R16 level setting and stereo files

Discuss the Zoom HD and R series. Please don't "post and run". Participate in the discussion. Thanks.
Post Reply
hoodoo voodoo
dues paid
dues paid
Posts: 202
Joined: Mon Nov 16, 2009 7:17 pm

R16 level setting and stereo files

Post by hoodoo voodoo » Sun Sep 23, 2018 7:48 am

1....I've been watching a few videos on recording into DAW's like Reaper and the recommendation is to main average input level of -18 and not exceeding -12 to avoid overloading the preamps. So when using the R16 as audio interface into typical DAWs would that be recommended or standard practice ? Contrast that with using the R16 as a standalone recorder with internal SD card.

All of a sudden the R16 manual suggests to increase the input gain so that the red overload light flashes occasionally, which would give one to assume we're now recording at an average of -6 (?) and that occasional overloads to 0 are ok ?

One of these recommendations is presumably wrong (-18 to -12 or -6 to 0)? Or alternatively is it possible or likely that the R16's input levels are 'internally scaled' invisibly to the user, so that the occasional red flashes are in fact indicative of a "true recording level" closer to the Reaper recommendations ?

Zoom would not deliberately be leading users to record at levels which produce preamp distress and subsequent mix distortion.....or are they simply calibrating input levels to replicate what analog tape users would be more familiar with ?

2 ...When I record acoustic music concerts...eg chamber music groups or orchestra, I often use a simple spaced stereo mic pair (ORTF or similar) in front of the musicians. I tend to record this to 2 mono channels of the R16, panned hard left and right, and then transfer the 2 SD card files to computer for editing in Reaper. Would it be more advisable to make a stereo pair of the 2 inputs in the R16 prior to recording, to create a true stereo file ?

In recording a continuous concert of 60-90 mins length, is it conceivably possible the the 2 mono files could slip out of sync with each other, even by a small amount, leading to a slight phase shift between the 2mics of the pair ? If I took the trouble to 'lock them together' by stereo linking them as a pair in the R16 before recording would such 'slip' or loss of sync lock be lessened ? Does creating an R16 pairing somehow interleave the 2 files together....and does it result in a smaller file size than if the same audio stream were recorded as 2 discrete mono files, as I'm doing now ?

Thanks for your input to these 2 questions !
0 x

User avatar
sciurius
senior member
senior member
Posts: 100
Joined: Tue Jan 24, 2012 4:37 pm

Re: R16 level setting and stereo files

Post by sciurius » Sun Sep 23, 2018 9:33 am

Q1: As I understand, it is safe to turn up the gain until the red light flashes occasionally. This will give a slight distortion on load passages. Personally, I turn the gain a bit lower until there are no flashes anymore. This gives maximum dynamic range for the recording.
As long as there are no distortions, the audio files can always be postprocessed without loss.

As for Q2: There is no distinction between a stereo and two mono channels. You can combine and separate at will. Having one audio file is easier to manage. I use Ardour, and it lets you import a stereo channel into two mono channels.
As for 'out of sync': I'm pretty sure this will not happen since both tracks are recorded with the same digital precision.
I sometimes record on the R24 simultaneously with my H2n, and I measured a hardly noticable skew of less than 0.2 seconds on a one hour recording. See viewtopic.php?f=15&t=24927&p=212834#p212834 .
0 x
Zoom H2n, Zoom R24, Ardour, Audacity on Linux (Fedora)

Wulfraed
The Force
The Force
Posts: 3174
Joined: Wed Jan 23, 2008 8:18 pm
Location: Lowell, MI

Re: R16 level setting and stereo files

Post by Wulfraed » Sun Sep 23, 2018 10:26 am

hoodoo voodoo wrote:
Sun Sep 23, 2018 7:48 am
One of these recommendations is presumably wrong (-18 to -12 or -6 to 0)? Or alternatively is it possible or likely that the R16's input levels are 'internally scaled' invisibly to the user, so that the occasional red flashes are in fact indicative of a "true recording level" closer to the Reaper recommendations ?

Zoom would not deliberately be leading users to record at levels which produce preamp distress and subsequent mix distortion.....or are they simply calibrating input levels to replicate what analog tape users would be more familiar with ?
The PEAK indicator flickers on analog signal of 0dB (or higher) (page 21 of the R16 manual). The flicker should only occur for transient sounds of very short duration, for which clipping may not matter. Probably should have a dim room to see the flicker, since anything long enough to register in higher lighting is likely going to sound distorted (compare the click of a pick hitting a string vs the actual string note).

If you are NOT using any insert effect, the level meter should reflect the digital level, and since you do not want to see the red LED on the meter, you'd have to turn down the input GAIN. With an insert effect, you adjust the algorithm output level using the effect parameters -- some effects can have the effect of a higher output level than input (say, boosting the EQ -- in the input is just at 0dB and you add 6dB EQ, you now clip in the digital realm, so you have to adjust the overall effect down appropriately).

Analog tape "saturates" before clipping, digital A/D converters do not. Using analog meters on a tape unit one aims for 0dB -- the meter movement is too slow to register the short flickers that might exceed that level, but the tape saturation effect sort of "compresses" those peaks. I had a unit with digital meters -- as I recall, it had a marker at +3dB which was given as the target recording level, as the digital meters could flicker on the peaks.

-12dB is the target point shown in my video cameras (. . . * . . | where | is the 0dB point, * is the larger dot at -12dB, . are smaller dots every 3dB)

On the discontinued HD-series, each input still has a GAIN control, with the same instructions for "lights up occasionally" -- but all active inputs go through a single RecLevel control, and that has a CLIP indicator that should not flicker...


The archaic BOSS BR-600, and its replacement, the BR-800, however, have PEAK indicators that flicker at -6dB -- giving a slightly safer margin for the peaks. Those inputs also go through a single record level control, and one has to monitor the level meter to avoid clipping. The BR-800 manual goes on to specify a target "within the range of -12dB (between -24 and -6) -- 0dB".

Zoom's 0dB PEAK indicator doesn't allow for errors -- you really do need it to only flicker on the very loudest parts of the performance. BOSS's -6dB PEAK gives more safety margin.

Both companies expect one to adjust recording levels in the digital realm to avoid the maximum meter. However, where the BOSS devices (and Zoom HD) have explicit recording level controls, the R-series only has a recording level control as the final part of an insert effect. If not using an insert effect, one has to reduce the GAIN control to adjust the recording level.


2 ...When I record acoustic music concerts...eg chamber music groups or orchestra, I often use a simple spaced stereo mic pair (ORTF or similar) in front of the musicians. I tend to record this to 2 mono channels of the R16, panned hard left and right, and then transfer the 2 SD card files to computer for editing in Reaper. Would it be more advisable to make a stereo pair of the 2 inputs in the R16 prior to recording, to create a true stereo file ?
I would... it makes it easier to adjust monitoring levels also as typically one fader will control both channels, and produces one file so that editing is applied the same to each channel.

In recording a continuous concert of 60-90 mins length, is it conceivably possible the the 2 mono files could slip out of sync with each other, even by a small amount, leading to a slight phase shift between the 2mics of the pair ? If I took the trouble to 'lock them together' by stereo linking them as a pair in the R16 before recording would such 'slip' or loss of sync lock be lessened ? Does creating an R16 pairing somehow interleave the 2 files together....and does it result in a smaller file size than if the same audio stream were recorded as 2 discrete mono files, as I'm doing now ?
You've already got TDOA phase effects from using ORTF microphone placement (it takes a fraction of a millisecond for a sound coming from one side to cross to the second microphone -- work out speed of sound and the distance between microphones). One reason all the hand-held field recorders try for XY microphone placement -- all stereo effect relies solely upon angle to the sound source (and attenuation by the element patterns), rather than having both angle to the source and TDOA.

As for the digital realm of things... There should be no detectable "slippage" in the resulting files, since all the data samples are based off of the processor clock. The clock may drift, but the samples for each channel will be taken so close together they effectively drift at the same rate.

Linked (stereo pair) creates a single stereo WAV file containing both channels.

NOTE: the clocks in the Zoom devices are not the most precise (pretty much any mid-range video recorder will have a more precise clock, simply because VIDEO samples have to be on a much tighter schedule). Many years (decades?) ago I once ran a test using: two video cameras (high end consumer $800, and a "pro-sumer" $3500), a SuperScope/Marantz audio CD recorder (moderately high-priced as the SuperScope variant included the ability to directly copy copy-protected CDs -- no playback conversion to analog followed by record conversion to digital), a Zoom H2, BOSS BR-600, Zoom HD16, and I think I had the R16 at the time.

Started all devices, then did a hand clap as a "clapper board" sound... Waited 30 minutes, did another hand clap, then shut down the devices. I then transferred all tracks (and video) into Vegas Pro, and adjusted the position of the tracks so that the starting hand clap was aligned. Then moved down the time-line to the 30 minute area to compare the alignment of the ending hand clap.

Both video cameras were within a video frame of each other, and the SuperScope was off by less than 5 frames (30 frames per second). The BOSS device was off between 5-10 frames. The Zoom devices were between 7 and 15 frames off. I forget which side, but one brand had a clock that was running fast -- so recorded MORE samples in the given time, hence the alignment to video put the hand clap later; the other brand tended to a slower clock -- recording fewer samples, and putting the hand clap before the video.

A 15 frame mis-alignment is half a second. Extrapolating that would be a full second off in a one-hour recording. Only of significance if one is recording audio to be matched up with a separate video (which is what my intention with the HD16/R16 had been -- four channels for "surround" and four left for, say, narration or "actors").
0 x
--
Baron Wulfraed
IISS Elusive Unicorn (detached)

Superscope PSD-300; BOSS BR-600, Zoom HD16cd, Zoom R16, BOSS BR-800, Zoom H2n
Now to (re)learn to play an instrument

Lanikai S-C, SMC-E; GoldTone Banjo-Uke; Flatiron 1C, A5; Big Muddy M1-W; Ovation MM68AX, CSE-44; Orpheus Valley Fiesta FS; Taylor NS-72ce, T5-S1; Musima (4st, 20 fret, tenor-tuned) banjo; bongos, dumbeks, bodhrans, hand drum, tambourine; recorder: soprano, alto, tenor; Cedar Flute (5 sizes); Pennywhistle (3 keys); Casio keyboards

hoodoo voodoo
dues paid
dues paid
Posts: 202
Joined: Mon Nov 16, 2009 7:17 pm

Re: R16 level setting and stereo files

Post by hoodoo voodoo » Sun Sep 23, 2018 8:58 pm

Thank you both, sciurius and Wulfraed, for your answers. I think I'lll opt for the more conservative Reaper recommended -18 to -12.....at least the R16 has a -12 dedicated LED which I can use as a reference point. As the Zoom preamps get a bit noisy at the higher end of their range, running them lower and boosting level digitally later in the computer seems a good policy ? The other issue is getting a good bit depth, but I tend to record at 24 bit so that should be ok even down at -18/-12 ?

Stereo files seems like a good way forward too ! I appreciate your advice :applause:
0 x

Post Reply

Who is online

Users browsing this forum: No registered users and 4 guests