Nice pickup experiment

[bbsailor]

If you pluck a string and look at the amplitude in a DAW, it tends to look like this:

[ATTACH=CONFIG]37953[/ATTACH]

[ATTACH=CONFIG]37954[/ATTACH]

Unless I'm mistaken, that characteristic non-uniform, non symmetrical decay pattern owes to the usual elliptical string movement, where as the string tends to move more up and down, you see the more asymmetrical / high amplitude emphasis, and when the string's movement changes to a more left to right orientation, you see a moment of more symmetry, and lower amplitude, and it continues like that, back and forth, until the note goes quiet.

According the math, the horizontal inductance is a small fraction of the vertical inductance, so whether you're using a blade or pole pieces, the difference with or without that horizontal induction is going to be "buried in the mix". I don't believe there is ever a moment where the string moves perfectly up and down, or left and right, aside from when the string is initially plucked, so there's never a moment of perfect horizontal movement where the output would go silent, there's always a significant enough amount of vertical movement to produce a near constant volumes, although it does get a bit quieter and louder as the note decays, I believe people refer to that as "bloom".

John,

True, but for the following reason. The initial amplitude is due to the angle of the initial string pick attack and the total displacement distance of the string above the magnet. Let us assume that the string displacement is .0625 inches down and .0625 inches up. That means that when the string is vibrating in the most downward location toward the magnet it is in the strongest magnet location and closest to the pickup coil. In the most upward location, 0.125 inches higher than the lowest location, it is in a weaker magnetic field and the farthest location from the pickup coil. This will cause an asymmetry to occur in the initial peak of the note display and decay to a more symmetrical display as the string settles into its sustaining vibration mode. How you pick the string can affect this difference in only the very initial sound. However, the ear is very sensitive to the initial characteristics of the string attack.

As a thought experiment or a physical experiment try this. What would happen if you put another pickup (exactly the same as the one mounted below the strings) but mounted above the strings and wired in series adding? The asymmetry caused by the single pickup below the strings would be eliminated due to the vertical movement between the upper and lower coils and magnetic fields. The horizontal string movement would still contribute to increased second harmonic output. With two pickups in series (upper and lower) the output would be almost doubled.

As pickups are moved farther from the strings the output gets lower but the asymmetry becomes reduced as the relative upper motion string distance is less than the lower string location when the pickup is farther away from the strings. Try moving your guitar mounted pickup .125 inches lower and listen to where the biggest changes in tone are located... (1) initial attack or (2) string sustain portion?

Joseph J. Rogowski

[Mike Sulzer]

Pickup sensitivity is not directly related to inductance (sensitivity and inductance vary differently as the number of turns is changed). Thus, the terms horizontal and vertical inductance do not make sense. I think we need an actual experiment to determine the effect of sensitivity to the horizontal using real strings.

If you pluck a string and look at the amplitude in a DAW, it tends to look like this:

[ATTACH=CONFIG]37953[/ATTACH]

[ATTACH=CONFIG]37954[/ATTACH]

Unless I'm mistaken, that characteristic non-uniform, non symmetrical decay pattern owes to the usual elliptical string movement, where as the string tends to move more up and down, you see the more asymmetrical / high amplitude emphasis, and when the string's movement changes to a more left to right orientation, you see a moment of more symmetry, and lower amplitude, and it continues like that, back and forth, until the note goes quiet.

According the math, the horizontal inductance is a small fraction of the vertical inductance, so whether you're using a blade or pole pieces, the difference with or without that horizontal induction is going to be "buried in the mix". I don't believe there is ever a moment where the string moves perfectly up and down, or left and right, aside from when the string is initially plucked, so there's never a moment of perfect horizontal movement where the output would go silent, there's always a significant enough amount of vertical movement to produce a near constant volumes, although it does get a bit quieter and louder as the note decays, I believe people refer to that as "bloom".

[Mike Sulzer]

John,

That means that when the string is vibrating in the most downward location toward the magnet it is in the strongest magnet location and closest to the pickup coil. In the most upward location, 0.125 inches higher than the lowest location, it is in a weaker magnetic field and the farthest location from the pickup coil. This will cause an asymmetry to occur in the initial peak of the note display and decay to a more symmetrical display as the string settles into its sustaining vibration mode. How you pick the string can affect this difference in only the very initial sound. However, the ear is very sensitive to the initial characteristics of the string attack.


Joseph J. Rogowski

The problem is that you cannot base an analysis of pickup response on the spatial changes of the permanent field alone. If the field were spatially constant, imparting a constant magnetization to the string, the spatial variations of the resulting field from the vibrating string cause the flux through the coil to vary. This process has its own asymmetry as well.

[John Kolbeck]

Pickup sensitivity is not directly related to inductance (sensitivity and inductance vary differently as the number of turns is changed). Thus, the terms horizontal and vertical inductance do not make sense. I think we need an actual experiment to determine the effect of sensitivity to the horizontal using real strings.

Just to make sure we're talking about the same thing; when the string is at it's highest vertical position in the process of rotating, it's magnetism would be at it's lowest since it's as far from the pole piece as it's going to get. When it's moving more left to right, the magnetism would be more steady since it's not coming as near, and moving as far away from the pole piece.

[Mike Sulzer]

Just to make sure we're talking about the same thing; when the string is at it's highest vertical position in the process of rotating, it's magnetism would be at it's lowest since it's as far from the pole piece as it's going to get. When it's moving more left to right, the magnetism would be more steady since it's not coming as near, and moving as far away from the pole piece.

Yes and yes, and so nearly all of the flux change (and thus induced voltage) resulting from horizontal motion results from decreased flux through the pole piece as the string moves from directly over it. Of course, the string might not be directly over it to start with, so this can get complicated.

[John Kolbeck]

They say some pickups have more "bloom" than others, I wonder what a pickup maker can do, or what those characteristics those pickups already have, that would over-emphasize the sound of one phase of the elliptical rotation over the other. Based on the linked article, you'd think rails would have a tone that evolves more as the rotation changes, but I don't think I've ever seen "bloom" and "rails" mentioned together in the same sentence before.

[Mike Sulzer]

They say some pickups have more "bloom" than others, I wonder what a pickup maker can do, or what those characteristics those pickups already have, that would over-emphasize the sound of one phase of the elliptical rotation over the other. Based on the linked article, you'd think rails would have a tone that evolves more as the rotation changes, but I don't think I've ever seen "bloom" and "rails" mentioned together in the same sentence before.

I think in general both horizontal and vertical vibration are present at the same time, but in different amplitudes and phases. This is what the ellipse is: the sum total of the motion. The ellipse rotates slowly, meaning that the relative amplitude and phase of horizontal and vertical vibrations are changing.

A pickup can be thought of as having its highest sensitivity to vibration in some direction. For a rail that is vertical; for some other pickup it might be 30 degrees from vertical. Both would see the evolution of the string vibration, picking up different aspects of it.