|
Post by geo on Sept 3, 2012 23:19:20 GMT -5
So I ridiculed my brother for saying that ceramic magnets (as a pickup ferromagnet) are just as good as alnico magnets, and he tells me he Google'd it and it's the popular consensus that the two are equal. So I take a look and lo and behold, everyone's saying they're just as good, but for different tones. Now correct me if I'm wrong, but ceramic is just a less-ordered ferromagnetic material than alnico and should provide inconsistent, muddier, lower-quality tone, right?
|
|
|
Post by newey on Sept 4, 2012 0:39:28 GMT -5
It's hard to make direct comparisons because there's a lot more variables involved than just the composition of the magnets.
Ceramic, I think, got a bad reputation as it was often used in cheaper pickups. But there are now high-quality pickups made with both types of magnets.
|
|
|
Post by darkavenger on Sept 4, 2012 3:26:19 GMT -5
Where to start...
Ceramic magnets typically have a bad rep because the material is less expensive and used in some low end pickups in the form of a bar magnet under metal slugs. The reality is far from that, in fact there are a few areas where ceramic is superior relative to alnico. Alnico is conductive and can form eddy currents reducing high end while ceramic will not. Ceramic typically has a higher permeability, or it doesn't resist a change in it's magnetic field as much as alnico will. Both of these will in theory help give a better high end response, and it's been shown that single coil pickups with ceramic poles pickup more high end harmonics compared to a conductive magnetic counterpart.
Another often over looked advantage of ceramics is their high coercive force, or resistance to become demagnetized. Over time, as you'll find with some vintage instruments, alnico magnets become less magnetized and over all weaker than they were designed to be.
So why doesn't every pickup use ceramic? Well, despite what you might think, you might like the reduced high end, which some might describe as being more 'warm' In a typical humbucker design, using a stronger alnico bar magnet makes more sense, too.
So in a nutshell, there you go!
|
|
|
Post by reTrEaD on Sept 4, 2012 9:20:07 GMT -5
It's hard to make direct comparisons because there's a lot more variables involved than just the composition of the magnets. True dat. Even with "alnico magnets" there are different arrangements. In some, the polepieces ARE the magnets. In others the magnet is a bar placed beneath the polepieces. Not sure what alloy is used for the polepieces of a pickup that uses a ceramic magnet. Ceramic, I think, got a bad reputation as it was often used in cheaper pickups. Alnico magnets are smooth, shiny, hard, and pretty. Ceramic magnets are rough, dull, brittle, and relatively unattractive. I have to wonder if this also plays into the (mis)perception that ceramic magnets are inherently inferior.
|
|
|
Post by geo on Sept 4, 2012 11:43:51 GMT -5
As a ferromagnetic material, ceramics are less oriented than a quenched metal alloy, hence they have a weaker, less uniform field. You're saying that doesn't have a negative impact on tone?
|
|
|
Post by reTrEaD on Sept 4, 2012 13:59:14 GMT -5
You're saying that doesn't have a negative impact on tone? You're saying that is does have a negative impact on tone? How? You can draw a relationship between magnetic field strength and signal amplitude. But amplitude =/= tone. Uniformity of field? Disorder on a micrometer or nanometer level doesn't translate to non-uniformity of field measured millimeters away. None of this suggests to me that ceramic magnets necessarily "provide inconsistent, muddier, lower-quality tone". I'm still of an open mind, but I would need a better explanation than what I've heard here.
|
|
|
Post by geo on Sept 4, 2012 14:18:31 GMT -5
I'm not very familiar with guitar electronics as you can tell from most of my questions/posts, but I'm very familiar with magnets. Nonuniformity in a magnet's composition translates into distortions in the magnetic field it produces. You can consider a ceramic magnet to have a "rougher" magnetic field; the field lines aren't as straight.
In taking scientific measurements, you want your magnet as close to ideal as possible (and generally as powerful as possible so small deviations in the field contribute less error to the overall result). Hence the use of superconducting magnets (like in an MRI machine, that's why those scans are so expensive); the signal-to-noise ratio is best. With alnico to ceramic comparison the alnico should create a stronger, more uniform field. If you treat the vibration of the string as the quantity you wish to measure, then you should get a better measurement with alnico than with a ceramic magnet.
Also, as far as the eddy currents go, using metallic pole pieces with ceramic magnets brings those concerns back on the board.
|
|
|
Post by reTrEaD on Sept 4, 2012 15:01:52 GMT -5
MRI has as much to do with a guitar signal as a sonogram has to a submarine sending out "one ping only" and determining distance according to the time it takes for the return.
The field from the magnet is averaged over an appreciable length (millimeters) of the string. If it's greater or lesser over a microscopic portion of that region, it won't matter. The coil can't differentiate a stronger influence in one region from a weaker influence in the adjacent region. It's all about the average.
If we place importance on microscopic variations in uniformity, I think we might be in "cork-sniffing" territory.
|
|
|
Post by geo on Sept 4, 2012 15:20:28 GMT -5
MRI needs much higher resolution than your guitar does, but the principle in gaining better measurement resolution holds.
The vibrations of the guitar string come out as a sine wave in your current. Non-uniformities in the magnetic field blur or smudge the line of that sine wave. The stronger the magnetic field and the more windings, the greater the amplitude of that sine wave.
By this reasoning ceramics are certainly qualitatively inferior, but we have yet to quantify that and determine exactly how much of an impact it has.
|
|
|
Post by reTrEaD on Sept 4, 2012 16:00:56 GMT -5
MRI needs much higher resolution than your guitar does, but the principle in gaining better measurement resolution holds. Does it? Given the averaging mentioned above, it seems like small-scale non-uniformities within the magnetic field would be largely irrelevent in the guitar application. The vibrations of the guitar string come out as a sine wave in your current. This statement makes little sense. Non-uniformities in the magnetic field blur or smudge the line of that sine wave. This one makes even less sense. Suggesting that something has "blurred" or "smudged" a line implies that the line has width. By definition, a line doesn't. The stronger the magnetic field and the more windings, the greater the amplitude of that sine wave. Why are you even discussing more windings. That part would be best left as a constant. It would make more sense to just focus the comparison on the magnetic field. By this reasoning ceramics are certainly qualitatively inferior, but we have yet to quantify that and determine exactly how much of an impact it has. Or if it has any impact at all.
|
|
|
Post by geo on Sept 4, 2012 16:12:19 GMT -5
Think about what you'd see if you hooked the pickup up to an oscilloscope.
The line width is representative of noise in the signal.
You can't just average and say small-scale non-uniformities don't matter without grounds for dismissing the changes. While small-scale non-uniformities won't change the NOTE being played, they will certainly affect the quality of your sound.
|
|
|
Post by reTrEaD on Sept 4, 2012 16:44:20 GMT -5
Think about what you'd see if you hooked the pickup up to an oscilloscope. The line width is representative of noise in the signal. For noise to affect the "line width" of the oscilloscope trace, it would necessarily have to be a MUCH greater frequency than the "sine wave". You're proposing that the ceramic magnet is somehow generating high frequency noise? Not buying it. You can't just average and say small-scale non-uniformities don't matter without grounds for dismissing the changes. I explained the averaging process over a relatively large region of the string. Kind of makes the concept of "high resolution" a bit out of place compared to spatial imaging. Or are you just choosing to ignore that part of my reply? While small-scale non-uniformities won't change the NOTE being played, they will certainly affect the quality of your sound. I'm not convinced they will affect the "quality" of the sound in a perceptible way, if at all.
|
|
|
Post by geo on Sept 4, 2012 17:03:31 GMT -5
The line width of the oscilloscope trace would also be representative of the "averaging" along the length of the string you're so concerned about. Understand where line width comes from and not just what causes it. Non-uniformity in your ferromagnetic will cause smudging in the oscilloscope's signal since they "roughen" the field.
While I acknowledge that averaging does occur over the length of the string above the pickup, it's not acceptable to claim this averaging eliminates effects from inconsistencies in your ferromagnetic without some sort of quantitative argument.
The actual discernible difference in quality would have to go to a quantitative test, but I can say with confidence that if there are good alnico pole pieces and bad alnico pole pieces and this creates a perceptible difference, then pickups using alnico magnets should be superior to ceramics.
|
|
|
Post by reTrEaD on Sept 4, 2012 17:37:18 GMT -5
The line width of the oscilloscope trace would also be representative of the "averaging" along the length of the string you're so concerned about. No. Understand where line width comes from and not just what causes it. Double-speak. Non-uniformity in your ferromagnetic will cause smudging in the oscilloscope's signal since they "roughen" the field. Speculative and mostly nonsense. Non-uniformities on a microscopic level aren't going to affect the uniformity of the magnetic field at a distance. At least not in any appreciable way. This concept of "roughening" the field or making the lines of force being "less straight" borders on the absurd. I can cause local turbulence in a flowing river by sticking my finger in. Does the flow appear less laminar a mile down the river because of my finger? it's not acceptable to claim this averaging eliminates effects from inconsistencies in your ferromagnetic without some sort of quantitative argument. But it's perfectly acceptable to speculate that microscopic inconsistencies cause an effect on a macro scale with nothing more "quantitative" than claims of "roughening" or smudging an imaginary trace on an imaginary oscilloscope? Could you define the rules here? They seem even more "inconsistent" than the ceramic magnet you describe. The actual discernible difference in quality would have to go to a quantitative test, Yep. but I can say with confidence that if there are good alnico pole pieces and bad alnico pole pieces and this creates a perceptible difference, then pickups using alnico magnets should be superior to ceramics. You can say that? Really? One thing does not infer the other. Your "logic" defies logic.
|
|
|
Post by JohnH on Sept 4, 2012 18:05:33 GMT -5
I think we may be in an area where geo has some particular technical expertise that most of us dont have. Keep discussing politely. I think we can all learn something hete if we can bridge the gap between what we each know in different (magnetic) fields
|
|
|
Post by geo on Sept 4, 2012 18:49:05 GMT -5
We assume here that the point on the string directly above the magnet is the closest to the magnet, and that the string as a whole moves in a perfect sine wave for simplicity.
1) Because the string isn't perfectly straight and isn't perfectly parallel to the oscilloscope, you'll see some "smudging" in your signal.
If you would like for me to explain or justify this in greater detail, please request.
2) We'll pretend that pole pieces are flat surfaces and that the magnetic field decreases linearly with respect to height above the surface for the string where it is directly above the pole piece, and quickly elsewhere.
If you would like for me to explain or justify this in greater detail, please request.
3) We'll agree that ferromagnetic materials with non-uniformities obey the superposition principle. The sum of small deviations therein results in a weaker magnetic field of less uniformity.
If you would like for me to explain or justify this in greater detail, please request.
4) In an oscilloscope measurement of our signal, small deviations in the signal are seen as smudging. This is easy enough, especially since we're considering a sine-wave input. If you disagree, we'll just overlap each consecutive wave and there will be smudging.
If you would like for me to explain or justify this in greater detail, please request. With this point please be very specific about your problem with the assumption.
The statement that if there are good and bad quality alnico magnets then surely ceramics are inferior stems from the fact that bad quality alnico pole pieces are less ordered than good alnico pole pieces, and if that is audible then surely the difference between alnico and ceramics is audible.
|
|
|
Post by reTrEaD on Sept 4, 2012 19:56:18 GMT -5
We assume here that the point on the string directly above the magnet is the closest to the magnet, and that the string as a whole moves in a perfect sine wave for simplicity.
1) Because the string isn't perfectly straight and isn't perfectly parallel to the oscilloscope, you'll see some "smudging" in your signal.
If you would like for me to explain or justify this in greater detail, please request. Please elaborate. The business of the string being out of parallel causing "smudging" sounds like pure fabrication. 2) We'll pretend that pole pieces are flat surfaces and that the magnetic field decreases linearly with respect to height above the surface for the string where it is directly above the pole piece, and quickly elsewhere. If you would like for me to explain or justify this in greater detail, please request. Please elaborate. I was under the impression that the decrease in magnetic strength wasn't linear. I thought it decreased by a cube of distance ratio. 3) We'll agree that ferromagnetic materials with non-uniformities obey the superposition principle. The sum of small deviations therein results in a weaker magnetic field of less uniformity.
If you would like for me to explain or justify this in greater detail, please request. Please elaborate. While the sum of small deviations explains a weaker field, it doesn't imply that the net affect at a distance results in a highly non-uniform field. 4) In an oscilloscope measurement of our signal, small deviations in the signal are seen as smudging. This is easy enough, especially since we're considering a sine-wave input. If you disagree, we'll just overlap each consecutive wave and there will be smudging.
If you would like for me to explain or justify this in greater detail, please request. With this point please be very specific about your problem with the assumption. No need to elaborate here. The "small deviations in signal" = smudging is a red herring. Any "smudging" that would occur on an oscilloscope trace would be caused by changes in amplitude (vertical) at a much higher rate than the horizontal sweep. Apparently your imaginary field is so severely distorted that small movements of the string result in rapid and disparate changes of the imaginary signal on the imaginary oscilloscope. The statement that if there are good and bad quality alnico magnets then surely ceramics are inferior stems from the fact that bad quality alnico pole pieces are less ordered than good alnico pole pieces, and if that is audible then surely the difference between alnico and ceramics is audible. Poor assumption, imho. To draw this conclusion we need to assume the only difference between "good" and "bad" quality alnico is order on a microscopic level. We have to assume there are no cracks, voids, inclusions, or large-scale segregation of the alloy. That's not an assumption I would make.
|
|
|
Post by long813 on Sept 4, 2012 20:03:31 GMT -5
Interesting debate, one I've seen without loudspeaker construction as well.
Previous research into the loudspeaker debate, shows that the reason that manufactures switched to ferrite magnets (Strontium Ferrite), wasn't a cost issue, but one of availability. The largest supplier of cobalt (Zaire) at the time (and still are IIRC) underwent a war. Although not scientific, history plays a huge part in the materials used in products today, so a worthy note.
Pulling off some rough numbers from the web (it's a vast over simplification considering how many alloy compositions you can have)
Alnico Br: 12,500 Hc: 640 BHmax: 5.5 Tbr: -0.02 Tmax: 540 Tc: 860
Ferrite Br: 3,900 Hc: 3,200 BHmax: 3.5 Tbr: -0.20 Tmax: 300 Tc: 460
Based off this data, and it is a general piece of knowledge, that Alnico's are affects far less by temperature than ferrites and are much easier to demagnetize. (It's why alnico horse shoe magnets come with a keeper). Alnico's are also much more resistant to back emf and stable ... although in the power we are talking, neither alnico's or ferrites should be pushed out of it's operating point (knee of the BHcurve).
Lets get on with it.
The talk (in loudspeaker) about Alnico's are that they provide smooth compression. When the signal (AC) moves through the voice coil a magnetic field is produced. Because of the alternating polarity of the coil and the constant polarity of the perm. magnet, the voice coil oscillates. The magnetic field generated opposes the perm. magnet. The resultant effect is that the alnico has a smaller magnetic field - voice coil moves less. They call this the 'smooth compression'.
With ferrites, the magnet doesn't demagnetize as easily, so the voice coil will oscillate to it's maximum (mechanical limit). This apparently gives the 'harsh' or 'edgy' sound.
Note that these effects occur when loudspeakers are driven very high and if the ferrite magnets are designed properly it will obtain the same results.
In my reading for PU's I came across a nice analogy:
Alnico vs ceramic's is analogous to tube and SS amps. The effects are noted when the amps are driven high. When the SS starts to clip, the sound becomes harsh, where as the tube-amps compress smoothly at high levels.
My opinion, I don't think one would notice much different between the two in a guitar. If you take a high quality pickup of either material, it should be designed right and thus sound equally as good. Conversely, if you take a poorly constructed PU, irregardless of the material, it will probably sound bad.
Lastly, I don't think that there is enough energy in the guitar to shift operating points of the pickup, so again, it's all in the construction of the pickup and less about the material.
|
|
|
Post by geo on Sept 4, 2012 20:16:32 GMT -5
1) Smudging is created because the magnet feels a pull from the string at multiple distances simultaneously. Each of these distances is felt, so there's some uncertainty in the measurement since you're not measuring exactly one quantity. This is felt by the o-scope as noise.
2) The force between a point magnet and a point of interest decreases with the square of distance. The force between a magnetic wire and point decreases linearly with distance. In the wire very near the magnet we can consider the latter scenario to be a valid approximation. For justification past that you'll have to consult a physics textbook. Personally, I recommend Griffiths book on Electricity & Magnetism.
3) The field isn't highly non-uniform, since the non-uniformities are small compared to the overall field strength, however it is appreciably non-uniform when we consider small deviations in the wire traveling through the field. Again, to determine how large this effect is, you'd need some sort of quantitative measurement. It remains, however, that non-uniformities do affect the signal regardless of whether or not the ear can appreciate this effect.
4) Changes in amplitude of the string ARE the signal. If you're missing that, then that explains much of our dispute over the smudging.
Your last point is poignant and entirely valid. It does leave us to predict that a number of cheaply manufactured alnico pole pieces would be of much higher quality than others from the same batch, which is interesting.
|
|
|
Post by geo on Sept 4, 2012 20:20:20 GMT -5
@long: In examining pickups you have to look at much weaker effects than in speakers. The signal will later be amplified.
While looking at magnets for speakers we want to see how they react when pushed as hard as the go.
While looking at magnets for pickups, we want to see how they react to very small perturbations.
|
|
|
Post by long813 on Sept 4, 2012 20:32:45 GMT -5
@long: In examining pickups you have to look at much weaker effects than in speakers. The signal will later be amplified. While looking at magnets for speakers we want to see how they react when pushed as hard as the go. While looking at magnets for pickups, we want to see how they react to very small perturbations. Which is actually my point - although, I forgot that concluding statement. The effects of Alnico vs ferrite is seen when alnico is pushed out of it's operating region. At lower levels, they act the same. For another analogy to drive home my point, you have 3L of water to hold and the choice of two cups - one with 4L capacity, one with 5L capacity. @ 3L, the differences between the two cups are not seen. It's only when the water reaches 4L and above are differences noticed. Or... It could be that the alnico IIs are constructed in such a way that they do move out of the knee (playing with coil turns, pole pieces, magnet size). So, they wouldn't actually be operating any differently from their loudspeaker counter parts. I don't know much about their construction, but I could see this being true.
|
|
|
Post by reTrEaD on Sept 4, 2012 22:14:27 GMT -5
1) Smudging is created because the magnet feels a pull from the string at multiple distances simultaneously. Each of these distances is felt, so there's some uncertainty in the measurement since you're not measuring exactly one quantity. This is felt by the o-scope as noise. Complete and utter fabrication riddled with horrible inaccuracies. An oscilloscope can't "feel" anything other than the instantaneous net voltage at any given moment in time. The magnet doesn't generate the signal, it merely provides the lines of force that the string displaces as it moves. Whatever is "felt" at the magnet is largely irrelevant. The current induced in the coil (and the subsequent voltage across a load) is an aggregate of all the lines of force that have moved through the windings at that moment in time. To suggest that the trace will be widened because of individual disparities of string distance is ludicrous. What I've just read from you goes a long way toward convincing me that you're just making things up to support your hypothesis. 2) The force between a point magnet and a point of interest decreases with the square of distance. The force between a magnetic wire and point decreases linearly with distance. In the wire very near the magnet we can consider the latter scenario to be a valid approximation. For justification past that you'll have to consult a physics textbook. Personally, I recommend Griffiths book on Electricity & Magnetism. You might want to reread the book. I'm quite sure you'll find a 1/r 3 relationship for magnetic strength vs distance. Else bin the book. 4) Changes in amplitude of the string ARE the signal. If you're missing that, then that explains much of our dispute over the smudging. Our dispute over "smudging" can be summed up in a nutshell. You're making claims about how an oscilloscope functions that are based on misconceptions rather than fact.
|
|
|
Post by geo on Sept 5, 2012 1:18:14 GMT -5
Since we're getting down to the nitty-gritty here goes: The o-scope measures the first-order derivative of the magnetic field measured by the solenoid, which is determined by the change in the field of the pole piece, which is determined by the instantaneous velocity of the pole piece vibrating on a micrometer scale (hey, all of a sudden those tiny irregularities are looking kinda big!), which is related by the magnetic field of the pole piece to the vibration of the guitar string. Thus unevenness in the guitar string evokes an uneven acoustic wave in the pole piece and an uneven response in its magnetic field and noisy signal in the oscilloscope. If you want to pursue this discussion much further you'll have to look into some graduate materials on solid state physics. I feel it's important to mention: the o-scope should be looking at current here, not voltage.
The operative word was point magnet; I'm really trying to simplify the problem as much as possible. The force due to a dipole decreases as distance cubed, not the same for a monopole. When r is close to d you don't use the dipole equation so I simplified and treated it as a monopole for simplicity's sake. Truthfully, it shouldn't matter since we're not trying to make a quantitative solution (unless you'd like to boot up Mathematica and model this).
I strongly encourage you to connect a guitar pickup to an oscilloscope and experiment a little. Granted, a great deal of smudging of the line will be electronic noise from the oscilloscope, but if you get your hands on a nice one you should be able to see the effects I've discussed.
|
|
|
Post by reTrEaD on Sept 5, 2012 2:28:05 GMT -5
Since we're getting down to the nitty-gritty here goes: The o-scope measures the first-order derivative of the magnetic field measured by the solenoid, which is determined by the change in the field of the pole piece, which is determined by the instantaneous velocity of the pole piece vibrating on a micrometer scale (hey, all of a sudden those tiny irregularities are looking kinda big!), which is related by the magnetic field of the pole piece to the vibration of the guitar string. Thus unevenness in the guitar string evokes an uneven acoustic wave in the pole piece and an uneven response in its magnetic field and noisy signal in the oscilloscope. Nice bit of gobbledygook. I particularly enjoyed the part about the acoustic wave in the pole piece. If you want to pursue this discussion much further you'll have to look into some graduate materials on solid state physics. Almost as amusing as the part that preceded it. I feel it's important to mention: the o-scope should be looking at current here, not voltage. You'll be hard-pressed to find an oscilloscope that measures current. But fear not. The current in a circuit is proportional to the voltage across any resistor in the circuit. The operative word was point magnet; I'm really trying to simplify the problem as much as possible. The force due to a dipole decreases as distance cubed, not the same for a monopole. When r is close to d you don't use the dipole equation so I simplified and treated it as a monopole for simplicity's sake. Are you about to tell me your magnet is comprised of monopoles, not dipoles? Give me fair warning so I know when to start laughing. I strongly encourage you to connect a guitar pickup to an oscilloscope and experiment a little. Granted, a great deal of smudging of the line will be electronic noise from the oscilloscope, but if you get your hands on a nice one you should be able to see the effects I've discussed. Which effects are we talking about now? Would that be the nonsense in your most recent post or the earlier nonsense regarding how "the magnet feels a pull from the string at multiple distances simultaneously." I think it's important to know which nonsense we should attribute this to.
|
|
|
Post by geo on Sept 5, 2012 17:58:02 GMT -5
Okay, let's do this real quick:
Learn up on solid-state physics if you want any idea what's going on inside the magnet. It might also be called condensed matter, but same difference.
See above.
Right! But our signal is current, so we want to look at the waveform of the current. Since this is a thought experiment, we've got a magic oscilloscope that measures current or we've taken the resistance and converted.
The distance-cubed equation is an approximation for dipoles which is only valid when the distance from the dipole to the point measured is much, much larger than the dipole moment. You've really gotta read that Griffiths book, kiddo.
Griffiths covers the principle of superposition so you'll be OK.
|
|
|
Post by darkavenger on Sept 6, 2012 0:30:57 GMT -5
Wow, gone for a day and a ton of great discussion and quite a bit of usefully knowledge and information! Also, as far as the eddy currents go, using metallic pole pieces with ceramic magnets brings those concerns back on the board. This is a great point and possibly a part of why ceramic bar SCs tend to sound 'worse' or different. That being said, a typical fender single coil usually has magnetic poles and since the cheap imitation is trying to emulate those poles with metal slugs and a bar magnet, well that's a big difference! Of course, these cheap imitations generally don't adhere to standards for pickup winding either, usually wound inconsistently(not scatter wound) and even with odd wire gauges. Basically they are crap and only resemble Fender's coils on the outside, but that's not to say ceramic magnets are crap because they used them in cheap knock offs. So anyway, in my opinion and from what I've gathered ceramic based pickups have more 'high end harmonics' than alnico. The exact reason or reasons is yet to be definitively shown, but I've offered some explanations. Either way, there is an audible difference and this shouldn't be the discussion rather why this occurs and as the OP asked, are ceramic inferior? My opinion is absolutely not, but they are different and something to factor into the design of a pickup. As to the small side discussion about oscilloscopes and readings... It's interesting stuff, I've never had or used one but I would love to some day. The precision of a pickup is far from an MRI, but I see the point trying to be made. I'd think that the lengthwise area of the string being sensed would be a bigger concern since the strings are made from ferromagnetic material and are magnetized. Just some thoughts.
|
|
|
Post by geo on Sept 6, 2012 1:09:55 GMT -5
Is there any physical theory (even unproven) as to why ceramics pick up high end better? That sounds like an interesting area for experimentation.
I heard it mentioned before, but I assumed that ceramics were just missing some mids and lows so the highs were more noticeable.
I find it noteworthy that Standard Strat (the Mexican one) ships with ceramics sandwiching six metal poles. I'm assuming that's at least half the price difference between Mexi and American strats?
|
|
|
Post by darkavenger on Sept 6, 2012 1:28:54 GMT -5
My theory is that it has to do with a mix of either... eddy current in alnico, higher permeability in ceramics, or/and a higher coercive force and hysteresis in ceramics. Gauss/strength must also be taken into account and it's relationship with ceramic's permeability and inductance as well as the string's magnetic properties.
As to how each of these factors impact the high end response and the degree they do it with... I don't know exactly. For being such a simple device, there are a great many variations of pickup designs around.
Edit: added info on hysteresis, string's magnetism.
|
|
|
Post by geo on Sept 6, 2012 1:37:04 GMT -5
Has anyone looked into material properties? (Specifically Young's Modulus.) It might just be the fact that I'm a solid-state physicist so I look for solid-state everywhere, but I can't help but wonder if phonon transport is an important factor.
In regular English: I wonder if it has to do with how much the two materials stretch to being pushed/pulled by their magnetic interaction with the string. How well the vibration from the string travels through the magnet might be very important, not just how well the magnet feels the string.
|
|
|
Post by long813 on Sept 6, 2012 11:54:50 GMT -5
I feel you're looking deeper than you need to be.
The solid-state physics of the magnetics explains the hows and whys of their magnetic fields, permeability, reluctance etc.
You need to look at these quantities, not the smaller scale qualities. Much like you don't describe the strength of steel in terms of atomic particle forces.
I did some reading, and my post on loudspeakers applies to pickups. These pickups are designed the same way the loudspeakers are. Pickups using alnico magnetics are designed to be in saturation - giving that smooth compression sound people talk about.
On the other hand though. If a pickup using ceramic is designed to match the field of a alnico magnet you should not be able to hear a difference.
|
|