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Feb 11, 2021 - 11:28:25 AM
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15 posts since 2/11/2021

I was setting up the intonation recently and found that the ideal bridge alignment, in order to get my intonation the 'most right'), I had to slant the bridge, so that the heavier strings have a slightly shorter length.

I haven't seen this a lot, would that be because some folks don't play up the neck that much? Or is it just my cheap banjo? ; )

Feb 11, 2021 - 11:44:30 AM
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ChunoTheDog

Canada

707 posts since 8/9/2019

There is only 1 correct place for the bridge. If that happens to be slanted, so be it.

I wouldn't call my 1928 no hole TB-3 'a cheap banjo', and my bridge needs a slight slant to bring all 5 strings to proper intonation.


Feb 11, 2021 - 1:08:08 PM
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13839 posts since 10/30/2008

Normally the thicker strings need a bit MORE length to note true. Which means slanting as in Chuno's photo. I slant my bridges a bit like that on some of my banjos.

Feb 11, 2021 - 1:19:23 PM
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Bill Rogers (Moderator)

USA

24583 posts since 6/25/2005
Online Now

I don’t think I’ve ever used straight bridge I didn’t have to slant. That’s why compensated bridges came about.

Feb 11, 2021 - 2:01:50 PM

Alex Z

USA

4188 posts since 12/7/2006

Wound strings have less stiffness than plain strings of the same diameter.  Therefore, it is possible that a wound 3rd or 4th string could end up shorter than a plain 1, 2, or 3 string.

It is also possible that the 1st string and the 5th string might require the same distance from the nut.  In this situation, if the intent is that the 1st and 5th be precise, then the 2, 3, and 4 will be slightly out.

There are multiple locations for a straight bridge, and none of them are all correct on all strings.  smiley   Which to choose depends on the player's toleration of intonation considering the style of play.

Feb 11, 2021 - 2:26:54 PM

15 posts since 2/11/2021

quote:
Originally posted by ChunoTheDog

There is only 1 correct place for the bridge. If that happens to be slanted, so be it.

I wouldn't call my 1928 no hole TB-3 'a cheap banjo', and my bridge needs a slight slant to bring all 5 strings to proper intonation.


 

Very nice banjo...if it works best with a slant, mine is just fine then ; )

I also play some lap steel and have had questions about intonation...on a lap steel, if you tune the strings properly open, they aren't always in perfect tune when sliding up the neck.  So I was asking a steel player about it and they basically seemed to say "that off tuning is part of the instrument"...so I was wondering if there are banjo players who share the same opinion.

Feb 11, 2021 - 3:56:47 PM

Jbo1

USA

994 posts since 5/19/2007

DarseZ , I don't know about banjo players, but I know a lot of fiddlers who seem to have that opinion.

Feb 11, 2021 - 4:10:58 PM

m06

England

9734 posts since 10/5/2006

With the open strings all correctly tuned check the harmonics at the 12th fret. Adjust the bridge position so that the open tuning and harmonic of each string coincide. This will typically leave the bridge at a slight angle.

Feb 11, 2021 - 5:18:48 PM
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13470 posts since 6/29/2005

The reason the bridge wants to be slanted is because the stiffer the string, the more it will fret sharp up the neck.  Since the third string is the stiffest one, that's the one that's the most problematic and has to be lengthened. 

You really want to slant the bridge from the first to the third string, have the 4th string roughly equal to the third, and have the 5th string roughly the same as the first—that's the way compensated bridges work.

If you were to fret the 5th string, you'd find that slanting the bridge would make it fret flat, but since most people don't fret that string it's not a problem.

A "moon bridge", while not as finitely tuned as a true compensated bridge, creates a slant from the first to the third string, and makes the fourth similar to the third. 

 

Edited by - Ken LeVan on 02/11/2021 17:19:42

Feb 11, 2021 - 6:59:23 PM

Bart Veerman

Canada

4893 posts since 1/5/2005

DarseZ: "I had to slant the bridge, so that the heavier strings have a slightly shorter length."

>>> it's hugely unusual for the heavier strings needing to be shortened - are you using nylon/nylgut strings by any chance?

Alex Z: "Wound strings have less stiffness than plain strings of the same diameter. Therefore, it is possible that a wound 3rd or 4th string could end up shorter than a plain 1, 2, or 3 string"

>>> No. Unless there's some weird reason, the lower strings always need to be lengthened. Look at the millions of acoustic guitars, the saddle is always slanted to lengthen the low strings, not to shorten them - banjos are no different in that respect.

Feb 11, 2021 - 8:01:54 PM

8370 posts since 8/28/2013

Alex Z: "Wound strings have less stiffness than plain strings of the same diameter. Therefore, it is possible that a wound 3rd or 4th string could end up shorter than a plain 1, 2, or 3 string"


Bart Veerman: "No. Unless there's some weird reason, the lower strings always need to be lengthened."

These statements are both basically true. Athough wound strings generally are more flexible than plain steel of the same diameter, the wound strings need to be of a greater diameter than the plain strings due to their lower pitch (and, consequently, lower tension), so the wound strings will still be stiffer. That makes Bart Veerman's statement true. And because wound strings will sound somewhat different than plain steel, many times they need to be made even thicker to match the plain strings tonally.

Feb 11, 2021 - 8:29:45 PM

Alex Z

USA

4188 posts since 12/7/2006

Guitar saddle is a good example.  In the "olden days," the saddles were slanted and uniform on the top.  These days -- at least on the Collings and Santa Cruz guitars we have, the saddles are slanted, BUT the top is compensated such that the plain 1st and 2nd strings have one slant, and the 3rd-6th strings have a different slant, and the 3rd wound string is shorter than the plain 2nd string, even though it is tuned lower and has a larger diameter.

By the time you get down to the 5th string on the guitar, it is longer than the 2nd string.  But the 3rd string is generally shorter than the second string on the more modern saddle top.

Now, it is true that the wound strings are lengthened in relation to the nominal scale, but it is not true that a wound string of greater diameter always has to be longer than a plain string of smaller diameter.  Heck, the .020 wound 4th string on the banjo ends up shorter than a .013 plain 3rd string.

Maybe the qualifier here is "in relation to the nominal scale," in which case I would agree with Mr. Bart.  Really, even a straight bridge is "compensated" by being placed farther from the nut than the nominal scale, although it is not differentially compensated string to string.

Feb 11, 2021 - 10:52:43 PM

Bart Veerman

Canada

4893 posts since 1/5/2005

Alex wrote: "Really, even a straight bridge is "compensated" by being placed farther from the nut than the nominal scale"

Thanks Alex, this is the most delicious way I've ever heard it explained smiley In all fairness though, a bridge is just a bridge, the thingie that holds up the strings - in the case of a guitar, what actually gets compensated is the guitar itself often because of improper placement of the bridge or the improper location of the saddle's slot in the bridge. Yup, that's why you see the compensating file/sandpaper offsets to correct for the proper string length on the saddles. I'm guessing though that these filed intonation compensations are along the about-this-much lines of approach as it is a PIA to slacken the strings so you can remove the saddle to tweak it a little more and then reinstalling and retuning routine. Each mass-produced instrument simply couldn't be expected to have undergone a thorough setup like that.

Anyways, DarseZ asked what's up with his banjo and he did mention "cheap banjo." The came-with-the-banjo OEM bridges on instruments in this instrument category often are very intonation un-friendly and that would easily fit in the "weird reason" category. Other reasons could be a flaky, uneven thickness/gauge (especially nylons/nylguts) of a string, or even a [temporary] hearing problem.

The wonderful thing about trying to correct/tame intonation issues is that it's a whole lot easier to please the human hearing than it is to satisfy math/physics theories and/or oscilloscopes.

Keep in mind: the human hearing is not designed to be an absolute measuring device like an oscilloscpe. Instead, by design, it must adhere to these three criteria that are in constant & continuous service: Perception, Interpretation and Evaluation. This plain and simple means we hear what we want to hear and it's a totally personal thing because everybody's PIE is different smiley

Many of you have experienced personal examples of this: you tune and play your instrument and after a bit, you hand it over to someone else - the very first thing they do is to re-tune your "out-of-tune" instrument while to others, it sounds perfect from both players wink

Wow, it's really cool to talk about intonation issues without getting into the compensated bridge debates smiley

Feb 12, 2021 - 2:19:25 AM
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141 posts since 7/14/2017

quote:
Originally posted by m06

With the open strings all correctly tuned check the harmonics at the 12th fret. Adjust the bridge position so that the open tuning and harmonic of each string coincide. This will typically leave the bridge at a slight angle.


I think Mike mis-typed - the open string and its 12th fret harmonic will always be the same note but an octave apart.

What you need to check is the 12th fret note against the 12th fret harmonic. If the fretted note is sharp, the bridge needs to move back a little, if flat, forward a touch.

As others have written you won't get it right for all the strings, so you need to find a compromise position that's close enough for what you play.

Edited by - Profchris on 02/12/2021 02:20:23

Feb 12, 2021 - 5:54:18 AM

15 posts since 2/11/2021

quote:
Originally posted by Bart Veerman

DarseZ: "I had to slant the bridge, so that the heavier strings have a slightly shorter length."

>>> it's hugely unusual for the heavier strings needing to be shortened - are you using nylon/nylgut strings by any chance?

Alex Z: "Wound strings have less stiffness than plain strings of the same diameter. Therefore, it is possible that a wound 3rd or 4th string could end up shorter than a plain 1, 2, or 3 string"

>>> No. Unless there's some weird reason, the lower strings always need to be lengthened. Look at the millions of acoustic guitars, the saddle is always slanted to lengthen the low strings, not to shorten them - banjos are no different in that respect.


That's interesting...I found that the bridge had to be slanted with the thickest strings being shorter.  But now I'm going to check that again!  It wouldn't be the first time I figured wrong.  Thanks for your feedback

Feb 12, 2021 - 8:27:32 AM

8370 posts since 8/28/2013

quote:
Originally posted by Alex Z

Guitar saddle is a good example.  In the "olden days," the saddles were slanted and uniform on the top.  These days -- at least on the Collings and Santa Cruz guitars we have, the saddles are slanted, BUT the top is compensated such that the plain 1st and 2nd strings have one slant, and the 3rd-6th strings have a different slant, and the 3rd wound string is shorter than the plain 2nd string, even though it is tuned lower and has a larger diameter.

By the time you get down to the 5th string on the guitar, it is longer than the 2nd string.  But the 3rd string is generally shorter than the second string on the more modern saddle top.

Now, it is true that the wound strings are lengthened in relation to the nominal scale, but it is not true that a wound string of greater diameter always has to be longer than a plain string of smaller diameter.  Heck, the .020 wound 4th string on the banjo ends up shorter than a .013 plain 3rd string.

Maybe the qualifier here is "in relation to the nominal scale," in which case I would agree with Mr. Bart.  Really, even a straight bridge is "compensated" by being placed farther from the nut than the nominal scale, although it is not differentially compensated string to string.

 


A lower tuned string with a larger diameter can easily still need to be shorter. Lower pitch means less tension; thicker diameter means more tension. Those two factors can combine differently, so that even a wound string might be stiffer than a plain string. It's just not as simple as "wound strings are more flexible." They aren't always, if they are carrying more tension.

There can also be a mechanical limit to the diameter of the core wire in relation to the heaviness of the wrap that can be wound on it (too small a core can break in the winding process or be unable to hold the added tension the winding adds when the string is brought to pitch. {The winding doesn't add any tensile strenth-it only adds mass.}). There are instances where the core wire may even  be  equal  to it's plain, unwound neighbor.

Feb 13, 2021 - 6:41:50 AM

Alex Z

USA

4188 posts since 12/7/2006

"Wound strings have less stiffness than plain strings of the same diameter."

I believe this is universally true for the musical instrument strings we are talking about, made out of the ordinary materials that they are.  It's the qualifier "of the same diameter" that makes it true.  (Probably could construct a wrap of flat-wound titanium welded to the core, or something, that would be an exception.smiley)

Now, whether the same string (wound or not) under the same, higher, or lower tension requires the same, less, or more compensation (meaning that the effective vibrating length is altered by tension) is an interesting question.  

Feb 13, 2021 - 7:21:35 AM

8370 posts since 8/28/2013

quote:
Originally posted by Alex Z

"Wound strings have less stiffness than plain strings of the same diameter."

I believe this is universally true for the musical instrument strings we are talking about, made out of the ordinary materials that they are.  It's the qualifier "of the same diameter" that makes it true.  (Probably could construct a wrap of flat-wound titanium welded to the core, or something, that would be an exception.smiley)

Now, whether the same string (wound or not) under the same, higher, or lower tension requires the same, less, or more compensation (meaning that the effective vibrating length is altered by tension) is an interesting question.  


That sounds good in theory, but it's not always a fact. A wound string with a steel core could certainly be stiffer than a plain nylon string. One must always take into account the wire or other material used to make the string, and there are, in fact, mixtures of nylon or silk and steel strings used in sets. It's also entirely possible for two wound strings of the same overall diameter to differ in stiffness due to the size of the core wire, even when steel is used in both cases. 

There is nothing simple at all about musical instrument strings. There are formulas for calculating tension, but the formulas for stiffness (which figures into "inharmonicity") are rather vague, and usually include a "fudge factor." The problems involved get even more complicated when one considers tone quality, player preferences, and longevity. Wound strings deteriorate because unlike metals suffer from electrolytic corrosion. The windings corrode to the core (much like your "welded titanium" and can become stiffer than a plain string faster than one might imagine.

Also, if you are talking the same string (and not the same string diameter) under the same tension, it should be obvious that it would require the same compensation if no other factors are changed. A string can't suddenly become stiffer (even wound strings take some time before they start corroding). If you are talking diameter, but one being wound and one being plain, then a wound string should require slightly less compensation than a plain string, if it is, in fact, less stiff.

Feb 13, 2021 - 8:41:42 AM

Alex Z

USA

4188 posts since 12/7/2006

"A wound string with a steel core could certainly be stiffer than a plain nylon string."

C'mon G.  We're talking about 5 string steel string banjo strings.  E.g., plain 3rd versus wound 4th.    I'd run out of bytes in the computer putting in all the qualifiers. smiley

Question is:  Same string, different tensions.  Same compensation or no, and in what direction?

Our Steinway uses the same string for different notes, although the speaking lengths are different.  Does that tell us anything about the relative tensions?

Edited by - Alex Z on 02/13/2021 08:44:17

Feb 13, 2021 - 9:59:17 AM

74230 posts since 5/9/2007

The slanting of the bridge longer on the 5th string side is for making the 3rd string longer.
In my compensated design the 4th string is the shortest or nearest to the neck for correct intonation along the entire neck.


 

Feb 13, 2021 - 9:10:17 PM

8370 posts since 8/28/2013

quote:
Originally posted by Alex Z

"A wound string with a steel core could certainly be stiffer than a plain nylon string."

C'mon G.  We're talking about 5 string steel string banjo strings.  E.g., plain 3rd versus wound 4th.    I'd run out of bytes in the computer putting in all the qualifiers. smiley

Question is:  Same string, different tensions.  Same compensation or no, and in what direction?

Our Steinway uses the same string for different notes, although the speaking lengths are different.  Does that tell us anything about the relative tensions?


The discussion may have started with steel strings, but it certainly hasn't precluded nylon. There have been others who have brought up nylon besides myself.

You question about "same strings" was, in my opinion, not very clearly worded.  I will now say that if the same string is under the same tension, nothing changes. More tension on that string would probably mean "stiffer" thus more compensation; less tension would be the opposite of more.  However, strings do not always behave the way we'd like. I'm sure many people have experienced the difficulties of accurately fretting a string that's too slack.

The speaking length of piano strings of the same diameter determines (along with the pitch) the tension on that string. The idea is to have as similar a tension as possible, but with some other caveats. The inharmonicity of a given string and its neighbors both close and distant also has to be figured into the scaling because of the tuning of octaves to one another; more so than on a banjo with it's more limited range. There is also a change in the strike point of the hammer as the pitch goes higher (this is to achieve a more even tone quality).  Most pianos also have a slight decrease in string tension as one goes up the scale, and due to size limitations, the tenor range where the plain strings end, also has a decrease in tension. 

I could, as you mention with qualifiers, run out of bytes discussing piano scales and their whys, wherefores, similarities and differences from one another (believe me, I've had much experience re-designing bad piano scales and know quite a bit about both plain and wound string foibles), but this is a discussion about banjo bridges and string compensation, not piano strings and how they work. There are, of course, some things that apply, (the wire is basically the same, just larger in diameter) such as wound string stiffness vs. plain, and how tension affects that stiffness, that tone quality and evenness must be figured into one's dealings with both instruments, but there are enough differences to not bother with comparing the piano, with it's fixed bridge and built in string scale, to the banjo, with it's moveable bridge and players' choice of what strings he or she wishes to use.

Edited by - G Edward Porgie on 02/13/2021 21:14:17

Feb 14, 2021 - 7:27:21 AM

Alex Z

USA

4188 posts since 12/7/2006

Same question, simplified:  Suppose a string  requires 1/8" of compensation if it is tuned to B.  If the same string is tuned down one step to A, does it require the same, less, or more compensation, than 1/8"?

Does the correct answer to the above question depend on whether the string is plain or wound?

Feb 14, 2021 - 10:31:04 AM

8370 posts since 8/28/2013

quote:
Originally posted by Alex Z

Same question, simplified:  Suppose a string  requires 1/8" of compensation if it is tuned to B.  If the same string is tuned down one step to A, does it require the same, less, or more compensation, than 1/8"?

Does the correct answer to the above question depend on whether the string is plain or wound?

 


Lowering the pitch of the same plain string would mean less tension and thus less stiffness, so theoretically less compensation. I doubt that a one step lowering would really make enough difference to warrant a compensation change, however. The tension/stiffness change of one musical step is pretty negligible and wouldn't produce a compensated pitch change that a human ear would even notice. 

A wound string would most likely respond about the same, but wound strings tend to be a little trickier to figure. There are some differences in the vibrational tendencies of a wound string. (I don't wish to get into that, though, as it only serves to complicate the issue and is probably meaningless to this question.)

In the long run, it's likely that a properly compensated bridge, although perhaps not perfect (what is?), will serve the vast majority of a banjo players' needs, and certainly the number of rave reviews and pro builders' uses more than proves this. If a bridge only compensates to within one cent of perfect intonation, there isn't an ear in the human race that will ever hear that the pitch is still slightly off. Our ears simply aren't that sensitive.

Feb 15, 2021 - 10:14:35 AM

Alex Z

USA

4188 posts since 12/7/2006

"Lowering the pitch of the same plain string would mean less tension and thus less stiffness, so theoretically less compensation."

Less compensation would mean that the bridge would be set closer to the nut if the string is detuned.  Easy to test.

Try it out.  Set the bridge to make the 1st string D perfect at the 12th fret.  Then take the 1st string D, and tune it down an octave below.  Then reset the bridge position for the 1st string.

Check which way the bridge has to be moved to maintain the intonation at the 12th fret.

Feb 15, 2021 - 10:40:16 AM

8370 posts since 8/28/2013

Taking the string down an octave is an entirely different thing than taking it down one step, as you asked about earlier. There is no way to accurately test a string that's been de-tuned an entire octave; the tension would be so reduced that it wouldn't even be tunable. It would be so slack, it would be like trying to tune someone's necktie.

I should have made it clearer that when I mentioned lowering the pitch, I meant lowering it by your original amount of one step, B to A.

Feb 15, 2021 - 3:38:05 PM

Alex Z

USA

4188 posts since 12/7/2006

OK.  1 step doesn't work.  An octave doesn't work.  What the heck works?  smiley  Are we being evasive here?  Try something in the middle.  You choose the interval.

The claim is that reducing tension of a string -- the same string -- reduces its stiffness and therefore reducing the  compensation needed.  Ain't my claim.  smiley

Cannot there be some way to test the claim?   If not, then it's only a conjecture, without evidence.

Alright, alright.  "Simon Says try an interval in the middle."  smiley

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