Sound and Vision (Avia) sub calibration too low?

Discussion in 'Speakers' started by Joe Spratley, Aug 14, 2003.

  1. Joe Spratley

    Joe Spratley Stunt Coordinator

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    Is it me or is the Avia sub calibration tone around 6-8 db's too low?
     
  2. Brian Henchey

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    If you mean that at "reference level" (for me, -10 on my pre-pro = 85b on the five channel speaker level test), the subwoofer level signal (as it bounces between the front left speaker and the subwoofer) is at 81-82db, I have noticed that too.

    It's unclear in the menus whether you need to calibrate the sub to 85db or to the signal bouncing to the left front speaker.
     
  3. Lewis Besze

    Lewis Besze Producer

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  4. James~P

    James~P Stunt Coordinator

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    whats it mean for a signal to bounce from the front left?
     
  5. Kevin C Brown

    Kevin C Brown Producer

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  6. Sebastian

    Sebastian Second Unit

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    Just trying to clarify,
    Are you asking about this DVD:
    [​IMG]
    Or the actual Avia DVD:
    [​IMG]

    If you have the S&V HTT DVD (red case),
    Yes, when I calibrated the sub to match the other channels at 85dB the sub level was way too low. When I used this DVD to calibrate my sub to read 85 dB to match my other speakers, I almost had to turn it off and when watching movies there was almost zero bass present. I ended up calibrating the sub this way: when my surronds speakers are reading 85dB on the meter, I adjust the sub to read about 7-10 dB over that and it sounds good that way. Comparing the results to VE, with the sub 5dB hot using the video essentials DVD and then using the HTT DVD the meter was reading 8-10dB hot on the meter. So basically IMO the S&V HTT bass signal is in error ~5dB.
    If you are asking about the actual AVIA DVD, nevermind what I just said.
     
  7. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    There are so many variables. Rest assured that the tones on these discs ARE correctly encoded. But then you have room resonances, phase issues, frequency nulls, etc. to deal with in your room.

    For instance, Kevin's problem: That means the center channel is likely out of phase with the subwoofer because of the room acoustics. Alas, there's not much you can do about it if the phase of the front speakers match. You have to set the phase of the subwoofer so that it matches the speaker that it is closest to and hope that matches up with the rest of the system (or find a decent compromise). But that is why Avia puts the subwoofer test tones in the main channels and lets your receiver's crossover do its job -- so you can evaluate the interaction for each speaker across the crossover range.

    Second example: If your room has a frequency reinforcement of 6dB around 50Hz and you adjust using the subwoofer test tones, the meter will read 82dB at reference (taking into account the meter's 3dB offset with bass noise tones as was previously mentioned). However, since you have that 6dB hump at 50Hz, that likely means that all the other frequencies have now been calibrated to 79dB instead of 85 (assuming the rest of the frequency response is flat, which it likely won't be). For most people, these test tones are a good general guideline. A quick run-through with Avia's bass sweep tones while watching the SPL meter should give you an idea of whether you have a serious frequency hump, as you'll see the meter jump up quite a bit.

    Because of the way bass interacts in every individual room, the only way to get your sub to true reference level across the frequency range is by using an equalizer between the receiver's subwoofer output and the subwoofer input. This lets you do advanced fine-tuning of each frequency FOR YOUR ROOM by playing tones at each frequency and calibrating using the Radio Shack SPL meter's correction chart to compensate for its low frequency rolloff. Alternately, if you have a real-time analyzer and a calibrated microphone, you can see the frequency response in real-time during bass noise tones and equalize accordingly. Once you have achieved a flat response, it ensures that you don't have any reinforcement during the subwoofer calibration noise tone and you can then dial the subwoofer in to reference level, ensuring that all frequencies are at their correct levels to reproduce the intended audio mix.

    In short, these discs offer a good general guideline for dialing in your subwoofer, but because of the differences in each individual room that setting may not work as you expect it to. This is why Avia offers such a great deal of differing tones -- so that you can do advanced evaluation and calibration of your system.
     
  8. Sebastian

    Sebastian Second Unit

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    Ah very good point Jeremy, Come to think of it, I have a 10-15dB peak around 36-40 Hz.
    However my meter only flucuates 4 dB. Why not more?
    Freq Raw correction
    166172.5
    1864.572.5
    207380.5
    2271.578.0
    257479.0
    288185.0
    31.58487.0
    369193.5
    409294.5
    458486.0
    507374.5
    567273.5
    637576.5
    717576.5
    8074.576.0
    896768.5
    1007476.0
    1116869.0
    1257474.5
    142.57878.5
    1607877.5

    These are old and have since moved furniture around
     
  9. Lewis Besze

    Lewis Besze Producer

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  10. Joe Spratley

    Joe Spratley Stunt Coordinator

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    Sebastian, Yes I have the Sound and vision version but its not in the red box its the best buy version in a black box but I believe its the same. I have found the same results it seems to be off around 5 db's.
     
  11. Kevin C Brown

    Kevin C Brown Producer

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    I personally didn't find any differences between the S&V disc and Avia in terms of speaker cals.

     
  12. Zack_R

    Zack_R Stunt Coordinator

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  13. Frank Carter

    Frank Carter Screenwriter

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    I don't believe this is true. If I calibrate with S&V HTT, my sub level is extremely low. If I then pop in my Ultimate DVD Platinum with the levels set the same my L/R/C/SL/SR are all the same, but the subwoofer level reads low. I can't remember by how many dB, but I think it was around 5-7dB.

    BTW, when I calibrate with the Ultimate DVD, the sub sounds balanced.
     
  14. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    Frank, the levels for those tests are digitally encoded at the proper level, so there's no question whatsoever about that. Now, what your system does with them is another matter altogether. After equalization of my subwoofer, my receiver's internal tones match up perfectly with S&V, Avia and Video Essentials at their respective playback levels.

    I'm not familiar with Ultimate DVD Platinum's tones, but perhaps they are using a different type of noise for their tests. Also, Avia and S&V HTT use the bass management of your system to play back the tones, and they are not encoded in the LFE channel as they are with some other discs. This, as I said, is for advanced configuration of bass management. So with speaker interaction, phase problems, room acoustics, etc. even test tones from different discs can be affected.

    The bottom line is that Kevin has the right idea: These discs are merely a guideline for reference levels. Where your system's settings end up after that is up to you.
     
  15. Frank Carter

    Frank Carter Screenwriter

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    That must be why, my Ultimate DVD platinum uses a LFE tone and S&V HTT doesn't.
     
  16. DavidES

    DavidES Stunt Coordinator

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    FYI on Avia's subwoofer level tests, it uses bandpass noise centered around 40 Hz (verified with spectrum software) so if you have a room peak or sub is peaky there, it will make the rest of your bass frequencies way too low in output when using SPL meter to set level.
     
  17. Sebastian

    Sebastian Second Unit

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    David,
    Thanks for the info. If they use the same subwoofer noise calibration on S&V HTT DVD then that makes perfect sense. Too bad I thought my LFE out was hosed at first. I almost took it in to have it verified but the service dept said they would have no way of knowing if it messed up like that. I feel like a fool now.
     
  18. GregBe

    GregBe Second Unit

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    Jeremy Anderson,

    I have an Onkyo 600, and from your previous posts, I believe you have the same. You have mentioned that "after" sub equalization, your internal test tones are dead on. Does that mean that you would not recommend the internal test tones for the sub.
    I do have a SPL Meter and Video Essentials, but am entertaining simply using the receivers internal tones for everything since VE does not include a tone for rear center speaker. Any thoughts?
     
  19. Michael R Price

    Michael R Price Screenwriter

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    "FYI on Avia's subwoofer level tests, it uses bandpass noise centered around 40 Hz (verified with spectrum software) so if you have a room peak or sub is peaky there, it will make the rest of your bass frequencies way too low in output when using SPL meter to set level. "

    Bingo! Calibrate hot, or equalize away.
     

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