[UnsteadyKen]

As an electrical ignoramus, i have long been puzzled by a throw away
comment often seen in loudspeaker reviews along the lines of...
"the copper plated pole piece acts as a shorted turn", the implication
being that this is a good thing.

Can anyone explain in simple terms why copper plating would have this
effect?
And if it is such a good thing, why don't they just short one of the turns
deliberately?

__
Ken

[Don Pearce]

On Wed, 26 Mar 2008 15:30:34 -0000, UnsteadyKen
wrote:

As an electrical ignoramus, i have long been puzzled by a throw away
comment often seen in loudspeaker reviews along the lines of...
"the copper plated pole piece acts as a shorted turn", the implication
being that this is a good thing.

Can anyone explain in simple terms why copper plating would have this
effect?
And if it is such a good thing, why don't they just short one of the turns
deliberately?

It is a way of controlling the damping of the motion of the cone. The
shorted turn has signal induced into it, and heats up, dissipating
power. By adjusting the thickness of the plating the amount of damping
it provides can be adjusted to achieve some desired value. You
wouldn't want to short one of the actual turns, because that would
cause too much loss of signal power.

d

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

[Arny Krueger]

"UnsteadyKen" wrote in message
m

As an electrical ignoramus, i have long been puzzled by a
throw away comment often seen in loudspeaker reviews
along the lines of... "the copper plated pole piece acts
as a shorted turn", the implication being that this is a
good thing.

The problem being addressed is eddy currents induced into the pole piece by
the voice coil.

This is problematical because the voice coil's relationship with the fixed
pole piece is changing when the speaker is driven. It creates nonlinear
distortion. It makes the performance of the speaker harder to predict.

Can anyone explain in simple terms why copper plating
would have this effect?

The copper plating has lower resistance than the usual iron or steel that is
used to make pole pieces. Sometimes a copper cap or ring is used for the
same purpose. Sometimes aluminum parts are used.

And if it is such a good thing, why don't they just short
one of the turns deliberately?

The shorted turn would be part of the voice coil, not part of the pole
piece. It's the relative motion that causes problems.

[UnsteadyKen]

Don Pearce said...

he
shorted turn has signal induced into it, and heats up, dissipating
power.

Thanks Don. A bit like regenerative braking at the end of the voice
coils travel. Now it makes sense.
--
Ken

[UnsteadyKen]

Arny Krueger said...

The shorted turn would be part of the voice coil, not part of the pole
piece. It's the relative motion that causes problems.

Thank you Arny the light dimly dawns.

--
Ken

[Richard Crowley]

"UnsteadyKen" wrote ...
Arny Krueger said...
The shorted turn would be part of the voice coil, not part of the pole
piece. It's the relative motion that causes problems.

Thank you Arny the light dimly dawns.

Speaking of copper....
http://www.youtube.com/watch?v=cVkZZsS-66c

[Don Pearce]

On Wed, 26 Mar 2008 10:14:52 -0700, "Richard Crowley"
wrote:

"UnsteadyKen" wrote ...
Arny Krueger said...
The shorted turn would be part of the voice coil, not part of the pole
piece. It's the relative motion that causes problems.

Thank you Arny the light dimly dawns.

Speaking of copper....
http://www.youtube.com/watch?v=cVkZZsS-66c



Thank you - that's a keeper.

d

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

[Earl Kiosterud]

"Richard Crowley" wrote in message
...

Speaking of copper....
http://www.youtube.com/watch?v=cVkZZsS-66c



That's a hoot. For anyone who wants the video file, it's on my site at
http://www.smokeylake.com/Fun%20Stuff/Fun_Stuff.htm

It's a 2 MB wmv file.
--
Regards from Virginia Beach,

Earl Kiosterud