NO! For a given set of strings, scale length and tuning, the string tension is ALWAYS the same regardless of bridge height, relief, humidity, whathaveyou.Originally Posted by
Hammer, I'd say you need a new nut.
NO! For a given set of strings, scale length and tuning, the string tension is ALWAYS the same regardless of bridge height, relief, humidity, whathaveyou.
Hammer, I'd say you need a new nut.
Perhaps the string tension difference may be minor. Break angles multiply the tension. The photo does not show a tall nut. How would the nut grow taller?
Forward relief makes a nut seem taller, requires the bridge to be taller, and makes cross picking and double stops a chore because of high action on the upper frets, like described. A flat adjusted neck requires a taller nut, lower saddle, which does equal less tension. Also, the fingerboard is from Stew Mac, and probably not cut for the 14+ scale length he's at. A tall nut is good...
david blair
Looking at the photo it sure looks to me like the D and A strings are bearing somewhere in the middle of the nut. That's where I'd start.
The slots in the nut are very good. I have a 10x loop so I can look at them very closely. The last contact point of the strings and the nut is right dead on the fingerboard edge of the nut. When the nut is not shimmed up with the paper strips, the strings are within a couple thousandths of the first fret when fretting between the 2nd and 3rd. I don't believe you can have the action any more perfect at the nut.
I cut an old nut this weekend so that it hung over the fretboard by about 0.020". It only changed the intonation slightly on the first couple of frets, but made things sound very different as doughoople suggested it might on the first page of this thread.
I would still like to hear what other folks are measuring for their actaual distance from the front of the saddle to the nut vs. the actual scale length their fretboard is cut to.
Some one measure their best mandolin and tell me how far the first, 12th and bridge are from the nut. My contention is that the first and 12th won't correlate to the same scale length the bridge is actually at. In other words if you actually put a bridge at 13 7/8" from the nut it will not intone even close
Cheers,
Pete
I don't want to be a jerk mr knowitall, but you're just wrong. Break angles do not "multiply tension". The pitch of the strings, the scale length and the gauge of the string COMPLETELY determine the tension. Take a look
here. If your mandolin is in tune, the tension is the same whether the bridge/nut/action/relief is high/low/tall/anything. Increasing the break angle does increase the FORCE the string applies to the nut/saddle, but the TENSION is unchanged. A small amount of relief gives you the lowest possible action without buzzing. A tall nut is bad. It throws off your intonation at the first few frets and makes it harder to note them too. What's good about that?
Sting! It's alright, we're all mandolin family here.
I still contend that his string tension is amplified by the longer scale length and the resulting higher action. I also ask that you consider some effects of forward relief to be a taller nut, higher action between the seventh and 15th frets, and a taller saddle height. All of these add up to poor intonation Sharp on 1-5 resulting from increased string tension of the longer scale length, and difficulty of noting frets 7-17. Especially double stops and cross-picking patterns. The following is pasted from the D'Addario website.
The ideal scale length is of course twice the length from the nut to the twelfth fret.
String tension is determined by vibrating length, mass, and pitch. The string diameter alone does not
determine a string’s tension. By using different raw materials (nickelplated steel or phosphor bronze, etc.)
or by varying the ratio between the core and the wrap wire, two strings with the same diameter, tuned to
the same pitch, could have two different tensions.
There are many factors other than string gauge that determine the actual and perceived string tension
on your instrument:
• Scale length, or the distance between the nut and the saddle. The longer the scale, the
higher the tension is for the same string tuned to the same pitch – for example, a standard
FenderTM guitar at 251⁄2” scale has more string tension and will feel stiffer than a standard
GibsonTM 243⁄4” scale guitar, even if both are tuned to the same standard pitch.
Some players adjust for this by using slightly heavier gauges on shorter scale guitar than on
longer scale guitars.
Mandolin = 13 7/8”
Mandola = 15 7/8”
Mandocello = 25”
Mandobass = 42”
• The flexibility of the instrument top and neck.
• The string break-angle at the nut and saddle/bridge.
• String height or “action” as adjusted at the saddle.
• Truss rod adjustment (neck relief).
Note: Before deciding on a string gauge, be sure your instrument is properly “set up.” Unusually high ac-
tion can change the way the string tension feels and can also result in poor intonation.
How to Measure String Tension
String tension is measured in pounds of pull per string. When all of the tensions of each string are added
up, you get the “set tension” for that set. If, for example, you want to change the tuning of one string, you
should try to select a string gauge that will offer a similar tension to the string you are replacing, but can
be tuned to the desired pitch.
david blair
David what does your mandolin actually measure from the nut to the 1st, 12th and bridge saddle? What is the actual height from the strings to the 1st, 7th and 12th frets? Give us an actual example that can be compared to.
When you say longer scale length, higher action and more forward relief what exact measurements are you talking about.
My mandolin, with frets set out for a 13 7/8" scale length doesn't have a high action (1.75mm at the 12th fret), doesn't have any relief (just a few thousandths between the 1st and 12th frets) and has the lowest possible action at the nut with out any string touching another fret behind one that might be fretted.
What is different between my mandolin and the theoretical one of that scale length, or are all mandolins like this and intone with the bridge further back than the theoretcial scale length would suggest and quite sharp on the first few frets?
Pete
It is normal for the actual distance between the nut and bridge to be a bit longer than the theoretical scale length but the excessive sharpness on the first few frets is not normal unless the strings are pressed down all the way to the fretboard.
There's once key phrase in that D'addario excerpt
High action or excessive relief will certainly make it FEEL like there's more tension in the strings, but it's really just that you have to push the strings further, which is more work for your fingers. The string tension is fixed. I'm really not trying to bust your chops or anything, but a lot of people read these discussions and when someone says something that contravenes the laws of physics I feel the need to correct them so the cafe isn't responsible for spreading misinformation. Words like tension and work have very specific meanings and when they are misused it leads to confusion.
Now to relief: The things you're worried about "taller nut, higher action between the seventh and 15th frets, and a taller saddle height" are the result of too much relief, lets call that a bowed neck. A bowed neck is obviously not optimal. A very small amount of relief lets the strings vibrate without buzzing on frets 7-15 or so. This lets you push the envelope and bring the strings closer to the fretboard, ie lower action. Once the neck is bowed beyond the small relief needed to let the strings vibrate, you start running into the problems you describe.
Pete, I always take a hair off the nut end of my fretboards to help with intonation. It looks to me like you could make a nut that would overhang your fretboard, if you wanted to try it (making a nut is harder than it looks, by the way). Just having skimmed this discussion, it sounds like your relief, action, and nut height are fine, and assuming the Stew-Mac fretboard is slotted correctly and if the bridge is position so that the twelfth fret is an octave above the open string (no, the bridge won't be at its theoretical position), the only other culprit is the nut. I'd first check to make sure the strings are bearing at the front edge and not farther back, and then I'd experiment with an overhanging nut or some simpler substitute.
I do think a lot of mandolins have intonation problems that go unnoticed. I find that the traditional saddle compensation is always completely wrong for J74s, but you find it used on the majority of instruments (opening a whole 'nother can of worms).
Andrew Mowry
Mowry Stringed Instruments
http://mowrystrings.com
Also visit me on Facebook to see work in progress and other updates.
Yes sir,
When I measure from inside edges saddle being zero, I have 13 7/8. The seven falls noticeably over the 12th fret.
How's it going?
david blair
David it seems you speak in tongues. The only problem being, there doesn't seem to be anyone around who can interpret
I have to side with the laws of physics and thereby with Markishandsome.#That being said, the D'Addario website is still accurate. It mentions perceived tension. Higher action increases the pressure required to fret. If the higher action is the result of a steeper break angle at the saddle, it will increase the pressure on the saddle (and thereby the top plate) too. Note that high action (at the fret board) in and of itself does not mean higher pressure on the saddle. That would depend on the neck angle (and thereby the break angle on the saddle.
I think we have to be more precise when talking about things like "action" to comment on the effects of "high action."
I'm not a luthier, but high action at the fretboard due to too much neck relief would cause the problems you're seeing IMO. As many have suggested, I would focus on the nut and the neck relief.
Good luck.
Don
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Sorry I'm so cryptic. I'm trying to say that measuring from the edge of the saddle to the edge of the nut (inside edges) I have 13 7/8". With zero at the saddle end, the seven marker of the tape measure falls over the the 12th fret wire. So, from nut edge to 12th is 6 7/8', and an even 7" from there to the bridge. Seems that if you had these measurements in common that the frets would have to be in the right place. Anyone reading is more than welcome to help explain this for me.
Are you having any success?
As far as the string tension discussion and my ideal set up, I like minimal forward relief. I play j75's and #like to cross pick, sometimes above the tenth fret or higher. For my style of playing the the setup I described earlier is comfortable. Others players trying my instrument unanimously agree.
Anyway, I have been having similar intonation issues and wanted to help.
david blair
Nut to saddle = 13.875"
Nut to 12th = 6.875"
This would suggest that your fingerboard is slotted as a 13.75" scale length per the calculator posted earlier, not 13.875".
I've been trying other strings, with no significant change in the intonation on the first few frets. #I'm on a set of Thomastic mediums right now that "sound" wonderful even though the tuner suggests that they are still off by 10 - 15 cents on the first two frets. #They aren't bluegrass strings though and won't rattle anyone's cage at a jam
Pete
Some of you folks are forgetting that when a string is pressed down to the fret the entire length of the string from the tuning peg to the tailpiece stretches, not just the length between the bridge and the nut. Because of the friction over the bridge and over the nut you tend to get three different rates of stretching along the length of the string. A high break angle causes more friction than a low break angle and that is the reason the break angle can affect intonation.
Wow, I can't believe how timely this thread is. I've been playing on an F-5 with either medium or heavy (J74 or J75) strings for as long as I've been playing. I just received a L&H style B that appears to have been in a time capsule for the last 80+ years as everything on it is as new from the factory. I don't believe that this one has been played but a few hours in its lifetime and looks to still have the factory set-up from the 1920's.
While I was thrilled to have stumbled on such a pristine instrument, I was really disappointed in how out of tune it sounded. I adjusted the non-compensated bridge to the best of my ability and installed a new set of strings (Calace by Dogal RW92) and still could not get the instrument to play in tune.
Adjusting to playing light gage strings with an attention to playing with a delicate touch has cured my problem for the most part. Although, it's still not perfect, I've eliminated 'driver error' to the best of my ability. Thanks for starting this thread as when I take it in for set-up work, I will be more informed as to what to ask about (ie. check the nut, frets and compensated vs. the non compensated saddle.
Thanks, this is such a great resource. You guys are the best!
And now for today's weather....sunny, with a chance of legs
"Give me six hours to chop down a tree and I will spend the first four sharpening the axe." - Abraham Lincoln
Can you back this up or is it just your intuition?
I just tried picking behind the bridge while doing a big bend between the bridge and nut and head an audible change in pitch. So I'll grant you that something is happening, but I don't buy the whole friction argument. I just don't think the strings are actually sliding around in their slots. I'd think that the tension in all parts of the string is the same and increases a bit when you fret down. What I mean to say is that before fretting the tension in front of and behind the nut is say 20 pounds and fretted BOTH go up to 20.1 pounds. So I guess i disagree with your assertion that there are "three different rates of stretching."
I love these sorts of threads (even though I know I come across as a jerk) because they get my brain working and I usually learn something interesting about my instrument. Far more stimulating than "what brand of strap do you use".
No intuition involved. Pretty hard to test on a mandolin without changing tailpieces though. You'll need a few more decimal places as well.
The concept of a frictionless bridge and nut may work in theory but frictionless? I don't know of any material that is frictionless.
Care to clarify what is involved then? I never said the nut or bridge was frictionless. Rather I'd think that the friction would in fact be far too high for the strings to be sliding around in the slots due to what we agree is a small increase in tension. And even if the strings were free to slide around, the difference in tension on either side of the nut/bridge would resolve itself pretty quickly. I'm still pretty confident that the tension in all parts of the stings is equal. I also seem to recall Bob Bennedetto calling the idea that the afterlengths effect the intonation "hogwash". If you can suggest a test that would prove otherwise I'd love to hear it.
This isn't something I just came up with. It has been known for a long time. People have been inventing and patenting solutions for this situation since the early 1900's.
Do some research.
I assume the inventions you are referring to are things like the "frequensator" tailpieces they used to put on archtop guitars. When was the last time you saw one of those on a high-end instrument? People invented a lot of useless junk in the 1900s that we know recognize as being based on pseudoscience and intuition. The research I have done (read a couple books and of course the cafe) has revealed a strong consensus rejecting the idea that the afterlengths have anything to do with intonation. Your defensiveness and refusal to provide any evidence, sources, or ways to test your hypothesis don't make it easy for me to take your position seriously.
Your expectation that I would take the time to write a book here on this forum is unreasonable. This isn't something that can be fully explained in a few paragraphs.
Your refusal to accept commonly known information makes discussion impossible so I shall stop.
What discussion? All you've been doing is insisting that you're right while insulting me at every turn. That's not a discussion. I've read a lot of these sorts of thread here at the cafe and have seen ideas like yours regarding afterlengths and intonation dismissed by professional builders and repairpersons who were kind enough to take the time to explain themselves. I've never read anyone who seemed to know what they were talking about who agreed with you. Doesn't sound like "commonly known information" to me. If you can't be bothered to explain yourself, why should I take your word for it over that of the many other people who have?
I really have tried to be polite here, and I am sorry this got a little ugly.
Friction in the nut can cause tuning problems. The tuner has to overcome the friction in the nut to raise the tension/pitch of the section of string between the nut and bridge. A common example is tuning a string up to pitch, then playing it for a while, the pitch goes slightly sharp as the tensions in the different sections (string post to nut, nut to bridge) equalize. Steeper break angles cause more friction at the point of contact, which is generally the nut but also the saddle.
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