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Calibration Question.


jgbsound
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Howdy Gents,

So I have a new shiny S3 console and am re-calibrating my speakers for film reference?  (85 C spl).

So I mapped 6 tracks in ProTools to discreet channels for the 5.1 field and inserted Pro Tools tone generator, set it to pink noise to start the process.

By default, the tone generator sets the tone level to -20db (for headroom?).  

But if I truly want to work at the 85db reference level, shouldn't I set the tone generator to 0?  By doing this wouldn't that more accurately reflect the meximum 85spl I need to dial my monitors to?

Am I thinking about this the wrong way? 

Thanks for any guidance you can give me!

John

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I'm not an expert but that's the way the test tones are provided ( at -20dBFS ) so I I've always assumed that's the way to play them down.  In saying that 85dB C SPL is way too loud for me - unless you're in a stage this is going to blow your head off - I work to a non-standard 75dB and that's still too loud in the loud bits, but then so is the theater - and it has been translating nicely.

 

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Am I thinking about this the wrong way? 

yes, you are think the wrong way

what you need is band limited pink, pink nose with HP at 500 and LP at 2000 (aka Dolby Pink) this helps eliminate room modes from effecting the measurement level

so 1 channel set to 1 output, SG set to -20dB Pink, EQ3 with LPF set to 500 & HPF set to 2k

measure the SPL for that channel, trim to 85 dB slow C

change the output for the next speaker

repeat

setting the SG to 0 would make you calibration 20 dB to low / you mixes would be ~20 dB low

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So I have a new shiny S3 console and am re-calibrating my speakers for film reference?  (85 C spl).

Congratulations!

How big is your room?  Why are you calibrating to 85dBC?  Is your room the size of a small Theater or larger?  If so, go ahead.  If not, like it's the size of a typical control room, you should be at 76 or 79dBC.

 

So I mapped 6 tracks in ProTools to discreet channels for the 5.1 field

 

Good.

and inserted Pro Tools tone generator, set it to pink noise to start the process.

Stop right there! The PT Pink genny is off by as much as 2dB.

Download the pink noise from here:

http://thedubstage.com/links/

Don't use Band-limited PINK UNLESS you have Bass Managed speakers.  For Full Range, full PINK is required.

Are you mixing for theatrical?  Or DVD/Home?  Because the cal is different.

for Theatrical, the Surrounds are 3dB down from the Screen Channels (so they sum to 1 "channel" of level in the back).  For the Home, it is equal SPL all the way around.

HOWEVER, you need an RTA to calibrate the Sub which should be +10 IN-BAND above the Screen Channels.  This ends up being around 91dBC on an SPL meter assuming 85dBC.

 

 

 

Edited by minister
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I'm mixing for theatrical, mostly.  Minister, I see the settings you mentioned in the Dolby Production Guidelines.  And thank you for the link to the appropriate band limited pink noise, a.k.a. Dolby Pink.  

I'm in a smaller mixing room (it's a 15x12' mix room ) so I would calibrate to the lower level I'm assuming.  Makes sense now considering you are setting reference relative to nominal dialog levels.  I'm pretty sure this is what I did before, the last time I calibrated the entire system.  

I have been doing the initial SPL measurement with my Sound Level Meter..

This is a good starting point!  I'll pipe up if I have any additional questions?

Thank you one and all!

John

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How things translate to rooms with 10,000 cubic feet of room volume and above from your room will be a bit of an art.  It is hard to say exactly if it should be 76 or 79, but I would start with 79 to see how it translates.  And, the reason you set it lower in a smaller room has to do with how "loud" things sound in a smaller room vs the same SPL in a bigger room, not nominal dialogue levels.

I also am using an LFE for the low end.

What does this mean?

LFE is Low Frequency Effects.  It is a channel, not a speaker.

Are you using a Sub-Satellite system?  If your speakers go down to 54Hz, where is your crossover?  If you have a Bass Managed (Redirected) system -- and I am assuming you know what that means -- you use Band Limited Pink.

Otherwise, if you simply have a speaker in the front that goes down to 54 but you are not not using Bass Redirect, use full pink.

What monitor controller?

Edited by minister
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What monitor controller(s) do you recommend?

For surround?  Bass Managed?  Film work?  They are all a little different, fitting different applications.

If you need Bass Managed, then Blue Sky.

If you don't, I like the Passive SM Pro Controllers.  They make a 5.1.  Not Bass Managed.

For film work, the standard for a long time was the MartinSound MulitiMAX.  I have one of these in my film mix room. Not bass managed.  

For high-end, Cranesong Avocet (Not Bass Managed) or Trinnov (options are there wit these).

 

 

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-20dBfs is the accepted 0VU reference for original dialog recording. I am assuming that the accepted VU reference for the mix of a final product is the same as mastered music, which is -12dBfs. If this is, indeed, the case, the calibration 0VU reference for final mix would be -12dBfs, not -20dBfs. This would explain why 85dB would be painfully loud with a 0VU reference of -20dBfs, which would be 8dB louder than when using a 0VU reference of -12dBfs.

Glen Trew

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-20dBfs is the accepted 0VU reference for original dialog recording. I am assuming that the accepted VU reference for the mix of a final product is the same as mastered music, which is -12dBfs. If this is, indeed, the case, the calibration 0VU reference for final mix would be -12dBfs, not -20dBfs. This would explain why 85dB would be painfully loud with a 0VU reference of -20dBfs, which would be 8dB louder than when using a 0VU reference of -12dBfs.

Glen Trew

Sorry Glen, this is misleading....

Theatrical alignment in US has been, since the 70's: 

Electrical alignment : -20dBFS 1kHz Sine = 1.23vRMS = 0 VU = +4dBU.  

For Room Calibration: -20dBFS RMS PINK = 0VU = 85dBC per Screen Channel in a room having a volume of 10,000 cubic. -82dBC per surround. and +10 IN-BAND for the Subwoofer (measured on an RTA)

Aligning a Music Mastering suite for -12dBFS= 0 VU has ZERO to do with theatrical alignment.  Mix of the final Theatrical product is -20=0VU.

When mixing a film, you calibrate, then MIX BY EAR.  So if it is PAINFULLY LOUD, like a piece of full scale music, then turn it down.  it's simple.  Yes, it's true, you would not play a Full Scale Mastered Music piece at that level, it would be painfully loud.

For smaller rooms, an alignment should be 79dBC or 76dBC for translation to larger rooms (with X-Curve).

 

Edited by minister
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I use the Blue Sky calibration test files for the occasional audio post project. However.. while BS states the full bandwidth pink noise file is -20dBFS, (mono)  it indicates -11.3dBFS on my DAW meters.(which are know to be accurate).

PINK noise is measured as -20dBFS RMS.  You are measuring PEAK.  Yes, it is approximately -11 PEAK. But you don't align Sound Pressure Level using PEAK.

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