sub reference level

Discussion in 'Speakers & Subwoofers' started by Doug Fogle, Mar 7, 2004.

  1. Doug Fogle

    Doug Fogle Stunt Coordinator

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    Okay,I've got a really stupid question so be kind.What exactly is reference level in terms of dbs?In other words what should I be measuring on my ratshack meter to know I'm playing at reference level on on my system>I know I normally play lower than reference so I wasn't overly concerned but now I'm shopping for a new sub and need to know how my normal listening levels compare to reference to determine how much sub I need.SVS says if I normally play between 6 to 12 db below reference a 20-39pci should be fine,but if I play higher I should go with the pb2isd.So,what exactly is reference level listening?(kudos to svs btw-its their suggestion about the cheaper sub over the pb2-very impressive when a company actually tries to save me money!)
     
  2. Dustin B

    Dustin B Producer

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    Depends.

    With all speakers set to small full reference means the sub needs to be capable of producing peaks of 121dB at the seats. If your speakers are set to large the sub needs to be capable of hitting 115dB at the seats. If you set your speakers to large, also remember your speakers then need to be capable of hitting 105dB at 20hz in order to get full reference levels.


    Said another way Dolby reference levels requires 5 speakers capable of 105dB from 20hz to 20khz at the seats and a sub capable of 115dB from 20hz to 120hz at the seats. Setting your speakers to small off loads the 20hz to your crossover point range from the speakers to the sub, making it's new possible peak level 121dB.

    The likely hood of all five channels and the LFE channel blasting you at the maximum level Dolby defines isn't high, but is possible. Few people have systems that can do Dolby reference level cleanly. A much larger number of people can do reference level with lots of distortion making it sound aweful and most peoples systems will damage themselves if you try and hit full reference.
     
  3. Doug Fogle

    Doug Fogle Stunt Coordinator

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    So,if I'm listening in my normal position and I'm reading between 74-80 dbs,I'm approximately 25-30 dbs below reference level?
     
  4. Dustin B

    Dustin B Producer

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    The numbers I mentioned are peak levels. The only way to know for sure what you system is doing is to get a calibration disc and an SPL meter. I assume from your post you already have the SPL meter.

    Avia's test tones are recorded at 20dB below the maximum value Dolby allows (a signal that is supposed to generate 85dB at the seats). Video Essentials is 30dB below the maximum.

    Level matching all your speakers to 85dB with the Avia disk and using that volume to play a movie is full reference. This will more than likely be way too loud for you. Back it off until you like the level (infact I'd start by calibrating at 75dB instead of 85dB). Then put the test tone back in and see what you are at. Subtract the level you get from 85dB and that's how far below reference you are.
     
  5. Ron Sc

    Ron Sc Agent

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    Well done Dustin[​IMG]
     
  6. Doug Fogle

    Doug Fogle Stunt Coordinator

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    yes,very well done and a million thanks,Your kind,concise response is probably more than my question deserved and very helpful.thanks again
     
  7. CurtisSC

    CurtisSC Screenwriter

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    Dustin....great posting...that is great info for everyone....a great "reference"!
     
  8. Phil Iturralde

    Phil Iturralde Screenwriter

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    Yep - nice summary Dustin!!!


    Depending on your budget, either SVS model will prove to be the best investment you made to complete your HT setup!

    I'm very partial to the SVS 25-31PCi myself and I can't imagine upgrading it based on what I hear & feel (including my neighbor)!!! [​IMG]

    Phil
     
  9. Doug Fogle

    Doug Fogle Stunt Coordinator

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    Wow...I've never had a question or concern addressed better than the replies to this thread.Thanks for all the info.(incidentally,I've found I watch films loud-at about -5 below reference.But mucic is much lower-at about -15 to -20 is a comfortable volume.I'm thinking film level is so high because I'm unconsciosly compensating for the lack of bass output my old sub is putting out,and I'd probably have lower volume with a more potent sub.At least I hope so-I live in a quiet neighborhood!I was a little surpried by how high the volume measured,frankly,and am probably going to tone it down a bit anyways.Wife is happy...
     
  10. Cam McFarland

    Cam McFarland Supporting Actor

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    Man, I made it all the way to the bottom & I dont have
    a clue what I read.......... :b
     
  11. Edward J M

    Edward J M Cinematographer

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    The one variable that hasn't been discussed is the actual mastering level on the DVD itself.

    DVDs are NOT all mastered at the same level. Like the three bears, some are too hot, some are just right, and some are too cool.

    I wish I could say that playing all Dolby Digital DVDs at Master Volume 0.0 after calibrating all channels (including the sub) to 85 dB with Avia will result in 105/115 dB bass peaks, but it's just not true.

    Try playing Underworld or SW-AOTC at RL and you'll see what I mean.

    There should be a strict standard that the mixing engineers must adhere to for DVD mastering levels.
     
  12. CurtisSC

    CurtisSC Screenwriter

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    Understood....those recordings are hot. But regardless of what the master volume is set at on the receiver or pre/pro, if the listening level is brought to 85dB, the 105/115dB should hold true. Right? More of a question than a statement.

    Reference level is what the SPL meter says at the listening position, not what dial says at receiver or pre/pro. That is my thinking.
     
  13. Edward J M

    Edward J M Cinematographer

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    The 85 dB is really just from the -20RL mastering level for Avia and S&V (85 dB + 20 dB = 105 dB for a surround channel). The LFE channel is boosted 10 dB, hence the 115 dB rating for that channel.

    I agree - assuming the sub is calibrated flat, bass peaks in the 115 dB (after c-weighted correction) region on the SPL meter would be about RL, regardless of what the master volume says. That's assuming the bass is mixed at the hottest level that Dolby allows.

    And I'll concur with Dustin - the chances are pretty slim of a simultaneous maximum level bass hit ocurring in all five surround channels and in the LFE channel. If it did happen, that's where you would see the 120+ dB peak.
     

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