add 5
    31.5Hz add 3
    40Hz add 2.5
    50Hz add 1.5
    63Hz add 1.5
    80Hz add 1.5
    100Hz add 2
     
  3. Lee-c

    Lee-c Second Unit

    Joined:
    Sep 2, 2000
    Messages:
    497
    Likes Received:
    0
    Trophy Points:
    110
    George: Thanks for the info. [​IMG] I take it from your post that at frequencies above 100 Hz the
    Radio Shack SPL meter is more or less accurate and doesn't need any correction factor applied?

    But what frequency does Avia use to calibrate the main speakers and surround speakers (remember,
    no subwoofer in system) to Dolby Digital reference level?

    Also, could someone please tell me the correct settings to activate on the front of the RS SPL meter
    to get proper readings when calibrating just main speakers and surround speakers? Thanks. [​IMG]
     
  4. GeorgeJM

    GeorgeJM Agent

    Joined:
    Nov 4, 2003
    Messages:
    41
    Likes Received:
    0
    Trophy Points:
    0
    C-Weighting, slow, and it doesn't matter if you're doing the subwoofer or surrounds. C-weighting, slow.

    I don't remember what frequency Avia uses for spl calibration, but it uses different frequencies for main/center/surrounds and a sub.

    AFAIK, above 100Hz the RS meter doesn't need correction.
     
  5. Lee-c

    Lee-c Second Unit

    Joined:
    Sep 2, 2000
    Messages:
    497
    Likes Received:
    0
    Trophy Points:
    110
    George, much thanks for the great info.! [​IMG]

    Even though we may not know the exact calibration frequencies used for the mains, surrounds, etc.,
    do you know if the frequencies used for the mains and surrounds are definitely well above 100Hz,
    and thus there is no need for any correction factor to be applied to the SPL meter readings
    when calibrating the mains and surrounds?
     
  6. Zack_R

    Zack_R Stunt Coordinator

    Joined:
    Nov 4, 2002
    Messages:
    220
    Likes Received:
    0
    Trophy Points:
    0
     
  7. Lee-c

    Lee-c Second Unit

    Joined:
    Sep 2, 2000
    Messages:
    497
    Likes Received:
    0
    Trophy Points:
    110
    An update on the compensation chart for the Radio Shack SPL meter. Over at the SVS site they have
    a low frequency compensation chart listed for the RS SPL meter and apparently there is still some
    lack of sensitivity even at 125Hz. So I thought you'd want to know about that. [​IMG]

    Here is the compensation chart from SVS on the Radio Shack SPL meter.

    12Hz add 16.5dB
    16Hz add 11.5dB
    20Hz add 7.5dB
    25Hz add 5dB
    31.5Hz add 3dB
    40Hz add 2.5dB
    50Hz add 1.5dB
    63Hz add 1.5dB
    80Hz add 1.5dB
    100Hz add 2dB
    125Hz add .5dB


    This still leaves the question. Are the calibration frequencies used for the main speakers
    and surround speakers on the Avia DVD above 125 Hz, so that no compensation is needed to correct
    your RS SPL meter readings?

    Anyone know the answer? [​IMG]
     
  8. Geoff L

    Geoff L Screenwriter

    Joined:
    Dec 9, 2000
    Messages:
    1,693
    Likes Received:
    0
    Trophy Points:
    0
    If your reading specific frequency tones with the spl meter, be it warrbel or sine, then you need to use the correction factors from aprx 125Hz down.

    As far a setting channel levels with Avia, no correction needs to be applied when setting the different channel levels.

    Avia explains everything you may want/need to know on the Avia disc itself about speaker/system calibration
    C-weighting, slow response, and set volume to your liking if referance is to loud. Many calibrate at -10 under=75db.

    "85db" per channel if you want to calibrate to "Reference Volume".

    Regards
    Geoff
     
  9. dusty

    dusty Agent

    Joined:
    Jul 11, 2001
    Messages:
    31
    Likes Received:
    0
    Trophy Points:
    0
  10. Lee-c

    Lee-c Second Unit

    Joined:
    Sep 2, 2000
    Messages:
    497
    Likes Received:
    0
    Trophy Points:
    110
    Thanks for the info. [​IMG]

    Ok, I won't apply any corrections to the SPL readings when calibrating my main speakers and surround speakers
    with the Avia DVD.

    My intention is to calibrate to Dolby reference level with the volume control set to 00dB,
    and then just back off the volume to -5, -10, -15 or whatever seems like a reasonable volume
    when actually watching movies.
     
  11. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Lee,

    Typically the test tones used are what we call Pink noise, which is a shaped combination of multiple frequency tones all at once.

    Like Geoff said, when calibrating speakers you do not want to use any RS calibration adjustments. The only deviation to that is maybe on the sub i.e. allowing a 2dB higher reading for the sub.
     
  12. Lee-c

    Lee-c Second Unit

    Joined:
    Sep 2, 2000
    Messages:
    497
    Likes Received:
    0
    Trophy Points:
    110
    Ok, thanks, I'll remember that. [​IMG]
     
  13. Edward J M

    Edward J M Cinematographer

    Joined:
    Sep 22, 2002
    Messages:
    2,031
    Likes Received:
    0
    Trophy Points:
    0
     

Share This Page