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dynamic omni vs condenser for low noise.



 
 
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  #1  
Old December 30th 19, 10:58 PM posted to rec.audio.pro
Tobiah
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Posts: 636
Default dynamic omni vs condenser for low noise.

It would seem that a dynamic mic has no self-noise, is that so?
Yet to get the same gain as a condenser one has to crank the gain
up much more on the dynamic, raising the noise level. Is it ever
the case that when recording soft sounds, one could get a lower
noise recording with a dynamic? Would it take a very expensive
preamp to achieve this?

I would guess that the output level of the dynamic would be
key. Any recommendations for a high-output omni dynamic for
$100-200?
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  #2  
Old December 30th 19, 11:11 PM posted to rec.audio.pro
Don Pearce[_3_]
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Default dynamic omni vs condenser for low noise.

On Mon, 30 Dec 2019 13:58:32 -0800, Tobiah > wrote:

>It would seem that a dynamic mic has no self-noise, is that so?
>Yet to get the same gain as a condenser one has to crank the gain
>up much more on the dynamic, raising the noise level. Is it ever
>the case that when recording soft sounds, one could get a lower
>noise recording with a dynamic? Would it take a very expensive
>preamp to achieve this?
>
>I would guess that the output level of the dynamic would be
>key. Any recommendations for a high-output omni dynamic for
>$100-200?


A dynamic mic does have self-noise, generated by the same mechanism as
that of a condenser - thermal electron noise in the source resistance.
A dedicated low-noise pre-amp will just about match it, and may be an
advantage in low-noise scientific or really high quality Foley work.
For any normal recording, you shouldn't worry about it.

d
  #3  
Old December 30th 19, 11:33 PM posted to rec.audio.pro
Mike Rivers[_2_]
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Posts: 2,111
Default dynamic omni vs condenser for low noise.

On 12/30/2019 4:58 PM, Tobiah wrote:
> It would seem that a dynamic mic has no self-noise, is that so?


For small values of "no," yes. No microphone has no self-noise. A
dynamic mic doesn't have amplifier noise (tubes, semiconductors that
make hiss, hum, and buzz if not implemented well) but it has wire and
resistance, that that has noise.

> Yet to get the same gain as a condenser one has to crank the gain
> up much more on the dynamic, raising the noise level.


Microphones don't have gain, they have sensitivity, and, yes, the
sensitivity of a dynamic mic is typically lower than that of a condenser
mic. Therefore, to get the same recording level from a given source,
you'd need more preamp gain with a dynamic than a condenser, and the
noise that you're adding with that additional gain is electronic noise.
There's no free lunch, except almost, with a transformer, which is why
most dynamic mics have a transformer inside.

> Is it ever
> the case that when recording soft sounds, one could get a lower
> noise recording with a dynamic?* Would it take a very expensive
> preamp to achieve this?


I assume you're asking if you can get lower noise with a dynamic mic,
assuming you have a really quiet, high gain preamp, than you can with an
unknown condenser mic and preamp with unknown noise characteristics?
That's a "maybe." You're juggling a lot of variables here, and I think
you're only looking at electrical noise. The really quiet condenser mic
to which you're comparing a dynamic mic might be omnidirectional and
will pick up your neighbor's leaf blower better than the really high
output cardioid mic.

> I would guess that the output level of the dynamic would be
> key.* Any recommendations for a high-output omni dynamic for
> $100-200?


Yeah. The quietest condenser mic you can find in that price range. But
it might not be the best mic for your source.

You would get better answers if your this-or-that questions weren't so
abstract. Do you want to record crickets in your back yard at night? Do
you want to record a softly picked guitar or mountain dulcimer at a
distance of a foot or two from the mic? Do you want to record a bagpipe
band from as far away as you can get from them? You'd want a different
mic for each situation, and you might have to eliminate your best choice
if you get too much noise. Or you might just have to move the mic closer
to the source.


--
For a good time, call http://mikeriversaudio.wordpress.com
  #4  
Old December 31st 19, 12:54 AM posted to rec.audio.pro
Scott Dorsey
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Default dynamic omni vs condenser for low noise.

In article >, Tobiah > wrote:
>It would seem that a dynamic mic has no self-noise, is that so?


No, it has resistive noise just because of the resistance of the coil.

>Yet to get the same gain as a condenser one has to crank the gain
>up much more on the dynamic, raising the noise level.


In general true.

>Is it ever
>the case that when recording soft sounds, one could get a lower
>noise recording with a dynamic? Would it take a very expensive
>preamp to achieve this?


Given a particular dynamic and a particular condenser microphone, this
might be the case.

But, the quietest microphones you'll find are going to be condenser
microphones such as the Sennheiser MKH-20.

>I would guess that the output level of the dynamic would be
>key. Any recommendations for a high-output omni dynamic for
>$100-200?


All the good wideband omni dynamics are long gone because the market
for them is pretty small. You might like an RE-55, but they are fetching
far more on the used market than they ever cost new. Shure made some
similar dynamic omnis for the broadcast market that are equivalently
expensive.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #5  
Old December 31st 19, 01:39 AM posted to rec.audio.pro
Tobiah
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Posts: 636
Default dynamic omni vs condenser for low noise.

On 12/30/2019 2:33 PM, Mike Rivers wrote:
> On 12/30/2019 4:58 PM, Tobiah wrote:
>> It would seem that a dynamic mic has no self-noise, is that so?

>
> You would get better answers if your this-or-that questions weren't
> so abstract. Do you want to record crickets in your back yard at
> night? Do you want to record a softly picked guitar or mountain
> dulcimer at a distance of a foot or two from the mic? Do you want to
> record a bagpipe band from as far away as you can get from them?
> You'd want a different mic for each situation, and you might have to
> eliminate your best choice if you get too much noise. Or you might
> just have to move the mic closer to the source.



I record classical guitar into a pair of NT1-A's which go into a
Presonus 18/10 interface. I've never tried a high end preamp, but
these are the cleanest I've used. I can crank up a recording and
boost the treble and there is no noise to be found.

I want to experiment with an omni signal, perhaps to mix with the
dynamics, because I've never owned an omni mic. I've heard it could
make the room sound more open. I need the omni to give me a similar
level of noise with this setup.

I was wondering whether I could get away cheaper with a dynamic,
given that these preamps (they call them XMAX) seem to be very clean.
A condenser that does Omni with the noise specs I'm looking for seems
to put me into another price tier.

The other thing I want to do is record very soft sounds (like
rubbing fingers or palms together) into a palate that I can make
a collage with via a computer program and csound. Low noise and
transparency is the target.


Thanks




  #6  
Old December 31st 19, 08:44 PM posted to rec.audio.pro
Adrian Tuddenham[_2_]
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Posts: 503
Default dynamic omni vs condenser for low noise.

Tobiah > wrote:

> It would seem that a dynamic mic has no self-noise, is that so?
> Yet to get the same gain as a condenser one has to crank the gain
> up much more on the dynamic, raising the noise level. Is it ever
> the case that when recording soft sounds, one could get a lower
> noise recording with a dynamic? Would it take a very expensive
> preamp to achieve this?


There are two sources of noise in a moving coil microphone:

1) The resistance of the coil itself at room temperature generates
"Johnson Noise" due to movement of the electrons. Microphones with
stronger magnetic fields will have better sensitivity and will give a
better signal-to-thermal-noise ratio, so the sensitivity figures are
important when considering this type of noise.

2) The impact of the air molecules on the diaphragm (Brownian Motion)
will give shot noise. Each time the area of the diaphragm is doubled,
the wanted signal, which is in phase across the whole diaphragm, should
increase by 6dB, but the shot noise is not in phase across the
diaphragm, so it only increases by 3dB. For every doubling of the
diaphragm area there is theoretically an improvement of 3dB in the
signal to shot noise ratio. So a large diaphragm is important when
considering this type of noise.

In a well-designed microphone, these two sources of noise are
approximately equal; there is no point in spending a lot of design
effort decreasing one of them if the other one is going to predominate.

The noise of the pre-amp should be negligible when compared with these
two sources of microphone noise. Most modern pre-amps will achieve this
as long as they are correctly matched to extract the maximum power from
the microphone.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
  #7  
Old February 7th 20, 03:56 AM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 459
Default dynamic omni vs condenser for low noise.

Adrian Tuddenham wrote:

----------------------

>
> The noise of the pre-amp should be negligible when compared with these
> two sources of microphone noise. Most modern pre-amps will achieve this
> as long as they are correctly matched to extract the maximum power from
> the microphone.
>
>


** Fraid that last claim is plain wrong.

Attempting to "power match" a mic output to the pre-amp only makes the s/n ratio worse.

Nearly all mic makers recommend the load impedance be 10 times the mic's impedance for the specified performance including self noise.



..... Phil

  #8  
Old February 7th 20, 03:55 PM posted to rec.audio.pro
Ty Ford[_2_]
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Posts: 77
Default dynamic omni vs condenser for low noise.

On Thursday, February 6, 2020 at 9:56:05 PM UTC-5, Phil Allison wrote:
>
> ** Fraid that last claim is plain wrong.
>
> Attempting to "power match" a mic output to the pre-amp only makes the s/n ratio worse.
>
> Nearly all mic makers recommend the load impedance be 10 times the mic's impedance for the specified performance including self noise.
>
>
>
> .... Phil


right.

 




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