Official Luthiers Forum!

I know this information is probably out there in some form or another, but surely some of you will have this handy??

I would like to know what the "standard" angle of compensation is for several scale lengths.

Starting with a 25.34, 24.9, 25.5, 25.9

I will be making bridges soon with my new CNC router, and I would like to have this information so that I can make bridges that are scale lengh specific.

I am also interested in the split saddle compensation angles and sizes.

Can anybody point me in the right direction for this information?

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Reguards,

Ken H

Interesting, Ken....I never thought about having a different angle for a different scale length....I just thought it was standard and the adjustment was made on the bridge saddle or lowering or raising the action slightly....I hope someone comes foreward with an answer....Larry

shorter scales require more compensation. think about it; the shorter scale is stretchedthe same distance downward to the fret, but the increase in tension on the string is proportionally greater, hence more compensation is required.

if i remember correctly martin uses a 3* angle on their long scale instruments, but john hall or one of the other ex martin factory hands may come in to contribute first hand experience.

i compensate my bridges on the instrument, i.e., cut the slot, after the bridge is mounted, but then i am crazy....

You really can't say that there is a specific angle. String spread as well as scale length will change this arbitrary angle some. It is really a dimensional variance from E-e not a given angle. though once you have a standardized your sting spacing you could at that time tie this dimensional variance to an angle value. However if my string spacing was 2 1/4 and yours was 2 5/16 the angle would be different. Not by much but never less by some

   COMPENSATION 101
     Compensation in its simplest form is matching the scale length , that is static ( non changing ) IE 24.9 and matching the working length Dynamic ( constantly changing) and making them work together so your guitar is in tune all along the fretboard. In reality this isn't truly possible but you can get it close.
     There are a few systems the Feiton system is one of the best known. So you need to understand what happens with the string in relation to the scale length and the change with the height of the action height.
    String length is constantly changing when it is played. The arc created is longer than at rest. It is the energy that is dispersed by this action on the saddle that creates sound. The working length of the stings will vary by the strings diameter , alloy ,physical properties , and age as the temper of the string will change as it ( work hardens ) over time.
     The compensation of the working length of the strings across the gauge determines the angle of the saddle. Martin figured this to be about 3 degree. Gibson uses about 3 1/2.
    Now to add more stock to the pot is the action height. As the action goes high the strings will pull sharp. There is also compensation length , In most cases about .100 to .125 added to the length as determined by string gauge. The heavier the string the more compensation length needed.
     You can tweak this better still by compensation of the saddle for each string. While it may sound confusing after the first 100 set ups you will get the hang of it.
    A good tuner will sure help.
Hope I helped someone
john hall
blues creek guitars

I always figured that the saddle positions at each string were varied strictly to compensate for the way the string breaks off of the saddle. String vibration calculations assume that the end conditions are a perfect pin joint, with the string free to pivot freely at the end points. Heavier gauge strings want to stay straighter and light strings behave more closely to the way the calculations predict (they are closer to the theoretical pin joint situation).

I guess the question really boils down to this: for a given set of strings...if you string up a 24" scale guitar vs. a 25.5" scale guitar, is there more deviation from E to e on one than the other?

I wouldn't expect that the physics governing the string vibration change substantially through the relatively small range in scale lengths that are commonly used on any specific group of instruments, be they steel string acoustics, basses, etc..

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http://www.PeakeGuitars.com

Cumpiano uses 1/8" slope over 3" length. This is a 2.39 Degree angle.

Michael,

Dont want to hijack this post but wondering if you would be willing to provide more information on how you do your saddle slotting after it is mounted. Do you use the Stew Mac jig? I bought the Stew Mac intonator kit which I haven't used yet and considering the saddle slotting jig. Any thoughts?

I just did my first with the StewMac jig.  I made an adapter to take the PC310 router.  It worked well.  It's a little flimsy. If I was doing this on all instruments I'd make something beefier.  I think David Collins posted a while back on a beautiful one he made.  I used a length of 1/8" square steel bar (from Ace Hardware) crowned on one side to represent the saddle and moved it till everything intonated well.
Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I just read about this and was wondering that myself. Glad this was posted.

I didnt mean to stir up anything except maybe some deep thought. I have bought saddles (Martins) that have deastically different angles of compensation. I had assumed that some of these were for their 25.34 scale and some for the 24.9 scale and that was why they were different?? I know when I bought my Martin D35 they told me that it wouldnt sound right with anything except medium guage strings. I dont know if this was because of the compensation angle of the saddle or for some other reason. It does play mighty loud with medium strings, but plays super easy and sweet sounding with SP lights on it too.

It only stands to reason that differing lengths of strings would require diffing compensation points. I had hoped that someone before me would have "done the math" and could tell me what these differences are. I had not even considered the differing guages of strings into the equation, but this gives me another line of saddle slots to cut if it requires any change.

 

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Reguards,

Ken H

when i first learned to do individual string compensation we used short bits of brass rod of varying diameters. now i use the s-m tool and it works well.

i do use a wider than normal saddle.

the jig is a simple one i made myself.