Zoom H4N Pro as audio interface: popping sound in certain frequency range

David Wise

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Hello all,

I have a Late 2013 Macbook Pro and a Zoom H4N Pro that I'm trying to use as an audio interface with the Zoom's built-in mics, primarily recording myself on saxophone. It works completely fine the vast majority of the time, except when I play in the upper range on alto saxophone, from high D to F on alto (F to Ab in concert pitch), with frequencies ranging from 698 to 830 Hz. When I play in this range I get a popping/clicking/crackling noise at regular intervals of about a half a second within the tone. It may continue higher past that range as well but I haven't checked.
Here's a link to a short recording for reference: https://drive.google.com/file/d/1bc0-Bf49dvK1yR_l4vTEAXmvL_zmmWPg/view?usp=sharing

I have already tried several steps trying to troubleshoot/isolate the issue, here's what I've done so far:
- ensured the signal is not clipping, it is well below the threshold according to both the Zoom's built-in signal monitor and the Sound prefpane's monitor, and happens regardless of volume
- ensured the Zoom, Audio MIDI Setup, and DAW app settings are all synchronized at either 44.1 or 48 kHz
- tried recording in several different applications, including Logic Pro, GarageBand, Audacity, and QuickTime Player
- tried recording both in Mac OS 11.6.2 and booted into BootCamp running Windows 10 (using Audacity)
- tried different buffer sizes in Audacity, such as 0, 10, 100, 1024
- tried resetting SMC and PRAM
- tried connecting to both USB ports directly, also tried connecting through a USB hub
- tried 2 different USB mini-B cables, one that I've had forever that came with some unknown device, and one universal USB cable with multiple adapters
- tried rotating the Zoom built-in mics from 90° to 120°
- tried powering on Zoom from battery power before connecting USB
- ensured Zoom is running latest firmware 1.10

The frequency of the popping was not exactly the same with every variable I changed, but it was always present, and always only in that specific frequency range. I know I have a couple workaround options, such as just using the Zoom to record on its own, or using the Zoom's recording standby mode monitoring with an 1/8" cable running from the headphone line out to another cheap-o 1/8"-to-USB audio interface I have, but that yields slightly lower audio quality overall. I haven't tried yet using an external mic connected to the Zoom as a USB interface, because the built-in Zoom mics are actually the highest quality mics I presently own.

Any ideas? Could it be that I need a higher-quality USB mini-B cable, if that even exists? Or it is just some hardware problem with the Zoom itself, or with my Mac?
 

Paul Johnson

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I'm not hearing any popping - just the strange modulation and distortion. First thing is to record onto the Zoom's card and then read that into the MacBook - this will cut out the processing stages in the zoom, in case its a codec issue, but I have the feeling what it is, is simple overloading of the internal mics. How close were the mics to the sax? It sounds very close and very loud. Is the artefact there when you play quieter? If you hear the artefact when you record direct to the card then this points to the problem being very early on in the recording chain. Condensers, when they are overloaded by volume often make these odd warbles. First thing I'd do is repeat the test, moving the recorder to a more distant location and see what the purity is like.

It's also possible what you are recording is arriving at the mics by two or more routes - so with the octave key pressed, most sound is obviously coming from just the lower holes, but there is a little sound coming from the top, and the two could be coupling. Again, changing mic positions might help. If your phone has a SPL app, it could be worth just seeing how loud that playing style registers. The lack of vibrato suggests you're using a higher number reed and a big lung full of air - so try recording the same notes but play more quietly and see if the unpleasant artefact reduces.
 

David Wise

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What do you mean by strange modulation and distortion? The sound I'm describing is a rhythmic sort of tapping/clicking noise that happens at regular intervals. It's not present on the first 2 (lowest) notes in the recording, but is present on the last 3, especially the last (highest).
Also I get what you're saying about the mics, but I should have made this cleared in my post, this only happens in USB Interface mode, the artifacts are NOT there when I record directly to the Zoom's SD card, which tells me it is not a mic/level/distance/soundwave problem, but something later on. I can do some more testing to be sure, but I'm pretty sure I've eliminated the mics as the source.
 

David Wise

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I just did more testing. No matter how quiet or how far away I play with it in USB mode, the popping is still there. I would say the volume of the popping decreases and increases in conjunction with the volume of the tone. Conversely, if I record straight to the Zoom, I can blast the hell out of it from any distance at any volume and it works perfectly with no artifacts.

I also just dug up my white MacBook from 2006 and tried it on there; same thing, so I know it's not a problem with my Mac.
 
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Rob presson

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could you share the zoom direct to card recording for comparison?

I'm not hearing any popping sound on my phone, which I should hear popping if there is any. I'm hearing modulation / distortion as well. listen to the example on this article for what popping sounds like https://www.filmeditingpro.com/why-does-audio-pop-how-to-fix-it-fast/

in my car it sounds fine.


try playing this on your phone, car, or other device to see if you hear the thing your describing. perhaps it is your playback setup? I will do the same. also, try recording a different instrument at these notes to see what happens.

make sure you turn off compression /limiting on the zoom. set input mic level to say 5 out of 100. check the input levels that they are below maximum.

how do you have your x/y mics set as far as degree of recording?

take a photo showing the mic and sax distance /position and share that with the recording into memory card for comparison.

please be open to the responses, we are here to help but sometimes don't have the same context, experience, nomenclature, or assumptions. Paul seems to be on point from my perspective.

.. on another note (ahem) the recording is not at all natural sounding, meaning mic placement is way too close for the type of microphone. I have the zoom and never tried to use it as an audio interface, thanks for the good idea.

For the record, my experience is thirty years of live audio for arena through club gigs for A list artists and a decade of studio work.
best regards!
 
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David Wise

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Hi, thanks for your response. I see what you mean the way "popping" is used in that sense, I was unaware it had that universal meaning, I was just trying to describe the sound I was hearing. By modulation/distortion are you referring to the rhythmic tapping that I'm talking about (as opposed to a quality applying to the sound overall)?
I have double-checked listening on various devices, same results.
I can re-record something direct to card later today or tomorrow for comparison when I have time, I didn't save those clips. I'll also try on a couple different instruments, maybe soprano/flute/trumpet.
I don't have the Zoom in front of me right now, don't remember where the compression/limiting setting is, but I don't think it's anything I've ever turned on; I'll check on that later. I did have the input levels pretty low and played around with them quite a bit to make sure it was nowhere near maxing out, I think they were at 30 for that recording.
I tested the mics at both 90° and 120°, it had no effect.

Yeah, I'm aware the mics were in a less than ideal position and distance on that recording, it was just something I did really quickly while messing around with a million variables, but I did experiment with placement a lot trying to fix this, ranging from being right up on it to the opposite side of the room.

When you said "Dave seems to be on point from my perspective" are you talking about me, or someone else? I'm confused.
 

Riley Casey

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Upon listening to the recording file of the sax playing a scale I hear a low bit rate mp3 recording but no distortion or noise. Post a wav file version and maybe I can hear something more subtle but on my record station monitors it sounds like a poor recording not a defective recording.
 

Paul Johnson

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Oct 27, 2012
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Did you hear this when you play the Zoom's SD card in the software of your computer? You didn't say. I'm not hearing any rhythmic elements that jump out at me
EDIT
I CAN hear this when I listen on my MacBook and not the studio system. I think it could be there on the big system but It's not obvious.

On the MacBook using the built in music app, I can hear it. I then tried it on the MacBook in audition - and it's like in the studio, very very low.

I assume you are hearing it on the uncompressed format you're recording in? Are you sure the noise is there before the conversion to mp3?

I think this could be a codec issue maybe? Is the noise there when you play normally - not a belter of a scale. The file in audition is also quite hot. Well worth repeating this test with the record levels quite a bit down. You didn't clip but you came very close and maybe with the strident tone of the sax, it's just revealing compression difficulties in your mp3 conversion, hopefully missing in the .wav the thing probably started in?

Do another recording with the gain knocked down, or just play a bit more quietly so we can assess the quality - it's so loud my wife could hear the sax across the room until I found the volume to turn it right down - its MEGA loud, which cannot help the conversion,
 

David Wise

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Hi Paul, thanks for checking it more. The sound is there before any type of conversion or export, happens during immediate playback within any of a number of apps, Logic, Garageband, Audacity, etc., and on multiple operating systems (tried Audacity in boot camp Windows 10). And yes, did try listening back to the Zoom SD's recording transferred onto the Mac via USB storage mode, sounds fine.

I have listened back on multiple devices: speakers plugged into Mac 1/8" audio port, Apple Earbuds plugged into 1/8" audio port, and two different pairs of Bluetooth headphones. The only playback where I canNOT hear it is trying to listen directly from the Mac's crappy built-in speakers, because I can't hear that level of detail from those speakers.

The noise is not there when I play in the rest of the range of the alto sax at any volume, or in any range of the tenor sax at any volume. As in the recording, the noise is not present on the first 2 notes, only the last three.

I'll re-do some of the tests I did before at different volumes and distances, as well as trying some other instruments in the same range, and share them here, just haven't had a chance yet.
 

David Wise

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Ok, did even more testing, determined it happens regardless of volume, distance, input level, or instrument. Was able to duplicate the same thing in every circumstance on both alto sax and flute in USB mode, and was unable to reproduce it under any circumstance when recording direct to SD. The noise DOES increase and decrease in volume in conjunction with the volume of the recording, but as far as I can tell it is always present. It also continues farther into the upper range as I went higher on flute, and seems to eventually tail off near the upper end of the flute's range. This time I actually also encountered a brand new artifact that I've never heard before, a randomly occurring brief buzzing noise.
Here's a new recording, edited together from different tracks, narrated throughout, laid out in the following order:
Alto sax in USB mode recording level 30 near (≈1 foot from mic), far (≈10 ft from mic); recording level 5 near, far; alto sax recorded direct to SD level 30 near, far, level 5 near, far; flute in USB mode level 30, flute direct to SD level 30

If anything is unclear please let me know. Thanks!
 

Rob presson

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it's me but I'm confused. is this recording to the internal storage card that didn't have the issue, or another recording using zoom as an audio interface?

we need to hear a recording that doesn't have the problem to compare to your audio interface. can you provide two recordings

1) a recording of something saved to storage card
2) a recording of the same exact source, same distance, same settings, through your interface

3) did you verify settings of the compressor /limiting?

thanks
 

David Wise

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Rob, that's what that recording was, comparing recording with the Zoom as a USB interface to recording directly to the Zoom's internal storage card. When recording directly to the Zoom, it doesn't have the issue.
In that recording you can hear alto sax with a variety of variables recorded as a USB interface, then a repeat of the exact same variables recorded direct to the Zoom's internal storage. That is followed by a clip of flute recorded as a USB interface, followed by flute recorded with the same variables direct to the Zoom's internal storage.
In every instance, the noises are there when using the Zoom as a USB, and in every instance they are NOT there when recording directly to the Zoom. Those clips are provided as comparison to hear a recording that doesn't have a problem.

I was not able to find any compressor/limiter settings on the Zoom itself.
 

Rob presson

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I have the h4n and it has a limiter and compressor that can be turned on with internal and external mics. I assume the pro has it as well. Check: https://www.manualsdir.com/manuals/696718/zoom-h4n.html?page=70

So check your manual. It does have it, and it is likely WHY there is a problem.

On my zoom the mic goes from 1-99 I believe, and for recording sources that are NOT speech from twenty feet I use 2-5 as the input volume, however, I have not tried this like you are using it. If there is a compressor or limiter turned on (default I believe) and you set the input volume above xx (8? 10? ) then you will get exactly what you are hearing.

With it enabled, you can record at too high a volume and it will work but there will be artifacts/issues when you push.

Your issue is most likely due to not having a proper gain structure or there is something in the signal path that is changing things.

BTW, to me "USB mode" is confusing. interface vs. an internal recording.

I asked for two recordings one each way so that I could try doing a null test (google it) to see what the actual differences were. The only way to do this though would be to simultaneously record to internal storage AND record to your DAW and copy the raw output file to two separate files.

hope this helps.
 

David Wise

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Just checked, those settings are all off already (Lo Cut, Comp/Limit, Level Auto, Mono Mix, Phantom, Plug-in).
Also, those settings are not available in interface mode, USB interface mode has its own dedicated menu with much more limited selection (Effect Tuner, Monitor, Phantom, Plug-in); I have everything set to off except Monitor.

And yeah, I looked up null test and see what you mean, but the Zoom is not capable of recording to both at the same time, so it's kind of a moot point I guess. The best I can do is alternate recording as interface and internally.
 

Rob presson

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since there are different settings for each, I don't think there is much point. Contact zoom for assistance perhaps, I am stuck.

I would highly suggest getting yourself a dedicated mic / audio interface for home recording, borrow, or have someone with the gear do a test to see if it happens outside of the zoom. It could be either a metering issue when used via an interface, but ultimately only the vendor would know why you get different results.

best of luck
 
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