A keyboard player needs to have a heart pacemaker put in. But he
has "heard" that stray magnetic fields may affect it and is
concerned about his ability to move and/or sit near his rig
due to the large magnets in his amp.

I've heard warning in the past about microwave ovens and pacemakers,
but I had never heard this about magnets. Does anyone know if this
is true?

On Fri, 19 May 2006 13:53:23 +0000 (UTC), georgeh
wrote:

A keyboard player needs to have a heart pacemaker put in. But he
has "heard" that stray magnetic fields may affect it and is
concerned about his ability to move and/or sit near his rig
due to the large magnets in his amp.

I've heard warning in the past about microwave ovens and pacemakers,
but I had never heard this about magnets. Does anyone know if this
is true?

Fields above 5 Gauss should be avoided; a static magnetic field is
used by cardiologists to put a pacemaker into a test mode, in which it
pulses regularly rather than in response to the patient's own pacing
stimulus. He would probably have to lie on the speaker to get anywhere
near this.

d

--
Pearce Consulting
http://www.pearce.uk.com

georgeh wrote:
A keyboard player needs to have a heart pacemaker put in. But he
has "heard" that stray magnetic fields may affect it and is
concerned about his ability to move and/or sit near his rig
due to the large magnets in his amp.

I've heard warning in the past about microwave ovens and pacemakers,
but I had never heard this about magnets. Does anyone know if this
is true?

Some modern pacemakers have a sensor in them... the doctor puts a
magnet over a particular place on the chest and it puts them into
a test mode. There was a Scientific American article a few years
ago.

My bet is that this takes a pretty strong field and that speaker
magnets aren't an issue. Remember the magnetic field falls off MUCH
faster than the square of the distance. Now, I would NOT put the
speaker magnet against my chest, mind you.

Tell him to ask his doctor for what the allowable field strength is.
It's probably a couple gauss, in which case if you keep any magnets
a foot or so away from your chest you should be fine.

I'd be more worried about ribbon mikes, some of which have some leakage,
and which you're a lot more apt to rub against your chest when leaning
over a rack.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Thanks Scott, I'll pass it on.

(Scott Dorsey) writes:
Some modern pacemakers have a sensor in them... the doctor puts a
magnet over a particular place on the chest and it puts them into
a test mode. There was a Scientific American article a few years
ago.

My bet is that this takes a pretty strong field and that speaker
magnets aren't an issue. Remember the magnetic field falls off MUCH
faster than the square of the distance. Now, I would NOT put the
speaker magnet against my chest, mind you.

Tell him to ask his doctor for what the allowable field strength is.
It's probably a couple gauss, in which case if you keep any magnets
a foot or so away from your chest you should be fine.

I'd be more worried about ribbon mikes, some of which have some leakage,
and which you're a lot more apt to rub against your chest when leaning
over a rack.

(Don Pearce) writes:
Fields above 5 Gauss should be avoided; a static magnetic field is
used by cardiologists to put a pacemaker into a test mode, in which it
pulses regularly rather than in response to the patient's own pacing
stimulus. He would probably have to lie on the speaker to get anywhere
near this.

Thanks Don. Followup: are the large transformers in many tube amps
a concern?

On Fri, 19 May 2006 14:14:00 +0000 (UTC), georgeh
wrote:

(Don Pearce) writes:
Fields above 5 Gauss should be avoided; a static magnetic field is
used by cardiologists to put a pacemaker into a test mode, in which it
pulses regularly rather than in response to the patient's own pacing
stimulus. He would probably have to lie on the speaker to get anywhere
near this.

Thanks Don. Followup: are the large transformers in many tube amps
a concern?

Absolutely not. They are designed to contain their fields, not radiate
them.

d

--
Pearce Consulting
http://www.pearce.uk.com

georgeh wrote:

A keyboard player needs to have a heart pacemaker put in. But he
has "heard" that stray magnetic fields may affect it and is
concerned about his ability to move and/or sit near his rig
due to the large magnets in his amp.

I've heard warning in the past about microwave ovens and pacemakers,
but I had never heard this about magnets. Does anyone know if this
is true?

This is a serious health issue that needs to be answered by a
cardiologist, not some bozos on an newgroup.

Would you even consider asking a doctor "what is the best
vocal mic under $200 ?" C'mon now ... ;-]

rd

ps - I have 2 old Bell/TRW Pacemaker PA amps that work well in the
presence of a speaker's magnetic field.

In article , (Don Pearce) wrote:
On Fri, 19 May 2006 14:14:00 +0000 (UTC), georgeh
wrote:

(Don Pearce) writes:
Fields above 5 Gauss should be avoided; a static magnetic field is
used by cardiologists to put a pacemaker into a test mode, in which it
pulses regularly rather than in response to the patient's own pacing
stimulus. He would probably have to lie on the speaker to get anywhere
near this.

They will pulse anyway if the heart does not beat.

Thanks Don. Followup: are the large transformers in many tube amps
a concern?

Absolutely not. They are designed to contain their fields, not radiate
them.

Remember when signs outside of quicky marts indicating microwave ovens?

greg

RD Jones wrote:
georgeh wrote:
A keyboard player needs to have a heart pacemaker put in. But he
has "heard" that stray magnetic fields may affect it and is
concerned about his ability to move and/or sit near his rig
due to the large magnets in his amp.

I've heard warning in the past about microwave ovens and pacemakers,
but I had never heard this about magnets. Does anyone know if this
is true?

This is a serious health issue that needs to be answered by a
cardiologist, not some bozos on an newgroup.

Would you even consider asking a doctor "what is the best
vocal mic under $200 ?" C'mon now ... ;-]

RD had the only wise response so far.

This thread caught my attention because I work for one of the largest
makers of pacemakers and ICD's in the world. I work in direct support
of their "Technical Services" group. These are the people that *the
doctors* call when they have a question about a device. I have read
some of ther documents on things like wireless microphones, wired
microphones, amplifiers, loudspeakers, etc.

It never even entered my mind to answer his question - beyond saying
"Ask this question of someone qualified to answer it for your specific
device." Wrong information could potentially kill him.

_Every_ other reply has at least some wrong information.

Austin

"AustinMN" writes:
This is a serious health issue that needs to be answered by a
cardiologist, not some bozos on an newgroup.

Would you even consider asking a doctor "what is the best
vocal mic under $200 ?" C'mon now ... ;-]

RD had the only wise response so far.

This thread caught my attention because I work for one of the largest
makers of pacemakers and ICD's in the world. I work in direct support
of their "Technical Services" group. These are the people that *the
doctors* call when they have a question about a device. I have read
some of ther documents on things like wireless microphones, wired
microphones, amplifiers, loudspeakers, etc.

It never even entered my mind to answer his question - beyond saying
"Ask this question of someone qualified to answer it for your specific
device." Wrong information could potentially kill him.

_Every_ other reply has at least some wrong information.
Austin

While I agree, I also suspect that few cardioligists have a clue
about what sorts of magnets and tranformers are contained in various
amps or PA systems. What I have gathered from this thread is
that a danger may well exist. With this info, he can go back to the
team of doctors and inquire further, whereas they may have previously
not taken his concerns seriously.

georgeh wrote:
A keyboard player needs to have a heart pacemaker put in. But he
has "heard" that stray magnetic fields may affect it and is
concerned about his ability to move and/or sit near his rig
due to the large magnets in his amp.

I've heard warning in the past about microwave ovens and pacemakers,
but I had never heard this about magnets. Does anyone know if this
is true?

These devices are required to meet a tremendous number of standards. As
such the engineering department will have records on EMI / RFI
susceptiblity along with a number of other environmental conditions.
Still there will be variances between models amd mfgs. Have your friend
find out the manufacter and exact model intended for him. Contact the
tech support for that company and inquire about this specific concern
on that particular model. They will have access to the engineering test
records. Anything less is conjecture and potentially dangerous.

bobs

Bob Smith
BS Studios
we organize chaos
http://www.bsstudios.com

On Fri, 19 May 2006 13:53:23 +0000 (UTC), georgeh
wrote:

A keyboard player needs to have a heart pacemaker put in. But he
has "heard" that stray magnetic fields may affect it and is
concerned about his ability to move and/or sit near his rig
due to the large magnets in his amp.

I've heard warning in the past about microwave ovens and pacemakers,
but I had never heard this about magnets. Does anyone know if this
is true?

His doctor will give any necessary warnings.

Since when do amplifiers have "large magets" in them?

The stray field from an electrodynamic speaker is weak, and is highly
unlikely to affect anything at "normal" distances.

William Sommerwerck wrote:
Since when do amplifiers have "large magets" in them?

Mine has a large cat on it.

The stray field from an electrodynamic speaker is weak, and is highly
unlikely to affect anything at "normal" distances.

Depends on the speaker. Some have enough leakage to screw CRTs up.
Admittedly this only takes a few tens of milligauss.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...
William Sommerwerck wrote:
Since when do amplifiers have "large magets" in them?

Mine has a large cat on it.

The stray field from an electrodynamic speaker is weak, and is highly
unlikely to affect anything at "normal" distances.

Depends on the speaker. Some have enough leakage to screw CRTs up.

Even the earth's magetic field screws up a CRT image, that why there's a
demagnitizer in every CRT unit. The fieldstrength of the earth is rougly 0.3
gauss, depending on the location.

The strength of magnets used to "switch" a medical implant (drain valves,
pacemakers) are comparable to the magnets used in speakers, so in order to
disurb anything, you would really have to dismantle the speakers magnet and
hug it.

Meindert

Meindert Sprang wrote:
"Scott Dorsey" wrote in message

The strength of magnets used to "switch" a medical implant (drain valves,
pacemakers) are comparable to the magnets used in speakers, so in order to
disurb anything, you would really have to dismantle the speakers magnet and
hug it.

I'm thinking just hugging the magnet assembly against your chest. Which is
something I have often done while changing drivers on suspended speakers...

It's not the most likely scenario, but I could see it being possible with
an open-backed guitar cabinet if you don't know to avoid it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."