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AV32R: Testtone for subwoofer and calibrating?

Discussion in 'TAG McLaren Audio Owners' Forum' started by LJN, Jan 22, 2005.

  1. LJN

    LJN
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    -Do you have any tips how to calibrate the LFE-sub from the testtone? I dont have any problems with the .5. speakers but with the sub I cant do a´proper reading from my sound level meter.

    My sound level meter are a Quest electronics type 211FS. Is a industrial model with 60-120 dbA or dbC in five ranges. Have also fast and slow response selection. Range 20 hz to 10 KHz. It is a old model but I think it have good quality.

    The sub test tone, what "hz-range" have that?

    /Lennart
     
  2. Dr Udo Zucker

    Dr Udo Zucker
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    Hi Lennart, in order to calibrate the subwoofer using the THX test tone, created by the AV32R, use your meter’s C-weighted scale in slow measuring mode. The level to aim for is 75dB, although most like a little "punchier" LFE channel and hence go for 77dB - 78dB.

    There are many room resonances in every listening room, which enhance or cancel pressure waves. They are very recognizable at lower frequencies, hence the AV32R DP/AV192R offer TMREQ to reduce/remove their influence. These resonances also affect your calibration, particularly that of the subwoofer. Depending on the exact position in your listening room, you might get differences of sometimes up to 20dB. Therefore in case of varying results during subwoofer calibration it is recommended to slowly move the sound pressure meter around your central measuring position to see if your measurements gets more stable.



    The THX test tone is a mixture of frequencies, selected to provide a good calibration despite those room resonances. Unfortunately, the available range during subwoofer calibration isn’t that wide and often “spiced-up” with many room resonances.



    Hope this helps…
     
  3. Miron

    Miron
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    I must add something here, I heard two systems from two friends (one Arcam/TAG and one Denon) where people set LFE to 78 and 79dB which they claim (as a main reason) is important to listening music in Direct+Sub.


    After this Udo's posting I am not sure about anything with sub levels anymore ???
     
  4. Dr Udo Zucker

    Dr Udo Zucker
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    Hi Miron, as mentioned above, the actual subwoofer level is very much affected by room resonances (if they are not corrected), i.e your THX test tone setting might differ from the THX recommened 75dB to the often used 77+/- dB setting.

    The best practise will be to set the level to 75dB and then correct the room resoances using TMREQ. After that correction is done, you need to recalibrate. It isn't uncommon that the level than shifts by a few dBs.

    In other words, the THX test signal will always be a "best guess" only if we haven't removed the influences of room resonances. If one has no access to TMREQ, you need to rely on your ear.

    Multi channel recordings, here most often movies, can live with a much wider calibration tolerance level as most often the low frequncies are used for "heavy" effects. A detonation sounds aways impressive, whatever the exact setting:) .

    Using Direct+Sub in music allows a much more realistic setting by ear.

    Has this "removed" your confusion?
     
  5. Miron

    Miron
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    A bit, thanks.
    I will have to reposition my whole room soon because on 11.2. all new furniture is coming in and then I'll try to get the best out it.

    I will post here and ask for help if any needed. Thanks!
     
  6. LJN

    LJN
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    -Thanks Udo for help and information! The only probelm I get was the "groundlevel" My testtone was round 85 db with C-scale, and I dont know how to adjust that?


    /Lennart
     
  7. Dr Udo Zucker

    Dr Udo Zucker
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    Hi Lennart, if your sound pressure reading is 85dB, then you need to adjust the AV32R's output level that it goes down to nominal 75dB. This is done in the Speaker Calibration Section. It is identical to the calibration of all other speakers.
     
  8. LJN

    LJN
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    Dr Udo: In that case I have to "lower" all my speakers -10 db. Today I have the centerlevel 0 db, surround +0,5 db, sub +2,0 db etc. What are the difference to calibrate at 75 db against 85 db? In "my world" I get the same calibration between the speakers?

    /Lennart
     
  9. Dr Udo Zucker

    Dr Udo Zucker
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    Hi Lennart, if you have all speakers calibrated to 85dB, then you can let them stay that way. All what happens is that now the "Directors Volume Level" is at -10dB instead of 0dB. May I ask why you opted for 85dB in the first place?
     
  10. LJN

    LJN
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    Dr Udo: I dont have any answer on that? Where did I set the "masterlevel?
    Maybee I have miss something here?

    The acoustic output depends on several factors, input sensitivity on the poweramplifiers and the sensitivity on the speakers.

    /Lennart
     

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