What would room temperature superconductivity do for audio?

[IAtaman]

The amp/speaker system would have to be current drive. The load would not be fully inductive, any sound power the driver delivers would be seen as a resistive load. They could be light and efficient.

I did not understand the bold part, how would that work?

 

[Cbdb2]

The SPL (sound in the air) comes from the power into the driver, the amp sees this load as a resistance, its real power, not reactive.

 

[Cbdb2]

Oh interesting. Does that mean the field strength of the magnets is a limiting factor in drivers?

If by factor you mean for power output, its only one. Properly engineered speakers should be designed so all the limiting factors kick in at the same power level, ie 100 watts. You don't let one limiting factor kick in at 10 watts if all the others are 100. And you don't put in a magnet that will work to 1000 watts.
With superconducting coils the weight of the magnets (90% of the driver weight) would be negligible.

 

[kemmler3D]

If by factor you mean for power output, its only one. Properly engineered speakers should be designed so all the limiting factors kick in at the same power level, ie 100 watts. You don't let one limiting factor kick in at 10 watts if all the others are 100. And you don't put in a magnet that will work to 1000 watts.
With superconducting coils the weight of the magnets (90% of the driver weight) would be negligible.

Very cool, and sorry for the freshman-seminar level questions here - with a given amplifier (let's just assume it's current-drive for now) would a superconducting voice coil create a materially stronger field than a standard copper one?

In my mind, superconducting electromagnets are much stronger than other kinds of magnets for a given size / weight... but I don't know if that's correct or missing important variables or just plain wrong.

But if we also generously assume LK-99 is not only the real deal, but also ends up being cheap and workable into voice coils, I would imagine it would impact speaker drive design quite a bit.

 

[IAtaman]

If by factor you mean for power output, its only one. Properly engineered speakers should be designed so all the limiting factors kick in at the same power level, ie 100 watts. You don't let one limiting factor kick in at 10 watts if all the others are 100. And you don't put in a magnet that will work to 1000 watts.
With superconducting coils the weight of the magnets (90% of the driver weight) would be negligible.

I meant limiting factor for driver sensitivity. From what kemmler3D wrote I thought he meant with stronger magnets we can create more sensitive speakers, which sounded interesting because I thought the biggest problem of sensitivity was impedance matching with air, but maybe it is not and stronger magnets can improve sensitivity?

From what you wrote I got the impression that superconductor magnets can make the drivers significantly lighther. Any other benefits?

 

[kemmler3D]

I meant limiting factor for driver sensitivity. From what kemmler3D wrote I thought he meant with stronger magnets we can create more sensitive speakers, which sounded interesting because I thought the biggest problem of sensitivity was impedance matching with air, but maybe it is not and stronger magnets can improve sensitivity?

From what you wrote I got the impression that superconductor magnets can make the drivers significantly lighther. Any other benefits?

Not an expert on driver parameters, but I think that a stronger magnetic field produces more motion per unit of current in the voice coil, so I guess yes, all else held equal, stronger magnets mean more sensitive drivers.

I guess since we're talking about using electromagnets on both ends in this scenario, the voice coil and stationary magnet could both be large, or even multi-layered (sort of like that KEF sub), which might open up previously unworkable possibilities for driver shape and size.

 

[IAtaman]

Not an expert on driver parameters, but I think that a stronger magnetic field produces more motion per unit of current in the voice coil, so I guess yes, all else held equal, stronger magnets mean more sensitive drivers.

That makes sense. Stronger magnet, stronger movement. But then again aren't much smaller tweeters generally more sensitive than subwoofers with much larger magnets?

 

[LTig]

Very cool, and sorry for the freshman-seminar level questions here - with a given amplifier (let's just assume it's current-drive for now) would a superconducting voice coil create a materially stronger field than a standard copper one?

Yes.

In my mind, superconducting electromagnets are much stronger than other kinds of magnets for a given size / weight... but I don't know if that's correct or missing important variables or just plain wrong.

Indeed. The heat dissipation of standard wires limits the maximum field strength one can reach. It's the reason why magnets for high field NMR use superconducting coils.

But if we also generously assume LK-99 is not only the real deal, but also ends up being cheap and workable into voice coils, I would imagine it would impact speaker drive design quite a bit.

One could create very strong magnets for dynamic speakers which are very light and use no electric power except during the initial charge. Once charged by an external current source to the specified field strength, one closes the coil and detaches the current source. From then on current flows in the coil as long as its wire stays superconductive. Sounds crazy, but its true ... been there, done that, with magnets for NMR instruments. It's probably the technology closest to a perpetuum mobile.

A superconductive voice coil would not heat up because no power is dissipated, so efficiency should be better and power compression reduced.

 

[kemmler3D]

That makes sense. Stronger magnet, stronger movement. But then again aren't much smaller tweeters generally more sensitive than subwoofers with much larger magnets?

This has to do with the frequency range more than anything. Producing high SPL at high frequencies requires disproportionately less power.

A superconductive voice coil would not heat up because no power is dissipated, so efficiency should be better and power compression reduced.

But, there would be some power dissipated in the system because of friction / damping in the motion of the cone, no? But either way it does sound like a superconducting driver could advance the state of the art quite a bit in the right hands.

 

[chelgrian]

The truth is we don't quite know. We haven't played around with superconductivity in practical applications, and in fact several things still seem contradictory in lab experiments. We do however know that superconductivity and magnetism fight each other, which would be a challenge for audio designs.

Superconducting magnets are used in MRI machines as a practical application. Also in particle accelerators, fusion reactor prototypes and even in a maglev train in Japan although due to the requirement to keep the magnets at cryogenic temperatures to keep them superconducting that last one makes no commercial sense.

 

[tmtomh]

All I know is that Audioquest would put them in little transparent containers, strap them to fancy looking interconnects, and sell the new Warp Drive interconnect line for $3500 a pair for a .5 meter length.

 

[Cbdb2]

I meant limiting factor for driver sensitivity. From what kemmler3D wrote I thought he meant with stronger magnets we can create more sensitive speakers, which sounded interesting because I thought the biggest problem of sensitivity was impedance matching with air, but maybe it is not and stronger magnets can improve sensitivity?

From what you wrote I got the impression that superconductor magnets can make the drivers significantly lighther. Any other benefits?

You will gain some efficiency but your right about impedance matching with air. ( why horns are 5 times more efficient). Lighter voice coils are probably the biggest advantage.
Cant see any paradigm shift

 

[pablolie]

Interesting, they now replicated it twice...

Superconductor Breakthrough Findings Replicated, Twice, in Preliminary Testing

A tentative but less nebulous step toward superconductor-fueled electronics.

www.tomshardware.com

 

[tmtomh]

This is beyond my expertise (to say the least!) - but I watched a video by Sabine Hossenfelder Monday (which was recorded on Sunday), and she said she suspected the initial video was showing that the material was diamagnetic, not superconducting.

Can anyone comment on whether these replications of the initial findings have conclusively shown that this is a superconductor - or could these replicated findings potentially just be confirming that this material is diamagnetic?

 

[pablolie]

This is beyond my expertise (to say the least!) - but I watched a video by Sabine Hossenfelder Monday (which was recorded on Sunday), and she said she suspected the initial video was showing that the material was diamagnetic, not superconducting.

Can anyone comment on whether these replications of the initial findings have conclusively shown that this is a superconductor - or could these replicated findings potentially just be confirming that this material is diamagnetic?

I doubt anyone can do that conclusively yet. But, as I mentioned previosuly (and -caveat- this may obsolete my -and many others- assumptions) magnetism and superconductivity in some ways are at odds -they repel each other-, check the Meissner Effect. Which makes superconductors diamagnetic, so it is not a contradiction, from my retired skills in Physics. But you can compartmentalize in designs, as shown in current use cases of superconductors (which someone else pointed out -kudos and sorry I can't check the id and credit as I type this- and separate stuff for results... which conceivably, if this works out, is HUGE and makes it much easier. Current superconductivity stuff requires liquid helium stuff and what not, which is incredibly energy hungry and comes with may limitations for practical use in consumer stuff.

But imagine if this LK99 stuff could be integrated into 3nm semiconductors... imagine a CPU or DSP or Class D that does not even need a cooler. That in itself would be mind-bogglingly disruptive.

 

[RayDunzl]

Interesting, they now replicated it twice...

Superconductor Breakthrough Findings Replicated, Twice, in Preliminary Testing

A tentative but less nebulous step toward superconductor-fueled electronics.

www.tomshardware.com

It was a simulation at LBNL.

"Abstract:
A recent report of room temperature superconductivity at ambient pressure in Cu-substituted apatite (`LK99') has invigorated interest in the understanding of what materials and mechanisms can allow for high-temperature superconductivity. Here I perform density functional theory calculations..."

[2307.16892] Origin of correlated isolated flat bands in copper-substituted lead phosphate apatite

 

[pablolie]

It was a simulation at LBNL.

"Abstract:
A recent report of room temperature superconductivity at ambient pressure in Cu-substituted apatite (`LK99') has invigorated interest in the understanding of what materials and mechanisms can allow for high-temperature superconductivity. Here I perform density functional theory calculations..."

[2307.16892] Origin of correlated isolated flat bands in copper-substituted lead phosphate apatite

Huge question in semiconductors is... can this material be used as a conductor within a semiconductor (we may need a new term if this flies) architecture? I wonder what the lag time between research and application would be in this one. It's not like transistors displaced tubes overnight, right...

 

[tmtomh]

I doubt anyone can do that conclusively yet. But, as I mentioned previosuly (and -caveat- this may obsolete my -and many others- assumptions) magnetism and superconductivity in some ways are at odds -they repel each other-, check the Meissner Effect. Which makes superconductors diamagnetic, so it is not a contradiction, from my retired skills in Physics. But you can compartmentalize in designs, as shown in current use cases of superconductors (which someone else pointed out -kudos and sorry I can't check the id and credit as I type this- and separate stuff for results... which conceivably, if this works out, is HUGE and makes it much easier. Current superconductivity stuff requires liquid helium stuff and what not, which is incredibly energy hungry and comes with may limitations for practical use in consumer stuff.

But imagine if this LK99 stuff could be integrated into 3nm semiconductors... imagine a CPU or DSP or Class D that does not even need a cooler. That in itself would be mind-bogglingly disruptive.

Thanks - I understand that. But my understanding is that while superconductors are diamagnetic, not all diamagnetic materials are superconductors. So I think the question remains whether what's been observed thus far is really the Meissner Effect, or if what we're looking at is a diamagnetic, non-superconducting material.

 

[pablolie]

There are a ton of diamagnetic materials. Copper, water, wood ... long list. If LK99 is both it is incredibly disruptive. Even if it is *just* one or the other at room temp, the superconductive ability is also quite game changing, and mind-blowingly so if usable in semiconductor substrates.

That said, the timeline from where the research is to wide-spread production is unlikely to happen in my professional lifetime (but I'd love it).

 

[tmtomh]

There are a ton of diamagnetic materials. Copper, water, wood ... long list. If LK99 is both it is incredibly disruptive. Even if it is *just* one or the other at room temp, the superconductive ability is also quite game changing, and mind-blowingly so if usable in semiconductor substrates.

That said, the timeline from where the research is to wide-spread production is unlikely to happen in my professional lifetime (but I'd love it).

Again, understood and all reasonable. But I feel like this comment and your previous comment are both sort of leaping over the most important step/question: is LK99 a superconductor or not? We don't know yet, and until we do, I doubt I am alone in not wanting to get excited yet, given the history of previously claimed room-temperature superconductor discoveries (not to mention the somewhat bizarre circumstances of the publication/withdrawal/republication of the preprint that's at the center of all this).