I think that a plucked instrument is never 100% intonated, it is always a compromise, precisely because of its anatomy, and the ukulele has the additional hassle of having a short scale which complicates things. To talk about this issue it is first of all important to have well understood some basic concepts about intonation and its compensation.
HOW IT WORKS
A string instrument is based on the principle that a string vibrates at a certain frequency (note) which depends on its length, tension and linear mass (which in turn depends on its diameter and density of the material). Once the instrument has been tuned (using the tuning pegs/machine, that act on the tension), the most practical way to vary the note of a certain string is to vary its length, shortening it by fretting it on the fingerboard. In doing so, the shorter the string, the higher the note produced will be. Bowed instruments such as violins have no frets, so the precision of the note produced is entrusted to the ear of the musician. In the plucked instruments, on the other hand, there are frets that must be positioned correctly, in relation to the position of the nut and bridge, in order to return precise notes.
But there is a problem: all this works well only in theory. In reality, every time the string is pressed, not only the length is changed, but also the tension. In fact, depending on its distance from the fret (action), the string is further pulled. As mentioned, the more tension we have, the higher the note will be. This means every time the string is fretted, the resulting note will always be higher than expected.
FINALLY: THE COMPENSATION
Compensation is the solution to this problem: the bridge’s saddle is positioned “a little” more distant than where it should be. In this way, every time the string is fretted, its vibrating length will be slightly longer than the theory would say. The pitch produced will undergo a decrease, which will counteract the increase given by the more tension caused by our finger.
This “a little” value depends on other variables: the action we want to keep on the instrument, the diameter and tension of the string.
Precisely for this reason, to have a good intonation, it is often not enough to move the saddle of the bridge further back, but this must be suitably shaped in order to provide different contact points for each string.
The ukulele has a short scale and this amplifies these problems.
The ukulele has plastic strings, which also amplifies these problems.
Now you start to understand because at the beginning I was talking about compromises: just change the brand of strings (sometimes even a new set of the same brand), or decide to change the action a bit, and the intonation will no longer be perfect, so you would have to re-shape a bit the saddle.
Now, why did I tell you about compensation and its problems?
In the development of my Elettrico and UFOS models, I wanted to offer the possibility of adjusting the intonation in a quick and effective way, even without particular skills or tools.
In electric guitars and basses the problem was solved by designing bridges capable of regulating the compensation and action of each individual string, but unfortunately these are not applicable to instruments that use an undersaddle piezo sensor as an amplification system (i.e. all electric ukuleles with plastic strings).
The reason is simple: sensors of that kind must be positioned under the standard single saddle to pick up the vibrations of the strings. Electric guitar style bridges are incompatible with that kind of piezos.
Ghost saddles solve this problem. Each of them has a small piezoelectric sensor inside, and this allows you to collect the signal of each string separately.
Each saddle can be adjusted at best by setting the compensation (moving them back and forth) and the action (up and down) of each individual string, simply by using an Allen key.
I had to design a new kind of bridge compatible with these saddles (originally thought for the various commercial bridges available for electric guitars), in order to be able to use them on my ukuleles. The wiring is very simple, the 4 separate signals of each module are mixed into a single signal and then sent to the output jack (in the case of UFOS) or to a potentiometer for the volume and then to the output jack (in the case of the Elettrico).
This system allows you to re-adjust the intonation with simplicity, and without the intervention of a luthier, whenever the need arises: when changing the strings, if you want to switch from High G to Low G, or if you want to change the action of the instrument.
A good side effect of this system is also the increase in homogeneity of the volumes of the various strings. In traditional piezo undersaddle systems the volume of the strings can be unbalanced due to a number of reasons: saddle movements, not perfect flatness of its base or bridge slot, sensor issues or due to the cable / effects / amplifier chain. Many of these problems are canceled by using the Ghost Saddle system.
Obviously this will not change the world of the ukuleles, we have lived very well so far even without the security of having 100% intonated instruments every single time, however I am happy to have applied this method and I’m satisfied with the result.
The Dang-o-meter is a scientific instrument capable of quantifying the amount of annoyance, screams, anger that has come up during a particular innovation. I use it to give an analog value to the degree of difficulty to the various experiments that you find in the Research and Development section.
The result in this case is:
EASY JOB! ACTUALLY I JUST HAD TO ADAPT SOMETHING ALREADY EXISTING
Thanks for reading and see you to the next experiment!