I set out to simply calibrate my mix monitoring level with pink noise...

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I set out to simply calibrate my mix monitoring level with pink noise...

Post by cashhewn »

Hello all,

Long post alert.

I feel like I've confused myself into a possibly needless tailspin, but I would like to emerge from this ignorance! And I suppose I need assurance that there isn't something fundamentally flawed with my studio setup in general...

I've found that I usually monitor while mixing with the main studio monitors' output pot on my analog console between about four and five (out of ten), and this usually equates to around 76dB SPL (or so) C-weighted, slow response, when measuring the program output of the console's 2-bus from the main monitors (more on the exact signal flow later). This seemed all well and good, it's a comfortable yet loud enough level to work, and my mixes have generally seemed consistent in terms of overall level. I probably should have left it here! The trouble began when I decided to try to measure the output from the studio main monitors with pink noise from the DAW...

I think the confusion for me comes in because of my convoluted signal flow and hybrid studio setup: I'm sending one track of mono uncorrelated pink noise from the DAW/DA interface to one input channel of an analog Soundcraft Series 600 console (channel fader at unity, no gain applied, bussed up the middle to the 2-mix, console master fader at unity) and from the console's 2-mix out to an RME ADI-2FS where that stereo signal is being converted AD and going SPDIF back into the interface/DAW to a stereo track running a Sonarworks plugin which is then going back out through the DA to a 2-track input on the analog console which is what I am actually monitoring (bottom line is that this setup allows me to monitor the output of the console "corrected" for my room's deficiencies using Sonarworks when I'm mixing).

Because of that signal flow and the differences in maximum input and output in dBu of the DAW/interface and the analog console and the RME converter (as well as the 7.3dB level loss from the Sonarworks correction software), I'm getting confused as what is important to measure and where. For example, -20dBFS pink noise from the DAW doesn't come back at the end of the line and hit the stereo track running Sonarworks that I am monitoring at -20dBFS, it's lower than that, but I can of course increase the output of the pink noise from the DAW above -20dBFS so that it does come back in at -20dBFS and then measure my SPL from the monitors at that point, but is that correct in terms of what I should be measuring? If I do this, then coincidentally I'm back at around 4.5 on my monitor mains pot on the console again and measuring around 76dB SPL...tail chasing...?

On top of all that, I'm noticing that when I am indeed getting -20dBFS out of the Sonarworks track and monitoring that on the analog console, my VU meters on the console are hovering around -12 or -13 VU, does that seem correct? In other words it's as if 0VU on my console corresponds more to around -10 dBFS than -20dBFS from my DAW. For what it's worth, I just sent a sine wave down the same path and when the VU meters read zero on the console I am measuring that output at around 1.2 volts RMS, so that seems correct.

Thanks for your help!
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by RichardT »

My question would be: do you actually need to do this? If you’re happy with your usual levels, and reference material sounds good, I’m not sure you need to calibrate your levels exactly. My personal theory is that we each have an optimum level for listening, and I think it varies from person to person. As long as you are able to compare your balances to good reference material, and the levels you’re using don’t damage your hearing, you’re probably ok.

Others may disagree!
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by resistorman »

RichardT wrote: Mon Jul 04, 2022 7:50 pm My question would be: do you actually need to do this? If you’re happy with your usual levels, and reference material sounds good, I’m not sure you need to calibrate your levels exactly. My personal theory is that we each have an optimum level for listening, and I think it varies from person to person. As long as you are able to compare your balances to good reference material, and the levels you’re using don’t damage your hearing, you’re probably ok.

Others may disagree!

I do not disagree :D
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by ef37a »

I do not disagree either but...

I think there is still value in keeping an eye on the levels you are monitoring at? I would say the dBu level through the system is secondary to having a consistent sound level.

You and your hearing are not 'the same' every day and you might make mix decisions when 'out of sorts' a bit that in a few days time seem poorly chosen?

Then there is 'mission creep', as you spend time at the monitors your hearing will get slightly depressed and I suspect a quick gander at the SPL meter every hour or so is no bad thing to stop you cranking the volume? Better of course to just take a break.

Dave.
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by Hugh Robjohns »

I think tail-spin is the correct description.

Your issue is that you have several different problems in the gain structure of your signal path, and that's confusing the heck out of you.

Firstly, 76dBC is a perfectly acceptable reference listening level in a small room (equating to -20dBFS in your DAW). So that's great.

Unfortunately, having the monitoring volume control on the desk around 4/10 or 5/10 is not so great as in that region you'll have stereo mistracking and poor level resolution issues. It would be far better if you could reduce the sensitivity of your monitors to allow that control to reside around 7/10 when delivering your comfortable (76dBC) reference level from the speakers.

If you can't turn the speaker's own input sensitivity down, you could buy or make inline attenuators which would solve the problem, or perhaps increase the attenuation through the Sonarworks processing.

As for the rest of the alignment process, all that matters is that -20dBFS on your final mix bus equates to your acoustic reference level. It doesn't matter what level you're pushing through the analogue console at this stage, nor what level the pink noise generator has to run at to achieve the desired goal.

That said, you'd actually make your life much easier to bypass the console part of the input signal path for this alignment process.

I'd recommend using the BlueSky calibration files as I know they are right. You can't measure the true RMS level of pink noise on the sample-peak meters in a DAW, so use a file that has been properly designed ... and the Blue Sky files have.

So all you need to do is load the file into your DAW and play directly through your output monitoring chain (and Sonarworks) into the console's monitor section and your speaker... and adjust the speaker's sensitivity accordingly with the monitoring volume control at it's reference position (ideally around 7/10, as discussed earlier).

You may well find that using the bandlimited (500Hz-2.5kHz) pink noise file gives more reliable results with your SPL meter as it neatly avoids problems with LF room resonances and HF splashes from hard surfaces like consoles!)

Once you have established a suitably calibrated relationship between the DAW's output and your speakers, you can do away with the pink noise, turn the monitors down, and align the rest of the signal path using sinewave tones. Personally I prefer working with 400Hz to 1kHz as it's less painful on the ears, but the BlueSky files only offer 1kHz.

You now need to work through your interface I/O level settings and your console input gains to achieve a unity gain signal path all the way through the chain. This may or may not be possible depending on the options in your interface...

It also depends what your console's VU meters are aligned for.

In normal professional circles 0VU should equate to +4dBu and -20dBFS... meaning that 0dBFS= +24dBu... but there are various other 'standard' calibrations that are all perfectly workable.

You mentioned an RME converter, but only the very latest ones can cope with +24dBu. Most of the older ones have an option for 0dBFS=+19dBu... and these are designed to conform to the European broadcasting standard alignment where 0dBu=-18dBFS (or +4dBu (0VU)=-14dBFS).

Anyway, check the alignment of your console meters, decide on a suitable alignment between the console meters and the DAW, and adjust gains and sensitivities accordingly so that the headroom margins through the whole chain are sensible and everything works as you expect it to.
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by cashhewn »

Thank you all so much for your help!

Hugh, if you have a moment could you link to or elaborate on the idea behind wanting our volume pots for our main monitors around 7/10? Is it a “Fletcher-Munson-y” sort of logarithmic sweet-spot thing?

Thanks as always for all of your help!
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by Hugh Robjohns »

It's a basic practical reality.

It's useful to be able to turn the volume up above the reference level to check for low level noises or just to get the client's trouser legs flapping.

Most monitor controllers allow 10-12dB for that, and on an audio-taper or log format 'pot' or fader, that works out to a reference level around 70% of the full travel — Ie. about 7/10 on a circumferential scale.

With all ganged pots/faders, the greatest resolution (ie. smallest change per degree of movement) occurs at the top of the range. This implies it's better to have the reference position as close to the top of the range as practical.

And as the value of resistance increases towards the middle and bottom of the scale, the matching between the two ganged tracks degrades significantly. This results in random left-right image shifts, and so its best to avoid this region for the reference level.

Volume controls using mechical switches or encoders operating switched relays don't suffer these tracking mismatches, of course which is why they are preferred in high-end monitor controllers.
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by cashhewn »

Makes perfect sense Hugh, thanks for all of the detailed information, as always.

I am a happy subscriber and love my print editions :D
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by cashhewn »

ps- Hugh: brilliant idea about lowering the output from Sonarworks, I wouldn’t have thought of that and my monitors don’t have sensitivity adjustment so it’s much easier to attenuate the Sonarworks output than build passive/resistive inline pads, I just lowered the output in the software to the appropriate level for my monitor controller potentiometer and saved it as a preset…voila. Thanks again for your always outstanding help.
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Re: I set out to simply calibrate my mix monitoring level with pink noise...

Post by Hugh Robjohns »

:thumbup:

Glad you're happy with the outcome.

Before anyone starts shouting, I should point out that, technically, this solution will degrade the signal/noise ratio slightly of the monitor chain... but I would argue that the practical and operational benefits outweigh that in your situation.
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