Yowza. Until you mentioned this, I hadn't noticed quite how much dynamic range was in all those plots you posted!
Back in my grad school days, while studying differential equations and some famous solutions to specific differential equations used in science and engineering, I learned that all the vibrating modes of a circular membrane (uniform, weightless, perfectly flexible, etc) are described by a set of Bessel functions of the first kind (J_n) Fascinating stuff!
Pure math fairly easily predicts all the vibrating modes for membranes or thin plates that are circular, or square, or rectangular.
Other shapes are much harder. I think an an actual guitar top, with its complex shape, bracing, and glued attachments at the edges, is pretty much impossible to solve analytically (using only pen and paper).
But with a computer, solving for its modes numerically is probably quite easy with the right tools. I think I've seen something like this several decades ago. I forget all the details, but I remember that the guitar neck was the first thing to vibrate for a solid-body electric guitar (i.e. the bending mode of the neck had the lowest of all the mechanical resonant frequencies of the wooden structure.)
Instead of endless arguing about "tonewoods" on e-guitar forums, they probably should be arguing about "neckwoods"! 😀
Funny story: in college a friend gave me her brother's cast-off archtop acoustic guitar, a rather crudely made no-name one. The rather thick carved top had cracked almost entirely into two halves, which is why the guitar was being discarded.
My plan was to take it apart and use the neck to build a guitar, but first I played the broken archtop a little. It had a rather sad, nasal sound to it.
Then I cut the body away, removed the neck, and built a solid-body electric guitar around it. The only parts of the archtop guitar that I reused were the neck, the nut, the tuners (tuning machines), and the trapeze tailpiece. This was long before the Internet, so there was very little information out there that I could find. I made many poor decisions out of ignorance, but I did end up with a playable electric guitar.
Here's the funny part: that guitar had just a faint trace of the same nasal sound its progenitor archtop guitar had had!
Since the neck was the only part of the original guitar body that made it to the new one, that sad nasal sound must have come from the neck!
-Gnobuddy
Converted a plywood classical to steel strings. Needed a neck reset also, did a quickie. Could have used a little more tilt back but the guitar is playable. Not as horrifying as the bevels though.Clever, but also horrifying!😀
-Gnobuddy
So one thing I'm curious about; all the resonances measured so far seem to fall on the flat side of concert pitch. Intentional? The closest of the guitars I have around is the above Yamaha, with its 431Hz out of 440 value.
If that "big boom" landed precisely upon 220Hz, would it be desirable if the guitar bowled everyone over every time an A note was played? Granted, a vibrating string (with a bunch of harmonics therein) driving the bridge isnt quite the same as a pure sine tone.
I suppose I could always tune it to A @ 431Hz and find out for myself how it sounds. I just find it interesting all the guitars I've tested showing "the Yamaha 3 prong pattern" resonances are all flat to concert pitch.
If that "big boom" landed precisely upon 220Hz, would it be desirable if the guitar bowled everyone over every time an A note was played? Granted, a vibrating string (with a bunch of harmonics therein) driving the bridge isnt quite the same as a pure sine tone.
I suppose I could always tune it to A @ 431Hz and find out for myself how it sounds. I just find it interesting all the guitars I've tested showing "the Yamaha 3 prong pattern" resonances are all flat to concert pitch.
I've been desiring one of those Gibson Chet Atkins solid body nylons. I've had the finger on the button at least once, for one of the Epiphone variants. Unsure if I can do the 1.75" nut, wanting the 2" version - which never comes up. One did in England, 5 years ago... So I was thinking could I do a "fill in" of one of my $100 units, which is what appears to be what you've done just upstairs here. Is that solid?
Bumped into this searching for Yamaha G60A;
It looks like they're touting a frequency range between 0 and 5kHz as being "Enhanced" by their system. So clearly the waterfall analysis is something that would reveal differences in guitar performance regarding sustain because that's what the time axis is. Regarding REW, the guitar's body becomes the equivalent of the room, only the long reverberation times are desirable - if they're at the right frequency. So, two properties for the guitar body design to solve; resonate in tune with concert pitch and ring those notes over time. I'm sure dynamics, such as peak SPL when you really whack it and like a speaker, with the little microlevels of sound riding on a larger voice and be clearly perceptible.
Here's a question; those "auditorium" sized guitars - do they resonate at lower frequencies, or, not necessarily so? I wonder if there's an acoustic that has similar resonate properties to the Yamahas, but shifted down from 110/220/440 to 82/164/328? FAIK, it's not possible; the guitar would be so big you couldnt hold it.
It looks like they're touting a frequency range between 0 and 5kHz as being "Enhanced" by their system. So clearly the waterfall analysis is something that would reveal differences in guitar performance regarding sustain because that's what the time axis is. Regarding REW, the guitar's body becomes the equivalent of the room, only the long reverberation times are desirable - if they're at the right frequency. So, two properties for the guitar body design to solve; resonate in tune with concert pitch and ring those notes over time. I'm sure dynamics, such as peak SPL when you really whack it and like a speaker, with the little microlevels of sound riding on a larger voice and be clearly perceptible.
Here's a question; those "auditorium" sized guitars - do they resonate at lower frequencies, or, not necessarily so? I wonder if there's an acoustic that has similar resonate properties to the Yamahas, but shifted down from 110/220/440 to 82/164/328? FAIK, it's not possible; the guitar would be so big you couldnt hold it.
You do not want the resonance to fall on a note's pitch. When it does the energy is sucked out of the string fast and you end up with a wolf note, louder but little sustain. A guitar would behave more like a banjo.
The guitar is acoustic, I cut the offending bits out and added some linings to the cut areas and then glued on a sheet of spruce. It had a steel saddle holder that I removed and I filled in the slot so a saddle fits in and is angled to compensate the steel strings.
The ARE system is torrifying the wood. Some of the hemicellulose is cooked off and the wood is a little stiffer than it was before treatment. The wood is less subceptible to humidity and the increased stiffness allows you to make the top a little thinner. The less mass allows it to vibrate more freely.
The larger the guitar the lower the resonances with all being equal. But you can adjust the construction to shift them around. I have a 0 sized body that is tuned lower than a Dread. The thing is you do not necessarily want your resonance to 82 Hz. For one you do not want it tuned to a note frequency (as I said above). Also the resonance may be tuned to a frequency but the frequencies above and below the resonant frequency still gets "amplified". If tuned to 82, the bottom half of the resonance is wasted as you have no string frequencies there. Guitars are often tuned to about the G on the E string. Smaller guitars usually have the resonance shifted up, some up to an A.
I mentioned that three of my music buddies have Taylor GS Minis ( https://www.taylorguitars.com/guitars/acoustic/features/series/gs-mini )
These are quite small guitars, but still have a decent amount of bass, even unplugged - much more than you'd expect from such a small-bodied instrument. I wonder what tricks Taylor Corp. used.
Before buying a new guitar (acoustic or electric), one of the things I do is play every note in the guitars range, one at a time, from open low E to the highest fretted note accessible on the high E string, and listen carefully.
I find many acoustic guitars - at least in the price ranges I look at - will have some "dead notes" in the mix. Notes that have bad tone, or buzz, or lack sustain.
Those same problematic notes will, of course, also show up when you're playing an actual piece of music on the guitar that uses any of those notes.
I think many of these problems are caused by a guitar body resonance falling too close (in frequency) to that note. As Printer2 said, if there is a body resonance right on top of a played note, the results are usually not good. The "wolf note" can cause the bad tone, and the resonance sucks energy away, causing short sustain.
IME, among electric guitars, Stratocasters are particularly prone to these dead notes. I suspect that the vast sheet of thin cheap plastic sheet loosely screwed to the front of a 'Strat body flaps and flutters at many different frequencies, and that causes all those dead notes.
If you play a 'Strat unplugged, you can hear that it is acoustically much louder than other types of solid-body electric guitar. I think that big sheet of loosely attached thin plastic sheet almost acts like a crude banjo head, amplifying the acoustic sound, but also shortening sustain, and sometimes causing dead notes in the mix.
So there you go, we should be fighting flame wars over "toneplastics" and "neckwoods" on 'Strat forums, instead of "tonewoods"! 😀
-Gnobuddy
Taylor route's a channel around the edge of the top (underside of course) to have it act as a 'flexible' surround to give the guitar more bass. Some classical builders feather sand the edge of the top to do the same thing.
Found a picture.
My guitar tuner actually goes down to 430 Hz as an adjustment. I set it to 431 and tuned down the Yamaha G130A. Waaaay down, as it were.
To my ears, it's louder and sustains longer. The strings are so floppy, it's almost not a playable guitar anymore, so that kinda obscures the effect of the effort, though open Em sounds pretty interesting with a long, deep growl going on. You'd have to bump the gauge up of all the strings to actually play it at A430...
All these old classical guitars I have on hand measure even lower, maybe like A410. The G130A measures the highest of the bunch. I'm still intrigued by the behavior of the two Gibsons I owned back in the early 80s, with their perceived responsiveness to concert pitch tuning. Only 1k$+ each these days to find out / own such an instrument again!
At least it's easier to stiffen, than relax an existing mechanical structure, if that's something one could explore. Violins use sound posts; never seen such an idea used in a guitar. Must be a reason for that.
To my ears, it's louder and sustains longer. The strings are so floppy, it's almost not a playable guitar anymore, so that kinda obscures the effect of the effort, though open Em sounds pretty interesting with a long, deep growl going on. You'd have to bump the gauge up of all the strings to actually play it at A430...
All these old classical guitars I have on hand measure even lower, maybe like A410. The G130A measures the highest of the bunch. I'm still intrigued by the behavior of the two Gibsons I owned back in the early 80s, with their perceived responsiveness to concert pitch tuning. Only 1k$+ each these days to find out / own such an instrument again!
At least it's easier to stiffen, than relax an existing mechanical structure, if that's something one could explore. Violins use sound posts; never seen such an idea used in a guitar. Must be a reason for that.
The violin operates differently as compared to a guitar. The sound post fixes that point together and the top pivots at that point. A guitar would have a more limited bass response if it were made the same way.
https://www.classicalguitardelcamp.com/viewtopic.php?t=127669
Nevermind - I dont know what I had the guitar tuned to. I tried a second time, this time verifying the tuner set to 4-3-2 with my function generator set to 4-3-2. 1 cent off. Now the guitar doesnt tune anywhere near as low as - whatever it was I was doing before.
Inspired by the article I found; https://www.acousticguitarforum.com/forums/showthread.php?t=468828 and the remarkable coincidence this Yamaha G130A presents @ 431Hz.
Inspired by the article I found; https://www.acousticguitarforum.com/forums/showthread.php?t=468828 and the remarkable coincidence this Yamaha G130A presents @ 431Hz.
Here's an idea regarding an acoustic instrument's resonances. I read somewhere years ago that a good sounding instrument should have many resonances, and all at about the same volume. This description of a filter bank may be illustrative:
http://yusynth.net/Modular/EN/BANK/index.html
http://yusynth.net/Modular/EN/BANK/index.html
Glad you caught that!
I was wondering what had actually taken place. 431 Hz is only 2% below 440 Hz. One semitone is nearly a 6% change. So tuning down from A440 to A431 is only down-tuning by about one-third of a semitone. Very slight!
Most people (including most musicians I know) wouldn't even notice such a small tuning change at all. String tension will change so little as to be quite imperceptible.
Records made before we all had precise digital tuners are often off-tune by 2% or more. One example I happen to remember well is "Every Breath You Take" by The Police. It's supposed to be in the key of F, but is actually in no-mans land, about a third of a semitone sharper than concert-pitch F.
"Every Breath" was released in 1983. I've heard older music that's off-pitch by considerably more than "Every Breath". When playing guitar along with playback of an older song, I have had to tune the guitar half a semitone flat or sharp more than a few times. Sometimes a song that's supposed to be in G-major is actually tuned almost to Ab-major, or F# major, so I've ended up tuning my guitar almost an entire semitone sharp or flat in order to play along in tune with the recording.
-Gnobuddy
Ah! Thanks for that very interesting tidbit of information.
I wonder how much that reduces the strength of the top. As the years go by, will Taylor guitars with the thinned-down edge implode sooner than other brands?
-Gnobuddy
Interesting picture. I wonder where the wire goes that enters the wood just above the soundhole? A second "Dynamic body sensor"? I see how they ground all their strings. No piezo on this model!
That is a pickup for the strings.
"a Dynamic String Sensor® embedded beneath the fretboard"
https://www.taylorguitars.com/guitars/acoustic/features/electronics/expression-system®
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A lot of guitar players these days like to use loopers to create their music, and many thump out percussion on their guitar bodies to crudely simulate drum accompaniment.
I suspect that's the reason for the "Dynamic body sensor" in this particular Taylor guitar. 🙂
I kinda doubt that there would be an electronic "dynamic body sensor", but not an electronic sensor for the strings as well.
My guess is that the fatter grey (coaxial) cable connects to the piezo sensor for the strings. The end of the cable is obscured by the hand in the picture, so we can't see if there is a connector on it, or what it might plug into.
-Gnobuddy
It's located a long way from the usual places for a string sensor, no?
Assuming this guitar is not a left-handed model, that "dynamic body sensor" is located close to the upper edge of the body, in a
convenient spot for the player to thump with his/her hand to create percussive grooves to accompany their guitar playing.
You can see this technique in action about 14 seconds into this lovely loop by Peter Honore, aka "Danish Pete":
-Gnobuddy
No, electric guitars do have neck pickups. The Taylor one is a magnetic pickup although they moved away from it with the ES (2) version. The body sensor was put in place to get the top resonance contribution. Most players do not 'thump' their guitars, the acoustical sound was the main goal.
String pickup.
"our behind-the-saddle placement enables the piezo crystals
to capture much more output energy and produce a more
natural, more linear acoustic sound."
https://www.taylorguitars.com/sites/default/files/TG_Understanding_ES2.pdf
https://hazeguitars.com/blog/taylor-es2-piezo-pickup-balance
I've heard it, and am not a fan at all. It sounds like an electric guitar, not an acoustic guitar. It completely ruins the tone of the guitar.
I don't own any Taylors (too rich for my blood), but generally I appreciate the quality of their products. That magnetic pickup was a notable exception. I think it was a massive mistake.
No wonder they moved away from it. The wonder is that they ever used it at all.
Very interesting. The location is so near the sidewalls, and so far from the bridgeplate, or the common places where people used to position their Barcus-Berry Hot Dots. (Remember those?)
I remember reading about their piezo redesign in a fawning article in one of the guitar magazines.
Whatever pickup Taylor has in their GS Mini's sounds good to my ears. But IMO, the piezo pickup with the closest approach to the acoustic sound is Takamine's "Palathetic pickup": https://www.takamine.com/palathetic-pickup
My best acoustic is a Takamine with a palathetic pickup, and an onboard Cool Tube preamp (which contains an actual 12AU7).
I don't know if the tube's contribution to the sound is hype or not, but you can dial in variable amounts of the tube sound to mix with the solid-state sound. To my ears, mixing in some of that tube sound does do a very nice job of removing the last traces of piezo harshness (aka "quack"). It's a very good-sounding piezo pickup + preamp combination.
-Gnobuddy
Danny Wilding, a great flute player, who by his by own account, "Got thrown out of most of the studios in London" (prior to 1978..) explained to me that some producers purposely increased the speed of the analog playback tape machine to raise the pitch of recordings for a slightly different or "brighter" sound without requiring any tuning or key changes in the original performance.
Also makes it harder for other musicians to copy 😉
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