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Matt Faunce Matt Faunce is offline
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Default Missing Proximity Effect Article and Radio Microphones

A year or so back, I followed a link from here, r.a.p., to a good
article that described why the proximity effect of a cardioid microphone
goes away when the side of the diaphragm is pointed at the sound source
rather than the front, but now I can't find it. The URL was
http://81.174.169.10/odds/mic/ If you know what article I'm talking
about could you tell me if the article has a new URL? Maybe you know or
remember the guy who wrote it.

This is somewhat frivolous, but related. I don't know much about what
makes a radio mike a radio mike. But, someone commented on this picture
(link below) saying the DJ in the pic would be better off using the
right mike type and angle, and I made a simple comment back about the
angle. But I wondered, if a female DJ did in fact want to eliminate the
proximity effect using this technique, would a mike designed for radio
still be the better mike? Why is a radio mike better for radio (or
usually better, if that's the case) when used in the usual way, than a
mike singers would pick?

pic (link is to my comment, scroll up for the pic)
http://www.rawstory.com/rs/2012/03/2...ment-470703194

I'm not that interested in commenting back over there, since I have no
experience in this matter, except maybe to point him to this thread if
it illuminates anything.
--
Matt
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Scott Dorsey Scott Dorsey is offline
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Default Missing Proximity Effect Article and Radio Microphones

Matt Faunce wrote:
A year or so back, I followed a link from here, r.a.p., to a good
article that described why the proximity effect of a cardioid microphone
goes away when the side of the diaphragm is pointed at the sound source
rather than the front, but now I can't find it. The URL was
http://81.174.169.10/odds/mic/ If you know what article I'm talking
about could you tell me if the article has a new URL? Maybe you know or
remember the guy who wrote it.


But... it doesn't. The proximity effect remains no matter what direction
it's pointed in. It has only to do with the pattern of the microphone and
the distance from the source.

In fact, if you turn the microphone to the side so the source is off-axis,
you will lose the high end (since typical cardioid mikes are only cardioid at
higher frequencies and are omni down on the bottom). So the bass boost
seems even more emphasized in comparison.

But if you want to find the original article you can probably go to
archive.org and use the Wayback Machine to see if the article has been
archived.

This is somewhat frivolous, but related. I don't know much about what
makes a radio mike a radio mike. But, someone commented on this picture
(link below) saying the DJ in the pic would be better off using the
right mike type and angle, and I made a simple comment back about the
angle. But I wondered, if a female DJ did in fact want to eliminate the
proximity effect using this technique, would a mike designed for radio
still be the better mike? Why is a radio mike better for radio (or
usually better, if that's the case) when used in the usual way, than a
MIke singers would pick?

pic (link is to my comment, scroll up for the pic)
http://www.rawstory.com/rs/2012/03/2...ment-470703194


I don't have any graphics, but if the picture is Rush Limbaugh, he
uses an RE-20 which is a microphone with some trickery to greatly reduce
proximity effect. It is popular with broadcasters but it's also a
great PA mike. Tight and even pattern. No "off mike" sound for
people who can't stand still.

In fact, all of the popular broadcast mikes, from the RCA 77 to the
Sennheiser 421, Shure SM-7, EV RE-20, are also great mikes for studio
and PA applications too.

i'm not that interested in commenting back over there, since I have no
experience in this matter, except maybe to point him to this thread if
it illuminates anything.


People are too quick to categorize mikes and say "that is a kick drum mike"
and "that is a studio mike" and "that is a PA mike," when in fact good
clean microphones have a wide variety of applications.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 29 Mar 2012 22:37:33 -0400, (Scott Dorsey) wrote:

Matt Faunce wrote:
A year or so back, I followed a link from here, r.a.p., to a good
article that described why the proximity effect of a cardioid microphone
goes away when the side of the diaphragm is pointed at the sound source
rather than the front, but now I can't find it. The URL was
http://81.174.169.10/odds/mic/ If you know what article I'm talking
about could you tell me if the article has a new URL? Maybe you know or
remember the guy who wrote it.


But... it doesn't. The proximity effect remains no matter what direction
it's pointed in. It has only to do with the pattern of the microphone and
the distance from the source.

In fact, if you turn the microphone to the side so the source is off-axis,
you will lose the high end (since typical cardioid mikes are only cardioid at
higher frequencies and are omni down on the bottom). So the bass boost
seems even more emphasized in comparison.

But if you want to find the original article you can probably go to
archive.org and use the Wayback Machine to see if the article has been
archived.

This is somewhat frivolous, but related. I don't know much about what
makes a radio mike a radio mike. But, someone commented on this picture
(link below) saying the DJ in the pic would be better off using the
right mike type and angle, and I made a simple comment back about the
angle. But I wondered, if a female DJ did in fact want to eliminate the
proximity effect using this technique, would a mike designed for radio
still be the better mike? Why is a radio mike better for radio (or
usually better, if that's the case) when used in the usual way, than a
MIke singers would pick?

pic (link is to my comment, scroll up for the pic)
http://www.rawstory.com/rs/2012/03/2...ment-470703194


I don't have any graphics, but if the picture is Rush Limbaugh, he
uses an RE-20 which is a microphone with some trickery to greatly reduce
proximity effect. It is popular with broadcasters but it's also a
great PA mike. Tight and even pattern. No "off mike" sound for
people who can't stand still.

In fact, all of the popular broadcast mikes, from the RCA 77 to the
Sennheiser 421, Shure SM-7, EV RE-20, are also great mikes for studio
and PA applications too.

i'm not that interested in commenting back over there, since I have no
experience in this matter, except maybe to point him to this thread if
it illuminates anything.


People are too quick to categorize mikes and say "that is a kick drum mike"
and "that is a studio mike" and "that is a PA mike," when in fact good
clean microphones have a wide variety of applications.
--scott


That URL. I will sort out a new link over the next few days and repost
it somewhere.

As for the proximity effect. It genuinely IS absent at 90 degrees from
the microphone as the velocity component is (near as dammit) zero from
that direction, and only the pressure response is available. Sure you
lose highs from the side - diaphragm geometry sees to that. But that
is not the same thing as bass boost through proximity effect.

d
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Matt Faunce Matt Faunce is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 3/30/12 1:25 AM, Don Pearce wrote:
On 29 Mar 2012 22:37:33 -0400, (Scott Dorsey) wrote:

Matt wrote:
A year or so back, I followed a link from here, r.a.p., to a good
article that described why the proximity effect of a cardioid microphone
goes away when the side of the diaphragm is pointed at the sound source
rather than the front, but now I can't find it. The URL was
http://81.174.169.10/odds/mic/ If you know what article I'm talking
about could you tell me if the article has a new URL? Maybe you know or
remember the guy who wrote it.


But... it doesn't. The proximity effect remains no matter what direction
it's pointed in. It has only to do with the pattern of the microphone and
the distance from the source.

In fact, if you turn the microphone to the side so the source is off-axis,
you will lose the high end (since typical cardioid mikes are only cardioid at
higher frequencies and are omni down on the bottom). So the bass boost
seems even more emphasized in comparison.

But if you want to find the original article you can probably go to
archive.org and use the Wayback Machine to see if the article has been
archived.

This is somewhat frivolous, but related. I don't know much about what
makes a radio mike a radio mike. But, someone commented on this picture
(link below) saying the DJ in the pic would be better off using the
right mike type and angle, and I made a simple comment back about the
angle. But I wondered, if a female DJ did in fact want to eliminate the
proximity effect using this technique, would a mike designed for radio
still be the better mike? Why is a radio mike better for radio (or
usually better, if that's the case) when used in the usual way, than a
MIke singers would pick?

pic (link is to my comment, scroll up for the pic)
http://www.rawstory.com/rs/2012/03/2...ment-470703194


I don't have any graphics, but if the picture is Rush Limbaugh, he
uses an RE-20 which is a microphone with some trickery to greatly reduce
proximity effect. It is popular with broadcasters but it's also a
great PA mike. Tight and even pattern. No "off mike" sound for
people who can't stand still.

In fact, all of the popular broadcast mikes, from the RCA 77 to the
Sennheiser 421, Shure SM-7, EV RE-20, are also great mikes for studio
and PA applications too.

i'm not that interested in commenting back over there, since I have no
experience in this matter, except maybe to point him to this thread if
it illuminates anything.


People are too quick to categorize mikes and say "that is a kick drum mike"
and "that is a studio mike" and "that is a PA mike," when in fact good
clean microphones have a wide variety of applications.
--scott


That URL. I will sort out a new link over the next few days and repost
it somewhere.

As for the proximity effect. It genuinely IS absent at 90 degrees from
the microphone as the velocity component is (near as dammit) zero from
that direction, and only the pressure response is available. Sure you
lose highs from the side - diaphragm geometry sees to that. But that
is not the same thing as bass boost through proximity effect.

d


I goggled around last night and found that it was your article. After
Scott's reading post I thought maybe you took it down because you found
a flaw, which happens to even the best scientists... So late last night
I tested a 0.5 inch cardioid mike I have (AKG blueline) by placing it
one inch away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small speaker, so
direction will be more precise than a multi-speaker speaker. I had to
make two takes, one for each mike position, then for playback I boosted
the gain on the sideways position take to match the other. The bass
boost seemed gone at the sideways position.

I do remember listening to some sound files you put up along with your
article, which were convincing.

Since normal listening is at a distance, and highs get absorbed in the
air, won't the sideways position give you a more realistic tone?
Especially if listening to playback with headphones? I've always
imagined that sound engineers might angle their cardioid mikes closer to
the side as they move from within a foot to even closer to the source,
especially if the source comes from a tight area like a small speaker.
--
Matt
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Matt Faunce Matt Faunce is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 3/30/12 8:37 AM, Matt Faunce wrote:

I goggled around last night and found that it was your article. After
Scott's reading post I thought maybe you took it down because you found


I meant, "After reading Scott's post..."

--
Matt


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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Missing Proximity Effect Article and Radio Microphones

On Fri, 30 Mar 2012 08:37:54 -0400, Matt Faunce
wrote:

On 3/30/12 1:25 AM, Don Pearce wrote:
On 29 Mar 2012 22:37:33 -0400, (Scott Dorsey) wrote:

Matt wrote:
A year or so back, I followed a link from here, r.a.p., to a good
article that described why the proximity effect of a cardioid microphone
goes away when the side of the diaphragm is pointed at the sound source
rather than the front, but now I can't find it. The URL was
http://81.174.169.10/odds/mic/ If you know what article I'm talking
about could you tell me if the article has a new URL? Maybe you know or
remember the guy who wrote it.

But... it doesn't. The proximity effect remains no matter what direction
it's pointed in. It has only to do with the pattern of the microphone and
the distance from the source.

In fact, if you turn the microphone to the side so the source is off-axis,
you will lose the high end (since typical cardioid mikes are only cardioid at
higher frequencies and are omni down on the bottom). So the bass boost
seems even more emphasized in comparison.

But if you want to find the original article you can probably go to
archive.org and use the Wayback Machine to see if the article has been
archived.

This is somewhat frivolous, but related. I don't know much about what
makes a radio mike a radio mike. But, someone commented on this picture
(link below) saying the DJ in the pic would be better off using the
right mike type and angle, and I made a simple comment back about the
angle. But I wondered, if a female DJ did in fact want to eliminate the
proximity effect using this technique, would a mike designed for radio
still be the better mike? Why is a radio mike better for radio (or
usually better, if that's the case) when used in the usual way, than a
MIke singers would pick?

pic (link is to my comment, scroll up for the pic)
http://www.rawstory.com/rs/2012/03/2...ment-470703194

I don't have any graphics, but if the picture is Rush Limbaugh, he
uses an RE-20 which is a microphone with some trickery to greatly reduce
proximity effect. It is popular with broadcasters but it's also a
great PA mike. Tight and even pattern. No "off mike" sound for
people who can't stand still.

In fact, all of the popular broadcast mikes, from the RCA 77 to the
Sennheiser 421, Shure SM-7, EV RE-20, are also great mikes for studio
and PA applications too.

i'm not that interested in commenting back over there, since I have no
experience in this matter, except maybe to point him to this thread if
it illuminates anything.

People are too quick to categorize mikes and say "that is a kick drum mike"
and "that is a studio mike" and "that is a PA mike," when in fact good
clean microphones have a wide variety of applications.
--scott


That URL. I will sort out a new link over the next few days and repost
it somewhere.

As for the proximity effect. It genuinely IS absent at 90 degrees from
the microphone as the velocity component is (near as dammit) zero from
that direction, and only the pressure response is available. Sure you
lose highs from the side - diaphragm geometry sees to that. But that
is not the same thing as bass boost through proximity effect.

d


I goggled around last night and found that it was your article. After
Scott's reading post I thought maybe you took it down because you found
a flaw, which happens to even the best scientists... So late last night
I tested a 0.5 inch cardioid mike I have (AKG blueline) by placing it
one inch away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small speaker, so
direction will be more precise than a multi-speaker speaker. I had to
make two takes, one for each mike position, then for playback I boosted
the gain on the sideways position take to match the other. The bass
boost seemed gone at the sideways position.

I do remember listening to some sound files you put up along with your
article, which were convincing.

Since normal listening is at a distance, and highs get absorbed in the
air, won't the sideways position give you a more realistic tone?
Especially if listening to playback with headphones? I've always
imagined that sound engineers might angle their cardioid mikes closer to
the side as they move from within a foot to even closer to the source,
especially if the source comes from a tight area like a small speaker.


The problem here is that most recordings are made in real rooms, so
the sound arrives from all sorts of angles with varying amounts of
delay. The whole purpose of the directional mic is to try and give a
little added isolation to the direct sound from those delayed
arrivals. So you put up with the proximity effect and kill it with
appropriate eq.

This is where my article can help, because it gives the correct eq for
a set of distances. When I say correct, I mean correct to kill the
proximity boost. You probably need to vary it from that point to
achieve the actual sound you want, but that is another matter.

d
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Scott Dorsey Scott Dorsey is offline
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Default Missing Proximity Effect Article and Radio Microphones

Matt Faunce wrote:
On 3/30/12 1:25 AM, Don Pearce wrote:

As for the proximity effect. It genuinely IS absent at 90 degrees from
the microphone as the velocity component is (near as dammit) zero from
that direction, and only the pressure response is available. Sure you
lose highs from the side - diaphragm geometry sees to that. But that
is not the same thing as bass boost through proximity effect.


Okay, I'll buy that argument. I guess it's something we never really notice
since the response off-axis is usually so wonky. I know that with an SM-7
when you speak up close parallel to the diaphragm you still get a massive
bass boost (but reduced popping) and a lot of broadcast guys like doing that.

Since normal listening is at a distance, and highs get absorbed in the
air, won't the sideways position give you a more realistic tone?
Especially if listening to playback with headphones? I've always
imagined that sound engineers might angle their cardioid mikes closer to
the side as they move from within a foot to even closer to the source,
especially if the source comes from a tight area like a small speaker.


Could be, but then you have all the other response problems that come from
being off-axis. If you want a realistic tone up close, either use an omni
or use equalization. There's no crime in using equalization, especially if
you have a mike with a built-in compensation filter.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 30 Mar 2012 10:32:14 -0400, (Scott Dorsey) wrote:

Matt Faunce wrote:
On 3/30/12 1:25 AM, Don Pearce wrote:

As for the proximity effect. It genuinely IS absent at 90 degrees from
the microphone as the velocity component is (near as dammit) zero from
that direction, and only the pressure response is available. Sure you
lose highs from the side - diaphragm geometry sees to that. But that
is not the same thing as bass boost through proximity effect.


Okay, I'll buy that argument. I guess it's something we never really notice
since the response off-axis is usually so wonky. I know that with an SM-7
when you speak up close parallel to the diaphragm you still get a massive
bass boost (but reduced popping) and a lot of broadcast guys like doing that.


Yes, but when you are up close, 90 degrees just isn't possible. Sound
emerges from the whole front of your face - not just your mouth. So
the bass boost is still going to happen.

Since normal listening is at a distance, and highs get absorbed in the
air, won't the sideways position give you a more realistic tone?
Especially if listening to playback with headphones? I've always
imagined that sound engineers might angle their cardioid mikes closer to
the side as they move from within a foot to even closer to the source,
especially if the source comes from a tight area like a small speaker.


Could be, but then you have all the other response problems that come from
being off-axis. If you want a realistic tone up close, either use an omni
or use equalization. There's no crime in using equalization, especially if
you have a mike with a built-in compensation filter.
--scott


No crime? I'd say it is pretty much mandatory.

d
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Mike Rivers Mike Rivers is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.


How much bass do you get out of a metronome? A better
experiment would be to speak an inch from the front of the
mic, then an inch from the side of the mic. Then a foot from
the front of the mic and a foot from the side of the mic.

That proximity effect goes away (or doesn't) off to the side
of a cardioid mic is really kind of a silly premise, though.
The mic simply sounds different off axis than on axis. And
there's no sharp a dividing line. I would expect the amount
of proximity effect to be reduced off axis, but even an inch
away, there will still be some sound getting into the front
of the mic, so you'll hear some proximity effect.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff
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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Missing Proximity Effect Article and Radio Microphones

On Fri, 30 Mar 2012 12:24:12 -0400, Mike Rivers
wrote:

On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.


How much bass do you get out of a metronome? A better
experiment would be to speak an inch from the front of the
mic, then an inch from the side of the mic. Then a foot from
the front of the mic and a foot from the side of the mic.

That proximity effect goes away (or doesn't) off to the side
of a cardioid mic is really kind of a silly premise, though.
The mic simply sounds different off axis than on axis. And
there's no sharp a dividing line. I would expect the amount
of proximity effect to be reduced off axis, but even an inch
away, there will still be some sound getting into the front
of the mic, so you'll hear some proximity effect.


I will be reposting the web page soon, so you can both see and hear
what this is all about. You may be surprised - but then again, maybe
not.

d


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Peter Larsen[_3_] Peter Larsen[_3_] is offline
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Default Missing Proximity Effect Article and Radio Microphones

Scott Dorsey wrote:

Okay, I'll buy that argument. I guess it's something we never really
notice since the response off-axis is usually so wonky. I know that
with an SM-7 when you speak up close parallel to the diaphragm you
still get a massive bass boost (but reduced popping) and a lot of
broadcast guys like doing that.


"up close parallel to the diaphragm" is likely to be 70 degrees off axis
rather than 90 with that mic because the capsule is recessed that far.

Kind regards

Peter Larsen



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Matt Faunce Matt Faunce is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.


How much bass do you get out of a metronome?


This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt
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Default Missing Proximity Effect Article and Radio Microphones

On Fri, 30 Mar 2012 15:02:16 -0400, Ty Ford
wrote:

On Fri, 30 Mar 2012 01:25:11 -0400, Don Pearce wrote
(in article ):

As for the proximity effect. It genuinely IS absent at 90 degrees from the
microphone as the velocity component is (near as dammit) zero from that
direction, and only the pressure response is available. Sure you lose highs
from the side - diaphragm geometry sees to that. But that is not the same
thing as bass boost through proximity effect.

d


Holy Crap!

Don and I agree again. Oh, that's right, the world is ending on 12/12/12.

Regards,

Ty Ford


Is that the rapture? People keep promising, but it never seems to
happen.

d
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Default Missing Proximity Effect Article and Radio Microphones

On Fri, 30 Mar 2012 16:03:29 -0400, Matt Faunce
wrote:

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.


How much bass do you get out of a metronome?


This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt


The fattening is because you are hearing more of the reverberant sound
from the room, and less of the dry, direct sound.

I have to reconstruct a web site, and that isn't going to happen until
tomorrow. I'll let you know.

d
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Default Missing Proximity Effect Article and Radio Microphones

On Fri, 30 Mar 2012 20:22:10 GMT, (Don Pearce) wrote:

On Fri, 30 Mar 2012 16:03:29 -0400, Matt Faunce
wrote:

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.

How much bass do you get out of a metronome?


This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt


The fattening is because you are hearing more of the reverberant sound
from the room, and less of the dry, direct sound.

I have to reconstruct a web site, and that isn't going to happen until
tomorrow. I'll let you know.

d


OK, it all went a little quicker than I expected. Here you go:

http://www.soundthoughts.co.uk/read/mic/

d


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Matt Faunce Matt Faunce is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 3/30/12 4:22 PM, Don Pearce wrote:
On Fri, 30 Mar 2012 16:03:29 -0400, Matt
wrote:

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.

How much bass do you get out of a metronome?


This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt


The fattening is because you are hearing more of the reverberant sound
from the room, and less of the dry, direct sound.


It's fatter on axis. Fatter was probably the wrong word. The tone of the
clicks sound lower. It occurred to me that I'm hearing a plosive effect,
even though the windscreen. This makes more sense to me. So much for the
metronome idea. But I think I learned plosives make the attack sound
lower, and a lot of what I thought was proximity effect, in general
cardioid usage, was a plosive effect. But ... omnis aren't as
susceptible to wind noise. Is this related to the proximity effect or a
completely (or relatively) separate thing?

I have to reconstruct a web site, and that isn't going to happen until
tomorrow. I'll let you know.

d


Thanks.

--
Matt
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Default Missing Proximity Effect Article and Radio Microphones

On Fri, 30 Mar 2012 17:04:32 -0400, Matt Faunce
wrote:

omnis aren't as
susceptible to wind noise. Is this related to the proximity effect or a
completely (or relatively) separate thing?


Omnis are not as susceptible to wind noise because the diaphragm has a
tiny volume of air behind it - it can't flap around in the breeze.
Anything with directionality, and figure 8s are the worst, has what is
called a velocity response. It responds to air speed as well as
pressure. So air movements shift the diaphragm - and plosives are a
particularly violent air movement.

d
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Scott Dorsey Scott Dorsey is offline
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Default Missing Proximity Effect Article and Radio Microphones

Don Pearce wrote:
On Fri, 30 Mar 2012 15:02:16 -0400, Ty Ford
Don and I agree again. Oh, that's right, the world is ending on 12/12/12.


Is that the rapture? People keep promising, but it never seems to
happen.


The man from Mars stopped eating cars and bars and now he only eats guitars.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Matt Faunce Matt Faunce is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 3/30/12 5:17 PM, Don Pearce wrote:
On Fri, 30 Mar 2012 17:04:32 -0400, Matt
wrote:

omnis aren't as
susceptible to wind noise. Is this related to the proximity effect or a
completely (or relatively) separate thing?


Omnis are not as susceptible to wind noise because the diaphragm has a
tiny volume of air behind it - it can't flap around in the breeze.
Anything with directionality, and figure 8s are the worst, has what is
called a velocity response. It responds to air speed as well as
pressure. So air movements shift the diaphragm - and plosives are a
particularly violent air movement.

d


Thanks Don, and thanks for the article.

I was looking at this gif of water particles moving with water waves to
help me grasp what's going on with air pressure waves and particles. I
think the lowest of the three red dots best represents air particle
motion from a sound wave.

http://en.wikipedia.org/wiki/File:Sh...water_wave.gif
--
Matt


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Mike Rivers Mike Rivers is offline
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Default Missing Proximity Effect Article and Radio Microphones

On 3/30/2012 5:04 PM, Matt Faunce wrote:

It's fatter on axis. Fatter was probably the wrong word. The
tone of the clicks sound lower. It occurred to me that I'm
hearing a plosive effect, even though the windscreen. This
makes more sense to me. So much for the metronome idea. But
I think I learned plosives make the attack sound lower, and
a lot of what I thought was proximity effect, in general
cardioid usage, was a plosive effect.


This puts me in mind of a demonstration that I constructed
several years back for an article about acoustic polarity.
Google me and polarity demonstration and you'll probably
find the WAV file. What most people heard was that the
sawtooth waveform that was playing lost some bass when the
polarity was inverted. Those who refused to believe that
this was a result of a change in polarity claimed that it
had to do with the phase response of their speakers.

In any case, when you move the sound source off to the side,
you change its phase, and hence polarity, relation to the
on-axis source. It could be that this is what you're hearing
with the metronome.

Or not.

--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff
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Ralph Barone[_2_] Ralph Barone[_2_] is offline
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Default Missing Proximity Effect Article and Radio Microphones

Scott Dorsey wrote:
Don Pearce wrote:
On Fri, 30 Mar 2012 15:02:16 -0400, Ty Ford
Don and I agree again. Oh, that's right, the world is ending on 12/12/12.


Is that the rapture? People keep promising, but it never seems to
happen.


The man from Mars stopped eating cars and bars and now he only eats guitars.
--scott


For a song that some say heralded commercial rap music, Rapture was a
horrible song. No, wait, I guess it does make sense...
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Default Missing Proximity Effect Article and Radio Microphones

Ralph Barone wrote:

I find it amusing that everyone freaks out because the Mayan calendar ends
in 2012, but you can't buy a modern calendar that's more than 18 months
long. Perhaps the Mayans figured "Well, that should do us for a while...".


Nailed! If they'd started with a bigger rock we wouldn't be having these
trepidations.

--
shut up and play your guitar * http://hankalrich.com/
http://www.youtube.com/walkinaymusic
http://www.sonicbids.com/HankandShaidri
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Default Missing Proximity Effect Article and Radio Microphones

Don Pearce wrote:

On Fri, 30 Mar 2012 20:22:10 GMT, (Don Pearce) wrote:

On Fri, 30 Mar 2012 16:03:29 -0400, Matt Faunce
wrote:

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.

How much bass do you get out of a metronome?

This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt


The fattening is because you are hearing more of the reverberant sound
from the room, and less of the dry, direct sound.

I have to reconstruct a web site, and that isn't going to happen until
tomorrow. I'll let you know.

d


OK, it all went a little quicker than I expected. Here you go:

http://www.soundthoughts.co.uk/read/mic/



The critical point, which is missing from most descriptions of the
Proximity Effect, is that it is caused by the expansion of a spherical
wavefront.

If we use a ribbon mic as an example, the ribbon is driven by a
difference in pressure between its two sides which is cause by a
difference in the path length to the front and back as the sound
wavefront passes. The electrical ouput is proportional to the velocity
of the ribbon movement, but the ribbon resonance is below audio
frequency; so, as the frequency goes down, the ribbon velocity and
output would increase if the pressure difference remained constant.

With a plane wave (from a distant source) the path difference between
the front and back of the ribbon becomes a smaller and smaller
proportion of a cycle as the frequency goes down, so the pressure
difference falls with falling frequency. This exactly compensates for
the increasing sensitivity of the ribbon system and the result is a flat
frequency response.

Independently of this, a spherical wavefront expands and falls in
pressure as its radius increases. It will give different pressures on
each side of the ribbon because it will have expanded more and dropped
in pressure by the time it reaches the back of the ribbon. This effect
does not decrease with frequency, so the rising sensitivity of the
ribbon system will give increasing output as the frequency falls.

The ratio of spherical to plane wavefront effect is what determines the
frequency below which the 'expansion' response becomes larger than the
'phase difference' response and bass tip-up begins to occur.


Even in an excellent book such as Robertson's "Microphones", this
information is buried in a load of mathematics in a theoretical
discussion and not presented clearly as a practical explanation. I have
never seen a satisfactory explanation in any practical microphone book,
although I have seen several disgracefully incorrect ones.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
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Default Missing Proximity Effect Article and Radio Microphones

On Sat, 31 Mar 2012 09:35:08 +0100,
lid (Adrian Tuddenham) wrote:

Don Pearce wrote:

On Fri, 30 Mar 2012 20:22:10 GMT,
(Don Pearce) wrote:

On Fri, 30 Mar 2012 16:03:29 -0400, Matt Faunce
wrote:

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.

How much bass do you get out of a metronome?

This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt

The fattening is because you are hearing more of the reverberant sound
from the room, and less of the dry, direct sound.

I have to reconstruct a web site, and that isn't going to happen until
tomorrow. I'll let you know.

d


OK, it all went a little quicker than I expected. Here you go:

http://www.soundthoughts.co.uk/read/mic/



The critical point, which is missing from most descriptions of the
Proximity Effect, is that it is caused by the expansion of a spherical
wavefront.

If we use a ribbon mic as an example, the ribbon is driven by a
difference in pressure between its two sides which is cause by a
difference in the path length to the front and back as the sound
wavefront passes. The electrical ouput is proportional to the velocity
of the ribbon movement, but the ribbon resonance is below audio
frequency; so, as the frequency goes down, the ribbon velocity and
output would increase if the pressure difference remained constant.

With a plane wave (from a distant source) the path difference between
the front and back of the ribbon becomes a smaller and smaller
proportion of a cycle as the frequency goes down, so the pressure
difference falls with falling frequency. This exactly compensates for
the increasing sensitivity of the ribbon system and the result is a flat
frequency response.

Independently of this, a spherical wavefront expands and falls in
pressure as its radius increases. It will give different pressures on
each side of the ribbon because it will have expanded more and dropped
in pressure by the time it reaches the back of the ribbon. This effect
does not decrease with frequency, so the rising sensitivity of the
ribbon system will give increasing output as the frequency falls.

The ratio of spherical to plane wavefront effect is what determines the
frequency below which the 'expansion' response becomes larger than the
'phase difference' response and bass tip-up begins to occur.


Even in an excellent book such as Robertson's "Microphones", this
information is buried in a load of mathematics in a theoretical
discussion and not presented clearly as a practical explanation. I have
never seen a satisfactory explanation in any practical microphone book,
although I have seen several disgracefully incorrect ones.


I've seen this explanation before, and I really don't buy it. The
distance between the front and back of a ribbon is essentially zero,
so the differential due to added expansion is absent. I don't pretend
to have delved too deeply into this, but if you look at the equation
in my paper, the term on the left is velocity. There is no term for
front-to-back distance in the mic.

Now I can quite see that in a spherical wavefront the further you are
from the mic, the larger is the volume contained in a single cycle of
sound. This difference is greater the lower the frequency, so the
velocity of air needed to fill and empty the space is increased. But
it is simply that - the velocity of air increases. You don't need to
consider the front-to-back distance of the microphone.

Obviously by the time you get a good distance away (or the wavelength
is short enough) the volume of two successive waves is essentially the
same, and the bass boost is reduced - but never quite absent, of
course.

d




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Default Missing Proximity Effect Article and Radio Microphones

Don Pearce wrote:

On Sat, 31 Mar 2012 09:35:08 +0100,
lid (Adrian Tuddenham) wrote:

Don Pearce wrote:

On Fri, 30 Mar 2012 20:22:10 GMT,
(Don Pearce) wrote:

On Fri, 30 Mar 2012 16:03:29 -0400, Matt Faunce
wrote:

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.

How much bass do you get out of a metronome?

This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt

The fattening is because you are hearing more of the reverberant sound
from the room, and less of the dry, direct sound.

I have to reconstruct a web site, and that isn't going to happen until
tomorrow. I'll let you know.

d

OK, it all went a little quicker than I expected. Here you go:

http://www.soundthoughts.co.uk/read/mic/



The critical point, which is missing from most descriptions of the
Proximity Effect, is that it is caused by the expansion of a spherical
wavefront.

If we use a ribbon mic as an example, the ribbon is driven by a
difference in pressure between its two sides which is cause by a
difference in the path length to the front and back as the sound
wavefront passes. The electrical ouput is proportional to the velocity
of the ribbon movement, but the ribbon resonance is below audio
frequency; so, as the frequency goes down, the ribbon velocity and
output would increase if the pressure difference remained constant.

With a plane wave (from a distant source) the path difference between
the front and back of the ribbon becomes a smaller and smaller
proportion of a cycle as the frequency goes down, so the pressure
difference falls with falling frequency. This exactly compensates for
the increasing sensitivity of the ribbon system and the result is a flat
frequency response.

Independently of this, a spherical wavefront expands and falls in
pressure as its radius increases. It will give different pressures on
each side of the ribbon because it will have expanded more and dropped
in pressure by the time it reaches the back of the ribbon. This effect
does not decrease with frequency, so the rising sensitivity of the
ribbon system will give increasing output as the frequency falls.

The ratio of spherical to plane wavefront effect is what determines the
frequency below which the 'expansion' response becomes larger than the
'phase difference' response and bass tip-up begins to occur.


Even in an excellent book such as Robertson's "Microphones", this
information is buried in a load of mathematics in a theoretical
discussion and not presented clearly as a practical explanation. I have
never seen a satisfactory explanation in any practical microphone book,
although I have seen several disgracefully incorrect ones.


I've seen this explanation before, and I really don't buy it. The
distance between the front and back of a ribbon is essentially zero,
...[...]


It's easy enough to check: take two miniature pressure capsules and
wire them in antiphase. Place them touching and expose them to sound;
with a bit of balancing, the electrical output can be reduced to zero.

http://www.poppyrecords.co.uk/other/images/MicTest1.gif


Now pull them apart by various small distances and see what effect you
get with sound which reaches one after the other. Alternatively,
interpose obstacles of various sizes and see what the increased path
length does. You will find that increasing the path length by either
method increases the sensitivity of the doublet. You will also find
that the plane-wave response sounds very harsh because it is caused by
the 'phase difference' effect which increases at 6dB/octave. The
response to a spherical wave will be flat.

If you now integrate the signal by putting a 'large' capacitor across
the amplifier terminals, the response to a distant source will become
flat (up to the point where the path difference between the capsules
approaches half a wavelength) and the spherical response will increase
with decreasing frequency. This is equivalent to the condition brought
about by working the ribbon above its resonance frequency.

Perhaps many aspects of this demonstration fit with your theory too, but
the path-difference explanation certainly covers all the observed
phenomena.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
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Scott Dorsey Scott Dorsey is offline
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Default Missing Proximity Effect Article and Radio Microphones

On Sat, 31 Mar 2012 00:28:28 -0400, Ralph Barone wrote

I find it amusing that everyone freaks out because the Mayan calendar ends in
2012, but you can't buy a modern calendar that's more than 18 months long.
Perhaps the Mayans figured "Well, that should do us for a while...".


Look at Sly Stone. His brain ended in 1972 but he's still around.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Default Missing Proximity Effect Article and Radio Microphones

On Sat, 31 Mar 2012 12:23:00 +0100,
lid (Adrian Tuddenham) wrote:

Don Pearce wrote:

On Sat, 31 Mar 2012 09:35:08 +0100,
lid (Adrian Tuddenham) wrote:

Don Pearce wrote:

On Fri, 30 Mar 2012 20:22:10 GMT,
(Don Pearce) wrote:

On Fri, 30 Mar 2012 16:03:29 -0400, Matt Faunce
wrote:

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.

How much bass do you get out of a metronome?

This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt

The fattening is because you are hearing more of the reverberant sound
from the room, and less of the dry, direct sound.

I have to reconstruct a web site, and that isn't going to happen until
tomorrow. I'll let you know.

d

OK, it all went a little quicker than I expected. Here you go:

http://www.soundthoughts.co.uk/read/mic/


The critical point, which is missing from most descriptions of the
Proximity Effect, is that it is caused by the expansion of a spherical
wavefront.

If we use a ribbon mic as an example, the ribbon is driven by a
difference in pressure between its two sides which is cause by a
difference in the path length to the front and back as the sound
wavefront passes. The electrical ouput is proportional to the velocity
of the ribbon movement, but the ribbon resonance is below audio
frequency; so, as the frequency goes down, the ribbon velocity and
output would increase if the pressure difference remained constant.

With a plane wave (from a distant source) the path difference between
the front and back of the ribbon becomes a smaller and smaller
proportion of a cycle as the frequency goes down, so the pressure
difference falls with falling frequency. This exactly compensates for
the increasing sensitivity of the ribbon system and the result is a flat
frequency response.

Independently of this, a spherical wavefront expands and falls in
pressure as its radius increases. It will give different pressures on
each side of the ribbon because it will have expanded more and dropped
in pressure by the time it reaches the back of the ribbon. This effect
does not decrease with frequency, so the rising sensitivity of the
ribbon system will give increasing output as the frequency falls.

The ratio of spherical to plane wavefront effect is what determines the
frequency below which the 'expansion' response becomes larger than the
'phase difference' response and bass tip-up begins to occur.


Even in an excellent book such as Robertson's "Microphones", this
information is buried in a load of mathematics in a theoretical
discussion and not presented clearly as a practical explanation. I have
never seen a satisfactory explanation in any practical microphone book,
although I have seen several disgracefully incorrect ones.


I've seen this explanation before, and I really don't buy it. The
distance between the front and back of a ribbon is essentially zero,
...[...]


It's easy enough to check: take two miniature pressure capsules and
wire them in antiphase. Place them touching and expose them to sound;
with a bit of balancing, the electrical output can be reduced to zero.

http://www.poppyrecords.co.uk/other/images/MicTest1.gif


Now pull them apart by various small distances and see what effect you
get with sound which reaches one after the other. Alternatively,
interpose obstacles of various sizes and see what the increased path
length does. You will find that increasing the path length by either
method increases the sensitivity of the doublet. You will also find
that the plane-wave response sounds very harsh because it is caused by
the 'phase difference' effect which increases at 6dB/octave. The
response to a spherical wave will be flat.

If you now integrate the signal by putting a 'large' capacitor across
the amplifier terminals, the response to a distant source will become
flat (up to the point where the path difference between the capsules
approaches half a wavelength) and the spherical response will increase
with decreasing frequency. This is equivalent to the condition brought
about by working the ribbon above its resonance frequency.

Perhaps many aspects of this demonstration fit with your theory too, but
the path-difference explanation certainly covers all the observed
phenomena.


Sure, I understand that interposing the obstacles causes a phase shift
between the two, resulting in poor cancellation. And the 6dB per
octave also makes sense, up to the point where a half wave is being
approached and the effect starts to turn over.

But that isn't the same as a velocity-gradient induced pressure
difference between two points a thousandth of an inch apart.

d
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Default Missing Proximity Effect Article and Radio Microphones

Don Pearce wrote:

On Sat, 31 Mar 2012 12:23:00 +0100,
lid (Adrian Tuddenham) wrote:

Don Pearce wrote:

On Sat, 31 Mar 2012 09:35:08 +0100,
lid (Adrian Tuddenham) wrote:

Don Pearce wrote:

On Fri, 30 Mar 2012 20:22:10 GMT,
(Don Pearce) wrote:

On Fri, 30 Mar 2012 16:03:29 -0400, Matt Faunce
wrote:

On 3/30/12 12:24 PM, Mike Rivers wrote:
On 3/30/2012 8:37 AM, Matt Faunce wrote:

.. So late last night I tested a 0.5 inch
cardioid mike I have (AKG blueline) by placing it one inch
away from my metronome speaker which clicks at two different
pitches. I used the metronome because it has a single small
speaker, so direction will be more precise than a
multi-speaker speaker. I had to make two takes, one for each
mike position, then for playback I boosted the gain on the
sideways position take to match the other. The bass boost
seemed gone at the sideways position.

How much bass do you get out of a metronome?

This is another question that I'm not sure I know enough to even
articulate. I still hear a fattening effect. Maybe the mike isn't
boosting the bass frequencies of the metronome, but fattening the
attack. Or is it converting the attack into a bass frequency?

I haven't gotten the physics of proximity effect straight in my head
yet. So Don, I'll be looking forward to going back your article.

Matt

The fattening is because you are hearing more of the reverberant sound
from the room, and less of the dry, direct sound.

I have to reconstruct a web site, and that isn't going to happen until
tomorrow. I'll let you know.

d

OK, it all went a little quicker than I expected. Here you go:

http://www.soundthoughts.co.uk/read/mic/


The critical point, which is missing from most descriptions of the
Proximity Effect, is that it is caused by the expansion of a spherical
wavefront.

If we use a ribbon mic as an example, the ribbon is driven by a
difference in pressure between its two sides which is cause by a
difference in the path length to the front and back as the sound
wavefront passes. The electrical ouput is proportional to the velocity
of the ribbon movement, but the ribbon resonance is below audio
frequency; so, as the frequency goes down, the ribbon velocity and
output would increase if the pressure difference remained constant.

With a plane wave (from a distant source) the path difference between
the front and back of the ribbon becomes a smaller and smaller
proportion of a cycle as the frequency goes down, so the pressure
difference falls with falling frequency. This exactly compensates for
the increasing sensitivity of the ribbon system and the result is a flat
frequency response.

Independently of this, a spherical wavefront expands and falls in
pressure as its radius increases. It will give different pressures on
each side of the ribbon because it will have expanded more and dropped
in pressure by the time it reaches the back of the ribbon. This effect
does not decrease with frequency, so the rising sensitivity of the
ribbon system will give increasing output as the frequency falls.

The ratio of spherical to plane wavefront effect is what determines the
frequency below which the 'expansion' response becomes larger than the
'phase difference' response and bass tip-up begins to occur.


Even in an excellent book such as Robertson's "Microphones", this
information is buried in a load of mathematics in a theoretical
discussion and not presented clearly as a practical explanation. I have
never seen a satisfactory explanation in any practical microphone book,
although I have seen several disgracefully incorrect ones.

I've seen this explanation before, and I really don't buy it. The
distance between the front and back of a ribbon is essentially zero,
...[...]


It's easy enough to check: take two miniature pressure capsules and
wire them in antiphase. Place them touching and expose them to sound;
with a bit of balancing, the electrical output can be reduced to zero.

http://www.poppyrecords.co.uk/other/images/MicTest1.gif


Now pull them apart by various small distances and see what effect you
get with sound which reaches one after the other. Alternatively,
interpose obstacles of various sizes and see what the increased path
length does. You will find that increasing the path length by either
method increases the sensitivity of the doublet. You will also find
that the plane-wave response sounds very harsh because it is caused by
the 'phase difference' effect which increases at 6dB/octave. The
response to a spherical wave will be flat.

If you now integrate the signal by putting a 'large' capacitor across
the amplifier terminals, the response to a distant source will become
flat (up to the point where the path difference between the capsules
approaches half a wavelength) and the spherical response will increase
with decreasing frequency. This is equivalent to the condition brought
about by working the ribbon above its resonance frequency.

Perhaps many aspects of this demonstration fit with your theory too, but
the path-difference explanation certainly covers all the observed
phenomena.


Sure, I understand that interposing the obstacles causes a phase shift
between the two, resulting in poor cancellation. And the 6dB per
octave also makes sense, up to the point where a half wave is being
approached and the effect starts to turn over.

But that isn't the same as a velocity-gradient induced pressure
difference between two points a thousandth of an inch apart.


They are only a thousandth of an inch apart "as the crow flies" (through
the thickness of the ribbon), but the pathway which the sound takes
around the pole pieces is much longer. As an example, in the STC 4038
the path difference through the air between one side of the ribbon and
the other is almost an inch. The designers also interposed resistive
screens in that pathway to correct the frequency response.

http://downloads.bbc.co.uk/rd/pubs/a...raphs/bbc_mono
graph_04.pdf


The formula you quoted may be adequate for one particular microphone,
but it needs to include a term which accounts for the change in
sensitivity with change in path difference if it is to explain all the
observed aspects of the phenomenon.

I also find it is much easier to understand bass-lift if it is explained
in terms of two different causes of pressure difference across the
ribbon.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
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Default Missing Proximity Effect Article and Radio Microphones

On Sat, 31 Mar 2012 17:05:50 +0100,
lid (Adrian Tuddenham) wrote:

Sure, I understand that interposing the obstacles causes a phase shift
between the two, resulting in poor cancellation. And the 6dB per
octave also makes sense, up to the point where a half wave is being
approached and the effect starts to turn over.

But that isn't the same as a velocity-gradient induced pressure
difference between two points a thousandth of an inch apart.


They are only a thousandth of an inch apart "as the crow flies" (through
the thickness of the ribbon), but the pathway which the sound takes
around the pole pieces is much longer. As an example, in the STC 4038
the path difference through the air between one side of the ribbon and
the other is almost an inch. The designers also interposed resistive
screens in that pathway to correct the frequency response.

http://downloads.bbc.co.uk/rd/pubs/a...raphs/bbc_mono
graph_04.pdf


The formula you quoted may be adequate for one particular microphone,
but it needs to include a term which accounts for the change in
sensitivity with change in path difference if it is to explain all the
observed aspects of the phenomenon.


The formula isn't for any kind of microphone. It is for air velocity.
Even a zero width, zero thickness ribbon suspended in free air will
suffer this bass lift.

I also find it is much easier to understand bass-lift if it is explained
in terms of two different causes of pressure difference across the
ribbon.


Like the Bohr atom, maybe easier to understand, but wrong.

d


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Default Missing Proximity Effect Article and Radio Microphones

Don Pearce wrote:

On Sat, 31 Mar 2012 17:05:50 +0100,
lid (Adrian Tuddenham) wrote:

Sure, I understand that interposing the obstacles causes a phase shift
between the two, resulting in poor cancellation. And the 6dB per
octave also makes sense, up to the point where a half wave is being
approached and the effect starts to turn over.

But that isn't the same as a velocity-gradient induced pressure
difference between two points a thousandth of an inch apart.


They are only a thousandth of an inch apart "as the crow flies" (through
the thickness of the ribbon), but the pathway which the sound takes
around the pole pieces is much longer. As an example, in the STC 4038
the path difference through the air between one side of the ribbon and
the other is almost an inch. The designers also interposed resistive
screens in that pathway to correct the frequency response.

http://downloads.bbc.co.uk/rd/pubs/a...raphs/bbc_mono
graph_04.pdf


The formula you quoted may be adequate for one particular microphone,
but it needs to include a term which accounts for the change in
sensitivity with change in path difference if it is to explain all the
observed aspects of the phenomenon.


The formula isn't for any kind of microphone. It is for air velocity.
Even a zero width, zero thickness ribbon suspended in free air will
suffer this bass lift.


If it is to usefully give the relationship between the acoustic
conditions and practical microphone output, you need to include another
term which will account for the relationship between path length and
sensitivity. As an explanation for microphone behaviour (as opposed to
air behaviour) it needs at least one more term, possibly more.


I also find it is much easier to understand bass-lift if it is explained
in terms of two different causes of pressure difference across the
ribbon.


Like the Bohr atom, maybe easier to understand, but wrong.


I think you will find it is as valid as the velocity concept. These are
just two different ways of explaining the same observed and measured
phenomena. My concern was not that the velocity calculation was
'wrong' but that it did not tell the whole story to someone who had
originally enquired about microphone responses.

Published textbooks and research papers show that the BBC and STC have
been designing their ribbon microphones on the basis of path length for
many years; if the concept was wrong, they would not have continued to
use it. There may be other manufacturers who use the velocity concept -
and I'm sure their products work equally well.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
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Don Pearce[_3_] Don Pearce[_3_] is offline
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Posts: 2,417
Default Missing Proximity Effect Article and Radio Microphones

On Sat, 31 Mar 2012 17:59:08 +0100,
lid (Adrian Tuddenham) wrote:

Don Pearce wrote:

On Sat, 31 Mar 2012 17:05:50 +0100,
lid (Adrian Tuddenham) wrote:

Sure, I understand that interposing the obstacles causes a phase shift
between the two, resulting in poor cancellation. And the 6dB per
octave also makes sense, up to the point where a half wave is being
approached and the effect starts to turn over.

But that isn't the same as a velocity-gradient induced pressure
difference between two points a thousandth of an inch apart.

They are only a thousandth of an inch apart "as the crow flies" (through
the thickness of the ribbon), but the pathway which the sound takes
around the pole pieces is much longer. As an example, in the STC 4038
the path difference through the air between one side of the ribbon and
the other is almost an inch. The designers also interposed resistive
screens in that pathway to correct the frequency response.

http://downloads.bbc.co.uk/rd/pubs/a...raphs/bbc_mono
graph_04.pdf


The formula you quoted may be adequate for one particular microphone,
but it needs to include a term which accounts for the change in
sensitivity with change in path difference if it is to explain all the
observed aspects of the phenomenon.


The formula isn't for any kind of microphone. It is for air velocity.
Even a zero width, zero thickness ribbon suspended in free air will
suffer this bass lift.


If it is to usefully give the relationship between the acoustic
conditions and practical microphone output, you need to include another
term which will account for the relationship between path length and
sensitivity. As an explanation for microphone behaviour (as opposed to
air behaviour) it needs at least one more term, possibly more.


I also find it is much easier to understand bass-lift if it is explained
in terms of two different causes of pressure difference across the
ribbon.


Like the Bohr atom, maybe easier to understand, but wrong.


I think you will find it is as valid as the velocity concept. These are
just two different ways of explaining the same observed and measured
phenomena. My concern was not that the velocity calculation was
'wrong' but that it did not tell the whole story to someone who had
originally enquired about microphone responses.

Published textbooks and research papers show that the BBC and STC have
been designing their ribbon microphones on the basis of path length for
many years; if the concept was wrong, they would not have continued to
use it. There may be other manufacturers who use the velocity concept -
and I'm sure their products work equally well.


Yes, I get all that, but my paper was about a simple phenomenon that
applies universally. The vagaries and traits of individual microphones
were simply not of interest here. They are individual, and must be
compensated for on an individual basis.

All the phenomena you describe, path length, shadowing etc are
perfectly valid, and have their own consequences to the response of
the mic, but they are outside the scope of my paper, I'm afraid.

d
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