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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

Best reply

KOROS

Level 2

290 points

Posted on Jun 21, 2007 10:00 AM

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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57 replies

Javier72 Author

Level 2

494 points

Jun 21, 2007 4:09 PM in response to David Robinson9

Hello, David. Thank you for posting, sir. I'm trying to wrap my mind around your post. I'm not doing a very good job of it, however.

You say there's a 6dB difference between the mid and side signals? I thought it was 3dB?

I guess I'll keep my present inquiry limited to this one question, and go from there after we deal with it. 🙂

Javier72 Author

Level 2

494 points

Jun 21, 2007 4:31 PM in response to iSchwartz

Wow. Awesome. Nothing like running some tests before you go running your mouth. iSchwartz, scratch my last post to you. I just finished donig a Pan Law test using a sine wave as my mono signal, and I stand very much corrected.

There is no real perceived difference in volume level between 0dB and -3dB Compensated. The difference in level , contrary to what I thought in the post above, was actually between the Pan Law of 0dB and that of -3dB. When compared with 0dB, -3dB was actually significantly lower in overall volume than -3dB compensated.

Learning every day. 🙂

Javier72 Author

Level 2

494 points

Jun 21, 2007 4:51 PM in response to David Robinson9

And yes, Mr. Robinson. It seems one has to have some serious audio engineer abilities in order to understand a lot of the intricacies in Logic.

sigh . . .

I'm getting it, slowly but surely (and with the help of everyone here) . . . but to say the route has been (and still is) circuitous . . . is, to put it mildly, an understatement.

Jun 21, 2007 8:34 PM in response to Javier72

I can get a great gtr tone out of any amp.
I just start turning all the knobs to their extremes to see what they do, and then I try to find the sweet spot. Then I move on to the next knob and do the same thing.
You should try that with Logic. Don't worry about the numbers too much. Just move things around until you get closer to the sound you like. At the end of the day you'll probably find that you're using the same techniques as other users.
And if not, then that's great too!

Javier72 Author

Level 2

494 points

Jun 21, 2007 8:49 PM in response to guavadude

Thanks, guava. I guess I picked a rather difficult project to begin learning Logic on, however. I'm doing the sound design, scoring and full mixing of a feature length film on it. It's daunting, but I'm getting it done slowly.

Jun 21, 2007 9:03 PM in response to Javier72

Ouch! Well then by all means you need to prioritize. The pan law is the least of your problems since all three settings will get you to the same place....you might have to adjust the volume fader as you pan, that's all. My advice is to set it to -3db compensated for this project. If you're more of a composer than a mix engineer, concentrate on that. You can alway hire someone to help you mix or do the sound design. Finding someone to compose with is a bit trickier.

Don't get hung up on the details right now. good luck

iSchwartz

Level 5

4,321 points

Jun 21, 2007 10:34 PM in response to Javier72

Javier,

I "discovered" the benefits of -3dB compensated one day when I got sick and tired of having to re-adjust levels when I'd pan things wide. I just changed from 0dB to -3dB compensated and, voila, my problem was solved. I've since set all of my template songs to -3dB compensated and I only work in that mode.

Jun 21, 2007 10:50 PM in response to David_Pye

hi, once only for any PL unless you're after a sfx.
there are so many shapes and values PL can take that there really isn't one answer.
the width question? you got it backwards. the more the center drops in level, the wider things will sound, if the levels match.
i suspect that the differences the users find between DAWs as to stereo is to do with PL.
recording live in a good room is an art form in itself. done plenty - big rooms, great sound and no real phase probs. but once you set up the mics, that's it.
anything added with another set up in that same room, will sound false and cause phase probs, comb filtering and other nasties. this is why some orch samples libs are superior to others.
if you try to widen a true stereo signal, it'll fall apart.
i truly believe that widening can be better achieved by narrowing stereo signals within a mix.
most drum libs are very wide eg: toms. the scale is wrong. narrow this down to under 50% so that a tom fill sounds smaller - put the kit in wide mono.
the benefit is that other sounds can be place "outside" the drums. percussion or metal pwr chrds work well. iow, use the instruments to widen the image, don't let the image "widen" the instruments (tip: it's in the arrangement).
best, david r.

Jun 22, 2007 6:49 AM in response to iSchwartz

&> Javier,

I "discovered" the benefits of -3dB compensated one

; day when I got sick and tired of having to re-adjust

levels when I'd pan things wide. I just changed from
0dB to -3dB compensated and, voila, my problem was
solved. I've since set all of my template songs to
-3dB compensated and I only work in that mode.

Same here. That and the use of the Direction Mixer plug-in on stereo tracks have made my mixes much better.

Javier72 Author

Level 2

494 points

Jun 22, 2007 8:42 AM in response to guavadude

"The pan law is the least of your problems since all three settings will get you to the same place....you might have to adjust the volume fader as you pan, that's all. "

Well, guava, I wish this indeed seemed like the case with me, but part of the reason I actually started this post is because of some of the issues that I explain to iSchwartz below. Read on. 🙂

And regarding working with/hiring another/assistant mixer/sound designer . . . well . . . I wish that was in the budget, so to speak. 🙂 Maybe for the next film. For now, I have to figure everything out on my own - which is not the most horrible thing in the sense that, difficult as the process is/has been, I'm acquiring a skill set that will allow much more empowerment for future projects.

Javier72 Author

Level 2

494 points

Jun 22, 2007 9:03 AM in response to iSchwartz

You, know, iSchwartz, although I did some PL tests, and although those test - using as my sound source something as simple as a basic sine wave - showed the surprising results that I previously mentioned (-3dB Compensated actually seeming to be more closely resembling 0dB in its final level than did -3dB), when I went to take this knowledge and applied it to my actual scoring sequence, the project itself didn't end up responding to the Pan Law settings in the same way AT ALL.

Perhaps it was because whereas the PL tests I did referred only to a one track mono sine wave, the sequences I'm applying these things to are oftentime have over fifty tracks with almost every type of pan automation curve you can imagine and have tons of effects spanning over an array of both mono AND stereo tracks.

What ends up happening is that when I go from a PL of 0dB to -3dB Compensated, my center signals (usually mono audio tracks comprising actor voice overs, but also including mono and stereo folies and sound effects in there as well) seem to boost quite a bit and I notice certain anomalies which make me cringe a little. I do realize, again as we established earlier, that -3dB Compensated does nothing to the center signal. It doesn't actually boost it, but, instead, raises your left and right signals 3dB. All the same, I can certainly hear the fact that when I go from, say, 0dB to -3dB, the overall level of the mix seems to even out a little bit better than at -3dBC.

Anyway, perhaps -3dB is the setting for this particular project, and -3dBC may work better for some others.

Javier72 Author

Level 2

494 points

Jun 22, 2007 9:11 AM in response to Ashermusic

Man, I'm going to have to revisit the direction mixer again. I looked at it yesterday and did a little testing on it for the first time while reading the logic plug in manual as well, and there were a few things that REALLY threw me off.

This of course, however, is an issue for another topic. 🙂

Jun 22, 2007 9:31 AM in response to Javier72

I think you just need to mix more and you'll get a better understanding of the different "pan laws", or as suggested, use -3db compensated and get on with your life. You have bigger fish to fry so to speak.

Let's say you have a mono gtr track panned in the center and you decide you want to move it to the left a little. If you use -3db comp, then you just move the fader and the volume will stay the same. If you use the other laws, you will have to adjust the volume every time you pan something which will take longer.

So think of it as an easy way to get more time to compose, which is way more important. If your score is lame, no one's going to care how the gtrs are panned.

I'm a firm believer in reading the manual, but at some point you have to start turning the knobs.
good luck

Javier72 Author

Level 2

494 points

Jun 22, 2007 9:38 AM in response to guavadude

Thanks for the advice, guava. I'm a HUGE "doer". In other words my philosophy had always been "just go in there and DO IT!" lol. Idiot savant all the way (more idiot than savant in my case though). This project has been so involved and voluminous that I HAVE indeed kind of lost myself in the technical minutia, however.

S'always good to have some people punch you back into reality and remind you that it's about the art and the creation.

Thanks.

Javier72 Author

Level 2

494 points

Jun 22, 2007 9:44 AM in response to Javier72

Okay. One last question to conclude this very helpful post: What is the "Playback Pre-roll" button for in the Pan Law dialogue box? I usually have this unchecked . . . but have no idea what it does one way or the other.

Thank everyone.

Javier

Pan Laws and Bounce Tests