Just set my speakers with SPL meter, question...

Discussion in 'Archived Threads 2001-2004' started by Michael Cook, Sep 27, 2002.

  1. Michael Cook

    Michael Cook Stunt Coordinator

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    Is the sub supposed to be set the same db as the rest of the speakers, or a little higher? or is it just personal preferance?? I am surprised my ears were pretty far off. Up to 10db on 3 of the speakers.
     
  2. Vince Maskeeper

    Vince Maskeeper Producer

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    Supposed to be dead on, however usually 2-5db goose is normal.

    The issue is that the perception of bass at lower than ref level is skewed. So, you calibrate to a ref level, and then listen 5-10db under that ref level, you will reduce the overall sound by 10db but perceive an even greater loss in bass. To overcome this fact, some guys will goose their sub channel a little high.

    Also, make sure your LFE pad is in the proper position (this will be a control different from the sub speaker level setting). It controls the level of strictly LFE material (where the sub level controls both LFE and bass rerouted from other channels due to bass management). The correct position is all the way up (on the LFE PAD, not the sub speaker level). This will insure the LFE and rerouted bass are at the same level.

    -vince
     
  3. Michael Cook

    Michael Cook Stunt Coordinator

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    Thanks, when using the meter, is there a certain db I should set everything too, or does that really matter as long as all the speakers are equal?
     
  4. Neil Joseph

    Neil Joseph Lead Actor

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    Real Name:
    Neil Joseph
    Check this out if you are using the Radio Shack SLM...
    Radio Shack SPL Meter Correction Values
    The Radio Shack SLM tends to be slightly off at the lower frequencies. The chart is used to compensate for this. Most people I have seen around here run there subs a few dB hot (between 75 and 85). I have mine at 79dB with the speakers calibrated to 75dB. You want to be able to feel the bass but not have it boomy to the point where it becomes un-natural and drowns out the soundtrack.
     
  5. Michael Cook

    Michael Cook Stunt Coordinator

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    I don't quite understand now, sorry. I have the digital meter from Radio Shack. I set it to measure in the 60-80 db range. Then set all speakers to 70db. Should I be keeping the meter in the same spot for all speakers (that is what I did) or should I point it directly at each speaker from where I normall sit??
     
  6. Vince Maskeeper

    Vince Maskeeper Producer

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    The chart Neil has linked to are correction values for specific freq which are useful when generating specific band test tones- but are a bit difficult to incorporate when using filtered pink noise that you get on test discs like Avia and VE.

    I went A/B from a pro RTA to my RS Spl on filtered pink and came up very close.

    -Vince
     
  7. Michael Cook

    Michael Cook Stunt Coordinator

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    Thanks for you help.
     
  8. Chris Liberti

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    As far as I understand it the sub should be set 10db hotter than the mains. For the Dolby spec the maximum spl for all channels except the LFE is 105db and the maximum SPL for the LFE is 115db. The average sound level for reference should be 85db.
     
  9. Bill Kane

    Bill Kane Screenwriter

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    Chris,
    No, the Dolby spec coding automatically provides the extended range of LFE to 115dB. Setting calibration to 85dB AVIA or 75dB Video Essentials locks in this playback.
    When you consider that ordinary low frequency bass from the other speakers is diverted to the Sub -- where the LFE only goes in set SMALL configuration -- the sub can actually see or output 120dB when the receiver volume is set to "reference level." We're talking peak levels here.
    Adding +10dB to the sub during calibration can seriously push some subs to bloooie! at max levels.
     
  10. Vince Maskeeper

    Vince Maskeeper Producer

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    False, and terribly dissappointing that people are still under this impression.
    The proper Dolby decoder will add the 10db necessary in the LFE channel in decoding. The tones on AVIA and VE are specifically "10db down" in lfe-- when the decoder converts the tones, they will all be produced evenly. The Avia and VE tones are specifically designed to output from all 6 channels evenly- so a manual boost of 10 db is not necessary.
    In addition, the "average sound" should NOT be 85 db. The level to calibrate to with tones will vary depending on the encoding levels of the tones (Avia is designed to calibrate their tones to 85, VE designed to measure 75). The average actual output level will vary from disc to disc (I'm not sure where you came up with 85 as an average)-- but I think the median level for dialog according to dolby is -26dbfs, which would be approximately 79 db spl. But, that's a "perfect world" estimate- reality is that it varies.
    -V
     

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