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Mic spec & input gain noise relation
Old 4 weeks ago
  #1
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Mic spec & input gain noise relation

Hi,

I have purchased LOM Usi PRO long time ago. They use Primo EM272 condenser omnies.

Later on, I have purchased Audio Technical AT4021 cardidoid.

I wonder why AT4021 has got less noise with HIGH input gain than Primo EM272.

Mic spec:

AT4021
Sensitivity -34dB
Output impedance 250 Ohm

EM272
Sensitivity -28dB
Output impedance 2.4 kOhm

AT4021 has about same noise with HIGH +76dB compared to EM272 at MID gain.

Is it due mic pattern omni vs cardiodoid (AT4021) or Output impedance or sensitivity?

Or perhaps AT4021 has own electronic circuits built-in and EM272 is directly connected to preamp?

I have purchased also AT4022 and will do comparison.

Could someone explain me relationship of mic spec vs noise, please?

I do nature audio recording and wonder how to compare microphones before purchase. I always check self-noise, best sensitivity and seek lowest impedance.

Sennheiser MKH-20 is similar to AT4022 but with lower output impedance. Does that mean Sennheiser has got stronger signal than AT4022, please?

Regards

Hajes
Old 4 weeks ago
  #2
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avare's Avatar
 

the AT4021 has 6 dB less gain
Old 4 weeks ago
  #3
Gear Addict
 

I'm not a mic designer but I would imagine that the very small EM272 capsule would be responsible for the mic mic not having the best signal to noise ratio and as well it's fairly low cost.

The EM272 is the cap in the Crown GLX 100 mics are xlr and are great little mics for putting in a guitar or a fiddle but still probably not the best for nature recording.

Are you recording places or specific things like bird song? Omni mics are good for a flat uncolored sound but shotgun mics are the usual for grabbing sound from a particular point source.

The best nature mics like any other "best" mic are expensive.

The AT4022 is a electret mic but not a tiny mini like the LOM and at more than twice the cost of the LOM I'm not surprised it's a better performer.
It's a good mic but really high quality can run a whole lot more.
Old 4 weeks ago
  #4
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Quote:
Originally Posted by avare View Post
the AT4021 has 6 dB less gain
isn't it the other way around. if i understood correctly the lower minus dB it means higher sensitivity
Old 4 weeks ago
  #5
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Quote:
Originally Posted by sn1p3r29a View Post
isn't it the other way around. if i understood correctly the lower minus dB it means higher sensitivity
There is your problem.
Old 4 weeks ago
  #6
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Quote:
Originally Posted by JLast View Post
I'm not a mic designer but I would imagine that the very small EM272 capsule would be responsible for the mic mic not having the best signal to noise ratio and as well it's fairly low cost.

The EM272 is the cap in the Crown GLX 100 mics are xlr and are great little mics for putting in a guitar or a fiddle but still probably not the best for nature recording.

Are you recording places or specific things like bird song? Omni mics are good for a flat uncolored sound but shotgun mics are the usual for grabbing sound from a particular point source.

The best nature mics like any other "best" mic are expensive.

The AT4022 is a electret mic but not a tiny mini like the LOM and at more than twice the cost of the LOM I'm not surprised it's a better performer.
It's a good mic but really high quality can run a whole lot more.
I started to use omnies with various direction damping/reflection/reduction because I do not like directional mics. The labyrinth design or whatever they use in designs distorts natural sound.

For example waterfall's pressure waves make funny noise in shotguns.

Cardidoids have similar problems...I have tried some water stream/waves recording and it made weird distorted noises .

Omni with cork damper sounds more natural to me
Old 4 weeks ago
  #7
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Quote:
Originally Posted by avare View Post
There is your problem.
so less sensitivity + higher gain = less noise?
Old 4 weeks ago
  #8
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Quote:
Originally Posted by sn1p3r29a View Post
so less sensitivity + higher gain = less noise?
It depends.
Old 4 weeks ago
  #9
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Quote:
Originally Posted by sn1p3r29a View Post
so less sensitivity + higher gain = less noise?
Less sensitivity (6dB or so apparently) at a given sound pressure level = needing 6dB more gain ...for the same output and record level.
I'm wondering if you might also be including acoustical noise being picked up? Or how about comparisons with the gains having only that 6dB difference dialed in?

I would think set side by side in a quiet place, add a constant noise source (well above the room noise. Dial in both for the same record level. Turn off the noise, record. 'Bury/cover both mics enough so they can't hear' the room noise, record again.
Now you can in -digital gain- bring each up equally as loud as needed to compare room noise+mic noise, and just the mic's noise.
Old 4 weeks ago
  #10
Gear Nut
Quote:
Originally Posted by sn1p3r29a View Post
Hi,

I have purchased LOM Usi PRO long time ago. They use Primo EM272 condenser omnies.

Later on, I have purchased Audio Technical AT4021 cardidoid.

I wonder why AT4021 has got less noise with HIGH input gain than Primo EM272.

Mic spec:

AT4021
Sensitivity -34dB
Output impedance 250 Ohm

EM272
Sensitivity -28dB
Output impedance 2.4 kOhm

AT4021 has about same noise with HIGH +76dB compared to EM272 at MID gain.

Is it due mic pattern omni vs cardiodoid (AT4021) or Output impedance or sensitivity?

Or perhaps AT4021 has own electronic circuits built-in and EM272 is directly connected to preamp?

I have purchased also AT4022 and will do comparison.

Could someone explain me relationship of mic spec vs noise, please?

I do nature audio recording and wonder how to compare microphones before purchase. I always check self-noise, best sensitivity and seek lowest impedance.

Sennheiser MKH-20 is similar to AT4022 but with lower output impedance. Does that mean Sennheiser has got stronger signal than AT4022, please?

Regards

Hajes
I don’t know the specifics on these two mics and there may be a variety of factors at play, the output impedance certainly impacts Johnson noise and that is close to a factor of 10 X between these microphones in this instance that you describe.

Do you have data sheets with any more detail available?

Cheers!
Old 4 weeks ago
  #11
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Quote:
Originally Posted by fried fingers View Post
I don’t know the specifics on these two mics and there may be a variety of factors at play, the output impedance certainly impacts Johnson noise and that is close to a factor of 10 X between these microphones in this instance that you describe.

Do you have data sheets with any more detail available?

Cheers!
https://www.primo.com.sg/em272

https://www.audio-technica.com/cms/w...acc/index.html
Old 3 weeks ago
  #12
Gear Nut
Thanks - just some thoughts - nothing truly definitive but you can analyze these types of things all day. I would just use the one you like better. Please keep in mind when you mention noise that there is noise inherently in the device as well as the rest of the recording chain and then noise that is present in the environment.

It appears both are electret condensers and these generally are slightly noisier than comparable true condensers in my experience. The AT microphone lists 14 dBA as the noise specification, this is actually reasonably good for an electret condenser. It additionally lists S/N ratio of 80 dBA @ 1 kHz which is what you would derive based on the 1 Pa = 94 dB sound pressure level testing standard.

The Primo microphone also lists a S/N ration of 80 dBA @ 1 kHz which implies a noise specification of 14 dBA as well.

Very similar written noise specifications so why the difference?

1. The Primo indicates a circuit network attached to the microphone i.e. most likely a recommendation and what was used to test the microphone - I suspect if this was different, the noise performance may be impacted.

2. A weighting is intended to take into account some level of human audibility and therefore a degree of variability exists in products with the same A weighted noise level. For example the actual noise level in a given frequency on the Primo microphone may be higher and more objectionable than on the AT microphone. After the A weighting curve is applied it is possible that the noise level in the frequency band in question has been lowered below other frequency bands. Also note the specification lists 1 kHz for S/N. This is valid at one frequency, other audible frequencies could certainly deviate from that specification. It is also only valid at 94 dB spl. This could change with higher or lower spl.

3. Higher sensitivity of the Primo microphone would indicate that it will pick up more ambient noise than the AT microphone with a similar gain. This may also be exacerbated by the fact that it is an omnidirectional microphone while the AT microphone is cardioid.

4. The Primo is actually the condenser element - how is it mounted? Is the isolation similar to the AT microphone? The actual microphone performance is going to depend to some extent on how well the final "complete microphone" using it was executed.

5. Lack of standardization on microphone testing, some manufacturers are more conservative in their technical specifications and some also seek to provide these details as accurately as possible. Others it seems as an afterthought at best.

I use the specifications as guidelines only and rely more on my own experience as well as others. Ultimately you have to use the microphone to know how it will perform in your application. I am familiar with AT as they are a mainstream supplier of microphones and their specifications are usually accurate, I had never heard of Primo, so can't provide guidance in that case.

Good luck!
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