SPL Meter and my sub

Discussion in 'Archived Threads 2001-2004' started by Willem Vos, Feb 19, 2002.

  1. Willem Vos

    Willem Vos Stunt Coordinator

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    I'm trying to calibrate the sound level of my sub, but I'm noticing that the SPL meter isn't giving a consistent reading, even at Slow response. It "jumps" about 2 Decibels back and forth, sometimes even -3 / +3 Db's.

    Is this normal? I'm using test-tones generated by my 3802.

    Also, what would be the best volume setting for the subwoofer output of the denon?
     
  2. TimothyW

    TimothyW Extra

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    This is exactly what I'm seeing with my 2802! I'm interested in finding out the answer for this. It does this on a Velodyne CT-100 and SVS 20-39 using both the receiver test tones and AVIA.
     
  3. Oscar_R

    Oscar_R Second Unit

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    this is hillarious, I calibrated my 2802 about two weeks ago using Avia test tones, and I got the same inconsistancy as well. About a 2+- decibel jump.
     
  4. Willem Vos

    Willem Vos Stunt Coordinator

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    I'm hoping it's hilarious, so when somebody tells us all it's perfectly normal, I can laugh about it in the years to come...
     
  5. DaleR

    DaleR Stunt Coordinator

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    it also happens to me: rs digital sound meter, paradigm ps-1000 sub, video essentials and the room from hell. if it is happening to so many of us its safe to assume that its not uncommon. i just try to set it to the average. that works about as well as anything else.
     
  6. Angelo_Petralba

    Angelo_Petralba Second Unit

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    Having the same problems with my RS Meter...Maybe it's a

    1D10T User error but I can't seem to ge it to read or in my case Register any DB values on the display, only if I ma NEXT TO THE WOOFER will it give me some kind of reading, I thought I was supposd to take the reading on my Listening Position!. It's a digital meter if that helps!

    Any input is greatly appreciated.

    Thanks

    Angelo
     
  7. Oscar_R

    Oscar_R Second Unit

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    I'm using the RS analog model. While we're on the subject, I first started calibrating my speakers using the receivers test tones. I then used Avia and got completely different reesults. Wonder if any other Denon owners have experienced this as well.
     
  8. Bob McElfresh

    Bob McElfresh Producer

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    My best guess would be delayed reflections from the walls are causing the numbers to jump.
     
  9. jason celaya

    jason celaya Stunt Coordinator

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    It is normal from what I've always understood, primaraly because of properties of the room and frequency of the signal. I think you get a flatter response if your sub is in a optimal location in regards to the room. I may be wrong.
     
  10. Alan F

    Alan F Auditioning

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    I got different responses between my Sony's (cheap model) built in tones and Avia. But then, the tones clearly sound different, and the frequency response of my speakers is nowhere near flat (I think living room is the problem, because I just can't believe my Polk center would have a 15db+ spike around 12-14k), so I assume it's because the frequency mix in the pink noise is different. I went with Aiva to calibrate.

    Alan
     
  11. jeff lam

    jeff lam Screenwriter

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    Cmon guys! It will always jump around unless your sub is completely flat in your room. The tones are varried, not just one tone. If it was one frequency, you will not see a variance but since your sub and room have peeks and nulls the needle will jump when it plays a peek and drop when it plays a null(mostly due to room). An ideal set up is to have a sub flat all the way through the frequency range. Which is nearly impossible without equalization.
     
  12. BrianWoerndle

    BrianWoerndle Supporting Actor

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    That is fine. The smallest audiable difference is 3db. The spl meter might be telling you that it is jumping, but you will never be able to tell.
     
  13. John Kotches

    John Kotches Cinematographer

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    All,
    A couple of things when using the Radio Shack SPL Meter.
    1) Set response to slow. This makes the "jumping" of the needle less severe, and gives a more accurate depiction of SPL.
    2) The response of the SPL meter isn't exactly flat, and there are posted correction tables out on the web so that you can correct for its FR anomalies. Basically for subwoofer calibration, set to 2 or 3 dB under the desired result as it is off between 2 and 3 dB from 200Hz on down.
    3) As someone else pointed out (not given attributions here, sorry [​IMG] ) these are pink noise tones, with equal energy distributions across each octave. You see fluctuations/spikes because various room modes are excited over time.
    Brian,
    Research shows that 1dB over the majority of our listening range is the detectable difference in SPL. This varies based on frequencyt, but it is a good rule of thumb.
    Regards,
     

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