Intonation

I have searched, but not found much on this subject.

So far, I have not made any attempt to compensate for intonation in my saddles. I shape the saddle evenly and try to glue the Bridge at the precise distance indicated in the plan.

(Incidentally, the plans I have seem to indicate measuring to the front of the saddle slot. Wouldn't it make more sense to measure to the center of the slot, assuming the saddle is rounded evenly, and that string would begin to vibrate freely from that point? But I digress.)

Would anyone be willing to describe the process of shaping the saddle to get proper intonation? I fear this may be trade-secret stuff, but I have to ask.

Am I correct that, technically, each different kind of string will require a slightly different adjustment?

Thank you,

Nelson

It gets even more complicated than that. Intonation and compensating for it is dependant on so many things that at best we can only get it close.

Things that affect intonation.

• String Type and brand (Different density and diameter)
• String Age (changes as they wear)
• Fret Size (taller frets and player technique may stretch string more)
• How hard the player frets (stretches strings more or less)
• Action (again stretches string more or less)
• Temperature and Humidity (strings may change response to either of these conditions)

David Hurd has a good info in his book "Left Brain Lutherie" and his article about placing the bridge.

This subject has been oft discussed on the forum, some might say discussed to death, but I still obsess a bit on compensation. All the things that Allen said apply and probably a few more that he forgot. It get complicated. But keep in mind that is will always be an approximation. A very, very close approximation, but an approximation nonetheless. There are posters on this forum that have studied the subject to a degree that always makes my head start to hurt.

To your question: Yes, you should measure to the center of the bridge slot which is the center of the saddle. You don't say what your scale length is which is important. I used to try and "compensate" my saddles to compensate for string diameter, but this was seriously dissed by those who claim to know so I quit. I still think it has merit, but what is the formula? Nobody has ever offered one because it depends. Now I just move the bridge back off a 17 inch scale by 3/32 with a straight saddle and you know what? all is pretty good on a medium/low action. I wonder sometimes whether this all starts to get a little OCD. Still I obsess to a degree. My latest obsession is no matter what calculations I do, the rotation of the bridge under a load is unpredictable because it depends on the top wood type, thinness and the bracing. I could lock the bridge patch and that would solve the problem, but what does that do to the sound?

Allen, thanks for the response. I will take another look at Left Brain Lutherie.

Sequoia, thanks as well. I am building tenors, so 17" and the plans do call for the same 3/32 compensation. I will continue to measure to the center of the slot then. I appreciate that clarification.

As far as filing the saddle to compensate for individual string intonation, well, I'll guess I have to decide if I want to try to figure that out.

Nelson

Filing the saddle differently for each string is fun, you shouldn't be afraid to try it. I usually add 2 mm to the front of the saddle and then file back another 1 or 1.5 mm for the C-string. I'll see if I can find a pic on my blog.

Smoke and mirrors... Use the scalel length to the front of the bridge to give your offset - assuming your saddle slot is 3/32" from the edge. With a nice wide saddle you have all the wriggle room you need

Also in your journey to becoming a more competent maker use trusted sources for your knowledge... there is a lot of well meaning mis advice to be had on special interest forums.

I individually compensate my saddles.

With a 3mm (1/8") saddle i can fine tune the intonation by about 15 cents, which is an audible amount. It's just science and not snake oil.

Like Allen has said, everything changes if you change strings etc.

I set it as good as I can (I shoot for within 5 cents of perfect) for the strings I put on and the action I set- change either of those and everything changes.

Try not to worry too much about it. Everything is a compromise even the fret placement can be different between scales. Most blues players for example bend the note on the third fret up slightly to get the actual blue note in the scale that got tempered down so that all scales coukd be approximated on the one fretted fingerboard.
I have heard that for ease of calculation frets used to be placed using the rule of 18ths, where each fret was placed an 18th of the way between the previous fret and the saddle, which is ever so slightly different from the current accepted model which works out the scale length , does a theoretical log based equal split and then adds an overall intonation adjustment which generally only gets checked at the 12th fret.

excuse my ignorance, but I'm trying to get my head round what's being said here. For a 17 inch scale e.g. the distance from the nut to the saddle centre is not 17 inches but 17inches + 3/32inches, so the nut to 12th fret is 8 1/2 inches and from 12th fret to saddle centre is 8 19/32 inches? Am I to attach my bridge so that the saddle slot centre is 17 3/32" from the nut, not 17 inches as I was thinking? Mike

mikeyb2 said:

excuse my ignorance, but I'm trying to get my head round what's being said here. For a 17 inch scale e.g. the distance from the nut to the saddle centre is not 17 inches but 17inches + 3/32inches, so the nut to 12th fret is 8 1/2 inches and from 12th fret to saddle centre is 8 19/32 inches? Am I to attach my bridge so that the saddle slot centre is 17 3/32" from the nut, not 17 inches as I was thinking? Mike

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Exactly. The scale compensation is added to the scale length as you surmised. Keep in mind that the compensated amount being discussed here is a rough approximation and will change with different scale lengths (different uke sizes). The shorter the scale length the more compensation will be needed. Also, the lower your action is the less compensation you'll need. With some strings you may need to individually compensate as well. Some strings rarely require it.
Once you figure out what works best for you make yourself a simple stick jig where one end sits in the nut slot and the other end into the saddle slot of the bridge for easier positioning.

Thanks Chuck, I'm glad this thread was started. It never occurred to me and I just assumed I was going to place the saddle at 17". I'm on my first uke build which is a tenor, so I have to start somewhere, without any previous know how. I wasn't intending to do anything like individually compensating the saddle slots,so 17 3/32" it will be with a straight saddle and I'll see where that takes me. Mike.

It will sound fine. And all things being equal yes, Pete is right (again! drat!), if the saddle slot is 3/32" inch back from the front of the bridge, measuring to the front of the bridge at 17 inches will give you the right approximate compensation. But why assume that? Measure to the saddle where the rubber meets the road and make no assumptions.

Moore Bettah Ukuleles said:

... The shorter the scale length the more compensation will be needed. ...

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I've come to the same conclusion, but want to add that it is a proportionally greater compensation, in effect leading me to add the same amount in absolute numbers. So I add between 2 and 2.5 mm on piccolos (280 mm scale length), sopranos (350 mm), and tenors (can't remember but around 425 mm).

OK. So here is a question: The thicker the string, the more compensation it needs or visa versa? Thus the thick C string needs to be set further back and the and the thinner string less so?

I'm a consumer, not a builder. What I want to say is based on measuring numerous ukulele's VERY carefully with vernier callipers while referencing Stewart Macdonald's fret position calculator.

Short answer to the OP. You measure scale length to the leading edge of the saddle slot. There is NO circumstance where you would need negative saddle compensation, UNLESS you got something else wrong. If something else is wrong, then fix what was wrong. If you measure the scale length to the leading edge of the saddle then you at least give someone else who knows what they are doing a fighting chance of getting decent intonation. If you build the instrument with the scale length measured to the centre contact point of the saddle then an experienced luthier has no room to adjust for correct intonation even if they wanted to without resorting to special saddles.

This is just a minimum position. Luthiers who know what they are doing will allow slightly more compensation at the saddle

Now I'm going to bitch.

Why doesn't everyone know this already? I don't want to point a finger just at the small luthiers. The big companies screw it up too. I've visited a well known Guitar company in Australia and pointed out to them that their ukuleles weren't being built accurately. (so I'm a jerk).

You guys need to collectively (at least) build a ukulele intonation test rig. Build your own even. Make it so you can adjust the nut AND saddle contact points in relation to various fret boards.

String it up, measure, adjust, measure.

Seriously guys. I pull out my tuner, rule and verniers when ever I try a new instrument seriously.

Now yes, perfection isn''t a reality. I know that , but you can get very close. If an instruments intonation is out by more than a few percent then I WILL be able to measure an error.

The simple answer for good intonation? Well apart from accurate fretting, the nut needs to be precisely positioned in accordance to the scale length, and the saddle needs a little extra length past the theoretical scale length position.

If you want to get serious you should carefully compensate the nut for the slightly different lengths that the angled strings induces.

EDIT: Theoretical scale length only works if you have theoretically PERFECT strings. Real world strings aren't perfect. Basically, the thicker a string gets the less perfect its vibration is so more compensation is required.

Rant over.

Anthony

Why are you measuring it? Can't you hear it?

Michael N. said:

Why are you measuring it? Can't you hear it?

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Yes I can hear it. I can clip a tuner on and I can measure it. The question then becomes, why is the intonation out.

You could simply throw your hands in the air and say, its a ukulele, get over it, or you can measure the instrument up and see if you can find the error.

OK, ukuleles being short scale instruments need to be built to a slightly higher degree of accuracy than a longer scale guitar, but its doable. What I'm ranting about is the lack of theoretical understanding in the whole industry. I'm not pointing the finger just at a few small scale builders.

Sure, the theory can get beyond me in a hurry too but the fact that some of this stuff isn't common knowledge for even small scale builders is an indictment. Apparently Martin built their guitars incorrectly for many years because ONE disgruntled employee was sacked and sabotaged the tools before he left. No one else picked it up for many years.

Ukuleles can and should be built with better intonation than most of them are.

Anthony

I don't really see the point of the measurements, the ruler and the vernier. As a user, if it didn't intonate to my satisfaction, I would simply put the Uke aside. Choose something else.

Michael N. said:

I don't really see the point of the measurements, the ruler and the vernier. As a user, if it didn't intonate to my satisfaction, I would simply put the Uke aside. Choose something else.

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Well as a user that's OK if you simply want to put the instrument aside. My first interest in this was to measure if the instrument was viable to fix or a complete waste.

My point in posting in the builders forum was, A, an attempt to get the OP on the right track, and B, an attempt to generate some interest in some "community development".

Anthony