Subwoofer Calibration.

Discussion in 'Speakers' started by RyanJE, Jan 11, 2005.

  1. RyanJE

    RyanJE Second Unit

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    I have the DVE disc and I was wondering when calibrating the sub what should I set the gain on, on the actual sub. I know everything should be at zero on the receiver but im not sure about the sub.
     
  2. Cameron Yee

    Cameron Yee Executive Producer
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    I usually set it halfway to start. I would try to set the sub amp as close to calibration level as possible then use the receiver adjustment to fine tune 1-2 dB either way. I figure why stress the receiver more than it needs to when the sub has an amp?
     
  3. RyanJE

    RyanJE Second Unit

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    Do you have someone else read the meter and adjust the sub gain accordingly?
     
  4. John Garcia

    John Garcia Executive Producer

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    About half way is a good rule of thumb, but it will vary based on your room. I start with that as well, then adjust the sub's gain a few times until I have something that is in the ballpark. Once that is done, I use the receiver's adjustments to fine tune with the SPL meter. Should be able to do it all by yourself.
     
  5. Brian L

    Brian L Cinematographer

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    I would stay away from DVE for sub calibration, as there is a known problem with the .1 channel level.

    Here is a link to the master thread on DVE. Search through that thread looking for LFE, and you will find lots to read.

    http://www.hometheaterforum.com/htfo...&highlight=DVE

    BGL
     
  6. ScottCHI

    ScottCHI Screenwriter

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    you run really really fast. i mean real fast.

    [​IMG]
     
  7. Cameron Yee

    Cameron Yee Executive Producer
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    Besides running really fast you can also put the chapter on a loop and walk back and forth [​IMG]
     
  8. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    Ryan,

    Definitely research the DVE issue with bass levels before using it. You can compensate for the problem...but I would just use the built in tones in the receiver/procesor instead. If you can rent/purchase AVIA...that is a very good setup disc.

    Most powered subwoofers calibrate easily with their volume knobs anywhere from 1/4 to 3/4. Using a combination of the subwoofer volume knob and the receiver's bass level control...just avoid the extremes of either and you'll be fine.

    Tom V.
    SVS
     
  9. RyanJE

    RyanJE Second Unit

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    Thank you very much Tom. I read that DVE's subwoofer channel has a playback of +2db. I may just adjust to +2db on the spl meter over 75 to compensate. This is if I cant rent Avia.
     
  10. Edward J M

    Edward J M Cinematographer

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    DVE relies on the LFE channel for subwoofer calibration. It is encoded 10 dB too hot.

    All DD/DTS pre/pros boost the LFE channel exactly 10 dB, and JKP did not take this into account when mastering DVE. Thus, your proper subwoofer calibration tone will be at least 10 dB hot compared to the other channels. So if you are using 75 dB for the speaker channels, use at least 85 dB for the subwoofer, and it will sound about right.

    The other problem with DVE is that the subwoofer calibration tone is wide bandwidth, with strong content to 15 Hz. This compared to Avia, which truncates the signal at about 35 Hz. If your subwoofer can dig to 15 Hz, and you also have some room gain below 30 Hz, then DVE will be anywhere from 13-15 dB hot at the proper calibration level. So this would be 88-90 dB.

    I typically recommend anywhere from 85-90 dB (try 87 db) for sub calibration as a good starting point with DVE. While it may seem extreme when you are calibrating the rest of the speakers to 75 dB, it will work out properly on source material. And you can certainly double check against your AVR test tones, too.
     
  11. RyanJE

    RyanJE Second Unit

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    Excellent idea. Ill start with the 87 db and when im all done ill use internal test tones to check. Some people are anti Test tones since there not coming from the DVD player. Is this really a significant problem??
     
  12. Edward J M

    Edward J M Cinematographer

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    Well, you are starting to open a can of worms, because Avia uses redirected bass for the subwoofer calibration tone, which includes some contribution from the speaker channel in question.

    If you check all five channels with Avia, you will find the subwoofer calibration level will change 4-5 dB depending on which channel you are using.

    This compared to the AVR test tone, which is discrete to the subwoofer, and does not rely on redirected bass.

    So if you were going to compare Avia and the AVR, you might want to take an average of all the Avia channels and select the average (most representative) and then compare it to the AVR sub tone.

    In this case, comparing the AVR test tones to DVE might be more appropriate, because they are both discrete signals to the subwoofer. So if you calibrate DVE to 75/87 (speak/sub), then the AVR test tones should show about 75/75-77.
     
  13. Scott Lawrence

    Scott Lawrence Stunt Coordinator

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    Is it possible that some receivers don't send a test tone to the sub specifically? I seem to recall anytime i've used my test tone feature it tested FL, CENTER, FR, SR, SL and then back to FL. I've got a Denon 1803.
     
  14. RyanJE

    RyanJE Second Unit

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    OK. No worms ill just try that. Thanks Edward!
     
  15. RayM

    RayM Agent

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    Yeah I have DVE, read the thread and calibrated my sub to about 86-87 and that seemed to work well.

    Scott,
    My receiver (JVC) doesn't have a built-in sub test tone either.
     
  16. EdNichols

    EdNichols Second Unit

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    If the RS SPL meter reads 3 db high on lower HZ shouldn't the actual reading be 72 on the meter to compensate or do I have that backwards? Or does this not apply to AVR test tones?
     
  17. Edward J M

    Edward J M Cinematographer

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    The meter reads low in the bass regions. So a reading on the meter of 75 dB for a typical subwoofer rumble tone, would actually be 77 dB.

    In the above quote, I was only stating that if you calibrate 10-12 dB hot with DVE, it should come out "about" flat on the AVR test tones. You can fine tune to taste of course.

    Calibration with the SPL meter is a good first step, but worrying about the C-weighted differential on the meter should rank lower than running a basic FR sweep and knocking out peaks and level matching with the mains at the crossover transition point.
     

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