Reference Level-Did I do this right?

Discussion in 'Archived Threads 2001-2004' started by Kevin_Cas, Oct 17, 2002.

  1. Kevin_Cas

    Kevin_Cas Agent

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    How do you find this? I have an analog radio shack sound meter and tripod, and I set all my speakers to 75db(even though it reccomends 85 db) using the Avia test tones(C weighting, slow response, reciever volume set to -12). I am running a Kenwood VR-6060 with JBL NSP-1's. That being said, am I to watch all movies(for reference level of course, not volume preference) at this -12 volume? This is what I have been doing, and am satisified at the results, but can additional tweaking make it sound better? I remember seeing somewhere the mention of 109db. What does this number mean, and how would I find it? Am I supposed to whip out the sound meter for every movie I watch now? Seems like a pain, but I am curious. Any and all help would be greatly appreciated. Thanks.
     
  2. Bill Slack

    Bill Slack Supporting Actor

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    109db or so is where the volume should peak at reference level. And no, -12 won't be reference, because the test-tones were referenced at 85db. Not that it really matters... the point is to have all the channel levels be equal, not to be ref. level, per se.
     
  3. Bob McElfresh

    Bob McElfresh Producer

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    Kevin: All you are doing is trying to get all the speakers to produce the same volume at your seating position.

    So..how loud should you have the speakers while playing the test tones? Why not ... 75 db?

    Now that you have level-adjusted your speakers, they should all track up/down with the master volume control. So for each movie, adjust the master volume to whatever is comfortable for that movie.

    75 DB IS reference level power/sound output for a THX certified theater. But in our living room, watching movies at this level is way too loud.
     
  4. Vince Maskeeper

    Vince Maskeeper Producer

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    Try as I might, there is still much confusion on this topic. I might suggest that you read the calibration and ref level explanations in the PRIMER AND FAQ (link in my signature)...

    This main issue here is that you are talking about 2 different elements: (1) balancing speaker level and (2) setting a overall ref output.

    The steps that you've take will provide you with #1 (balancing speaker level), which is really what is of key importance on the matter. The overall volume output is really a matter of taste, so "ref level" figures are really more of a novelty than any practical point of achievement.

    The AVIA tones are specifically designed so that the overall volume level you achieve by calibrating them using the target point of 85db of SPL output will be ref level. It is likely that your particular unit would have ended up at/around the -02 point on the volume knob had you chosen to use the 85db point for your calibration level as AVIA suggested. What that would mean would be that playback at -02 would be equal to "ref level", meaning the loudest sound coming from any one speaker would be 105db in SPL.

    Instead, you chose to calibrate your system using the same tones at 75db of spl output. This, essentially, means you are operating 10db below REF level, and as such the maximum output you will experience from any one speaker in your system will be at or about 95db of spl output.

    Again, you need not have a meter read handy for every film- nor should you consider it for an additional second. Once you have balanced all the speakers in the system so that they read evenly, you have calibrated your system and are encouraged to adjust the master volume as you see fit.

    Enjoy!

    -Vince

    PS: The statement "75 DB IS reference level power/sound output for a THX certified theater" is correct in what Bob's point was (This "ref level" is suitable for theaters, but home use may vary)-- but is still technically "incorrect", and something we should be careful of... The ref point is 105db of SPL output maximum-- they often use tones to measure this that are 30 steps below maximum, hence 75db measurement. But, this 75db number would cease to be relevant if any other test tones were used- so it is a bit of a misnomer to say 75db is ref level.
     
  5. Will Orth

    Will Orth Stunt Coordinator

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    the best spl meter is your ears! not the spl meter!
    though an RTA- REAL TIME ANALIZER is a must. i can still adjust my own room with out one as i have done 1000's of rta measurments and i just did mine and found a few problems, only way to fix mine is a lower octave EQ but i can live with the 6db BOOST at 50hz for now...


    Will
     
  6. Vince Maskeeper

    Vince Maskeeper Producer

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    I'm not sure what Will meant by this- if he was suggesting your ears are a good judge of your overall volume setting, or if he was suggesting that a SPL meter is unnecessary for calibration.

    If he was suggesting the latter, you'll find his opinion in the overwhelming minority. The reality is accurate calibration is nearly impossible without a basic SPL meter.

    I too have done 1000s of RTA adjustments, and hundreds of SPL speaker balances- and while I can EQ a room to the ballpark of flat using just my ears- I still break out the SPL meter when I'm doing speaker balance.

    -Vince
     
  7. Will Orth

    Will Orth Stunt Coordinator

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    Vince Maskeeper: well I would like to clear up this post, for some one that has no sound experience the spl meter is a good tool! just for me I have had to tweak so many systems by ear, if you have a good ear use it, I just did my sine sweep and found my 2 room problems one at 50 Hz and one at 300hz also I need a sub EQ, I have had my own recording studio years back and have Won over 5 first place car audio competitions for the best sounding vehicle in my class and have 60 dusty trophy's in my basement. After you have listened to 20 test discs for 1000 times and have a good ear for balance, it is second nature. I have been doing audio for 20 years but video i am a newbie and wont boast any comments in this area.

    I will have some tips on my web site for sound advice.
    they way I test some systems is with a dcr/vom meter set on AC and test each output of the amp with different tones.

    this is a must on sub systems with multiple amplifiers!
    I had to match 12 mono block 1200 watt amps to with in a 1/10 of a volt for an spl van.


    But the bottom line is you have to listen to it not the METER!

    So try the meter if you don't like it set it to what you think is best in the end, i have set RTA'S that scored a 40 but sounded like crap! so use your own judgment in the end, a machine is a ballpark tool, you have to live with what you have created....

    Nuff said
     

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