Pondering Sub Calibration with Avia

Discussion in 'Archived Threads 2001-2004' started by Bryan Acevedo, Nov 5, 2001.

  1. Bryan Acevedo

    Bryan Acevedo Second Unit

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    After reading for months on this forum - there always seems to be a question of how to calibrate the sub level. It seems this is the biggest problem with home theater setup. I was thinking about it the other day and came up with some hypothesis as to why it may be so hard to actually calibrate a sub correctly. I thought I would post them here, to see what others thought about them, and see if it makes sense.
    1) Setting the Sub to match the output of the main speakers is sub dependent AND room dependent. It seems that whenever I set my sub to match the mains in output, the bass is very, very weak on everything. I think this is because in MY room, with MY sub, there are some peaks in the Frequency response of the sub. So when I am calibrating to 85 db, I am calibrating one frequency (the peak) to that level. Then when I play back a movie or music, the bass is like 6 - 8 db lower than it should be, because the bass is at a different frequency than what I calibrated at. The reason I think this, is because when I play the test tones for the main speakers, the needle on my RS SPL meter stays at one level. However, when I try to calibrate my sub, it jumps all over the place. I can never get it to stay at one level. I think this is where the problem for most of us lies. Where do we calibrate it at? Does anyone else have this problem? I would be interested to know why my needle jumps around on the sub level only.
    This would also make me believe those with a parametric EQ that can get rid of these humps would have an easier time with calibration. True?
    2) Maybe setting the sub that low just sounds weak, because we are all used to a nice mid-bass hump from the entry level stuff we all started out with. I heard a little computer speaker system this weekend at Comp USA - this little tiny sub had some nice bass punch. In no way can it match the output of my Velodyne SPL1200 - but it did produce a nice punchy bass sound. Maybe we are all just used to this, and setting up the sub correctly (read flat) sounds incorrect. I don't know - but this is a thought.
    3) Maybe music and movies really do need different settings for subs. Movies have that LFE channel at +10db, but music doesn't. Even when you set your sub up at a low level, that extra 10db can really make it crank for a movie, but for music it can sound very weak. Just a thought.
    It could be combinations of all these things - but it amazes me how many questions there are on this one topic alone, and it seems that everyone has a different way of doing it.
    What I have done is calibrated my mains with the SPL meter, and just calibrated my sub by ear with some music I am very familiar with, and know how I want my sub to sound on it. It may not be totally accurate, but it is the way I have found to actually enjoy my system more. I am interested to hear what others have done with their sub setup.
    Bryan
    [Edited last by Bryan Acevedo on November 05, 2001 at 02:07 PM]
     
  2. Karim Nogas

    Karim Nogas Stunt Coordinator

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    During the warble tones, my SPL needle was also flying all over the place to the same degree, irrespective of where I set the low pass filter.
    What AVIA did help me discover was where the sub bottomed out and it showed me I have a lousy sub. From about 95Hz to 65Hz, there is minimal dB output. Then when it hits 45Hz to 35Hz, it booms creating a sound that hurt my ears. At 30Hz, it bottomed out again.
    Unfortunately, that 45Hz-35Hz seems to be in a lot of movies and I have no choice but to only set the sub's volume to 1 out of 10 or it becomes totally unpleasant.
    I too had no choice but to set it by ear. For now, to get more bass output, I simply crank the volume on the receiver.
    ------------------
    You don't need a centre channel.
     
  3. Bryan Acevedo

    Bryan Acevedo Second Unit

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    Thanks for the info Karim!
    Does anyone else have any thoughts on this?
    Bryan
     
  4. JohnDG

    JohnDG Stunt Coordinator

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    Karim,
    How did you determine (and what are) the frequencies for the Avia sub warble tones?
    jdg
     
  5. Karim Nogas

    Karim Nogas Stunt Coordinator

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    Bryan,
    No problem. I actually should have said to increase bass I crank the BASS control on the receiver, not the main volume control.
    John,
    The warble tones and frequencies are two different tests. The warble tones are used to set the low pass filter. The other test starts at 150Hz and goes down to 20Hz and is used for dB level.
    If I remember correctly, with the warble tones, you should set the LPF to where there is less movement of the needle on the SPL. With the frequencies, what you are looking for is a consistent decibal output. Unfortunately, I don't have either and am not even close.
    ------------------
    You don't need a centre channel.
     
  6. Ariel

    Ariel Stunt Coordinator

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    I also have the same problem with the sub calibration. when i check the sub output using the individual test tone from another cd that i have, it showed that the output has some peaks up to +15db on some frequency. what i did was move the sub to the location where the biggest swing is minimized to just about +5db. when i calibrated the sub the needle of the spl meter in not going wild anymore. with this setup, the sub blends well with the mains for music.
     
  7. Bryan Acevedo

    Bryan Acevedo Second Unit

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    Ariel - thanks - I have a feeling it is the placement of the sub as well. Unfortunately, I don't have a lot of options, so the sub has to stay where it is. But the overall sound quality is there - maybe a few peaks - but I can live with that!
    Thanks for the info.
    Bryan
     
  8. JohnDG

    JohnDG Stunt Coordinator

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    Karim: yep, that is the approach I took. Thanks.
    Ariel: without an equalizer, sub placement was the only way for me to tame the variations in db's during the frequency sweep.
    In the corner or on the side wall, it was all over the board. Happily, I was able to put the sub under a coffee table in the middle of the room and the variations are down to +/- 5 db's. Not as much kick, but the "boominess" at the peaks has been tamed.
    jdg
     

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