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

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  • #16
    You could do "waterfall" plots of the same pickup with different mags installed and see if you can "see" any differences in the plots. You would need identical plucks.

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    • #17
      Magnets do not have tonal properties; they have magnetic and electrical properties, which contribute to the sound of the pickup in combination with the other components of the pickup. For example they have a magnetic field strength, electrical conductivity, and magnetic permeability.

      Originally posted by Tone Cam View Post
      I appreciate the suggestions but don't think folks have a clear understanding of what I am asking.

      I made some quick measurements on single isolated Alnico pole pieces that will address some of the comments. The pole pieces measure 0.187 (+/- .001) x 0.671 and have very different tonal properties. I have made a number of Strat sets (with similar winding parameters) from each material and gotten feedback on their tonal properties both professional and amateur musicians. At the present time the most skilled blues player I know (over 45 years of professional experience) has neck and middle pickups from each material in two hybrid (tele bridge and strat neck/middle) teles. He likes both, recognizes that there are significant differences in their tonal properties but is unable to describe the differences beyond saying that one of the materials "sounds more like a 57 strat" than the other.

      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.

      This conclusion is further supported by an experiment in which I added a 0.032 thick x 0.188 dia. unmagnetized disc of Alnico 3 to the bottom of one pole and repeated the field measurement. The disc had virtually no effect on field strength even though past experience has shown that attaching them to the bottom pole surfaces of a fully magnetized strat pickup will significantly alter its tone.

      All the available experimental evidence (and I have accumulated a lot over the past 9 years) indicates that the tonal differences that are observed in samples of the same alloy from different manufacturers are due to variations in ferromagnetic loss. These losses also contribute significantly to observed tonal differences in the soft ferromagnetic materials that are commonly used to make humbucker slugs, screws and keeper bars. In all cases they are sensitive functions of composition, the methods used to cast the materials, and the details of their thermal and mechanical histories. Samples from different foundries vary significantly with respect to one or more of these parameters.

      I don't think it is possible ( or reasonable) to measure the differences in ferromagnetic loss directly but do think it should be possible to describe their effect on pickup tone using reasonably precise terminology. Terms such as 'like a PAF' or 'similar to a '57 strat' get used a lot but have poorly defined meanings.

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      • #18
        Originally posted by Mike Sulzer View Post
        Magnets do not have tonal properties; they have magnetic and electrical properties, which contribute to the sound of the pickup in combination with the other components of the pickup. For example they have a magnetic field strength, electrical conductivity, and magnetic permeability.
        I was thinking the same thing. But then I thought, what if that's not all there is. Is it possible that there is some difference in delivery of magnetism as it relates to the bounce back/beating of the string? I ask because I honestly don't know. What I mean is, do some magnetic materials yield/recover more/less in the presence of another magnetic force? This would certainly change the feel and tone. I thought of this because alnico speakers have a reputation for being more compressed sounding when driven hard. I haven't used enough alnico speakers to report on it. Maybe it's bunk, but a lot of guys are spending three times for the alnico speakers what their ceramic counterparts cost for some reason.
        "Take two placebos, works twice as well." Enzo

        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

        "If you're not interested in opinions and the experience of others, why even start a thread?
        You can't just expect consent." Helmholtz

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        • #19
          Originally posted by Chuck H View Post
          I was thinking the same thing. But then I thought, what if that's not all there is. Is it possible that there is some difference in delivery of magnetism as it relates to the bounce back/beating of the string? I ask because I honestly don't know. What I mean is, do some magnetic materials yield/recover more/less in the presence of another magnetic force? This would certainly change the feel and tone. I thought of this because alnico speakers have a reputation for being more compressed sounding when driven hard. I haven't used enough alnico speakers to report on it. Maybe it's bunk, but a lot of guys are spending three times for the alnico speakers what their ceramic counterparts cost for some reason.
          Here is another view of this issue. Consider the direction of the initial string motion relative to the pole piece locations. In a P bass or J bass pickup the string lies between two pole pieces per string. The mass of the bass strings are high enough to be more damped if the pole piece were too large or strong and located directly below the string. With two smaller pole pieces on each side of the string, any horizontal movement will induce a magnetic pulse in the coil at each end of the horizontal string motion thus emphasizing the second harmonic more than if only a single pole were mounted directly below the string. Emphasizing the second harmonic in a bass makes them sound “less muddy” based on comments about their sound.

          How we perceive sound occurs mostly in the first 30 millivolts seconds of the initial attack, especially when playing live with other instruments.

          Here is a simple experiment to do to hear the result of string movement. Pinch a string between your fingers right above the neck pickup. Pull sideways about .125 inches and release. Listen and/or look at an oscilloscope image of this and look at the relative output of the primary frequency versus the second harmonic at twice the frequency. Now, do this again in the same place over the pickup but this time pinch the string and raise vertically and release. This motion will produce a stronger fundamental output with a more asymmetrical output because on the downward motion of the string it is closer to the magnet while at the upper most string location, it will be in a weaker magnetic field. Try this with the string location located between two magnetic poles and observe and listen to the differences.

          This string motion relative to pole piece locations is a topic that does not get much discussion but based on the comments in this thread, it might be time to discuss this.

          When you add the other typical characteristics of the pickup, such as resonance, Q at resonance, loading by on board controls and effect of coax capacitance on overall performance, you can now see if second harmonic emphasis due to pole placement were in line with resonance characteristics, there could be an emphasized interaction that can now be better understood and added to the discussion.

          Joseph J. Rogowski
          Last edited by bbsailor; 08-08-2018, 04:55 PM.

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          • #20
            The mass of the bass strings are high enough to be more damped if the pole piece were too large or strong and located directly below the string.
            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?
            - Own Opinions Only -

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            • #21
              Originally posted by Helmholtz View Post
              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?
              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.

              Comment


              • #22
                Originally posted by Helmholtz View Post
                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

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                • #23
                  Originally posted by ric View Post
                  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.)
                  - Own Opinions Only -

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                  • #24
                    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.
                    - Own Opinions Only -

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                    • #25
                      Originally posted by Helmholtz View Post
                      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.
                      Last edited by ric; 08-09-2018, 03:36 PM. Reason: typo

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                      • #26
                        Originally posted by Helmholtz View Post
                        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.
                        "Take two placebos, works twice as well." Enzo

                        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                        "If you're not interested in opinions and the experience of others, why even start a thread?
                        You can't just expect consent." Helmholtz

                        Comment


                        • #27
                          "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.

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                          • #28
                            Originally posted by Chuck H View Post
                            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.
                            - Own Opinions Only -

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                            • #29
                              Originally posted by Helmholtz View Post
                              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.

                              Click image for larger version

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

                              Click image for larger version

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                              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.
                              Last edited by Antigua; 08-09-2018, 08:55 AM.

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                              • #30
                                ..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.
                                - Own Opinions Only -

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