Spacer Bar Magnet?

[switchman]

Hello. I've been looking into pickup mods again after not doing it for a long time. I saw this spacer Bar Magnet from Philadelphia Luthier Supply. https://www.philadelphialuthiertool...5-spacer-bar-magnet-2-5-x-25-x-125-magnetized

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I'm having trouble figuring out how this would affect the overall pickup. You could replace the non-magnetic spacer under one bobbin. but usually the other has lead wires so you can't do triple magnet on a PAF style with the braid like the photo I don't think.

Wouldn't it make the magnetic field "lopsided" or stronger in one coil than the other? How would the bars be arranged? North edge facing North or North facing South? Are there any notable pickups built with this type of magnet arrangement? Has anyone here tried this or can you explain what the effect would be?

I know there are triple magnet pickups too but I've never handled one to know how its assembled different from a PAF style.

thanks

 

[freefrog]

In a triple magnet HB like a Gibson 500T or DiMarzio X2N, the magnets are arranged like South-North (left spacer), North-South (center magnet), South-North (right spacer). Philadelphia Luthier Supply doesn't recommend anything else about their magnetic spacers : "When installing these, make sure they are installed so the poles are opposite of the main magnet (ie. they should repel each other). Similar to a P90's magnet installation".

A center magnet + only one side spacer shoud effectively make one of the coils magnetically stronger and therefore louder than before... I don't remember any notable pickup built like that (except to some extent the Bluesbucker recently reviewed by Nienturi)...

But nothing forbids to experiment.

EDIT - The following page shows a sim of magnetic field for "HB mixed mag, ceramic on left A5 on right". IOW, with a ceramic spacer next to the screw poles, apparently.

https://skguitar.com/SKGS/sk/Images/pickups/Pickup stuff/Magnetics.htm

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[Clint 55]

You can use a spacer mag on each side, simply move the leads out of the way and have them go out the side. What do you think they do on the triple mag Duncans?

 

[Seashore]

The Invader is another popular triple magnet pickup. Bare Knuckle makes some too. Some baseplates have more holes and it's possible to reorient the lead so it's not running under the bobbin, but sometimes you're stuck with it.

I've put spacers on one side of a couple pickups and liked the results, but that was with a hybrid and another pickup that was weird to begin with, so I don't know how it would affect a "normie" pickup. The pickup that Nienturi posted actually had two spacers under one bobbin and nothing under the other, if I remember correctly, so an even more extreme version of this idea.

I also made two Invader/500T hybrids, one with the double thickness ceramics from the 500T and the other with three single thickness ceramics, and the single thickness version sounds awesome (well they both do, but I expected it with the other one). Bright, clear, and powerful. It's worth playing around with.

 

[Seashore]

Phila's advice on the orientation is INCORRECT. The fields are supposed to OPPOSE each other so each coil sees the same pole.

You can use a spacer mag on each side, simply move the leads out of the way and have them go out the side. What do you think they do on the triple mag Duncans?

That IS Philadelphia Luthier's advice. Spacers repel center. Nobody is saying otherwise.

 

[freefrog]

That IS Philadelphia Luthier's advice. Spacers repel center. Nobody is saying otherwise.

That's what I understand as well...

This topic gave me the idea to check what was going on with a 500T and a X2N.

It's interesting to see how the magnetic field is so much more powerful with the Gibson than with the Dimarzio: the magnetometer exhibited almost twice higher Gauss readings with the 500T. Readings with vertical probe from the sides of coils were RP compared to their horizontal magnetic field, as implied by the P90 mag orientation principle... But these "lateral" magnetic measurements were stronger than from the top of the coils with the DiMarzio. It wasn't the case with the Gibson HB...

 

[switchman]

Thanks all this is great info making me think of more questions :laugh: That SK guitar image makes it clear. You see you all know way more than me about the high output humbuckers and especially the 3 magnet pickups. Dirty Fingers was the only one I remembered because some Gibson sales rep way back was always talking it up to me. "Dude It's got three magnets!" I kid you not. DIY hybrids or the JB are the highest output I get into.

So freefrog as you said it would make one coil have stronger output. It's increasing the inductance of one coil and therefore the pickup as a whole yes? Could this be thought of as similar to unbalanced coils where one intentionally has more output than another?

If you take a hypothetical PAF type and add the bar magnet spacer under the slug side like the Phila. pic, does making one coil louder also reduce the hum-canceling between the two coils?
I don't know enough about gauss to know what all the effects would be.

Tthe reason I got interested in this is because as I sort of said I lean towards vintage output humbuckers, but I have a couple of chambered guitars which have a bit pluckier thinner natural sound. Various 59 or similar pickups that sound good in other guitars sound kind of weak or blah in them. But medium or overwound PAF types like WLH or Slash were too much. Sound great, just not what I want on those guitars mostly played clean for rhythm not lead. I thought the 2nd magnet might be worth a try for the thinlines in the bridge and maybe neck too.

 

[freefrog]

So freefrog as you said it would make one coil have stronger output. It's increasing the inductance of one coil and therefore the pickup as a whole yes? Could this be thought of as similar to unbalanced coils where one intentionally has more output than another?

If you take a hypothetical PAF type and add the bar magnet spacer under the slug side like the Phila. pic, does making one coil louder also reduce the hum-canceling between the two coils?
I don't know enough about gauss to know what all the effects would be.

No risk for hum-cancelling, normally. Plenty of humbucking stacks involve noise-sensing coils noticeably weaker than their signal coils and they buck the hum without any issue. ;-)

Regarding the balance between coils, predicting the result is not that easy... As a matter of fact, "normal" Gibson style humbuckers are already "unbalanced" from the start, with a slugs coil more efficient by design than the coil with screw poles. Also, the precise shape, mass and alloy of magnetic parts can lead them to convey differently a magnetic field which is rarely consistent along a whole bar magnet... So there's no way to guess what a spacer would do exactly to a given humbucker - and I've often noticed how a magnet giving a good tone to one pickup might make another pickup dull sounding so I don't think that magnetic spacers would behave more consistently. YMMV.

But a spacer is not expensive and shouldn't be too difficult to install so, it might be interesting to give it a try. Let us know your findings if you do this...

 

[Clint 55]

That IS Philadelphia Luthier's advice. Spacers repel center. Nobody is saying otherwise.

I don't know what I was reading.

 

[htrd]

Additional magnet spacers will drop the inductance of your screw coils. Probably because of lowered screw poles permeability in the stronger magnetic field. I haven't observed this effect with slugs, even with double thick ceramic 8 magnets.

For example, regular Black Winter inductance is about 7 H at 100 Hz (~3,5 H for the slug coil and 2,73 H for the screw), while Blackened BW with two smaller screw coils is about 5,5 H (both coils are ~2,5 H and fully symmetrical).

 

[freefrog]

For the record, the 500T that I've tested yesterday was stronger of +/- 200G over the slugs than above the screw poles... But the "lateral" RP measurements with vertical Hall effect probe were in fact stronger on the screw poles side, in roughly comparable proportions.

The X2N with its identical big bar pole pieces was magnetically symetrical, conversely.

+ 1 about the idea that repelling magnets have also a variable and potentially paradoxical effect on inductance according to the magnetic circuit involved.

I was not far in the precedent answer to evoke what happens with P90's: a coil of 6.1H with screw poles and keeper bar will rise at 6.34H with one magnet and 6.58H with two identical non repelling bars... but it will drop again to 6.47H with these bars "correctly" disposed as repelling each other on each side of the keeper bar - which is preferable in this case since non repelling magnets reduce the flux measured from the screw poles to virtually nothing... <:0)

 

[switchman]

Thanks all. I'll try this out, except it might be a few weeks. I don't have a specific pickup I want to tinker with right now. Too bad I didn't realize this option sooner before letting a few go...

I found another thread here from last year on this same topic. https://forum.seymourduncan.com/forum/the-pickup-lounge/6266643-alnico-5-spacer-magnet
I missed it searching the first time.The only actual results mentioned there was Supernautilus​ swapped one of the two full size magnets in a phat cat out to the spacer to reduce inductance. Not sure if it was neck or bridge but its an interesting idea! The reverse of what I was thinking.

Can I ask what equipment you all are using to measure Gauss and Inductance? The interactivity of all the components is so complex and sometimes paradoxical like some of the examples given. Being able to make changes and take notes in real time compared to what I think I hear helps a lot. The last time I looked into it good Gauss and LCR meters were out of my budget.. Maybe there's better options now.

 

[freefrog]

Can I ask what equipment you all are using to measure Gauss and Inductance? The interactivity of all the components is so complex and sometimes paradoxical like some of the examples given. Being able to make changes and take notes in real time compared to what I think I hear helps a lot. The last time I looked into it good Gauss and LCR meters were out of my budget.. Maybe there's better options now.

Various lab meters are used here like Jeulin teslameters (very local products, I'm afraid), Tonghui TH2811D or the smaller Wavetek 27XT LRC meters...

Nowaday, it should be possible to find affordable LRC meters or Gaussmeters online. For instance, there were online discussions recently about a Chinese Teslameter (WT10A? Sorry, I don't recall the brand but I think it's sold under various names anyway). I've tried it and found it as reliable as our Jeulin stuff.

FWIW.

 

[ehdwuld]

I think that was one of my threads

Unfortunately I couldn't get repeated results for the one I purchased

It may not have been the one you suggested

 

[freefrog]

I think that was one of my threads

Unfortunately I couldn't get repeated results for the one I purchased

It may not have been the one you suggested

The WT10A is something that I had spontaneously evoked in one of your threads in order to help, because you asked for an affordable magnetometer.

It's effectively not with this device that you stated to have obtained unreadable results.

Again, a WT10A gives VERY close measurements compared to our (3 times more expensive) Jeulin lab meters.

That said and for the record: as suggested by the FEMM sims on the skguitar site, measuring magnetism is essentially tricky. So, a precise approach is necessary. It's also better to average multiple measurements (and even better if they involve multiple meters). Once that done, experimental results appear as clear, meaningful and on par with theory.