Post audio levels

[Marc Wielage]

Yes, the remixes for home video are being done in small-to-mid-sized mixing stages. As one example, here's info on the THX-approved PM3 stages, which are for non-theatrical (TV, home video, etc.) mixes:

http://www.thx.com/professional/sound-engineer/thx-certified-pm3-studio/

Among other things, people are using lower reference levels, as low as 79dB compared to the usual 85dB.

[ccsnd]

yeah, between 79 and 82 are the reference levels for tv. 85 is mostly theatrical mixes.

[Toy Robot]

Anyone else using the Bob Katz K-System for monitoring in post? I've implemented it a long time ago and it's amazing. Completely changed my re-recording mixing in post.

[Marc Wielage]

I think the ITU standard goes in the same direction as Bob Katz' K-System, but is much more recent. I think Bob's idea was from the late 1990s, and came from a concern about overcompressed CD mastering. The ITU standard is more for film & TV, and is from the last couple of years.

[Toy Robot]

I think the ITU standard goes in the same direction as Bob Katz' K-System, but is much more recent. I think Bob's idea was from the late 1990s, and came from a concern about overcompressed CD mastering. The ITU standard is more for film & TV, and is from the last couple of years.

Very good to know. I don't focus on post, so wasn't aware, but I'll certainly add this to my punch-list. You're spot on about how his method came to be. I started in studios with bands like so many other sound mixers on this forum, and not all of the knowledge is directly transferrable.

[Tony Koretz]

yeah, between 79 and 82 are the reference levels for tv. 85 is mostly theatrical mixes.

Wow this thread has so much great discussion and ideas on it. Glad I found it!

If you are in a smallish room and are primarily using nearfield monitoring, then 85dB is going to sound Very Loud. Even 82 can be fatiguing over a preiod of time. I have found that in my room working at 79 dB is the best level for me to work at.

Besides what's here already, I am interested to know when using compressors and limiters on stems and stereo mixes in post, what sort of release times people are using on their compressors and limiters for the most natural sound with no pumping etc?

[Philip Perkins]

For small rooms we use the ATSC standard for remote trucks, which is 76 db.

phil p

[Jay Rose]

what sort of release times people are using on their compressors and limiters for the most natural sound with no pumping etc?

For the compressors: fast attack, not quite so fast release... and use a multiband where you can make the times faster for higher frequencies. Too fast an attack/decay on LF will distort, as the compressor tries to ride the wave instead of the envelope.

The real trick is having a fairly low threshold - much lower than you'd think - but then backing off the ratio, with an eye on the GR meter. Adjust both for the GR you'd expect on louder passages... and the combination of low threshold and gentle ratio will get you there without obvious compression.

Limiters are a different story. They're there for protection, and shouldn't be triggering too often. So high thesh, high ratio, fast attack/decay (depending on band).

[Tony Koretz]

For the compressors: fast attack, not quite so fast release... and use a multiband where you can make the times faster for higher frequencies. Too fast an attack/decay on LF will distort, as the compressor tries to ride the wave instead of the envelope.

The real trick is having a fairly low threshold - much lower than you'd think - but then backing off the ratio, with an eye on the GR meter. Adjust both for the GR you'd expect on louder passages... and the combination of low threshold and gentle ratio will get you there without obvious compression.

Limiters are a different story. They're there for protection, and shouldn't be triggering too often. So high thesh, high ratio, fast attack/decay (depending on band).

Cool...nice response. Great points on multi band comps. It's always interesting to read how other people go about things, and their techniques to get the results they are after.

Limiters are for protection yes...but if you have an L2 on your master buss for instance, and you are using it to tame mixes for TV to keep them in line......? Your take on that ?

[ccsnd]

Wow this thread has so much great discussion and ideas on it. Glad I found it!

If you are in a smallish room and are primarily using nearfield monitoring, then 85dB is going to sound Very Loud. Even 82 can be fatiguing over a preiod of time. I have found that in my room working at 79 dB is the best level for me to work at.

85dbb is the same near as it is far. It is to be measured from your reference "sweet spot", not at the speaker.

[RJBerto]

85dbb is the same near as it is far. It is to be measured from your reference "sweet spot", not at the speaker.

+1

The issue is that in a smaller room, 85dbSPL may be too loud because you end up with the room interacting with the direct sound more than it would in a larger space. Calibrating to 79dbSPL will help to minimize this interaction if you must mix in a smaller room.

[Tony Koretz]

Yes you measure at the listening position not at the speaker. However, 85db in a smallish control room is pretty loud and not recommended.

[Tony Koretz]

+1

The issue is that in a smaller room, 85dbSPL may be too loud because you end up with the room interacting with the direct sound more than it would in a larger space. Calibrating to 79dbSPL will help to minimize this interaction if you must mix in a smaller room.

Everyone here seems pretty knowledgible so this may not be much help, but if anyone here is unsure of how to calbrate from the listening position, some time back I wrote a basic tutorial on how to do it which can be found here:

http://rocksuresoundz.com/2011/10/11/calibration-of-audio-playback-levels/

[Mark Orusa]

The mix room where I edit and mix movies is set around 74-75 db IRRC. I've found it produces levels consistent with comparable movies. Of course, I tend to mix a little quiet. It would be considered a small mix room.

Mark O.

[Toy Robot]

And for people who haven't done this before, remember to set your monitoring levels appropriately, and then let your ears do the mixing. Don't mix with meters.

That is to say, for example, if you set up an 85db monitoring environment then you are working in a controlled, calibrated environment. When you hear dialog it should be clear and comfortable and easy to understand. You should never have to struggle to understand dialog. And when you hear sound design fx and music scoring, they should be appropriately mixed to interact with the dialog.

Don't mix the dialog so loud that you're turning your volume down below 85db because it's too loud. If it's too loud, then it's TOO LOUD. Mix down to a comfortable and clear level, and then you'll have massive amounts of headroom for sound design.

[Rick Reineke]

"And when you hear sound design fx and music scoring, they should be appropriately mixed to interact with the dialog"

Unfortunately this has not been the norm in the last ten years or so. Just the opposite.. Not my preference..

Tony, you should have added 'PFL' to you glossary, which BTW stands for "Pretty F___ing Loud"

[ccsnd]

"And when you hear sound design fx and music scoring, they should be appropriately mixed to interact with the dialog"

Unfortunately this has not been the norm in the last ten years or so. Just the opposite.. Not my preference..

Tony, you should have added 'PFL' to you glossary, which BTW stands for "Pretty F___ing Loud"

?

[Rick Reineke]

The PFL is a joke, sort of. Back in my recording studio days, that was my common answer when band members and such always asked, 'What's PFL mean, on that button."

[Tony Koretz]

The PFL is a joke, sort of. Back in my recording studio days, that was my common answer when band members and such always asked, 'What's PFL mean, on that button."

Ah yes I left that one out

[Marc Wielage]

Ah, PFL is related to the Rude Solo Light on Mackie consoles...

[ccsnd]

Ah, PFL is related to the Rude Solo Light on Mackie consoles...

HA!

[Tony Koretz]

Ah, PFL is related to the Rude Solo Light on Mackie consoles...

Oh I always thought it was the button you press when you want someone to Please Flamin' Leave

[AudioPostGuy]

There have been several issues raised in this thread and many of the replies lack vital facts (or occasionally are incorrect) which results in many of the answers being rather unclear or misleading. So I'll try and address some of them:

Monitoring and Calibration: The standard for theatrical calibration is 85dBSPL = -20dBFS. However, this is only applicable to the large, commercial mix stages. As has been mentioned, once calibrated, the mixing is done "by ear" the problem here is that "by ear" really means "by human perception". Human perception of loudness for example is only partially and indirectly dictated by sound pressure levels. So although 85dB as measured at the listening position by an SPL meter is always 85dB, how loud 85dBSPL is perceived to be varies enormously. In a small room 85dBSPL is going to sound way too loud, so when mixing by ear your is going to sound way too quiet when played back in a cinema (very large room). You must also remember that when you are listening to your monitors, you are not actually listening to your monitors, you are listening to your monitors plus all the reflections of the sound waves being produced by your monitors from all the various surfaces in your mix room. In other words, the performance of your monitors is largely defined by the acoustic environment in which they are operating. I personally would much rather be working with $1k speakers in a very well treated acoustic environment than with $%k speakers in an untreated room. Now baring in mind that there is no way to emulate the acoustic properties of a cinema (very large room) in a small room, plus the fact that the construction/technology of the speakers used in cinemas cannot be used in a small room, a mix made in a small room is never going to translate well in a cinema. Obviously a lot of experience of large mix stages is going to help get you more in the ball park but no respecting re-recording mixer would feel confident in producing a mix which translates well without at the very least checking the mix on an approriately sized mix stage. For example, imagine how well your mix would work for audience members who may be sitting 30 feet closer to the left front speaker than to the right front speaker. So what is the correct calibration for your room? Unfortunately, that's impossible to say because there are too many variables: The exact size and dimensions of your room, your speakers and how they are positioned in your room, the acoustic properties of your room and your monitoring position. The correct calibration level for a small room could be anywhere from 66dBSPL to 82dBSPL and the only way of getting close to the correct setting is comparing the loudness (from experience) of a full sized mix stage.

One last pitfall to watch out for is the pink noise you use to calibrate.Nearflied monitors or monitors suitable for small rooms are normally not full range and have quite a severe roll-off below about 40Hz. If you are using standard 20Hz-20kHz pink noise to calibrate, part of the energy (the octave below 40Hz) being output by your D to A converter is not being output by your speakers, so you will have to increase the output of your speakers to achieve the desired SPL meter reading. In other words, your speakers will sound louder than the SPL meter reading indicates. I can't tell you how many small studios fall into this trap! The solution to this problem to use compensated band limited pink noise. Tomlinson Holman used to distribute a 500Hz - 2kHz pink noise file specifically for this purpose.

Calm Act: Contrary to a previous poster, the CALM Act is specifically aimed at commercials/adverts rather than the TV programs themselves. No advertiser is going to want their commercials to be quieter than the TV programs and no broadcaster wants two different specifications so in practise the ATSC A/85 spec is being implimented across the board, for programs and commercials. It should also be noted that the ITU BS 1770 spec upon which both the ATSC A/85 spec (USA) and the EBU R128 spec (Europe) are based includes EQ curves and RMS calculations which effectively defeats the existing techniques for making content appear louder than the previous peak level specs allowed. So the time honoured methods of boosting EQ in the critical hearing band and using lots of compression will produce a higher readings on the LKFS (or LUFS in Europe) meters requiring the mix to be lowered in level to achieve compliance. There is a slight loophole in the ATSC A/85 spec (which is plugged in the EBU R128 spec) and has been adopted in the ITU BS 1770-2 spec and I don't think it will be too long before it is therefore plugged by the ATSC as well. Apart from this minor loophole though there is really no way (for the foreseeable future) of making a mix sound louder while still hitting the spec. The ATSC A/85 (and EBU R128) specs are only aimed at the broadcast sector and is not applicable to the theatrical film sector.

Recording Levels: With analogue tape and 16bit digital, the noise floor of the recording systems meant that best practice was to record as hot as possible without clipping. 24bit has largely eliminated this problem and most good converters now provide a dynamic range of over 100dB and in some cases upto 120dB or more. The limiting factor is now much more the mics and mic pre-amps. If your recording device is calibrated to -20dBFS = 0VU (a standard setting for film) and if you are recording as close to 0dBFS as you can get, you are almost certainly overdriving your pre-amps and adding more noise not less! 24bit does not provide higher quality recording or playback than 16bit, the only point of 24bit is the increase in dynamic range and therefore the amount of headroom you have to play with. In other words, there is no longer any need to get anywhere near 0dBFS. This piece of knowledge is perhaps of more concern in music recording where you have highly controlled recording environments (very low noise floors). Obviously with production sound, environmental noise is far and away of more concern than adding pre-amp noise but it's still worth considering.

Hope this info has been of use.

Cheers, G

[sdog]

AudioPostGuy,

Thank You! I LOVE forum posts that clarify rather than muddle!!!

I learned most of this stuff in tiny little tidbits, after ungodly amounts of research, trial, and error (plenty of error!), my access to a large theater often only for a final double check. You've just packed a whole chunk of very useful information into one tidy post. Your post is definitely going to make someone's life a lot easier, particularly someone who needs to do the majority of their mixing in a smaller room.

[Philip Perkins]

Good advice re small room levels. Mixing at 85 in a small room is very painful!

phil p