We don't 'need' DCR as such, it is just a by-product of winding a coil of sufficient length to achieve a strong enough motor and avoid massive saturation. As such the impedance is related to the DC resistance, and affected throughout the spectrum by induced back-EMF and inductance.
If you just use thicker wire to get the DCR down you add mass which can be undesireable. You would just end up working with massive currents that would be very susceptible to losses.
If you just use thicker wire to get the DCR down you add mass which can be undesireable. You would just end up working with massive currents that would be very susceptible to losses.
Very low impedances means very high currents. It is easier to design an amp that does not need to deliver huge amounts of current as output devices are not designed for that level of current even if the voltage is low. p=iv, so bump up the voltage and lower the current to get the same number of watts. A 4 ohm load is a good medium between current/voltage but lower gets hard to do.
AGGEMAM said:
OH, geeze...you're exaggerating....
Even with a gap strength of 2 tesla, a 13 mil diameter niobium titanium wire will still carry 45 amps at about 10 Kelvin...
And the HTS stuff is useable at 77K....
Hey, liquid nitrogen is dirt cheap...how about a cryogenic diy subwoofer???
Cheers, John
BillFitzmaurice said:
AGGEMAM said:
Bill you have a way with words! very direct and he is right.
AGGEMAN is talking about a Superconductor and dont worry one day you wont have to freeze it to zero kelvin! i hope.
I think we have a superconducting Niobium Wire but i dont know much about its properties or its use as voice coil.
i have looked into making a Titanium voice coil but it would cost me more than £200 to make just the voice coil and former with a Grade 5, 1 mm titanium wire! that is just to much for me to attempt yet.
Once molecular engineering come true in the next 10 or 20 years we will have room temperature superconductors, it will happen not because we need zero inductive coils but zero inductive chips!
I hope somebody can develope a moving magnet cone instead of the moving coil system we have now, who know if it would be better but it would be different thats for sure!
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.
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.
Way back when, before the dynamic loudspeaker was invented, earphones and speakers used a fixed coil wound around a permanent magnet along with a sheet metal diaphragm as the moving entity. That's not moving magnet, but its close relative, moving iron.
For speaker service the dynamic system has proven superior.
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
), but it only required 150W and produce HUGE levels of 10-30Hz for the time.The Cyclone
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.
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.
Mr Teal said: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
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!
richie00boy said:
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
Paradise_Ice said:
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..
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.
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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