Topic: Record Levels. -12 db?

[stevetoney]

I have just recently began using an M10 for recording.  Most of my projects are of the stage-lip, jazz variety.  The music often has a very wide dynamic range.  I have been pushing my levels well past -12 ( but no overs) using the logic that the softer portions are then being recorded at as high a level as possible.  Perhaps I am reverting back to my old D5 analog days, but this makes sense to me.  Thoughts?

As long as you don't clip, that's how I'd do it as well.

[deadheadcorey]

I prefer to peak out about -8db. gives me room to work with in post production.

[John Willett]

When first running my DR680 I had trouble convincing myself to run hotter than the metering lead me to believe.  Consiquently I had a couple shows where I had to put a knee to the groin of the file set and add 24dB.     There was noise floor-O-plenty, believe me.  Keeping 24 bit up around the target is better than "fixing it" in post.

But if you go over, you cannot "fix it in post".

If you set -18dBFS as 0VU and peak 4-8dB over this, you should be fine and still leave plenty of headroom.

Peaking at -24dBFS, like you obviously did, was just far far too low.

[Gutbucket]

Read this post a few times.  Three good points here-

The question is where is your input noise (acoustic + analog) floor with respect to your digital noise floor?  If it is already significantly above the digital floor, then you will get no benefit to increasing input level, and you would increase the risk the very significant detriment of clipping.  But if you never clip then it's not a big worry.

..[snip]..

Avisoft did these bench tests, but since they are only concerned with very quiet sounds they didn't test maximum dynamic range (which is at minimum, not maximum gain):

http://www.avisoft.com/recordertests.htm

Overall I suspect many people are recording hotter than they need to, even if they are recording to 16 bit.

Here's the take away- Clipping is usually the bigger problem compared to noise, is uglier and a PITA to fix if it occurs regularly.  Unless you are experiencing noise problems in the quiet parts when raising the level of your files in post which you know are due to the noise floor of your gear and not the inherent noise floor of the environment in which the recording was made, don't worry about peaking low and leaving 'too much' headroom.  Leave it lower and reduce your worries.  Once set, I rarely look at the meters anymore except to make sure everything is working.

On stage jazz dynamics can have a significant crest-factor, especially if your microphone position is relatively close to the drumset.  You will need to leave more headroom to accommodate sharp transients over the average RMS level than you would if recording a PA from farther back in the room.  That bit me a few times before I learned to leave more headroom.  Now I don't worry about how much I need to bring up the level in post, as long as primary contributor to the noise at the bottom is still that of the room and not that of my gear.   Classical has an even wider range of dynamics and sometimes an even greater crest factor but it's RMS is more all over the place than jazz so the expectation that more headroom will be requried is sort of already there.  With jazz, the on stage transients above it's less wide typical RMS range tricked me more easily and I suspect the same may be true for other tapers.

IMO, many tapers are overly concerned with peaking high so as to leave minimal wasted headroom.  That's an is an outdated holdover from past best practices and an unecessary risk.

[John Willett]

The future will be (actually already is) digital microphone systems where gain setting is not necessary.  I'm hoping to have mine before the year is out

I have been using digital microphones since 2006.   

Though I do set digital gain so as to get a reasonable monitoring level.

[DSatz]

> set 0 VU on the analog side = -12 dB on the digital side

This was never meant to keep the maximum/peak levels in this rather low range; it was because the VU meters that were standard on professional analog tape recorders respond much more slowly than the peak-reading meters found on most digital recorders. For example, when a VU meter hovers around 0 VU on live program material, momentary peaks in the signal might be 6 - 8 dB higher. And with low-noise, high-output analog tape such as Scotch 206 or 250, Ampex 406 or 456 ("GrandMaster"), or Agfa PEM 468 it was altogether normal to record "into the red" on peaks. +3 dB was the limit of the printed scale on a VU meter, and occasionally one would see (and hear!) VU meters "pin" briefly without hearing gross distortion from the tape.

Actually I seem to recall -15 dBFS being used as the equivalent for 0 VU in the studios I worked in, not -12. That's going back some 30 years and I haven't done the digging necessary to confirm that, but  -15 dBFS would allow the transferred recordings to peak around -3 dBFS or thereabouts--and then once in a while, a peak might even go even higher than that--which was fine, as long as it didn't hit the absolute limit. The "red book" standard for CD mastering actually requires a very small buffer zone below 0 dBFS--a few hundredths of a dB as I recall--although I never heard of a CD master being rejected for that reason. (If anyone here is curious about the technicality of this, I can spell it out in a little more detail since I do remember that part fairly well.) When I prepared masters for CD production, I tried to get the highest peaks to come out at -1 dBFS; it was a point of pride with me.

The thing is, I see some people here claiming that maximum peak levels should remain around -12 even when there is no risk of their going any higher--as if reaching -12 dB and not exceeding that level was the desired result. That is a huge misunderstanding! There's no virtue in having headroom for its own sake. You can't hear headroom. Its purpose is safety--it's there TO BE USED if peaks in the program material go higher than you had expected.

But if you know in advance that no peaks will ever exceed some given level (and in some situations you really do know this), then set your recording levels so that the maximum peaks will get as close to 0 dBFS as you can. The point is always to make best use of the available dynamic range of each part of the "recording chain" because not to do so means, in effect, adding noise to the eventual playback of the recording.

--best regards

[firusan]

I generally use the -12db as a base and make sure it doesn't peak over 0 with the PCM-M10.

[johnfitz]

Do the recording meters reading matter much on a deck like a D50 when running an analog signal in? I'm running a Littlebox into a D50 and the Littlebox only has the single light that changes from green through red without telling you exactly where your at db wise so I only have the display on the D50 for reference.

As an example, there's been times that I've run the Littlebox levels where I want them but the input to the D50 might peak only around -20, -18 or so.

I've never worried about it since I've always thought that adding more gain with the D50 input is essentially the same as adding that volume afterwards in post, that it would affect the recording the same either way.

Am I wrong about that, or is the headroom at the recorder stage as important as the headroom at the pre-amp stage and I should shoot for more optimal levels (say -10 or-8) in the field using the D50's input knob?

[John Willett]

I generally use the -12db as a base and make sure it doesn't peak over 0 with the PCM-M10.

It *can't* peak over 0 as 0dBFS is the absolute limit as at this point it clips.

Actually, it can clip *under* 0dBFS if inter-sample peaks go over 0.

For a 16-bit system, -12dBFS is a sensible 0VU point - for a 24-bit system -18dBFS is better.

You can peak higher than this, of course - with a 16-bit system at -12dBFS, I would normally peak about 6dB higher - with a 24-bit system with -18dBFS I would normally peak about 10dB higher.

This leaves safety headroom and allows for inter-sample peaks.

You can always normalise in the DAW if you need.

[John Willett]

0VU = -15dBFS seems to be a de facto standard for a number of converter manufacturers, but I seem to recall that one of the standards orgs has tried to promulgate -18dBFS, which makes more sense to me.

-12dBFS is the EBU standard for 0VU for 16-bit systems.

For 24-bit systems the EBU standard is -18dBFS - in the USA, the SMPTE standard is to use -20dBFS.

[Scooter123]

Analog like to be pushed into the red--sounded great especially on guitars.

As a matter of fact, there is a DAW plug in which recreates that same sound.

But as others pointed out, digital is a whole different world.  Keep them at -12 and do everything in post.  Never go above 0db

[Gutbucket]

In the digital world-

Some recording situations are more dynamic and require more headroom than others.  You are in control and can either adjust headroom depending on what you are recording, or you can set things conservatively enough that you can use the same level targets all the time.  The standards mentioned above are meant as appropriately conservative, agreed upon conventions.

Using less headroom is only potentially beneficial if doing so raises the noise floor of the room above that of your recording chain.  You can’t do anything about the noise-floor of the room, it sets the lower dynamic range limit. The recorded signal needs to fit between the noise at the bottom and clipping at the top without ‘spilling over’ either end of the range.

There is no need to "leave headroom for post-editing". Once imported, editors use floating point calculations internally providing greatly increased headroom over that of the file.  It is only whenever a file is stored that we need to make sure that the range of dynamics fits within the range of the file format. 


To put it in actual recording terms, I'll relate a rather boring story-

I typically set levels on the Tascam DR-680 (writing 24bit files) so that the meters peak at the small line across the display, which is -18dbFS.  I'm not entirely sure about the ballistics of the otherwise unmarked level meters on the DR-680, but doing that usually leaves a comfortable range of headroom.  Setup for an onstage jazz trio recording, with some microphones arranged pretty close to the drums- about 2' away at closest, I had levels set so the meters were peaking somewhere over that line.  I clipped the input a on a microphone closest to the drum kit, inaudibly, but indicated on the display.  Many other times recording the same band in the same room, same situation, I made sure things were peaking right on the line and it never clipped.  At the time I had been recording a bunch of other less dynamic stuff which didn't require as much headroom and had become somewhat complacent, letting the levels run a bit hot.  It wasn’t major problem but pushing the recording level hotter didn’t benefit me anyway.  Now I always target that -18dbFS line and avoid clipping.

I consider that situation (close to a jazz drumkit with an energetic, dynamic drummer) one where I'll use the most headroom.  That transient rich source at close proximity has a high crest-factor or ratio of peak to average level.  Recording a PA reinforced band from farther back in the room won't require that much headroom.  The crest-factor is much lower and the transient peaks are less wild.  I can safely get away with using less headroom in those situations, but I still use the line on the meter, because doing so simplifies setup, provides consistency and keeps me from wasting time guessing how much headroom I really need, and because I know from experience that the noise-floor of my recording chain will be buried far enough below the noise-floor of the room that I won't benefit from raising the recording levels at that point anyway, the noise floor of the room would just be raised right along with the peak levels.

[SmokinJoe]

To me it's simple.  I run something like -12 so I don't have to stress about it, and the tapes sound just fine. I've learned that from my own experience.

Digital recording is very unforgiving when it clips... it sounds like shit, and is generally unusable.  The occasional snare hit which clips for a few milliseconds is OK, but much more and it starts to sound scratchy.

Almost all of us with a few years of experience have had a learning curve about like this:

• You start a recording, then wander off, and you didn't realize it but the music got a little louder, and when you walk back to check on your deck it's clipping like crazy.  Your listen to that later and it sounds like shit.
• Then you will post "how can I fix this?"  The answer is "you can't really", you can try software tools, but they don't really work. Technically, the information is lost, and there is no getting it back.
• Get angry, delete the file, better luck next time.
• The next show you are all stressed out, watching your meters really close, riding your gains all over the place. You take that home, and the tape gets louder and softer.  Now you spend a couple of evenings trying to level out it out, counteracting all the level adjustments you made at the show.
• After a little while you come to the conclusion -12 is a good point.  You take that home, there are a few louder portions which are up around -6, you boost 6db in post, and it sounds great.  Lather, rinse, repeat.
• At some point you come up with your own lessons learned. One of mine is "expect the main act to be about 5db louder than the opener."  Not always, but frequently it's right.  Another one is "the sound guy always turns the main gain at some point, frequently during the first song." 
  
• Myself, I've gotten to the point where I start off conservatively.  If it's -12 during the first song, that's perfect, if the music gets louder there is still some headroom.  If it's -24, that's kinda low, but let it ride through the first song.  Turn it up between 1st and 2nd songs, that's one step to clean up in post, and it's easier to fix than in the middle of song.  Especially if your deck has clicks of 5 db, you know it's a 5db step.

[tim in jersey]

To me it's simple.  I run something like -12 so I don't have to stress about it, and the tapes sound just fine. I've learned that from my own experience.

Digital recording is very unforgiving when it clips... it sounds like shit, and is generally unusable.  The occasional snare hit which clips for a few milliseconds is OK, but much more and it starts to sound scratchy.

Almost all of us with a few years of experience have had a learning curve about like this:

• You start a recording, then wander off, and you didn't realize it but the music got a little louder, and when you walk back to check on your deck it's clipping like crazy.  Your listen to that later and it sounds like shit.
• Then you will post "how can I fix this?"  The answer is "you can't really", you can try software tools, but they don't really work. Technically, the information is lost, and there is no getting it back.
• Get angry, delete the file, better luck next time.
• The next show you are all stressed out, watching your meters really close, riding your gains all over the place. You take that home, and the tape gets louder and softer.  Now you spend a couple of evenings trying to level out it out, counteracting all the level adjustments you made at the show.
• After a little while you come to the conclusion -12 is a good point.  You take that home, there are a few louder portions which are up around -6, you boost 6db in post, and it sounds great.  Lather, rinse, repeat.
• At some point you come up with your own lessons learned. One of mine is "expect the main act to be about 5db louder than the opener."  Not always, but frequently it's right.  Another one is "the sound guy always turns the main gain at some point, frequently during the first song." 
  
• Myself, I've gotten to the point where I start off conservatively.  If it's -12 during the first song, that's perfect, if the music gets louder there is still some headroom.  If it's -24, that's kinda low, but let it ride through the first song.  Turn it up between 1st and 2nd songs, that's one step to clean up in post, and it's easier to fix than in the middle of song.  Especially if your deck has clicks of 5 db, you know it's a 5db step.

^This.

[yates7592]

^Yep, exactly.