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Old 23rd July 2004, 09:38 PM   #21
Svante is offline Svante  Sweden
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Quote:
Originally posted by jneutron


I wasn't sure what he was saying...

A zero ohm VC certainly will not dissipate, but most certainly can transfer power, from the current entering it, to the field it will generate. And it will move in such a way as to try to lower the current flowing in it, that movement is the back emf..

The superconducting VC would certainly be a neat thing...the upper power limit on all vc's is how strong the epoxy (or polyimide) is at high temperatures, eg: the Glass transition temperature of the epoxy. And the supers I deal with handle 1000 to 3000 amps per square mm..

Cheers, John

Right. However, we'd have to rethink a great deal of the way an electrodynamic loudspeaker works. For example, what would Qes be for a loudspeaker with zero Re? (Hint: The resistance seen from the mechanical side is (Bl)^2/Re). Doable, yes, but a new way of thinking.
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Old 23rd July 2004, 09:43 PM   #22
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Jeez, I wish I had some T/S or other reference material handy, but I don’t, so here is a thought thread between bites of my lunch…

It seems Re adds only ‘real’ resistance to the otherwise complex impedance (mechanical and electrical) of the driver. While this does serve to control damping and Q, it is a purely lossy (wasteful) component. If Re were near zero ohms you would certainly want to block DC from getting to the driver – same as you would with a power transformer. But wouldn’t any signal above, say, 10Hz still have the same ol’ impedance to work with, only with less pure resistance (i.e., be more reactive)?

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Old 23rd July 2004, 09:53 PM   #23
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Quote:
Originally posted by jneutron


I'm all bummed out now.

I went to their site...they state a ceramic coated voice coil assembly...no details....aaaawwwrrrrrr!!!!!!

Copper melts at 1062 C..copper oxide at 1060 C...How in the world do they ceramic coat a voice coil without melting the copper?? hmmmm..

I bet their using the ceramic co-fire insulation scheme CTD developed for use in niobium tin wind and react superconducting magnets needing radiation resistance......they only have to go to 750 to 800C. A little bit of s-glass reinforcement, and voila!!

It gets really easy to cool a voice coil that's running 500 to 600 C...but it must be "heck" on the wire resistivity...

Cheers, John
PS..thanks for the tip..
Chemical vapor deposition doesn't have to be at very high temperatures.
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Old 23rd July 2004, 10:29 PM   #24
drewd is offline drewd  United States
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Quote:
Originally posted by markp
Wouldn't it be very little voltage and a truck load of current?
Theoretically? Zero volts and infinite current. POW!

Assuming that the amp's output impedance is zero. After all, it's all theoretical!

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Old 23rd July 2004, 10:31 PM   #25
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Quote:
Originally posted by Svante

Right. However, we'd have to rethink a great deal of the way an electrodynamic loudspeaker works. For example, what would Qes be for a loudspeaker with zero Re? (Hint: The resistance seen from the mechanical side is (Bl)^2/Re). Doable, yes, but a new way of thinking.

Indeed,

A speaker is a resonating mass-spring system. To tame that you NEED proper damping and damping is nothing else than dissipating energy somewhere. A small part is dissipated as mechanical loss but the majority is dissipated in the voice coil resistance.

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Old 23rd July 2004, 11:00 PM   #26
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Quote:
Originally posted by 454Casull

Chemical vapor deposition doesn't have to be at very high temperatures.
Sorry, "plasma" CVD is at lower temps.
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Old 24th July 2004, 01:48 AM   #27
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No electrical engineer here. Just a hobbyist. But I am going to take a stab at this.

In Ronald Wagner's book on Electrostatic Loudspeakers, he says it is very hard to get work out of a capacitance. However, the speaker moving against the air load converts the reactance to a resistance. So the electrostatic loudspeaker can do work, in fact it can be very efficient.

Wouldn't the same principle work with an electrodynamic loudspeaker, which has inductive reactance instead of capactive reactance? Wouldn't the radiation resistance of the cone be a key factor?
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Old 24th July 2004, 06:25 AM   #28
moamps is offline moamps  Croatia
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Quote:
Wouldn't the same principle work with an electrodynamic loudspeaker, which has inductive reactance instead of capactive reactance? Wouldn't the radiation resistance of the cone be a key factor? [/B]
Ribbon (magnetostatic) speaker?

or something like this

http://www.hobbyhifi.de/SLMS/Die_Story/die_story.html

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Milan
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Old 25th July 2004, 06:09 AM   #29
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Smile Let me explain my question clearly

Hi,
My question seems to be lost somewhere in the thread.
Here is why I posted the question.
I was wondering if we could lower the DC resistance of the coil (for practical reasons we could gold-plate it) to a very low value. From whatever I read, the DC resistance produces heat (I^2R). This heat is simply lost and there are then attempts to manage the heat by the driver manufacturer.

As told in some previous posts to my question, it is certainly not correct to say that the amplifier sees a zero resistance with this kind of driver b'coz the amplifier actually sees the driver load as an inductor and so sees the impedance of the driver. This impedance although depends on the inductance of the coil but is never zero and so the amp could stay happy with this kainda load.

Obviously there are problems with this approach else others would have done it. I would like to understand the problems and explore the possibility of overcoming them. Hope someone can explain why this is not possible.
Thanks in advance.
Goldy
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Old 25th July 2004, 10:53 AM   #30
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Default Re: Let me explain my question clearly

Quote:
Originally posted by goldyrathore
Hi,
My question seems to be lost somewhere in the thread.
Here is why I posted the question.
I was wondering if we could lower the DC resistance of the coil (for practical reasons we could gold-plate it) to a very low value. From whatever I read, the DC resistance produces heat (I^2R). This heat is simply lost and there are then attempts to manage the heat by the driver manufacturer.

As told in some previous posts to my question, it is certainly not correct to say that the amplifier sees a zero resistance with this kind of driver b'coz the amplifier actually sees the driver load as an inductor and so sees the impedance of the driver. This impedance although depends on the inductance of the coil but is never zero and so the amp could stay happy with this kainda load.

Obviously there are problems with this approach else others would have done it. I would like to understand the problems and explore the possibility of overcoming them. Hope someone can explain why this is not possible.
Thanks in advance.
Goldy
I understand what you are saying.

I have had this type of discussion before and it was geared towards thermal heat energy that is a by product of high power and DC resistance, coating the voice coil in gold sounds like a nice idea, forget about the cost and the weight but its not.
The best Voice coil i have ever seen in my life was a Silver voice coil, i believe its the best material for a voice but it is very expensive, and tarnishes very easily, so special care is needed.
Carbon-Graphite could be used in the future?
The problem is drive unit tecnology is very old and has not changed in the last 100 years for all intense purposes.
Its good,but has its limitation,and this is one of them.
You could post this thread in the Amplifiers section and get some interesting post?
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