Logic Output Calibration [SOLVED]

[markalex905]

Hi - I've been doing lots of post lately, so I tried calibrating my speakers. I set everything to Unity, turned on Logic's Pink Noise @ -20 dB, then cranked my interface until my SPL meter hit 79dB (small room). (Slow response, dBC)

 

However, when I move to iTunes, QT, etc. the output is "blow up my speakers" loud. I have to set iTunes internal volume to almost zero.

 

Is this normal? Should I just change my interface output when I go back and forth?

 

Also, I did the same calibration test in ProTools and got a very different output. (3 or 4 dB) I've read threads on Pro Tools and Logic having different output levels, but people keep coming back and denying it. I tried all the Pan Law options, and still the discrepancy. Even playing back a test tone sine wave file in Logic and PT gets different output levels.

 

Anyone ???

[David Nahmani]

when I move to iTunes, QT, etc. the output is "blow up my speakers" loud

iTunes has all sorts of ways to process the signal, QT does not. Are you listening to the same file? The same file out of Logic or QT should have the same level.

 

I've read threads on Pro Tools and Logic having different output levels

Where have you read that? PT and Logic are Digital Audio Workstation. In digital, the maximum level is when all the bits inside a sample are set to "1", and that level is called, by definition, 0 dB FS (Full Scale). It does not, by default, have any correlation to levels in the outside world (dB u, dB V, dB SPL etc...), so you can make that relation if you want, but whether a full scale sample (so, basically, in 24 bits, a sample of 111111111111111111111111) comes from PT or Logic, your converter doesn't care.

 

Even playing back a test tone sine wave file in Logic and PT gets different output levels.

Same audio interface?

[markalex905]

when I move to iTunes, QT, etc. the output is "blow up my speakers" loud

iTunes has all sorts of ways to process the signal, QT does not. Are you listening to the same file? The same file out of Logic or QT should have the same level.

 

I've read threads on Pro Tools and Logic having different output levels

Where have you read that? PT and Logic are Digital Audio Workstation. In digital, the maximum level is when all the bits inside a sample are set to "1", and that level is called, by definition, 0 dB FS (Full Scale). It does not, by default, have any correlation to levels in the outside world (dB u, dB V, dB SPL etc...), so you can make that relation if you want, but whether a full scale sample (so, basically, in 24 bits, a sample of 111111111111111111111111) comes from PT or Logic, your converter doesn't care.

 

Even playing back a test tone sine wave file in Logic and PT gets different output levels.

Same audio interface?

 

---------

 

Thank you David. I know your THEORY is sound, and Logic and PT SHOULD output the same volume, but try it. Take an audio file of a sine wave. Open sessions in PT and LOGIC, no plugins, everything at Unity. Play the file from both DAWs and measure the SPL in your room. When I do this, there is a 3 to 4 dB discrepancy EVERY time. I THOUGHT it was the Pan Law in Logic, but nope. This happened on 3 computers in 3 studios.

 

Re the calibration - I was just wondering if -20 dB is the right level for Pink Noise when I'm calibrating for A/V work. It forces me to REALLY crank my monitors to get 79dB on the SPL. This results in a pretty quiet mix. (Maybe I'm just used to modern pop songs, where we L2 everything up to a hair beneath zero.)

 

And yes, same interface (TC Konnekt 48).

[David Nahmani]

I know your THEORY is sound, and Logic and PT SHOULD output the same volume

Yes: they should, and they do, as the sound theory indicates. Your converters don't make the difference between a "1" from PT, a "1" from Logic, or a "1" from any other app for that matter. A "1" is a "1" is a "1", period.

 

So then that means your PRACTICE is wrong. Somewhere in your test, something is going wrong. I'm not sure where. Did you check the digital level at the output of both Logic and PT? In the TC Electronic mixing software?

[markalex905]

David, I reply to you with my tail drooping behind my legs.

 

As it turns out, it WAS the Pan Law setting after all. Pro Tools defaults to -3dB, all our Logic sessions were set to -3 Compensated. Switching it to good old -3 did the trick. (Wish it were a Global setting -- Now I have to change it in all the sessions...)

[David Nahmani]

AH! You have to trust in the theory sometimes... well thanks for letting me know what it was, good to hear.

[Tumer]

Also a good tool for calibration of monitors (speakers) in terms of dB SPL:

 

http://www.audiopluggers.com/press-2011-05-12-kmeter-demo.html