Nice pickup experiment

[tedmich]

I just ran across renaissance man Alex Kenis's page looking at blade vs slug PUPs, the man's a born empiricist!

https://alexkenis.wordpress.com/2015...s-pole-pieces/

I especially liked his idea of using a soft iron bar mounted on a speaker to isolate the radial movement...

lots of interesting pickup work there.

[elipsey]

Nice work there. A diagram defining the axes would be nice; I'm a little hazy on his terminology.

A higher ratio of horizontal component suppresses odd-order harmonics and raises the overall harmonic content in relation to the fundamental.

I think I take this to mean that blade pickups will have greater odd-order harmonic component, and the balance can be tuned to taste, but maybe I'm not getting it?

[John Kolbeck]

I'm really surprised by what I'm seeing here, as it is showing the horizontal contribution to be roughly 75% the vertical for the pole pieces. My understanding is that induction resulting from horizontal movement is only a tiny fraction of that which results from vertical movement.

[Mike Sulzer]

Maybe the amplitude of "string" motion was unrealistically high; this would exaggerate the relative importance of the horizontal motion.

I'm really surprised by what I'm seeing here, as it is showing the horizontal contribution to be roughly 75% the vertical for the pole pieces. My understanding is that induction resulting from horizontal movement is only a tiny fraction of that which results from vertical movement.

[Mike Sulzer]

Nice work there. A diagram defining the axes would be nice; I'm a little hazy on his terminology.



I think I take this to mean that blade pickups will have greater odd-order harmonic component, and the balance can be tuned to taste, but maybe I'm not getting it?

I think you have that right, but I think the relative importance of the horizontal motion for realistic string motion is less, and so this effect is not so important as it might seem.

[John Kolbeck]

Semi on topic question;

In the experiment, he has one full sized Strat pickup and half of a rails humbucker, so essentially it's a half sized Strat pickup. When you have a wide area wherein induction is occurring beneath the string, frequencies of string vibration that happen to be half the width (or 1/4th, 1/8th, etc.) of that width will cancel out, because both the positive and negative component of that frequency are inducting at the same time. Does this mean that the thinner blade coil will have a more linear response, in that it would cause fewer harmonics to cancel themselves out in that manner?

[Mike Sulzer]

The length of string sensed is usually a lot less than the width of the coil because it is limited to the part of the string significantly magnetized by the core(s) or blade(s).

Semi on topic question;

In the experiment, he has one full sized Strat pickup and half of a rails humbucker, so essentially it's a half sized Strat pickup. When you have a wide area wherein induction is occurring beneath the string, frequencies of string vibration that happen to be half the width (or 1/4th, 1/8th, etc.) of that width will cancel out, because both the positive and negative component of that frequency are inducting at the same time. Does this mean that the thinner blade coil will have a more linear response, in that it would cause fewer harmonics to cancel themselves out in that manner?

[LtKojak]

How is all of this related to the actual elliptical movement of a string?

How valid is the data?

[John Kolbeck]

The length of string sensed is usually a lot less than the width of the coil because it is limited to the part of the string significantly magnetized by the core(s) or blade(s).

So the pole pieces are maybe 4.95mm while the blade looks to only be about 1mm wide. I'm not sure how wide the significantly magnetized portion of the string is above the blade compared to the pole piece, but supposing it was 4.95mm for one and 1mm for the other, within the 4.95mm area you could have harmonics with node widths of 2.475mm, with a positive and negative component that are both inducing voltage, where as with the 1mm width you'd only see induction from either the positive or the negative component of that same harmonic, therefore no cancellation. Would those harmonics be outside the audible range, or could the serve to color the resulting tone?

[rjb]

The reason for this test is that I had theorized that the transversal string-movement response (across the pickup face) was lower for a blade style pickup as a result of the orientation of the lines of magnetic flux, and as a result, the horizontal movement of the string contributes less to the overall output signal, which is significant for a few reasons that I will explain.

Ray Butts knew this in 1957. See Patent 2,892,371, column 4, lines 13 through 33.
(How he knew it, I have no idea.)
https://docs.google.com/viewer?url=p.../US2892371.pdf

[Mike Sulzer]

How is all of this related to the actual elliptical movement of a string?

How valid is the data?

The ellipse of string motion indicates that both horizontal and vertical motion are present, generally in different amounts and not vibrating in the same phase. The rotation of the ellipse indicates that the phase relationship changes with time. This is complicated; I think it might mean that if the horizontal motion is detected significantly by the pickup, you should hear the harmonic content changing as the ellipse rotates, causing reinforcement/subtraction. I have never noticed such a thing, and so maybe the horizontal is not detected so well as this experiment indicates.

Another sort of test would be to build a pickup with a slot for insertion of a blade. You could insert a full blade as usual, or "bladelets" of different lengths under the strings, varying from less than the diameter of a pole piece on up. You would listen for differences, and measure the spectra of string harmonics. Because you are just looking for different ratios of harmonics you could use a normal complement of strings in the measurements, picking for carefully and repeatedly.

[Mike Sulzer]

So the pole pieces are maybe 4.95mm while the blade looks to only be about 1mm wide. I'm not sure how wide the significantly magnetized portion of the string is above the blade compared to the pole piece, but supposing it was 4.95mm for one and 1mm for the other, within the 4.95mm area you could have harmonics with node widths of 2.475mm, with a positive and negative component that are both inducing voltage, where as with the 1mm width you'd only see induction from either the positive or the negative component of that same harmonic, therefore no cancellation. Would those harmonics be outside the audible range, or could the serve to color the resulting tone?

Those are very high harmonics. For comparison, the spacing of the two coils in a standard hum bucker introduces such a filtering effect, but it is only significantly audible on the bass strings. For the treble strings, the harmonics get out of range of the guitar speaker.

[John Kolbeck]

Ray Butts knew this in 1957. See Patent 2,892,371, column 4, lines 13 through 33.
(How he knew it, I have no idea.)
https://docs.google.com/viewer?url=p.../US2892371.pdf

Trained physicists are able to work it all out on paper (I'm not such a person, of course). Alex Kenis didn't stumble upon a great discovery, he just demonstrated what is known, although as noted above, the results of his testing doesn't really match the math.

[bbsailor]

The ellipse of string motion indicates that both horizontal and vertical motion are present, generally in different amounts and not vibrating in the same phase. The rotation of the ellipse indicates that the phase relationship changes with time. This is complicated; I think it might mean that if the horizontal motion is detected significantly by the pickup, you should hear the harmonic content changing as the ellipse rotates, causing reinforcement/subtraction. I have never noticed such a thing, and so maybe the horizontal is not detected so well as this experiment indicates.

Another sort of test would be to build a pickup with a slot for insertion of a blade. You could insert a full blade as usual, or "bladelets" of different lengths under the strings, varying from less than the diameter of a pole piece on up. You would listen for differences, and measure the spectra of string harmonics. Because you are just looking for different ratios of harmonics you could use a normal complement of strings in the measurements, picking for carefully and repeatedly.

Mike,

Here is a quick experiment that you or anyone who has access to an oscilloscope or a PC USB Oscilloscope can do to observe horizontal and vertical string motion effects.

1. Attach the oscilloscope to measure the pickup output.
2. Set the oscilloscope to an appropriate vertical range to see the full amplitude of the Peak to Peak string output.
3. Pinch and release the string right above the neck pickup magnet and pull up about .125 to .25 inches depending on the string action to not dampen the initial string vibrations buzzing against the frets.
4. Observe the first few oscillations of the string and see how quickly the peak decreases and harmonics change as the string vibration decays.
5. Pinch and release the string again right above the magnet of the neck pickup and now pull the string sideways the same amount as in step 3 (above).
6. Observe the string output as in step 4 (above).
7. Do steps 3 and 5 (above) in different places along the string and observe for differences.

You will see the biggest difference in the very early string attack. This has implications for how you hold the pick either strumming with the pick perpendicular to the guitar body top or hold it at a 45 degree angle or pick the string at different places from directly above the active pickup to away from the active pickup. Play in the upper register on the neck and move your picking location to hear how that affects your sound.

When playing with other instruments you may want to fill open musical spots in a more rhythmic way and accentuate the strum peaks or you may want to add some clipping to sustain a louder sound for more melodic or saxophone-like musical segments.

We can measure the effect and explain the technical reason for the "why" but in the final analysis the ear is the final arbitrator within the context of the total musical expression.

If anyone does this experiment, please post your results or observations.

Thanks

Joseph J. Rogowski

[John Kolbeck]

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





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".