QLab Volume Limits

[David Meissner]

I'm trying to calibrate our sound system for QLab by setting the maximum and minimum volume limits under Settings -> Audio. On both QLab 4 and OLab 5, I have tried to set the minimum limit to -25 dB, but QLab resets the number to -40 dB as soon as I exit the field. Is -40 hard-wired to be the minimum allowed setting? Is there any way to change this?

Thanks in advance,

-David

[Sam Kusnetz]

On May 3, 2023 at 11:38:44 AM, David Meissner <dme...@gmail.com> wrote:

I'm trying to calibrate our sound system for QLab by setting the maximum and minimum volume limits under Settings -> Audio. On both QLab 4 and OLab 5, I have tried to set the minimum limit to -25 dB, but QLab resets the number to -40 dB as soon as I exit the field. Is -40 hard-wired to be the minimum allowed setting? Is there any way to change this?

Hi David

-40 is the highest minimum volume limit permitted, based mostly on the notion that a sound system with less than 40 dB of dynamic range is pretty unusual… even the built-in speakers on a Mac have more range than that.

Can you tell me how you arrived at a level of -25 for your minimum volume?

Best

Sam

—

Sam Kusnetz (he/him) | Figure 53

s...@figure53.com

[David Meissner]

Thanks for getting back to me. My method was to start playing a cue, then I turned down the master volume for the cue until I didn't think I could hear anything. It could be an issue with my hearing, or maybe we have some other issue in the sound system.

[Sam Kusnetz]

On May 3, 2023 at 12:27:36 PM, David Meissner <dme...@gmail.com> wrote:

Thanks for getting back to me. My method was to start playing a cue, then I turned down the master volume for the cue until I didn't think I could hear anything. It could be an issue with my hearing, or maybe we have some other issue in the sound system.

That’s the right method from QLab’s perspective, but it’s important to make sure the rest of the sound system is in good condition first. Here are some basic steps:

1. If you’re using an audio interface for output, make sure it is set to output at full volume.
2. If you’re using the headphone jack for output, make sure your Mac’s output volume is set to full.
3. On your console, make sure the channels that QLab is using are set to line level input, and their trim is set appropriately.
4. Make sure those channels are set to unity gain, and routed to the outputs you want to use.
5. Make sure the outputs are set to their usual level.
6. Make sure your amplifiers are set to the correct level for your speakers.

Only once all those things are confirmed is it time to do the level test that you described.

Let us know how it goes!

[Tom Colburn]

Thanks for the detailed list, Sam! I’ve wondered what the proper MacBook output level is and haven’t seen it documented anywhere, though I could have missed it. I think it would be good to add that info to the, “A Computer Prepares…” pages of the documentation (and/or elsewhere as appropriate):

https://qlab.app/docs/v4/general/preparing-your-mac/

https://qlab.app/docs/v5general/preparing-your-mac/

Tom

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[micpool]

I've deleted my previous comment, for 2 reasons. Firstly, because I assumed that the original post was about a special use case,  and it may just be about the  gain structure in David's system, in which case my post confuses the issue and Sam has dealt with that in his post in a more useful way.

But also because setting the maximum volume to a level less than 0dB does not work in the way I assumed, (and it is possible , not in the way it was intended as -30dB Max results in a Maximum possible  output level for a single cue of  minus 180dB FS)

I have to say I've never used a workspace with a maximum gain less than the default (+12) and have never seen anyone use a maximum gain below 0dB, so these observations may all  be a bit academic, and can probably  be ignored by at least 99.99% of users! However it is possible, in an averagely noisy room to conclude that -25 is the correct minimum level if you set your Max to -10 and hadn't double clicked the existing levels of the cue you were listening to. Although you would soon find out that a Max of -10 would produce a considerably quieter output than that level might suggest, and you would quickly restore it to 0 or above!

Changing the Max level has many strange peculiarities:

With a 0dB(FS) Pink noise signal in an audio cue, with the cue output faders,  the main fader, and the matrix in and out levels as high as they go, on any given Max Volume Setting, QLab produces the following levels metered at the device output FX point. (These levels are incorrect as we will see in a moment)

Max Setting     Meter reading

      0.                          0

     -5                        -20

    -10.                      -40

    -15                       -60

    -20.                      -80

    -30                      -120

The indicated levels are not the actual levels If you  option click twice on all the  levels to reset them, the levels change dramatically   (and sometimes the levels get completely messed up and you have to open and close the workspace to get the indicated and actual levels to align). Screen recording of this in action attached

After double clicking the actual levels are:

Max Setting     Meter reading

      0.                          0

     -5                        -30

    -10.                      -60

    -15                       -90

    -20.                      -120

    -30                      -180 

Here's a screenshot of Max set at -30 with 16 Full level noise audio cues playing. The meter in the device output only reads down to -120 so I have boosted the gain by 60dB prior to the meter reading of -90 so the actual output level is -150dB FS

Finally one other peculiarity  has come to light in my test, which I (and possibly no one else has ever noticed before)
If you use multiple effects in QLab 4 and QLab 5 device outputs,  they are chained Right to Left!

Mic

[David Meissner]

Just to close this out - thanks very much for the detailed comments. This helps with my general understanding of the issues. It may be an issue with my own hearing that I can't hear our house speakers once they drop below what QLab shows as -25, I'll have to check with other colleagues at the theatre. But I think my basic question was answered: that the minimum setting is -40 dB, which should be sufficient for a normal and correctly configured sound system.

[micpool]

I think we may have lost sight, in our detailed discussion of the mechanics of QLab's Max/Min Volume Limit settings, of why a minimum level of -25 would be considered as most unusual. 

For typical compressed pop music this would be a level setting that  should result in playback at a reasonably loud level on a well adjusted system, with a suitable output power for the room it is used in.

This level set up allows quieter, well recorded cues like solo classical piano to be set with the main slider at 0 for playback at a fairly loud volume and, assuming a maximum volume setting  of +12, gives another 12dB of potential extra gain for boosting material recorded at lower then optimum  recording levels, or for cues with extra loud transients like explosions or thunderclaps to have maximum impact.

The attached video shows the effect of  various minimum Volume limits on typical program material. All the fades are linear.   Even if you listen to this video on a phone speaker the effects of the minimum volume setting should be plainly obvious (Although listening to it on your PA will be more useful)

At -25dB the cut off is abrupt, like someone lifting a needle out of a vinyl groove.

At -40 it's not much better

at -60 the cut off sound reasonable and is a good setting for a room with an average background level e.g an air-conditioned auditorium with an audience present. 

at -80 the fade is audible for it's entire 3 sec duration, and fades gracefully all the way into the noise floor of the room

at -120 the fade sounds like it has completed around 2 secs into the 3 sec fade. This would be more problematic with long fades e.g. a 30 sec fade would result in no audibility after 20 secs.

So for most typical uses, on a well adjusted system a Max Volume setting of +12 and a minimum of  -60 to -80 should give good results. 

Mic

[David Meissner]

(Sorry, had to delete my previous message to fix a typo). 

Thanks again. I can definitely hear what you describe in the video. I suspect a problem with the operator (me) - as I mentioned, my hearing is not ideal, I'm getting up there in years and I have mild tinnitus. But in testing, I can clearly hear audio on the computer's speakers at -25, and can just hear something very faintly at -40. The problem I'm trying to solve is with my fade cues - it seems like they fade too quickly in the theatre even if I use a longer fade time. I was trying to calibrate the minimum dB for our environment to see if that solved it. I'll try a minimum of -60, and will work with my colleagues at the theatre whose hearing is better.