Calibration question - reaching 85dB

Discussion in 'Archived Threads 2001-2004' started by Hal_J, Feb 21, 2003.

  1. Hal_J

    Hal_J Agent

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    i think this is a pretty basic question... i couldnt reach 85dB using avia test tones with my receiver volume set at -15...

    i just did my first official spl calibration of my setup last night. here are the details:

    - using avia
    - rat shack analog meter, c-weighted, slow response
    - hk avr-520
    - paradigm focus mains with cc-270 matched center
    - bose something or others as rears. (im frugal right now)
    - HTPC as source. soundblaster audigy mp3 card for audio. passing spdif from dvd player through sound card to receiver.
    - no sub (dls coming next week...)
    - room is 10x12

    so i set all the levels of the channels to 0dB, then set the main receiver volume to -15dB. then i play the test tone. i got something like 72dB. i figured with this receiver, these speakers, and this small room i would not have issues reaching reference levels. someone weigh in?

    what i did: i dont watch movies at reference level anyway, so what i did was set all speakers to 0 dB, play the test tone from the left front, and increase the main volume till i got 75dB. that was about -13 or -12dB on the receiver. then i rotated the test tone through the channels, increased 1dB here, decreased 2dB there, and whammo spiffo, it's fantastic.

    just to be clear - i consider it spl calibrated, and i think it sounds great. im not pissed and im not planning to write angry letters to mr. kardon. [​IMG] but i am really curious as to why i didnt reach the higher levels...

    any ideas?

    thanks,

    Hal
     
  2. ColinM

    ColinM Cinematographer

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    Crank the HK to -0db and use the channel trims to acheive 85db on the meter.

    My AVR110 is set up as -0db = reference, trims are +3, +2, +3, +2, +2.

    Your results will not be the same, probably, but the main vol must be -0, then trim.
     
  3. Hal_J

    Hal_J Agent

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    colin,

    thanks for the reply. i have a question. first, do i really care if i calibrate at 75dB or 85db? is one inherently better than the other? or even 80dB?i ask out of total ignorance.

    thanks,

    Hal
     
  4. ColinM

    ColinM Cinematographer

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    Avia needs 85

    Vid Essentials = 75

    It's the recording level of the tone that determines that. Don't deviate from the instructions...
     
  5. Vince Maskeeper

    Vince Maskeeper Producer

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    Hal,

    I wrote a quick overview of calibration that can be found in the FAQ & primer that covers most of what you asked.

    Understand that the overall measure of the tone isn't nearly as important as getting all the channels even. Hitting 85db on every channel just gives you a "ref" level output- which you probably won't use for normal listening anyway. What is the biggest key is getting even levels across all channels.

    I am a little surprise you tried you calibrate at -15. What gave you the urge to do that? Remember decibels is not a linear scale, rather a logarithmic scale (exponential like the scale used to measure earthquakes).

    Every 6db jump on the decibel scale is a DOUBLING of perceived loudness (so every 6 db drop means a half of "volume" level!). So by running at -15, you were significantly reducing the level!

    As Colin said (and I outlined in the primer), start at 0 on the main, and make adjustments on channel trims.

    -Vince
     
  6. Hal_J

    Hal_J Agent

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    vince/colin,

    perfect. ive scanned the primer and figured i was pretty much on the mark. i know exactly what the issue is: i erroneously thought that the level to set the main volume at was -15dB. the hk 520 has that little auto-calibrate function, and in the manual they recommend setting it to -15dB. so i foolishly assumed that was the 'standard.'

    i have a hunch that when i go home tonight and re-do it at 0dB, im going to be more than fine.

    thanks for the help. vince, thanks for the patient reply since i missed the obvious in the primer. [​IMG] this forum rules.

    Hal
     

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