Volume levels vs DB levels

Discussion in 'Speakers & Subwoofers' started by Frank PW, Jan 21, 2005.

  1. Frank PW

    Frank PW Stunt Coordinator

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    I’m not quite sure how to phrase this question.

    I’ve been reading a little about people calibrating their sound systems. People keep referring to the fact that they have their mains calibrated to 10db less then their subs or it’s reading 80db on the SP meter.

    I just took delivery of my HK 635. This is the first AV receiver that I’ve owned that reads a negative number on the display with regards to volume levels. I guess I assumed that this number was based on some kind DB scale. But after reading what people have posted I’m not so sure.

    I have the Avia disk and the HK has an EzSet and EZQ. It directs you to set you volume level to –35db and then it performs a calibration of my speakers accounting for room acoustics and volume levels.

    I’m sure this is just a matter of a particular scale but how do some of you set it up to 80db when my receiver is cranked at –10. I’m confused.

    Don’t get me started on reference levels. I don’t think my walls can handle 105

    Thanks in advance for the lesson.

    F
     
  2. SethH

    SethH Cinematographer

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    Well, I'm not sure how to instruct you with the proprietary calibration products. But using a disc like Avia and a Radio Shack SPL meter, here's basically what you'd do:

    Determine your own "reference" level. If you'll NEVER listen above 95dB, then that could be YOUR reference. Set your receiver to -00dB and use the SPL meter to calibrate it to 95dB. Then, when you adjust your receiver's volume to say -10dB, you're at 85dB (10 less than your reference). Many people calibrate their subs a little hotter because they feel it works better in their system in their room.

    EDIT: I hope this makes sense. I'm sure someone else can come along and explain better than I have.
     
  3. Edward J M

    Edward J M Cinematographer

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    Remember, the Avia test tones are mastered at 20 dB LESS than the actual playback level on a typical movie DVD.

    If you want to calibrate your system to Reference Level, set your Master Volume to 0.0 and adjust all channels until they are reading 85 dB, if you are using Avia. For the subwoofer, try anywhere from 85-87 dB on the meter. Using the 90 scale for the sub calibration will result in less needle fluctuation. 85-87 dB on the meter will result in a 2-4 dB "hot" calibration on the sub.

    Dolby reference level is defined as 105 dB bass peaks from any surround channel, and 115 dB bass peaks from the LFE channel - as measured at the listening position. The reason the LFE channel is higher, is because your DD/DTS pre/pro automatically boosts that channel 10 dB.

    If the surround speakers are set to “small”, the subwoofer is required to handle both redirected bass from the speaker channels and the LFE channel. In the event of simultaneous bass peaks in multiple speaker channels and the LFE channel, the subwoofer would be required to deliver anywhere from a 117-120 dB bass peak at RL as measured at the listening position. Now you can appreciate how demanding RL can truly be on a subwoofer, especially when all speaks are set to small!

    There is one variable on the whole RL concept, and that's the actual DVD mastering level. I wish I could say that setting the Master Volume to 0.0 after RL calibration with Avia or S&V always yielded sound pressure peaks of 105 dB in the surround channels and 115 dB in the LFE channel every time for every Dolby Digital DVD, but it just isn't true. Some DVDs are mastered very hot, and other ones are not.

    Calibrating to Reference Level doesn't mean you have to listen at Reference Level. So ultimately it's best to view RL calibration more as a standardized benchmark for enthusiasts to compare Master Volume settings on playback than to view it as an absolute playback level, because we can't control the mastering level in DVD movies.

    The only way to really be sure you are playing back at true Dolby Reference Level is with an SPL meter at the seat (and correction factors if the meter is C-weighted). Most of the hot bass peaks on DVDs are in the 25-30 Hz region, so I would suggest using an average correction factor of 3-4 dB on C-weighted Fast. If you are hitting bass peaks in the 113-116 dB region on the meter, you are very close to true Reference Level.

    Most subs can’t cleanly hit true RL at the seat, and many enthusiasts find it far too loud for comfortable playback anyway. Personally, I play back most of my DVDs at around 10 clicks under RL (but some as low as -15, and others as high as -5).
     
  4. Frank PW

    Frank PW Stunt Coordinator

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    Wow!! Thanks Edward, you to Seth.

    That clears up some of the muddy water.

    If I set my HK to 0.0 and play the sound levels from Avia I'd have to wear ear plugs. As it is -14 is getting loud.
    The HK tools request that the volume be set at -35 when using it's onboard calibration tool. It’s set to deliver LFE to the mains and the sub. My JBL book instructs me to set my fronts to large to achieve a smoother crossover.
    The speakers that I have are the JBL Reference Series line and can handle just about anything.

    This set up sounds interesting. I'll give it a go.

    Thanks for the lesson.

    F
     
  5. meeks

    meeks Agent

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    I just asked this same question yesterday on the Polk forum. I have the hk230 & was told to start with the FL speaker & have it set at 0, then raise the volume untill I get 75db on my meter & then set the other channels from there. My manual says to have it set at -15 on the dial but when I would do that I would have the channels boosted to around +7 or 8, so Im gonna try it this way.
     

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