Polished vs Un-polished Magnets

[David Schwab]

Since some capacitors have ceramic dielectrics, could there be in theory piezo effects in the ceramic that have an effect on the acoustics, versus say mylar that has none of that effect? Probably belongs in a new thread, just a random thought...

Some ceramics are microphonic.

[Joe Gwinn]

Some ceramics are microphonic.

Never let a moderator have a microphone...

[Mark Hammer]

Just a silly little question. Are the folks who tout the virtues of polished magnets polishing them prior to charging, or after? And does this apply to any alnico 5, whether bar or polepiece, or just to polepieces? If just polepieces, are we talking only standard equal-height polepieces, or staggered as well, or the extry-long polepieces like the Wieder Big-T? Will any effect show up in a Tele bridge PU?

My point is that, in the land of pickup mysteries, just about anything may, on occasion, appear to have a tonal impact. But that impact may require the alignment of many planets to suddenly appear, and not be robust enough to occur in any circumstance. Whether that constitutes something to pay attention to is a whole other matter. For instance, there could be something about the magnets in a Dynasonic that provide a little more bandwidth, but that pickup structure is so distinct from so many other kinds that there is nothing much to generalize beyond that specific niche. It's not completely unimportant, if you're a fan or maker of those pickups, but there isn't much of importance or utility for the rest of us.

[frankfalbo]

Guys, by the jokes and some of the speculation on shining or using "polish" I can't tell if some of you are truly unaware of what the OP is asking, and you're thinking he means to take a magnet and polish it up (of course you'll all deny it later LOL)

Forgive me if some of this sounds condescending on a forum with experienced pickup makers but these threads obviously live on indefinitely and are searched by all types/all levels. I will also start by confirming that I do hear a difference, small enough for most not to care, but big enough we shouldn't be dismissive of those who do care.

This term polished comes from polished vs rough cast, and is generally centered around ONLY humbucker magnets. The better term would be "rough cast oversized, then precision ground down to final size" but that would take too long. Rough cast magnets are cast in an attempt to hit the target size. Then sometimes you'll see a few hits from the grinder here and there where it went over. Often, even a rough cast humbucker magnet is still cast oversized along the critical keeper bar and slug edges. So you'll see those edges clean but the top and bottom are rough. You will see rough cast rod magnets occasionally but that's not typically what is discussed at length by the forum magnet swappers.

Two things occur with rough cast. First, the simple fact that two surfaces have a texture means the field is being dithered. However minutely or inconsequential, a scientist would not consider a variable not to exist, just consider whether its below the threshold of other random differences and/or user perception. But I believe this texture is the main reason they sound different. I could be wrong in that it may also affect how the bar takes the charge. Someone asked "is this before or after charging"; well its a manufacturing process, not a buff on the wheel, so its prior to charging. The charge itself may get a little more wild and random at these nooks and crannies. If so, that would likely level itself out as a slight degauss rather quickly. I haven't measured reduced gauss a the top of the pole with RC vs polished, but that doesn't mean that within the bar magnet there aren't some relaxed areas.

The second thing is that whatever that difference is, it now becomes a bit random. Some rough cast are smaller than others. Some fall away from treble to bass, or from screw to slug. Vice versa if you flip/rotate it of course. It's entirely possible one pickup has softer highs or spongier lows when nothing else has changed. Many would consider random to be bad, and precision to be good. I wouldn't disagree on premise but if you prefer the sound of rough cast magnets, I would equate it to worn-in blue jeans. You may have 5 pairs of various worn-in jeans, of which the fit and degree of wear is random. But you know you'll like ALL of them better than that new crisp pair you just got. So the randomness becomes secondary.

If you want to try to balance consistency with textured surface and rolled edges, you can begin with precision ground magnets and tumble them in media. You'll pick up a bit of randomness, but at least all of your dimensions will have started out precision cut.

[salvarsan]

Much less seriously, but with as much relevance as climate change to the significance of polished magnets, we were constructing mock jeopardy questions.

Agriculture for $600
"What is the estimated daily chicken egg output of any one American state?"

Actresses for $800
"What were Lycia Naff's and Kaitlyn Leeb's most memorable parts?"


-- The ex-immoderator

[Mike Sulzer]

I haven't measured reduced gauss a the top of the pole with RC vs polished...

Yes, I think that is the issue.

It is the field at the strings that counts, if it is the dc field we are talking about. Small scale roughness is just not an issue, directly. (You can look at a magnet as a vast collection of tiny dipoles, each of which has a field that falls off with the cube of distance. A small rearrangement of these dipoles has very little direct effect on the field at the string, especially since the dipoles point in the wrong direction.) The field at the string is provided by the pole piece, as magnetized by the magnet. Small scale effects are pretty much averaged out, but if there is a large void right near where the magnet touches a pole piece, that pole piece might not get magnetized as much as the others.

Also there could be small effects on the conductivity and permeability of the magnet.

Someone should measure the field at the strings using a rough cast versus smooth. It might be significantly different, and field strength does matter, especially with some degree of non-linearity in pedals and amp. But there are a lot of things that affect the signal level that would have essentially the same effect on the sound, so I am not convinced that we are talking about effects on the sound that are uniquely interesting even if large enough to notice. There is always the different effects of string pull from different filed strengths also.

[Mike Sulzer]

Much less seriously, but with as much relevance as climate change to the significance of polished magnets, we were constructing mock jeopardy questions.

Agriculture for $600
"What is the estimated daily chicken egg output of any one American state?"

Actresses for $800
"What were Lycia Naff's and Kaitlyn Leeb's most memorable parts?"


-- The ex-immoderator

I thought you were supposed to give the answer and let the contestant win the money by coming up with the question, you know, like 5 billion eggs, or two hookers in drag, or whatever.

[big_teee]

Guys, by the jokes and some of the speculation on shining or using "polish" I can't tell if some of you are truly unaware of what the OP is asking, and you're thinking he means to take a magnet and polish it up (of course you'll all deny it later LOL)

Forgive me if some of this sounds condescending on a forum with experienced pickup makers but these threads obviously live on indefinitely and are searched by all types/all levels. I will also start by confirming that I do hear a difference, small enough for most not to care, but big enough we shouldn't be dismissive of those who do care.

This term polished comes from polished vs rough cast, and is generally centered around ONLY humbucker magnets. The better term would be "rough cast oversized, then precision ground down to final size" but that would take too long. Rough cast magnets are cast in an attempt to hit the target size. Then sometimes you'll see a few hits from the grinder here and there where it went over. Often, even a rough cast humbucker magnet is still cast oversized along the critical keeper bar and slug edges. So you'll see those edges clean but the top and bottom are rough. You will see rough cast rod magnets occasionally but that's not typically what is discussed at length by the forum magnet swappers.

Two things occur with rough cast. First, the simple fact that two surfaces have a texture means the field is being dithered. However minutely or inconsequential, a scientist would not consider a variable not to exist, just consider whether its below the threshold of other random differences and/or user perception. But I believe this texture is the main reason they sound different. I could be wrong in that it may also affect how the bar takes the charge. Someone asked "is this before or after charging"; well its a manufacturing process, not a buff on the wheel, so its prior to charging. The charge itself may get a little more wild and random at these nooks and crannies. If so, that would likely level itself out as a slight degauss rather quickly. I haven't measured reduced gauss a the top of the pole with RC vs polished, but that doesn't mean that within the bar magnet there aren't some relaxed areas.

The second thing is that whatever that difference is, it now becomes a bit random. Some rough cast are smaller than others. Some fall away from treble to bass, or from screw to slug. Vice versa if you flip/rotate it of course. It's entirely possible one pickup has softer highs or spongier lows when nothing else has changed. Many would consider random to be bad, and precision to be good. I wouldn't disagree on premise but if you prefer the sound of rough cast magnets, I would equate it to worn-in blue jeans. You may have 5 pairs of various worn-in jeans, of which the fit and degree of wear is random. But you know you'll like ALL of them better than that new crisp pair you just got. So the randomness becomes secondary.

If you want to try to balance consistency with textured surface and rolled edges, you can begin with precision ground magnets and tumble them in media. You'll pick up a bit of randomness, but at least all of your dimensions will have started out precision cut.

Thanks frank for explaing how the magnets are oversized, then ground down.
What is being referred as shiny, still have those grind marks on them.
Some of the discussion I was referring to is on the SD forum.
It has been discussed pretty lengthy on several guitar forums.
I was trying to de Myth the rough cast vs ground, or shiny.
And, the how one could add highs, and one could reduce the highs.
T

[big_teee]

Yes, I think that is the issue.

It is the field at the strings that counts, if it is the dc field we are talking about. Small scale roughness is just not an issue, directly. (You can look at a magnet as a vast collection of tiny dipoles, each of which has a field that falls off with the cube of distance. A small rearrangement of these dipoles has very little direct effect on the field at the string, especially since the dipoles point in the wrong direction.) The field at the string is provided by the pole piece, as magnetized by the magnet. Small scale effects are pretty much averaged out, but if there is a large void right near where the magnet touches a pole piece, that pole piece might not get magnetized as much as the others.

Also there could be small effects on the conductivity and permeability of the magnet.

Someone should measure the field at the strings using a rough cast versus smooth. It might be significantly different, and field strength does matter, especially with some degree of non-linearity in pedals and amp. But there are a lot of things that affect the signal level that would have essentially the same effect on the sound, so I am not convinced that we are talking about effects on the sound that are uniquely interesting even if large enough to notice. There is always the different effects of string pull from different filed strengths also.

The rough A2 magnets I have do charge a little hotter than the Shiny Ground A2 magnets.
Is that the sound difference These Magnet Swappers are referring too, perhaps?
T

[Mark Hammer]

Thanks for an informative reply, Frank. I hope I didn't come off as snarky. The questions I asked alluded to a dearth of information that was needed to fill in gaps before any inferences about the plausibility ought to be drawn. And as your reply aptly illustrates, once the information gaps are filled in, what may have sounded silly to some begins to make eminent sense, and some consilience is achieved. Indeed, reading through the 2nd paragraph of your reply made me anticipate almost precisely what you said in the subsequent paragraph. OF COURSE precision ground edges are going to behave a little differently than rough ones when it comes to physical coupling with keeper bars and/or slugs. I suspect some of us here were thinking purely in tems of shiny polepieces on Strats, which is clearly a different kettle of fish.

[Mike Sulzer]

The rough A2 magnets I have do charge a little hotter than the Shiny Ground A2 magnets.
Is that the sound difference These Magnet Swappers are referring too, perhaps?
T

Could be. Maybe the magnet is a bit thicker before being ground. More magnetic material, higher field.

[frankfalbo]

A proper rough cast magnet is generally undersized. It's cast to not exceed a maximum dimension. That's why you'll still see occasional grinder marks on rough cast. There are still supplier considerations at play, if your rough cast is from a different supplier then there can always be other variables. As with any Alnico, its not what it charges to, it's where it stabilizes.

Mike what I was saying about gauss strength is that in my experiences there were no differences at the top of the pole, but perhaps our meters didn't have enough decimal places. And since the strength at the pole is identical, but the two magnets sounded different, I begin to look elsewhere for the cause.

Mark- no not snarky at all. If someone suggested buffing a magnet to a high luster changed the sound, my reaction may have been twice as sarcastic! (Of course we assume they haven't created enough heat to alter the properties of the alloy)

[salvarsan]

I thought you were supposed to give the answer and let the contestant win the money by coming up with the question, you know, like 5 billion eggs, or two hookers in drag, or whatever.

Alex, I'll take Agriculture for $600.
"What is the estimated daily chicken egg output of any one American state?"

What are 3 million eggs?

I'll take Actresses for $800, Alex.
"What were Lycia Naff's and Kaitlyn Leeb's most memorable parts?"

What is a third breast?
... and if that isn't a memorable part, you're way too jaded for this place.

[David Schwab]

Two things occur with rough cast. First, the simple fact that two surfaces have a texture means the field is being dithered.

Not dithered. That means something totally different. That means to add noise to a signal.

The sides of a magnet don't really have a field. That's the rough part. The poles on a rough cast magnet are ground smooth. That's where the field is.

It's the surface area of the pole that helps determine how strong a magnet is. A thicker magnet would be stronger (assuming they are both fully charged). So if the final ground size matches the rough size, and the magnets are the same type, they should be the same strength.

[ScottA]

I try to not poo-poo any tonal arguments at face value. That being said, I have a hard time seeing how the surface texture of a magnet would make a big difference in performance.

But let's assume, for the sake of argument, that there is a discernable difference between rough and smooth magnets.

Where would this difference come from?

Surface texure (what about roughness at mating surfaces acting like an air gap in the magnetic circuit - maybe)?
Dimensionality (mass)?
How about changes that come about due to the additional heat introduced during the grinding process? This would seem to make some sense to me.