Exactly what is "reference" level?

Discussion in 'Archived Threads 2001-2004' started by Richard Harvey, Feb 23, 2002.

  1. Richard Harvey

    Richard Harvey Stunt Coordinator

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    I have heard this term for years, and never really thought much about what it really means. So, what exactly is "reference" level?

    In a related (maybe?) question. I just upgraded my receiver to a Denon 2802. Unlike my old Sony STR-DE915, the Denon manual actually tells me what to calibrate my speakers to, so I picked up an SPL and got everything balanced at 75db/C/slow. But, when I adjust volume on the Denon, it is showing me everything as an offset in dB (starting at -55db, I believe).

    Ok, so I assumed that if I balanced to 75db, that '0db' would get me back to 75db, but when I test the levels at the '0db' volume level, I'm actually getting about 94db output. Does this make sense? What does this volume setting dB value actually refer to? And, does this tie back to the "reference" level definition, or do Dolby Labs and dts have their own levels they consider "reference"?

    Rich
     
  2. MichaelGomez

    MichaelGomez Stunt Coordinator

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    Reference level usually refers to movie theaters calibration level of 85 dBs.

    Most of the time the #s on a receiver are just some gimmic that the company makes up. The negative #s would be sound levels that you can't hear and since you can hear them. . .

    Calibrate your system using a test DVD (Video Essentials or Avia) When you have everything calibrated at 75 dBs, look at where your volume knob is. Then just dial to that spot whenever you want to watch a movie.

    Hope that this helps.

    Mike
     
  3. Rick Radford

    Rick Radford Supporting Actor

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    Good question, Rich. A quick search on "reference level" will turn up more than you ever wanted to know!
    Here's a few links to get you started:
    Link 1
    Link 2
    Link 3
    Link 4
     
  4. Ryan L B

    Ryan L B Supporting Actor

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    I always consiter it, when you show of the home theater and the tv, what dvd's will you use to do that. I always use The Matrix or the Fast and the Furious to show them off.
     
  5. Vince Maskeeper

    Vince Maskeeper Producer

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    Dolby defines ref level as 105db of SPL from any single speaker (115db from the sub)-- as measured at the listening position.
    If you get a calibration DVD like Video Essentials or Avia:
    On VE if you use their calibration tones, and set it so that every channel measures 75 on the meter- that is dolby ref level.
    On AVIA if you use their calibration tones, and set it so that every channel measures 85 on the meter- that is dolby ref level.
    It is just the allotted level dolby suggests for playback of their soundtracks. Ref level measures output level. So, that 00 spot on the volume knob is basically just a marketing gimmick-- it doesn't necessarily equate to anything.
    Some receiver put that point in there so you can dial all your speakers with the master volume at that level- making it easier to remember where ref level is. However, as you might guess, higher volume might be needed in a larger room, and less volume might be needed in a smaller room. So when you measure with a meter, your volume knob might end up at 55, maybe at 07, and maybe at that 00 ref point-- but it doesn't matter- the level of output is what matters.
    So, again, ref level is all a measure of OUTPUT. The volume knob has no idea how big your room is, how far you are away, how sensitive your speakers are-- so the only real way to know what ref level is on your system is to get a calibration dvd like Avia or Video Essentials and use their tones.
    -Vince
     
  6. Brian E

    Brian E Screenwriter

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  7. Bruce Hedtke

    Bruce Hedtke Cinematographer

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    Brian, I would assume that the Sound & Vision disc would be comparable to VE or Avia. I would just check and see that it includes a Blue Filter for proper color balancing.

    Bruce
     
  8. Bill Lucas

    Bill Lucas Supporting Actor

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    Vince,
    Dolby defines reference levels as 105db PEAKS with a 115db PEAK from the sub. Not sustained levels of 105db as you post implies. [​IMG] Regards.
     
  9. Cees Alons

    Cees Alons Moderator
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    Cees Alons
    Richard,
    The reason for having a "reference level" is this:
    Our ears are not equally sensitive to different frequencies. Nor dynamically sensitive, meaning that at lower levels you tend to the hear higher and lower frequencies less loud. In older pre-amplifiers they sometimes had a volume dial that was supposed to be somewhat adjusted to this behaviour: physiological volume adjustment. When you turned the volume down, the lower and higher frequencies were less affected, so the over-all sound image stayed the same (to your ears!). Of course, this was dangerous, because you never knew when the frequency response of the amplifier was really straight. Probably only at max-setting!
    That's why they need a reference level: if you listen at that level the whole sound image as produced from the medium is supposed to be the one the creator intended.
    Note that you have no obligation at all to listen to it at that level! You may not want the official level, lest your ears will be damaged enough, over time, to not be able to hear everything anymore at all (just mentioning one good reason [​IMG]).
    You can set another, wanted, reference level for your own taste (probably lower), and use AVIA or the like, to adjust accordingly. Note, that you cannot use an SPL-meter then for comparing the level of different frequencies, but need to use your ears as instrument. Not bad at all, actually [​IMG]. Doing it that way you may be able to perfectly experience the intended sound image at another DB-level!
    Cees
     

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