Alnico vs Ceramic in Guitar Pickups

[bassnut]

This is an old discussion among guitar players and pickup makers who are into "vintage" hardware.
The usual belief is that Alnico V sounds "sweeter" in a pickup and ceramic is harsh. I've heard people say it depends on the design and not the magnet...flux is flux.
My question is that if Alnico V has lower coersivity, I believe meaning it has less resistance to change in flux (?), as the guitar string disrupts the field. wouldn't this have an effect on the sound produced? Wouldn't a more radical change in the flux affect other factors i.e.induced voltage in the coil, inductance, capacitance etc. Could this be what the so called "vintage" sound is? I don't think the difference in density has much to do with it as the string to pole piece distance is adjustable...I could be wrong.
Not really understandig this my thinking says that more change = more musical character - less change = stiffer / harsher tone. (good for Heavy Metal players)

Thanks.

 

[nbucska]

Flux is flux but the A. is conductive and acts as a
damping (short circuit). heavy short C. in PU with ceramic magnet may do the same -- so you must design with the
material used.


<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[sreid]

I would think that the sound difference would be based on the "Third Quadrent" charasteristics of the magnet. Ceramic is basically linear in recoil permeability where Alnico is quite nonlinear.

 

[bassnut]

Could you explain that please...to a layman? This may be what I'm actually asking about.

I was just writing a follow-up to nbucska's response:
-----------
Thanks. I've heard this argument before too. The conductive Alnico will invite eddy currents which may rob high freq and dampen the sound somewhat causing the ear to think it's more pleasant. If the magnet however is isolated from the circuit by an insulator (air, adheasive etc) would this still be a factor? The design I'm thinking of uses bar magnets providing flux to magneticaly soft pole pieces. Some designs use cylindrical magnets as pole pieces. The ceramic cylinders in this case wouldn't conduct eddy currents.
The pickup I'm working with is based on a (probably) late 1950s design using Alnico. I'm trying to find a rationale to stay with it. I'm looking for an argument or explaination as to why it's better if one exists. I don't particularly want to dampen any high freq. Truthfully it does sound better with Alnico to me. Less "nasil" for lack of a better term. Maybe the ceramic causes a midrange bump?
Here is a link to a photo of this particular bass guitar pickup. There is a stack of steel laminations under the copper strip between the Alnico V bar mags which convey flux to the pole pieces. There is electrical continuity between the mags and the rest of the hardware for grounding purposes but they could easily be insulated.

http://img.photobucket.com/albums/v371/Hammon/largeimage6.jpg

------------

 

[bassnut]

"...the "Third Quadrent" charasteristics of the magnet. Ceramic is basically linear in recoil permeability where Alnico is quite nonlinear."


Are you talking about a hysteresis loop?
I just did a Google search on "3rd quadrant, recoil permeability"

 

[nbucska]

The string occupies a small portion of the gap- i.e.
the range of the change of the magnetic field is small,
so the nonlinearity must be negligeable, too.




<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[sreid]

nbucska,

I agree that the nonlinearities must be small. However the perception of musical quality is often based on small nonlinearities.

bassnut,

Check out the Magnetic component Engineering website

http://www.mceproducts.com/

The third quadrant recoil permeability are the lines that slope from the vertical axis to the horizontal axis (the lines that shoot straight out from the vertical axis are the MgOe energy product curves).

 

[gphatch]

Actually, it is the SECOND quadrant of the hysteresis loop that you would be interested in, with this and pretty much most other design scenarios, though you're right in that the "lines that slope from the vertical axis to the horizontal axis" would be the ones you are interested in [though Alnicos typically have a "knee" in the curve, so their responses are not linear at all permeance coefficients].

More important though is that if the Alnico magnets were pushed into the non-linear range, they would demagnetize and would thus be useless as guitar pickups.

My thanks to my colleague Mike Devine for his thoughts on this subject.

Gareth P. Hatch, Ph.D.
Director of Technology
Dexter Magnetic Technologies

http://www.dextermag.com

 

[nbucska]

sreid:
U R right -- this discussion is meaningless -- music quality is subjective -- it has to be judged subjectivelly...

<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[gphatch]

While one's "feeling" about a piece of music might be subjective [how a sound compares to another], the ability to reproduce it or understand how it was produced is not [given enough time and effort] - just look at CDs and digital recording.

Gareth P. Hatch, Ph.D.
Director of Technology
Dexter Magnetic Technologies

http://www.dextermag.com

 

[bassnut]

Gentlemen.
Thank you all very much for responding. Truthfuly I'm having a hard time with the physics dialog. A bit over my head.
Actually I'm thinking that the direction you have taken would best be discussed using quantum physics...

Pickup making is a "black art" and nobody seems to understand fully why they work/sound the way they do. Some of he best minds in are still trying to understand why a Strativarious violin sounds so good.
I'd like to understand the effect of the linear vs non liner charactistics of the two materials with this circuit.
I'm wondering if the "knee curve" in Alnico is audiable.
Being mechanical by nature I'm trying to "visualize" the interrelationships and sequence of events as the different components react with each other.

 

[EdStainless]

The pickups are not working near the knee. If they were they would 'wear out' over time as they demaged.
Are the field strengths really the same? Or do the ceramic pickups have higher field strengths resulting in a stiffer or harder sound?
With ceramics or even Alnico 8 you should be able to build lower profile pickups since you don not need as long of mag path to prevent demag issues. These materials have lower B field values, but higher coercivity.
My guess is that if you connected an oscilloscope to various pickups you could see the selective boosting or reduction of various harmonics of the primary string freq. You might need some singal analysis equipment to do the job right, but the information is there.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[gphatch]

Not sure what quantum physics has to do with a fairly "macro scale" design problem....

It's important to make the distinction between "sounding good" and "determining the origin of the sound". While no-one might know why a Stradivarius violin sounds so "good" [i.e. "why do I like this sound?"], there is indeed a substantial body of research on the ORIGIN of the particular sounds that a Strad can make compared to other violins [to do mainly with porosity of cell structure of wood used].

My point is, that science and engineering can give you all the data you could ever want or need, but it can't tell you if that all adds up to a sound that is "good" or "bad" to a particular ear. If you start off with one set of parameters, using a material with a unique set of intrinsic properties, and a restrictive set of design criteria [e.g. geometry], you are unlikely to achieve reproduction of a particular sound. You have to increase the degrees of freeedom on the design, which could negate the usefulness or feasibility of the design in the first place.

Gareth P. Hatch, Ph.D.
Director of Technology
Dexter Magnetic Technologies

http://www.dextermag.com

 

[bassnut]

Back to my original question.
I like the sound of the design I'm making. Many people do. The problem is that I don't know why it sounds "better" than other designs. I'd like to be able to understand and communicate this to people and steer away from any sort of "hype". I'd like to be able to say. "I use Alnico because..." The only reason I'm using it now is because it was used in the original 1950-60s version. It's a good sounding pickup. It has a sort of "vacuum tube" like compression quality to the sound that musicians are liking. The core contains lots of steel and the amount of magnet mass is much more than other designs. I was thinking that Alnico's lower coersivity was contributing somehow. Less "stiff" maybe. Because the disruption of the field by the string, inducing voltage in the coil etc. I was visualizing Alnico as being a more compliant "dance partner" in the circuit.
BTW. The quantum physics comment was a joke.

I appreciate your input very much.

 

[sreid]

First, I have no idea why I said "Third Quadrant."

Second, here's a link to some info on guitar pickups

http://www.guitarnuts.com/wiring/pickups.php

As expected, there are many things that affect the sound (and non-linearity was not mentioned).

Third, The pickup magnets work pretty much open circuit but there is not anything in the system that would demagnatize them.

 

[bassnut]

You guys might get a kick out of this:

http://www.q-tuner.com/index.shtml

This design is using neodymium.

Interesting text...