Is this really how Pro Tools does panning? Take the test

[adpz]

Something has been bugging me about the panning inside Pro Tools (HD). I finally ran some tests. I made sound clips of 5 different pan positions, with nothing being different other than the pan position. Once the pan was set, I bounced a small section to disk. If anyone's in the mood, take a listen to the file below (mp3) and you'll hear the same slice at 5 different pan positions.

The first one is 100 hard-left. What would people think is the approximate location of the other 4. I'll reveal the answers after some feedback. Listen on speakers or phones . . .

[paul101]

All vaguely left-ish.

For me it just highlights the pointlessness of non LCR panning.

[adpz]

That's just it; outside of PT I don't think these pans would be so vague or seem random (even though they are all left).

[BLueROom]

within 100-80% left?

[paul101]

This thread may be of interest.



An Interesting Excerpt On L-C-R Mixing - The Womb

[adpz]

The difference is much more "visible" on phones. But I would agree with Paul's link that, at least ITB, there are really only 5 valid positions: L CL C CR R.

[BluegrassDan]

100%
85%
75%
65%
50%

[adpz]

So maybe there will be more reactions to the reality:

The pans are a linear move from Hard Left 100, as so:








100 - 96 - 93 - 89 - 86

What surprised me is how non-linear the progression sounds. I termed it lumpy. I also find that 96 and 93 sound basically the same, as do 89 and 86, while 93 and 89 make for a jump. Obviously, we could test it across the spectrum, but who's going to listen to that

For me, the point is that the panning jumps away from the left speaker very quickly - even at 96 - and then moves in a lumpy fashion quite quickly toward the middle. Of course, this is a lot easier to hear on phones. On speakers they all sound basically the same - probably due to how little signal is driving the opposite side.

I'd love to know the quality of that opposite signal, b/c it is very low-level, low resolution - not digital's strongest playing field.

[adpz]

Originally Posted by BluegrassDan

100%
85%
75%
65%
50%

Very interesting BGD. Where you listening on phones? You may be surprised, as I was, that that last one - which has some affinity for the 'center' is actually 86 left.

[lerone]

Definitely have to agree on this one. Just not the same as a board is it..

Toby

[BluegrassDan]

Yeah, I was listening on phones and taking a stab in the dark on my home pc.

I was thinking the last was somewhere right between L and C. However, after listening to a reference CD I have better bearings.

I've been getting used to PT at our new studio. I find that I do better when I close my eyes and turn the console knobs rather than use the mouse and "look". Sometimes I end up dialing things in almost exactly where I expect them, and other times I'm REALLY surprised.

[Tony Shepperd]

You see, you haven't changed the pan law inside Pro Tools yet.
So instead of the Stereo mixer, use the Surround mixer (non dithered).
Now instead of BTD run it out of Pro Tools (analog) and then back in and Record to Disc, using those same guitar files as you did before.

Now, post those results.

[adpz]

Originally Posted by Tony Shepperd

You see, you haven't changed the pan law inside Pro Tools yet.
So instead of the Stereo mixer, use the Surround mixer (non dithered).
Now instead of BTD run it out of Pro Tools (analog) and then back in and Record to Disc, using those same guitar files as you did before.

Now, post those results.

Wow - excellent thought. I am going to try that tonight. Will the results be influenced just by the different pan law that the surround mixer uses? Thanks for the idea

[Tony Shepperd]

Originally Posted by adpz

Wow - excellent thought. I am going to try that tonight. Will the results be influenced just by the different pan law that the surround mixer uses? Thanks for the idea

The short answer is... yes!

[Lynn Fuston]

EDIT: Changed my mind about replying.

[gainreduction]

The pan law in the surround mixer is different (by 0.5dB or so) and will of course affect the behaviour of the pan slider. As the center is a little lower (or the sides louder) it will feel like the pan travels a little longer, or sound wider if you will.

[BluegrassDan]

Originally Posted by gainreduction

The pan law in the surround mixer is different (by 0.5dB or so) and will of course affect the behaviour of the pan slider. As the center is a little lower (or the sides louder) it will feel like the pan travels a little longer, or sound wider if you will.

And how does this translate, for example, when bouncing to disk? Does it work and act more like an analog console? Do you recommend working and mixing all the time with the surround mixer setting?

[okydoky]

Originally Posted by adpz

I'd love to know the quality of that opposite signal, b/c it is very low-level, low resolution - not digital's strongest playing field.

hi,

that is one real nasty issue that is often overlooked. when you have "almost hard left" or "almost hard right", the opposite channel will be degraded in pro tools [and other current daws, as far as i know]. in some circumstances it sounds really bad.

it has not always been the case, though. early on, the problem was recognized and dealt with. for example. synclavier's panning was analog, after the d to a, so that digital resolution was good in both channels.

many compromises were made in order to bring digital recording's price down to a larger market.

better panning and resolution is one of the advantages of mixing out of the box.

it seems to me that this is one issue that could be fixed by digidesign [and / or other daws] with hardware upgrade[s].


right.

[gainreduction]

Originally Posted by oky****

hi,

that is one real nasty issue that is often overlooked. when you have "almost hard left" or "almost hard right", the opposite channel will be degraded in pro tools [and other current daws, as far as i know]. in some circumstances it sounds really bad.

That is one of the reasons why the dithered mixer exists in ProTools. You get "dithered 24 bit resolution" all the way down to the noisefloor instead of distortion. This includes every part of the mixer, aux sends and all.

With the dithered mixer there should not be audible degradation of low level signals. Especially since ProTools has "foot room" aswell as headroom in its 48 bit fixed point processing.

[gainreduction]

Originally Posted by BluegrassDan

And how does this translate, for example, when bouncing to disk? Does it work and act more like an analog console? Do you recommend working and mixing all the time with the surround mixer setting?

Just try both and see which one you like better, there´s no right or wrong here.

[okydoky]

Originally Posted by gainreduction

That is one of the reasons why the dithered mixer exists in ProTools. You get "dithered 24 bit resolution" all the way down to the noisefloor instead of distortion. This includes every part of the mixer, aux sends and all.

With the dithered mixer there should not be audible degradation of low level signals. Especially since ProTools has "foot room" aswell as headroom in its 48 bit fixed point processing.

hi,

no, it actually does not work like that, although the dithered mixer may have some other advantage over the non-dithered mixer.

the solution is to pan outside the box.


right.

[gainreduction]

From digi´s white papers:

A BIT OF DITHER

There is a dithering stage in most double precision plug-ins
and one final dithering stage at the post master output of the
summing mixer. Dither is noise with very specific properties
added to the signal in order to de-correlate the noise floor
from the original signal so that when length reduction
occurs, the resulting waveform does not contain any
harmonic distortion or noise floor modulation artifacts.
This allows the plug-in and the mixer to perform very
precise calculations while maintaining the low level detail
when handing the signal off to the next process. Within
the Pro Tools TDM mixing environment, when the dithered
mixer is used, dither is added to the 48-bit signal before it
is reduced to 24 bits to be placed back on the TDM bus and
sent to the DACs. Dither is not added on a track by track
basis, as this would produce unwanted accumulated noise.
Dither is only added once at the Master Fader output of the
mix bus so the total system dither noise is 3 dB at -144 dB.
“Not so fast!” you say. “You just added noise to my signal and
truncated my word from 48 bits to 24 bits—I’ve been robbed!”
Well, it’s true that within this system topology, the signal must
be 24-bit in order to pass from DSP to DSP via the TDM bus,
but it’s important to understand that the level of the dither
added to the signal is around -144 dB, which is below the
noise floor of the converters. Consider that our ears can deal
with a dynamic range of around 120 dB (from the threshold
of audibility to the threshold of pain). This gives you an idea
of how low “-144 dB” is in terms of audibility—you’d have to
have your monitor system cranked up to extremely high levels
to even hear any sound that might exist in a noise floor this
low. The same could be said about the loss of the lower 24 bits.
The sample values represented by the lower 24 bits in a 48-bit
word are between -144 dB and -288 dB, so the dither only
affects the signal at -144 dB or lower.

THE PRO TOOLS 48-BIT MIXER PLUG-IN

Just as EQs, dynamics, and reverbs are plug-ins, the Pro Tools
Dithered Mixer is a plug-in as well. It differs from most other
plug-ins in that it can grow to span multiple DSPs and as it
grows, it passes signal from DSP chip to DSP chip at a full
48 bits instead of dithering and truncating back to 24 bits.
It does so by using two 24-bit TDM timeslots per connection.
This enables the mixer to maintain an internal dynamic range
of at least 288 dB from beginning to end.
The extra 24 bits in the system are used to provide channel
faders with additional dynamic range above and below the
original 24-bit word, and it guarantees that the same fidelity
is maintained when adding more inputs to the mix bus. In the
Pro Tools +12 mixer, 9 bits are reserved for levels above 0 dBFS,
providing 54 dB of headroom. This is enough headroom to
allow 128 tracks of full code, correlated audio (imagine sample-
aligned sine wave source files) to be summed with all faders at
+12 without clipping the “input side” of the bus. It also provides
enough bits below the 24-bit word to allow channel faders to
be placed at nearly -90 dB before they stop contributing a full
24 bits to the mix.
Since in the real world, audio signals are almost never exactly
correlated in this way, you can mix a far larger number of
inputs within the Pro Tools mixer without clipping the “input”
side of the mix bus at all. You can clip the “output” side of
the mixer, but that’s what Master Faders are for—they allow
you to trim your final output level to avoid clipping the DAC
or 24-bit digital output when your mixed signals leave the
Pro Tools mix environment. This is analogous to an analog
console mix bus, where you trim the master bus with a master
fader to avoid clipping the output circuitry in the console.
Similar to analog mixers, the Pro Tools mixer is comprised of
individual input channels and a summing stage. At the input
stage, each channel’s 24-bit word is multiplied by 24-bit gain
and pan coefficients to create a 48-bit result. The new 48-bit
word contains the original 24 bits “shifted” lower in the 56-bit
register to allow for headroom and “footroom” below unity
gain, enabling channels to be turned down without losing
precision. Specifically, it’s possible to pull any channel fader
down to -90 dB and its signal still retains 24 bits of precision.
As channel faders are pulled down, there is a loss to the lower
bits of the newly extended 48-bit word which represent signals
down to about -240 dB—but a full 24 bits of precision is main-
tained down to -90 dB.
It’s important to understand that while some lower bits
of the 48-bit word are truncated when reducing individual
channel levels, the quantization (or rounding error) that
occurs when they are lost adds about one millionth of a
dB to the total quantization error. This is determined by
adding the quantization noise from the single precision
quantization to the quantization noise of the double preci-
sion quantization. For example, when the mixer represents
-144 dB, the actual value is more like -143.99999 dB and it
is quantized to -144 dB. The difference is about one millionth
of a dB and is astronomically close to the “ideal” mixer—
one that doesn’t ever lose bits internally.
At the summing stage, Master Faders perform in a similar
way to channel faders in terms of resolution. The final gain
stage is in effect a master fader, which is always present;
and, when the Pro Tools UI displays a Master Fader, the user
is given a “handle” to adjust the range of the final gain stage
output. As a built-in part of the mixer, Master Faders don’t
consume any additional DSP resources, so they are the best
way to adjust the final output of an internal bus or external pair
without losing precision.

[gainreduction]

Originally Posted by oky****

hi,

no, it actually does not work like that, although the dithered mixer may have some other advantage over the non-dithered mixer.

the solution is to pan outside the box.


right.

If I understand digi´s white papers right the internal headroom of the PT mixer is 288dB the way it is setup using double precision math, 48 bits. The noisefloor is at -144dB. The dither applies to the lower 24bits of the 48bit word.

This means any signal is at full 24bit resolution down to -90dB (which is a quite typical noisefloor in an analog system) and the degradation after that affects only the lower 24bits (of the 48bit word) (which is where dither is applied).

This *should* apply to panning too. Only when one channel is down below -90dB (which is close to silent) can degradation theoretically occur.

I don´t think the average analog panpot performs much better.

Please enlighten me what I´m getting wrong, I want to learn more about the digital process.

Peace.

[okydoky]

Originally Posted by gainreduction

From digi´s white papers:

A BIT OF DITHER

There is a dithering stage in most double precision plug-ins

THE PRO TOOLS 48-BIT MIXER PLUG-IN

hi,

48-bit mixer, at page 6.

"We should take a moment to distinguish between the result of lowering a fader within the context of the internal mixer (where 48-bit precision is maintained) and lowering the level of a signal that is being sent to a DAC output.

As with any digital audio system (not just Pro Tools), if you
lower a fader assigned to an individual DAC output you can
lose resolution and dynamic range, as you are simply reducing the number of bits representing the output signal in comparison
to the DAC’s theoretical 24-bit resolution. You would be throwing away dynamic range that the DAC can represent
if you, say, pulled your fader down to -14 dB and left it there
so that peaks hitting the converter were far below full scale. That would decrease your signal-to-noise ratio significantly,
so optimizing signal levels going to individual DAC outputs is important to preserving signal quality—you want to get as much resolution out of the DAC that it can offer before clipping to take maximum advantage of its dynamic range performance."



also, even within the tdm environment you are exceeding the [purported] -90 dB leeway in many panning scenarios. there is more to it as well.

dither is not the be all and end all.

panning is better done outside the box.


right.

[gainreduction]

Cool, I was just thinking about the PT internal mixbuss not taking the DAC resolution into the equation. That, of course matters a lot.

Thanks for clearing that up.

[RKrizman]

Originally Posted by oky****

hi,

48-bit mixer, at page 6.

"We should take a moment to distinguish between the result of lowering a fader within the context of the internal mixer (where 48-bit precision is maintained) and lowering the level of a signal that is being sent to a DAC output.

As with any digital audio system (not just Pro Tools), if you
lower a fader assigned to an individual DAC output you can
lose resolution and dynamic range, as you are simply reducing the number of bits representing the output signal in comparison
to the DAC’s theoretical 24-bit resolution. You would be throwing away dynamic range that the DAC can represent
if you, say, pulled your fader down to -14 dB and left it there
so that peaks hitting the converter were far below full scale. That would decrease your signal-to-noise ratio significantly,
so optimizing signal levels going to individual DAC outputs is important to preserving signal quality—you want to get as much resolution out of the DAC that it can offer before clipping to take maximum advantage of its dynamic range performance."



also, even within the tdm environment you are exceeding the [purported] -90 dB leeway in many panning scenarios. there is more to it as well.

dither is not the be all and end all.

panning is better done outside the box.


right.

I don't think your analysis supports your conclusion. As long as you remain ITB then you are not losing dynamic range. Only when you go out your converters do you lost bit depth. Therefore, for the best low level resolution, required for convincing panning, it makes more sense to stay ITB, when your depth of resolution far exceeds analog.

I don't have any trouble panning in PT, and have no trouble in getting a very wide stereo field. And I like the fact that every time I call up the mix every subtle little thing I did to create the stereo field pops up exactly like I left it. Spatial positioning is about way more than just twisting a pan pot.

-R

[space2012]

panning is affected by wordclock.

101010101010101
LRLRLRLRLRLRLRLR

jitter makes harder for the AD/DA chip to know whats L or R.

take for example the Lavry gold vs. Apogee ad-16x here in gearsluts:
http://www.gearslutz.com/board/3134913-post67.html

Files:
http://www.gearslutz.com/board/attac..._-1.3dbwav.wav
http://www.gearslutz.com/board/attac..._rc-1.25db.wav

answere:
5.1 Lavry Gold mk III
6.1 Apogee AD-16x
http://www.gearslutz.com/board/3535201-post74.html

also...
RME mixer has panning LAWs, with single channel:
-4.5 dB gives a flat L to R.
-6dB gives a low center.
-3dB gives a loud center.

Linear or Logarithmic ?
is another variable.
thers positive log, negative log, parabolic, convex, tactrix, etc...

panning is easyer to hear in triangle speaker placement.

[monomer]

Human ears experience position in a number of ways, of which sound energy is only one.
And , sorry to say, panning is not the most important one in many cases.
Filtering by the pinnea and inter-aural time differences give us the majority of spatial cues.

I once heared an audio file that proved this very directly.
There is this psychoacoustic effect where your brain persistently thinks a sound is located at the side where is has first arrived.
This soundfile had a short burst of a sound on one channel.
While the burst was taking place the same sound started on the other channel.
This other sound, however, continued on after the first stopped.
What i (and i guess most people) heared was a continuous sound comming from the side that the short burst had played from.
The illusion would only dissapear after a few seconds and i could hear the sound pan to the other (correct) side.
weird stuff.

What i want to say is that there is a lot more to sound localization than pan potting.

[Clueless]

Originally Posted by space2012

panning is affected by wordclock.

101010101010101
LRLRLRLRLRLRLRLR

jitter makes harder for the AD/DA chip to know whats L or R.

I never knew that. Can you please tell me what happens when panning in 2.1?

What about 5.1?

What about 7.1?

Inquiring minds want to know!

[okydoky]

Originally Posted by RKrizman

I don't think your analysis supports your conclusion. As long as you remain ITB then you are not losing dynamic range. Only when you go out your converters do you lost bit depth. Therefore, for the best low level resolution, required for convincing panning, it makes more sense to stay ITB, when your depth of resolution far exceeds analog.

I don't have any trouble panning in PT, and have no trouble in getting a very wide stereo field. And I like the fact that every time I call up the mix every subtle little thing I did to create the stereo field pops up exactly like I left it. Spatial positioning is about way more than just twisting a pan pot.

-R

hi,

well, first off you are not going to reasonably be able to limit all your work to "in the box", unless you are willing to totally cripple your options all the time and forever. in the box is alright, and i am sure you can get some nice results that way with certain types of projects, but it is no substitute for a more complete system.

at some point in the process, most professional work will involve multiple d to a converters and a console, with hardware outboard and so forth. this is a fact, not reasonably subject to dispute.

next, even "in the box" you are susceptible to running into issues with panning, because when you start pulling back individual channel pairs while doing panning that is not center or hard left or right [say 90 - 95% or something of that nature], you get into a scenario where the "weaker side" of the panning is effectively less than 90dB down. note that this is giving full faith and credit to digidesign's claim that one can pull an individual fader back "almost 90dB" and have the fader "still contribute a full 24 bits" [whatever that vague statement may be taken to mean].

you should know that the claim of being able to pull faders back "almost 90 dB" is kind of widely taken with a grain of salt, and it does not necessarily take everything relevant into consideration.

if i remember correctly, all of digidesigns measurements and claims are very careful to specify in writing that they are taken with the signal hard panned to one side or another.

additionally, if you are doing some sort of 2 channel "bounce everything in the box straight to disk without ever leaving the box" routine, i wonder what happens to all of your attenuated panned channel signals when they are bounced?



right.