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"phase" curve on a mic (kind of a silly question)

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Anonymous
January 8, 2005 1:50:25 AM

Archived from groups: rec.audio.pro (More info?)

hello everyone,

i'd like to "un-stupid" myself on something:

lets say you have a flat recorded signal. then you apply an eq curve
with a mixer to boost the treble. this will cause a phase-response
somewhere in the waveform.

when i look at condenser mics frequency plots, they very often have a
huge treble bump in their response patterns. does this mean the mics
are incurring this same sort of phase response as a boosting the treble
on a mixer?

i'm thinking the answer is "no"... which means you kind of get "free"
treble boost from a condenser mic without the phase issues that a mixer
eq boost would induce.

so what's the right answer?
Anonymous
January 8, 2005 2:45:10 AM

Archived from groups: rec.audio.pro (More info?)

genericaudioperson@hotmail.com wrote:

> i'm thinking the answer is "no"... which means you kind of get "free"
> treble boost from a condenser mic without the phase issues that a mixer
> eq boost would induce.
>
> so what's the right answer?

I don't think so. The bump implies a resonance and a
resonance implies a shifting phase response.


Bob
--

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

A. Einstein
Anonymous
January 8, 2005 10:04:21 AM

Archived from groups: rec.audio.pro (More info?)

On 7 Jan 2005 22:50:25 -0800, genericaudioperson@hotmail.com wrote:

>so what's the right answer?

The right answer to your question is "no" ,but the right question
is still waiting to be asked. Purists about religious content on
this newsgroup now have the floor. (Agnostics: hush...... hush).

Chris Hornbeck
Related resources
Can't find your answer ? Ask !
Anonymous
January 8, 2005 11:29:19 AM

Archived from groups: rec.audio.pro (More info?)

thanks for all the responses.

let me re-ask the question in a simpler way:

what causes a single-diaphragm cardioid condenser mic to have a huge
frequency bump around 10K?

what i'm getting at is this: if you *know* you want a bright, hyped
sound, maybe a bright mic will give you that without the phase-shift
that happens whan applying a normal eq.
Anonymous
January 8, 2005 11:32:14 AM

Archived from groups: rec.audio.pro (More info?)

thanks Arny,

that's a good point about how aggregating weird combinations of eq in a
mix can cause bad results.
Anonymous
January 8, 2005 12:52:05 PM

Archived from groups: rec.audio.pro (More info?)

<genericaudioperson@hotmail.com> wrote:
>i'd like to "un-stupid" myself on something:
>
>lets say you have a flat recorded signal. then you apply an eq curve
>with a mixer to boost the treble. this will cause a phase-response
>somewhere in the waveform.

If your EQ is an analogue IIR filter. And, if it's a minimum phase system,
which most analogue EQ networks are, you can predict the phase response
from the slope and frequency of the filter.

>when i look at condenser mics frequency plots, they very often have a
>huge treble bump in their response patterns. does this mean the mics
>are incurring this same sort of phase response as a boosting the treble
>on a mixer?

Depends on what causes it. Most of the microphone problems you see are
going to be minimum phase, but not all of them are.

And it gets more complicated, because I suspect you have never seen an
accurate microphone response plot. The plots that manufacturers provide
are VERY heavily smoothed and don't have any real detail, so you miss out
on all of the narrower resonance problems.

>I'M THinking the answer is "no"... which means you kind of get "free"
>treble boost from a condenser mic without the phase issues that a mixer
>eq boost would induce.

What do you mean by "phase issues?" The phase shift that you get with an
equalizer is good and useful for the most part.

You might want to play around with a digital FIR filter some time, which has
no group delay. It's weird to work with, but sometimes useful.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
January 8, 2005 1:08:56 PM

Archived from groups: rec.audio.pro (More info?)

On 8 Jan 2005 08:29:19 -0800, genericaudioperson@hotmail.com wrote:

>what i'm getting at is this: if you *know* you want a bright, hyped
>sound, maybe a bright mic will give you that without the phase-shift
>that happens whan applying a normal eq. <snip>

Go back and re-read Allison. He's quite correct on this subject.
Phase shift follows freq response deviations, and microphones are no
exception.

dB
Anonymous
January 8, 2005 2:05:05 PM

Archived from groups: rec.audio.pro (More info?)

Hi, generic. A condenser microphone can have a high-frequency response
peak due to the acoustical properties of the capsule and capsule head
arrangement (underdamped resonance), electrical equalization within the
microphone's circuitry, or perhaps some combination of the two.

Resonances that cause response peaks also cause deviations from linear
phase around the same frequencies, and all common analog peaking (EQ)
circuits do likewise. So if you take a "peaky" microphone and equalize
its peak away, you most likely are smoothing its phase response at the
same time.

Of course not every condenser microphone has a high-frequency peak, let
alone a huge one, or a peak that's around the particular frequency
range that you mentioned. If any high frequency peak exists, it's
generally because the manufacturer hopes that artificial brightness
will increase sales ("This microphone has enormous 'resolution', an
'open' sound, and will really make your vocals 'cut through' a mix.").

Some condenser microphones are essentially ruler-flat across the entire
audio band, so the condenser principle itself is definitely not the
cause; measurement microphones, as you probably know, are generally
condensers.

--best regards
Anonymous
January 8, 2005 4:42:36 PM

Archived from groups: rec.audio.pro (More info?)

<genericaudioperson@hotmail.com> wrote in message
news:1105201759.844374.289770@c13g2000cwb.googlegroups.com...
> thanks for all the responses.
>
> let me re-ask the question in a simpler way:
>
> what causes a single-diaphragm cardioid condenser mic to have a huge
> frequency bump around 10K?
>
> what i'm getting at is this: if you *know* you want a bright, hyped
> sound, maybe a bright mic will give you that without the phase-shift
> that happens whan applying a normal eq.
>

which condenser mic? most of the pro grade mics that i'm am familiar with
are very flat over their operating range.
Anonymous
January 8, 2005 4:43:27 PM

Archived from groups: rec.audio.pro (More info?)

<genericaudioperson@hotmail.com> wrote:
>
>what causes a single-diaphragm cardioid condenser mic to have a huge
>frequency bump around 10K?

Marketing. Vendors think people want presence peaks, so they build them
into microphones. You can get plenty of cardioid condensers out there
that have no presence hump and no spikiness in the top octave. They are
not really pushed to the project studio crowd, though.

>what i'm getting at is this: if you *know* you want a bright, hyped
>sound, maybe a bright mic will give you that without the phase-shift
>that happens whan applying a normal eq.

No, you get the same phase shift, or somewhat different phase shift. But
I don't see anything wrong with phase shift.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
January 8, 2005 4:47:17 PM

Archived from groups: rec.audio.pro (More info?)

DeserTBoB <desertb@rglobal.net> wrote:
>On 8 Jan 2005 08:29:19 -0800, genericaudioperson@hotmail.com wrote:
>
>>what i'm getting at is this: if you *know* you want a bright, hyped
>>sound, maybe a bright mic will give you that without the phase-shift
>>that happens whan applying a normal eq. <snip>
>
>Go back and re-read Allison. He's quite correct on this subject.
>Phase shift follows freq response deviations, and microphones are no
>exception.

Microphones CAN be an exception. For the most part, you will never see
electronics that aren't minimum phase unless they're specifically designed
not to be. But a lot of mechanical and acoustical systems aren't minimum
phase. You'll find microphones aren't always, especially when you talk about
narrowband body resonances.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
January 8, 2005 5:49:33 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Depends on what causes it. Most of the microphone problems you see are
> going to be minimum phase, but not all of them are.

Right. It's mixed phase if they are directional because
pure delay is contained in the transfer function.

I hate to talk above Phil's head but it is often necessasary.


Bob
--

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

A. Einstein
Anonymous
January 8, 2005 9:00:00 PM

Archived from groups: rec.audio.pro (More info?)

In article <1105201759.844374.289770@c13g2000cwb.googlegroups.com> genericaudioperson@hotmail.com writes:

> what causes a single-diaphragm cardioid condenser mic to have a huge
> frequency bump around 10K?

The designer (or the marketing department). They want it to sound nice
and "airy" and that's how to do it. It's usually a combination of the
electronics and the construction of the microphone mechanism itself.

> what i'm getting at is this: if you *know* you want a bright, hyped
> sound, maybe a bright mic will give you that without the phase-shift
> that happens whan applying a normal eq.

Exactly. That's one reason why people chose to use the mics they do.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
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 here: double-m-eleven-double-zero at yahoo
Anonymous
January 8, 2005 9:35:47 PM

Archived from groups: rec.audio.pro (More info?)

<genericaudioperson@hotmail.com>

>
> lets say you have a flat recorded signal. then you apply an eq curve
> with a mixer to boost the treble. this will cause a phase-response
> somewhere in the waveform.
>
> when i look at condenser mics frequency plots, they very often have a
> huge treble bump in their response patterns. does this mean the mics
> are incurring this same sort of phase response as a boosting the treble
> on a mixer?
>
> i'm thinking the answer is "no"... which means you kind of get "free"
> treble boost from a condenser mic without the phase issues that a mixer
> eq boost would induce.
>
> so what's the right answer?
>


** With one exception - the phase response of a device always follows the
frequency response, no matter what mechanism ( mechanical or electrical) is
causing the frequency response to vary.

The one exception is something called an "all pass filter" which varies
phase while marinating a flat frequency response - not very common
circuits in audio systems.




.............. Phil
Anonymous
January 8, 2005 9:35:48 PM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:349gqkF3tpo6rU1@individual.net

> ** With one exception - the phase response of a device always
> follows the frequency response, no matter what mechanism ( mechanical
> or electrical) is causing the frequency response to vary.

This is the so-called minimum phase characteristic. Electrical filters and
analog audio electronics are minimum phase as, a rule. Notable exceptions
exist, such as delay lines (reverb boxes).

> The one exception is something called an "all pass filter" which
> varies phase while marinating a flat frequency response - not very
> common circuits in audio systems.

Ironically, most directional microphones and virtually all multi-driver
speakers have all-pass, non-minimum phase response.

So, getting back to the OP:

> <genericaudioperson@hotmail.com>

>> lets say you have a flat recorded signal. then you apply an eq curve
>> with a mixer to boost the treble. this will cause a phase-response
>> somewhere in the waveform.

True, unless you use a non-minimum phase eq which is now not uncommon in
DAW software. A case in point would be the FFT filter in Audition. Most
other Audition equalizers are minimum-phase, or approximately so.

>> when i look at condenser mics frequency plots, they very often have a
>> huge treble bump in their response patterns. does this mean the mics
>> are incurring this same sort of phase response as a boosting the
>> treble on a mixer?

Probably, but not certainly. Omnidirectional mics tend to be minimum phase,
and therefore their frequency response and phase response are tied together
in a similar fashion as an electrical equalizer circuit. The formal name for
this connection is called the Hibert transform.

OTOH, cardioid mics operate on the basis of the mixing of sound from two or
more different locations that are separated by acoustical delays. It's not
reasonable to expect cardioid and other directional mics to be minimum phase
at all frequencies. IOW, the phase shift of directional microphones can be
all over the place.

>> i'm thinking the answer is "no"... which means you kind of get "free"
>> treble boost from a condenser mic without the phase issues that a
>> mixer eq boost would induce.

No, there is no free lunch in audio.

However, the phase shift due to equalization is not necessarily a problem.
The ear is relatively insensitive to phase shift that is equally applied to
both channels. A lot of the real-world problems with phase shift in the
recording process are due to different phase shifts that are applied to
different sources that are mixed together.

If phase shift was really that much of a problem, we wouldn't be able to
stand to listen to loudspeakers, and in rooms.

>> so what's the right answer?

Forget about free lunches in audio. Don't be paranoid about using
equalization. But do exercise appropriate care, particularly when mixing
different versions of the same basic musical source.
Anonymous
January 9, 2005 12:00:19 AM

Archived from groups: rec.audio.pro (More info?)

David Satz wrote:

> ("This microphone has enormous 'resolution', an 'open' sound, and will
> really make your vocals 'cut through' a mix.").

"Like a blunt axe through oatmeal!!"

--
ha
Anonymous
January 9, 2005 1:57:14 AM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger"
> "Phil Allison"
>> ** With one exception - the phase response of a device always
>> follows the frequency response, no matter what mechanism ( mechanical
>> or electrical) is causing the frequency response to vary.
>
> This is the so-called minimum phase characteristic.


** Don't tell anybody Arny - but that term just means an absence of all
pass filters.


> Electrical filters and analog audio electronics are minimum phase as, a
> rule.

** Yep


> Notable exceptions exist, such as delay lines (reverb boxes).


** Time delay devices are all pass filters.


>> The one exception is something called an "all pass filter" which
>> varies phase while marinating a flat frequency response - not very
>> common circuits in audio systems.
>
> Ironically, most directional microphones and virtually all multi-driver
> speakers have all-pass, non-minimum phase response.


** But Arny is too coy to say what that is due to.


> So, getting back to the OP:
>
>> <genericaudioperson@hotmail.com>


** Having screwed over my post with his asinine mumbo jumbo.



>>> lets say you have a flat recorded signal. then you apply an eq curve
>>> with a mixer to boost the treble. this will cause a phase-response
>>> somewhere in the waveform.
>
> True, unless you use a non-minimum phase eq which is now not uncommon in
> DAW software. A case in point would be the FFT filter in Audition. Most
> other Audition equalizers are minimum-phase, or approximately so.
>


** The point is lost in the over use of unnecessary jargon.

IOW More of Kreuger's mumbo jumbo.


>>> when i look at condenser mics frequency plots, they very often have a
>>> huge treble bump in their response patterns. does this mean the mics
>>> are incurring this same sort of phase response as a boosting the
>>> treble on a mixer?
>
> Probably, but not certainly. Omnidirectional mics tend to be minimum
> phase, and therefore their frequency response and phase response are tied
> together in a similar fashion as an electrical equalizer circuit. The
> formal name for this connection is called the Hibert transform.


** Arny has just swallowed whole some load of BS on the net.

Can't even spell Hilbert either.



> OTOH, cardioid mics operate on the basis of the mixing of sound from two
> or more different locations that are separated by acoustical delays. It's
> not reasonable to expect cardioid and other directional mics to be minimum
> phase at all frequencies. IOW, the phase shift of directional microphones
> can be all over the place.


** The throw away "all over the place" is not a helpful summary.

More of Kreuger's gobbledegook.


>>> i'm thinking the answer is "no"... which means you kind of get "free"
>>> treble boost from a condenser mic without the phase issues that a
>>> mixer eq boost would induce.
>
> No, there is no free lunch in audio.
>


** Or much good free advice.




................ Phil
Anonymous
January 9, 2005 12:25:52 PM

Archived from groups: rec.audio.pro (More info?)

hank alrich <walkinay@thegrid.net> wrote:
>David Satz wrote:
>
>> ("This microphone has enormous 'resolution', an 'open' sound, and will
>> really make your vocals 'cut through' a mix.").
>
>"Like a blunt axe through oatmeal!!"

I have a microphone sitting on the bench right now which fits this description
perfectly. The frequency response plot looks like a hedgehog centered around
6 KC or so. I sent a copy of the plot to the "manufacturer" to ask if it was
really supposed to be this way, and I was told basically that nobody had ever
done a narrowband plot on those mikes...
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
January 9, 2005 1:31:31 PM

Archived from groups: rec.audio.pro (More info?)

<genericaudioperson@hotmail.com>
>
> let me re-ask the question in a simpler way:
>
> what causes a single-diaphragm cardioid condenser mic to have a huge
> frequency bump around 10K?
>


** When the wavelength of a sound is comparable to the diameter of the
microphone capsule there is an acoustic pressure doubling effect that
increases the output by up to 6 dB. The larger the mic capsule the lower the
frequency where this effect starts. A 10kHz sound has a wavelength in air
of 34 mm.

With most dynamic mics the effect is exploited to extend the frequency
range - with condensers it produces a rising response at some high frequency
if nothing is done to counteract it.

Mics for test and measurement are usually made very small to put this
effect out of the audible range.




............... Phil
Anonymous
January 9, 2005 2:49:00 PM

Archived from groups: rec.audio.pro (More info?)

"Bob Cain"
>
> Scott Dorsey wrote:
>
>> Depends on what causes it. Most of the microphone problems you see are
>> going to be minimum phase, but not all of them are.
>
> Right. It's mixed phase if they are directional because pure delay is
> contained in the transfer function.
>
> I hate to talk above Phil's head but it is often necessasary.
>
>


** You are not likely to be talking over *anyone's head* while using your
arse as the source of speech.


Sound waves arriving from the rear of a cardioid mic and entering the ports
are delayed by tiny amount ( circa 20 - 40 microseconds) to equalise the
path lengths with waves travelling around the outside of the capsule. Hence
the pressures are exactly in phase on both sides of the diaphragm and there
is no output. Since the rear path to the diaphragm is obstructed short
wavelengths cannot pass as easily as lower ones do - hence the
cancellation effect fails at higher audio frequencies. Cardioids do still
manage around 10 dB front to back ratio at 10 kHz - but then so too do
many omnis !

However, for sound waves arriving *on axis* the time delay to reach the rear
of the diaphragm is greater by that same tiny amount which increases the
output. But at high audio frequencies the delayed wave loses amplitude at
the diaphragm and the mic returns to mostly omni operation. A rising high
frequency response will be simply due to the usual pressure doubling effect
as wavelength approaches the diameter of the diaphragm and/or the nature of
the diaphragm itself. The rear path time delay is simply not involved and
so response and phase will closely follow.


This is an easy to follow explanation of the cardioid mic principle.

http://www.prosoundweb.com/install/spotlight/cardioid/c...





............ Phil
Anonymous
January 9, 2005 2:49:01 PM

Archived from groups: rec.audio.pro (More info?)

Phil Allison wrote:

> This is an easy to follow explanation of the cardioid mic principle.
>
> http://www.prosoundweb.com/install/spotlight/cardioid/c...

Here's a couple not quite so easy:

http://www.arcanemethods.com/single_diaphragm_paper.pdf

http://www.arcanemethods.com/dual_diaphragm_paper.pdf

These are linked without permission because the author has
disappeared to the best of my ability to determine.


Bob
--

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

A. Einstein
Anonymous
January 9, 2005 4:48:45 PM

Archived from groups: rec.audio.pro (More info?)

David Satz wrote:

> Hi, generic. A condenser microphone can have a high-frequency response
> peak due to the acoustical properties of the capsule and capsule head
> arrangement (underdamped resonance), electrical equalization within the
> microphone's circuitry, or perhaps some combination of the two.

The general mechanism the question is about is the inverse of the baffle
diffraction step that occurs with loudspeakers, ie. a pressure build up
in front of the diaphragm and/or mic housing. The parameter that matters
is size of mic compared to wavelength of sound. Generally the on axis
response or the off axis response can be made linear, but not both.
Special design tricks, ie. the pointed nose of one of the special grids
for the dpa ommis can be used to make both identical, but strictly
speaking, very strictly, not totally and fully linear. All things equal,
to whatever degree they may be, smaller mics are more likely to have a
linear high end than larger mics unless a presence boost is applied via
acoustic resonance.

> Resonances that cause response peaks also cause deviations from linear
> phase around the same frequencies, and all common analog peaking (EQ)
> circuits do likewise. So if you take a "peaky" microphone and equalize
> its peak away, you most likely are smoothing its phase response at the
> same time.

Yes. EQ generally compensates also phase response to at least some
extent. Issues that are caused by narrow mechanical and/or acoustic
resonances ARE however problematic, especially if delayed resonance is
involved.

The issues are quite the same for mics as they are for loudspeakers,
including that cabinet design is a part of the acoustic design and not
just cosmetics.

The largest single problem with phase response is that those that write
hifi magazines seem to fail to comprehend that proper EQ generally is
minimum phase EQ and gets the phase if not right, then at least less
wrong when applied. Which is why one of the things to listen for when
EQ-ing by ear is whether the room rendering is improved.


Kind regards

Peter Larsen


--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************
Anonymous
January 9, 2005 5:28:41 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> hank alrich <walkinay@thegrid.net> wrote:
>
>>David Satz wrote:
>>
>>
>>>("This microphone has enormous 'resolution', an 'open' sound, and will
>>>really make your vocals 'cut through' a mix.").
>>
>>"Like a blunt axe through oatmeal!!"
>
>
> I have a microphone sitting on the bench right now which fits this description
> perfectly. The frequency response plot looks like a hedgehog centered around
> 6 KC or so. I sent a copy of the plot to the "manufacturer" to ask if it was
> really supposed to be this way, and I was told basically that nobody had ever
> done a narrowband plot on those mikes...
> --scott


6 KC? KC??? Scott!! Your age is showing!
Anonymous
January 10, 2005 12:56:13 AM

Archived from groups: rec.audio.pro (More info?)

"Bob Cain"
>
> Phil Allison wrote:
>
>> This is an easy to follow explanation of the cardioid mic principle.
>>
>> http://www.prosoundweb.com/install/spotlight/cardioid/c...
>
> Here's a couple not quite so easy:


** Seeing as you snipped my whole post and ignored my URL - you know
where to shove yours .

Same smelly windy place all your ideas emanate from .




................... Phil
Anonymous
January 13, 2005 2:50:13 AM

Archived from groups: rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in
news:34cgueF49ljlmU1@individual.net:

>
> "Bob Cain"
>>
>> Phil Allison wrote:
>>
>>> This is an easy to follow explanation of the cardioid mic
>>> principle.
>>>
>>> http://www.prosoundweb.com/install/spotlight/cardioid/c...
>>> html
>>
>> Here's a couple not quite so easy:
>
>
> ** Seeing as you snipped my whole post and ignored my URL - you
> know where to shove yours .
>
> Same smelly windy place all your ideas emanate from .
>
> .................. Phil
>



Correct, except on one important point. Bob Cain doesn't have ideas. He
only has opinions, and most of them are wrong.
!