Reply
 
Thread Tools Display Modes
  #1   Report Post  
TJ Hertz
 
Posts: n/a
Default A question about dynamic and condenser microphones and maths

Hey. This might be a stupid question, but here goes.

A dynamic microphone's output, in voltage, is proportional to dx/dt (where x
is diaphragm displacement), right? And a condenser's output is proportional
to x, right?

So in theory (disregarding, for the moment, differences in capsules,
components, sensitivity, etc), if you differentiated the signal from a
condenser in terms of t, you'd get a dynamic-like signal, and if you
integrated the signal from a dynamic mic in terms of t, you'd get a
condenser-like signal, right?

In some applications, a condenser might sound better but a dynamic might be
more practical due to high SPL or the risk of damaging an expensive
condenser etc. Has anyone ever tried to design a plugin that could integrate
or differentiate a sound file's signal (numerically, obviously, not
analytically)? Maybe even in realtime?

Or am I just being stupid... and is this how mic/speaker simulators work?

I'd be interested to hear any thoughts.

--
tj hertz




  #2   Report Post  
Scott Dorsey
 
Posts: n/a
Default

TJ Hertz wrote:
Hey. This might be a stupid question, but here goes.

A dynamic microphone's output, in voltage, is proportional to dx/dt (where x
is diaphragm displacement), right? And a condenser's output is proportional
to x, right?

So in theory (disregarding, for the moment, differences in capsules,
components, sensitivity, etc), if you differentiated the signal from a
condenser in terms of t, you'd get a dynamic-like signal, and if you
integrated the signal from a dynamic mic in terms of t, you'd get a
condenser-like signal, right?


Yes.

In some applications, a condenser might sound better but a dynamic might be
more practical due to high SPL or the risk of damaging an expensive
condenser etc. Has anyone ever tried to design a plugin that could integrate
or differentiate a sound file's signal (numerically, obviously, not
analytically)? Maybe even in realtime?


That's more or less what a high-pass filter does.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #3   Report Post  
Arny Krueger
 
Posts: n/a
Default

"TJ Hertz" wrote in message
. uk
Hey. This might be a stupid question, but here goes.

A dynamic microphone's output, in voltage, is proportional

to
dx/dt (where x is diaphragm displacement), right? And a
condenser's output is proportional to x, right?

So in theory (disregarding, for the moment, differences in
capsules, components, sensitivity, etc), if you

differentiated
the signal from a condenser in terms of t, you'd get a
dynamic-like signal, and if you integrated the signal from

a
dynamic mic in terms of t, you'd get a condenser-like

signal,
right?


No.

If you differentiate a signal with some reference frequency
response characteristic, you'd get a signal with frequency
response that is rising at 6 dB/octave as compared to the
signal you differentiated.

But, in the real world both dynamic and condensor
microphones have nominally flat response.

IOW, there is *something* in a dynamic mic that causes a
level of integration that compensates for the
differentiation function you've noticed. I think that
*something* is the mass of the diaphragm and voice coil,
which is obviously far greater than the mass of the
fantastically thin diaphragms used with condensor mics.



  #4   Report Post  
Chris Hornbeck
 
Posts: n/a
Default

On Wed, 29 Jun 2005 16:48:14 GMT, "TJ Hertz"
wrote:

A dynamic microphone's output, in voltage, is proportional to dx/dt (where x
is diaphragm displacement), right? And a condenser's output is proportional
to x, right?

So in theory (disregarding, for the moment, differences in capsules,
components, sensitivity, etc), if you differentiated the signal from a
condenser in terms of t, you'd get a dynamic-like signal, and if you
integrated the signal from a dynamic mic in terms of t, you'd get a
condenser-like signal, right?


Cool, so next you want to be thinking about pressure response vs.
pressure-gradient response.

Two frequency-invariant models arise. Quiz on Friday!

Chris Hornbeck
"Chief Assistant to the Assistant Chief" -F&S
  #5   Report Post  
Adrian Tuddenham
 
Posts: n/a
Default

Arny Krueger wrote:

No.

If you differentiate a signal with some reference frequency
response characteristic, you'd get a signal with frequency
response that is rising at 6 dB/octave as compared to the
signal you differentiated.

But, in the real world both dynamic and condensor
microphones have nominally flat response.

IOW, there is *something* in a dynamic mic that causes a
level of integration that compensates for the
differentiation function you've noticed. I think that
*something* is the mass of the diaphragm and voice coil,
which is obviously far greater than the mass of the
fantastically thin diaphragms used with condensor mics.


Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.

The diaphragm of a condenser mic is much lighter and resonates on a mass
of entrapped air at a frequency well above audio. In the audio band it
is operating below resonance in compliance-controled mode, which is 90
degrees phase shifted from the resistance-controlled mode.

....That's where the compensating phase shift and consequent 6 dB/octave
slope comes from.


For a much more erudite description than that, try to get hold of a copy
of "Microphones" by A.E. Robertson. I believe it was published on both
sides of the 'pond'.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk


  #6   Report Post  
Bob Cain
 
Posts: n/a
Default



Adrian Tuddenham wrote:

Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.


Don't you mean mass-controlled?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
  #7   Report Post  
Phil Allison
 
Posts: n/a
Default


"Bob Cain"

Adrian Tuddenham wrote:

Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.


Don't you mean mass-controlled?




** Adrian 1.

Bob 0.



.......... Phil




  #8   Report Post  
Bob Cain
 
Posts: n/a
Default



Phil Allison wrote:
"Bob Cain"

Adrian Tuddenham wrote:


Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.


Don't you mean mass-controlled?





** Adrian 1.

Bob 0.


What is the "heavy-damping" mechanism that makes a dynamic
mic resistance controled and not sensitive to its mass?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
  #9   Report Post  
Phil Allison
 
Posts: n/a
Default


"Bob Cain"
Phil Allison wrote:

Adrian Tuddenham wrote:


Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.

Don't you mean mass-controlled?



** Adrian 1.

Bob 0.


What is the "heavy-damping" mechanism that makes a dynamic mic resistance
controled and not sensitive to its mass?



** Got news for you Bob - a mic is not electrically driven.




............. Phil


  #10   Report Post  
Adrian Tuddenham
 
Posts: n/a
Default

Bob Cain wrote:

Adrian Tuddenham wrote:

Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.


Don't you mean mass-controlled?


No, it also has a stiffish mounting, so the uncontrolled resonanace
would lie slap in the middle of the audio band - that's partly why they
were so popular, because the resonance made them sensitive and it could
be tuned and damped to cover the frequencies of interest.

The resistance control was by means of close-fitting air baffles (often
formed from the front of the magnet assembly) with restricted-flow air
vents. Modern moving coil mics also use all kinds of extra resonances,
damping and venting to flatten and extend the useful range. Of all the
mic types, they are the most difficult to get 'right' for high fidelity
because the technology is 'wrong' to start with - the manufacturers have
done a brilliant job to design them so well.

A mass-controlled mic, such as a ribbon, would have the resonance below
the frequency band of interest and there is a further 90 degrees of
phase shift.

(Before you say it, I know the mass of a ribbon is less than the
diaphragm and coil of a moving coil mic, but the suspension is *lot*
softer).

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk


  #11   Report Post  
Adrian Tuddenham
 
Posts: n/a
Default

Bob Cain wrote:

Adrian Tuddenham wrote:

Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.


Don't you mean mass-controlled?


Sorry to follow-up twice but:

I didn't explain properly, the 'resistance' is air resistance, not
electrical resistance.

Electrical damping can also make a difference but it is only loosely
coupled to the diapharagm and has far less effect. Some moving coil
mics do need particular terminating resistor values if they are to
perform exactly as specified.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
  #12   Report Post  
Bob Cain
 
Posts: n/a
Default



Phil Allison wrote:
"Bob Cain"

What is the "heavy-damping" mechanism that makes a dynamic mic resistance
controled and not sensitive to its mass?




** Got news for you Bob - a mic is not electrically driven.


And that is relevant to my question how?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
  #13   Report Post  
me
 
Posts: n/a
Default

Bob Cain wrote in
:

snip....snip

What is the "heavy-damping" mechanism that makes a dynamic
mic resistance controled and not sensitive to its mass?
Bob



If you got off your high horse and did a little reading, you might learn
something and eventually dispel your long-standing reputation as being
someone whose arrogance is only matched by his technical ignorance.

The answer to your question can be found on page 262 of Harry Olson's
classic text "Acoustical Engineering" which was first published in 1957.
If you don't have a copy, perhaps you should get one. If you do have a
copy, perhaps you should give it a read, as it clearly isn't doing you any
good by simply collecting dust on your bookshelf.



  #14   Report Post  
Chris Hornbeck
 
Posts: n/a
Default

On Thu, 30 Jun 2005 18:25:24 -0700, Bob Cain
wrote:

Adrian Tuddenham wrote:

Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.


Don't you mean mass-controlled?


Y'all are talking about two different critters. Adrian is describing
the compromises necessary in conventional (voice coil plus diaphragm)
dynamic mics, and Bob is talking about loosely suspended pressure-
differential mics like classic ribbons.

The former has a resonance in the pass band that must be dealt
with as well as possible; the latter must try to push the
resonance below the pass band.

Both are dynamic mics. Both are resistance controlled and both
are mass controlled, just varying in emphasis. But y'all know
all this.

Chris Hornbeck
"You been good to me, Baby,
Better than I been to myself"
-Isley, Isley, Isley
  #15   Report Post  
Adrian Tuddenham
 
Posts: n/a
Default

Chris Hornbeck wrote:

On Thu, 30 Jun 2005 18:25:24 -0700, Bob Cain
wrote:

Adrian Tuddenham wrote:

Or to put it another way, the (relatively massive) diaphragm + coil
system of a moving coil mic resonates, heavily damped, in the audio
band. It behaves as a resistance-controlled system.


Don't you mean mass-controlled?


Y'all are talking about two different critters. Adrian is describing
the compromises necessary in conventional (voice coil plus diaphragm)
dynamic mics, and Bob is talking about loosely suspended pressure-
differential mics like classic ribbons.

The former has a resonance in the pass band that must be dealt
with as well as possible; the latter must try to push the
resonance below the pass band.

Both are dynamic mics. Both are resistance controlled and both
are mass controlled, just varying in emphasis. But y'all know
all this.


I wasn't brought up on the American terminology "dynamic", but had
assumed it only referred to moving coil mics (and speakers).

So as to keep my answer on absolutely safe ground, I slightly changed
the wording and referred to the mic I was talking about as "moving coil"
- althought I wasn't aware that the term "dynamic" might have had such a
wide application as to include ribbon mics.

I suppose, in a way, nearly all mics are 'dynamic' because something in
them has to move. Is it possible, without starting another flame war,
to ask what the American terminology is for *only* a moving coil mic -
and how broadly the term 'dynamic' can be used ?

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk


  #17   Report Post  
Chris Cavell
 
Posts: n/a
Default

Here's a little but info-packed booklet from Neumann that contains most
mic types and nearly all the physics equations necessary to describe
their operation:

https://www.neumann.com/infopool/dow...i=docu0002.PDF

TJ, it sounds like what you're concentrating on is the dependence on
output of veleocity vs. position/displacement of the mic element. This
property of a microphone depends on several factors, and often one
predominates the other at certain areas of the frequency response
depending upon the mic design. Iirc, this booklet goes into that a
little bit.

Cheers,
Chris

  #18   Report Post  
Adrian Tuddenham
 
Posts: n/a
Default

Chris Cavell wrote:

https://www.neumann.com/infopool/dow...i=docu0002.PDF


That's a very useful reference - thanks.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
  #19   Report Post  
Chris Cavell
 
Posts: n/a
Default

You're welcome.

Adrian Tuddenham wrote:
Chris Cavell wrote:

https://www.neumann.com/infopool/dow...i=docu0002.PDF


That's a very useful reference - thanks.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk


  #20   Report Post  
Bob Cain
 
Posts: n/a
Default



Chris Cavell wrote:
Here's a little but info-packed booklet from Neumann that contains most
mic types and nearly all the physics equations necessary to describe
their operation:

https://www.neumann.com/infopool/dow...i=docu0002.PDF


Thanks, Chris. From page 26:

"Dynamic directional microphones, which respond to pressure
gradients or particle velocity and therefore are subject to
increasing forces as frequency rises (as shown in Fig. 3),
must be operated at the top of the downslope of their
resonance curve in order to yield a flat frequency response,
i.e. above their mechanical resonance frequency. This means
that they must be “low-tuned” and predominantly
mass-controlled in operation."

It was from memory of this principle that I questioned
"resistance-controlled" being an appropriate description of
a dynamic's operation. The quote and the figure 3 applies
to the gradient type which is by far the predominant dynamic
design and thus the default when I think about them.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
Reply
Thread Tools
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Budget Condenser Microphones dazz Pro Audio 76 August 21st 05 01:30 PM
Some Recording Techniques kevindoylemusic Pro Audio 19 February 16th 05 08:54 PM
question regarding beyer dynamic condenser mic mc740 [email protected] Pro Audio 29 January 15th 05 10:55 PM
What's in your mic cabinet? Bob Cain Pro Audio 49 April 11th 04 08:31 AM


All times are GMT +1. The time now is 04:57 PM.

Powered by: vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AudioBanter.com.
The comments are property of their posters.
 

About Us

"It's about Audio and hi-fi"