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Is there a 'summing law'?
Old 13th October 2013
  #1
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Is there a 'summing law'?

When you make a duplicate copy of an audio track in your DAW and they're both playing back at the same time, is there a predetermined amount of increase in decibles that you can expect? The panning law can be up to 6.02 decibles so Wikipedia says, but I'm not sure that same number applies to just summing a mono signal.
Old 13th October 2013
  #2
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TREMORS's Avatar
If they are the exact same should be 3db louder

Sent from my SPH-D710BST
Old 13th October 2013
  #3
Registered User
If they are exactly the same they will be exactly 6dB louder. Double the voltage.

If they are exactly the same but reversed polarity, they will cancel out. Zero voltage.

If they are random audio wave files they will fall somewhere in between, but probably somewhere around a 3dB boost.
Old 13th October 2013
  #4
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So is it 3 or is it 6?
Old 13th October 2013
  #5
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drBill's Avatar
It's 6. Pretty easy to do in your daw and see for yourself. Takes less time than it took for me to type this....
Old 13th October 2013
  #6
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I'm trying to do it on paper and I don't know the formula/math :P

Also though, it makes me wonder why a -3db pan law is the norm. Shouldn't it be 6 if that's the case?
Old 13th October 2013
  #7
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drBill's Avatar
Quote:
Originally Posted by HSLand View Post
I'm trying to do it on paper and I don't know the formula/math :P
I was never too good at math...,,,
Old 13th October 2013
  #8
Registered User
The whole thing about pan law is completely optional and doesn't make any difference unless you want to pan things dynamically. (Because in a static pan mix you just set the fader where you want, nobody can tell what pan law was in use).

If the pan law is zero, when you fade from left to right the volume double in the centre. That is sort of how it is in real life. I imagine a train track. If you are standing in front of a straight train track the volume increases until the train is right in front of you, and then it decreases.

If you have a pan law of -6dB the effect is rather like standing in front of a semi-circular train track that maintains equal distance from your ear. So as it travels from left to right the volume remains the same.

With a single mono signal it will double in the centre unless you intentionally attenuate, hence why some people like using a pan law. I see no reason for it, and set my DAWs at zero pan law.

If you are dealing with mono signals then -6dB will maintain equal apparant volume. But with dissimilar signals (wide stereo) then signals don't sum to create a 6dB increase, so the 3dB attenuation is probably better.

It's all a bit hit and miss, and ultimately you will set the fader where you want it, and master bus compression changes everything anyway.

I wouldn't worry about it. Sometimes pan law settings mess with levels when you are exporting files and stuff, so it pays to have some understand of what you are working with. But I just turn it off - can't see the point.
Old 13th October 2013
  #9
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Old Goat's Avatar
 

Quote:
Originally Posted by Kiwi View Post
The whole thing about pan law is completely optional and doesn't make any difference unless you want to pan things dynamically. (Because in a static pan mix you just set the fader where you want, nobody can tell what pan law was in use).

If the pan law is zero, when you fade from left to right the volume double in the centre. That is sort of how it is in real life. I imagine a train track. If you are standing in front of a straight train track the volume increases until the train is right in front of you, and then it decreases.

If you have a pan law of -6dB the effect is rather like standing in front of a semi-circular train track that maintains equal distance from your ear. So as it travels from left to right the volume remains the same.

With a single mono signal it will double in the centre unless you intentionally attenuate, hence why some people like using a pan law. I see no reason for it, and set my DAWs at zero pan law.

If you are dealing with mono signals then -6dB will maintain equal apparant volume. But with dissimilar signals (wide stereo) then signals don't sum to create a 6dB increase, so the 3dB attenuation is probably better.

It's all a bit hit and miss, and ultimately you will set the fader where you want it, and master bus compression changes everything anyway.

I wouldn't worry about it. Sometimes pan law settings mess with levels when you are exporting files and stuff, so it pays to have some understand of what you are working with. But I just turn it off - can't see the point.
Thanks for that. I never really got it about pan laws until now.
Old 13th October 2013
  #10
Gear Addict
 

Tf v is your new voltage level and u your old voltage level then the dB increase from new to old is 20xLog(v/u). (Log is base 10 log)

So if you double something you get 20xLog(2) = 6.02
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