Intonation adjustment limits when tuning lower

[karaolos]

Hello, AGF!

I've been looking into what is necessary to adjust on a guitar, in order to set it up for tunings lower than standard. I understand that you'd have to modify the nut, if thicker strings are used. You'd also need to compensate for intonation at the bridge.

How low can you go, on a 650mm scale length guitar, before you can't adjust for proper intonation?
or
How low would it be possible, before you'd have to get a guitar that has been designed as a baritone?

Would it be easier to adjust a baritone to play slightly higher?

I understand that, not guitars behave in the exact same way... I just want to get an idea of what the limits are.

Thanks

[Fathand]

If thicker strings are used, resulting in similar to original tension, intonation adjustment should be minimal, likewise, if it is a nylon strung guitar.

If the guitar has a floating bridge, then intonation adjustments are easy.

It should be simple to test with steel strings. Buy a set of the heaviest strings you feel comfortable playing, maybe Daddario EJ 18, .014 to .059, String it up to your desired pitch and see how it intonates or if the strings get sloppy.

[karaolos]

Originally Posted by Fathand

If thicker strings are used, resulting in similar to original tension, intonation adjustment should be minimal, likewise, if it is a nylon strung guitar.

If the guitar has a floating bridge, then intonation adjustments are easy.

It should be simple to test with steel strings. Buy a set of the heaviest strings you feel comfortable playing, maybe Daddario EJ 18, .014 to .059, String it up to your desired pitch and see how it intonates or if the strings get sloppy.

So equal tension requires minimal intonation adjustment - that's useful to know. Thanks.

I was referring to the saddle that most acoustic guitars have. The material has a certain thickness on which adjustments can be made... when does that stop being enough?

[Howard Klepper]

Thicker strings are stiffer and therefore have greater inharmonicity. That means worse intonation and more bridge adjustment even though the tension may have been kept equal. Increasing the compensation can only partially correct the intonation, because the strings' harmonics ring progressively sharper as they get higher in the harmonic series, and when we move the saddle we are only compensating to get the fundamental pitch in tune. String inharmonicity is the main reason why the scale has to be longer in order for a stringed instrument that is tuned to a lower pitch to intonate well. Heavier strings will not compensate for a string length that is too short for the pitch.

There is no definite answer for how low you can tune for a given scale length on a guitar. For starters, no string has a perfectly in tune harmonic series. Even an instrument like a piano that uses different gauge and length strings for each pitch has its issues with string inharmonicity. The guitar is a compromised instrument when compared with the piano because each string has to produce such a wide range of pitches. The answer to your question depends on how much misintonation you are willing to tolerate. You are already tolerating some, no matter how perfectly your saddle is compensated.

This is without getting into the issues of temperament, which is separate from intonation, but often gets brought up in a discussion of intonation; IMO that just muddies the already turbid waters.

[karaolos]

Originally Posted by Howard Klepper

Thicker strings are stiffer and therefore have greater inharmonicity. That means worse intonation and more bridge adjustment even though the tension may have been kept equal. Increasing the compensation can only partially correct the intonation, because the strings' harmonics ring progressively sharper as they get higher in the harmonic series, and when we move the saddle we are only compensating to get the fundamental pitch in tune. String inharmonicity is the main reason why the scale has to be longer in order for a stringed instrument that is tuned to a lower pitch to intonate well. Heavier strings will not compensate for a string length that is too short for the pitch.

There is no definite answer for how low you can tune for a given scale length on a guitar. For starters, no string has a perfectly in tune harmonic series. Even an instrument like a piano that uses different gauge and length strings for each pitch has its issues with string inharmonicity. The guitar is a compromised instrument when compared with the piano because each string has to produce such a wide range of pitches. The answer to your question depends on how much misintonation you are willing to tolerate. You are already tolerating some, no matter how perfectly your saddle is compensated.

This is without getting into the issues of temperament, which is separate from intonation, but often gets brought up in a discussion of intonation; IMO that just muddies the already turbid waters.

Thank you for educating me on inharmonicity. I am aware of the harmonic series of overtones, but I didn't know that inharmonicity increases with string core diameter and shorter scale lengths. This makes more sense now with what I'm hearing from the guitar. The fundamental reads ok, but the whole note still sounds off or a unpleasant.