Is it possible to accurately describe the tone of magnets and/or pickups?

[mozz]

Single coil strat pickups can be mounted with springs or rubber tubing. Anyone hear that difference? I have heard some people can tell. I think, when you have these nodes, some will get absorbed by the nut, some by the bridge, if not absorbed, reduced and transferred. What nodes or frequencies are absorbed depends on the guitar components makeup. Maybe a brass nut works better with A2 magnets and a bone nut works better with A5, there are too many variables and better is subjective.

[Helmholtz]

You say a spring captures and releases energy, but I don't see the magnet capturing or releasing any energy in this context.

The potential energy is stored in the magnetic field. A changing distance changes the field and the potential energy. I can't see it either, but this is in the nature of potential energy.

The question is, does that resultant beating, or wave interference, decrease the duration of the standing wave?

The answer is "no".

What's this talk about the pickup vibrating? As far as I know, the is pickups is/was perfectly still, unable to move vertically in relation to the strings.

I don't think you would notice the tiny vibration of the PU. If there was increasing string damping, the PU must have been vibrating. An immovable PU or magnet can not damp the string.

If you don't believe me, just ask any physicist you trust.

[Antigua]

Over here we use springs in pull, push and push-pull applications . For pure pull operation some bias force is applied (stretching). This won't change the energy balance.

You say a spring captures and releases energy, but I don't see the magnet capturing or releasing any energy in this context.

Asymmetry influences the vibrational pattern of the string, but I cannot see an influence on the decay of vibrational energy. A spinning top is a completely different problem, it has more degrees of freedom and is not comparable to a vibrating string.

When you have asymmetry there will be some beating with the harmonics. The question is, does that resultant beating, or wave interference, decrease the duration of the standing wave? In my own testing, when you have so much string pull that "stratitus" is audible, the sustain is also noticeably reduced at that point.

Somewhat hard to tell without further explanation. But if so, the PU must have been vibrating with increasing intensity.

What's this talk about the pickup vibrating? As far as I know, the is pickups is/was perfectly still, unable to move vertically in relation to the strings.

[Helmholtz]

That is clearly the case - just forgot to put it into the list of variables. Several well-known pup makers advertise models with 'degaussed' magnets.

I think that there are two effects:

1. The interaction of the poles and strings changes and
2. The small loop hysteresis losses vary with position on the demagnetization curve.

Did you receive my reply to your PM?
I have the impression that the reply function to PMs does not work. Also all of my sent items have disappeared from the box.

[Helmholtz]

It is really easy to observe a plucked strings visual vibrations being damped by moving a hand held magnet near the string and even feel the string vibrations in the fingers holding the magnet due to damping energy transfer from the vibrating string.

Your experiment confirms my statement regarding string damping via magnetic coupling to a movable load (magnet or PU).
Please see my post #24.

[bbsailor]

It is really easy to observe a plucked strings visual vibrations being damped by moving a hand held magnet near the string and even feel the string vibrations in the fingers holding the magnet due to damping energy transfer from the vibrating string. Eddy currents in various Alnico magnet types will vary and roll off some harsher higher harmonics and add a sound that some people call xxxxxxxxxxxx (fill in your own word(s) here).

Here is a web link that discusses the Alnico vs Ceramic magnets used in guitar pickups from an engineering perspective. https://www.eng-tips.com/viewthread.cfm?qid=105845

I hope this puts this issue into a more observable and scientific perspective that pickup builders can use to achieve the desired sound goal.

Leo Fender had a goal to make guitars that sounded good through his amps with enough output to drive the amp for a good musical sound and limited noise. We are still using a pickup technology that is similar to what was invented a long, long time ago but we now have a scientific vocabulary and test equipment to break it down into more technical details. Our current gap is: how is what we call our subjective and marketing characteristics of a pickup sound backed up by objective science?

Joseph J. Rogowski

[Helmholtz]

..because the spring will pull when stretched, and push when compressed, but a magnet merely pulls.

Over here we use springs in pull, push and push-pull applications . For pure pull operation some bias force is applied (stretching). This won't change the energy balance.

I think it's makes sense that a string which vibrates asymmetrically will sustain for less time than a string that vibrates symmetrically, for the same reason that a spun top will stand and spin around longer if it has perfect symmetry.

Asymmetry influences the vibrational pattern of the string, but I cannot see an influence on the decay of vibrational energy. A spinning top is a completely different problem, it has more degrees of freedom and is not comparable to a vibrating string.

Based on that experiment, it does appear that relative amplitude drop more rapidly with increased magnetic interaction

Somewhat hard to tell without further explanation. But if so, the PU must have been vibrating with increasing intensity. The vibration amplitudes will be very low, of course, as the PU has a considerable mass compared to the string.

The magnetic force between string and PU means an elastical mechanical coupling (just like a spring). A spring can only transfer energy from the source (string) to the load (PU), if the load is at least somewhat movable.
Decreasing the PU-string distance increases this coupling and thus the probability of PU vibration. A rigidly mounted PU, though, cannot vibrate and suck energy from the strings.

[Antigua]

An immobile fixed magnet cannot produce a damping effect. It just acts like an ideal spring attached that absorbs and releases the same amounts of energy. This follows from the law of conservation of energy. Things change when eddy current effects are involved.
(I do have a scientific background.)

On the one hand, the ideal spring model makes sense, because there is no damping agent between the magnet and string that serves to eat up the energy, but on the other hand, it's not like a string, either, because the spring will pull when stretched, and push when compressed, but a magnet merely pulls. So the magnetic pull causes the guitar string to be slightly best at all times, when it's moving and even when it's still. A bent string vibrates asymmetrically, because it's being pulled at one end and not the other, and I think it's makes sense that a string which vibrates asymmetrically will sustain for less time than a string that vibrates symmetrically, for the same reason that a spun top will stand and spin around longer if it has perfect symmetry.

I actually did an experiment with a mechanically plucked D string, listening from a Strat neck pickup, and I moved the pickup from very low, to where the pole piece was almost colliding with the strings, and then I normalized the audio in order to account for the difference in amplitude that accompanies pickup height. Based on that experiment, it does appear that relative amplitude drop more rapidly with increased magnetic interaction.



Also in this screen shot you can see the harmonic FFT display, here it is expanded



The most prominent thing that stood out were varying degrees of harmonic beating, especially with the fundamental, and a gradual increase in the 4th and 5th harmonic amplitudes.

[Helmholtz]

Could position of the magnet along the vibrating string length (other than center that is) create a dissonant, and therefor damping vibrations along the strings length? I'm thinking of a problem that is typically called Stratitis. Said to be caused by excessive magnetism due to pickups being adjusted too close to the strings. It causes odd harmonics and damping of sustain is usually reported.

Strong magnetic force between string and PU increases the frequencies of fundamental and harmonics for up and down string movement but not for sideways vibration. The result is beating and dissonance, aka. stratitis. Damping can only occur if the PU is loosely mounted and actually vibrates.
I have not seen any evidence of increased string damping yet.

[mozz]

"My measurements show the difference in field strength between the two fully magnetized poles to be less than 5% and I find it hard to believe this difference to be large enough to account for the nature and size of the tonal differences between the two materials."

Maybe 5% is more than enough to cause these changes. Also, if the pickups weren't exactly the same inductance, same capacitance and located in the same pickguard spot, you can not compare them.

[Chuck H]

An immobile fixed magnet cannot produce a damping effect. It just acts like an ideal spring attached that absorbs and releases the same amounts of energy. This follows from the law of conservation of energy. Things change when eddy current effects are involved.
(I do have a scientific background.)

Could position of the magnet along the vibrating string length (other than center that is) create a dissonant, and therefor damping vibrations along the strings length? I'm thinking of a problem that is typically called Stratitis. Said to be caused by excessive magnetism due to pickups being adjusted too close to the strings. It causes odd harmonics and damping of sustain is usually reported.

[ric]

An immobile fixed magnet cannot produce a damping effect. It just acts like an ideal spring attached that absorbs and releases the same amounts of energy. This follows from the law of conservation of energy. Things change when eddy current effects are involved.
(I do have a scientific background.)

Yes, I figured you did.

Thanks for the explanation in layman's terms. I get it. Ideal spring/ absorbs and releases same amount/ conservation of energy ...I can visualize that.

A contractor I worked for figured his rafter cuts with calculus on an engineering calculator. I did mine with a measuring tape and framing square. Both methods worked but I remember him saying "Ricky if you know the rules you can play the game"... well there are a lot of things I'll never learn but I do add some things once in a while.

Thanks again.

[Helmholtz]

Then add different magnet strengths under the string and measure the decline in decay time from the non magnetized string sample.

Please show measuring results with perfectly fixed magnets.

[Helmholtz]

A fixed magnet next to a vibrating steel string. How can that Not have a damping effect?

I ask from a "isn't that just common sense?" perspective. I don't have any scientific or engineering background.

I'll be interested to see how this plays out.

An immobile fixed magnet cannot produce a damping effect. It just acts like an ideal spring attached that absorbs and releases the same amounts of energy. This follows from the law of conservation of energy. Things change when eddy current effects are involved.
(I do have a scientific background.)

[bbsailor]

String vibration damping requires a loss/transfer of energy. While a strong magnetic field/attraction between string and PU may shift string frequencies for the Y-motion and might increase PU distortion, I don't see a possibility for a damping effect as long as the PU itself doesn't start vibrating.

Are there any measurements showing PU field induced string damping?

All vibrating strings are subject to a decay rate governed by these things.
1. Stiffness at the points of rest being the nut or fret and bridge.
2. Area of the string exposed to the air causing friction while in motion
3. The air density around the string.
4. Any magnetic force near a ferrous metal string.

A simple experiment is to time the controlled pluck of different strings time of decay using an oscilloscope and timer. The time from initial controlled pluck until the sound level decays into the noise is the variable affected by 1,2, and 3 above. Then add different magnet strengths under the string and measure the decline in decay time from the non magnetized string sample.

When vibrating strings were moved into a vacuum, it vibrated longer due to only the removal of the air friction but other factors would still apply and cause a vibrating string decay.

As we tend to want higher output voltages from pickups to improve the signal to noise ratio and improve our subjective perception of the sound, there will always be some damping due to the pickup magnetic field but does this damping affect our musical perception of the tone is the key question. If so, then the magnet in the pickup, or test magnet is too close to the string.

The creative placement of magnets relative to the position of the string needs to consider all the factors that affect sound quality, good, as well as bad.

Joseph J. Rogowski