Alnico 3 rough cast vs polished

Mikelamury

Mikelamury

New member
I'm going to order some alnico 3 bar magnets to swap into my 490r and I've come across polished and rough cast bars, what's the difference in sound?
 
Each surface seems to impart that vibe on the sound is the best way I can describe it. Smooth is a little crisper, RC rounds off the top a tad and sounds more rattly. I prefer smooth, don't care for RC but many like it.
 
People describe rough as more 'textured' in sound. To my ear, it's a little softer on the top end and has a different quality through the mids - I want to say it's smeared or grainy/threaded sounding, but that wouldn't be right because it's still clear and there is note definition, but it's got some hairy detail on top of the sound. Hard to explain in words.

I'm at a point where I only use rough cast when the pickup sounds harsh to start with. Otherwise, I would recommend polished to get clarity and detail and even sounding.
 
Mikelamury said:
I'm going to order some alnico 3 bar magnets to swap into my 490r and I've come across polished and rough cast bars, what's the difference in sound?
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If there's a tonal difference, it's due to how bars hold the charge and it has potentially to do with how these mags are made... "Polished" mags are most of the time sintered magnets while rough cast ones are... rough cast.

More details here, from the horse's mouth: https://www.stanfordmagnets.com/cast-alnico-magnets-vs-sintered-alnico-magnets.html

Seeing how the surface of RC magnets can vary in texture and color from spot to spot, I've always suspected that many RC bars are less homogeneous in their blend of materials.

BTW and if I can share something else for the record: A3 is theoretically named "alni3" because there's no cobalt in it. :-D
 
The article doesn't really say what percentage are which. It also says for cast, "The resulting magnet has a dark gray exterior and may have a rough surface. Further treatment, such as machining (grinding), can be used to smoothen the surface of the magnets produced." which was my understanding of how polished bars used in pickups are made, at least for Duncan, from posts on here.
 
freefrog said:
If there's a tonal difference, it's due to how bars hold the charge and it has potentially to do with how these mags are made... "Polished" mags are most of the time sintered magnets while rough cast ones are... rough cast.
Click to expand...

This is what I was going to say the polishing doesn't make a difference so much as the manufacture process. To further confuse things, not all sintered/"polished" magnets end up getting polished and end up with a pretty rough surface that looks like a roughcast magnet, but doesn't sound like one. For example the magnet that came out of my GFS VEH that looks like it's roughcast, but you can tell from the texture of the surface and a slightly brighter color it was sintered. There's a chance there are polished roughcast magnets as well, wouldn't know how to look for them though. Then throw into that the original PAFs had sandcast magnets.

I myself personally don't hear any difference that is worth writing home about. Most a the differences people claim swapping from RC->Polished or Polished->RC sound suspiciously similar to the same words someone would use to describe the tonal difference of a fresh set of strings.
 
beaubrummels said:
The article doesn't really say what percentage are which. It also says for cast, "The resulting magnet has a dark gray exterior and may have a rough surface. Further treatment, such as machining (grinding), can be used to smoothen the surface of the magnets produced." which was my understanding of how polished bars used in pickups are made, at least for Duncan, from posts on here.
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Actually, I was about to add to my previous answer that RC mags could be polished too. I've renounced because I posted on a hurry and because it was already said in the article, precisely. ;-)


Chistopher said:
This is what I was going to say the polishing doesn't make a difference so much as the manufacture process. To further confuse things, not all sintered/"polished" magnets end up getting polished and end up with a pretty rough surface that looks like a roughcast magnet, but doesn't sound like one. For example the magnet that came out of my GFS VEH that looks like it's roughcast, but you can tell from the texture of the surface and a slightly brighter color it was sintered. There's a chance there are polished roughcast magnets as well, wouldn't know how to look for them though. Then throw into that the original PAFs had sandcast magnets.

I myself personally don't hear any difference that is worth writing home about. Most a the differences people claim swapping from RC->Polished or Polished->RC sound suspiciously similar to the same words someone would use to describe the tonal difference of a fresh set of strings.
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Yep, things are complex...

Regarding tonal differences: I've met samples of AlNi(Co) mags whose swapping didn't make significant difference in measured mT and inductance, and therefore didn't affect the tone noticeably. Then I've met other mags (vintage and RC, most of the time) whose unique character was perceptible to lab gear as well as to our ears...

The only thing that I find "clear" (?) personally is that the supposed alloy of an AlNi(Co) bar is not necessarily indicative of a tone. There's certainly tonal "tendencies" statistically associated to alloys but IME, a "same" alloy from different suppliers and / or eras can open to noticeably different sounds. I've already evoked several times on this forum the dark blueish bars used by Seymour in his early SH1's: if I trust the depiction of these pickups by SD himself + our inductance meter and Teslameter, these magnets are most probably A5 bars... Their dark blueish aspect confirms that by suggesting a good amount of cobalt... But to my ears and whatever are the coils used with them, they give a sirupy sound that I'd rather attribute to a lower grade of AlNiCo.

Not enough free time to dig this question for the moment. More later maybe. :-)
 
Can I ramble a bit more?... :-P

"Things are complex", was I saying above. At least they appear as such to me. Even on smooth shiny sintered bars from a same supplier / batch and whose aspect was flawlessly identical, I've never measured totally equal and consistent magnetic fields with a Gaussmeter/Teslameter, for example.

I've said that I also suspect a less consistent blend of magnetic materials in RC mags. what makes me think that is the obvious variation of superficial corrosion on vintage RC bars. Example:

https://www.crazyparts.de/pickup-mak...agnet-long.php

RC mags are also less consistent IME when it comes to mass. Two sandcast magnets of the same external dimensions can exhibit convex and concave spots changing their overall mass.

Someone did question me once about inductance measurements: his pickup had more inductance with a RC UOA5 than with a RC A2 while it should have been the contrary. WTF?

It was due to mass: with similar external dimensions, the UOA5 was just heavier, with more of everything than the A2...

IOW, the kind of RC magnets used in guitar pickups seems by nature way less consistent than polished magnets. Hence potential sonic variations (not really predictible IMHO, since physical inconsistencies makes each RC bar potentially unique, whatever is its alloy).

I incidentally happen to think that superficial micro peaks/dips and corrosion of RC bars alter the contact between magnet and baseplate, with an effect on Foucault currents. That would also contribute to explain why players perceive RC magnets as tonally different.

This effect is measurable and reproductible: an electrically excited humbucker has not the same measured inductance and resonant peak(s) when a polished magnet is totally stuck on the baseplate than when it's separated from it by some adhesive tape, for instance - which suggests that RC bars might be emulated by a polished magnet whose surface would be separated from a baseplate by a thin layer of non conductive or resistive materials... :-P

FWIW. Sorry for the probably painful length of this answer. :-)
 
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i love your indepth answers! having a detailed explanation with real world testing is a gift in this field where there is so much conjecture and hearsay. numbers might not tell us everything and our ears may hear things differently, but a better understanding of how things work and the factors involved is great!
 
I think the next link to conquer is translating all the math and lab testing into the real world of "...and this is what that sounds like", then the everyday musician can realize "Ah, so that's what that does" and make really informed decisions when buying parts and equipment.
 
beaubrummels said:
I think the next link to conquer is translating all the math and lab testing into the real world of "...and this is what that sounds like", then the everyday musician can realize "Ah, so that's what that does" and make really informed decisions when buying parts and equipment.
Click to expand...

Now that dust has settled a bit... I was precisely trying to share how and why "this" does NOT always sounds like "that" IME... ;-)
 
A last (?) rambling session about RC vs polished…

A few seconds of Google search let us know what eddy currents did to tone in Bill Lawrence's sonic experience: "No loss of highs at all, but the higher midrange was slightly reduced".

Source:

http://www.billlawrence.com/Pages/Pickupology/External Interference.htm

It was also clearly pictured by Helmuth Lemme showing how eddy currents "scoop" the response just before resonant peak:

http://www.buildyourguitar.com/resources/lemme/secrets5.gif

I've said above that RC mags might contribute to less eddy currents. IOW, these currents might be stronger with polished magnets...

And precisely, Demanic wrote: "Smooth cast is chimey. Rough cast gets a bit more complex in the upper mids but not as bright".

Am I alone to detect a reversed echo between quotes in bold above ?... :-)


Now and to complete my previous geeky tech reflection : by separating partly magnet and baseplate, the irregular and potentially corroded surface of a RC magnet would do something similar to lamination of steel in the cores of transformers:

https://www.vedantu.com/question-an...lass-12-physics-cbse-60d8461a4fd8652fb1c36b67

So, RC magnets would make less “polite” / subdued / more present the resonant peak of humbuckers (resonance located in high mids with typical guitar wiring + cable). Hence more upper mids, more focused.

Incidentally, since my previous message here, I've realized that RC A3 were evoked by a winder on MLP forum as causing a different sound... precisely because their physical inconsistency created some gaps (spaces) between magnet and baseplate (!)...



...But what if a RC A3 has a lighter mass than a polished one and exhibits weaker magnetic properties for whatever reason - inconsistent production, oddball magnet in a series, different origin when it comes to batch / foundry / supplier and therefore different molding/heating/cooling/magnetizing process?... In this case, a lower inductance and a quieter output level should be obtained from the RC magnet... giving a less prominent resonant frequency and a brighter tone... IOW the contrary of what could been expected from RC vs polished. :-P

And I'm not even evoking the difference between contemporary and vintage A3…

Yep, definitively, things are complex. ;-)
 
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Seeing as how I'm putting it ina 490R I think I'm going to go with the smooth surface A3 to avoid any inconsistency and I want more chime than warm sound in my neck pickup.
 
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