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Author Topic: 24 bit v 16 bit  (Read 2745 times)

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Offline DSatz

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Re: 24 bit v 16 bit
« Reply #30 on: February 01, 2019, 12:38:48 PM »
> The -18dBFS is the EBU standard and the -20dBFS the SMPTE standard to set for 0VU as I understand it - which is why I quoted those figures.

John, I know that you know this, but for the benefit of those who don't:

VU meters are a very particular thing. Not every analog meter is a VU meter--not even every analog meter that has the letters "VU" on its face. True VU meters are/were highly standardized "volume indicators" (VU = "volume units"). They were designed in the early 1940s to give an idea of the perceived loudness mainly of speech transmission.

The motion of a VU meter's needle has "syllabic response"--using an integration time (ca. 200 milliseconds as I recall) that the Bell System engineers considered optimal for telephone systems and AM broadcasting. True VU meters are dead-on accurate when fed continuous tones, but with live, uncompressed program material and modern microphones (e.g. condensers), signal peaks are typically about 8 dB higher than what you see on the meter. (John, you will probably recall that PPMs were calibrated so that their zero point was effectively equal to +8 VU for this reason.) With some program material a VU meter would "under-read" signal peaks by a significantly greater amount--especially strong signal components that rise and fall quickly, such as percussion picked up at close range with condenser microphones.

Now, the scale on a VU meter doesn't stop at 0 dB; it continues to +3. The zone between 0 VU and +3 is marked in red, and with analog tape there was higher distortion above 0 VU than below it, sometimes audibly so. But even +3 VU wasn't a "brick wall" limit. The most conservative, purist classical approach to recording still involved "going into the red" sometimes--just not hanging out there for any length of time. Rock music, on the other hand, was often recorded with the needle well into the red a lot of the time--intentionally using tape saturation as a kind of compressor. I've seen some engineers "push" tape so hard that the VU meters were continuously "pinned", i.e. off the scale and all the way to the right, and they were proud of it.

In summary: For live recording, if you set -18 dBFS = 0 VU on continuous tone, your typical (often-recurring) peaks on the digital side will tend to be around -10 to -8 dBFS, with occasional peaks going maybe to around -5 or in truly extreme cases, a touch higher. Those would be very good levels for 24-bit recording in my opinion.

So the standards you mentioned make excellent sense IF the fundamental difference between VU meters and peak-reading meters is well understood. For better or worse, though, fewer and fewer people nowadays have ever seen real VU meters in action, let alone used them for live recording. So some people might infer (quite wrongly) that according to these standards, their digital recording levels should be set so that the peaks occur at -18 or -20 dBFS.

But that's not at all what those standards mean, and setting your levels so low is just asking for extra noise--if not from the recording channel itself, then from everything that comes before and after it.

--best regards
« Last Edit: February 05, 2019, 10:16:59 AM by DSatz »
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Offline u2_fly_2

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Re: 24 bit v 16 bit
« Reply #31 on: March 18, 2019, 12:51:57 PM »
If you have the option use 24 Bit.

As all good people has explained/said...more "headroom" to work with in post-prod. and also if you have space for 24-Bit, Why not?

One can always dither down to 44.1-16 Bit later on.

We already have recorders with 192/24-Bit...Do we really need it? Perhaps not, yet use it if there´s a chance/option is my opinion...then ofcourse it´s all about which mic´s and position you use.
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Offline Gutbucket

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Re: 24 bit v 16 bit
« Reply #32 on: March 18, 2019, 06:07:18 PM »
Why not?

Because some recorders have a high noise-floor and are effectively only recording around 16bits of actual dynamic range even when set to 24bit mode.  In that case you'd just produce a larger sized file with no benefit.  But to know if that's the case or not you'd have to measure, and since the difference in file size going from 16 to 24 bits isn't astronomic, it's a reasonable choice to record in 24 bit mode without worrying too much wasted file space. < Makes sense to worry more about setting levels (go a bit higher).

In contrast, going from 48kHz to 96kHz doubles the file size, and going to 192kHz quadruples it.  That's way more file size bloat than going from 16bits to 24bits and I'd be more hesitant to do so unless I'd convinced myself that the result was worth it.
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Offline MakersMarc

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Re: 24 bit v 16 bit
« Reply #33 on: March 18, 2019, 09:52:10 PM »
I ran super hot levels when recording to DAT, the only way thing I hate  about 😈 is having to guess at levels and having to add a bunch of volume, yeah I’m doing solid state 24 bit, but I’m losing quite a bit more than I gain by not being able to run hot. Imo.
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Offline Ben Turnbull

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Re: 24 bit v 16 bit
« Reply #34 on: April 07, 2019, 11:39:40 AM »
Setting levels correctly "cold" will come with increased opportunity and venue familiarity.

In short, you need to get out more.

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Offline MakersMarc

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Re: 24 bit v 16 bit
« Reply #35 on: April 07, 2019, 11:57:46 AM »
Setting levels correctly "cold" will come with increased opportunity and venue familiarity.

In short, you need to get out more.

<ducks, runs, covers ass>

Have that 620 down now. If I am hitting -12 levels I'm good with it, which generally results if I run 620 levels at -11 or so. So I could probably be fine at like -6 but still don't like to take that chance of clipping. I was worried I clipped Kansas, but I get it home and it's like -12. :facepalm:
« Last Edit: April 07, 2019, 12:00:45 PM by MakersMarc »
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Offline Ben Turnbull

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Re: 24 bit v 16 bit
« Reply #36 on: April 12, 2019, 06:03:05 PM »
 ??? Sounded fine to me. Post work?
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Offline MakersMarc

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Re: 24 bit v 16 bit
« Reply #37 on: April 12, 2019, 07:07:44 PM »
??? Sounded fine to me. Post work?

Normalize and amplified by 4db. That’s it.
😈 Mk4v/41v>nbob actives>Baby nbox>Oade warm mod Marantz 620.

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