Zoom H6 line out phase inversion problem

[Geoffrey Cox]

Originally Posted by Paul R Johnson

This is getting rather strange.

If you buy two mics that have pins 2 and 3 reversed, I just cannot imagine ANY scenario when you'd notice the inversion. In fact, I'm not even sure any of our usual tricks of flipping channel polarity would reveal it on any digital equipment clearly because of latency. We cannot use a Y split and test in to out against direct because of the A/D and D/A conversion time. With analogue, we can test and check the polarity. With digital - time domain changes take place that sort of spoil the thing.

All I know is that I have never checked the polarity of any of my current digital audio products - and I also feed audio to cameras and no issues whatsoever have ever appeared to cause me any issues. Even worse - when you do spaced mic recordings for stereo you have even more time delays.

The Zooms may or may not have polarity reversed, but I personally won't lose any sleep not knowing if one or the other of mine have this issue?

Geoffrey's original post said:


Is it possible that the real issue here is not phase inversion at all, but just the in to out latency of the zoom? It goes mic-zoom SD card (the A to D) then the output is that digital stream back to analogue - so a few mS is to be expected? Is it inverted or is it delayed?

If it were delayed then I would have noticed that what I needed to do is shift one signal along a few ms but no, that isn't what is happening and I can clearly see the corresponding waveform shapes, albeit with one upside down. The proof is that when I align them as exactly as the software allows (down to sample level) then the phase cancellation is massive. Note I double-checked this using a single mono mic only.

I'll say again this isn't a major problem. And fixing it is easy by flipping one signal in the software. Serious audio folk would however note that this should not be necessary as there should be no inversion in the first place and it is worth knowing what the root cause is if it effects all signals coming form the Zoom line out for future reference.

[Don Palomaki]

I work alone so having a pair of mics somehow in a different place is practically unworkable - they have to be mounted on the camera.

For a one-man-band shoot: Some would suggest only the mic gain controls need to be on/at the camcorder, the mics can be anywhere. And many would argue the poet should have a lav mic, not a camcorder-mounted mic. Using a camcorder mounted mics might introduce handing noise if one is not careful. (Perhaps a wireless lav to give the poet and camera more freedom to move.) It becomes a matter of the art of mic selection and placement.

But then you already knew that and chose to go the way you did. Please just don't expect others to understand your reasons without clear explanation.

[Geoffrey Cox]

The poet does have a radio lav mic. There are three mics going into the Zoom. I mentioned this when I said a few posts back: 'Inevitably the voice is also picked up by the spaced pair as well as the mono mic.' This was the plan from the very beginning because clearly the voice is the most important element.

I am sorry if this was not 100% clear but the whole point is that this thread was not about my project but a specific issue with the zoom line out and my mic set-up is not relevant so I never went into that detail so as not clog up the main point. The topic has since morphed into a different discussion which is fine but I cannot be blamed for not giving full info on a topic I never posted about in the first place and then even attacked for being the sort who deliberately withholds information!

[Pete Cofrancesco]

You strike me as someone who is thin skinned, perceiving attacks where there are none.You're fixating on unimportant technical details while ignoring the big picture of using the proper setup. This is why we are asking these questions because they matter more than the phase of the output. The two logical approaches to spoken word outdoors are lavalier with under/over covers or a boomed shotgun inside a blimp.

[Geoffrey Cox]

How do I use a boomed shotgun if I am working alone, something I stated quite clearly? It is a pointless suggestion. I am using a lavalier (COS-11D with Sennheiser G4 system). I have thought long and hard about the best setup and tested various possibilities. This involved comparing various signal levels which is where I came across the phase inversion and wondered if anyone else had any thoughts on that specific matter. I never asked for advice about the general setup as I had already spent a lot of time testing possibilities and arrived at my current configuration. I am not ignoring the big picture of a proper setup at all so you are wrong to say that (again).

Frankly wish I had never posted anything at all.

I'm out.

[Don Palomaki]

I agree the thread has morphed from "does the Zoom have a phase issue" to more of what is a good way to acquire audio for the shoot whether or not the Zoom has an issue. Probably in part because most folks posing questions here are seeking solutions or work-arounds rather than confirmation of an observation.

I read the boom pole suggestion as being a generic approach for outdoor work, not as a suggestion for an one-man-band.

All this points out why Hollywood-class production add ambient and other sound effects in post where it can be controlled and synced to the image and not rely on mother nature and passing traffic to behave. After all, the background/ambient should complement the image. Except for things like legal proceedings and select documentation efforts (and perhaps some artistic demands not related to viewer perception) it need not be time and/or spatially coincident with the shoot.

But video is an art form, so to each their own.

[Pete Cofrancesco]

I work almost exclusively solo and I often use a portable boom stand such as this https://www.bhphotovideo.com/c/product/546705-REG/Manfrotto_420B_420B_Combi_Boom_Stand.html/BI/2855/KBID/3801
If its really windy I bring a c-stand that has a boom holder https://www.bhphotovideo.com/c/product/885688-REG/Auray_BPH_BOOM_POLE.html/BI/2855/KBID/3801
I'm surprised that I even have to suggest this. I thought it would be common knowledge. For interviews and even for this a poetry recital the subject isn't moving so you don't need a boom operator.

I don't understand why listening suggestions from like minded people makes you mad. The day when you say I know everything is the day you stop learning and growing. I always keep an open mind. But that's just me...

[Paul R Johnson]

I have confirmed that the Zoom H6 does indeed have reversed polarity on the line out. The SD card recording is normal.

I also checked the sources direct to the tascam interface.

Microphone direct into the Tascam 1604 interface. a tap on the windshield produced a negative going peak in Cubase.
Microphone recorded on the H6 SD card, read into the computer, inserted into Cubase also has a negative going peak to the tap.
Microphone connected to H6 input, and the 3.5mm line output connected to the Tascam produces a positive going peak.

Interestingly, swapping the H6 for an H4 produces a negative going peak, as with the other connections.

Conclusion
The H6 does indeed have an inverted output, but this is not a standard in the Zoom recorders, as the H4 does not do this.

My H4 gets little use, but the H6 does, and I would never have found this out. I tried all the handheld microphones I have in the video studio - quite a few from all eras. Only one microphone produced a positive going waveform on the tap test - an old Shure SM61. So this mic - an omni - has, with it's brother, been used by me for years and I have never noticed that difference.

Geoffrey is quite right, the Zoom H6 output, not recording internally, is reversed - but as to why? We will never know.

[Pete Cofrancesco]

Paul good detective work. Zoom is a bit of an odd duck maybe because they initially built it for musicians. For example, the xlr input permanently set to mic level. If you get xlr line out from a sound board you must use a 1/4 jack

[Patrick Tracy]

Originally Posted by Pete Cofrancesco

Paul good detective work. Zoom is a bit of an odd duck maybe because they initially built it for musicians. For example, the xlr input permanently set to mic level. If you get xlr line out from a sound board you must use a 1/4 jack

That's true on the H4s that I've used, but it's not true on my H5, which has a a software selectable 20 dB pad making it compatible with +4 line level via XLR. I have not yet seen a clipped waveform since I started using that setting.

[Pete Cofrancesco]

Originally Posted by Patrick Tracy

That's true on the H4s that I've used, but it's not true on my H5, which has a a software selectable 20 dB pad making it compatible with +4 line level via XLR. I have not yet seen a clipped waveform since I started using that setting.

Good tip. I'm not sure if I knew this at one time but forgot. So is taking mic level and padding it to line is that proper or good enough for field work? I'm not crazy about software setting like this because if you don't use a recorder on a regular basis you could easily forget pad is on and the time you plug in a mic...

[Patrick Tracy]

Originally Posted by Pete Cofrancesco

Good tip. I'm not sure if I knew this at one time but forgot. So is taking mic level and padding it to line is that proper or good enough for field work? I'm not crazy about software setting like this because if you don't use a recorder on a regular basis you could easily forget pad is on and the time you plug in a mic...

I think it would be fairly obvious that you're running the preamp gain a lot higher than normal to get proper levels.

[Pete Cofrancesco]

Originally Posted by Patrick Tracy

I think it would be fairly obvious that you're running the preamp gain a lot higher than normal to get proper levels.

It's fine just an annoyance because I use the H5 for a very specific thing, unattended recording of the board feed. Most of the time you have student or amateur board operator who is struggling to figure out how to send an out, neither I nor they know if it's mic or line.

I've heard Zoom will be releasing a new recorder that will be better suited for this type of work because it has 32bit float.
https://www.bhphotovideo.com/explora/pro-audio/news/zoom-f3-a-pro-level-palm-size-32-bit-float-recorder-for-xlr-mics/BI/2855/KBID/3801

[Don Palomaki]

if you don't use a recorder on a regular basis you could easily forget pad is on

Perhaps print a small check lists and attach it as a reminder?

[Geoffrey Cox]

Originally Posted by Paul R Johnson

I have confirmed that the Zoom H6 does indeed have reversed polarity on the line out. The SD card recording is normal.

I also checked the sources direct to the tascam interface.

Microphone direct into the Tascam 1604 interface. a tap on the windshield produced a negative going peak in Cubase.
Microphone recorded on the H6 SD card, read into the computer, inserted into Cubase also has a negative going peak to the tap.
Microphone connected to H6 input, and the 3.5mm line output connected to the Tascam produces a positive going peak.

Interestingly, swapping the H6 for an H4 produces a negative going peak, as with the other connections.

Conclusion
The H6 does indeed have an inverted output, but this is not a standard in the Zoom recorders, as the H4 does not do this.

My H4 gets little use, but the H6 does, and I would never have found this out. I tried all the handheld microphones I have in the video studio - quite a few from all eras. Only one microphone produced a positive going waveform on the tap test - an old Shure SM61. So this mic - an omni - has, with it's brother, been used by me for years and I have never noticed that difference.

Geoffrey is quite right, the Zoom H6 output, not recording internally, is reversed - but as to why? We will never know.

Thank you Paul. I'm not going mad then!