Is there any way to magnetically shield a speaker?

[MOSFET]

Again, this doesn't have much to do with car audio, but I know there are
some REAL knowledgeable folks here.

For years I have been using a center channel that was not really designed as
a center channel, but it's timber matches PERFECTLY my main speakers, a pair
of Michael Green Designs. Anyway, I am rearranging my home-theater and want
to put my center channel next to my TV (it was sitting on a shelf on the
wall up high behind the TV so no problems were created). But obviously if I
wish to put the speaker on top of my TV, the magnetic field will create
havoc with my picture tube. The speaker I want to do this with has two 5"
drivers and one 1" tweeter in the middle (it actually LOOKS like a center
channel speaker). I know that typical magnetically shielded speakers have
something that encases the magnet. Is this possible? Any other thoughts?

Thanks in advance.

[John Durbin]

Normal shielding techniques are adding a bucking magnet (additional
magnet glued to the backplate in reverse magnetic polarity so it helps
cancel the external magnetic field of the existing magnet structure)
followed by a steel can that is glued over the top of the bucking magnet
& motor assembly.

JD

MOSFET wrote:
> Again, this doesn't have much to do with car audio, but I know there are
> some REAL knowledgeable folks here.
>
> For years I have been using a center channel that was not really designed as
> a center channel, but it's timber matches PERFECTLY my main speakers, a pair
> of Michael Green Designs. Anyway, I am rearranging my home-theater and want
> to put my center channel next to my TV (it was sitting on a shelf on the
> wall up high behind the TV so no problems were created). But obviously if I
> wish to put the speaker on top of my TV, the magnetic field will create
> havoc with my picture tube. The speaker I want to do this with has two 5"
> drivers and one 1" tweeter in the middle (it actually LOOKS like a center
> channel speaker). I know that typical magnetically shielded speakers have
> something that encases the magnet. Is this possible? Any other thoughts?
>
> Thanks in advance.
>
>

[RG]

John is right .... and Madisound is one source that can supply bucking
magnets and covers.

-RG


"MOSFET" > wrote in message
m...
> Again, this doesn't have much to do with car audio, but I know there are
> some REAL knowledgeable folks here.
>
> For years I have been using a center channel that was not really designed
> as a center channel, but it's timber matches PERFECTLY my main speakers, a
> pair of Michael Green Designs. Anyway, I am rearranging my home-theater
> and want to put my center channel next to my TV (it was sitting on a shelf
> on the wall up high behind the TV so no problems were created). But
> obviously if I wish to put the speaker on top of my TV, the magnetic field
> will create havoc with my picture tube. The speaker I want to do this with
> has two 5" drivers and one 1" tweeter in the middle (it actually LOOKS
> like a center channel speaker). I know that typical magnetically
> shielded speakers have something that encases the magnet. Is this
> possible? Any other thoughts?
>
> Thanks in advance.
>

[JimJ[VT]]

Edit - already perfectly answered :)


--
JimJ[VT]

[MOSFET]

> Loose the CRT, get an LCD or Plasma :) :) :)
>
Not to get off on a completely different subject....

I would LOVE to have a large screen LCD, they ROCK!!! But frankly, my
top-off-the-line Philips 34" widescreen (the 34PW9846) looks sharper and
brighter than any plasma I have seen. I KNOW they are getting better all
the time, and perhaps now there are units that do rival my CRT, but for now,
I'll stick with my 34", thank you very much!

But I agree, LCD's are superior. I would LOVE to have a 42" LCD HDTV.

MOSFET

[Cyrus]

In article >,
"MOSFET" > wrote:

> > Loose the CRT, get an LCD or Plasma :) :) :)
> >
> Not to get off on a completely different subject....
>
> I would LOVE to have a large screen LCD, they ROCK!!! But frankly, my
> top-off-the-line Philips 34" widescreen (the 34PW9846) looks sharper and
> brighter than any plasma I have seen. I KNOW they are getting better all
> the time, and perhaps now there are units that do rival my CRT, but for now,
> I'll stick with my 34", thank you very much!
>
> But I agree, LCD's are superior. I would LOVE to have a 42" LCD HDTV.
>
> MOSFET
>
>

Of the LCD's I've watched, the trails are hideous. Leaves me feeling
dizzy after watching.

--
Cyrus

*coughcasaucedoprodigynetcough*

[Matt Ion]

MOSFET wrote:
>>Loose the CRT, get an LCD or Plasma :) :) :)
>>
>
> Not to get off on a completely different subject....
>
> I would LOVE to have a large screen LCD, they ROCK!!! But frankly, my
> top-off-the-line Philips 34" widescreen (the 34PW9846) looks sharper and
> brighter than any plasma I have seen. I KNOW they are getting better all
> the time, and perhaps now there are units that do rival my CRT, but for now,
> I'll stick with my 34", thank you very much!
>
> But I agree, LCD's are superior. I would LOVE to have a 42" LCD HDTV.

Actually, I'm looking forward to SED technology hitting the broad market:

http://www.hdtvsolutions.com/sed_tvs.htm


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[GregS]

In article >, "MOSFET" > wrote:
>Again, this doesn't have much to do with car audio, but I know there are
>some REAL knowledgeable folks here.
>
>For years I have been using a center channel that was not really designed as
>a center channel, but it's timber matches PERFECTLY my main speakers, a pair
>of Michael Green Designs. Anyway, I am rearranging my home-theater and want
>to put my center channel next to my TV (it was sitting on a shelf on the
>wall up high behind the TV so no problems were created). But obviously if I
>wish to put the speaker on top of my TV, the magnetic field will create
>havoc with my picture tube. The speaker I want to do this with has two 5"
>drivers and one 1" tweeter in the middle (it actually LOOKS like a center
>channel speaker). I know that typical magnetically shielded speakers have
>something that encases the magnet. Is this possible? Any other thoughts?

When you change the magnetism, the sound will also change. The
Qts of the drivers and sensitivity change.

greg

[John Durbin]

The bucking magnet & shield impact EXTERNAL magnetic flux, not
internal... the motor works the same.

JD

GregS wrote:
> In article >, "MOSFET" > wrote:
>
>>Again, this doesn't have much to do with car audio, but I know there are
>>some REAL knowledgeable folks here.
>>
>>For years I have been using a center channel that was not really designed as
>>a center channel, but it's timber matches PERFECTLY my main speakers, a pair
>>of Michael Green Designs. Anyway, I am rearranging my home-theater and want
>>to put my center channel next to my TV (it was sitting on a shelf on the
>>wall up high behind the TV so no problems were created). But obviously if I
>>wish to put the speaker on top of my TV, the magnetic field will create
>>havoc with my picture tube. The speaker I want to do this with has two 5"
>>drivers and one 1" tweeter in the middle (it actually LOOKS like a center
>>channel speaker). I know that typical magnetically shielded speakers have
>>something that encases the magnet. Is this possible? Any other thoughts?
>
>
> When you change the magnetism, the sound will also change. The
> Qts of the drivers and sensitivity change.
>
> greg

[GregS]

In article >, John Durbin > wrote:
>The bucking magnet & shield impact EXTERNAL magnetic flux, not
>internal... the motor works the same.


Any change in the external will affect the internal I'm sure. The magnet is a complete unit, not
just one area, but you can concentrate flux. You can buck or you can also
add to the magnetism, when the magnets repel. I might have this backwards. A bucking magnet will
attract.The magnetism will affect the Qes directly.

greg

>JD
>
>GregS wrote:
>> In article >, "MOSFET"
> > wrote:
>>
>>>Again, this doesn't have much to do with car audio, but I know there are
>>>some REAL knowledgeable folks here.
>>>
>>>For years I have been using a center channel that was not really designed as
>>>a center channel, but it's timber matches PERFECTLY my main speakers, a pair
>>>of Michael Green Designs. Anyway, I am rearranging my home-theater and want
>>>to put my center channel next to my TV (it was sitting on a shelf on the
>>>wall up high behind the TV so no problems were created). But obviously if I
>>>wish to put the speaker on top of my TV, the magnetic field will create
>>>havoc with my picture tube. The speaker I want to do this with has two 5"
>>>drivers and one 1" tweeter in the middle (it actually LOOKS like a center
>>>channel speaker). I know that typical magnetically shielded speakers have
>>>something that encases the magnet. Is this possible? Any other thoughts?
>>
>>
>> When you change the magnetism, the sound will also change. The
>> Qts of the drivers and sensitivity change.
>>
>> greg
>

[GregS]

In article >, John Durbin > wrote:
>The bucking magnet & shield impact EXTERNAL magnetic flux, not
>internal... the motor works the same.

Oh, I just wanted to add, a driver is best built from the getgo as far as flux leakage
goes, as told by R. Pierce on many occasions.

greg

>
>GregS wrote:
>> In article >, "MOSFET"
> > wrote:
>>
>>>Again, this doesn't have much to do with car audio, but I know there are
>>>some REAL knowledgeable folks here.
>>>
>>>For years I have been using a center channel that was not really designed as
>>>a center channel, but it's timber matches PERFECTLY my main speakers, a pair
>>>of Michael Green Designs. Anyway, I am rearranging my home-theater and want
>>>to put my center channel next to my TV (it was sitting on a shelf on the
>>>wall up high behind the TV so no problems were created). But obviously if I
>>>wish to put the speaker on top of my TV, the magnetic field will create
>>>havoc with my picture tube. The speaker I want to do this with has two 5"
>>>drivers and one 1" tweeter in the middle (it actually LOOKS like a center
>>>channel speaker). I know that typical magnetically shielded speakers have
>>>something that encases the magnet. Is this possible? Any other thoughts?
>>
>>
>> When you change the magnetism, the sound will also change. The
>> Qts of the drivers and sensitivity change.
>>
>> greg
>

[John Durbin]

I stand corrected... but the change is small & predictable so easily
taken into account when designing the driver in the first place. But,
adding the bucking magnet to a driver not originally designed for it you
could change the sound enough to be audible. Typical changes are lower
Qes and therefore Qts, and a slight increase in efficiency.

JD

GregS wrote:

> In article >, John Durbin > wrote:
>
>>The bucking magnet & shield impact EXTERNAL magnetic flux, not
>>internal... the motor works the same.
>
>
>
> Any change in the external will affect the internal I'm sure. The magnet is a complete unit, not
> just one area, but you can concentrate flux. You can buck or you can also
> add to the magnetism, when the magnets repel. I might have this backwards. A bucking magnet will
> attract.The magnetism will affect the Qes directly.
>
> greg
>
>
>>JD
>>
>>GregS wrote:
>>
>>>In article >, "MOSFET"
>>
> wrote:
>>
>>>>Again, this doesn't have much to do with car audio, but I know there are
>>>>some REAL knowledgeable folks here.
>>>>
>>>>For years I have been using a center channel that was not really designed as
>>>>a center channel, but it's timber matches PERFECTLY my main speakers, a pair
>>>>of Michael Green Designs. Anyway, I am rearranging my home-theater and want
>>>>to put my center channel next to my TV (it was sitting on a shelf on the
>>>>wall up high behind the TV so no problems were created). But obviously if I
>>>>wish to put the speaker on top of my TV, the magnetic field will create
>>>>havoc with my picture tube. The speaker I want to do this with has two 5"
>>>>drivers and one 1" tweeter in the middle (it actually LOOKS like a center
>>>>channel speaker). I know that typical magnetically shielded speakers have
>>>>something that encases the magnet. Is this possible? Any other thoughts?
>>>
>>>
>>>When you change the magnetism, the sound will also change. The
>>>Qts of the drivers and sensitivity change.
>>>
>>>greg
>>

[Brandonb]

Question as I know jack squat about loudspeaker design: why don't
loudspeaker manufacturers then automatically make shielded speakers for
car audio? Couldn't the magnetic fields potentially affect in-car
electronics (like the vehicle's computer)? I would think any increase in
efficiency would be a bonus also, even if very slight. I know many
manufacturers already market "double-stacked" and "triple-stacked"
magnets. Is there a lowered power handling with adding a bucking magnet?

Brandonb


John Durbin wrote:
> I stand corrected... but the change is small & predictable so easily
> taken into account when designing the driver in the first place. But,
> adding the bucking magnet to a driver not originally designed for it you
> could change the sound enough to be audible. Typical changes are lower
> Qes and therefore Qts, and a slight increase in efficiency.
>
> JD

[Matt Ion]

Brandonb wrote:
> Question as I know jack squat about loudspeaker design: why don't
> loudspeaker manufacturers then automatically make shielded speakers for
> car audio?

Not necessary.

> Couldn't the magnetic fields potentially affect in-car
> electronics (like the vehicle's computer)?

No.


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[John Durbin]

Neodymium designs where the magnet is inside the voice coil have a
greatly reduced fringe field, as a bonus... but really not an issue as
Brandon wrote.

JD

Matt Ion wrote:
> Brandonb wrote:
>
>> Question as I know jack squat about loudspeaker design: why don't
>> loudspeaker manufacturers then automatically make shielded speakers
>> for car audio?
>
>
> Not necessary.
>
>> Couldn't the magnetic fields potentially affect in-car electronics
>> (like the vehicle's computer)?
>
>
> No.
>
>
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