Avid Pro Audio Community

Avid Pro Audio Community

How to Join & Post  •  Community Terms of Use  •  Help Us Help You

Knowledge Base Search  •  Community Search  •  Learn & Support


Avid Home Page

Go Back   Avid Pro Audio Community > Pro Tools Post Production > Post - Surround - Video

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 02-02-2010, 01:53 PM
mikevarela mikevarela is offline
Member
 
Join Date: Feb 2008
Location: Los Angeles
Posts: 571
Default Room Calibration - ATSC Standards - Help

Need a little guidance (Marti?)

I'm re-calibrating my room... 1027 cubic feet. I've followed the ATSC standard that Marti posted at the top of the forum (sticky).

1) I calibrated my system with the 440 signal. I'm on an LE 003 Rack system with a Durrough stereo digital meter. I've calibrated the 003 volume knob to make the Durrough read -20dbfs per channel (2).

2) I used the band-limited pink noise and my SPL monitor controller volume knob and Radioshack digital SPL meter to calibrate the level at 76, as per the cubic size of my room. I set the volume knob and marked the position, each speaker measures the same level.

3) Here's my problem. I downloaded the speech sample that the ATSC paper mentioned, dubbed it to stereo and played the file (they say it's measured at -24 LKFS (loudness)). When I play this file it's very loud, not at all what I would mix at. They say adjust for comfortable mixing level but can't figure why they'd have me go and change any levels. I thought this was calibration. If I do change the level to a normal one, a listening level I'd mix Dx at, then the speech falls at -31dbfs, or around there. Is this right????

I'm posting the last paragraph from the ATSC paper for clarification.

I appreciate any help in figuring this step out.

-Mike

----------------

Quote:
Step 3. Dub (duplicate) the original speech file downloaded (see below) using unity gain into the
center or mono channel of the playback device in use. In the case where only two-channel
stereo monitoring exists, dub the original speech into left and right channels with an
attenuation of –3 dB into each of the channels, and confirm that they are in sync to the sample.
Ensure that the signal path is the same as was used in step 1 above, so that this playback
encounters the same gain conditions as the tone of step 1 and the noise of step 2. Play the
speech, which is recorded with a measured loudness of –24 LKFS, and observe that its level is
normal. If no sound level meter is available and you have skipped here from Step 2, confirm
that you have performed Step 1 if you have such equipment and adjust this track for the most
comfortable listening level.
• This speech recording has been adjusted in level so that it measures –24 LKFS to standard
BS.1770 [3].
http://www.atsc.org/refs/a85/Speech_sample.wav
__________________
NuanceTone.com
Reply With Quote
  #2  
Old 02-02-2010, 03:02 PM
O.G. Killa's Avatar
O.G. Killa O.G. Killa is offline
Member
 
Join Date: Oct 2002
Location: Los Angeles
Posts: 2,152
Default Re: Room Calibration - ATSC Standards - Help

what SPL did you calibrate to? 1027 cubic feet is considered "small". Keep in mind most hollywood dub stages are anywhere from 40,000 to 60,000 cubic feet. A lot of the dub stage calibration specs are written for these size rooms. When the speakers get closer and closer to you, their apparent loudness goes up, meaning a speaker 20ft away calibrated to 85dB SPL will feel quieter than a speaker 5 ft away calibrated to the same 85dB SPL. Depending on how close you are to the speakers, you might have to calibrate to a lower level for it to "feel" and/or "sound" correct in your room.

The experience you are describing with the ATSC dialogue sounds like you are encountering the acoustic anomaly I'm describing above.

I think dolby (anyone, please correct me if I'm mistaken) specifies that you need to be at least 13 ft 4 inches away from your front speakers in order to use the 85dB SPL ref level. But to me even that seems pretty close and might need to be calibrated to 82dB or something instead of 85.

In the end, use your ears. 99% of the time they are correct.
__________________
Derek Jones
Sound Engineer / Producer / Composer

Derek Jones Linkedin
Megatrax Recording Studios
Megatrax Studios Yelp Page
A-list Music Artist Page
Reply With Quote
  #3  
Old 02-02-2010, 03:11 PM
dr sound's Avatar
dr sound dr sound is offline
Member
 
Join Date: Jul 2002
Location: Burbank, CA
Posts: 2,118
Default Re: Room Calibration - ATSC Standards - Help

I would try 82 spl and see how it sounds. If it is still too loud try
going down in 1db steps until it sounds right.
If it's below 78, you better check it in a calibrated dub stage.
__________________
Marti D. Humphrey CAS
aka dr.sound
www.thedubstage.com
IMDB http://www.imdb.com/name/nm0401937/
Like everything in life, there are no guarantees just opportunities.
Reply With Quote
  #4  
Old 02-02-2010, 03:33 PM
O.G. Killa's Avatar
O.G. Killa O.G. Killa is offline
Member
 
Join Date: Oct 2002
Location: Los Angeles
Posts: 2,152
Default Re: Room Calibration - ATSC Standards - Help

Quote:
Originally Posted by mikevarela View Post
2) I used the band-limited pink noise and my SPL monitor controller volume knob and Radioshack digital SPL meter to calibrate the level at 76, as per the cubic size of my room.
I just re-read this and realized I misunderstood it the first time. sorry. If you are cal'ing to 76dB SPL, then you are already compensating for your room size and speaker distance.

If it's any help... most feature films are said to have an average dialogue level of around -27dBfs to -31dBfs. But when mixing, they aren't looking at the meters to make sure it hits those numbers. That's just kind of how it works out when adjusting levels by ear in a calibrated room.

So maybe you aren't that far off after all. But as Marti suggested, you might want to mix something and then bring it to a calibrated dub stage to check it as well as listening to it in a few theaters.
__________________
Derek Jones
Sound Engineer / Producer / Composer

Derek Jones Linkedin
Megatrax Recording Studios
Megatrax Studios Yelp Page
A-list Music Artist Page
Reply With Quote
  #5  
Old 02-02-2010, 03:40 PM
minister's Avatar
minister minister is online now
Member
 
Join Date: Jun 2004
Location: Minneapolis, MN
Posts: 4,807
Default Re: Room Calibration - ATSC Standards - Help

Quote:
Originally Posted by O.G. Killa View Post
what SPL did you calibrate to? 1027 cubic feet is considered "small". Keep in mind most hollywood dub stages are anywhere from 40,000 to 60,000 cubic feet. A lot of the dub stage calibration specs are written for these size rooms. When the speakers get closer and closer to you, their apparent loudness goes up, meaning a speaker 20ft away calibrated to 85dB SPL will feel quieter than a speaker 5 ft away calibrated to the same 85dB SPL. Depending on how close you are to the speakers, you might have to calibrate to a lower level for it to "feel" and/or "sound" correct in your room.

The experience you are describing with the ATSC dialogue sounds like you are encountering the acoustic anomaly I'm describing above.

I think dolby (anyone, please correct me if I'm mistaken) specifies that you need to be at least 13 ft 4 inches away from your front speakers in order to use the 85dB SPL ref level. But to me even that seems pretty close and might need to be calibrated to 82dB or something instead of 85.

In the end, use your ears. 99% of the time they are correct.
These ATSC guidelines that people are referring to are for mixing HDTV NOT mixing Theatrical Features. What you are saying here does not apply.

Mike, I think your system may not be set up correctly. If you are going AES into the Dorroughs, why are you changing any volumes? The volume knob on the 003 affects the Digital output? Digital is absolute. Levels in the DAW passed over AES are absolutely the same as what is read on a meter. Analogue is a world that needs a reference.

Also, the pink noise is -20dBFS RMS, NOT Peak value. It's Peak value will be higher.

You should be putting the pink in a channel that feeds the left, then adjust your monitor controller so that this pink reads your target monitoring SPL.
__________________
Tom Hambleton CAS
Ministry of Fancy Noises
IMDb
Undertone on Facebook
Undertone Custom Sound Libraries

"Groupable markers would be epochal!"
-Starcrash
Reply With Quote
  #6  
Old 02-02-2010, 05:13 PM
mikevarela mikevarela is offline
Member
 
Join Date: Feb 2008
Location: Los Angeles
Posts: 571
Default Re: Room Calibration - ATSC Standards - Help

Thanks guys, I think I've got it but needed clarification.

Tom, your right, this is a TV spec. I'm mostly mixing shorts which will or will not be shown in a theater (probably via DVD) and most definitely online. If I was in a larger room, I'd still probably hold the monitor level at around 80, just because my clients are gonna want less dynamic range and a little hotter signal.

I've used the ATSC spec to calibrate, Tom your right on the pink noise, it does register higher peaks, but that's not what I'm looking at, I'm looking at a mono RMS value that sits exactly at -20dbfs per channel, which is what the paper called for and what I'm getting. Also, the 003 volume knob I'm referring to here is NOT digital. Because the 003 is meant as an all in one box for the home studio, it offers 2 headphone outputs and a volume control output to monitors. It also offers a secondary main output as well. I think it's great for convenience. But it most certainly is analog.

When you guys say -27 to -31 is about right for Dx, then that makes me feel better, because that's where it feels right when I measure it on the Durrough. That ATSC speech file plays very hot, and while I understand it might be for a dub stage, I can't figure out how this is different. If say, I calibrate my monitors to 80, I hear a volume level that registers at that level. If I calibrate a dub stage to 80, that level should remain consistent. Of course more juice is being pumped through the dub's speakers to get a reading of 80 at the mix position, but never-the-less it should remain the same.

So why then would the spec call for the vocal sample to be adjusted to desired level in a calibration test? I thought all measurements are supposed to got through full scale.

Am i understanding you guys right? If you played this vocal file in your rooms, it would register quieter?

Marti, you say I should adjust to 82, but for my room volume they say 76 is where I should stay at. I'm happy with the figure, and need to mix something and take it to a stage somewhere for a quick test. I'm up for changes, but just want to get it all right.. youknow.

-mike
__________________
NuanceTone.com
Reply With Quote
  #7  
Old 02-02-2010, 05:52 PM
minister's Avatar
minister minister is online now
Member
 
Join Date: Jun 2004
Location: Minneapolis, MN
Posts: 4,807
Default Re: Room Calibration - ATSC Standards - Help

Quote:
Originally Posted by mikevarela View Post
1) ... I've calibrated the 003 volume knob to make the Durrough read -20dbfs per channel (2).
Mike,

I am confused by this statement.
__________________
Tom Hambleton CAS
Ministry of Fancy Noises
IMDb
Undertone on Facebook
Undertone Custom Sound Libraries

"Groupable markers would be epochal!"
-Starcrash
Reply With Quote
  #8  
Old 02-02-2010, 06:20 PM
mikevarela mikevarela is offline
Member
 
Join Date: Feb 2008
Location: Los Angeles
Posts: 571
Default Re: Room Calibration - ATSC Standards - Help

the Durrough is fed from the main outs of the 003, when I playback the test audio file which is supposed to read -20dbfs, I turn the volume monitor know on the 003 all the way up and leave it there. it registers -20dbfs on the durrough. The durrough is an analog meter (might not have mentioned that) reading a digital scale (top of meter is 0dbfs).

I'm now understanding that maybe I should run the durrough on the same analog chain as the monitors, but without a pass thru, I'm hesitant to duplicate the audio signal to my monitors for fear of noise.

Right now I take the 1-8 analog outputs from the 003 vie db-25 cable snake to my monitor controller (brand SPL). That leaves me a main set of stereo outputs which i feed to the durrough via balanced TRS to XLR cables.

The main volume is monitored and augmented via the monitor controller, the durrough is fed and augmented via the volume knob on the 003, which has been pinned at full for quite some time.

any help in how to configure these all together so that the durrough reads the main monitor chain?
__________________
NuanceTone.com
Reply With Quote
  #9  
Old 02-02-2010, 06:30 PM
dr sound's Avatar
dr sound dr sound is offline
Member
 
Join Date: Jul 2002
Location: Burbank, CA
Posts: 2,118
Default Re: Room Calibration - ATSC Standards - Help

Quote:
Originally Posted by mikevarela View Post
Thanks guys, I think I've got it but needed clarification.

SNIP
Marti, you say I should adjust to 82, but for my room volume they say 76 is where I should stay at. I'm happy with the figure, and need to mix something and take it to a stage somewhere for a quick test. I'm up for changes, but just want to get it all right.. youknow.

-mike
Mike,
Sorry, I am in the middle of Mixing a Film and didn't read your post correctly.
listen to Minister.
I gotta go.....
__________________
Marti D. Humphrey CAS
aka dr.sound
www.thedubstage.com
IMDB http://www.imdb.com/name/nm0401937/
Like everything in life, there are no guarantees just opportunities.
Reply With Quote
  #10  
Old 02-02-2010, 06:43 PM
minister's Avatar
minister minister is online now
Member
 
Join Date: Jun 2004
Location: Minneapolis, MN
Posts: 4,807
Default Re: Room Calibration - ATSC Standards - Help

Quote:
Originally Posted by mikevarela View Post
....
1) I'm on an LE 003 Rack system with a Durrough stereo digital meter.
This is why I thought you were running a digital meter!

Quote:
Originally Posted by mikevarela View Post
tThe durrough is an analog meter (might not have mentioned that) reading a digital scale (top of meter is 0dbfs).
Hunh?
Once it is analog, the level reading is an analog of the voltage.

Your posts are very confusing.

If you are running ANALOG, the 003 does not do -20=1.228=0vu, so you will have a problem!

Forget the meter.

Put the correct pink in your system and adjust the volume to the appropriate SPL.
__________________
Tom Hambleton CAS
Ministry of Fancy Noises
IMDb
Undertone on Facebook
Undertone Custom Sound Libraries

"Groupable markers would be epochal!"
-Starcrash
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Meters for room calibration idris Post - Surround - Video 3 09-23-2010 05:27 PM
Monitor Calibration and Room Compensation. donrey Pro Tools TDM Systems (Mac) 3 09-18-2006 11:46 AM
Calibration in a small room... joeyk Post - Surround - Video 3 05-08-2006 10:02 PM
Room Calibration and Levels for LE Starcrash Post - Surround - Video 8 08-03-2005 10:40 AM
Room calibration for Stereo Monitoring Bossi 003, Mbox 2, Digi 002, original Mbox, Digi 001 (Win) 4 06-14-2005 10:48 AM


All times are GMT -7. The time now is 12:54 PM.


Powered by: vBulletin, Copyright ©2000 - 2008, Jelsoft Enterprises Limited. Forum Hosted By: URLJet.com