5.1 speaker balance: SPL meter reading: Shouls it be 85,75,65???

Discussion in 'Archived Threads 2001-2004' started by shankar, May 2, 2002.

  1. shankar

    shankar Stunt Coordinator

    Feb 4, 2001
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    Hello all,

    May be this was discussed before.

    I have seen it repeatedly here that your speakers should be balanced so that the SPL meter reads 85dB while the master volume control reads 00dB on the reciever. This is the so called "reference" level.

    AVIA disk says that this will be too loud and hence suggests balancing the speakers to 75dB reading on the SPL meter.

    Hypothetically, lets say someone sets it at 85dB and then finds it too uncomfortable. They then reduce the master volume to a comfortable level. Will the 5.1 "balance" still remain??

    Let's now say that someone uses the AVIA disk and "accidentally" balanced the speakers at a certain master volume so that the SPL reading is 65dB. He finds it too low while listening and then increase the volume to a comfortable level. Will the 5.1 balance be intact here?

    If yes, why can't one use the receiver's test tone to balance the speakers?? As long as the balance remains when the volume is changed with the master volume control, how does it matter what the source is or what the reading on the SPL meter is (let's just keep 85,75,65 as the choices
  2. John Kotches

    John Kotches Cinematographer

    Mar 14, 2000
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    A lot of good questions you've asked, most have been answered before once or twice....

    However, I'll start with this.

    "Reference Level" -- 85dB is considered reference level with the Avia disc because it is authored with the test tones at -20dBFS (20dB below the loudest possible signal that can be encoded digitally), and the volume set to Reference level.

    85dB might be "too loud" for regular listening but it's not that bad for setting up speakers IMO.

    In terms of speaker balancing, if the volume control is competently engineered, the channel trims (aka balance) will remain irrespective of the overall volume. So the answer to your first questions is "yes".

    Using the receivers internal test tones you are testing past the DD/DTS decoder. Using AVIA (or Sound & Vision's Tuneup disc) you are testing the entire signal chain, including the DD (and DTS on S&V) decoders. There can be differences between the receivers internal test tones and the DD/DTS decoder outputs. In theory there shouldn't be, but practice is a bit different.

    It doesn't really matter what volume you calibrate to in the grand scheme of things, but by calibrating with 85dB on Avia or 75dB with internal tones, you can say with confidence if the volume control reads -10.0dB you are 10dB under reference, and keeping peaks to 95dB SPL for main speakers, and 105dB for the LFE channel.

    Hope this helps.


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