Post by timmccormick on Mar 11, 2017 11:17:31 GMT
An Unconstrained Guitar Soundboard Design
© Tim McCormick 2017
tmccor2003@yahoo.com email for pictures that go with this piece if interested.
Towards the end of the nineteenth century when guitars were becoming larger and steel strings began to be fitted, it became apparent that the construction methods of existing guitars were inadequate to cope with the somewhat higher string tensions of steel as compared with gut. In the USA, Orville Gibson’s response was to build carved arch-topped instruments, some with tailpieces to anchor the strings to the bottom of the guitar in the manner of the violin family of instruments, forming a break-angle of the strings over the bridge which thus exerted considerable downward pressure on the arched top. These ideas developed into the familiar jazz guitar.
At about the same time in the USA the Larson brothers were taking the existing flat-top guitar as their basic design and strengthening the internal bracing, reinforcing it with strips of hardwood. Gibson was against bracing per se, pointing out that it restricted the vibrations of the top. The Larsons’ Prairie State brand had a steel tube running from the neck block to the end block of the guitar to resist the strings’ tendency to develop compressive forces on the body. Fender used this technique in the 1960s for some of their US-made acoustic guitars, using wood instead of steel. The Babicz design seeks to distribute the string tension over a wide area of the soundboard.
None of the above-mentioned techniques tackled head-on the fundamental problem of flat-top guitar design. On the one hand the soundboard has to possess the strength to cope with the typical ten-and-a-half-stones of pull from the strings, exerted via the bridge, this achieved by the use of an internal bracing system (principally the X-brace in steel-strung instruments), but on the other the soundboard has to be thin and flexible enough to vibrate to produce the sound. These conflicting requirements can not be resolved in conventional guitar designs. It is only by removing string pull from the soundboard entirely that a solution can be found, and the presently described guitar design does exactly that.
Taking the load off the soundboard
In a conventional design the strings are attached to the bridge such that the latter exerts considerable rotational and lateral forces on the guitar’s top, or soundboard as it will henceforth be called. If however one adds a second bridge saddle to the back of the bridge to create a mirror image of the first, and then one allows the strings to continue towards the bottom of the guitar, these forces are removed from the soundboard entirely. See Cort 2. Crucially, the section of the strings to the right of the bridge in the picture are at exactly the same height, and on exactly the same plane, as the section of the strings to the left of the bridge. Cort 4 emphasizes this, the line of the ruler following the line of the strings. If the top of the guitar in Cort 1 were to be removed, the bridge would remain in exactly the same place in mid air, held there by the tension of the strings. Bridge Model 1 demonstrates this in isolation. The bridge on the guitar therefore exerts no force whatever on the soundboard, in any direction. It is only when one plucks the strings that force is applied to the soundboard, to vibrate it.
Dumping the String Tension Elsewhere
Moving on from the bridge towards the bottom of the guitar, the strings have to be attached elsewhere and their tension accommodated by other means, now that it has been successfully removed from the soundboard. The strings are attached to a string anchor (in the picture, a commercial off-the-shelf example chosen for purely ascetic reasons. I am not a guitar maker) which is in turn attached to a wooden end plate, see Cort 3. The term ‘string anchor’ is used instead of ‘tailpiece’ because a conventional tailpiece creates a string break-angle over the bridge which exerts considerable downward force on the soundboard. Crucially, the present design manifestly does not do that, so the avoidance of the term helps to dispel preconceived ideas about what it does. Indeed, the strings could be attached directly to the end plate, and an early prototype did just that. It threw up two problems. Firstly, the length of strings between the bridge and the bottom of the guitar was long enough for them to be acoustically live, causing dissonant overtones, and they had to be damped. Secondly, the distance right from the bottom of the guitar to the furthest tuning machines meant that some strings were barely adequate in length to make it with sufficient extra to fasten them securely. A string anchor neatly removes these two problems, and its role is straightforward, continuing the line of the strings.
In Cort 1, a wooden rod can be seen through the sound-hole. This runs down from the neck block (the latter now fitted with a thin wooden plate with a rod-sized hole in it for correct positioning of the rod), along the length of the body, and on through a hole in the end block where it emerges to butt up against the approximate centre of the end plate. The rod is aligned to be parallel to the soundboard. Two bolts near the bottom of the end plate secure it to the guitar’s end block, but these are not tightened all the way home. They are adjusted during initial set-up so that the end plate is at right-angles to the soundboard, ensuring that the wooden rod rests against it also at right-angles. The end plate therefore acts as a see-saw, and the wooden rod acts as the fulcrum. When full string tension is applied and everything has settled, the bolts are adjusted to fine-tune the alignment. In Cort 3, it can be seen that the end plate does not rest against the body of the guitar. There is a gap which is plugged by a soft gasket, and the wooden rod extends a little beyond the guitar body, through the gasket, to engage with the plate. The string tension is therefore born by the rod, and not by the guitar body.
Two points need to be made. Firstly, I am not a guitar maker, and a pre-existing instrument was procured for modification. If one were building from scratch, one would move the end plate assembly an inch or so towards the bridge, so that it was neatly flush with or a little recessed beneath the guitar body. The soundboard would have a small rectangular section removed to accommodate this, a small gap between it and the end plate being left to ensure that the plate does not bear against the edge of the soundboard. The arrangement stays the same otherwise, including the hole through which the wooden rod passes so it can be taken out after removal of the end plate to gain access through the sound-hole for repairs, fitting transducers and the like.
Secondly, the bridge saddles have slightly different heights. This is because the line of the strings makes a slightly upward slope from the fingerboard to the string anchor, meaning that the underside of the bridge and the soundboard are not therefore parallel with them. The bridge design accommodates this: if during initial set-up the two saddle heights and the plate are adjusted so that Cort 4 is obtained, the bridge functions correctly. The bolt holes in the end plate are elongated so that the plate/string anchor assembly can be adjusted in height along with the bridge saddles for action setting.
Overview of the Design
A simple and straightforwardly implemented idea removes all string tension from the guitar’s soundboard, leaving it free to vibrate. Its bracing now needs to be considered. Why now brace at all? It must be said at once that the stout transverse brace running beneath the end of the fingerboard is there to counteract the latter’s tendency to exert downward force onto the soundboard, and it must not be omitted. All other bracing is negotiable, as it were, and an early prototype had no bracing at all both to demonstrate the structural integrity of the design (it has shown complete stability over more than ten years) and to access the sonic significance of bracing by its absence. The brace-less soundboard was loud, sounded rather colourless and lacking in harmonics, and it lacked sustain. The sonic function of the bracing is firstly to couple the vibrating bridge to a large area of the soundboard via the long X-braces, and then to divide the soundboard up into smaller areas with supplementary braces, these areas vibrating at higher frequencies to achieve an appropriate tonal balance, small areas vibrating at higher frequencies than larger ones. The bracing also controls the rate at which the soundboard transduces the vibrating mechanical energy of the strings into sound, achieving an optimum balance between volume and sustain which all acoustic guitar designs need to achieve.
The main X-brace couples the vibrations of the bridge to a large area of the soundboard. The tone bars, that is the (usually) two spaced diagonal braces which lie across the bottom half of the middle section of the soundboard approximately at right-angles to one of the X braces, are appropriately named. They sub-divide this fairly large area into smaller sections which can now vibrate at mid frequencies, and are very important for a full tonal quality. Removing them produces a rather hollow, ‘absent’ quality to the sound because of the lack of mid frequencies.
The areas of the soundboard beyond the bass end and beyond the treble end of the bridge between the X-braces are usually sub-divided into three roughly equal areas by finger braces, four in all, set diagonally at right angles to the X-braces. These create small areas of vibration which increase high frequency output. That completes a brief conducted tour of a pretty standard X-brace layout. Large areas of the soundboard vibrate to produce low frequencies, driven by the main X braces, and the smaller areas between the other braces vibrate to produce the higher frequencies and harmonics. Structural considerations are not relevant to the present design.
The sound-hole is something of a misnomer. Base-hole would be better. Much of the sound comes from the soundboard as a whole, and the functioning of the sound-hole is twofold. Firstly, it forms a Helmholtz resonance with the internal air volume of the guitar body to enhance the output at that resonant frequency and at frequencies very close to it. The resonant frequency is generally at G, third fret on the bottom string, for OM/000-sized guitars; and a semitone lower at F# for jumbos and dreadnoughts. It is somewhat higher for smaller bodied guitars. Secondly, a mechanism is also at work which is broader-banded in nature, helping to prevent the Helmholtz resonance from dominating the low frequency performance by broadening the low frequency output. The soundboard does not couple very efficiently directly with the outside air at low frequencies, and left to itself the sound would be anaemic. Prove this for yourself by placing a tableware coaster over the sound-hole and hearing what happens to the sound. Low frequency fundamentals disappear. But inside the guitar, the enclosed volume of air has a greater acoustic impedance than has the open air ( enclosed within a confined space, it is ‘springier’) and due to the increased acoustic loading the internal surface of the soundboard can transfer low frequency energy into it more efficiently, pumping it through the sound-hole. This is essentially similar to the coupled cavity principle in loudspeaker design. The low frequency output of the guitar is therefore smoother and broader-band than the Helmholtz resonance alone would provide. The back of the guitar also vibrates to enhance bass output. Compare the sound of the guitar with it held firmly against the body with the sound of it when held away from the body.
Assessment
For comparison, an English-made guitar of the first rank and of very similar proportions to the Cort was used as a formidable control by which to assess the heavily modified Cort NTL Custom. In addition to the modifications discussed, the Cort’s main X braces had about a third of the wood removed from their tops; four finger braces were installed in the panels each side of the bridge which replaced Cort’s very low ‘graft’-type braces here; the tone bars were removed to assess their contribution, and then new ones were fitted; and internally the top was sanded thinner everywhere I could get to, working through the sound-hole, to make the guitar more responsive. Before any modifications were made, the Cort was notably somewhat dead-sounding and unresponsive compared with the control. Just tapping the control’s bridge and top with the fingers produced a somewhat more lively sound than the Cort did. The latter is a typical industry type: a well-made mid-priced guitar constructed of high quality solid woods, over-built to ensure that it can be manufactured with ‘margin of safety’ and shipped anywhere in the world and survive without structural and climate variation issues rearing their ugly heads.
The Cort now had the ‘alive’ quality of the control when handling it, something which is common to high quality guitars generally. It was immediately apparent that the bass response benefitted significantly from a soundboard unconstrained by any stiffening force from string tension. Quantity of bass is not exaggerated. Fundamentals are impressive but not boomy, and even when playing close to the bridge there is an impression of ‘body’ and richness to the sound underpinning the high frequencies. The guitar is responsive, and one can feel the wood vibrating against one’s body. Placing a hand on various areas of the soundboard after playing a chord, one can feel plenty of vibration going on, as with the control, and it is easy to hear the dampening effect of the hand as one moves it around. The Helmholtz resonance (discussed earlier) is at a point between F# and G (it was at G on the unmodified guitar) and it is rather less prominent than the control’s, and on other guitars of conventional design. (Technically, the Cort’s resonance is low Q, the control’s resonance is high Q.) The bass response from note to note is smooth and even as one passes through the Helmholtz frequency, and it copes with drop tuning better that the control, managing to retain a good sense of the fundamental frequencies, and I believe that this is because the soundboard is free of the string tension that normally imparts a stiffening tautness. The control has weaker fundamentals, so is not as warm in the bass. The control though has better mid range power, a rich density of tone which allows it to excel at bringing out melodies played on the top three strings, particularly when one moves a few frets up the fingerboard. I think this is partly because the stiffening string load on the soundboard of the control tends to favour upper rather than lower frequency power, but it probably also has a fair amount to do with the makers’ canny placement of extra finger braces in the tone bar area. It has also been played for twelve years, and its tone has fully developed. The Cort at the time of writing had only been played for a few weeks, and its tone, including mid-range output, was improving. One also has to be wary of attributing effects to specific causes without definitive evidence.
But the fact that the Cort now holds its own with a guitar costing nearly five times the price, and even exceeds its performance in the quality of the bass, is a vindication of the design. Additionally, it has the huge advantage of being structurally extremely stable. The Cort was modified and then left for ten years because of pressure of other things, and nothing had moved at all. It was even tolerably in tune. The control after ten years had an action that had drifted high, and an intonation that had become sharp, these because of the familiar ten-and-a-half stones of string pull exerting rotational and lateral forces on the bridge and soundboard. This is typical of high quality, responsive, lightly built guitars generally. A new nut cured both problems, restoring its action and intonation to exemplary standards. The long-term structural stability of the modified Cort, ensured by this design, means that these problems do not occur, and that cannot be matched by any conventional design.
Further Considerations
The twelve-string guitar can benefit a great deal from this design. Instead of strengthening the soundboard and/or the bracing to cope with the pull of twelve strings, it can be as lightly built as the Cort described above. There are no structural issues. The acoustic bass guitar would also benefit from the principle, the removal of the stiffening force of the string pull freeing the soundboard to vibrate more freely at the low frequencies for convincing fundamentals to be produced.
A ‘test-bed’ guitar can be constructed with no bracing on it whatever (apart from the aforesaid mandatory transverse brace under the end of the fingerboard), or perhaps just the main X-brace. The designer can then experiment with different types of bracing, these attached to the outside of the soundboard, to explore and develop systems which produce good results. Bracing can be added and removed without even slackening the strings, because structural considerations are a thing of the past. When promising designs have been evolved, guitars can be constructed with the bracing on the inside of the soundboards in the conventional manner to fully assess their worth. As every maker and player knows, designs have to be lived with for a period of time before definitive conclusions can be drawn.
© Tim McCormick 2017
tmccor2003@yahoo.com email for pictures that go with this piece if interested.
Towards the end of the nineteenth century when guitars were becoming larger and steel strings began to be fitted, it became apparent that the construction methods of existing guitars were inadequate to cope with the somewhat higher string tensions of steel as compared with gut. In the USA, Orville Gibson’s response was to build carved arch-topped instruments, some with tailpieces to anchor the strings to the bottom of the guitar in the manner of the violin family of instruments, forming a break-angle of the strings over the bridge which thus exerted considerable downward pressure on the arched top. These ideas developed into the familiar jazz guitar.
At about the same time in the USA the Larson brothers were taking the existing flat-top guitar as their basic design and strengthening the internal bracing, reinforcing it with strips of hardwood. Gibson was against bracing per se, pointing out that it restricted the vibrations of the top. The Larsons’ Prairie State brand had a steel tube running from the neck block to the end block of the guitar to resist the strings’ tendency to develop compressive forces on the body. Fender used this technique in the 1960s for some of their US-made acoustic guitars, using wood instead of steel. The Babicz design seeks to distribute the string tension over a wide area of the soundboard.
None of the above-mentioned techniques tackled head-on the fundamental problem of flat-top guitar design. On the one hand the soundboard has to possess the strength to cope with the typical ten-and-a-half-stones of pull from the strings, exerted via the bridge, this achieved by the use of an internal bracing system (principally the X-brace in steel-strung instruments), but on the other the soundboard has to be thin and flexible enough to vibrate to produce the sound. These conflicting requirements can not be resolved in conventional guitar designs. It is only by removing string pull from the soundboard entirely that a solution can be found, and the presently described guitar design does exactly that.
Taking the load off the soundboard
In a conventional design the strings are attached to the bridge such that the latter exerts considerable rotational and lateral forces on the guitar’s top, or soundboard as it will henceforth be called. If however one adds a second bridge saddle to the back of the bridge to create a mirror image of the first, and then one allows the strings to continue towards the bottom of the guitar, these forces are removed from the soundboard entirely. See Cort 2. Crucially, the section of the strings to the right of the bridge in the picture are at exactly the same height, and on exactly the same plane, as the section of the strings to the left of the bridge. Cort 4 emphasizes this, the line of the ruler following the line of the strings. If the top of the guitar in Cort 1 were to be removed, the bridge would remain in exactly the same place in mid air, held there by the tension of the strings. Bridge Model 1 demonstrates this in isolation. The bridge on the guitar therefore exerts no force whatever on the soundboard, in any direction. It is only when one plucks the strings that force is applied to the soundboard, to vibrate it.
Dumping the String Tension Elsewhere
Moving on from the bridge towards the bottom of the guitar, the strings have to be attached elsewhere and their tension accommodated by other means, now that it has been successfully removed from the soundboard. The strings are attached to a string anchor (in the picture, a commercial off-the-shelf example chosen for purely ascetic reasons. I am not a guitar maker) which is in turn attached to a wooden end plate, see Cort 3. The term ‘string anchor’ is used instead of ‘tailpiece’ because a conventional tailpiece creates a string break-angle over the bridge which exerts considerable downward force on the soundboard. Crucially, the present design manifestly does not do that, so the avoidance of the term helps to dispel preconceived ideas about what it does. Indeed, the strings could be attached directly to the end plate, and an early prototype did just that. It threw up two problems. Firstly, the length of strings between the bridge and the bottom of the guitar was long enough for them to be acoustically live, causing dissonant overtones, and they had to be damped. Secondly, the distance right from the bottom of the guitar to the furthest tuning machines meant that some strings were barely adequate in length to make it with sufficient extra to fasten them securely. A string anchor neatly removes these two problems, and its role is straightforward, continuing the line of the strings.
In Cort 1, a wooden rod can be seen through the sound-hole. This runs down from the neck block (the latter now fitted with a thin wooden plate with a rod-sized hole in it for correct positioning of the rod), along the length of the body, and on through a hole in the end block where it emerges to butt up against the approximate centre of the end plate. The rod is aligned to be parallel to the soundboard. Two bolts near the bottom of the end plate secure it to the guitar’s end block, but these are not tightened all the way home. They are adjusted during initial set-up so that the end plate is at right-angles to the soundboard, ensuring that the wooden rod rests against it also at right-angles. The end plate therefore acts as a see-saw, and the wooden rod acts as the fulcrum. When full string tension is applied and everything has settled, the bolts are adjusted to fine-tune the alignment. In Cort 3, it can be seen that the end plate does not rest against the body of the guitar. There is a gap which is plugged by a soft gasket, and the wooden rod extends a little beyond the guitar body, through the gasket, to engage with the plate. The string tension is therefore born by the rod, and not by the guitar body.
Two points need to be made. Firstly, I am not a guitar maker, and a pre-existing instrument was procured for modification. If one were building from scratch, one would move the end plate assembly an inch or so towards the bridge, so that it was neatly flush with or a little recessed beneath the guitar body. The soundboard would have a small rectangular section removed to accommodate this, a small gap between it and the end plate being left to ensure that the plate does not bear against the edge of the soundboard. The arrangement stays the same otherwise, including the hole through which the wooden rod passes so it can be taken out after removal of the end plate to gain access through the sound-hole for repairs, fitting transducers and the like.
Secondly, the bridge saddles have slightly different heights. This is because the line of the strings makes a slightly upward slope from the fingerboard to the string anchor, meaning that the underside of the bridge and the soundboard are not therefore parallel with them. The bridge design accommodates this: if during initial set-up the two saddle heights and the plate are adjusted so that Cort 4 is obtained, the bridge functions correctly. The bolt holes in the end plate are elongated so that the plate/string anchor assembly can be adjusted in height along with the bridge saddles for action setting.
Overview of the Design
A simple and straightforwardly implemented idea removes all string tension from the guitar’s soundboard, leaving it free to vibrate. Its bracing now needs to be considered. Why now brace at all? It must be said at once that the stout transverse brace running beneath the end of the fingerboard is there to counteract the latter’s tendency to exert downward force onto the soundboard, and it must not be omitted. All other bracing is negotiable, as it were, and an early prototype had no bracing at all both to demonstrate the structural integrity of the design (it has shown complete stability over more than ten years) and to access the sonic significance of bracing by its absence. The brace-less soundboard was loud, sounded rather colourless and lacking in harmonics, and it lacked sustain. The sonic function of the bracing is firstly to couple the vibrating bridge to a large area of the soundboard via the long X-braces, and then to divide the soundboard up into smaller areas with supplementary braces, these areas vibrating at higher frequencies to achieve an appropriate tonal balance, small areas vibrating at higher frequencies than larger ones. The bracing also controls the rate at which the soundboard transduces the vibrating mechanical energy of the strings into sound, achieving an optimum balance between volume and sustain which all acoustic guitar designs need to achieve.
The main X-brace couples the vibrations of the bridge to a large area of the soundboard. The tone bars, that is the (usually) two spaced diagonal braces which lie across the bottom half of the middle section of the soundboard approximately at right-angles to one of the X braces, are appropriately named. They sub-divide this fairly large area into smaller sections which can now vibrate at mid frequencies, and are very important for a full tonal quality. Removing them produces a rather hollow, ‘absent’ quality to the sound because of the lack of mid frequencies.
The areas of the soundboard beyond the bass end and beyond the treble end of the bridge between the X-braces are usually sub-divided into three roughly equal areas by finger braces, four in all, set diagonally at right angles to the X-braces. These create small areas of vibration which increase high frequency output. That completes a brief conducted tour of a pretty standard X-brace layout. Large areas of the soundboard vibrate to produce low frequencies, driven by the main X braces, and the smaller areas between the other braces vibrate to produce the higher frequencies and harmonics. Structural considerations are not relevant to the present design.
The sound-hole is something of a misnomer. Base-hole would be better. Much of the sound comes from the soundboard as a whole, and the functioning of the sound-hole is twofold. Firstly, it forms a Helmholtz resonance with the internal air volume of the guitar body to enhance the output at that resonant frequency and at frequencies very close to it. The resonant frequency is generally at G, third fret on the bottom string, for OM/000-sized guitars; and a semitone lower at F# for jumbos and dreadnoughts. It is somewhat higher for smaller bodied guitars. Secondly, a mechanism is also at work which is broader-banded in nature, helping to prevent the Helmholtz resonance from dominating the low frequency performance by broadening the low frequency output. The soundboard does not couple very efficiently directly with the outside air at low frequencies, and left to itself the sound would be anaemic. Prove this for yourself by placing a tableware coaster over the sound-hole and hearing what happens to the sound. Low frequency fundamentals disappear. But inside the guitar, the enclosed volume of air has a greater acoustic impedance than has the open air ( enclosed within a confined space, it is ‘springier’) and due to the increased acoustic loading the internal surface of the soundboard can transfer low frequency energy into it more efficiently, pumping it through the sound-hole. This is essentially similar to the coupled cavity principle in loudspeaker design. The low frequency output of the guitar is therefore smoother and broader-band than the Helmholtz resonance alone would provide. The back of the guitar also vibrates to enhance bass output. Compare the sound of the guitar with it held firmly against the body with the sound of it when held away from the body.
Assessment
For comparison, an English-made guitar of the first rank and of very similar proportions to the Cort was used as a formidable control by which to assess the heavily modified Cort NTL Custom. In addition to the modifications discussed, the Cort’s main X braces had about a third of the wood removed from their tops; four finger braces were installed in the panels each side of the bridge which replaced Cort’s very low ‘graft’-type braces here; the tone bars were removed to assess their contribution, and then new ones were fitted; and internally the top was sanded thinner everywhere I could get to, working through the sound-hole, to make the guitar more responsive. Before any modifications were made, the Cort was notably somewhat dead-sounding and unresponsive compared with the control. Just tapping the control’s bridge and top with the fingers produced a somewhat more lively sound than the Cort did. The latter is a typical industry type: a well-made mid-priced guitar constructed of high quality solid woods, over-built to ensure that it can be manufactured with ‘margin of safety’ and shipped anywhere in the world and survive without structural and climate variation issues rearing their ugly heads.
The Cort now had the ‘alive’ quality of the control when handling it, something which is common to high quality guitars generally. It was immediately apparent that the bass response benefitted significantly from a soundboard unconstrained by any stiffening force from string tension. Quantity of bass is not exaggerated. Fundamentals are impressive but not boomy, and even when playing close to the bridge there is an impression of ‘body’ and richness to the sound underpinning the high frequencies. The guitar is responsive, and one can feel the wood vibrating against one’s body. Placing a hand on various areas of the soundboard after playing a chord, one can feel plenty of vibration going on, as with the control, and it is easy to hear the dampening effect of the hand as one moves it around. The Helmholtz resonance (discussed earlier) is at a point between F# and G (it was at G on the unmodified guitar) and it is rather less prominent than the control’s, and on other guitars of conventional design. (Technically, the Cort’s resonance is low Q, the control’s resonance is high Q.) The bass response from note to note is smooth and even as one passes through the Helmholtz frequency, and it copes with drop tuning better that the control, managing to retain a good sense of the fundamental frequencies, and I believe that this is because the soundboard is free of the string tension that normally imparts a stiffening tautness. The control has weaker fundamentals, so is not as warm in the bass. The control though has better mid range power, a rich density of tone which allows it to excel at bringing out melodies played on the top three strings, particularly when one moves a few frets up the fingerboard. I think this is partly because the stiffening string load on the soundboard of the control tends to favour upper rather than lower frequency power, but it probably also has a fair amount to do with the makers’ canny placement of extra finger braces in the tone bar area. It has also been played for twelve years, and its tone has fully developed. The Cort at the time of writing had only been played for a few weeks, and its tone, including mid-range output, was improving. One also has to be wary of attributing effects to specific causes without definitive evidence.
But the fact that the Cort now holds its own with a guitar costing nearly five times the price, and even exceeds its performance in the quality of the bass, is a vindication of the design. Additionally, it has the huge advantage of being structurally extremely stable. The Cort was modified and then left for ten years because of pressure of other things, and nothing had moved at all. It was even tolerably in tune. The control after ten years had an action that had drifted high, and an intonation that had become sharp, these because of the familiar ten-and-a-half stones of string pull exerting rotational and lateral forces on the bridge and soundboard. This is typical of high quality, responsive, lightly built guitars generally. A new nut cured both problems, restoring its action and intonation to exemplary standards. The long-term structural stability of the modified Cort, ensured by this design, means that these problems do not occur, and that cannot be matched by any conventional design.
Further Considerations
The twelve-string guitar can benefit a great deal from this design. Instead of strengthening the soundboard and/or the bracing to cope with the pull of twelve strings, it can be as lightly built as the Cort described above. There are no structural issues. The acoustic bass guitar would also benefit from the principle, the removal of the stiffening force of the string pull freeing the soundboard to vibrate more freely at the low frequencies for convincing fundamentals to be produced.
A ‘test-bed’ guitar can be constructed with no bracing on it whatever (apart from the aforesaid mandatory transverse brace under the end of the fingerboard), or perhaps just the main X-brace. The designer can then experiment with different types of bracing, these attached to the outside of the soundboard, to explore and develop systems which produce good results. Bracing can be added and removed without even slackening the strings, because structural considerations are a thing of the past. When promising designs have been evolved, guitars can be constructed with the bracing on the inside of the soundboards in the conventional manner to fully assess their worth. As every maker and player knows, designs have to be lived with for a period of time before definitive conclusions can be drawn.
Jo whoever he is.
