Neck stiffness and perceived string tension, et al

[Howard Emerson]

Hi all,
Some of you may remember a thread titled "New D-28. Medium gauge strings feel really bendy and overly slack??"

Well I sent an email to Hugh Gilmartin at D'Addario (I have an endorsement with them, and have used their strings just about my entire guitar life) and he passed it on to their tech department. The question I sent included this portion of the thread:

Hugh,
"I have a specific question about string tension on a given scale vs perceived or actual stiffness..........Here's the crux in a nut shell:

Quote: Originally Posted by Aaron Smith

"Agree that the tension will be the same, but the stiffness may not be. Your friend's guitar may just have a more flexible neck than you're used to."

To which I replied to Aaron:

"Aaron,
So are you saying that if a gauge were placed against a given string, then forced sideways a specific distance (or to a specific pitch amount), that it would read differently on different guitars (same scale) owing to a stiffer, or less stiff neck, or looser bracing, etc?

If a human can feel it, is it a measurable thing?"

So here is the answer I got from Brandon Medici at D'Addario

Dear Mr. Emerson,
My name is Brandon Medici and I am one of the product specialists here at D’Addario & Co.

What I think you are asking is the difference between actual tension and perceived tension? Just to be clear, your neck ‘flexibility’ isn’t really (or shouldn’t be) factor in string tension. The amount, or more accurately, lack of ‘flexibility’ or give is so minute that it isn’t a factor.

Also, when mathematically calculating a string there is the theoretical, and there is the actual. The theoretical is where we, a string company, start, but it is just the beginning.

But to address your email – if a guitar has a standard scale length (25.5 is widely considered standard) and is tuned to a standard pitch, or to its designed pitch, then it will not vary in tension due to the neck material (again not enough for a human to notice or both quantifying).

There is the actual tension, of which we calculate mathematically, and perceived tension which is what you and Aaron I believe are discussing. Perceived tension usually is defined by the scale length, nuts, saddles, the ratio of other strings in the set, and the ratio of pounds of total tension between each string. I hope this clarifies a little for you and if there are any other questions please don’t hesitate to write."

So there you have it, from a fairly reputable source:-)

Truth is, of course, that I've always known that it has much more to do with the shape of a neck (and how the centerline passes through the hand) and how it fits a particular players hand, coupled with fret size. Even high action is not as much of a factor, provided the neck relief is correct. Two divergent lines are fine, but a straight line and a curved (neck with too much relief) line under it?? That feels totally unwieldy and plays very inconsistently.

My thanks to D'Addario for their timely reply!

Regards,
Howard Emerson

[Michael Watts]

Very cool! Thanks for that Howard

[robj144]

I believe what he is actually referring to when talking about perceived tension is torque. The longitudinal tension (theoretical tension in context which depends simply on the mass per unit length of the string and fundamental frequency) could be the same for strings on different guitars, but the act of pressing the strings to the fret board also relies on torque. Torque depends on the nut height, shape of the neck, etc., and this depends on the construction of the guitar itself.

[Howard Emerson]

Originally Posted by robj144

I believe what he is actually referring to when talking about perceived tension is torque. The longitudinal tension (theoretical tension in context which depends simply on the mass per unit length of the string and fundamental frequency) could be the same for strings on different guitars, but the act of pressing the strings to the fret board also relies on torque. Torque depends on the nut height, shape of the neck, etc., and this depends on the construction of the guitar itself.

Rob,
You forgot one of the most important issues: Leverage.

Ever try to drive a car where the seat is too far away from the pedals (especially the clutch), or too close, as the case may be?

The construction of the player's hand must be factored into the construction of a neck, but of course when you're dealing with factory made instruments, like D-28's, there is a pattern followed, so each one is very close to another one. Sometimes, though, the existing pattern just happens to fit somebody's hand, like a glove.

HE

[robj144]

Originally Posted by Howard Emerson

Rob,
You forgot one of the most important issues: Leverage.

Ever try to drive a car where the seat is too far away from the pedals (especially the clutch), or too close, as the case may be?

HE

Torque is leverage... it's the layperson's version of leverage.

[gitnoob]

I did a test a while back. There is simply no way either the neck or the top moves with the added force from fretting a string. So, I'm skeptical of claims that "feel" is affected by either neck or top stiffness.

Originally Posted by Howard Emerson

Even high action is not as much of a factor, provided the neck relief is correct.

This I disagree with. The force required to fret is highest near the nut. High action at the nut has a huge effect on feel.

[Howard Emerson]

Originally Posted by robj144

Torque is leverage... it's the layperson's version of leverage.

Hi Rob,
Ya know........as I walked away from the computer, I thought about my torque wrench (used for my lawn mower blade), and how it allows me to have more, er.......leverage........to a controlled point, of course.

Thank you for the information! I'm definitely a lay person when it comes to physics!

HE

[Howard Emerson]

Originally Posted by gitnoob

I did a test a while back. There is simply no way either the neck or the top moves with the added force from fretting a string. So, I'm skeptical of claims that "feel" is affected by either neck or top stiffness.



This I disagree with. The force required to fret is highest near the nut. High action at the nut has a huge effect.

I'm primarily referring to high action as a whole.

I absolutely agree with you that high nut action makes playing near the first couple of frets disagreeable.

Truth is, of course I never, ever, play without a capo on the second fret or higher.

Thanks for the correction.

HE

[robj144]

Originally Posted by gitnoob

This I disagree with. The force required to fret is highest near the nut. High action at the nut has a huge effect on feel.

Once again, this is a function of torque.

[gitnoob]

Originally Posted by robj144

Once again, this is a function of torque.

I agree, but I'm not sure that makes it any better.

Lower the nut slots as low as you can get them without buzzing.

[Howard Emerson]

Originally Posted by robj144

Once again, this is a function of torque.

Rob,
He's correct, though, because in the middle of the string it's easier to bend the whole thing, whereas near the termination points, it is definitely stiffer............but then I think to myself about that saying I read 'Give me a place to stand..........yadda............' and so I guess you have more 'torque' the further from the 'fulcrum', right?

HE

[gitnoob]

As long as we have a physicist here, we should also clarify whether string length past the nut/saddle affects feel.

Electric guitarists swear up and down that it does.

What's the physics? Strings are elastic, so having more material in "reserve" past the nut/saddle should make them more pliable, right? Longer strings at same tension == slinkier?

[robj144]

Originally Posted by gitnoob

As long as we have a physicist here, we should also clarify whether string length past the nut/saddle affects feel.

Electric guitarists swear up and down that it does.

What's the physics? Strings are elastic, so having more material in "reserve" past the nut/saddle should make them more pliable, right? Longer strings at same tension == slinkier?

I'd have to think about in more detail, but off the top of my head, I would say it does not matter. The forces from a torque point of view which are most relevant is the normal force produced by the nut. Making the string longer or shorter past the nut, does not change the position of the normal force. However, if I think about it more, maybe there's something else at play which I have not thought of just yet.

[Howard Emerson]

Originally Posted by gitnoob

As long as we have a physicist here, we should also clarify whether string length past the nut/saddle affects feel.

Electric guitarists swear up and down that it does.

What's the physics? Strings are elastic, so having more material in "reserve" past the nut/saddle should make them more pliable, right? Longer strings at same tension == slinkier?

I'm staying out of this one, although maybe I'll email the thread link to Brandon, and see what he has to say.........

Of course it would be interesting to do a blindfold test on one of those electric players by having them play, blindfolded, a guitar that has a locking nut. Have it totally loose when they start the test, then tighten it down, cut the excess string, from the nut to the tuners, off, and hand it back to them.

HE

[gitnoob]

Originally Posted by robj144

However, if I think about it more, maybe there's something else at play which I have not thought of just yet.

I think of it as a cable attached at an endpoint (nut) vs a cable attached at a farther endpoint past the nut. Friction at the nut should be a factor in pliability, I'd think.