The -20 dB discussion

[Syncman]

Okay, Here it is. Who can tell me why the hell we ended up with 20 dB of headroom. Because we can? Because Sony decided it was the way. Everytime I mix down and watch those top 6 dB just sit there unused (I use -18, sue me), I kind of laugh to myself about the state of things.

So what to do, not use the top few dB, the best sounding bits? Use -12 for reference in a blatant protest to the Sony way and confuse editors everywhere? Or the most popular way, compress the hell out of the mix so it seems as though it's all the way up there (kidding). Really how do you all handle it? I'm assuming most just throw them away and leave the levels down where the kid bumping it to 1/2" will stay out of trouble, but is it right?

Chip

[trakbytes]

Turn down the monitors and print hotter!

Actually, I believe the -20 standard was arrived at as a means to get a full-level mag film mix onto 16 bit digital media without blowing it out. -24 was tried for awhile, but it was too low for average levels. I used to get a lot of ADR (still do, for that matter) where the waveform is barely visible. Signal to noise sounds like a cassette tape. A common myth is that digital has no noise, where in reality it is plenty noisy if recorded too low.

I see plenty of 5.1 mixes where every one of the bits is used. TV broadcast is a different story, as program material is limited to +12. Here, the top 8db remains unused. I have been told that this is a limitation with Digibeta machines, although I find that kind of hard to believe with today's technology. Maybe Dr Sound has some more concrete explanation?

rcm

[Chief Technician]

Could you be more specific about the limitation? I can certainly hit the deck at 0dBFS (if the broadcaster's would let me, alas we don't do mixes for FOX that often).

[TVPostSound]

I have been told that this is a limitation with Digibeta machines

Not true, sattelite transponders have a HARD -8 limiter, anything above gets rejected, if it passes the QC, it gets distorted!!!!!

[Soundwise]

In Finland the TV broadcast level is -12dBfs for Digibeta masters. Peaks can go up to -3dBfs. Go figure.

Jari

[dr sound]

Why do we have to hit stuff at the absolute maximum to feel we've used every "good sounding bit"?
Thank God we have dynamics. Hell, if you wanta slam it go for it. Just don't bitch when it gets rejected or is lower in volume then the next show or spot. It takes skill to make it fit within the guidelines.Find out what they are and go for it. Otherewise have at it and keep on bitching! The reasons are as explained, satelites and other mediums are the reason for -20. I Like it!
Just a point of view,

[Chief Technician]

I never claimed I didn't like it. Perhaps I should've phrased it differently. We stay within specs, and FOX as I understand it wants you to hit at -2dBFS. So, when we mix for Discovery and they say -10dBFS is your peak ceiling, that's how we mix.

[TVPostSound]

FOX is digital, so we get full dynamics.

I just printed a Dicovery/Travel Channel show the delivery specs are -12dBfs or +8 analog,
-20dBfs = 0Vu

But they want the average VU to be -5 to -2 at 300ms analog metering response (Can you say Dorrough?). That left me 10 to 13 dBs of dynamic range, not bad for a talkie with BI music!!! Its nice to mix with minimal compression!!!!

[Richard Fairbanks]

I appologize up front for the tone of this reply. Don't take it personally but this topic is worn out for me.

Hey, if you want to set your system for a reference level of -12 (instead of -18 or -20) then go right ahead. Just be sure you bring your final mix level back down to -20 before you make your deliveries. It is the networks who have set their delivery standards to be what they are, not a room full of misguided editors. Existing land and satelite distribution chains are filled with old technology and the built in limits exist until the equipment is replaced.

Personally, I prefer to do my final deliveries with 1:1 gain, which means my whole system is set for a -20 reference level. I prefer to have the extra headroom in my tracks for mistakes and surprises. I believe it is foolish to operate at tippy top peak because when your tracks are constantly hitting the top you will be forced to always pad your signal before you process further. Talk about a waste of time and resolution! You cannot even do subtractive eq because the eq will actually cause a bit of gain somewhere out of band. Gain applied to a 0dbfs peak equals distortion.

"Best sounding bits"???? There is a one bit difference between 0dbfs and -6dbfs. Technically you will probably get between 1 and 2 bits of extra resolution if you operate with no headroom. I did it that way in the old days and can honestly say the negative impact in terms of having no spare headroom was not worth it to me. I could honestly never hear a difference in sound quality. What I could hear was the increased noise floor when I had 48 tracks opened up and no signal in most of them. That was on digital 16 bit tape machines. Today we can mute those silent regions on our tracks, which effectively turns the track off and removes the noise. Or just mute the freakin' fader. We can work at 24 bits, which takes most of the weight out of your concerns. It is much more important, in my view, to concentrate on good mixes and good content, and forget about that extra bit just sitting there unused but available to catch you when you mess up.

But, hey, go ahead and do whatever makes you comfortable. After all, there are no rules and if you want to live on the edge of crazy then I think you should.

[dr sound]

Thanks Richard! Well said!