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Reference Level Question

Discussion in 'AV Receivers & Amplifiers' started by mooky, Dec 15, 2003.

  1. mooky

    mooky
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    Ok,

    So somethings been bugging me since I contemplated using an SPL and setting to 75dB.

    First let me explain, in hifi world I was always concious of never over running the AMP and tried not to run the standard volume control past half.

    So, now on to SPL setting. So according to you all i'm supposed to set my amp to 00dB and then play the test tones. What concerns me is this is FULL volume on my Yamaha. Is this ok?

    Mark.
     
  2. Brogan

    Brogan
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    Is 0dB really full volume on the Yamaha?
    I only ask because the Pioneer AX5 full volume is +12dB.
     
  3. jont

    jont
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    Do some amps not allow you to adjust/set the way the volume settings go ... ie 0>50, -50>0, -35>15, etc ...

    Anyway isn't reference level the 75db and then whatever your amp says the volume is to give you that 75db ... ?
     
  4. ailean

    ailean
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    Yeah the 0db thing got me confused too on my Yam A1. 75db on a SPL metre is about -20db (just short of half way) on my setup.

    So yes play test tone on either main L or R and turn main volume up till you read 75db at the normal listening position. Then calibrate the other channels to match without moving main volume. I stuck a small arrow cut from sticky tape to the dial to mark the point for future referance. :)
     
  5. Reiner

    Reiner
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    That might be correct but you are oversteering the amp beyond it's normal operating point. This isn't good since it introduces distortion and limits your headroom / dynamic range. 0dB is the normal operating point and if possible you shouldn't go further than that.

    Yep. And actually it's dBA, hence it does not directly compare to the labels of the volume knob.
     
  6. mooky

    mooky
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    Ahhh I see. So I got it arse backwards. I don't turn the volume on the amp to 0db and then modify the L/R/C etc. to 75db using the SPL. I turn the volume up till I read 75db and then calibrate all speakers to this?!?

    Mark.
     
  7. cskates

    cskates
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    Don't you mean dBC? The C scale is flat, but the A scale includes a curve to compensate for the frequency response of the ear. Your SPL meter should be set to 'C' weighting and 'slow' when calibrating the volume. A difference of 10dB on the volume scale should be equivalent to a 10dB change in the volume measured by the SPL meter, ideally anyway...

    Normal home cinema reference level is 105dB peak from each channel, but since 105dB is so loud we measure tones recorded 30dB below peak. So when you calibrate to 75dB using a -30dB test tone you're actually calibrating so that the peak is 105dB. An exception worth mentioning is the Avia DVD, the test tones on Avia are recorded at 20dB below peak so you calibrate to 85dB.

    The exact calibration technique will depend on how your amp was designed. Many amps, including all THX ones I've seen, will set the amp to 0dB when the speaker calibration is run, so 0dB will be reference level. Some amps will leave the volume control active so you would set the volume to measure around 75dB, and then adjust the other channels to match. The position of the volume control will then be reference level, so mark or remember it. If you're using a DVD or other external source to calibrate, remember to set your amp's volume to 0dB or some other known position first.

    You don't have to listen at reference level, it may be too loud for your ears or your equipment. Listen at whatever level you like, that's what it's all about at the end of the day!
     
  8. nealgs

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    after my first initial setup, 75db is reached at between -15 and -14 or so on the volume indicator on our Yamaha RXV1000RDS.

    will be redoing the setup again as was using wrong test-tone (according to the manual)

    Gary
     
  9. mooky

    mooky
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    What do you mean, using wrong test tone?

    Also, On your Yamaha is it possible to use the volume nob whilst test tones are playing or is the volume automatically set at 00db as the previous message?

    Mark.
     
  10. nealgs

    nealgs
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    mooky - IIRC yes, volume knob is useable, as it needs to be in order to set MAIN L to 75db in order to calibrate the others.

    There appears to be two areas of tones - one is the TEST tone button, the other is the Low Freq Test menu item

    I should read the manual first :) as i used the Low Freq Test option. This was as i couldn't get the MAIN L speaker to stay current whilst using the TEST button option ( so couldn't see how I was supposed to balance everything) it kept cycling round all the speakers.

    a bit confusing at times the Yamaha user manual

    Gary
     
  11. ailean

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    I had the same issue with the cycling tone being too fast to get a good reading. Ended up getting the AVIA DVD which made life a lot easier as the tones can play upto about 30 secs.

    End of the day the numbers don't mean anything, what's important is to turn the main volume up to where you normally listen and make sure all the channels are equal from your seating position.
     

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