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Other than magnet strength, what makes one variety of magnet sound different from another?

Discussion in 'Just Pickups' started by Vibro Chimp, Mar 26, 2017.

  1. Vibro Chimp

    Vibro Chimp TDPRI Member

    18
    Jul 22, 2016
    Upper Left USA
    I understand that the composition of a magnet will dictate how much magnetic charge it can hold, and that stronger magnets make a pickup sound brighter and louder, but is there anything else about a magnet that changes the sound? For example, if an A5 is degaussed to the same strength as an A2, will it sound the same? If not, why?
     
  2. rigatele

    rigatele Tele-Holic

    708
    Apr 20, 2014
    Ontario
    The permeability of different types varies, which changes the inductance slightly. That changes the sound, but in a small way compared to other things that can change the inductance much more.
     
  3. GuitarPix

    GuitarPix TDPRI Member

    56
    Oct 1, 2015
    Calgary, AB
    Not only is there a certain amount of gauss strength in a magnet but the formula is different - and just as a steel string would be different sounding than nickel or nylon- different materials in the magnet would emphasize or de-emphasize different harmonics in the note. Even a smooth surface magnet sounds different than a rough cast magnet (from what I've read) because of the way the harmonics are captured in the very complex interactions between string vibration and magnetic field - which is more complex than the oval shape we see in simple demonstrations with iron filings.
     
    Ascension likes this.
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  5. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    There's an internet echo chamber that trades these beliefs as if they're fact. There is no basis in physics for any of this to be true.
     
  6. chezdeluxe

    chezdeluxe Poster Extraordinaire

    Age:
    67
    Dec 29, 2007
    Brisbane Australia
    I keep hearing echoes about "ground loops" in passive guitar circuits. :twisted:
     
  7. GuitarPix

    GuitarPix TDPRI Member

    56
    Oct 1, 2015
    Calgary, AB
    Oh? And what is the truth?
     
  8. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    I'm not saying what is true, I'm saying what is not true.
     
    Doctorx33 likes this.
  9. etype

    etype Tele-Holic

    732
    Sep 23, 2014
    Dallas
    The magnet's contribution is the magnetic field it generates. I can see how using a bar vs slugs (different shapes) could affect the shape of the field, but not the material it is actually made out of. And it seems pretty unlikely that rough cast vs smooth magnets could cause any sort of significant (i.e. measurable) different in the magnetic field.
     
  10. Mr Green Genes

    Mr Green Genes Tele-Afflicted

    Feb 23, 2016
    MI
    Ted Weber explained the difference to me years ago, but most of it was over my head. If I remember correctly, he said they pretty much behave the same way unless they're being pushed to extremes. For many speaker applications, he said ceramic magnets actually make a better speaker, but it wasn't because of the magnet itself as much as the fact that the physical characteristics allowed him to do things with the voice coil, etc, that he couldn't do with an AlNiCo magnet.
     
    Andy B likes this.
  11. Asmith

    Asmith Tele-Afflicted Ad Free Member

    Age:
    20
    Nov 27, 2014
    Morley, England
    This

     
  12. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    A lot of the parts of the pickup perform double duty. The coils function both as an antenna and an inductor to raise the impedance. In a Strat pickup, the magnets are also a structural features. The steel parts not only hold the thing together, but the eddy currents they cause attenuate the high end and help a pickup not sound shrill. The steel pole pieces not only convey magnetism to the strings, but they also increase the inductance of the coils they run through, without also increasing the capacitance.

    In the case of the magnet, the AlNiCo is both a permanent magnet and also a metal, so it functions similar to the steel parts in causing eddy currents and increasing inductance, but to a lesser extent than steel. Different alloys do these different things to different extents. Ceramic bars are not metal, so they do none of that. From an electrical standpoint, they are like "air gap" that magically causes a magnetic field to exist.

    ALNiCo 2, 3 and 4 are all very similar, though, so one thing to be skeptical of are claims that there are big differences between how they perform. Compared to AlNiCo 5 and AlNiCo 8, they are substantially similar to one another.
     
    etype likes this.
  13. jvin248

    jvin248 Friend of Leo's

    Apr 18, 2014
    Near Detroit, MI
    .

    Magnet shape can impact the field - especially the sharpness of the edges. Slugs with ground flat ends compared to rounded flats to pencil points - all variations I've seen on Strat pickups. I once took a cheap import pickup that I pushed out the slugs so I could grind them to different shapes and it changed the tone more than I expected. See the hot zones at the edges of the slugs and baseplate in the images below - FEA models of the magnetic flux density in a Tele slug vs Tele slug with baseplate.

    This edge effect is quite likely where the 'ground' vs 'sand cast' magnet theories originated from. The ground magnets would have sharper edges that concentrate the magnetic flux lines while the rounder edged cast ones (sand casting is limited to minimum radii for the mold to work and not get voids) spread out the flux lines into a more diffuse pattern. Those rough sand-cast magnets do have little spikes like cacti that in theory concentrate the localized field output around them, but could you measure it? The edges of the bar are most important though.

    Pole piece stagger (compare flat Tele bridge pickup to some Strat pickups with classic stagger) changes the tone, you can try it with a humbucker by lowering the whole pickup and then screwing out the screw poles to get more emphasis from the screw bobbin. Then change the flat pattern to different shapes just like a mini-eq pedal. I have found that putting the screws in the fretboard radius to match the strings destroys the classic character of a humbucker, meanwhile a humbucker with Strat stagger sounds a lot more like a Strat (I have one guitar with a neck humbucker that I took advantage of this, I dropped and raised the screw side in the Strat stagger, split the coil, and push/pull to have either single coil or parallel and it gets me really close to a Strat neck #5 and #4 quack.)

    [​IMG] [​IMG]

    .
     
    24 track likes this.
  14. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    More internet myths. The surface texture is irrelevant. The reason a magnet of a given material has as much strength as it does, is because of it's size and shape. Simple polishing the surface does virtually nothing for the size and shape.

    Nobody ever polished an AlNiCo magnet with the notion that it would improve the sound of the equipment it was placed into, they polish it because it has to be fit smoothly into larger mechanisms. If these were rough, it would be difficult to slide them into or around their housing:

    [​IMG]



    The same is mostly true of bevel; a substantial bevel will actually reduce the volume of magnet nearest to the string, concentrating flux into a finer point, but a superficial 5% bevel makes too little of a difference in the overall volume of magnetic material. All the evidence to date suggests that a finer point of flux doesn't make much difference, either.

    The more likely reason there would be a difference between rough cast and polished is that if there is no intention of polishing a magnet, it can be made differently than a magnet that is intended to be polished. AlNiCo 5 is not just AlNiCo 5, there are sub varieties with that. Oriented versus unoriented is one example. Some polish easier than others. Those differences will impact all the various properties of the magnets, as if you have a whole different grade of magnet.
     
    Last edited: Mar 27, 2017
  15. GuitarPix

    GuitarPix TDPRI Member

    56
    Oct 1, 2015
    Calgary, AB
    Well, maybe I just wasted a night but I do love testing ideas to see if there's any merit.

    So, grabbed a ceramic magnet single coil pickup from my parts bin, soldered on a jack, removed the ceramic magnet, then grabbed the ceramic plus ALNiCo 2 and AlNiCo 5 magnets - plugged the pickup into my Apogee one interface and launched iSpectrum. I kept the pickup in on place on a guitar and swapped the magnets around while doing oscilloscope and frequency analysis readings. The note was low E.

    I repeated each test many many times (hence waste of evening) and basically confirmed what I thought - the difference between either ALNiCo and the ceramic was bigger than the difference between the two ALNiCo's - and the difference between the ALNiCo's is subtle, but it is there.

    However I suspect a lot of people can't hear the difference just like I can't see some of the colour differences that my artist girlfriend talks to me about. While I don't have the most acute hearing, I have tested it enough to know I can differentiate tone well enough for practical purposes. When I was choosing pickups I did numerous blind tests to see if anything stood out and the CS 69 consistently was my fave. I wouldn't say I can pick out a specific pickup out of a series of tests if they are close to the same, but I can hear some differences most of the time.

    Anyways, here's a few graphics from my tests:
    The ceramic is way different on an oscilloscope, but the difference between 2 and 5 is very slight.
    OciliscopeMagnets.jpg

    Most of the frequency analysis were like this - fairly different results for each pickup - which could be accounted for by difference in picking; however these are not the attack phase, but just after attack and before fading out.
    FreqAnalyis1.jpg

    And the one 'atypical' result where they were actually all very similar - with some variation in some of the harmonics.
    FreqAnalyis2.jpg

    What does this prove? That I can waste time like anyone else. I'd say there's enough to show there are differences in the harmonic information output by different magnets - but its pretty close and could be argued that without corelating just how much those differences mean to the listener it may not be proof of actual real world difference.

    But like I said, I've done enough blind tests (and yes, I am willing to question myself and test to make sure there is an actual difference) to be comfortable saying I chose the pickups I did because I liked how they sound and it was different enough from other pickups.
     
    Last edited: Mar 28, 2017
    songtalk, PixMix, Indian Joe and 7 others like this.
  16. dougstrum

    dougstrum Tele-Meister

    257
    Oct 6, 2015
    blu ridge mtn cabin
    HA! wasting time can be so much fun:) relaxing and informative also...
     
    24 track likes this.
  17. etype

    etype Tele-Holic

    732
    Sep 23, 2014
    Dallas
    GuitarPix, Any way to discern if the AlNiCo/Ceramic difference is magnet strength vs materials? If the AlNiCo 2 and 5 are similar but different strengths, then it would seem the difference is materials.

    Does this only measure "tone" or does it measure output differences too? For example, despite the similar waves for the 2 and 5, would the 5 still push the amp harder, ceteris paribus.
     
  18. Antigua Tele

    Antigua Tele Tele-Afflicted

    Jun 2, 2014
    west coast
    What was the question you were looking to answer with this test?
     
  19. dogwatermike

    dogwatermike Tele-Meister

    111
    May 10, 2014
    albuquerque
    Aloha,

    There's a nice paper that describes the magnetic field variation with distance for different magnet shapes:

    "Alternative method to calculate the magnetic field of permanent magnets with azimuthal symmetry" by Camacho and Sosa, in Revista Mexicana de Fisica E 59 (2013) 8-17.

    Its in English by a couple of university profs.... it shows the magnetic field variation with distance depends on the magnet shape.... it kinda goes like 1/y cubed... ( y is distance along the axis) ...this results In a different set of harmonics, and therefore a timbre (tone) difference.... I owe you-all a write-up on that...

    So Guitarpix, if the "string height" was different, you will get a slightly different tone (set of harmonics)...likewise, if you pick harder, the string samples different portions of the B field (a different portion of the 1/y cubed curve), and so you get a slightly different tone again.... I like your scientific curiosity.... keep it up!

    Cowabunga!

    Mike
     
    Indian Joe likes this.
  20. Zepfan

    Zepfan Friend of Leo's

    Nov 30, 2013
    Horn Lake, MS
    Testing with electronic devices isn't the same as testing with the ear, how the brain perceives the sound and how the individual likes/dislikes that sound.

    If a person doesn't see much difference and they can't hear much difference, it doesn't matter to them. If another person hears a difference and prefers one over the other, it matters greatly.

    Some would argue that it was all in their head(they wanted to hear it and they therefore did hear it). For some, that maybe true. For others, they actually can hear the difference.

    Best that you can do is try each for yourself, pick out the one you like, be happy with your choice and play it.;)
     
    Teleterr and Piggy Stu like this.
  21. GuitarPix

    GuitarPix TDPRI Member

    56
    Oct 1, 2015
    Calgary, AB
    I wanted to test to see if there was a measurable difference in the magnets as to how they respond to different harmonics.

    The wire was the same, the distance was the same, the guitar obviously the same - the only variable being the magnet itself.

    The second version of the frequency analysis was very very close in the overall response, the only difference being how each handled specific harmonics - which is what tone is made up from - at least for anything more complicated than a sine wave.

    As for listening to pickups - I totally agree that it is your ear that determines the actual qualities.

    I think the best thing is to read or listen to someone who really knows their stuff and listen to pickups they talk with what they say in mind- trying to hear what they've heard. Once you educate your ear about what to listen for then start listening to different pickups and try to determine what it is about those pickups you like or dislike.


    Even if the audience has no concept of how each choice we make in the signal chain affects the sound - we hear it and that can make us enthusiastic or dreading our guitar tone, which - to a greater or lesser extent depending on who's playing - affects how well we play and that's something the audience can hear.
     
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