Why are roughcast magnets more middy? Why are degaussed magnets darker?

[Rex_Rocker]

Trying to understand magnets here. Electrically, what happens when a magnet is roughcast? And degaussed?

My Antiquity JB is noticeably darker than my production JB, but the low-end is not as deep either. Now, I know it's not 100% apples to apples. Who knows what mojo magic powder the CS sprinkled on the pickup. But I do know the common knowledge in this forum is that changing a polished magnet to a roughcast magnet of the same material brings down the treble and bass and brings the mids forward as a result. What causes this? Is it related to inductance?

But then, why is degaussing the magnet causing the pickup to darken? Or to "soften"? What could be causing this? FWIW, I found the magnet on my CS Ant JB is not very degaussed at all. I don't think there is a big difference in output levels comparing both my JB's. My AT-1, even if it's pretty much the same DCR and magnet type, is noticeably quieter, I assume because of the airbucker thing. Again, I realize this is not 100% apples to apples, but consisdering all these pickups are close to the same DCR, same magnet type, and allegedly the same wire gauge, I don't think it's 100% apples to oranges either.

So... I just want to have a deeper understanding of why my favorite pickup is the way it is.

Thank you!

 

[freefrog]

-What makes degaussed magnets darker: their degaussing, precisely.

Some theoricians like Manfred Zollner even claim it's the only difference between AlNi(Co) alloys because the difference in inductance due to ferrous content would/should be too small to be noticeable.

IOW, the only significant difference between an A2 and an A5 would be (de)gaussing...

That's not my experience, TBH, but I won't open any online controversy about that. Let's just state that according to my own experimental data, strongly magnetized magnets change the EQing (bringing more high frequencies but also more bass in many cases) AND give pickups a faster attack with more amplitude (quicker higher transients)...


-Regarding rough cast magnets:
*like most if not all magnets, they don't exhibit homogeneous magnetic fields when charged but IME, they even tend to stay less homogeneously charged from one spot to the other than "modern" shiny bars...
*the texture of their surface is prone to oxydization and creates small gaps + rows of micro-"picots" separating the magnet from other elements - baseplate, magnetic poles. This random physical contact makes pickups more prone to squeal but also brings a subtle change in Foucault currents.

-On inductance: let's just recall that with a strictly same size and mass + charged in the same way, A3>A2>A4>A5>A8>ceramic inductively, while it's the contrary when it comes to magnetic strenght.

ALL that being said and as already stated, I personally avoid like plague generalization on magnets: bars from different eras / foundries or even from different batches if not same batches can exhibit or generate noticeably different measured specs IME.

FWIW. YMMV.

 

[freefrog]

Post scriptum...

*some Gausmeters/Teslameters can be bought online for cheap nowadays;

*here is something to listen : https://youtu.be/R4S2mM3rA6E?si=Xt2m3vPRIAZ0hPIs&t=176

 

[Supernautilus]

I tried putting a polished A5 bar in my SH-18 at one point but I didn't notice much a difference to be honest. If there was any change in tone, it was pretty subtle. I put the rough cast bar back in just to keep it original. Just my 2 cents.

 

[freefrog]

I tried putting a polished A5 bar in my SH-18 at one point but I didn't notice much a difference to be honest. If there was any change in tone, it was pretty subtle. I put the rough cast bar back in just to keep it original. Just my 2 cents.

That's exactly why I avoid generalizations on magnets after more than one measurement with lab gear (the last harvest done here being of 90 experimental results in a few hours, for the record) : a rough cast bar and a polished one CAN exhibit similar as well as very different measured specs.
So subjective experiences may vary.

It doesn't make indifferent what I explained: rough cast mags are less consistent than modern polished ones IME and don't necessarily "behave" in the same way*.

*For those who have the gear allowing to induce resonant peaks and to measure them as well as surface Gauss levels or LRC specs: an interesting experiment is to separate partly a magnet from baseplate and magnetic poles thx to some insulating material emulating more or less a rough cast surface. Measurements done on a humbucker with and without this add should be instructive. ;-)

 

[Rex_Rocker]

-What makes degaussed magnets darker: their degaussing, precisely.

Some theoricians like Manfred Zollner even claim it's the only difference between AlNi(Co) alloys because the difference in inductance due to ferrous content would/should be too small to be noticeable.

IOW, the only significant difference between an A2 and an A5 would be (de)gaussing...

That's not my experience, TBH, but I won't open any online controversy about that. Let's just state that according to my own experimental data, strongly magnetized magnets change the EQing (bringing more high frequencies but also more bass in many cases) AND give pickups a faster attack with more amplitude (quicker higher transients)...


-Regarding rough cast magnets:
*like most if not all magnets, they don't exhibit homogeneous magnetic fields when charged but IME, they even tend to stay less homogeneously charged from one spot to the other than "modern" shiny bars...
*the texture of their surface is prone to oxydization and creates small gaps + rows of micro-"picots" separating the magnet from other elements - baseplate, magnetic poles. This random physical contact makes pickups more prone to squeal but also brings a subtle change in Foucault currents.

-On inductance: let's just recall that with a strictly same size and mass + charged in the same way, A3>A2>A4>A5>A8>ceramic inductively, while it's the contrary when it comes to magnetic strenght.

ALL that being said and as already stated, I personally avoid like plague generalization on magnets: bars from different eras / foundries or even from different batches if not same batches can exhibit or generate noticeably different measured specs IME.

FWIW. YMMV.

Thank you for the explanation.

 

[nienturi]

-What makes degaussed magnets darker: their degaussing, precisely.

Some theoricians like Manfred Zollner even claim it's the only difference between AlNi(Co) alloys because the difference in inductance due to ferrous content would/should be too small to be noticeable.

IOW, the only significant difference between an A2 and an A5 would be (de)gaussing...

That's not my experience, TBH, but I won't open any online controversy about that. Let's just state that according to my own experimental data, strongly magnetized magnets change the EQing (bringing more high frequencies but also more bass in many cases) AND give pickups a faster attack with more amplitude (quicker higher transients)...


-Regarding rough cast magnets:
*like most if not all magnets, they don't exhibit homogeneous magnetic fields when charged but IME, they even tend to stay less homogeneously charged from one spot to the other than "modern" shiny bars...
*the texture of their surface is prone to oxydization and creates small gaps + rows of micro-"picots" separating the magnet from other elements - baseplate, magnetic poles. This random physical contact makes pickups more prone to squeal but also brings a subtle change in Foucault currents.

-On inductance: let's just recall that with a strictly same size and mass + charged in the same way, A3>A2>A4>A5>A8>ceramic inductively, while it's the contrary when it comes to magnetic strenght.

ALL that being said and as already stated, I personally avoid like plague generalization on magnets: bars from different eras / foundries or even from different batches if not same batches can exhibit or generate noticeably different measured specs IME.

FWIW. YMMV.

A similar situation applies to polished magnets as well. I still remember the surprise I felt when I first got my gaussmeter. While examining bar magnets, I was astonished to observe significant differences in gauss readings as I moved the sensor from one end to the other. I still encounter this phenomenon with certain magnets. For instance, I start measuring at one end and get (so to say) 1000G, then as I move millimeter by millimeter, slowly, I see values like 880G, 770G, and 910G. These low-gauss domains don’t always disappear even after recharging the magnet.

However, speaking generally, this phenomenon of varying regions is more common in roughcast magnets, and the differences seem to be a bit more pronounced.

 

[beaubrummels]

I tried putting a polished A5 bar in my SH-18 at one point but I didn't notice much a difference to be honest. If there was any change in tone, it was pretty subtle. I put the rough cast bar back in just to keep it original. Just my 2 cents.

FWIW Sometimes the rig you are playing through, or the settings, doesn't expose the detail that is different.