Help! Trying to Understand Ref Level and Calibration

Discussion in 'Archived Threads 2001-2004' started by Michael Thompson, Jul 8, 2002.

  1. Michael Thompson

    Michael Thompson Auditioning

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    Hopelly this isn't too dumb of a question, but I'm trying to get a handle on understanding reference level and calibration. I've been reading several different posts on the subject and now I'm wondering if I was making it harder than it actually is.

    Anyway, I need to put it in my own words so I know if I'm actually understanding it correctly...

    From what I'm reading, your so-called "reference level" is actually wherever your volume knob happens to be set when you register a level of 75db on your front speakers using Video Essentials and your handy dandy SPL meter from your main listening position. You then leave the volume knob alone and use the receiver's other settings to tweak the center, surrounds and sub until you get identical readings all the way around.

    Now, let's say your initial volume setting was -34 (again this has nothing to do with the db level of the speaker, it is just the volume setting that allows you to reach the desired db level.) Assuming this is the case, you should not encounter levels above 115db from any one speaker during DVD playback. Obviously, if you use a higher volume setting after calibration, your could get levels higher than 115db due to the increased amplification.

    So, what's the consensus? Do I get it or am I missing the boat somewhere?

    I'm still lost on frequency equalization does anyone know of a good thread or external link that gives some basics on that?

    As always thanks for the help!
     
  2. Bill Kane

    Bill Kane Screenwriter

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    Michael, yeah, you got it right.

    Admin Vince Maskeeper has posted voluminously on this in Basics if you have the time and patience to research, for the theory.

    I'll add: Video Essential at 75dB calibrates for maximum, peak output of 105dB from the mains for DolbyDigital DVD soundtracks, plus 115dB for the LFE booms. Folks using the AVIA disc at 85dB at home achieve the same Dolby peak reference levels.

    I believe it's termed "reference" level because this was developed by Dolby Labs to "reference" the 105/115dB standards of playback in movie theaters.

    As most people say, at home they usually listen at some -10dB below the "reference" volume setting on home amps for more comfortable playback.
     
  3. Michael R Price

    Michael R Price Screenwriter

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    "Assuming this is the case, you should not encounter levels above 115db from any one speaker during DVD playback. Obviously, if you use a higher volume setting after calibration, your could get levels higher than 115db due to the increased amplification. "

    Correct, except that number is 105db for each full range channel and 115db for the LFE.

    Setting the volume control at the point (-34) at which you calibrated to 75db will put you at "reference level." If you watch a movie with the receiver set to -39 you are listening at 5db under reference.

    Equalization is usually used for correcting the effects of a room on the frequency response of a subwoofer... I'm sorry that I don't have any links/resources now, but you may want to try searching for "BFD house curve" or something.

    A short explanation: Room resonances create deviations in your subwoofer's frequency response (meaning that some frequencies will be reproduced louder than others when they shouldn't). These problems can cause "one-note" bass and an otherwise inaccurate reproduction. A device such as the Behringer Feedback Destroyer (BFD) is often used to electronically correct the frequency response.
     
  4. Michael Lomker

    Michael Lomker Stunt Coordinator

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  5. Michael Thompson

    Michael Thompson Auditioning

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    Right, 105 is the correct number for the full range channels, had 115 on the brain! Thanks for the info on the BFD, I'll do some searching.

    Thanks again!
     

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