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Post by antigua on Aug 30, 2017 0:03:48 GMT -5
I've finally prototyped a means of getting a fairly reliable "pluck" to replace the exciter coil (like an eBow). The problem with a coil driving a constant vibration in the string through an oscillating magnetic field, set to half the frequency the guitar string is tuned to, is that it creates a situation which never truly exists (unless you use an eBow) where the steady vibration of the string is maintained through a particular kind of energy input at a particular location along the string, as apposed to an attack and decay of an actual string pluck. When the magnet got really close to the string, it would interfere with the movement of the string in a way that wouldn't occur in practice. The problem with plucking with a regular guitar pick in hand, in case someone isn't aware, is that it introduces a number of variables that are hard to reproduce consistently, such as precise plucking location, precise displacement of the string and a precise break angle on the pick, all of which have substantial impacts on the harmonic content produced by the string. With such a large margin for error, you could only test for things where the variance was substantially large than that margin, which excludes much of what is worth testing. This plucker, as depicted below, is made of two Popsicle sticks, a bolt and a few nuts, with the parts held together with epoxy. The construction is secured to the face of the guitar, and the string is drawn in between the nuts, and suspended there with a needle that is fed down through the nuts, which serves as a pin. When the needle is pulled away quickly, the string releases. With this setup, the amount of displacement, and the angle of displacement are fairly constant, much moreso than plucking the string manually:  Here is a sample recording of some plucks of the D string. You can see some variation in the overall amplitude presentation, but the peaks are far more constant than I've achieved with previous techniques. The harmonics profiles seen in the spectrogram are especially consistent.  I think I can improve on this rig by using smaller nuts, or something similar, that decreases the amount of play in the needle / pin. I'll also try a dulled needle, to see if a rounded pin makes for a more consistent attack. But overall, this approach represents a very cheap, DIY means of creating uniform string movement for a variety of different test scenarios. |
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Post by wgen on Aug 30, 2017 7:29:58 GMT -5
I've finally prototyped a means of getting a fairly reliable "pluck" to replace the exciter coil (like an eBow). The problem with a coil driving a constant vibration in the string through an oscillating magnetic field, set to half the frequency the guitar string is tuned to, is that it creates a situation which never truly exists (unless you use an eBow) where the steady vibration of the string is maintained through a particular kind of energy input at a particular location along the string, as apposed to an attack and decay of an actual string pluck. When the magnet got really close to the string, it would interfere with the movement of the string in a way that wouldn't occur in practice. The problem with plucking with a regular guitar pick in hand, in case someone isn't aware, is that it introduces a number of variables that are hard to reproduce consistently, such as precise plucking location, precise displacement of the string and a precise break angle on the pick, all of which have substantial impacts on the harmonic content produced by the string. With such a large margin for error, you could only test for things where the variance was substantially large than that margin, which excludes much of what is worth testing. This plucker, as depicted below, is made of two Popsicle sticks, a bolt and a few nuts, with the parts held together with epoxy. The construction is secured to the face of the guitar, and the string is drawn in between the nuts, and suspended there with a needle that is fed down through the nuts, which serves as a pin. When the needle is pulled away quickly, the string releases. With this setup, the amount of displacement, and the angle of displacement are fairly constant, much moreso than plucking the string manually: Here is a sample recording of some plucks of the D string. You can see some variation in the overall amplitude presentation, but the peaks are far more constant than I've achieved with previous techniques. The harmonics profiles seen in the spectrogram are especially consistent. I think I can improve on this rig by using smaller nuts, or something similar, that decreases the amount of play in the needle / pin. I'll also try a dulled needle, to see if a rounded pin makes for a more consistent attack. But overall, this approach represents a very cheap, DIY means of creating uniform string movement for a variety of different test scenarios. Now this is really, really fantastic man...Congrats! |
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Post by newey on Aug 31, 2017 20:05:41 GMT -5
Antigua-
JohnH and others around here have discussed the desirability of a uniform way to pick a string for testing purposes. But you're the first to actually do something about it, AFAIK.
You truly McGyver'd it, and I mean that as a compliment.
wgen-
For future reference, when you use the big "Quote" button in the corner of a post, you reproduce the entire prior post, diagrams and all, inserted in a box at the start of your reply. There is no need to do so, and it means the res of us just have to scroll down that much further to read what you have to say.
Rather than quote the whole post, you can quote the pertinent portion to which you are responding by selecting the text you want to quote (i.e., highlighting it), and copying it. Then, paste the text into your reply and click on the little quote button which resides next to the smiley face button in the toolbar at the top of your reply box. This will then insert the BBC code "quote" tagging around your selected text.
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Post by ms on Sept 1, 2017 13:05:03 GMT -5
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Post by antigua on Sept 2, 2017 14:20:42 GMT -5
For some reason it looks that way zoomed out, but zoomed in, the transient doesn't have a real distinctive look to it. I'm "plucking" near the neck pickup though, where as you test plucked near the bridge. I think the movement before the transient is vibration caused needle pulling away. The width / frequency of those initial movements is at or near half of the fundamental.  |
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Post by antigua on Sept 2, 2017 17:34:32 GMT -5
Here is plucker mark II. It's the same idea, but with much smaller screws and nuts. The more narrow spacing makes it easier to get a consistent release, and is less cumbersome to maneuver in between the strings. I drilled a little hole into the popsicle stick, so the screw extend as far down as it can go, for extra stability. The Loctite five minute epoxy is very stiff and holds everything together rigidly. The nuts are all free spinning though, so they can be raised or lowered to suit the height of string.  |
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timtam
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Post by timtam on Dec 28, 2019 8:05:32 GMT -5
Just an FYI .... the single string plucker most commonly used amongst the academic guitar science crowd seems to be the wire break method, where a thin wire with known breaking force bent around the string is pulled on until it breaks, in order to excite the string in a reproducible fashion. Obviously rather tedious. eg
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Post by antigua on Dec 28, 2019 12:26:40 GMT -5
Just an FYI .... the single string plucker most commonly used amongst the academic guitar science crowd seems to be the wire break method, where a thin wire with known breaking force bent around the string is pulled on until it breaks, in order to excite the string in a reproducible fashion. Obviously rather tedious. eg
I tried this, and I couldn't get consistent results. IIRC I was using fine thread, and even the velocity with which my hand pulled away the thread made a difference. I would have to pull at the thread at a constant rate. No matter how careful I was, sometimes the string would displace more or less before the thread snapped, and it could be seen in in the audio waveform that the transient amplitudes had a lot of variation. I tried pulling it very slow and ripping it away very fast, and the fast pulling action actually made it less consistent. It might be that the thread varied in strength along it's length, or maybe there was some other variable that I wasn't keeping consistent, but I couldn't get it to work for me. It might be that a certain type of thread is required, too. Even with this pin scheme depicted above, it's important to pull the pin away at the same velocity every time. |
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timtam
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Post by timtam on Mar 15, 2020 22:53:02 GMT -5
For completeness of a review of automated (continuous) string pluckers, we could add the Gizmotron, although viability is somewhat uncertain ...
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Post by antigua on Mar 16, 2020 11:25:25 GMT -5
For completeness of a review of automated (continuous) string pluckers, we could add the Gizmotron, although viability is somewhat uncertain ...
That is really neat. At first I though it was the hokey guitar-piano device, but that looks awesome. One thing I found though, is that the decay pattern caused by the magnetic interaction between the strings and pickup is important, but devices like this and the ebow dont allow for the decay pattern to be observable. They can be switched off, but there's no transient. This device rattles the string, causing higher harmonics, but because the excitation is over the bridge, it still might not be similar enough to a "pluck" above the pickups to say that one is representative of the other. Picking closer to the bridge causes a higher and more uniform distribution of harmonics, where as picking in the center somewhere favors lower harmonics, and an uneven distribution of harmonic amplitudes. |
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timtam
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Post by timtam on Aug 7, 2020 4:01:37 GMT -5
D'Addario apparently has a strumming machine ...
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timtam
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Post by timtam on Apr 16, 2022 1:36:22 GMT -5
Another contribution to standardized strumming/picking methods ...
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Post by antigua on Apr 16, 2022 12:46:30 GMT -5
That's an amazing amount of work he has put into that test rig. I think he made a similar YouTube video and it got lots of views, so maybe it pays for itself. I have a $100 Chinese Telecaster that I was willing to risk scuffing up for experiments, but that Telecaster has on his workbench actually looks pretty nice, sad to see holes being drilled into it.
The only problem I see there is that he's pulling it manually by hand, if he pulls it faster, it's probably going to produce a stronger transient and transient harmonics then if he pulls it slowly.
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