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  #1   Report Post  
Bob Cain
 
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Scott Dorsey wrote:


The notion is that by using gated impulse testing, you can get a response
which is equivalent to the response that you'd get from a swept test in
an anechoic chamber. The gated impulse effectively eliminates room
reflections from the testing, and therefore is "anechoic" meaning without
echoes.


This can only be made to work with a driving point that
itself can deliver very short impulses. A typical speaker
isn't done radiating by the time reflections start arriving.
But that can be compensated by measurement of the speaker
first in really anechoic or hemi-anechoic conditions,
inverting its impulse response and from that point on
convolving all stimuli sent through the speaker with that
inverse first. The speaker is idealized in the process.

This won't work too well as a way to compensate speakers for
monitoring because of latency issues involved in convolution
but for measurement it works well.


Bob
--

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

A. Einstein
  #2   Report Post  
Bob Cain
 
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Default Mic Frequency Response



Scott Dorsey wrote:

A perfect impulse has an infinite width,
which is a problem to get in the real world.


Make that infinitessimal rather than infinite.


Bob
--

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

A. Einstein
  #3   Report Post  
Bob Cain
 
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Chris Hornbeck wrote:


So Bob's concern with fatter sparks is with getting a longer
*time* of arc? Rather than amplitude?


No, the discharge is still very quick even if long. What
the length gives is LF energy. A spark is not an impulse
exactly and the longer it is the closer it gets to one. A
short spark is a high passed impulse.

The spark is a heating phenomenon where a local region of
air expands due to heat and there is a relationship between
the amount of energy dissipated and the spectral content.

An exploding wire is different in that a highly condensed
material, a metal, is instantly turned into a gas of _much_
greater volume. The energy dissipated in the process is
also much higher, kilojoules. You can project potatoes very
long distances with one. :-)

The only real advantage of impulsive sources over swept sin
approaches is the typically omnidirectional nature of the
pressure field if that is desired. In all other regards the
swept sin is superior.


Bob
--

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

A. Einstein
  #4   Report Post  
Chris Hornbeck
 
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On Thu, 06 May 2004 00:25:11 -0700, Bob Cain
wrote:

So Bob's concern with fatter sparks is with getting a longer
*time* of arc? Rather than amplitude?


No, the discharge is still very quick even if long. What
the length gives is LF energy. A spark is not an impulse
exactly and the longer it is the closer it gets to one. A
short spark is a high passed impulse.


So, for better low frequency energy output, the spark needs
to last longer in time. The spark itself will still provide
the sharp leading and trailing edges. OK so far?

The spark is a heating phenomenon where a local region of
air expands due to heat and there is a relationship between
the amount of energy dissipated and the spectral content.


And the spectral content is determined by how long (in time)
that the arc occurs? And acoustic amplitude is related in some
way to the physical size of the gap?

Thanks, as always,

Chris Hornbeck
  #5   Report Post  
Aaron J. Grier
 
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Bob Cain wrote:
The only real advantage of impulsive sources over swept sin approaches
is the typically omnidirectional nature of the pressure field if that
is desired. In all other regards the swept sin is superior.


if I'm not mistaken, with a bit of math you can convert an impulse
response to a frequency response and vice versa, with the practical
limitations of spark size limiting the low-frequency response
measurement.

swept sines seem like an anachronism when you have fourier at your
disposal; what am I missing?

--
Aaron J. Grier | "Not your ordinary poofy goof." |
"someday the industry will have throbbing frontal lobes and will be able
to write provably correct software. also, I want a pony." -- Zach Brown


  #6   Report Post  
Bob Cain
 
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Aaron J. Grier wrote:
Bob Cain wrote:

The only real advantage of impulsive sources over swept sin approaches
is the typically omnidirectional nature of the pressure field if that
is desired. In all other regards the swept sin is superior.



if I'm not mistaken, with a bit of math you can convert an impulse
response to a frequency response and vice versa, with the practical
limitations of spark size limiting the low-frequency response
measurement.

swept sines seem like an anachronism when you have fourier at your
disposal; what am I missing?


That you can do the same thing exactly with a swept sin.
You just calculate the cross correlation of the response
with a slight variation of the stimulus (using Fourier
magic) and, voila, out pops the impulse response!

The advantage of swept sin over impulse methods is noise
immunity. You have much more energy in the response from
which to calculate the IR than you do in a real impulse.
It's advantage over pseudo random noise sequences is that
spectral components due to non-linear distortion are
separable using the swept sin.


Bob
--

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

A. Einstein
  #7   Report Post  
Peter Larsen
 
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OldBluesman wrote:

If an inexpensive mic has the same frequency response
and frequence response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?


Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.

OldBluesman



Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
  #8   Report Post  
Peter Larsen
 
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OldBluesman wrote:

If an inexpensive mic has the same frequency response
and frequence response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?


Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.

OldBluesman



Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
  #9   Report Post  
Arny Krueger
 
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Peter Larsen wrote:
OldBluesman wrote:

If an inexpensive mic has the same frequency response
and frequency response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?


Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Same primary reason - their response curves exist in 3 dimensions.

I heard an AES presentation by Earl Geddes about what it takes to truly
record and store the full frequency response curves of a mic or speaker with
sufficient resolution. 'Tain't trivial even using modern computer hardware,
though he says he has a patent-pending solution...


  #10   Report Post  
Arny Krueger
 
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Peter Larsen wrote:
OldBluesman wrote:

If an inexpensive mic has the same frequency response
and frequency response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?


Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Same primary reason - their response curves exist in 3 dimensions.

I heard an AES presentation by Earl Geddes about what it takes to truly
record and store the full frequency response curves of a mic or speaker with
sufficient resolution. 'Tain't trivial even using modern computer hardware,
though he says he has a patent-pending solution...




  #11   Report Post  
David Bock
 
Posts: n/a
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" Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.
OldBluesman

Kind regards
Peter Larsen"


Not true, you just need to see enough different kinds of measurements
and learn how to read them. Expect to see more info on this in the
coming years as major mic mfg's work w/the AES to create more useable
standards to address your very comment.
regards,
David Bock
Soundelux Microphones
  #12   Report Post  
David Bock
 
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" Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.
OldBluesman

Kind regards
Peter Larsen"


Not true, you just need to see enough different kinds of measurements
and learn how to read them. Expect to see more info on this in the
coming years as major mic mfg's work w/the AES to create more useable
standards to address your very comment.
regards,
David Bock
Soundelux Microphones
  #13   Report Post  
Bob Cain
 
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Peter Larsen wrote:

OldBluesman wrote:


If an inexpensive mic has the same frequency response
and frequence response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?



Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


Bob
--

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

A. Einstein
  #14   Report Post  
Bob Cain
 
Posts: n/a
Default



Peter Larsen wrote:

OldBluesman wrote:


If an inexpensive mic has the same frequency response
and frequence response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?



Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


Bob
--

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

A. Einstein
  #15   Report Post  
Arny Krueger
 
Posts: n/a
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Bob Cain wrote:
Peter Larsen wrote:

OldBluesman wrote:


If an inexpensive mic has the same frequency response
and frequence response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?



Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


Since we've covered linear distortion, that leaves nonlinear distortion and
noise.

Noise as currently specified is not as revealing as it could, because mic
have different noise spectra.

In general, it seems like mics have relatively low nonlinear distortion as a
rule, at least until the diaphragm bottoms, the transformer saturates, or
the electronics clip.




  #16   Report Post  
Arny Krueger
 
Posts: n/a
Default

Bob Cain wrote:
Peter Larsen wrote:

OldBluesman wrote:


If an inexpensive mic has the same frequency response
and frequence response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?



Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


Since we've covered linear distortion, that leaves nonlinear distortion and
noise.

Noise as currently specified is not as revealing as it could, because mic
have different noise spectra.

In general, it seems like mics have relatively low nonlinear distortion as a
rule, at least until the diaphragm bottoms, the transformer saturates, or
the electronics clip.


  #17   Report Post  
Paul Stamler
 
Posts: n/a
Default

"Bob Cain" wrote in message
...
Peter Larsen wrote:

OldBluesman wrote:


If an inexpensive mic has the same frequency response
and frequence response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?


Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


Distortion. Phase response. Hysteresis.

Peace,
Paul


  #18   Report Post  
Paul Stamler
 
Posts: n/a
Default

"Bob Cain" wrote in message
...
Peter Larsen wrote:

OldBluesman wrote:


If an inexpensive mic has the same frequency response
and frequence response curve as an expensive mic, what
is the advantage of purchasing the expensive
mic?


Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


Distortion. Phase response. Hysteresis.

Peace,
Paul


  #19   Report Post  
 
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"Then what other physical phenomenon accounts for the sound?

stortion. Phase response. Hysteresis."

3 of the above is an example of 1 and 2 would be seen as freq responce.
The biggest differences are noise and pickup pattern if the mic is not
overdriven. Two omins with the same freq responce and other things being
equal will sound the same, for example.
  #20   Report Post  
 
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"Then what other physical phenomenon accounts for the sound?

stortion. Phase response. Hysteresis."

3 of the above is an example of 1 and 2 would be seen as freq responce.
The biggest differences are noise and pickup pattern if the mic is not
overdriven. Two omins with the same freq responce and other things being
equal will sound the same, for example.


  #21   Report Post  
 
Posts: n/a
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"Then what other physical phenomenon accounts for the sound?

stortion. Phase response. Hysteresis."

3 of the above is an example of 1 and 2 would be seen as freq responce.
The biggest differences are noise and pickup pattern if the mic is not
overdriven. Two omins with the same freq responce and other things being
equal will sound the same, for example.
  #22   Report Post  
Bob Cain
 
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Arny Krueger wrote:


Since we've covered linear distortion, that leaves nonlinear distortion and
noise.


Yep.


Noise as currently specified is not as revealing as it could, because mic
have different noise spectra.


And don't, in general, color the sound of the mic. It's
additive and at low levels.


In general, it seems like mics have relatively low nonlinear distortion as a
rule, at least until the diaphragm bottoms, the transformer saturates, or
the electronics clip.


Yes, condensers are much lower than any speaker you might
listen on. Since it seems that every factor which could
affect the sound of a mic has been ruled out, I guess were
down to magic. Often happens with mics. Too often.

Oh, by frequency response I presume both magnitude and phase
were implied.


Bob
--

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

A. Einstein
  #23   Report Post  
Bob Cain
 
Posts: n/a
Default



Arny Krueger wrote:


Since we've covered linear distortion, that leaves nonlinear distortion and
noise.


Yep.


Noise as currently specified is not as revealing as it could, because mic
have different noise spectra.


And don't, in general, color the sound of the mic. It's
additive and at low levels.


In general, it seems like mics have relatively low nonlinear distortion as a
rule, at least until the diaphragm bottoms, the transformer saturates, or
the electronics clip.


Yes, condensers are much lower than any speaker you might
listen on. Since it seems that every factor which could
affect the sound of a mic has been ruled out, I guess were
down to magic. Often happens with mics. Too often.

Oh, by frequency response I presume both magnitude and phase
were implied.


Bob
--

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

A. Einstein
  #24   Report Post  
Bob Cain
 
Posts: n/a
Default



Arny Krueger wrote:


Since we've covered linear distortion, that leaves nonlinear distortion and
noise.


Yep.


Noise as currently specified is not as revealing as it could, because mic
have different noise spectra.


And don't, in general, color the sound of the mic. It's
additive and at low levels.


In general, it seems like mics have relatively low nonlinear distortion as a
rule, at least until the diaphragm bottoms, the transformer saturates, or
the electronics clip.


Yes, condensers are much lower than any speaker you might
listen on. Since it seems that every factor which could
affect the sound of a mic has been ruled out, I guess were
down to magic. Often happens with mics. Too often.

Oh, by frequency response I presume both magnitude and phase
were implied.


Bob
--

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

A. Einstein
  #25   Report Post  
Mike Rivers
 
Posts: n/a
Default


In article writes:

Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


It's really all about frequency response, no any single frequency
response curve accurately characterizes the sound of a microphone,
other than perhaps a true omni mic (and there are darn few of those).

Since the frequency response curve changes (significantly) depending
on the direction from which the sound is coming when it reaches the
microphone, and since few things that we'd actually want to record
produce sound that goes in a straight line (only), you have to take
into account the fact that the frequency response for that particular
recording isn't going to look like the published curve. It (like a
speaker measured in natural habitat) will probably look pretty rough,
and you'd say "I'd never use a microphone with frequency response like
that." But you do. Microphones, like any transducers, are always imperfect.

Generally, when frequency response varies in a smooth and predictable
manner as you go off axis, a microphone will be considered "less
colored" which means the frequency response is more even. On the other
hand, if you like the frequency response curve 30 degrees off axis,
you can get that sound by pointing the mic so that an imaginary line
30 degrees from straight-on is pointing to the source. But then you've
gotta watch those reflections.

And then there's transient response.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo


  #26   Report Post  
Mike Rivers
 
Posts: n/a
Default


In article writes:

Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


It's really all about frequency response, no any single frequency
response curve accurately characterizes the sound of a microphone,
other than perhaps a true omni mic (and there are darn few of those).

Since the frequency response curve changes (significantly) depending
on the direction from which the sound is coming when it reaches the
microphone, and since few things that we'd actually want to record
produce sound that goes in a straight line (only), you have to take
into account the fact that the frequency response for that particular
recording isn't going to look like the published curve. It (like a
speaker measured in natural habitat) will probably look pretty rough,
and you'd say "I'd never use a microphone with frequency response like
that." But you do. Microphones, like any transducers, are always imperfect.

Generally, when frequency response varies in a smooth and predictable
manner as you go off axis, a microphone will be considered "less
colored" which means the frequency response is more even. On the other
hand, if you like the frequency response curve 30 degrees off axis,
you can get that sound by pointing the mic so that an imaginary line
30 degrees from straight-on is pointing to the source. But then you've
gotta watch those reflections.

And then there's transient response.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo
  #27   Report Post  
Mike Rivers
 
Posts: n/a
Default


In article writes:

Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.


Then what other physical phenomenon accounts for the sound?


It's really all about frequency response, no any single frequency
response curve accurately characterizes the sound of a microphone,
other than perhaps a true omni mic (and there are darn few of those).

Since the frequency response curve changes (significantly) depending
on the direction from which the sound is coming when it reaches the
microphone, and since few things that we'd actually want to record
produce sound that goes in a straight line (only), you have to take
into account the fact that the frequency response for that particular
recording isn't going to look like the published curve. It (like a
speaker measured in natural habitat) will probably look pretty rough,
and you'd say "I'd never use a microphone with frequency response like
that." But you do. Microphones, like any transducers, are always imperfect.

Generally, when frequency response varies in a smooth and predictable
manner as you go off axis, a microphone will be considered "less
colored" which means the frequency response is more even. On the other
hand, if you like the frequency response curve 30 degrees off axis,
you can get that sound by pointing the mic so that an imaginary line
30 degrees from straight-on is pointing to the source. But then you've
gotta watch those reflections.

And then there's transient response.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo
  #28   Report Post  
Arny Krueger
 
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Bob Cain wrote:

Oh, by frequency response I presume both magnitude and phase
were implied.


Since the use of multiple mics in the same sound field is common, and the
outputs are frequently added, phase is much more important than usual.


  #29   Report Post  
Arny Krueger
 
Posts: n/a
Default

Bob Cain wrote:

Oh, by frequency response I presume both magnitude and phase
were implied.


Since the use of multiple mics in the same sound field is common, and the
outputs are frequently added, phase is much more important than usual.


  #30   Report Post  
Arny Krueger
 
Posts: n/a
Default

Bob Cain wrote:

Oh, by frequency response I presume both magnitude and phase
were implied.


Since the use of multiple mics in the same sound field is common, and the
outputs are frequently added, phase is much more important than usual.




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



Mike Rivers wrote:


It's really all about frequency response, no any single frequency
response curve accurately characterizes the sound of a microphone,
other than perhaps a true omni mic (and there are darn few of those).


Yep. Its the response as a function of frequency, angle of
incidence to the plane of the diaphragm and the rotation
angle about the axis.

I would dearly love to find some real data measurments,
taken at an incidence resolution of a few degrees, which
would disclose the spatial frequency response of any
directional mic but while we claim that it is such a big
factor, I have never seen and have looked hard, for any real
data to back that up.

I would be especially interested in such data from a few
well known mics for comparative analysis.

Intuition tells me that the on axis response is the
predominant factor and that the angular variations from that
are going to be a very similar function across microphones
of similar size but I need data (or the time to gather it
some day) to prove or disprove that.

The frequency response, magnitude and group delay,
encompasses the transient response. Any system's response
to the shortest transient is isomporphic to its frequency
response.

People usually think "phase" but for audio and I wish we
could change that. It's really group delay or time
dispersion that we hear and are interested in. Phase was of
interest for closed loop systems wherein the whole frequency
domain thing was developed and phase gave information about
stability, but for open loop systems and especially with
respect to perception it's all about dispersion or group
delay as a function of frequency.


Bob
--

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

A. Einstein
  #32   Report Post  
Bob Cain
 
Posts: n/a
Default



Mike Rivers wrote:


It's really all about frequency response, no any single frequency
response curve accurately characterizes the sound of a microphone,
other than perhaps a true omni mic (and there are darn few of those).


Yep. Its the response as a function of frequency, angle of
incidence to the plane of the diaphragm and the rotation
angle about the axis.

I would dearly love to find some real data measurments,
taken at an incidence resolution of a few degrees, which
would disclose the spatial frequency response of any
directional mic but while we claim that it is such a big
factor, I have never seen and have looked hard, for any real
data to back that up.

I would be especially interested in such data from a few
well known mics for comparative analysis.

Intuition tells me that the on axis response is the
predominant factor and that the angular variations from that
are going to be a very similar function across microphones
of similar size but I need data (or the time to gather it
some day) to prove or disprove that.

The frequency response, magnitude and group delay,
encompasses the transient response. Any system's response
to the shortest transient is isomporphic to its frequency
response.

People usually think "phase" but for audio and I wish we
could change that. It's really group delay or time
dispersion that we hear and are interested in. Phase was of
interest for closed loop systems wherein the whole frequency
domain thing was developed and phase gave information about
stability, but for open loop systems and especially with
respect to perception it's all about dispersion or group
delay as a function of frequency.


Bob
--

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

A. Einstein
  #33   Report Post  
Bob Cain
 
Posts: n/a
Default



Mike Rivers wrote:


It's really all about frequency response, no any single frequency
response curve accurately characterizes the sound of a microphone,
other than perhaps a true omni mic (and there are darn few of those).


Yep. Its the response as a function of frequency, angle of
incidence to the plane of the diaphragm and the rotation
angle about the axis.

I would dearly love to find some real data measurments,
taken at an incidence resolution of a few degrees, which
would disclose the spatial frequency response of any
directional mic but while we claim that it is such a big
factor, I have never seen and have looked hard, for any real
data to back that up.

I would be especially interested in such data from a few
well known mics for comparative analysis.

Intuition tells me that the on axis response is the
predominant factor and that the angular variations from that
are going to be a very similar function across microphones
of similar size but I need data (or the time to gather it
some day) to prove or disprove that.

The frequency response, magnitude and group delay,
encompasses the transient response. Any system's response
to the shortest transient is isomporphic to its frequency
response.

People usually think "phase" but for audio and I wish we
could change that. It's really group delay or time
dispersion that we hear and are interested in. Phase was of
interest for closed loop systems wherein the whole frequency
domain thing was developed and phase gave information about
stability, but for open loop systems and especially with
respect to perception it's all about dispersion or group
delay as a function of frequency.


Bob
--

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

A. Einstein
  #34   Report Post  
David Satz
 
Posts: n/a
Default

Bob Cain wrote:

Intuition tells me that the on axis response is the predominant
factor and that the angular variations from that are going to be
a very similar function across microphones of similar size [ ... ]


Two early morning thoughts:

[a] The response actually heard on a recording will be somewhere between
a microphone's on-axis response and its diffuse-field response, but how
close it is to the one curve or the other depends on the miking distance
and the recording environment.

Diffuse-field response usually ends up being more important to the sound
than most people seem to expect. Even in a close-up recording, more off-
axis sound energy is picked up, and is heard in the result, than most
people seem to think will occur. With moderately distant miking or in
classical music-style recording which can be truly distant, the on-axis
sound energy is a small fraction of the total.

[b] The capsule's design and construction has a huge effect on its polar
response at various frequencies, and this can't be predicted from its size
alone, especially in pressure gradient transducers.

The Neumann U 87 for example has a rather drastic (but reasonably smooth)
loss of high-frequency response off axis, while other microphones of
similar size may have bumpy, elevated high frequency response off-axis.
That matters a lot to the overall character of a mike's sound in a room.

--best regards
  #35   Report Post  
David Satz
 
Posts: n/a
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Bob Cain wrote:

Intuition tells me that the on axis response is the predominant
factor and that the angular variations from that are going to be
a very similar function across microphones of similar size [ ... ]


Two early morning thoughts:

[a] The response actually heard on a recording will be somewhere between
a microphone's on-axis response and its diffuse-field response, but how
close it is to the one curve or the other depends on the miking distance
and the recording environment.

Diffuse-field response usually ends up being more important to the sound
than most people seem to expect. Even in a close-up recording, more off-
axis sound energy is picked up, and is heard in the result, than most
people seem to think will occur. With moderately distant miking or in
classical music-style recording which can be truly distant, the on-axis
sound energy is a small fraction of the total.

[b] The capsule's design and construction has a huge effect on its polar
response at various frequencies, and this can't be predicted from its size
alone, especially in pressure gradient transducers.

The Neumann U 87 for example has a rather drastic (but reasonably smooth)
loss of high-frequency response off axis, while other microphones of
similar size may have bumpy, elevated high frequency response off-axis.
That matters a lot to the overall character of a mike's sound in a room.

--best regards


  #36   Report Post  
David Satz
 
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Bob Cain wrote:

Intuition tells me that the on axis response is the predominant
factor and that the angular variations from that are going to be
a very similar function across microphones of similar size [ ... ]


Two early morning thoughts:

[a] The response actually heard on a recording will be somewhere between
a microphone's on-axis response and its diffuse-field response, but how
close it is to the one curve or the other depends on the miking distance
and the recording environment.

Diffuse-field response usually ends up being more important to the sound
than most people seem to expect. Even in a close-up recording, more off-
axis sound energy is picked up, and is heard in the result, than most
people seem to think will occur. With moderately distant miking or in
classical music-style recording which can be truly distant, the on-axis
sound energy is a small fraction of the total.

[b] The capsule's design and construction has a huge effect on its polar
response at various frequencies, and this can't be predicted from its size
alone, especially in pressure gradient transducers.

The Neumann U 87 for example has a rather drastic (but reasonably smooth)
loss of high-frequency response off axis, while other microphones of
similar size may have bumpy, elevated high frequency response off-axis.
That matters a lot to the overall character of a mike's sound in a room.

--best regards
  #37   Report Post  
Bob Cain
 
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David Satz wrote:


The Neumann U 87 for example has a rather drastic (but reasonably smooth)
loss of high-frequency response off axis, while other microphones of
similar size may have bumpy, elevated high frequency response off-axis.
That matters a lot to the overall character of a mike's sound in a room.


David, do you know of any source of full band polar
measurement data on that or other mics?


Bob
--

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

A. Einstein
  #38   Report Post  
Bob Cain
 
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David Satz wrote:


The Neumann U 87 for example has a rather drastic (but reasonably smooth)
loss of high-frequency response off axis, while other microphones of
similar size may have bumpy, elevated high frequency response off-axis.
That matters a lot to the overall character of a mike's sound in a room.


David, do you know of any source of full band polar
measurement data on that or other mics?


Bob
--

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

A. Einstein
  #39   Report Post  
Bob Cain
 
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David Satz wrote:


The Neumann U 87 for example has a rather drastic (but reasonably smooth)
loss of high-frequency response off axis, while other microphones of
similar size may have bumpy, elevated high frequency response off-axis.
That matters a lot to the overall character of a mike's sound in a room.


David, do you know of any source of full band polar
measurement data on that or other mics?


Bob
--

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

A. Einstein
  #40   Report Post  
Peter Larsen
 
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David Bock wrote:

" Frequency response and sound of mic is no better correlated than
frequency response and sound of loudspeaker.
OldBluesman

Kind regards
Peter Larsen"


Not true, you just need to see enough different kinds of measurements
and learn how to read them.


30, 60, 90, 120, 180 degrees off axis response curves help. But static
frequency response does not reveal things like membrane and housing
resonances. Add waterfall diagrams and then things begin to get
correlated. With static curves it is only possible to see that some mic
has "a problem" at say 5 and at 12 kHz, because front to rear separation
is poorer, but not positively whether it is a problem with a resonance.

And all of that is still not the response in terms of tonal balance of
recorded sound, to some extent because some "issues" are catered for in
the positioning and angling of the actual mics in question. Some mics,
such as those I use and could afford second hand, ARE better at having a
violin slight off of their axis ...

Expect to see more info on this in the coming years as major
mic mfg's work w/the AES to create more useable
standards to address your very comment.


Very good news, thanks!

regards,
David Bock
Soundelux Microphones



Kind regards

Peter Larsen

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* My site is at: http://www.muyiovatki.dk *
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