Pan Laws and Bounce Tests

Question

Level 2

494 points

Pan Laws and Bounce Tests

I've been trying to wrap my mind around the following for a few hours now, and am, it seems, no where near understanding this, so I'm posting on here in hopes of finding a remedy/solution to this issue:

A pan law of 0dB obviously does nothing to your levels.

A pan law of -3db takes the center pan and drops it -3dB while leaving your left and right pan signals the same.

A pan law of -3dB Compensated leaves your center pan the same, and RAISES your left and right pan signals +3dB.

Both the -3dB and the -3dB Compensated pan laws are designed to address the center pan loudness that the human ear perceives when listening to equal level signals across the pan spectrum. Both end up giving the listener a smoother signal across the entire spectrum by comparatively dropping the center pan signal 3dB. Due to the different methods of doing this, however, there's an over level difference of 3dB between either setting, -3dB Compensated being about 3dB louder.

. . .

Okay now take a file from a sequence that has a pan law of -3dB and bounce it.

If you reimport the bounce back into the same sequence and want to hear how it sounds at a level-accurate playback, then you have to at that point change your pan law back to 0dB. Correct? And this, of course, is because your bounced track was ALREADY bounced at a pan law of -3dB. Your sequence is already at a pan law of -3dB. So playing the bounce track back in the same sequence would add ANOTHER -3dB to it unless you change the pan law of the sequence back to 0dB.

That being said (and hopefully understood) here's my question.

What on earth is the difference between taking a track that was bounced at a pan law of -3dB and hearing it back (in your sequence) at 1) a pan law of 0dB, and 2) a pan law of -3dB compensated? In other words, when I take that track that was bounced at a pan law of -3dB and play it back at a pan law of 0dB, I get a level of, say, 8.4dB. If I change my sequence's pan law to -3dB, then I have to boost the bounce itself by +3dB in order to get the same 8.4dB signal. If I, however, change my sequence's pan law to -3dB Compensated, whereas I was under the impression that I would end up getting a signal boost to 11.4 from my bounced track (since, again, what a pan law of -3dB Compensated does is leave your center pan signal the same while boosting your left and right pan signals +3dB) I end up getting the same 8.4 signal that I got when I played the bounce back at a pan law of 0dB.

This confuses me.

What's going on? Can someone explain it to me? It seems that a proper understanding of Logic's Pan Law dynamic is absolutely crucial to being able to hear back bounces (among other things) properly. Without a proper understanding of such, it seems one is not going to know the hows and whys of the different signal fluctuations that take place in one's final mix.

At the risk of sounding presumptuous, this, it seems to me, is a rather advanced question, and not for the light hearted. While I would appreciate responses from anyone and everyone with something to impart, I would really, really like help from those Logic users that have a thorough understanding of the dilemma.

Thank you very much everyone in advance for all the help.

Javier Calderon

Macintosh Dual 2 Gig G5, Mac OS X (10.4.7)

Posted on Jun 21, 2007 9:47 AM

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Answer 1

Best reply

KOROS

Level 2

290 points

Jun 21, 2007 10:00 AM in response to Javier72

I agree this needs sorting out. I'm in the middle of a huge project in Finale right now and will not even be opening Logic for the next 6 weeks or so. However, I think what i would do is:
1. set up a stereo track
2. put on a 1Khz sine wave pulse lasting about 1/2 second then 1/2 second pause
3. automate pan so that each pulse is left then centre then right then centre then left and so on.
4. Note whether left and right sound more distant (quieter) or whether left/centre/right sound equal.
5. Bounce the track
6. play the track bounce in Finder or iTunes which don't have a pan law setting. Is it the same?
7. Import the bounce into a new Logic song and do another aural check, switching between finder and Logic.
8. Change the Pan law settings in Logic to see how they compare with the bounced file in the Finder as a kind of control
9. Bounce with other pan law settings.

I think a pattern should soon become clear.

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Answer 2

Javier72 Author

Level 2

494 points

Jun 21, 2007 10:10 AM in response to KOROS

Ha. Good to hear from you again, Koros. I was hoping you'd chime in. 🙂

Yesterday (and prompted by your other helpful post) I did something similar to what you've suggested on here. Instead of taking one signal and automating a pan curve, I took one signal and copied it three times atop itself with three different pan settings:

track 1=center
track 2=far left
track 3=far right

I'm going to, however, also try your suggestion and see if it gets me any further. For the moment I've been plugging away at this for quite a few hours now, and am going to take a quick work out break. I will return afterward and continue the detail on the issue. 🙂

Thanks for posting so promptly.

Javier

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Answer 3

Jun 21, 2007 11:16 AM in response to Javier72

Hi!

A pan law of -3db takes the center pan and drops it
-3dB while leaving your left and right pan signals
the same.

No, wrong. The center level stays the same, left and right are dropped by -3dB.

A pan law of -3dB Compensated leaves your center pan
the same, and RAISES your left and right pan signals
+3dB.

Not exactly, it's the same scheme as above, but all levels are raised +3dB afterwards.

Best,
21th

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Answer 4

Jun 21, 2007 1:45 PM in response to 21th Century

Did you test this before posting ?

The original poster is correct. A pan law set to -3 will drop center panned signals by 3db at the output. Signals panned left and right will not be affected.

A pan law set to -3 compensated will boost left and right panned signals by 3db at the output. Center panned signals will not be affected.

-GK

Hi!

A pan law of -3db takes the center pan and drops

it

-3dB while leaving your left and right pan signals
the same.

No, wrong. The center level stays the same, left and
right are dropped by -3dB.

A pan law of -3dB Compensated leaves your center

pan

the same, and RAISES your left and right pan

signals

+3dB.

Not exactly, it's the same scheme as above, but all
levels are raised +3dB afterwards.

Best,
21th

2 x 2 G5, Logic Pro 7, 2408 mkIII + 308, UAD x 3, Powercore PCI Mac OS X (10.3.9)

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Answer 5

iSchwartz

Level 5

4,321 points

Jun 21, 2007 2:04 PM in response to Grassrootking

This topic has gotten a lot of play on the forum, and there's still a lot of confusion on the issue.

Why not let's start from how the manual describes this function, and if there's an error in their explanation then we can explore that.

The following is taken directly from the "Late Breaking News" section of Logic's .pdf-based manual/help...

==========================================

Pan Law
The Pan Law value determines the amount of volume reduction to mono signals that are panned to the center position. If set to 0 dB, mono signals will seem louder when panned to the center position, in comparison with extreme left or right pan positions. If set to either –3 dB or –3 dB compensated, mono signals will seem equal in loudness, regardless of their pan position:

• –3 dB:
A full scale mono signal (0 dBfs) will have a level of –3 dB when panned to the center position.

• –3 dB compensated:
A full scale mono signal (0 dBfs) will have a level of 0 dB when panned to the center position (or +3 dB when panned to extreme left or right positions).

Songs created in older Logic versions always use the 0 dB option. Please note that switching the Pan Law value to –3 dB will change the mix of such songs!

==========================================

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Answer 6

iSchwartz

Level 5

4,321 points

Jun 21, 2007 2:06 PM in response to iSchwartz

I think it's interesting to note that this explanation refers only to mono signals. How the the pan law setting affects stereo signals (where, in essence, the pan pot becomes a balance control and not a pan pot) is, I think, definitely worthy of exploration and explanation.

Tawk amongst yaselves... Discuss!

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Answer 7

KOROS

Level 2

290 points

Jun 21, 2007 2:24 PM in response to iSchwartz

Thanks iSchwarz

so, I was partly right, but only in reference to panning mono channels. That figures, cos I nearly always use stereo channels and had never encountered a problem.

This will also explain why an imported bounce, being stereo has no problems.

All clear now.

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Answer 8

Javier72 Author

Level 2

494 points

Jun 21, 2007 2:42 PM in response to 21th Century

Hello, 21. You're saying that a pan law of -3dB keeps your center the same and DROPS your left and right -3dB? Then that means that your center is 3dB LOUDER than your left and right pans. If that's the case, then the perceived center loudness get even LOUDER - undermining the objective of Logic's pan law, i.e. making the pan spectrum smoother by accounting for the fact that we tend to perceive center signals as being LOUDER than left right signals.

As far as what you seem to mention regarding what Logic does in the -3dB Compensated scheme . . . well . . . same thing I just said I think might apply.

By all means let me know if I'm misinterpretting or getting something incorrect.

Thanks.

Javier

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Answer 9

Javier72 Author

Level 2

494 points

Jun 21, 2007 2:44 PM in response to Grassrootking

Ah. Okay. Looks like rootking's agreeing with me. I'm reading these posts and responding to them one at a time, so sorry for the possible redundancies on my part. 🙂

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Answer 10

Javier72 Author

Level 2

494 points

Jun 21, 2007 3:05 PM in response to KOROS

Okay, Koros. Are you saying that when you import a stereo bounce you've not encountering the perceived center loudness? If so, I'm not seeing/understanding why you WOULDN'T.

Or is it ONLY with mono signals that one encounters the perceived center loudness?

Ahhh . . . maybe that IS the case, since, as iSchwartz mentioned, mono is one signal that DOES get panned left/right, while stereo is NOT panned at all, but simply raises and lowers the volume of the left signal verses the right signal. Is that correct? If it is, then in a stereo channel, you really DON'T have any signal going through the center per se. It seems like it is but only because you're hearing it out of both speakers, and the levels of the left v right signal of a stereo channel get, again, raised and lowered in accordance with whether you're panning it left or right . . . but in a stereo signal you're never actually having a signal (mono or otherwise) traversing the center pan. Right?

Hmmm . . . But let's say you have a sequence with many tracks - some of which are stereo channels and some of which are mono . . . Is it correct to say that although your stereo channels won't suffer from the perceived center loudness, your mono tracks WILL, and you should therefore give your entire sequence a pan law of -3dB or -3dB Compensated in order to address the fact that your mono signals will appear to sound louder at center pan than at left or right?

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Answer 11

Jun 21, 2007 3:07 PM in response to Javier72

Hi javier, logic's manual doesn't fully 'splane this - probably because the writers assumed some form of audio engineer skill in the end user. oh well, another thing apple's gotten wrong.
anyway, there's a 6db difference between the mid and side signal normally when summed to mono. the mid raises and the side lowers.
fact: with stereo, a mono signal, dead centre, is at an identical level in both of the side signals. the only truely mono signal in stereo is one that's on the far left or right. as you pan, the signal creeps into the other channel gradually.
a more important issue is phase and anti-phase. positive phase (0deg) with all signals is generally a very good goal.
anti-phase will creep in anytime a mic is used, so everything in the real world contain both phase and anti-phase components.
reverbs like Space Designer add a lot of anti-phase info. check this with logic's multi-meter.
in fact RN Inspector XL, has a proper mid-side meter and typically there's 6db difference between them. if the side signal get too loud, your image will widen but will not be as mono compat. in reverse, too much mid signal will narrow the mix. a happy medium is, you guessed it, 6db.
i switch off logic's PL, and use the one in Sonalksis' Free G.
this is set to -6db!
it's not compensated, so i raise the pre gain (trim) by 6db on the plug.
my mixes sound right in both stereo and mono.
best, david r.

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Answer 12

Jun 21, 2007 3:09 PM in response to Javier72

Which setting makes it easier for you to get the mix you want?
Take a simple tune that uses mono and stereo tracks and try mixing it using all three settings and then pick the one you like to work with. I use the -3db compensated because when I pan mono tracks around, the volume seems balanced. When I import stereo tracks, they're panned hard and sound fine with no difference to level.
I use the direction plug-in with stereo tracks when mixing so I have better control over spread width and placement.
Put a meter on your master so you know where you're at level wise and use whatever makes it easier to get where you want to be.

Also, I would find it hard to live without my Logitek old school VU meters with real needles.

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Answer 13

David_Pye

Level 4

2,325 points

Jun 21, 2007 3:24 PM in response to David Robinson9

i switch off logic's PL, and use the one in
Sonalksis' Free G.
this is set to -6db!

Hi David, just wanting to check something with you here.
Above, someone reminded us all that logic's own pan law does not apply itself to stereo tracks. Only mono ones being panned. But when using something like Free G to change the pan law on the master output, does this not apply itself over every channel you put through it? So it would apply a 6dB Pan Law, to a stereo mix imported into the arranement if you put it on the master again, whereas logics own would not? This mix you may have used a 6dB pan law on in the first place so you'd be affecting the width for a second time?
Surely this would never be desirable, and if you were using any stereo tracks such as synths, ultrbeat, stereo micing, these would all be altered where they should not be?

I don't know why anyone would want to use anything other than 0dB pan law, and just work around it. If you mix sounds good then it sounds good. When you pan something you then set it at the correct level anyway, I don't want logic to adjust any levels for me.

Also, would something that was only panned 50% left be altered by only half the amount, 1.5dB in logics case or 3dB in the Free G 6dB pan law? Or is it ONLY affective when something is hard panned?

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Answer 14

iSchwartz

Level 5

4,321 points

Jun 21, 2007 3:27 PM in response to David_Pye

I've settled on -3dB compensated because a) my mixes sound better and b) when I pan something its relative volume doesn't change. Regarding 'b', that's something that's bugged me for years, having to re-balance mixes because I put something off a little bit to one side. So for me the -3dB compensated is a bit of a godsend and the 0 dB setting no longer an option. But of course, to each his own when it comes to this stuff.

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Answer 15

Javier72 Author

Level 2

494 points

Jun 21, 2007 4:05 PM in response to iSchwartz

But, iSchwartz, doesn't -3dB Compensated, in raising the left right signals, increase the overall level of your mix? I was thinking -3dB seemed to aproximate the 0dB level a little more in that the overall volume of one's mix doesn't seem to increase, but, instead, just drops the perceived loudness of the center a bit.

Just wondering.

I ask because, through the miriad of questions I may have, I would be much interested in continuing to garner advice from the experienced people on this forum.

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