Myth/science In Lutherie

[Mickguard]

First column(original min. break angle) shows the longer string requires more distance to reach the higher pitch. That makes sense and is what I expect.

Second column(after angle is added) shows a decrease in distance to pitch.

Okay, lemme see if I'm reading this right...

In this case, that opens up the possibility of 'dosing' the guitar by adjusting the angle for each individual string. It would follow that each string --for a given gauge along a given scale-- should have an optimum length and angle, right?

Staggered tuners achieve that to a certain extent. A redesigned headstock with different tuner placement might do a better job of it.

Another thing: on a typical drop down headstock, the string trees effectively serve the function of the headstock angle, right?

So it follows that one could use the placement of the string tree to add or subtract the angle (or shorten or lengthen the string)?

[ToneMonkey]

The more physics related classes I take, the more I look at every thing as forces in the form of vectors(and the more I realize many of my previous beliefs were simply false ). It really helps to take the guess work out of something. Then again, sometimes it's useless and feel becomes overwhelmingly more important. I think these types of situations require equal attention from both a theoretical and practical point of view. At least that'll save you the most time.

peace,

russ

It's a spring/mass/damper system

[fryovanni]

Brian d- I pulled the string to position and held it there for a fair period of time. As far as deflection during fretting altering the effect of dead string length. I think they are independant factors, but altering either will effect results. The independance seems to make sense to me because when tested the action is similar, but intonation varied slightly.

ToneMonkey- And.....

Mick- Maybe, Until you can identify and understand the effects of the differenct factors it is hard to say. As far as string trees VS angled headstock. At a glance you will be increasing friction and possibly adding to the deflection thats hard to say (if it is even a factor on elasticity). Good thoughts.

Peace,Rich

P.S. ToneMonkey/ other smart fellas- If string tension is equal to elasticity multiplied by length extended beyond natural length then divided by it's natural relaxed length. (Hooke's law unless I am mistaken). Would this possibly explain the reason behind (or quite possibly play a role in) the variations I am seeing in my test. I am not intending to say friction is not a factor, I am just trying to validate the possibility that we may be altering the elasticity of the string. Opening it for consideration.

[badsnap]

[fryovanni]

"Rich...forgive me if I seemed arrogant or insensitive"

Not a thang. I took nothing negative from it at all.

The Length and Mass as it relates is clear at this point (at least in my mind). The tension(as it relates to elasticity) and friction are the points I am still trying to resolve.

Peace,Rich

[brian d]

Brian d- I pulled the string to position and held it there for a fair period of time.

well that answers that question.

As far as deflection during fretting altering the effect of dead string length. I think they are independant factors, but altering either will effect results. The independance seems to make sense to me because when tested the action is similar, but intonation varied slightly.

You could test it by taking away the effect of fretting deflection using harmonics or a slide to "fret" the note at the 12th fret without introducing any deflection. I wonder if there would be a difference in intonation with different dead string lengths or headstock angles under those circumstances.

In any case, the experiments you're doing show what really happens. The theory may give some answers of why it happens, but knowing that increasing headstock angle decreases deflection needed for whole step pitch raise is much more important than knowing why.

Regards,

Brian.

[badsnap]

Interesting thought brian...Rich, when you changed the headstock angle, which direction did you need to adjust the bridge in order to get the intonation correct?? I did not record this info (fool!!) when I tried it. If you're game (since you have the test jig) perhaps you can try a 3rd angle and see if the intonation follows the string length or is the opposite. My neck is off the guitar I used and I'm working on it this weekend so I can't repeat my experiment. But, as Brian said, you could perhaps use the harminics so you won't need to adjust intonation after the angle change and see if the harmonics all track in the same direction. We could then extrapolate which direction the bridge would need to go and see if they follow the bend distance. Just a wild thought...Rog

If I get done with the neck soon (replacing truss rod and and fret board) I'll try to remember to repeat the experiment and record ALL of the data...Rog

[GregP]

Did I miss something amidst all these posts (great thread, btw... lots of different people involved)?

Intonation needs to be adjusted because the length of string from nut to tuners has changed, no?

[fryovanni]

Did I miss something amidst all these posts (great thread, btw... lots of different people involved)?

Intonation needs to be adjusted because the length of string from nut to tuners has changed, no?

I am going to re-do this test. I want to confirm that my findings are correct. A LOT of these adjustments are very small, and although my measurements differed it was not by much. Rog is really making me want to do this to confirm I the findings are accurate.

Greg- Yes, the extra length at the headstock should require a modification. However (and this is big!), I had about 6" of difference(total string length) in the initial test and only had a difference of .06" in intonation. That is 1/100th of an inch per inch of new length (that new length is very small less than a quarter inch, because I offset the pivot point). I also had to re-adjust the length from the tailpiece to the bridge (although it should be pretty much identical if I did it right). I don't know if my rig is going to prove accurate when we are talking about less than 2/1000's of an inch. Especially when I am dealing with the slight arching that is now occuring at he nut and saddle. Maybe this is going to be beyond my capacity for accurate results.

Peace,Rich

[GregP]

I don't know about the specific numbers, but it stands to reason that there won't be HUGE differences in the intonation. After all, with the right height of nut and well-adjusted action, the downward pressure of the string, especially at the 12th fret where intonating is done (unless you're using a technique I don't know about), produces an extremely small increase of string tension in the first place. Adding 25% more string length means that the entire tension is only being increased by 25%. That's tension, not pitch. Let's say that the first test had you pitching up by 5 cents (barely detectable by the human ear), and the second one (longer string length) had you now pitching up by only 4 cents, you're not going to very easily or accurately measure, and the change in intonation would be such that few people would even bother. No one in the world can hear a 1-cent difference. I'd put a 1-cent test in front of even these legendary folk with "perfect pitch" and challenge them to notice a difference. Heck, variations in how hard you're fretting your string will produce more than a 1-cent change.

Now, those maths are not tested and confirmed ( ) but I erred on the side of generosity instead. There's often only a 1-cent difference between fretted and unfretted, meaning that the increased string length would be particularly unnoticeable.

Greg

[boomerlu]

Perry: I actually did consider string lengthening, I simply did not mention it in my model because I knew it would unnecessarily complicate my argument.

And the reason I'm not actually going out and trying this stuff out is because I simply do not have the materials to do so.

As far as real world results vs theory:

I mean objective real world results. IE, spectrum analysis, not "Oh it sounds different!". Tension gauges and not "Oh, it feels different.", although feel is slightly less subjective than sound. The reason I brought up the importance of experiment is that there is NO WAY of knowing a priori (beforehand) the laws of our universe.

Just as an example, in physics there are like umpteen billion (exaggeration I know) theoretical models of how the world works. All of them reduce to our real world, based on what we know. Until we know more (through experiment) we can't verify or deny any of them. Theories are simply what are possible (since they are deductively valid), but not necessarily the truth.

Anyways, I'm glad we're getting a good debate.

[Ben]

Just as an example, in physics there are like umpteen billion (exaggeration I know) theoretical models of how the world works. All of them reduce to our real world, based on what we know. Until we know more (through experiment) we can't verify or deny any of them. Theories are simply what are possible (since they are deductively valid), but not necessarily the truth.

Sounds like you could be refering to a different kind of string theory there

[ToneMonkey]

P.S. ToneMonkey/ other smart fellas- If string tension is equal to elasticity multiplied by length extended beyond natural length then divided by it's natural relaxed length. (Hooke's law unless I am mistaken). Would this possibly explain the reason behind (or quite possibly play a role in) the variations I am seeing in my test. I am not intending to say friction is not a factor, I am just trying to validate the possibility that we may be altering the elasticity of the string. Opening it for consideration.

I dunno mate, that's why I've been quiet in this thread. Generally I view vibration the same as I would aerodynamics.............if you think that you've pictured it in your head correctly, it's probably wrong.

I only piped up with the spring/mass/damper system comment so that people could try and model it in their heads a bit better. Basically (and this is a very general assumption), everything vibrating is a spring/mass/damper sytem. I'll draw up a couple of pictures if I get chance to today (just got back from a meeting so I may be busy for the rest of the day). Just picture a mass on the end of a spring, the spring attachend to the bottom of the damper and the damper attached to the ceiling. The mass is the force, the spring is the string and the damper is the forces causing the string to slow it's vibration (such as air resistance, smaller vibrations acting past the nut opposing the vibration of the strings, even the vibration of the nut and bridge having an adverse effect.

Basically, I couldn't say what's happening, but I'd think that the vibrations of the string behind the nut may very well have an effect on the string. Also when reading through this thread, I think it may help if people picture the string as being elastic. Sorry I can't be any more help, but I'll keep my eye on this topic and may well pipe up again if I have anything useful.

Ben - Super Symmetric String Theroy by any chance? - Have a read of "The Elegant Universe" by Brian Green, good book

[Ben]

Indeed... never read that book though. My Dad's probably going to the library soon, so I might tell him to keep an eye out for it.

I wish I'd been keeping up with this thread as it developed really- it seems a little daunting now to catch up with 8 pages of essay like posts

[fryovanni]

TM- I agree using SMD theory as a foundation for the model is good. The tricky part is that it is very dynamic(FSMD). If we model it based on an open string being plucked that is one thing. Bend the string and you have a new starting point. I guess the task is to make sure we grasp all the changing dynamics so that we don't leave something out of the equation(s).

Peace,Rich

[Ben]

I've skimmed over most of this thread, but not read it all in depth, because its pretty long...

What is the main 'goal' that people are trying to achieve?

Or is there no specific goal- and its just a general discussion? (I'm sure someone refered to a goal in another post somewhere though..)

[SwedishLuthier]

What is the main 'goal' that people are trying to achieve?

Fryovani, guided by Perry, has showed, through his experiments, that there are factors in building that many, I am one of those, has regarded as pure myths. I had never ever considered the dead length of the string to have an impact on how the guitar would behave and how it would feel to play.

I think that that is the goal. Understanding the factors that affect the guitars performance and feel.

I haven’t chipped in on this because I have had too much work to be able to do the same experiments that Rich has done, but I will follow in his path as soon as I have the time. I think only reading has learned me a lot, but doing it myself will make me really understand the factors that has been explored.

Now we only have to lure Perry into revealing more of what he has found out. Not the results, but directions to go with our own investigations.

[GregP]

I have to (to some people's annoyance I'm sure) add that the length of dead string is something I mentioned right on page 1, sans experiments. It might not seem as overt because I didn't use those terms, but when I referred to the "length" of the string, given the same scale length of the fretboard, any additional length is by default "dead" string. So part of the thread is also discussing the "scientific" (using the term loosely because sometime's it's pure logic) reasoning behind why those experiments prove true.

Greg

[fryovanni]

I've skimmed over most of this thread, but not read it all in depth, because its pretty long...

What is the main 'goal' that people are trying to achieve?

Or is there no specific goal- and its just a general discussion? (I'm sure someone refered to a goal in another post somewhere though..)

[speal]

I couldn't help but post, having seen all the bad physics going on here. Let me start by stating my position: The tension on your string, assuming a frictionless nut and bridge, will be exactly the same at all places along the string.

Your spring is anchored at both ends, and somewhere in the middle, there is a pulley (frictionless, of course) that raises the height of the string. The angle between the two sections of string is the break angle of your neck. While the string exerts a downward force on this pulley, the pulley is not accelerating. F = ma, so if there is a net force on the pulley, it would HAVE to accelerate down through your neck and away from the string. The reason it's not accelerating downward is because the neck provides the necessary normal force to counteract the string pushing down. If the string tension and/or breaking angle is too great, the neck will snap. Otherwise, it'll just flex forward at the location of the nut until the force of the neck resisting the flexing is equal to the downard force on the nut.

So, tension is the same everywhere. Now, if you take friction into account, you will STILL find equal tension, except when bending. The force due to friction is defined as F = f * N, where N is the normal force between the string and the nut, and f is some constant of friction dependent on the nut and string surfaces. The friction force, when starting a bend, will point from the nut toward the tuners. The string will not move across the nut until the difference in tension between the lower (between nut and brudge) and upper (between tuners and nut) sections of the string is greater than the frictional force exerted by the nut. Once this force has been exceded, the string will all have the same tension everywhere. This happens because the friction constant of two surfaces once already moving is almost always less than that of the static frictional constant (before they're moving). When you release the bend, the opposite will happen. The upper string tension will be greater than that of the lower string tension as you release, but the tensions will equilibrate as soon as the difference in tensions is greater than the frictional force in the opposite direction (toward the bridge).

One thing you'll notice is that the frictional force depends on the normal force. The normal force is directly related to the breaking angle. A breaking angle of 0 degrees will have no downard force on the nut, and thus no friction. A breaking angle of 180 degrees will exert twice the tension on the nut. So, increasing your breaking angle increases the friction between the string and nut, and makes it more likely that your guitar will go out of tune after you bend. I haven't plugged in the numbers just yet, but I imagine the difference between a breaking angle of 11 degrees and 18 degrees would have almost no effect on your guitar's intonation after bending, since the friction constant for most nut materials is intentionally very low. You're going to make a much bigger difference (or, a noticible one) in intonation if you use a high quality bridge and tuners, and adjust your guitar's intonation properly.

If anyone reads this old thread and wants to see a diagram, I'd be happy to make one.

[Prostheta]

Okay, my little myth sarcasm *has* to be injected somewhere of course. You called a fire buddies!

"Tone is in the fingers"

Where? Do cleaner fingers mean clearer tone, like strings? Do denser, heavier fingers sustain longer? Does Ed Roman stock some US-made fingers I can buy, and why are Japanese fingers supposedly inferior? Does the fingerprint grain on fingers contribute to better note stability and purity? Do old slow-grown fingers sound better than fast ones? What's a better design - tendons through wrist or bolt-ons like Tony Iommi? Can I Tru-Oil my fingers? How far should I sand back my fingers before dyeing them?

All in good humour guys :-D

[Prostheta]

A real myth or perhaps scientific theory that I would love to be broached:

THE SPEED OF SOUND

Basically, sound energy propagating through elastic materials varies with the material density. This will obviously affect the tone of our instruments as resonances, internal reflections and phase cancellations will all come into play here. I understand that acoustic instruments are much better designed in terms of wave propagation for obvious reasons. Electric instruments however, seem to have a degree of faith in how the instrument will sound. A Les Paul is what I perceive to be a "slow" instrument in terms of propagation whereas a Tele is "faster".

Interesting variations which will undoubtedly affect this aspect of solidbody design are:

- dense neck laminations on neck-through instruments allowing vibrations to be unmolested by changes in material density between nut and bridge

- heavy top caps "tightening" the body sound slightly

- necks with differing fingerboard woods

- differing nut materials

As mentioned, a lot of this is taken for granted in lutherie and general instrument lore - how does it translate in the really real world however?

[erikbojerik]

I couldn't help but post, having seen all the bad physics going on here.

Thanks for posting that. A much better explanation of what I was trying to say many pages ago (more or less).

[VesQ]

Does a fat person have more sustain in his guitar that skinnier one ?

The answer is yes.

just get one these http://www.stringsdirect.co.uk/Catalogue/V...x?productId=406

and you don´t have to eat so many donuts.

[Robert Irizarry]

Does a fat person have more sustain in his guitar that skinnier one ?

The answer is yes.

just get one these http://www.stringsdirect.co.uk/Catalogue/V...x?productId=406

and you don´t have to eat so many donuts.

I'll have to disagree with you. Fat lacks resonance and dampens tone. What you really want is to be rail thin. Bone conducts sound far better than fat. You may also want to go that extra step and sandpaper down fat fingertips so you have bone on string. That way you can get that tone in your fingers to contribute as well. Not only do you not have to eat donuts, but you don't have to eat at all. That way you can literally be a starving musician and tell everyone how you suffer for your art.

Seriously though, those are just another take on Fatheads - brass plates you attached to the back of your headstock. Did anyone ever use those?

Regards,

Rob