Condensers & magnetic fields

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So there I was dangling an NT-4 down the back of my fridge recording the
weird gurgling sound it was making, which I could maybe slow down & turn
into some Eraserhead style atmospherics, when I thought "can the magnetic
fields around motors & compresser pumps damage condenser mics?"

 

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"Karl Engel" wrote ...
> So there I was dangling an NT-4 down the back of my
> fridge recording the weird gurgling sound it was making,
> which I could maybe slow down & turn into some Eraserhead
> style atmospherics, when I thought "can the magnetic fields
> around motors & compresser pumps damage condenser mics?"

I'd be concerned about the grunge and grime back there.
The magnetic field (if there are any of significant strength)
can only affect things like built-in transformers, etc. Nothing
about condenser (externally-biased or elecctret) elements that
is sensitive to a magnetic field.

In fact, if collecting sounds in a magnetic field, you would
most certainly want a condenser and NOT a magnetic mic!

Didn't I hear somewhere that the sound of the laser sabres
in the original StarWars was collected from the sync buzz
on an old TV receiver?

 

[Guest]

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<< when I thought "can the magnetic
fields around motors & compresser pumps damage condenser mics?"
>>

If so, every mic which has been placed in front of a speaker cabinet would have
been damaged as well.


Scott Fraser

 

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Karl Engel <karlengel-at-excite-dot-com> wrote:
>So there I was dangling an NT-4 down the back of my fridge recording the
>weird gurgling sound it was making, which I could maybe slow down & turn
>into some Eraserhead style atmospherics, when I thought "can the magnetic
>fields around motors & compresser pumps damage condenser mics?"

No, but they _can_ cause noise pickup on dynamics and ribbon mikes.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

 

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On Sun, 8 Aug 2004 22:17:23 -0700, "Richard Crowley"
<rcrowley7@xprt.net> wrote:

>In fact, if collecting sounds in a magnetic field, you would
>most certainly want a condenser and NOT a magnetic mic!

Have those SM57 and SM58s we've been pointing at speaker cones all
these years been suffering?

CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm
"Possibly the world's least impressive web site": George Perfect

 

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"Laurence Payne" <l@laurenceDELETEpayne.freeserve.co.uk> wrote in message
news:03heh05fp6vc0lj8lpl9e285ll44uh2q1b@4ax.com...
> On Sun, 8 Aug 2004 22:17:23 -0700, "Richard Crowley"
> <rcrowley7@xprt.net> wrote:
>
> >In fact, if collecting sounds in a magnetic field, you would
> >most certainly want a condenser and NOT a magnetic mic!
>
> Have those SM57 and SM58s we've been pointing at speaker cones all
> these years been suffering?
>

They haven't been suffering, but this might explain why they actually sound
GOOD on cabs. Maybe the magnetic field results in an asymmetrical output
from the mic that we tend to find pleasing on these sources.

Bill Balmer

who started off thinking this was a joke response, but who knows????

 

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> "Richard Crowley" wrote:
> >In fact, if collecting sounds in a magnetic field, you would
> >most certainly want a condenser and NOT a magnetic mic!

"Laurence Payne" wrote ...
> Have those SM57 and SM58s we've been pointing at speaker
> cones all these years been suffering?

No, of course not. The OP was posting a question about a
completely different application than pointing a dynamic mic
at a dynamic speaker.

In the case of the mic/speaker, the DC component of the mag
field (the permanent magnet) will cause no signal as long as
there is no motion between the speaker and the mic. And
whatever AC magnetic field might reach the mic is actually
the very signal that you are trying to capture.

Of course it is possible that whatever magnetic fields might
eminate from the motors, etc in the original scenario could be
considered part of what the OP was trying to capture. But there
are too many variables that weren't disclosed.

 

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"Richard Crowley" <rcrowley7@xprt.net> wrote in message news:<10he274mjisgvac@corp.supernews.com>...
> "Karl Engel" wrote ...
> > So there I was dangling an NT-4 down the back of my
> > fridge recording the weird gurgling sound it was making,
> > which I could maybe slow down & turn into some Eraserhead
> > style atmospherics, when I thought "can the magnetic fields
> > around motors & compresser pumps damage condenser mics?"
>
> I'd be concerned about the grunge and grime back there.
> The magnetic field (if there are any of significant strength)
> can only affect things like built-in transformers, etc. Nothing
> about condenser (externally-biased or elecctret) elements that
> is sensitive to a magnetic field.
>
> In fact, if collecting sounds in a magnetic field, you would
> most certainly want a condenser and NOT a magnetic mic!
>
> Didn't I hear somewhere that the sound of the laser sabres
> in the original StarWars was collected from the sync buzz
> on an old TV receiver?

Nah, I can't remember who did the sound F/X but they were interviewed
in Keyboard magazine about 12 years ago and they used a pretty low
tech method to get that sound.

They took a mic (probably an SM-57 I believe) on a mic cord and swung
it back and forth in front of a fan...seriously that was it. I suspect
the combination of doppler shifts and proximity effect gave it that
mmmmwoooooooshhhhmmmmm sound.

Funny thing, these days they'd probably spend three hours searching
through a sample library for the appropriate sound whereas back in
1976 they just improvised something that worked.

Analogeezer

 

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"Cosworth" <billbalmer@worldnet.att.net> wrote in message
news:ECNRc.190610$OB3.157886@bgtnsc05-news.ops.worldnet.att.net
> "Laurence Payne" <l@laurenceDELETEpayne.freeserve.co.uk> wrote in
> message news:03heh05fp6vc0lj8lpl9e285ll44uh2q1b@4ax.com...
>> On Sun, 8 Aug 2004 22:17:23 -0700, "Richard Crowley"
>> <rcrowley7@xprt.net> wrote:
>>
>>> In fact, if collecting sounds in a magnetic field, you would
>>> most certainly want a condenser and NOT a magnetic mic!
>>
>> Have those SM57 and SM58s we've been pointing at speaker cones all
>> these years been suffering?
>>
>
> They haven't been suffering, but this might explain why they actually
> sound GOOD on cabs. Maybe the magnetic field results in an
> asymmetrical output from the mic that we tend to find pleasing on
> these sources.

I suspect that the metal case of the mic and capsule are pretty fair
magnetic shields. Even if non-ferrous, they would be pretty good shorting
turns.

The power-line related magnetic fields one finds in modern life probably
dwarf just about everything else. Control them and you've controlled a lot
of other things.

 

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in article 10hgoqqivpicge9@corp.supernews.com, Richard Crowley at
rcrowley7@xprt.net wrote on 8/10/04 1:55 AM:

Great example: using a dynamic mic as a room/stage pickup to feed a
hearing-imparied inductance loop system (for those not having encountred
this simple idea.... imagine sitting inside a giant speaker voice-coil and
picking up the audio on a headphone set attaced to a coil of wire sensing
the varying mag field from the big coil... yep: the room is wrapped in a
bunch of turns of wire and anybody sitting in/near it with a coil/amp/cans
pickup unit can hear what it's doing)

If you want to optimise what the person wearing the headphones is hearing,
then you'd push as much clean power into the transmit coil as possible,
you;d also eq and compress it so that they wouldn;t miss a word in the quiet
parts and wouldn;t be blown away by the loud parts (Just Like TV At Home!).

Now... what's that thing hanging over the stage (and well within the field
area of the transmit coil) made of again...?

 

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On 10 Aug 2004 06:00:40 -0700, analogeezer@aerosolkings.com
(Analogeezer) wrote:

>Funny thing, these days they'd probably spend three hours searching
>through a sample library for the appropriate sound whereas back in
>1976 they just improvised something that worked.

The light saber "handles" were battery holders from old Graphlex
bulb-type flashes, the kind you'd see in old movies.

Chris Hornbeck

 

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"Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in message
news:lemhh09c27aj3surngdkcsphi5v0ci3gr8@4ax.com...
> On 10 Aug 2004 06:00:40 -0700, analogeezer@aerosolkings.com
> (Analogeezer) wrote:
>
> >Funny thing, these days they'd probably spend three hours searching
> >through a sample library for the appropriate sound whereas back in
> >1976 they just improvised something that worked.
>
> The light saber "handles" were battery holders from old Graphlex
> bulb-type flashes, the kind you'd see in old movies.

And one of the spaceship control panels was a video switcher.

Peace,
Paul

 

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in article r26Sc.422690$Gx4.93521@bgtnsc04-news.ops.worldnet.att.net, Paul
Stamler at pstamlerhell@pobox.com wrote on 8/10/04 11:43 AM:

>
> "Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in message
> news:lemhh09c27aj3surngdkcsphi5v0ci3gr8@4ax.com...
>> On 10 Aug 2004 06:00:40 -0700, analogeezer@aerosolkings.com
>> (Analogeezer) wrote:
>>
>>> Funny thing, these days they'd probably spend three hours searching
>>> through a sample library for the appropriate sound whereas back in
>>> 1976 they just improvised something that worked.
>>
>> The light saber "handles" were battery holders from old Graphlex
>> bulb-type flashes, the kind you'd see in old movies.

better were the SOUNDS of the light sabers.
take 2 flavors of bad movie projector gears,
mix in HV tv power-supply hash
all hand-dopplered to perfection


>
> And one of the spaceship control panels was a video switcher.

IIRR the Death Star planet-buster beam control was a working switcher at an
LA tv facility... the whole movie is a grand example of how to salvage a
shoot with an inadequate budget for its vision. Only thing that got more out
of less was DARK STAR.

 

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analogeezer@aerosolkings.com (Analogeezer) wrote in message news:<bfb37ea9.0408100500.76f5609b@posting.google.com>...
> "Richard Crowley" <rcrowley7@xprt.net> wrote in message news:<10he274mjisgvac@corp.supernews.com>...
> > "Karl Engel" wrote ...
> > > So there I was dangling an NT-4 down the back of my
> > > fridge recording the weird gurgling sound it was making,
> > > which I could maybe slow down & turn into some Eraserhead
> > > style atmospherics, when I thought "can the magnetic fields
> > > around motors & compresser pumps damage condenser mics?"
> >
> > I'd be concerned about the grunge and grime back there.
> > The magnetic field (if there are any of significant strength)
> > can only affect things like built-in transformers, etc. Nothing
> > about condenser (externally-biased or elecctret) elements that
> > is sensitive to a magnetic field.
> >
> > In fact, if collecting sounds in a magnetic field, you would
> > most certainly want a condenser and NOT a magnetic mic!
> >
> > Didn't I hear somewhere that the sound of the laser sabres
> > in the original StarWars was collected from the sync buzz
> > on an old TV receiver?
>
> Nah, I can't remember who did the sound F/X but they were interviewed
> in Keyboard magazine about 12 years ago and they used a pretty low
> tech method to get that sound.
>
> They took a mic (probably an SM-57 I believe) on a mic cord and swung
> it back and forth in front of a fan...seriously that was it. I suspect
> the combination of doppler shifts and proximity effect gave it that
> mmmmwoooooooshhhhmmmmm sound.

I saw a talk by Ben Burtt & I'm pretty sure he said he got the sound
after leaving a radio lav mic hanging down over the back of an old TV
and noticing the hum it made; he then combined this with the hum &
whirr of a huge old projector. The swinging mic proximity effect thing
was also correct though since he said he got the dolper effect by
swinging a mic at a speaker playing this sound combo (not a fan) while
watching the film playback, AFAIRecall

 

[mark]

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

> They took a mic (probably an SM-57 I believe) on a mic cord and swung
> it back and forth in front of a fan...seriously that was it. I suspect
> the combination of doppler shifts and proximity effect gave it that
> mmmmwoooooooshhhhmmmmm sound.
>

Do you have any proof that an SM-57 swinging in front of a fan will
produce Dopplers shifts?

Oh... sorry..

wrong thread.

Mark

 

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Karl Engel wrote:
> So there I was dangling an NT-4 down the back of my fridge recording
> the weird gurgling sound it was making, which I could maybe slow down
> & turn into some Eraserhead style atmospherics, when I thought "can
> the magnetic fields around motors & compresser pumps damage condenser
> mics?"

They certainly can, if they get caught in the belt drive, or they fall on
them.

geoff

 

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Analogeezer wrote:
>
> They took a mic (probably an SM-57 I believe) on a mic cord and swung
> it back and forth in front of a fan...

Roger Daltry on a hot day ?

geoff

 

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Scott Dorsey wrote:
> Karl Engel <karlengel-at-excite-dot-com> wrote:
>> So there I was dangling an NT-4 down the back of my fridge recording
>> the weird gurgling sound it was making, which I could maybe slow
>> down & turn into some Eraserhead style atmospherics, when I thought
>> "can the magnetic fields around motors & compresser pumps damage
>> condenser mics?"
>
> No, but they _can_ cause noise pickup on dynamics and ribbon mikes.
> --scott

I guess any extrenal feild could couple nicely with a transformer in
particular, and generate a noise signal.. But damage - I think not.

geoff