Why sigh? Anyone can see that you walk the walk. You are the real deal 😀
I'm looking at your ground loop stuff in the gallery right now! THANKS for posting that stuff
Last edited:
Because back in my AA days I was young and stupid.
I'm much older now.😉
Jn
Ps. The coil inductance/resistance graphs are actually related to the current voice coil stuff we've been discussing here.
Last edited:
😀 Smarter in the upstairs as the bones creak and the joints ache more. That's life.
Please, gentlemen, can't you stop those playground brawls ?
Have a little more respect for what J.C gave to the audio industry and his age ?
I'm sure that if you met him, you'd say, just like all well-behaved people: "I'm proud to meet such a famous and talented designer." looking with indulgence at the little eccentricities that tend, in everyone, to appear with age. As well as the tendency to llive more and more in the past with our memories.
And you John, really, you should encourage J.N. rather than feel deprived of something. The horse he beats is alive and crafty. Despite his age (that of the horse ;-).
For once we look here on this topic at a subject which is the weak point of the current audio: the speakers ...
If it can lead to simple solutions to improve, at least a little, the reproduction, it can only give us desire and curiosity. And that does not take away an ounce to your own glory.
All the ways to reduce distortions (and that applies as well to compression drivers, my favorite speakers too) are welcomed. Just wait to see where it will lead.
PS: Happy to see a collaborative work starting here. A miracle ;-)
Have a little more respect for what J.C gave to the audio industry and his age ?
I'm sure that if you met him, you'd say, just like all well-behaved people: "I'm proud to meet such a famous and talented designer." looking with indulgence at the little eccentricities that tend, in everyone, to appear with age. As well as the tendency to llive more and more in the past with our memories.
And you John, really, you should encourage J.N. rather than feel deprived of something. The horse he beats is alive and crafty. Despite his age (that of the horse ;-).
For once we look here on this topic at a subject which is the weak point of the current audio: the speakers ...
If it can lead to simple solutions to improve, at least a little, the reproduction, it can only give us desire and curiosity. And that does not take away an ounce to your own glory.
All the ways to reduce distortions (and that applies as well to compression drivers, my favorite speakers too) are welcomed. Just wait to see where it will lead.
PS: Happy to see a collaborative work starting here. A miracle ;-)
This approach (emphasizing "subtle sound differences") leads to differing personal preferences, or group preferences. "Group preferences" I mean that group of people who mostly listen to audiophile jazz will almost certainly have different preferences than a group of people who mostly listen to acoustical classical music, philharmonic orchestra, chamber orchestra. Looking at MET 7 plots (that you like) I may say with 99.9% probability that I would not like it and would find it colorizing. I do not like oboe sounding like English horn 😀 (even if maybe like audiophile English horn). I know that many people would not care and would not recognize which is which.
Last edited:
Personally I am hoping jneutron will construct his eddy machine and give data on force vs velocity of the disc.
Well, I was wrong again. That plot is wrong, with the loss model fixed the result is the same, just minus infinite DC drift. And the zero crossings don't matter. I think it's important to note that as the eddy voltage is EMF=I*v, then there MUST be DC currents in the pole piece. What was wrong was the continual rise in DC current, it is there but it levels off.
Still no way to generate 3rd harmonics magnetically. 🙁
Well, I was wrong again. That plot is wrong, with the loss model fixed the result is the same, just minus infinite DC drift. And the zero crossings don't matter. I think it's important to note that as the eddy voltage is EMF=I*v, then there MUST be DC currents in the pole piece. What was wrong was the continual rise in DC current, it is there but it levels off.
Still no way to generate 3rd harmonics magnetically. 🙁
Um Ed..you outfit stadiums. Your loudspeakers are larger than anybody's.😀
True. For the most part, the FEA is consistently DC, with some pseudo AC stuck in.
To actually model a speaker magnetic assembly with voice coil through audio power requires on heck of a package. Tha kind of analysis is no small feat, and takes huge computing horsepower.
All,
I just realized that for all the literature I have read out there, there is lots of talk of Le(x) gradient, as well as shorting rings to linearize it. But the real question I have to ask, is..what frequency is used to measure inductance, and why no mention of resistive dissipation? Whenever I measure an inductor, I always without exception, measure Ls and Rs from 20 hz to 20khz, unless the iron laminations are too thick rending 20k useless.
Linearizing with a shorting ring has to be frequency sensitive, but I've seen no data.
As to John Meyer, a google scholar search turned up zero technical papers but plenty of patents. Has he written any technical papers on magnetic linearization?
Jn
AFAIK Le value depends on frequency, so we cannot answer this.
https://www.klippel.de/fileadmin/kl...iterature/Papers/Voice_Coil_ Impedance_04.pdf
Thanks.
It's good that he tested with ring out front and ring in back.
Still, variations between what his model predicts and what is measured varied hugely, 30 to 50% for seconds or thirds.
I note he also mentions the vc and stranded wire. I assume he meant that the vc was individual turns of solid wire, not that stranded wire was used.
A very good paper on testing, but it still errs in accuracy of prediction.
I also do not recall any mention of an aluminum former, eddy dragging of that, flux modulation of gap field, nor any mention of proximity effect on the moving conductors.
So, plenty of more work to do..
Jn
Personally, I hope Jneutron doesn't lose a finger trying to assemble those stupid neo magnets. Unbelievable forces, even between just two. This is how fingertips are lost.
Jn
I purchased some 2” cube neos for fun some years ago. One of my fingers didn’t like the fun.😡
As John said, forget the air. Electrical eddies feed you with enough puzzle already.
Tell me if you have any objections with my interpretation 😀
Coil’s magnetic field –called the primary magnetic field- induces EMF into the surrounding metal structure (front plate and center pole). This induced EMF depends on
- density of magnetic field lines (magnetic flux Φ) entering the metal structure (function of coil current magnitude, coil size, number of turns, distance from coil and magnetic permeability of the metal)
AND
- magnetic flux change (ΔΦ) .
ΔΦ can be due to (either of, or both)
- rate of change of coil’s current (dΦ/dt, aka transformer EMF) that is current’s frequency and/or wave-shape dependent.
- velocity of coil past magnet structure (aka motional EMF)
This induced EMF will generate electrical currents into the metal structure.
As the magnitude of the induced EMF is a local phenomenon, so are the generated electrical currents.
Named as eddy currents, are currents circulating around the local primary magnetic field (conceptually, around each magnetic field line of it), running on planes normal to the local magnetic field lines.
The intensity of these electrical currents depends on the magnitude of the EMF that gave birth to them and the electrical resistance of the path in which they flow in the metal .
These are the initial eddy currents. They produce a magnetic field around them (called secondary magnetic field) which tends to cancel the primary magnetic field.
Now the flow of each local initial eddy current will affect and be affected by all the neighboring local eddy currents. Where the loops are running in the same direction, their resultant are circulating currents like those around the center pole piece and the inner diameter of the front plate. Where the loops are running in the opposite direction they tend to cancel each other like around the squeezed paths within thin laminated plates. Where the loops are running in an intermediate different direction, they interact by forming elliptical paths (all these in 3D).
Secondary eddy currents are generated in the metal between locations with different magnitudes of initially induced EMF, that is, between locations where stronger and weaker local eddy currents circulate. The resultant eddy current paths are been affected further.
The resulting secondary magnetic fields further complicate the situation as they too tend to interact with each other constructively or destructively causing shielding against the initially induced EMF (exponential spread of the eddy currents with distance from the generating magnetic field but linear time lag), skin effect, proximity effect.
It doesn't when considering it’s effect on reluctance of the magnetic circuit. But for the sake of minimizing eddy currents and their effects, the steel at the vicinity of the gap should work into deep magnetic saturation, for it’s μr to be forced close to 1 steadily (regardless of the demagnetizing field of the voice coil)
You may read these for help (and a lot of good equations).
Sensors | Free Full-Text | Non-Destructive Techniques Based on Eddy Current Testing | HTML
http://www.gruppofrattura.it/pdf/rivista/numero39/numero_39_art_26.pdf
http://www.jpier.org/PIERM/pierm65/16.18011904.pdf
In this reference you’ll see how much and in which way the frequency profile (fundamental and harmonics) changes by minute variations of carbon (along the depth from the surface during solidification) in metallurgical controlled investigations using eddy current
https://dibujotecnicoutepsa.files.w...ing-for-evaluation-of-steel-decarburizing.pdf
George
George, couldn't have said it better myself.
No, really, I couldn't have said better. Wish I had... 😀
Jn
Edit: I love the first article...scientists can find the cracks.....
No, technicians can. Scientists develop the method, techs use it in the field.😀
In the second..whenever I see all four maxwells equations in that format, all I can think of is that t-shirt, "God said" at top, "and then there was light" at the bottom.😀
Note they wrote their own modeling code.
Third article, closer to coil over pole piece, note also they had to write their own FEA code to do the analysis..
They were using Roxio and Opera at work for this kind of stuff, would take days on a quad core PC. I'm sure it's faster now, but then again, code bloat is always a killer.
Nice links George.
No, really, I couldn't have said better. Wish I had... 😀
Jn
Edit: I love the first article...scientists can find the cracks.....
No, technicians can. Scientists develop the method, techs use it in the field.😀
In the second..whenever I see all four maxwells equations in that format, all I can think of is that t-shirt, "God said" at top, "and then there was light" at the bottom.😀
Note they wrote their own modeling code.
Third article, closer to coil over pole piece, note also they had to write their own FEA code to do the analysis..
They were using Roxio and Opera at work for this kind of stuff, would take days on a quad core PC. I'm sure it's faster now, but then again, code bloat is always a killer.
Nice links George.
Last edited:
It's good that you are kind with me.
I can go to sleep now (before you read it for a second time and change your mind) 🙂
George
I can go to sleep now (before you read it for a second time and change your mind) 🙂
George
Me? Nah.
Just sitting here following doctors orders. Drink plenty of clear liquids and eating plenty of greens.
Drowning fruit as it were. Wait, are olives fruit? Or are they legumes. Or, seeds? Or vegetables..ah, doesn't matter. The pimento will probably kill me anyway..
Sigh.
Jn
Last edited:
- Status
- Not open for further replies.