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Comparing dynamic and small diaphragm microphones for dialog


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Hello,

 

I am learning location sound recording, practising as an enthusiast. I first try to use what I already have, and if necessary, I may invest a bit. These days, I focus on recording dialog. I would like to check whether buying an Audix SCX-1 / AT4053b / MK012 would improve the quality.

 

I have a Beyer M88-TG, hypercardioïd, 2,9mV/Pa. I recorded my voice 40cm away from the mouth (acceptable for a close-up). The recorder is a USB soundcard, a Behringer UMC204HD. Although being an entry level device, pres are rather clean, EIN supposed to be -129dBu.

 

I measured “signal to noise ratio” my own way (not really scientific):  LUFS of spoken words / LUFS of silent parts. Of course, there is room tone in these silent parts. With the preamp gain at its maximum (56dB), I get 40dB difference between the average level of my voice and the noise. To my ears, this is acceptable.

 

The level of my voice at the mic position is 59dBA. I tried to figure out what I could get from an small condenser microphone. I am not sure of my calculation.

Let’s assume I have an SCX-1, 14dBA self noise. Ignoring the preamplifier noise, this means that the best signal to noise ratio I would get is 59-14 = 45dBA. Is that correct ?

With a MK012, 18dBA self noise, this would give 59-18 = 41dBA S/N, Correct ?

At best, the SCX-1 would provide an improvement of 5dB over my M88. It would indeed not be that much due to preamplifier noise, plus the fact that current “noise” contains an unknown amount of room tone. The MK012 would probably bring no improvement at all, or even worse than the M88.

 

Now, I tried to estimate the M88 self noise. This is a dynamic microphone. Lets’ assume the noise is the one of a 150 ohm resistor, so -130dBu, as proposed by an article on Neumann’s website:
https://www.neumann.com/homestudio/en/will-a-better-preamp-give-you-lower-noise

-130dBu = 0,245µV
M88 sensitivity is 2,9mV/Pa. Sound pressure equivalent to noise : 0,245E-6 / 2,9E-3 = 84,5µPa
Equivalent SPL: 20*log(84,5E-6 / 2E-5 ) = 12,5dB

 

12,5dB is extremely low. I guess A-weighting would even lower it. Is that calculation correct ? Does this mean that, due to its high sensitivity (for a dynamic microphone), the Beyer M88 competes with the best small diaphragm condensers as long as I use a clean preamplifier ?  

 

Or... is my calculation complete BS ?

 

By the way, I also made tests with an AT4033, 17dBA self noise, 25mV/Pa, and the results were really close to the M88: about 40dB difference between voice average level and noise. This again suggests there is not much improvement to be expected buying a decent condenser, at least with rthe ambient noise (measured at 34dBA)

 

Please note I just focused on noise here. I know the M88 is highly sensitive to vibrations, wind, and weight a lot if boomed. Good reasons to use something else.

 

Thank you for reading.

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If you want to get good at location sound, focus on sound perspective, mic placement (including booming and lav mounting), room treatment etc rather then a few db noise difference. 

those will be much more useful skills then comparing technical data sheets.

 

as for mic choice, these are dozens of topics with great advise here. Personally I‘d say get something cheap to learn if you are broke, but get a nice mic as soon as you can (used if necessary)

 

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Yes, you focus way too much on the numbers, but they are largely irrelevant. Learn to listen to the mics and find out for yourself which mic you like. If you want you can then look at the numbers and try to find out from them what it is you like. 
Take the Schoeps CMk641, for example. It’s not the mic with the lowest self-noise or the greatest specs, but still it’s a hugely popular and well regarded mic

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I read these topics about cheap mics, and this is why I focused on the usual suspects: Oktava/Audix/AT. I did not expect that figures would tell about the whole quality, nor would they help about mic placement. However, I think figures help understanding where a problem may come from. It could even tell that I am expecting too much from a mike on a boom in that situation, and I should switch to lavs for example.

 

I would rather know before spending $500 whether a SCX-1 would help in terms of S/N ratio. It seems not much. Since I liked the sound of the M88 during my tests, I suppose I should stick with it for beginning. In my case, figures suggest those $500 would be best spent in a lavalier (which I do not have). I find this useful.

 

Other than that, I bought a Rycote INV-7 HG mkIII shock mount, as advised on this forum. I received it today, and performed not-truly-scientific-tests of "handling noise" (again, measuring the LUFS level) . Here are my results:

- basic mic clamp as reference

- Beyer EA19/25 shock mount: 3dB reduction of the rumble

- Rycote INV-7 HG: 11dB reduction.

 

Sounds like a good investment (and audible).

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Once you get half decent pres and microphones, the SN is less of an issue for dialogue.

 

I feel my Sanken CS3e is a bit noisy sometimes (in terms of selfnoise), but the characteristics make up for it in a noisy environment.

 

If you lust low selfnoise for dialogue recording, it's mainly the Sennys that push that among the popular dialogue mics. That said, I like my Audix SCX1HCs better than Sennheiser 8050s on most voices, selfnoise is just one thing of many to consider. 

 

We also planted an oktava close to a Schoeps CMC1 MK41 on a recent gig. The selfnoise was not the big factor here when listening back to the files, but offaxis was more forgiving and it sounded more immersive and "real" with the Schoeps.

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There is a quick and simple advice:

 

Microphone closer to the mouth means: Less gain & better S/N.

 

The case in production sound, isn't about self-noise of microphone or mic preamp always; but collaboration with other other departments.

 

Numbers - specs from any output (microphone) or input (mic preamp) means nothing when you deal with a noisy location; and there you need a "friend of sound" (I miss you Jan).

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Maybe I should have given the context, because you cannot guess. I have worked over ten years as live sound engineer, for hundreds shows with hundreds bands. Noise is not a topic in live sound. A Shure Beta98 has over 30dB self noise. When miking the 130dB of a saxophone a few centimetres away, it still provides 100dB S/N ratio. If I set the preamp gain over 36dB, I wonder where’s the problem.

 

What I am doing here is “calibrating my expectations and habits”. I did the calculation in the first post to check whether 40dB between voice and noise is acceptable or if I am completely missing something. But I am not sure it is correct.

 

Videographers sometime come into the venues I work in to shoot the performance. Almost every, single, time, one member of the video crew is a “friend who helps”. The guy loses 5 minutes searching where to set the frame rate in the menu. Man! The “director” should have invited you to a local bar before. You should have already set-up all you could before entering the house.

 

When I will be on location, with the other crew members being enthusiast as well, I will not be discovering everything. I will know that pushing the gain at its maximum is nothing strange. I will have a boom pole, a mic that does the trick, an efficient shock mount. Staying at home does not teach diplomacy toward the other crew members. I will not become experienced that way. I will only be less a complete beginner. That is all I am after right now with the lock down.

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I think I get where you're coming from Nico. I also came from the music (studio) world and know the M88 (great on guitar cabs) very well. I think what people have mentioned here is super helpful. I understand that you're very experienced with doing live sound for bands. The way we mic these kind of concerts are very different from film/tv/video. For example, yes, the venues are crowded with fans and they are very loud BUT the lead singers mouth is practically on the capsule most of the time. This helps with the S/N ratio. In this kind of work, we might have a noisy location (street, sidewalk, etc) and we can't get the mic capsule in front of the source like you would on a guitar cab, snare, or kick drum. The S/N ratio gets worse when actors whisper. This creates challenges when capturing dialogue. Getting close to the source is the main challenge in audio for picture. Specially nowadays with so many cameras playing wide, tight, and tighter.

All this being said, in my experience, dynamic microphones react differently to different mic amps and the sound will change--dramatically-- depending on the mic and mic amp combination. I feel like tube mics and condenser mics are a bit less prone to this. Of course there will be a difference but it won't be as pronounced. Just my 2 cents.

 

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well, I still don't get the point of the "noise calculations" above...

 

borrow some mics, try them with your typical environment and gear, then see what you like.

will take you a few hours and cost like 50 bucks, but tell you 10 times more then reading data sheets and running calculations for days.

 

as for which mics to try, as mentioned there are quite a few of good topics already.

 

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