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Glass saddles and ukuleles, a test
17 August 2010
Ever since I started playing the ukulele, I've been delving deeper into the science and mystery of acoustics. For the past two and a half years I've been trying to understand how and why a ukulele - or any stringed instrument - generates sound. What factors influence the sounds we hear, and who can changing one or more element change that sound?
Luthiers know this more intimately. I'm just an outsider with a layman's passion for music and science. But during this time, I've learned a lot about instrument design and construction, about tonewoods, sound holes, the Helmholtz resonance, strings, saddles, bridges, braces, frequency response and harmonics. It's fascinating stuff. Here are some of the basics:
The top wood has a significant effect on the sound. There are many studies and several interesting reports of acoustic research online. But it's more complicated than just saying "the wood." The thickness, the grain, the density, humidity and stiffness of a particular slice all play a role as well. Since no two slices of wood are identical in physical properties - even from the same part of the tree - you can only generalize. That's why two ukes of the same wood, from the same manufacturer, set up identically with the same strings can sound very different.
In general, though, wood with a reasonably good stiffness and flexibility is preferred for a top wood since it both generates the sound well and braces the top without having to be too thick or need a lot of interior bracing. Some varieties of spruce are considered the best for sound reproduction because they are both springy and strong. They also reproduce a good range of tones.
Every wood will act as a filter for some frequencies, letting some pass through (energy turned into sound waves), and rejecting others. Spruce has a good range for sound, with an edge towards the higher frequencies which can create a 'bright' sound. Mango - a lovely wood, has a more restricted range at both ends of the scale so is very 'mellow'. Koa and mahogany are appreciated for their wide middle range, with less upper-end than spruce (hence they sound a little more 'mellow' than spruce but brighter than mango). One of my personal favourites is cedar which has many of the qualities of spruce, but a little less of its brightness.
In general, dense woods like rosewood or ebony require more energy in order to absorb it and pass it along - they work best on the bridge or saddle where the string's energy is highest (where they act as intermediary filters), but inside the instrument the energy is now much reduced (as a sound wave), and hasn't the strength to get absorbed, so it gets reflected. These woods are best used on back and sides. On the top, since these woods are not very flexible, they don't vibrate as much, so they don't create a loud sound, nor do they have the same frequency response as a more flexible wood like spruce.
So there are two types of wood used. First for the top, which is the sound producer. Second for the back and sides, which reflects the sound inside the body (and absorbs a little, too).
The body shape and size play an important role, too, because it determines how the interior sound is reflected and moved around. As does the location and size of the sound hole(s).
So you have two types of acoustic activity going on (inside and outside), and it's the combination of both that creates the sound listeners hear. They are actually separated by a tiny fraction of a second, too, but listeners hear them as one combined sound.
Then add another bit of complexity: the saddle. This is the first filter which transmits the energy of the strings to the bridge, which in turn passes it along to the top. The material of the saddle plays a very important role because it can pass or block certain frequencies (the saddle is the first filter in the process).
In general, material like bone or a very dense wood like ebony is preferred because they let a lot of the energy pass without too much restriction. Other materials like glass and brass are also good for that, as are some synthetic materials like Tusq. Some of the energy of the string is rejected by the saddle and stays in the string (this is the sustain).
And finally, the strings play an important role because they generate the mechanical energy that becomes the sound. A string's material has to be able to transmit a lot of energy without losing it too quickly (to retain the wave on the string). Change strings and the sound can be vastly different because of the way the different materials hold or transmit the wave.
So all of these factors go into the sound an instrument makes. It's as much an art as a science to mix these elements into a combination that makes a nice sounding instrument.
I started to get interested in using glass for a saddle a while back. On guitars and ukes, the saddle is like your knee bone or clavicle - it works in concert with the other components, not alone. But it is one of, if not the most, important component for sound reproduction. I had already experimented with replacing bone and wood saddles in a couple of my more mellow ukes (the mango and cigar box) with Tusq saddles, and found I could hear a noticeable difference, mostly in improved brightness.
The material of the saddle is clearly critical to the sound the instrument produces. Some materials are too dense or inflexible to reproduce frequencies well - iron and stone, for example. Others are too light - balsa wood. The preferred materials for acoustic guitars and related instruments are bone, ivory, a few synthetics and some very dense woods like ebony. There is a limited group of materials that seems well suited for sound reproduction. Although brass and glass on are among them, neither are commonly used on musical instruments. I wanted to know why and how they might work on a ukulele.
So I went and got a couple of small glass pieces from the local glass store to test. I also have some brass bits that need shaping and thinning so I can test that material, too. I finally got around to trying my glass saddle this weekend. And the results were both interesting and informative. First the background on the uke:
I picked up a well-used Lyra baritone ukulele from a woman in Toronto last month. It was purchased by her in Texas, back in 62(?) or thereabouts, and been in the family ever since. Not bad condition, given the years she and later her kids, played it. I have some pics and initial comments on my web site. It needed some cleaning and new strings, but not much else I could see. I replaced the strings with a set of Martin fluorocarbon (low D, wound D and G strings).
I wanted to change the saddle too, since the Lyra's original saddle was a credit-card thin slice of something (plastic? bone? I can't tell). I was sure it wasn't doing a very efficient job.
This weekend I widened and deepened the slot so I could test both a glass and a commercial Tusq ("artificial ivory") saddle picked up through Blue Mountain Music. Okay, not a perfect job and my hands slipped with the file once. Or twice.
Glass and Tusq have similar properties in frequency response, it seems. Both add a lot of brightness and volume to the uke's sound. Glass just adds more of the same. In fact it almost seemed too good in its reproduction, since I could hear more of my fingers scraping on the wound strings with glass than with the Tusq.
I can hear a difference between glass and Tusq, but it's not as much as, say the difference between the Tusq and the original saddle. This is the glass saddle in place (note the shim, since it is not as wide as the Tusq - that shim is actually the original saddle!).
But the difference between the original and either is incredible. This uke sounds like a steel-stringed acoustic guitar now. It's LOUD, bright, and rings like as 12-string. It's truly remarkable and so very different from any other uke I've owned. It is so different from my Pono baritone that they seem like different types of instruments, not merely different brands of the same scale. Both are mahogany but you couldn't tell - the Lyra now sounds more like spruce.
Did I mention this thing is LOUD? You can hear this thing across the street. Seriously. This little lightweight, bargain-brand uke has a powerhouse voice. Here's the Tusq in place:
Right now I have the Tusq saddle in place because both unaltered were too tall, creating an unacceptably high action mid-string. I could not really deepen the slot any more, so I started to reduce the saddle itself. Tusq is easy to work with, glass is not. I was able to reduce the height of the Tusq saddle in a few minutes. I suspect it will take a lot longer to get the glass piece down to a more acceptable height. I'll work on that over the next week and see what I can do. I still need to shave the Tusq down a hair because, while the action is now playable, it's still a trifle taller than I prefer.
That's my kitchen "workbench" for this project, with the Pono behind the Lyra. The Pono has a bone saddle and J71 strings.
What was picked up as a beater has taken on a whole new life with a new saddle. I love this sound. Reminds me of my old Yamaha acoustic guitar from the 70s. I want to wail into a Bob Dylan or Fred Neil piece every time I pick it up. A very folky sound.
While it's hardly a scientific experiment, just a subjective test, I have proven to myself that glass can be a good saddle material, although it might be almost too good and reproduce sound with a little too much fidelity. Different sorts of glass might make a difference, too, but I was limited to plate glass. I've read some comments that suggest tempered glass might be better, but the small size makes it difficult to temper.
Next on the text bench: brass. I'm also thinking about trying composite saddles, where a piece of material like glass sits under each string, but each piece is separated by another material so there is less frequency cross-over between strings (right now the energy goes both down the saddle and transversely along it).
Luthiers know this more intimately. I'm just an outsider with a layman's passion for music and science. But during this time, I've learned a lot about instrument design and construction, about tonewoods, sound holes, the Helmholtz resonance, strings, saddles, bridges, braces, frequency response and harmonics. It's fascinating stuff. Here are some of the basics:
The top wood has a significant effect on the sound. There are many studies and several interesting reports of acoustic research online. But it's more complicated than just saying "the wood." The thickness, the grain, the density, humidity and stiffness of a particular slice all play a role as well. Since no two slices of wood are identical in physical properties - even from the same part of the tree - you can only generalize. That's why two ukes of the same wood, from the same manufacturer, set up identically with the same strings can sound very different.
In general, though, wood with a reasonably good stiffness and flexibility is preferred for a top wood since it both generates the sound well and braces the top without having to be too thick or need a lot of interior bracing. Some varieties of spruce are considered the best for sound reproduction because they are both springy and strong. They also reproduce a good range of tones.
Every wood will act as a filter for some frequencies, letting some pass through (energy turned into sound waves), and rejecting others. Spruce has a good range for sound, with an edge towards the higher frequencies which can create a 'bright' sound. Mango - a lovely wood, has a more restricted range at both ends of the scale so is very 'mellow'. Koa and mahogany are appreciated for their wide middle range, with less upper-end than spruce (hence they sound a little more 'mellow' than spruce but brighter than mango). One of my personal favourites is cedar which has many of the qualities of spruce, but a little less of its brightness.
In general, dense woods like rosewood or ebony require more energy in order to absorb it and pass it along - they work best on the bridge or saddle where the string's energy is highest (where they act as intermediary filters), but inside the instrument the energy is now much reduced (as a sound wave), and hasn't the strength to get absorbed, so it gets reflected. These woods are best used on back and sides. On the top, since these woods are not very flexible, they don't vibrate as much, so they don't create a loud sound, nor do they have the same frequency response as a more flexible wood like spruce.
So there are two types of wood used. First for the top, which is the sound producer. Second for the back and sides, which reflects the sound inside the body (and absorbs a little, too).
The body shape and size play an important role, too, because it determines how the interior sound is reflected and moved around. As does the location and size of the sound hole(s).
So you have two types of acoustic activity going on (inside and outside), and it's the combination of both that creates the sound listeners hear. They are actually separated by a tiny fraction of a second, too, but listeners hear them as one combined sound.
Then add another bit of complexity: the saddle. This is the first filter which transmits the energy of the strings to the bridge, which in turn passes it along to the top. The material of the saddle plays a very important role because it can pass or block certain frequencies (the saddle is the first filter in the process).
In general, material like bone or a very dense wood like ebony is preferred because they let a lot of the energy pass without too much restriction. Other materials like glass and brass are also good for that, as are some synthetic materials like Tusq. Some of the energy of the string is rejected by the saddle and stays in the string (this is the sustain).
And finally, the strings play an important role because they generate the mechanical energy that becomes the sound. A string's material has to be able to transmit a lot of energy without losing it too quickly (to retain the wave on the string). Change strings and the sound can be vastly different because of the way the different materials hold or transmit the wave.
So all of these factors go into the sound an instrument makes. It's as much an art as a science to mix these elements into a combination that makes a nice sounding instrument.
I started to get interested in using glass for a saddle a while back. On guitars and ukes, the saddle is like your knee bone or clavicle - it works in concert with the other components, not alone. But it is one of, if not the most, important component for sound reproduction. I had already experimented with replacing bone and wood saddles in a couple of my more mellow ukes (the mango and cigar box) with Tusq saddles, and found I could hear a noticeable difference, mostly in improved brightness.
The material of the saddle is clearly critical to the sound the instrument produces. Some materials are too dense or inflexible to reproduce frequencies well - iron and stone, for example. Others are too light - balsa wood. The preferred materials for acoustic guitars and related instruments are bone, ivory, a few synthetics and some very dense woods like ebony. There is a limited group of materials that seems well suited for sound reproduction. Although brass and glass on are among them, neither are commonly used on musical instruments. I wanted to know why and how they might work on a ukulele.
So I went and got a couple of small glass pieces from the local glass store to test. I also have some brass bits that need shaping and thinning so I can test that material, too. I finally got around to trying my glass saddle this weekend. And the results were both interesting and informative. First the background on the uke:
I picked up a well-used Lyra baritone ukulele from a woman in Toronto last month. It was purchased by her in Texas, back in 62(?) or thereabouts, and been in the family ever since. Not bad condition, given the years she and later her kids, played it. I have some pics and initial comments on my web site. It needed some cleaning and new strings, but not much else I could see. I replaced the strings with a set of Martin fluorocarbon (low D, wound D and G strings).
I wanted to change the saddle too, since the Lyra's original saddle was a credit-card thin slice of something (plastic? bone? I can't tell). I was sure it wasn't doing a very efficient job.
This weekend I widened and deepened the slot so I could test both a glass and a commercial Tusq ("artificial ivory") saddle picked up through Blue Mountain Music. Okay, not a perfect job and my hands slipped with the file once. Or twice.
Glass and Tusq have similar properties in frequency response, it seems. Both add a lot of brightness and volume to the uke's sound. Glass just adds more of the same. In fact it almost seemed too good in its reproduction, since I could hear more of my fingers scraping on the wound strings with glass than with the Tusq.
I can hear a difference between glass and Tusq, but it's not as much as, say the difference between the Tusq and the original saddle. This is the glass saddle in place (note the shim, since it is not as wide as the Tusq - that shim is actually the original saddle!).
But the difference between the original and either is incredible. This uke sounds like a steel-stringed acoustic guitar now. It's LOUD, bright, and rings like as 12-string. It's truly remarkable and so very different from any other uke I've owned. It is so different from my Pono baritone that they seem like different types of instruments, not merely different brands of the same scale. Both are mahogany but you couldn't tell - the Lyra now sounds more like spruce.
Did I mention this thing is LOUD? You can hear this thing across the street. Seriously. This little lightweight, bargain-brand uke has a powerhouse voice. Here's the Tusq in place:
Right now I have the Tusq saddle in place because both unaltered were too tall, creating an unacceptably high action mid-string. I could not really deepen the slot any more, so I started to reduce the saddle itself. Tusq is easy to work with, glass is not. I was able to reduce the height of the Tusq saddle in a few minutes. I suspect it will take a lot longer to get the glass piece down to a more acceptable height. I'll work on that over the next week and see what I can do. I still need to shave the Tusq down a hair because, while the action is now playable, it's still a trifle taller than I prefer.
That's my kitchen "workbench" for this project, with the Pono behind the Lyra. The Pono has a bone saddle and J71 strings.
What was picked up as a beater has taken on a whole new life with a new saddle. I love this sound. Reminds me of my old Yamaha acoustic guitar from the 70s. I want to wail into a Bob Dylan or Fred Neil piece every time I pick it up. A very folky sound.
While it's hardly a scientific experiment, just a subjective test, I have proven to myself that glass can be a good saddle material, although it might be almost too good and reproduce sound with a little too much fidelity. Different sorts of glass might make a difference, too, but I was limited to plate glass. I've read some comments that suggest tempered glass might be better, but the small size makes it difficult to temper.
Next on the text bench: brass. I'm also thinking about trying composite saddles, where a piece of material like glass sits under each string, but each piece is separated by another material so there is less frequency cross-over between strings (right now the energy goes both down the saddle and transversely along it).
