I have a beginners question regarding the arching of the classical soundboard as detailed in your book. The soundboard appears to be arched across the lower bout because of the arching of the lower cross strut, but there is no arching of the soundboard along the centre line from the lower end to sound hole.
I also read Roy Courtnall's book, "Making Master Guitars" where the solera is domed inward across the lower bout and along the centre line from the bottom of the lower bout up to the soundhole implying an arch across and along the soundboard.
The workboard shim you describe has a narrow section of cork all around the edge of the lower bout to accommodate and hold the arched soundboard but because the shim has cork at the bottom end of the lower bout, it implies to me that the doming is both across and down the soundboard in your method. The shim doesn't appear to be used in the soundboard arching process but is used later in the assembly process. Have I missed something important in the process? Is the soundboard arched across the lower bout only or across and along the centreline of the lower bout?
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The raised lip of the workboard shim simply raises the guitar off the flat workboard to clear the portion of the soundboard that has been arched by the lower transversal face brace. We don't want the brace to be squashed when the back is roped on. The more traditional solera is dished for the same purpose. You cannot assume or accept the "implication" that the workboard or the solera have anything to do with actually shaping the soundboard. How could it?
Having said that, I acknowledge two "schools" of thought here. One school affirms that the guitar is improved in some undetermined way by imparting a dome into the soundboard--by clamping the fan braces against the domed solera while they are being glued to the soundboard--and then curving the base of the bridge (requiring a bridge gluing-block to be arched to match). This would extend the size and extent of the dome, than doing otherwise.
The other school of thought--the one I favor--calls for simply arching the lower transverse brace and then gluing all the fan braces flat and not arching the bridge's down-face. We believe that the string's tension is going to eventually drag all those elastic elements into a final configuration of its' own. The first school, I suppose, would affirm that purposely doming the top would impart greater stiffness and resistance to the soundboard. But to the extent that the same result could not be achieved by simply increasing the cross-section of those top elements, they don't ascribe any other distinct advantage to the greater complication.
So I go with the simpler solution. And besides, great guitars can be achieved using either method. So why choose the more complicated option?
Showing posts with label soundboards. Show all posts
Showing posts with label soundboards. Show all posts
Saturday, August 16, 2008
Saturday, May 17, 2008
On Scalloped Braces
Everyone seems to make such a big deal about them, but what are your thoughts on scalloped braces?
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I don't know what justification is advanced by builders who scallop their braces: I don't. Maybe you should ask them. I suppose they would reply, "Martin used them on guitars made during the 20s and 30s, and since those guitars reputedly sounded so good, presumably it must have been the scalloped braces." Sounds like lore, doesn't it?
Few people know that actually, those early guitars were originally braced for gut strings, and when decades later people swapped steel strings onto them, their tops eventually collapsed from the extra tension. But boy, they sure sounded great before they collapsed!!
The peculiar scallop shape, it seems apparent to me, must have originated as a result of an early voicing technique where (in the days when luthiers worked in factories, and were not just machine operators) builders reached inside through the soundhole with finger planes and removed material judiciously from the braces, in stages--and progressively listen to the changes after restringing, and stopped when they felt the compliance was "right."
There's nothing magic about the scallop shape itself, just that it was the result of the process of using finger planes to remove material through the soundhole. At least that's my best guess. But as it happens, that peculiar shape decades latered engendered enough lore and mystery to subsequently drive aspiring luthiers crazy trying to decipher its significance. I have been asked that same question by many of them.
Large, stiff, disappointing guitars are today "strutted" by technicians who reach inside through soundholes with finger planes to remove material from their "struts" to improve the sound. The result usually is to "hot rod" the guitar by making it sound somewhat louder and a bit deeper-voiced...while potentially hastening it's demise. The guitar survives only if the braces were way too large to start with or if the the strutting was done with great restraint. It takes an experienced eye to sense how much is too much.
The string's signal is nothing more than minute and rapid changes in tension (dynamic stress) amidst the constant background string tension (static stress). So the problem is to construct the top in a way that adequately supports the static stress without hindering the dynamic stress. It's the guitarmaker's dilemma: that the soundboard is really a trade off between structure and tone. If the brace heights are left high, the soundboard will resist the 200 lbs of steel-string tension with no problem at all, but with a price to pay insofar as the acoustical range that results: invariably a tight sound or a limited tonal response. Reducing the brace heights increases the compliance of the top to a wider range of signals coming from the strings and a more satisfactory acoustical response, but with a price to pay in its architecture. The builder is truly expert when he derives a sense of structure sufficient to dimension the top thickness and brace heights to achieve an optimum--say, minimally adequate structure.
So, the secret is not in the peculiar contour of the braces, it's in the acquired skill of the builder that senses the minimal structural requirements of the instrument and responds correctly when removing material. Note that Martin now again offers "scalloped braces"--as a marketing ploy, I suspect, because no one in the factory is graduating braces. They are likely to be using thicker, stiffer tops to hedge their bets, and make it a point to insist that low tension strings be used.
======================
I don't know what justification is advanced by builders who scallop their braces: I don't. Maybe you should ask them. I suppose they would reply, "Martin used them on guitars made during the 20s and 30s, and since those guitars reputedly sounded so good, presumably it must have been the scalloped braces." Sounds like lore, doesn't it?
Few people know that actually, those early guitars were originally braced for gut strings, and when decades later people swapped steel strings onto them, their tops eventually collapsed from the extra tension. But boy, they sure sounded great before they collapsed!!
The peculiar scallop shape, it seems apparent to me, must have originated as a result of an early voicing technique where (in the days when luthiers worked in factories, and were not just machine operators) builders reached inside through the soundhole with finger planes and removed material judiciously from the braces, in stages--and progressively listen to the changes after restringing, and stopped when they felt the compliance was "right."
There's nothing magic about the scallop shape itself, just that it was the result of the process of using finger planes to remove material through the soundhole. At least that's my best guess. But as it happens, that peculiar shape decades latered engendered enough lore and mystery to subsequently drive aspiring luthiers crazy trying to decipher its significance. I have been asked that same question by many of them.
Large, stiff, disappointing guitars are today "strutted" by technicians who reach inside through soundholes with finger planes to remove material from their "struts" to improve the sound. The result usually is to "hot rod" the guitar by making it sound somewhat louder and a bit deeper-voiced...while potentially hastening it's demise. The guitar survives only if the braces were way too large to start with or if the the strutting was done with great restraint. It takes an experienced eye to sense how much is too much.
The string's signal is nothing more than minute and rapid changes in tension (dynamic stress) amidst the constant background string tension (static stress). So the problem is to construct the top in a way that adequately supports the static stress without hindering the dynamic stress. It's the guitarmaker's dilemma: that the soundboard is really a trade off between structure and tone. If the brace heights are left high, the soundboard will resist the 200 lbs of steel-string tension with no problem at all, but with a price to pay insofar as the acoustical range that results: invariably a tight sound or a limited tonal response. Reducing the brace heights increases the compliance of the top to a wider range of signals coming from the strings and a more satisfactory acoustical response, but with a price to pay in its architecture. The builder is truly expert when he derives a sense of structure sufficient to dimension the top thickness and brace heights to achieve an optimum--say, minimally adequate structure.
So, the secret is not in the peculiar contour of the braces, it's in the acquired skill of the builder that senses the minimal structural requirements of the instrument and responds correctly when removing material. Note that Martin now again offers "scalloped braces"--as a marketing ploy, I suspect, because no one in the factory is graduating braces. They are likely to be using thicker, stiffer tops to hedge their bets, and make it a point to insist that low tension strings be used.
Wednesday, April 30, 2008
On Solid Maple Soundboards
I recently saw a photograph of a very beautiful Taylor 6-string. Instead of a spruce top, this guitar had a book-end top made of quilted maple. I have always been under the impression that straight grain wood like spruce or cedar was not only structurally a necessity, but also that it gave a superior tone above other choices. Taylor, being the quality brand that it is, would certainly not make such a basic mistake to overlook the importance of these considerations. Does it mean that my understanding has been wrong altogether? And what type of tone can one expect of an instrument with such type of top? (Could it be that Taylor is merely breaking the mold and becoming innovative - like Ovation has done?)
I personally like a crisp and clear tone in a guitar - almost twangy. I have thought of cutting a saddle and a nut out of aluminum. My logic just tells me that it might give me the type of tone and clarity that I am looking for. What would your view be on this?
Many thanks for all the hours of pleasure you have given me through your book - and also your willingness to respond to my questions.
Cape Town
South Africa
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The guitar is above all other things a cultural artifact: its form is derived in great measure as a result of historic and cultural processes, from a legacy of dedicated woodworking craftsmen emulating the aesthetic preferences of their day--rather than a legacy of acoustical engineers and scientists pondering over the years how to increase its acoustical efficiency. But in modern times, another process has stepped in to dictate its development: corporate marketing.
In the guitar's cultural continuum, the guitar emerged with certain materials being prized over others. These decisions, again, were based not on acoustical or engineering principles, but on far more mundane considerations: what materials were available to builders, what materials bent the best, or were less reactive, or carved the easiest, or finished easiest, and so forth.
Now every element in the guitars form and structure has an impact, be it trivial or be it significant, on its perceived tone when played. Thus a guitar made with a perfectly straight-grained spruce top will indeed sound differently than a guitar made with a solid slab of jumbled-up-grain curly maple. So, I'm willing to bet, placed side by side and played, there will be a perceived difference. My contention is that a guitar with a quilted maple top falls outside the guitar's traditional continuum. Indeed, I'll be willing to bet that the actual decision of putting a quilted maple top on an acoustical guitar was based on a marketing rule called "product differentiation in the marketplace," and not, "how can we make the sound of this guitar louder, richer, more complex?"
Regardless, you might actually like, even prefer, the sound of the Taylor with its solid maple top. So, if you don't mind corporate marketing's impact on the guitar's historic form, then buy it. But if you think the guitar's historic form has special value, then pass it by. When is a rose a rose?
I haven't heard that quilted maple top guitar, but I would be surprised if the sound quality was not inferior in certain regards. During the 1940s, when Martin made solid mahogany tops on their acoustic guitars--during the period that Spruce was at a premium for the war effort--those guitars which I've played sounded sweet but weak. Yet some other folks--mostly inexpert players--valued them highly. So I would think the same dynamic is in force here: the stiffness to weight ratio of split spruce (it's "efficiency") is greater than any other wood, bar none. That translates to a smaller inertial load being placed on the string signal at the bridge, i.e., less damping. The consequence of less "efficient," wood like maple is that only the stronger, more energetic frequency components of the string signal will succeed in driving the denser, higher-damping top, and that many of the lower-energy signals coming from the vibrating strings will stop there and remain bound up in the string--never to be heard. But just dropping out a fraction of the string signal doesn't only change it's timbre, it changes its loudness. When you drop the sliders in an audio EQ unit, the sound source changes in character (maybe even creates an unusual new sound) and so consequently, the loudness is also reduced as you do so. Ergo, the effect is an unusual--perhaps distinctive--softer sound.
I personally like a crisp and clear tone in a guitar - almost twangy. I have thought of cutting a saddle and a nut out of aluminum. My logic just tells me that it might give me the type of tone and clarity that I am looking for. What would your view be on this?
Many thanks for all the hours of pleasure you have given me through your book - and also your willingness to respond to my questions.
Cape Town
South Africa
. . . . . . . . . . . . . . . . . . . . . . . . .
The guitar is above all other things a cultural artifact: its form is derived in great measure as a result of historic and cultural processes, from a legacy of dedicated woodworking craftsmen emulating the aesthetic preferences of their day--rather than a legacy of acoustical engineers and scientists pondering over the years how to increase its acoustical efficiency. But in modern times, another process has stepped in to dictate its development: corporate marketing.
In the guitar's cultural continuum, the guitar emerged with certain materials being prized over others. These decisions, again, were based not on acoustical or engineering principles, but on far more mundane considerations: what materials were available to builders, what materials bent the best, or were less reactive, or carved the easiest, or finished easiest, and so forth.
Now every element in the guitars form and structure has an impact, be it trivial or be it significant, on its perceived tone when played. Thus a guitar made with a perfectly straight-grained spruce top will indeed sound differently than a guitar made with a solid slab of jumbled-up-grain curly maple. So, I'm willing to bet, placed side by side and played, there will be a perceived difference. My contention is that a guitar with a quilted maple top falls outside the guitar's traditional continuum. Indeed, I'll be willing to bet that the actual decision of putting a quilted maple top on an acoustical guitar was based on a marketing rule called "product differentiation in the marketplace," and not, "how can we make the sound of this guitar louder, richer, more complex?"
Regardless, you might actually like, even prefer, the sound of the Taylor with its solid maple top. So, if you don't mind corporate marketing's impact on the guitar's historic form, then buy it. But if you think the guitar's historic form has special value, then pass it by. When is a rose a rose?
I haven't heard that quilted maple top guitar, but I would be surprised if the sound quality was not inferior in certain regards. During the 1940s, when Martin made solid mahogany tops on their acoustic guitars--during the period that Spruce was at a premium for the war effort--those guitars which I've played sounded sweet but weak. Yet some other folks--mostly inexpert players--valued them highly. So I would think the same dynamic is in force here: the stiffness to weight ratio of split spruce (it's "efficiency") is greater than any other wood, bar none. That translates to a smaller inertial load being placed on the string signal at the bridge, i.e., less damping. The consequence of less "efficient," wood like maple is that only the stronger, more energetic frequency components of the string signal will succeed in driving the denser, higher-damping top, and that many of the lower-energy signals coming from the vibrating strings will stop there and remain bound up in the string--never to be heard. But just dropping out a fraction of the string signal doesn't only change it's timbre, it changes its loudness. When you drop the sliders in an audio EQ unit, the sound source changes in character (maybe even creates an unusual new sound) and so consequently, the loudness is also reduced as you do so. Ergo, the effect is an unusual--perhaps distinctive--softer sound.
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