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Australian Image (Ray)

Understanding Microphones

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Audio is something quite new to me and there's one thing that I'm struggling to come to grips with at this moment. The short of it is, I have a Zoom F6 field recorder that's capable of recording in 32 bit and I want to use an on-camera mic to transmit a signal to the F6 and have it record in 32 bit.

Now the issue is, as far as I understand, that most wireless transmitters only transmit either 16 bit or 24 bit signals. However, I've come across a wireless transmitter, NUX B3, that's capable of transmitting a 32 bit/48 kHz signal. But it isn't capable of providing phantom power to any XLR mic.

The Rode NTG 4+ is able to be self-powered, but I can't find any specs on its bit depth. My assumption is that it's analogue only, so then it doesn't matter, but I really don't know. My quandary is, what sort of XLR mic is capable of matching the NUX B3 so that I get a full 32 bit system?

Any and all assistance would be appreciated.

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Any analogue mic will be fine. That 32-bit audio is a concept that only exists at the point where that analogue signal is converted into a digital one.

That NUX B3 thing look interesting. Tidy.

If you really want to get fussy here, you need to understand the quality of the ADCs (analogue to digital convertors) and pre-amps. They will be the bits that make more difference than it being 24-bit or 32-bit, I think.

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Thanks. My problem though is identifying which mics are analogue. I'm assuming that it applies to any XLR mic, but I haven't been able to confirm that.

Yes, the ADCs and pre-amps are important and Curtis Judd advised me that those in the Zoom F6 are of high quality, which is why I'm able to pull good audio from the F6.

What I'd like to do is make full use of the F6's 32 bit capability, mainly because of where and how I shoot.

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2 hours ago, Australian Image (Ray) said:

Thanks. My problem though is identifying which mics are analogue. I'm assuming that it applies to any XLR mic, but I haven't been able to confirm that.

Yes, the ADCs and pre-amps are important and Curtis Judd advised me that those in the Zoom F6 are of high quality, which is why I'm able to pull good audio from the F6.

What I'd like to do is make full use of the F6's 32 bit capability, mainly because of where and how I shoot.

Curtis totally knows his stuff. I highly reccomend any advice he gives that pertains to audio. 

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Pretty much EVERY microphone is analogue. There are very few digital microphones out there (with ADCs built in), and the ones that exist are usually very expensive.

Such as: https://schoeps.de/en/products/shotgun-microphones/cmit-series/supercmit.html which costs over £3000.

Battery inside doesn't mean it's digital or there is any digital processing - it's typically just for phantom power.

Of course, these days, most wireless packs are digital. But the microphones themselves aren't.

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Curtis has responded and stated as much. I did think this was the case, but wasn't absolutely certain. The issue that I have is if I get the NUX B3, it won't power XLR mics that need phantom power, so it has to be one that takes a battery. That doesn't leave many moderate cost mics to choose from.

The other thing is that the mics that I have, the Rode VideoMic Pro+ (possibly) and VideoMic NTG (definitely) are limited to 24bit, so they won't accommodate the 32 bit float recording that the Zoom F6 provides. Unless I have all this wrong and it doesn't matter what the mic transmits meaning that the Zoom F6 will handle any signal and just refine it to 32 bit. 

I must say that Curtis has been extremely patient and ready to answer my questions. I don't think many would be so accommodating.

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@Australian Image (Ray), as far as I can tell, the 48KHz 24-bit specification of the Rode VideoMic NTG only applies if using the USB output (and the internal processing).

If you're using the minijack output then surely it's just analogue, and there is a DAC in the microphone converting that digital signal (post the internal processing) that would have otherwise been sent via USB into an analogue signal to go down the minijack?

So it goes:

Mic capsule > ADC > 24-bit 48KHz internal processing > USB

or

Mic capsule > ADC > 24-bit 48KHz internal processing > DAC > minijack (analogue)

 

The Rode VideoMic Pro + doesn't appear to have any digital output, so will always be Mic capsule > ADC > internal processing > DAC > minijack (analogue). The USB appears to be only for power.

 

So, if connecting the NTG to your Zoom F6 via USB (is that even possible?), recording at 32-bit is questionable (arguably pointless... I don't know). You may as well keep it at 24-bit. If connecting either mic via their minijack then it's an analogue signal, and so there will be benefits to recording 32-bit float.

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I think you may be correct. I received my mini-XLR to 3.5mm patch cables on Friday and tested them out briefly with the NTG and Pro+ and the audio response was dramatically different to using the 3.5mm input ie much stronger and clearer. I mean the difference was like night and day. I intend to do more testing in the next couple of days to see how things pan out now that visitors have gone.

I did do an early test using the NTG on the F6 with an XLR to 3.5mm patch cable, but it wasn't an extensive test because it's not how I want to use the system. I also bit the bullet and bought a NUX B3 (as I can always use it regardless) and once I get that, I can positively find out the differences. In the mean time I'll be doing some more comparisons with the NTG on-camera and attached to the F6.

If this works out, I'm going to be very one happy chappie.

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On 5/30/2020 at 5:17 AM, Nezih said:

Pretty much EVERY microphone is analogue. There are very few digital microphones out there (with ADCs built in), and the ones that exist are usually very expensive.

Such as: https://schoeps.de/en/products/shotgun-microphones/cmit-series/supercmit.html which costs over £3000.

Battery inside doesn't mean it's digital or there is any digital processing - it's typically just for phantom power.

Of course, these days, most wireless packs are digital. But the microphones themselves aren't.

every mic is analogue, unless it is a laser microphone that is sampling the diffraction of the beam or something.  For example the Neumann Solution D microphones are analogue microphones, but marketed as digital.  There are a few companies that offer AES 42 digital mics - the AES specification that has been embraced as the physical transport of digital signaling for microphones - such as Sennheiser and Schoeps.  The mics that are marketed as digital have a minimal matching preamp or no preamp that exists between the capsule and the ADC and output an AES42 signal to a recorder - but the sound capture is all done in the analog domain with a mechanical membrane like it has been done since the dawn of microphones.

now the Question of 32 bit audio... the purpose of 32 bit audio wasn't really to improve sound quality per se... but to make it sound better in wider ranges of situations.  Back in the day when we had 16bit CDs, it was sort of acknowledged that 16 bit was more than enough for the average listener to hear "perfect" sound reproduction.  As technology progressed, some emerging formats tried to increase the bit depth in order to improve 16 bit "redbook" digital audio.  So for example, 20 bit HDCD allowed for greater than 16 bit reproduction, where the average person probably wouldn't really notice the difference, but for audiophiles who had good rooms and great equipment, and had a personality disorder to spend a lot of time A/B comparing their music over and over again, it was possible to detect a difference.  So for the average population, our ears' resolving power probably lies somewhere in the 14 to 18 bit range.  When recording studios moved away from tape and into digital recording formats, we didn't want a format that was equal to CD, wanted something with greater dynamic range so that raw sounds could be recorded, but then manipulated in post (much like recording in 12-15 stop log so that we can deliver a 7 stop consumer render)... so 24 bit was selected as the bit depth that would give more than enough audio quality.  The other problem is that electronics are not completely quiet, so even though a 24 bit file is recorded, maybe 18 to 20 bits of that is actually useful information.  Here is one area where AES42 digital mics help, by putting the ADC converter right at the capsule, it gives the mic the best possible outcome in signal to noise ratio.  It's certainly not 24 bits of resolution, but better than cabling to a preamp and adding noise from gain and subsequent interconnects and line stages.  So when we record 32 bit audio, we aren't departing into some new realm where we've invented a better way for audio engineers to hear, what it does allow us to do, though, is to unpack a wider dynamic range back into a 24bit workflow.  In the most simplistic terms, it allows the gain pot to be removed from the equation, so that instead of matching the gain to an appropriate level, the sound is simply recorded at a very low level and then when working in a 24 bit workflow, the signal can be digitally gained back up without dangerously pushing against the noise floor.  (technically not true, but close enough for illustration). Now theoretically, if a signal was recorded in plain old 16 bit audio, more or less the resolution of the ear, but at perfect levels, for all intents and purposes it is just as good as 32 bit audio.   Maybe not for the "air" around cymbal brushes or delicate nuance of the wood mallet hit on a bell, etc... but for good old human dialogue, which is a relatively low-fi sound source of limited dynamic range.  In other words in-camera audio can be just fine, even for critical professional work, but just don't mess up the gain levels (and use a professional camera with good audio circuits - talking about ENG style broadcast cameras, not DSLRs or prosumer cams).  When you hire a sound recordist on set, he's recording 24 bit audio.  So he can intentionally record at 10 to 20 dB lower than he knows the material will be final mixed at and still not have an issue with.  Now 10-20dB is a pretty huge range.  I can have someone whispering, peaking at -40dBfs and then have that person scream at the top of their lungs and unless a drill sergeant or opera singer, probably not going to clip.  More percussive things like gunfire can certainly clip, but quite frankly modestly clipped gunfire sounds just fine and there are post tools that can technically declip the audio.  Now you may get the feeling I'm about to poo poo 32 bit audio and your mostly correct.  What 32 bit audio does allow you tot do is have no idea what you are doing and not care enough to even check your modulation levels, as you can just hit record and as long as you are on board with the idea of the point of 32 bit audio and didn't crank the gain up, you'll be fine.

Now as far as this NUX company, I don't know them at all, know nothing about their product.  It could be great stuff.  My intuition is that it is crap and just happened to build their gear on a 32 bit platform.  I could be wrong, and its not appropriate for me to make guesses about how good it is or isn't.  My intuition is based on conceit and arrogance having the luxury of working with proven gear from Lectrosonics and Zaxcom on an average day.  We are talking about a lavaliere mic transmitter / receiver, which are quite frankly crappy mics when compared to big expensive condensers (shotguns and studio mics).  Rode does make a couple of good mics, NTG4+ is probably one of them.... haven't used one, but NTG3 was great other than durability.  Zoom F6 is actually a great recorder too, they have a history of making hissy prosumer stuff, like H4/H6, but F6 is solid.  As great as your stuff is, there's probably room for improvement, like maybe upgrading to a better mic or making sure you have good shockmounts, stands, holders, and extra cable for interviews to get the mic just right, wind protection and secret sauce accessories for handling finicky situations or wardrobe.  These are the things that I'd be looking at first over picking gear which most of us have never heard of and selecting based exclusively on the 32 bit concept somehow presuming it sounds best because of it.

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I received the NUX a couple of days ago and while it does work, first impressions are that it is better suited to dynamic microphones and not so much for condenser microphones. I haven't been able to do extensive tests at the moment and will do so soon.

Rode has stated that the VMP+ is a fully analogue microphone, but that the NTG is digital (this was another user asking questions). I'm not sure whether the Rode advice is referencing the USB output or whether they mean that the NTG has a built in ADC and DAC for the 3.5mm output. I would have bought the NTG4+, but the length of the mic makes it extremely long for a run and gun situation.

I know that 32 bit float is a bit of a cop out, but in my situation I simply don't have the ability to closely monitor the input, so every bit (no pun intended) will help. I just have to find out what works and what does not and accommodate any compromises that eventuate.

What I have found to be very enlightening, other than the fact that the F6 really does improve audio quality even with the Wireless GO units, is the fact that a mini-XLR to 3.5mm cable provides such a significant improvement with in-camera audio. The 3.5mm input must go through a somewhat different or perhaps hobbled pathway, given how much better the XLR input is by comparison.

 

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10 hours ago, Australian Image (Ray) said:

I received the NUX a couple of days ago and while it does work, first impressions are that it is better suited to dynamic microphones and not so much for condenser microphones. I haven't been able to do extensive tests at the moment and will do so soon.

That'll be because the NUX doesn't supply phantom power.

10 hours ago, Australian Image (Ray) said:

What I have found to be very enlightening, other than the fact that the F6 really does improve audio quality even with the Wireless GO units, is the fact that a mini-XLR to 3.5mm cable provides such a significant improvement with in-camera audio. The 3.5mm input must go through a somewhat different or perhaps hobbled pathway, given how much better the XLR input is by comparison.

If I've understood what you're saying, that's possibly because of variations in line level and mic level... and what levels are being used... for example, a lot of DSLRs/mirrorless cameras etc actually use "consumer line level", which is lower.... and thus may need more gain added to get back up to where you'd like it... and those potential for more noise. Then I guess it depends on the quality of the preamps/gain structure of the mixer/recorder.

 

@Tom Visser very good. But you forgot to discuss 1-bit ADC/DACs too 😉😉, hehe.

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Yes, the lack of phantom power with the NUX is a setback when it comes to microphone choice. Had it been able to provide phantom power, the choice of XLR mics would have been much improved.

The audio circuitry in the BMPCC4K is supposed to be much better than in typical DSLR/mirrorless cameras and I've read that the 3.5mm input was designed more for timecode than audio input, but it does both. That's why I pondered that perhaps it doesn't quite use the full capability of the audio circuitry that you get when you use the mini-XLR input.

The manual doesn't give much information about the two audio options, other than that the XLR input uses line level audio and the 3.5mm mic level audio.

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9 hours ago, Nezih said:

 

@Tom Visser very good. But you forgot to discuss 1-bit ADC/DACs too 😉😉, hehe.

oh boy, brings back bad memories from my days when I consulted for Mark Levinson who was a proponent for the Sony / DSD technologies.  Yes it sounded great, but way too esoteric for regular consumer use.  Layman's terms, a super high clock cycle that modulated a 1-bit signal, basically a differential to rise / fall, in the end emulating an analog sine wave.

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