Linearity of dynamic response?
Fran Guidry
Brauner VM1 and a Soundelux U195, and adjusted the levels so they
seemed matched on a passage played at normal fingerstyle steel string
guitar levels. He then noticed that the Brauner was much more sensitive
to low level signals and less sensitive to hot transients.
This called to mind the times I've heard LDCs described as "too
sensitive" for stage use, or "picking up eveything" compared to dynamic
mics.
So my questions are two.
First, how does preamp gain interact with mic sensitivity? My naive
assumption is that a low sens mic and a high gain setting should have
the same result as a high sens mic and a low gain setting. Am I missing
something?
Second, is part of the magic of some (tube?) LDCs "in the mic"
compression, resulting in the "detail" and "intimacy" that are often
attributed to these mics.
Thanks a bunch for your input,
Fran
Phil Allison
news:1134946744.7...@g14g2000cwa.googlegroups.com...
** Another Groupie......
> My recording buddy has been auditioning LDCs lately.
** LDC = large diaphragm condenser mic.
> He put up a
> Brauner VM1 and a Soundelux U195, and adjusted the levels so they
> seemed matched on a passage played at normal fingerstyle steel string
> guitar levels. He then noticed that the Brauner was much more sensitive
> to low level signals and less sensitive to hot transients.
** Yawn ....
> This called to mind the times I've heard LDCs described as "too
> sensitive" for stage use, or "picking up eveything" compared to dynamic
> mics.
** Do you want to discuss mics or anonymous silly comments ?
> So my questions are two.
>
> First, how does preamp gain interact with mic sensitivity? My naive
> assumption is that a low sens mic and a high gain setting should have
> the same result as a high sens mic and a low gain setting. Am I missing
> something?
** Not on this one, at least.
> Second, is part of the magic of some (tube?) LDCs "in the mic"
> compression, resulting in the "detail" and "intimacy" that are often
> attributed to these mics.
** No.
You have to wake up that mics are just dumb objects.
The stuff some gullible folk *say* about them is wild and wacky rot.
....... Phil
David Satz
someone else's subjective impressions, asking a bunch of strangers to
help explain those reported impressions, and offering up a number of
highly questionable claims about "LDCs" and transients for us to
validate. It's not exactly a recipe for getting a simple, positive
reponse on a newsgroup such as this.
You say that your friend adjusted the levels from two types of
microphone so that they seemed to match while one type of music was
being played, then noticed that with another type of music, the
dynamics picked up by the two mikes seemed to differ. That's no
surprise. There could be many explanations for it, some of which would
be much simpler than the ones you seem to be considering. But again,
unfortunately the simplest explanation isn't always correct in a given
case. There can very well be multiple factors, including some that can
only be guessed at in a third-hand analysis.
You certainly touched on some very basic issues when you asked how
preamp gain interacts with microphone sensitivity. If we step outside
the real world and just look at signal voltages in isolation, those two
things add in a straightforward way. If we take the signals from a
microphone with 5 mv/Pa sensitivity and feed them through a preamp with
36 dB of gain, the result will be the same as taking the signals from
an otherwise identical microphone at the same moment in time and facing
in the same direction from the same point in space, but with 10 mv/Pa
sensitivity (i.e. twice as great), and feeding them through a preamp
with only 30 dB of gain (i.e. half as great). But as all the qualifying
phrases indicate, that is an abstract comparison. I didn't even begin
to get into any of the issues on the preamp side.
One unavoidable fact is this: A person simply can't match levels by ear
in any meaningful way between two different-sounding pickups of complex
sonic material with lots of transient energy in it. The result will
depend far too much on what aspects of the sound the listener chooses
to focus on. The margin of error when trying to do this might be as
much as 4 or 5 dB, while for serious comparisons, you need a much
closer match than that (certainly less than 1 dB difference in
sensitivty + preamp gain).
The usual way of lining up two microphones for such comparisons would
be to use a 1 kHz tone. But apples and oranges are different fruits
even if two instances of them have the same diameter. Or to step down
from the metaphoric soapbox for a moment, an otherwise sensible
comparison can yield nonsense if the level matching isn't right, but
the validity of any meaningful experiment will depend on many other
things as well. We all weren't there (apparently including you) when
this comparison took place, so who knows what actually went on and why
your friend thought he heard what he thought he heard?
It should be obvious, for example, that a limiter or compressor could
cause effects like what your friend described. It would be nice if we
could simply assume that there was no limiter or compressor in the
chain, but your message didn't say that--and there are people in this
world who use those things so routinely that they forget what limiters
and compressors do. Similarly we don't know whether any of the
associated equipment was close to overloading and/or what its overload
behavior is like.
As you can see, Phil Allison reacted strongly in his reply to certain,
let's call them "hearsay" elements in your posting. Please forgive his
legendary dismissiveness, but many if not most general notions which
people seem to have about the supposed character of "LDCs" are
somewhere in the range from being too vague to make any sense at all on
the one hand, and just plain wrong on the other. Similarly, most of
what many audiophiles seem to think they know about transients is
fairly nonsensical on any serious technical level.
So unfortunately I can't do a lot to clear up what created the
impressions that your friend told you he has, but maybe this can help
to inject a grain or two of reasonable doubt into any easy assumptions
that he might be tempted to make. If he or you can narrow the focus to
something a bit more specific and manageable for discussion, there'd be
more hope of getting directly positive results.
--best regards
Fran Guidry
Just having my understanding of preamp gain & mic sensitivity confirmed
was very valuable, and I appreciate your patience.
I agree that my question was coming from some vague observations. I had
hoped that we could put some pink noise into both mics at various
volumes to explore their sensitivities at different levels, but he had
to return the loaners before we did the testing.
Now that I've considered the question a bit, it seems obvious that
there would be non-linearities in sensitivity vs. source volume just as
there are non-linearities in almost every aspect of transducer
performance. It's all just a matter of degree, right?
Thanks again,
Fran
Paul Stamler
> Now that I've considered the question a bit, it seems obvious that
> there would be non-linearities in sensitivity vs. source volume just as
> there are non-linearities in almost every aspect of transducer
> performance. It's all just a matter of degree, right?
Yes, but with most condenser mics they're inconsequential until you get to
the point where the microphone is overloading.
Peace,
Paul
Phil Allison
"Fran Guidry"
** You are simply not interested in facts - at all.
Have you no appreciation that non-linearity >>> harmonic distortion ?
Mics are linear as all get out only falling down when the SPL becomes so
HUGE they mechanically or electrically overload.
Ears and human brains are non-linear as hell.
......... Phil
Fran Guidry
Phil Allison wrote:
> "Fran Guidry"
<snipped>
> > Now that I've considered the question a bit, it seems obvious that
> > there would be non-linearities in sensitivity vs. source volume just as
> > there are non-linearities in almost every aspect of transducer
> > performance. It's all just a matter of degree, right?
>
>
>
> ** You are simply not interested in facts - at all.
I'm sorry if it seems that way. Facts are what I'm hoping to learn.
>
> Have you no appreciation that non-linearity >>> harmonic distortion ?
>
No, honestly, I don't have that appreciation. My technical knowledge of
audio is embarrassingly slim. Thanks for pointing that out.
> Mics are linear as all get out only falling down when the SPL becomes so
> HUGE they mechanically or electrically overload.
That's good to know. I honestly had no idea that this was true. I've
seen polar graphs of response patterns, I've seen frequency response
graphs, but I've never seen specs for dynamic accuracy. If it's a
given, that would explain why it's not a point of comparison.
>
> Ears and human brains are non-linear as hell.
>
This I know from experience.
Thanks,
Fran
Phil Allison
"Fran Guidry"
> Phil Allison wrote:
>>
>> > Now that I've considered the question a bit, it seems obvious that
>> > there would be non-linearities in sensitivity vs. source volume just as
>> > there are non-linearities in almost every aspect of transducer
>> > performance. It's all just a matter of degree, right?
>>
>>
>> ** You are simply not interested in facts - at all.
>
> I'm sorry if it seems that way. Facts are what I'm hoping to learn.
** Fine - but those precious facts will not be uncovered the way you are
going about it.
>> Have you no appreciation that non-linearity >>> harmonic distortion ?
>>
>
> No, honestly, I don't have that appreciation. My technical knowledge of
> audio is embarrassingly slim. Thanks for pointing that out.
** Hmmm - I wonder if she has really got it so quick.
>> Mics are linear as all get out only falling down when the SPL becomes so
>> HUGE they mechanically or electrically overload.
>
> That's good to know. I honestly had no idea that this was true. I've
> seen polar graphs of response patterns, I've seen frequency response
> graphs, but I've never seen specs for dynamic accuracy. If it's a
> given, that would explain why it's not a point of comparison.
** Mics are often speced for "dynamic accuracy"
That is what the THD figure demonstrates.
>> Ears and human brains are non-linear as hell.
>>
>
> This I know from experience.
** So is it not self evident folly to use the latter to investigate the
amplitude linearity of a mic ?
........ Phil
Fran Guidry
Phil Allison wrote:
> "Fran Guidry"
> > Phil Allison wrote:
<much snippage>
> >> Ears and human brains are non-linear as hell.
> >>
> >
> > This I know from experience.
>
>
> ** So is it not self evident folly to use the latter to investigate the
> amplitude linearity of a mic ?
>
>
>
> ........ Phil
Indeed, when you put it that way, self evident folly seems like a good
description. I appreciate your willingness to go over points that are
elementary to you.
Fran
keith.b...@homemail.com
Just to add one more item to the many that could
affect the perceived non-linearies in results (regardless
of where and how they might have been introduced)....
Consider also that in the given situation, the mics
might have had significantly different polar patterns or
off-axis frequency responses, thus allowing the
difference in levels of direct to ambient sound to
differ.
Greater directionality should be able to increase the
"critical" distance at which direct sound becomes
washed out by reflections from the room.
If that doesn't make any sense or is not helpful, then
never mind. :-)
--
Keith W. Blackwell
(haven't hung out here in a very long time)