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I've located my bridge and have taped around it to mark it's location. We will probably use both medium and light strings on this guitar (14 fret 000). I personally use medium strings but my daughters will often use this guitar (especially till I've built them an even smaller guitar) and they will likely want light gauge strings. So a question before I proceed.

Is compensation independent of string gauge? I'm guessing it is and is more a function of action height over the fretboard (meaning the further you stretch the string down to the fret, the more compensation that's required). I've read values from 0.100" - 0.125" have been used for compensation (even 0.150" for some hard pounding bluegrassers). I at first thought that probably less compensation was used for lighter strings and more compenasation for heavier strings so used 0.116" to the center of the saddle (lengthwise and depth-wise) but I'm unsure if that's the best approach. I believe David Collins mentioned in a post using 0.110" string compensation. Any thoughts on compensation as a function of string gauge? I want this to be an easy player so do NOT want a high action.

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Formerly known as Adaboy.......

Sorry Darrel i cant help
Does anybody leave routing/chisiling the saddle slot till the final finish ?
eg. making a "setup saddle" that rests on the unrouted bridge

I havent really done numbers
but i would have guessed that compensation would vary with
bellying of top and streching of the strings and whatever else
... insert corrections where im wrong


do you guys use a piano tuner to do the final saddle profile
id love to read some tips
thanks

Darryl: The standard width 3/32" saddle(if there is a standard width)leaves very little room for location error. One of the main reasons that I use an extra wide saddle,.200 plus.This allows for errors and extra room for getting the compensation where I want it . Think your set back should be OK but look for other feedback as I have not measured for a while. I use a story stick and only use 25.4 lenght so have a stick with a hook that catches on the nut end of the fingerboard. At the bridge the stick is marked with knife cuts for the high E and the A strings.The cuts mark the forward edge of the saddle slot. I find this allows easy setting and locating.Changing string gauges may require different settings in theory,I have changed gauges without it bothering me.Have noticed that extreams of action can cause an intonation shift requiring work.Good luck setting her up.
Tom

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A person who has never made a mistake has never made anything!!!

I use an Ibex fret rule to set the scale length and compensation...works out to about 0.125 for compensation. A luthier friend with 40 years under his belt gave me this tip..when he's working with scales he not used to, he uses an end jig that fits centered on the end pin hole,...kinda like a trapese tail piece. 6 holes drilled in the thing so you can string the guitar up and move the bridge around to get it precise. Also ...I used the 0.150 number on my last guitar for compensation (so far all I do is short scale), and it came out spot on. I have used the StewMac Saddlematic unit to good results. This thing ads .60 to the treble side , and 0.150 to the bass side. I find the saddlematic and the Ibex fret rule both add up to the same result really.

I guess when discussing compensation distances, one should note where these measurements are taken (high E, Low E, middle of saddle etc.) and note if the compensation includes the compensation built into a sloped saddle. Seems discussing compensation to the middle of the bridge takes the saddle angle (or slope) out of the equation.

Following David Collins suggestions in some old posts, it appears that 0.110" to the middle of the saddle is roughly equal to 0.060" to the middle of the saddle at the high E which allows for 0.040" compensation 0.020" forward of the middle of the saddle. I'm currently setup for 0.116" of compensation to the center of the saddle (centered in both axis).

Would sure like to hear some experienced opinions discussing if string gauge affects compensation or not.

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Formerly known as Adaboy.......

Double check your measurements, it sort of looks like th bridge is pretty close to the soundhole. This really might mean nothing as the soundhole might be further back than normal. But it looks closer than normal to me...

Compensation is relative to the scale length as well as (to some small degree) the gauge of sting. Heavier gauge strings excert more tension when tuned to A440 than light gauge strings, which pull up the top more which can roll the bridge forward more (depending on the bracing and bridge plate and saddle height). But it's all a system. Longer scale length with light strings might have the same compensation as a shorter scale length with medium strings...

It's been so long since I did the math though....I've got my scale lengths set up on a go/no go gauge so that I don't have to worry about it any more. My bridges can only go in one spot with my jigs.

If cutting the slot after the bridge is glued on, might want to think about getting Stew-Mac's "The Intonator" as this will really help you dial in the intonation right.

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Rod, the sound hole is oversized at 4.25". The scale length is the standard Martin long scale of 25.34".

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Formerly known as Adaboy.......

I'll try once more.

Anyone change the string compensation based on string gauge? If so, what compensation do you use and how much do you change it? I'm using the Martin long scale of 25.34".

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Formerly known as Adaboy.......

I just use the stewmac bridge position figures from their fret calculator.
This gives a length for High and Low E which IMHO is the best way to set up the bridge rather than centre and relying on the saddle slope being correct.
NOTE that the measurements are to the CENTRE of the slot not to the front edge.
Make sure you use the actual measured scale length (nut to 12th X2)
I cant help on the difference between mediums and lights.

Darryl, you know what my experience is, so take this fwiw. Compensation has a lot to do with string gauge. If it didn't, compensated saddles wouldn't look the way that they do. thicker strings start to actually vibrate farther from the contact point on the saddle, so they need to be set farther back to make up for thickness.

Here's what I would do. Use the stew mac info, just like Jeff said, but try to engineer it so that your saddle is positioned so that it will be in tune with the medium gauge strings that you prefer. If you can, make it so the peaks are farther back on the saddle.

If you want, make a second saddle for light gauge strings. Or, just put light gauge strings on your medium-gauge-compensated-saddle and see if your daughters care...

There might not be an exact answer to your question about light vs medium string gauge compensation, other than "a little bit more." As Siminoff says ("The Luthier's Handbook"): "Since intonation correction is a factor of string gauge, string scale, and action, there is no formula I can provide to simplify finding the correct intonation correction location for each string."

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"...you have to get over your strict adherence to your largely imagined notion of absolute perfection..."

That would seem to me to be the most sensible suggestion I have read on any intonation thread.

So does anybody do this?

And if not, is it just because it has never occurred to them, or is there another way which gets superior intonation results ?

Both the stewmac innotator (for a bridge fixed in position but unslotted)
and the use of a temporary tailpiece with an unglued bridge can work for that approach.
But you must get the action spot on rather than a little high or these approaches will give too much compensation.

I really dont see the need unless you are doing something unusual with scale length such as a fanned fret arrangement.

Hey Darryl,

Here's my take on this. I don't think you need to change anything special regarding saddle position/compensation in relation to string gauge. No guitars are made for just one specific string gauge (at least regarding compensation).

That said, if you really want to make something adaptable, then make a saddle shim that you can take off when using medium strings and Bob should be your uncle! Medium strings having more tension, they vibrate with less amplitude, thus allowing you to lower the action. By doing this, you reduce the impact on the tension when freting strings, and consequently the need to compensate more.

And keep in mind that a prefect intonated guitar exists only in Alice's wonderland. You will get it (almost) perfect and the next day, it's gone! Not to mention different finger pressure from one player to the other, or the same player but before the third beer and after the third beer, and so on and so on...

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Well put, Alain.

Hi again
Alain wrote..
(And keep in mind that a prefect intonated guitar exists only in Alice's wonderland. You will get it (almost) perfect and the next day, it's gone! Not to mention different finger pressure from one player to the other, or the same player but before the third beer and after the third beer, and so on and so )

I would have thought that after a week of settling the intonation would be more consistant
Doesn't nearly everyone here build for a specific string guage and action in mind ?

Hello Gents,
I have nothing to add to what has already been said.
However, I have always thought that "hybrid" guitars add an interesting light to the compensation subject. i.e. Martin's Ian Anderson model that has a two different saddles (one for SS and one for NS). I would assume this is to battle the exact phenomenon you are speaking of.

Also, is this a good time to bring up compensated nuts and the ingenious systems that have been invented using them? If not, please disregard.

Hans

Might be better in a separate thread. but -
I've been compensating nuts by slanting the FB end at right angles to the "high" FB edge, (at the bottom edge of the zero fret position) and my ear likes the result.
Actually I will start a new thread.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Well, it will be consistant, but to a certain extent.

I may have exagerated a bit when I said that the intonation would be gone the next day. My point is that I think it's useless to reach for an intonation that is absolutely spot on, meaning 0% difference between the harmonic and the fretted note. Just by varying finger pressure, you can change a note by a few %. Add to this the variation of finger pressure between different players, the variation of action due to change of humidity, the different behavior of old strings versus new strings (etc., etc.) and you get yourself in a situation where it's impossible to always have a 0% delta on a regular basis.

So yes, you can get a certain consistance with your intonation, but give or take a few percents...

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

I measure my compensation at the first string, front edge of the saddle. I use 0.080" for medium gauge with 7/5 action, and 0.065" for light gauge, same action.

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John

Hallelujah! That is the info I was looking for. Many thanks John!

Thanks to everyone else for your thoughts as well. Sure nice to bounce questions off of you.

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Formerly known as Adaboy.......