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Old 23rd July 2004, 07:15 PM   #11
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Quote:
Originally posted by Eli Duttman
Time out guys. Current and voltage are vector quantities, having both direction and magnitude. Power is the dot (scalar) product of the 2 vectors. The dot product of 2 vectors is obtained by multiplying the 2 magnitudes and the cosine of the angle between the 2 vectors (phase angle).

In an idealized circuit that has only reactance, the phase angle is 90 degrees. Cosine 90 degrees = 0; therefore, the power dissipated is 0.

In an idealized circuit that has only resistance, the phase angle is 0 degrees. Cosine 0 degrees =1; therefore, the power dissipated = IV = I^2R.
Hi Eli.

While I agree with your math..I was wondering what question you were answering..

John
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Old 23rd July 2004, 07:41 PM   #12
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I think he was trying to say that if you have pure impedance with no resistance then you cannot dissipate any power.

But this was (maybe unknowingly) what the original poster was getting at... we don't want to disspate any power, just stick loads of volts across the winding to get a nice big fat magnetic field.
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Old 23rd July 2004, 07:43 PM   #13
RHosch is offline RHosch  United States
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Old 23rd July 2004, 07:47 PM   #14
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Quote:
Originally posted by Mr Teal
The car audio company Phoenix Gold used to manufacture a very unique subwoofer call the Cyclone that used a fixed coil and a rotating magnet structure. It didn't produce much upper subbass (I know it's a contridiction ), but it only required 150W and produce HUGE levels of 10-30Hz for the time.

The Cyclone
I remember that unit, it looked like a big plastic tub! with a big dirty black fan in it right?

Yes thats what am thinking of too!
But i am talking about new materials that can hold more magnetic power and this way we can have much more power running through the fixed coil! somebody will have to make it one day, its like the Magnetic motors that have no bushes! much better!
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Old 23rd July 2004, 07:57 PM   #15
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Quote:
Originally posted by richie00boy
I think he was trying to say that if you have pure impedance with no resistance then you cannot dissipate any power.

But this was (maybe unknowingly) what the original poster was getting at... we don't want to disspate any power, just stick loads of volts across the winding to get a nice big fat magnetic field.
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
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Old 23rd July 2004, 08:21 PM   #16
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Quote:
Originally posted by jneutron

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
I think Pioneer used a ceramic coating on there new mega watt subwoofer, very clever and very expensive! you are right but the voice coil is the only thing that fails before a drive unit dies.
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Old 23rd July 2004, 08:33 PM   #17
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Quote:
Originally posted by Paradise_Ice


I think Pioneer used a ceramic coating on there new mega watt subwoofer, very clever and very expensive! you are right but the voice coil is the only thing that fails before a drive unit dies.
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..
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Old 23rd July 2004, 09:06 PM   #18
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I've a question for the driver experts. How much of the net impedance of a voice coil is electrical resistance? A speaker is a transducer that converts electrical work (energy) into mechanical work (energy). The heating in the suspension system elastomers is the mechanical equivalent of electrical resistance. Speakers, like EVERYTHING else, are subject to the 1st Law of Thermodynamics. The change in energy of any given system is equal to the heat added less the work performed.
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Old 23rd July 2004, 09:21 PM   #19
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All this superconducting thermodynamic stuff is nice but what kind of amp are you going to drive it with? The reason most home speakers are 8 ohms is because that is an easy load for an amp to drive. Make the load a fraction of an ohm and the current will be beyond the limits of the amp trying to drive it.
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Old 23rd July 2004, 09:24 PM   #20
markp is offline markp  United States
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Quote:
Originally posted by richie00boy
I think he was trying to say that if you have pure impedance with no resistance then you cannot dissipate any power.

But this was (maybe unknowingly) what the original poster was getting at... we don't want to disspate any power, just stick loads of volts across the winding to get a nice big fat magnetic field.
Wouldn't it be very little voltage and a truck load of current?
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