US3656395A

US3656395A - Guitar construction

Info

Publication number: US3656395A
Application number: US44202A
Authority: US
Inventors: Charles H Kaman
Original assignee: Kaman Corp
Current assignee: Kaman Corp
Priority date: 1970-06-08
Filing date: 1970-06-08
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18

Abstract

A guitar includes a body comprised of a one-piece curved bowl of fiberglass material forming the back and sides of the body and a flat wooden soundboard forming the top of the body. A unique arrangement of braces secured to the interior surface of the soundboard causes it to be tuned to a large number of different frequencies over the fully frequency and produces a full rich sound when the instrument is played.

Description

United States Patent [151 3,656,395 Kaman 1451 Apr. 18,1972

1541 GUITAR CONSTRUCTION 1,889,408 11/1932 Larson ..84/267X I 2,204,150 6/1940 Quattrociocche... 84/267 [72] Invent 3,443,465 5/1969 Kasha .,..84/267 [73] Assignee: Kaman Corporation, Bloomfield, Conn. 3,515,024 6/1970 Broussard ..84/291 221 Filed: June 8, 1970 U.S. C1 ..84/267, 84/291 Int. Cl ..G10d l/08, G10d 3/00 Field of Search ..84/267, 268, 274, 275 291, 84/294- References Cited UNITED STATES PATENTS 1,179,499 4/1916 Bohmann.... ..84/267 3,474,697 10/ 1969 Kaman ..84/267 1,764,679 6/1930 Gast ..84/267 X App]. No.: 44,202

Primary ExaminerRichard B. Wilkinson Assistant Examiner-John F. Gonzales Attorney-McCormick, Paulding and Huber [5 7] ABSTRACT A guitar includes a body comprised of a one-piece curved bowl of fiberglass material forming the back and sides of the body and a flat wooden soundboard forming the top of the body. A unique arrangement of braces secured to the interior surface of the soundboard causes it to be tuned to a large number of different frequencies over the fully frequency and produces a full rich sound when the instrument is played.

22 Claims, 28 Drawing Figures PATENTEDAPR 18 1972 INVENTOR. CHARLES H. KAMAN ATTORNEYS I PATENTEDAP 18 I372 sum NF 5 1 GUITAR CONSTRUCTION BACKGROUND OF THE'INVENTION This invention relates to guitars, and deals more particularly with a guitar construction for producing an improved character of sound from the instrument.

The guitar construction of this invention is intended primarily for use in acoustic guitars, and is shown and described herein in connection with such guitars. However, the scope of the invention is not necessarily so limited and where applicable it may, if desired, also be applied to electric guitars. In any guitar, the fundamental source of sound is a vibrating string or strings. These vibrating strings, however, by themselves emit only very low levels of sound, and to render the sound acceptably audible, it'is necessary to amplify it, or more precisely to increase the coupling between the vibrations and the surrounding air. In an acoustic guitar this amplification is achieved by transmitting the vibrations of the strings through a bridge to the top of the instrument body, referred to herein as the soundboard and forming part of a soundboard assembly including in addition to the soundboard a plurality of interior braces which modify the acoustic response of the soundboard. Of course, when a particular musical note is played by plucking a string the tone produced consists not only of the fundamental frequency of the note but also various overtones or harmonics of such note, and the degree to which the note is amplified by the soundboard assembly, as well as its tonal character or timbre, will depend on the response of the soundboard assembly to the fundamental frequency and to its various harmonic frequencies.

In previous guitar constructions, the soundboard assembly tends to emphasize certain frequencies and to de-emphasize other frequencies overv the audible range. This is due to the soundboard assembly having the characteristic of being resonant to certain frequencies, which are emphasized, and substantially non-resonant to other frequencies, which are not emphasized. The result is that if the frequency response characteristic (frequency vs. volume of emitted sound for a fixed excitation) of the soundboard assembly is plotted the 'response curve will be found to have several spaced peaks representing frequencies that are emphasized and alternating with spaced valleys representing frequencies which are not emphasized. When a guitar with such a soundboard assembly is played, particularly in loud chords, the sound tends to break-up and to become unpleasing to the ear. This is because the energy of the emitted sound is concentrated-at the few resonant frequencies of the soundboard assembly and as the chordal structure becomes more complex and the vibrationsof the strings become more intense the contrast between these resonant frequencies and the frequencies becomes more material so as to produce a more unpleasant sound.

To produce a fuller and richer tone, and to overcome the tendency of the sound to break-up when the instrument is played in loud chords, the soundboard assembly of this invention is constructed so as to be resonant or tuned to a large number of different frequencies over the audible range of frequencies, thereby producing a smoother response curve having less contrast between its peaks and valleys and tending to emphasize practically all frequencies to a considerable extent. In particular, the soundboard assembly of a guitar made in accordance with this invention includes braces on its interior surface so arranged as to cause the soundboard to have a number of different resonant areas for each particular frequency of the audible range. That is, for a particular fundamental frequency, the soundboard has distributed over its surface a number of different small areas which tend to vibrate in a substantially resonant fashion in response to such frequency. At another fundamental frequency, the soundboard includes a number of other differently located areas which tend to frequency of the fundamental tone changes, but as a general rule for any given excitation frequency the soundboard surface. includes at least some area which responds in a generally resonant manner to amplify such frequency. Accordingly, although the response curve may include some peaks at frequencies which are emphasized somewhat more than others, the response between such peak producing frequencies is more filled in and contains less deep valleys or low response frequencies than heretofore. In addition to this giving the guitar a morepleasant tone, it also tends to give it more volume, better carrying power and long sustained notes due to the fact that the soundboard assembly tends to readily resonate at any frequency with small excitation of the string or strings.

An addedbenefit of the invention is that the particular bracing employed greatly improves the sound produced by practically all soundboard materials and therefore not only permits one to obtain a highly superior sound from the better and more expensive grades of soundboard materials but to also obtain a very acceptable sound from less expensive soundboard materials such as plywood.

SUMMARY OF THE INVENTION The present invention resides in a guitar having a body with a soundboard assembly including a soundboard, a bridge attached to. the exterior surface of the soundboard below the sound opening, and bracing secured to the interior surface of the soundboard for modifying the frequency response of the soundboard and more particularly for causing it to resonate and produce a significant response at almost any excitation frequency. The bracing consists of a main top brace and a main bottom brace both arranged obliquely to the center line of the soundboard, in different directions of inclination, and extending across the bass and treble sides of the soundboard to form a generally V-shaped figure having an apex on the treble side of the soundboard. The upper or treble-side end of the bottom main brace is located at approximately the level of the bridge and the lower or treble-side end of the top main brace may be located directly adjacent thereto or may be spaced some distance upwardly therefrom. The area of the soundboard located between the two main braces comprises essentially a diaphragm in approximately the center of which the bridge is located. The bracing further includes a plurality of fan braces, of smaller cross-section than the main braces, having upper ends located adjacent the'top main brace and extending generally downwardly toward the bottom main brace,

missing or de-emphasized vibrate in a substantially resonant fashion in response to such the fan braces being spaced from one another transversely of the soundboard and being inclined relative to the soundboard center line so that each has its upper end located closer to such center line than its bottom end. Preferably, an additional brace is located above the sound opening and is inclined relative to the soundboard center line in the direction opposite to the inclination of the top main brace. Another brace may be applied in some cases to extend generally perpendicularly to and across the lower ends of some of the bass-side fan braces. The soundboard is preferably tapered in going from its top to its bottom so as to be thicker at its top than at its bottom, and on its interior surface the soundboard may be additionally thinned out in areas located below the bottom main brace and/or above the top main brace. In addition'to the soundboard assembly, the body of the guitar includes side and back walls and preferably these latter walls are part of a one-piece back having a rounded back wall curved both in the longitudinal and transverse directions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of a guitar embodying the present invention, part of the lower right-hand corner of the soundboard being broken away to show other details.

FIG. 2 is a side elevational view of the guitar of FIG. 1 with part of the bowl of the body being shown broken away to reveal other details.

FIG. 3 is a transverse sectional view taken on the line 3-3 of FIG. 1.

FIG. 4 is a plan view, drawn on a slightly enlarged scale from that of FIG. 1, showing the interior surface of the soundboard of the FIG. 1 guitar and the bracing secured thereto.

FIGS. 4A through 4H are side elevational views of the various braces of FIG. 4.

FIG. 5 is a plan view generally similar to FIG. 4 but showing bracing arranged slightly differently from that shown in FIG. 4

FIG. 6 is a front elevational view of another guitar embodying the present invention.

FIG. 7 is a plan view, drawn on a slightly enlarged scale from that of FIG. 6, showing the interior surface of the soundboard of the FIG. 6 guitar-and the bracing secured thereto.

FIGS. 7A through 71 are side elevational views of the various braces of FIG. 7.

FIG. 8 is a plan view generally similar to FIG. 7 but showing a soundboard additionally including thinned areas.

FIG. 9 is a sectional view taken on the line 9-9 of FIG. 8.

FIG. 10 is a sectional view taken on the line 10-10 of FIG. 8.

DETAILED DESCRIITION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and first particularly to FIGS. 1 to 4, these figures illustrate one embodiment of a guitar made in accordance with the present invention. The guitar is indicated generally at 10 and includes a hollow body or sound box 12 comprised of a one-piece curved bowl 14 and a soundboard assembly 16 including a fiat top plate or soundboard 18. The bowl 14 is preferably made of a resin impregnated fabric such as plies of fiberglass fabric impregnated with an epoxy resin and laminated to an appropriate thickness. The bowl has a generally inwardly curving waist characteristic of a conventional acoustic guitar. It terminates in a forward edge 20 and, as shown best in FIGS. 2 and 3, has a two-dimensionally curved rear wall which produces a correspondingly curved acoustically effective inner surface 22 which tends to reflect sound more clearly and project it farther than a more conventional flat surface. The side portion of the bowl, which terminates in the forward edge 20, includes generally U- shaped upper and lower bouts, respectively indicated at 24 and 26, connected by inwardly curved

central bouts

28, 28 which form the waist of the instrument. The side portion of the bowl adjacent the forward edge 20 is substantially perpendicular to the soundboard l8, and the soundboard is attached thereto by an L-shaped strip 30 having one leg bonded to the bowl l4 and its other leg bonded to the soundboard 18, as by adhesive. Included in the soundboard 18 is a sound opening 32 of circular shape having its center located on the longitudinal center line of the soundboard slightly above the level at which the waist of the instrument is of a minimum transverse dimensron.

Also included in the guitar 10 is a neck 34, connected to the body 12, terminating in a peghead 36 and carrying a fret board 38 having a plurality of

frets

40, 40. The illustrated peghead 36 accommodates six

strings

42, 42 which at their lower end are attached to a bridge 44 including an upright transversely extending bridge member 45. There are fourteen frets 40, on the illustrated fret board 38 between the peghead 36 and the top of the body 12, and this is a characteristic common to so-called folk guitars. Except for the soundboard assembly 16, which is hereinafter described in more detail, the guitar 10 is or may be identical to the one shown in US. Pat. No. 3,474,697 to which reference may be had for further details of its construction. I

The soundboard assembly 16 includes the soundboard 18, the bridge 44 and a unique arrangement of bracing secured to the interior surface 46 of the soundboard. It may also include, on the exterior surface 50 of the soundboard, a rosette or purfling ring 48 surrounding the sound opening 32 and possibly a band of purfling or other edge trim extending along the outer edgev of the soundboard, but these details do not form any part of the present invention.

The soundboard 18 is preferably made of a single thickness of wood, such as spruce, and also, as shown best in FIG. 2, is preferably tapered from top to bottom so as to have a greater thickness at its top than at its bottom. This provides the body 12 with maximum strength at its upper end where it is attached to the neck 34 while providing the soundboard with greater freedom of vibration in its lower region. It should be noted, however, that this tapering is not absolutely necessary to the broader aspects of the invention and if desired the soundboard may be made with a uniform thickness from top to bottom. In fact, one of the benefits of this invention is that the bracing applied to the interior surface of the soundboard enables what were previously considered to be poor soundboard materials to produce greatly improved tonal results; and by using the present invention very good sounding guitars may be made using untapered soundboards of relatively low cost material such as plywood.

The present invention involves primarily the arrangement of the bracing applied to the interior surface of the soundboard of a guitar. Before considering in detail the particular bracing applied to the guitar 10 of FIGS. 1 to 4, it should be understood that the arrangement ofthe bracing may vary slightly from one instrument to another, without departing from the invention, in order to best suit other design parameters of the guitar and/or to produce a desired tonal effect such as increase or decrease in the bass or treble response. As to the other design parameters, the more important ones involve the style of the guitar, its number and type of strings and the size of its body. conventionally, acoustic guitars are made in either a folk style or a classic style, and the strings may be either metallic or non-metallic. Also, the size of the body and consequently its volume and the size of its soundboard may vary slightly from model to model. The folk" style is characterized by a long neck having a fret board with fourteen frets between the peghead and the instrument body, and the classic style is characterized by 'a shorter neck with a fret board having 12 frets between the peghead and the instrument body. The string lengths are, however, the same for both styles with the requirement therefore that the bridge be located lower on the soundboard in the classic style than it is in the folk style. Metal strings are held at a higher tension when tuned than are nonmetallic strings and therefore the bridge in a metal stringed guitar absorbs a higher string load than does the bridge of a guitar with non-metallic strings. Also, the bridge of a l2-string guitar obviously has approximately twice the string load applied thereto as does the bridge of a six-string guitar. It is therefore seen that the location of the bridge and the string load imposed thereon, as well as the size of the soundboard and the volume of its body, may vary from one guitar to another, and in order to obtain optimum results from such different guitars it may be necessary to use in them slightly different variations of the bracing of this invention. By way of example, several different variations of the bracing falling within the scope of the invention are illustrated by the various figures presented in this application.

Turning next specifically to FIG. 4 and to FIGS. 4A to 4H, these figures show a presently preferred arrangement of bracing for the guitar 10 of FIG. 1 which is a six-string folk style guitar having a relatively large bowl. In referring to these figures, the bracing includes a number of individual braces, 4A to 4H, all of which are bonded to the interior surface 46 of the soundboard by adhesive and all of which are made of wood such as spruce. Also all of the braces, except for the brace 4E preferably have their end portions tapered by

concave scallops

56, 56. The scalloping is provided primarily to produce a thin section on each brace end to which it is applied. The manner of achieving this end thinning is not however extremely critical and if desired, particularly with the fan braces, other shaping of the braces may be used such as a gradual feathering as used on the braces 7E to 71 hereinafter discussed. The braces consist of a top main brace 46 and a bottom main brace 4F, both of which are inclinded relative to the longitudinal center-line 52 of the soundboard and extend across both the bass and treble side of the soundboard to form a generally V-shaped figure having an apex on the treble side. As shown in FIG. 4, the bass side of the soundboard is the right hand side and the treble side the left hand side, the bass side being the side underlying the lower pitched

strings

42, 42 and the treble side being the side underlying the higher pitches strings 42, 42 in the completed instrument. All four ends of the top main brace 4G and the bottom main brace 4F terminate slightly short of the outer edge 54 of the soundboard. The top main brace'4G is arranged so that its bass-side end 58 is located within the vertical region of the soundboard defined by the center and the lowermost extent of the sound opening. In FIG. 4, the line 60 indicates the level of the center of the sound opening and the line 62 indicates the level of the lowermost extent of the sound opening, the region containing the end 58 being the region between the

lines

60 and 62. The treble-side end of the top main brace 4G is located at a lower level than its bassside end and within the vertical region defined by the lowermost extent of the sound opening and a lower limit located approximately at the level of the bridge. In FIG. 4, the approximate level of the bridge is indicated by the line 66 and the region containing the end 64 is therefore the region between the lines 62 and end 64 in FIG. 4 is, in fact, a spot spaced some distance above the level 66 of the bridge.

The bottom main brace 4F is arranged so that its treble-side end 68 is located at approximately the level of the bridge and with its bass-side end 70 located a considerable distance therebelow. The location of the treble-side end 68 of the bottom main brace at approximately the level of the bridge has been found to be fairly critical and is one standard which should be maintained in making slight variations of the bracing for different guitars.

The top main brace 40 and the bottom main brace 4F are the primary braces of the invention and, except for the brace 4H, are of relatively larger cross-section and stiffness than the other braces. The arrangement of the braces 4I and 4G defines an area of the soundboard located therebetween which acts somewhat as a diaphragm and in approximately the middle of which the bridge resides. As this diaphgram-like portion of the soundboard is vibrated by the bridge, the main braces tend to transmit these vibrations to other portions of the soundboard located above and below such braces to also bring them into vibration.

In addition to the main braces 4G and 4F, the bracing of FIG. 4 also includes five fan braces 4A, 4B, 4C, 4D and 4E.,

The two

fan braces

4A and 4B are located on the treble side of the soundboard and the three

braces

4C, 4D and 4E are located on the bass side of the soundboard. All of the fan braces are spaced transversely of the soundboard from one another, and they are arranged in a fan fashion so that each is inclined relative to the longitudinal center line 52 with its upper end located closer to such center-line than its bottom end. The upper end of each fan brace is located adjacent the top main brace 4G and each extends downwardly toward the bottom main brace 4F. The three fan braces 4A, 4B and 4C have their bottom ends located adjacent the bottom main brace 70, but the lower ends of the

braces

4D and 4E are spaced laterally outwardly beyond the lower end 70 of the bottom main brace and terminate slightly short of the outer edge 54 of the soundboard. The brace 4E is scalloped at only its lower end and at its upper end engages the top main brace and is preferably bonded firmly thereto. The fan braces, 4A to 4E, have a substantial effect on the sound produced by the soundboard and in addition to aiding in transferring vibrations from the diaphragm area to other portions of the soundboard also appear to have the effect of breaking up the area of the soundboard into a larger number of potential resonating areas.

It has been found that the tone or sound of the instrument is also usually improved by placing a brace, such as the one 66. The exact location of the shown at 4H, above the sound opening and arranged to extend across a major part of both the bass and treble sides of the soundboard with its longitudinal axis inclined relative to the soundboard center line oppositely to the inclination of the top main brace 4G so that its bass side end is lower than its treble side end. The brace 4I-I is preferably relatively thick in both its cross-sectional dimensions so as to be relatively stiffer than the fan braces 4A to 4E.

With regard to the arrangement of the top main brace 46 and the bottom main brace 4F, it has been found that by varying the spacing between their treble-side ends 64 and 68 the tonal response of the instrument may be controlled to some extent. In particular, increasing the spacing between these ends tends to de-emphasize the bass frequencies, and bringing them closer together tends to emphasize the bass frequencies. The volume of the bowl generally has a similar effect on the response of the instrument. That is, a large volume bowl tends to emphasize the bass frequencies and a smaller volume bowl tends to de-emphasize the bass frequencies. In the instrument 10 of FIGS. 1 to 4, the body is one having a relatively large volume and, therefore, the treble-side ends 64 and 68 of the

main braces

40 and 4F are spread a substantial distance since the large volume of the bowl already produces a sufficient bass response and no enhancement of it is required. In a smaller volume bowl, however, the ends 64 and 68 of the main braces 4G and 4F may be placed closer together to obtain a greater bass response to compensate for the smaller volume of the bowl which normally produces less emphasis of the bass frequencies.

FIG. 5 illustrates a soundboard assembly generally similar to that shown in FIG. 4 but wherein the bracing has been arranged to achieve a greater bass response, thereby in general rendering it suitable for use on a guitar having a smaller volume body than that of the guitar 10. In FIG. 5, the various illustrated parts are substantially identical to those of FIG. 4 and therefore the same reference numerals have been used as in FIG. 4, except for being primed, and the various parts need not be redescribed in detail. It should be noted in FIG. 5, however, that the bottom main brace 4F is arranged at approximately exactly the same location as the bottom main brace 4F of FIG. 4 so that its treble side end 68' remains at the spproximate level of the bridge. The closing of the space between the ends 64' and 68 is accordingly achieved by moving the end 64 of the top main brace 46 downwardly from the position occupied by the corresponding end 64 of FIG. 4. Also, the treble-side end portions of the

main braces

46 and 4F are not scalloped in the construction direct contact with one hesive.

Referring next to FIGS. 6, 7 and 7A through 7], these figures relate to a guitar, indicated by the reference numeral 72, which in contrast to the guitar 10 of FIG. 1 is of a classic style rather than of a folk style. That is, it includes a fret board 74 having twelve frets 76, 76 between the peghead 78 and the body 80, and consequently its bridge 82 is located lower on its soundboard 84 than is the bridge 44 of FIG. 1. Except for this difference and the difference in the bracing applied to the interior surface of the soundboard 84, the guitar 72 of FIG. 6 is basically similar to the guitar 10 of FIG. 1 and, except for its bracing, need not be described in further detail.

FIG. 7 shows the bracing applied to the interior surface 86 of the soundboard 84 of the guitar 72, and FIGS. 7A through 7.! show the side elevations of the various individual braces employed. The bracing shown in FIG. 7 includes a top main brace 7B and a bottom main brace 7C. The top main brace 7B is located and arranged approximately similarly to the top main brace 40 of FIG. 4, but the bottom main brace 7C is located somewhat lower than the bottom main brace 4F of FIG. 4 so as to accommodate the lower location of the bridge and to maintain its treble-side end 88 at approximately the level of the bridge 82, such approximate level being indicated by the line 90.

of FIG. 5 and are brought into another and bonded together by an ad- Between the top main brace 78 and the bottom main brace 7C the bracing of FIG. 7 includes six fan braces, 7D to 71, located in the area between the main braces and spaced transversely from one another relative'to the soundboard. Each of the fan braces, 7D to 7I, has its upper end located adjacent the upper main brace 78 and extends downwardly from such upper main brace toward the bottom main brace 7C. Three of the fan braces, 7D, 7E and 7F, are located on the bass side of the soundboard 84 and the three other of the fan braces, 76, 7H and 7I, are located on the treble side of the soundboard. They are collectively arranged in a fan fashion so as to be inclined relative to the center line of the soundboard with each having its upper end located closer to the center-line than its bottom end. As shown, each of the fan braces has its upper end tapered by a gradual feathering, except for the one brace 7D which has an untapered upper end, and all the fan braces are shaped to gradually taper to a small thickness at their lower ends.

In addition to the two main braces and the fan braces, it has also been found to be generally beneficial to add a supplementary bottom brace, such as shown at 7J, to the bracing arrangement of FIG. 7. This supplemental bottom brace 71 is located near the lower ends of and arranged generally perpendicular to the bass-side fan braces 7D, 7E and 7F, and in the illustrated case extends between and directly contacts the sides of the bottom main brace 7C and the outermost bass-side fan brace 7D. It has still further been found that usually an improved sound may be produced with the above described bracing of FIG. 7 by also including in the soundboard assembly an upper supplemental brace, indicated at 7A and generally similar to the brace 4I-I of FIG. 4, located above the sound opening 90 of the soundboard and arranged to extend between the bass side and the treble side of the soundboard with its bass side end lower than its treble side end.

As another refinement of the present invention, it has been found that, when desired, increased treble response of the soundboard may usually be obtained by thinning out areas of the interior surface of the soundboard located either below the bottom main brace, above the top main brace or both. Referring to FIGS. 8, 9 and 10, these figures show a soundboard assembly 83 identical to the soundboard assembly 83 of FIG. 7 except for including thinned areas in the soundboard for increasing the treble response. In these figures parts which are identical or similar to corresponding parts of FIG. 7 have been given the same reference numerals as in FIG. 7, except for being primed, and need not be redescribed. As shown in FIG. 8 the soundboard 84' in its interior surface 86 includes a first depression 92 located below the bottom main brace 7C and a second depression 94 located between the top main brace 7B and the upper supplemental brace 7A. These

depressions

92 and 94 may be made by making the soundboard with initially planar interior and exterior surfaces and then cutting away material from the interior surface in the

areas

92 and 94 so that the resulting soundboard in the

areas

92 and 94 is thinner than it would be if the interior surface were truly planar.

As previously explained, the accompanying drawings and the foregoing explanation thereof relate to several specific examples of this invention, and it is intended that the bracing may be varied somewhat from these examples without departing from the broader aspects of the invention. In particular, it should be noted that the number and arrangement of braces supplementary to the two main braces, and located outside of the diaphragm-like area of the soundboard defined by the two main braces, may vary widely. As to these supplemental braces, it has been found in general that increasing their number tends to emphasize the treble response and to decrease the bass response. Also, if it is desired to modify the response of the soundboard to a particular frequency of vibration this can be done by exciting the soundboard at such frequency and locating on its surface various nodes and antinodes, nodes being points at which the soundboard has a low or zero amplitude of vibration and anti-nodes being points at which the soundboard has a high amplitude of vibration. Then, placing a supplemental brace at a node tends to increase the response of the soundboard to the frequency in question and placing a supplemental brace at an anti-node has the tendency of reducing the response of the soundboard to the frequency in question.

Iclaim:

ll. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, a bottom main brace also arranged obliquely to said vertical center-line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, and a plurality of other braces extending generally longitudinally of said soundboard and spaced from one another transversely of said soundboard, said other braces being located between said top main brace and said bottom main brace.

2. A guitar as defined in claim 1 further characterized by said soundboard being tapered from a first thickness at its top to a smaller thickness at its bottom.

3. A guitar as defined in claim 1 further characterized by said body in addition to said soundboard including means defining side and rear walls for said body, said rear wall of said body being curved in two dimensions to provide a correspondingly curved sound reflecting surface in the interior of said body spaced rearwardly from said soundboard.

4. A guitar as defined in claim 1 further characterized by said other braces each having a transverse cross-sectional size and stiffness substantially less than that of said top main brace and said bottom main brace.

5. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, and a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble-side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, the bass-side end of said top main brace being located in the vertical region of said soundboard defined by the center and said lowermost extent of said sound opening.

6. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, and a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-sideend of said bottom main brace being located at a level considerably below that of said bridge, said soundboard having a depression in its interior surface below said bottom main brace so as to render said soundboard thinner in a givenarea below said bottom main brace than it would be if said interior surface were truly planar.

7. A guitar having a body with a soundboard assembly, said .soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, and a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, said soundboard having a depression in its interior surface above said top main brace so as to render said soundboard thinner in a given area above said top main brace than it would be if said interior surface were truly planar.

8. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, and a plurality of fan braces spaced relative to one another transversely of said soundboard and located between said top main brace and said bottom main brace, each of said fan braces having an upper end located adjacent said top main brace and extending generally downwardly relative to said soundboard from said top main brace.

9. A guitar as defined in claim 8 further characterized by said soundboard assembly including at least one additional brace supplementary to said two main braces and said fan braces, said at least one supplementary brace being disposed outside of that area of said soundboard located between said two main braces.

10. A guitar as defined in claim 9 further characterized by said at least one additional brace being a supplemental brace located above said sound opening and extending across a substantial portion'of both said bass side and said treble side of said soundboard.

11. A guitar as defined in claim 10 further characterized by said supplemental brace being inclinded relative to said center line of said soundboard in such a direction that its bass side end is lower than its treble side end.

12. A guitar as defined in claim 8 further characterized by said fan braces including a first plurality thereof located on said bass side of said soundboard and a second plurality thereof located on said treble side of said soundboard, each of said fan braces of said first plurality being inclined in one direction relative to said vertical center line of said soundboard andeach of said fan braces of said second plurality being inclined in the opposite direction so that each of said fan braces has its upper end located closer to said center line than its lower end.

13. A guitar as defined in claim 12 further characterized by said fan braces being so arranged that those located closer to said center line of said soundboard are inclined at smaller angles to said center-line than those which are located further from said center-line.

14. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, and a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, said top main brace having'its treble-side end spaced above the treble-side end of said bottom main brace.

15. A guitar as defined in claim 14 further characterized by said soundboard assembly including a plurality of fan braces spaced relative to one another transversely of said soundboard and located between said top main brace and said bottom main brace, each of said fan braces having an upper end located adjacent said top main brace and extending generally downwardly relative to said soundboard from said top main brace.

16. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, said top main brace having its treble-side end in engagement with the treble-side end of said bottom main brace, and a plurality of fan braces spaced from one another transversely of said soundboard and located between said top main brace and said bottom main brace, each of said fan braces having an upper end located adjacent said top main brace and extending generally downwardly relative to said soundboard from said top main brace.

17. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across. said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, a bottom main brace also arranged obliquely to said vertical center-line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, and a plurality of fan braces spaced relative to one another transversely of said soundboard and located between said top main brace and said bottom main brace, said fan braces consisting of two fan braces located on said treble side of said soundboard and three fan braces located on said bass side of said soundboard, the two of said treble-side fan braces and the one of said bass-side fan braces which is closest to said center line of said soundboard extending substantially the entire distance from said top main brace to said bottom main brace so that their upper ends are located adjacent said top main brace and their lower ends are located adjacent said bottom main brace, the other two of said bass-side fan braces having their lower ends spaced laterally farther from said centerline than the bass-side end of said bottom main brace.

18. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the

treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, and a plurality of fan braces spaced relative to one another transversely of said soundboard and located between said top main brace and said bottom main brace, said fan braces consisting of three fan braces located on said treble side of said soundboard and three fan braces located on said bass side of said soundboard, the three of said treble-side fan braces and the one of said bass-side fan braces which is closest to said center-line of said soundboard extending substantially the entire distance from said top main brace to said bottom main brace so that their upper ends are located adjacent said top main brace and their lower ends are located-adjacent said bottom main brace, the other two of said bass-side fan braces having their lower ends spaced laterally farther from said center-line than the bass-side end of said bottom main brace.

19 A guitar as defined in claim 18 further characterized by said soundboard assembly including a supplementary bottom brace arranged generally perpendicular 0 said bass-side fan braces and .located near the lower ends of said bass-side fan braces.

20. A guitar as defined in claim 19 further characterized by said supplementary bottom brace being arranged to directly engage and extend between said bottom main brace and the laterally outermost one of said three bass-side fan braces.

21. A guitar as defined in claim 18 further characterized by said soundboard assembly including an upper supplementary brace located generally above said sound opening and extending between the bass side and the treble side of said soundboard;

22. A guitar as defined in claim 21 further characterized by said soundboard having a first depression in its interior surface below said bottom main brace and a second depression in its interior surface between said top main brace and said upper supplementary brace so as to render said soundboard thinner in a given area below said bottom main brace and in another given area between said upper main brace and said upper supplementary brace than it would be if said interior surface were truly planar.

Claims

1. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, a bottom main brace also arranged obliquely to said vertical center-line of said soundboard and extending across said soundboard from its bass side to its treble sIde, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, and a plurality of other braces extending generally longitudinally of said soundboard and spaced from one another transversely of said soundboard, said other braces being located between said top main brace and said bottom main brace.

6. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, and a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, said soundboard having a depression in its interior surface below said bottom main brace so as to render said soundboard thinner in a given area below said bottom main brace than it would be if said interior surface were truly planar.

7. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboArd with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, and a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass-side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, said soundboard having a depression in its interior surface above said top main brace so as to render said soundboard thinner in a given area above said top main brace than it would be if said interior surface were truly planar.

10. A guitar as defined in claim 9 further characterized by said at least one additional brace being a supplemental brace located above said sound opening and extending across a substantial portion of both said bass side and said treble side of said soundboard.

12. A guitar as defined in claim 8 further characterized by said fan braces including a first plurality thereof located on said bass side of said soundboard and a second plurality thereof located on said treble side of said soundboard, each of said fan braces of said first plurality being inclined in one direction relative to said vertical center line of said soundboard and each of said fan braces of said second plurality being inclined in the opposite direction so that each of said fan braces has its upper end located closer to said center line than its lower end.

14. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, and a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, said top main brace having its treble-side end spaced above the treble-side end of said bottom main brace.

17. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing securEd to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, a bottom main brace also arranged obliquely to said vertical center-line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, and a plurality of fan braces spaced relative to one another transversely of said soundboard and located between said top main brace and said bottom main brace, said fan braces consisting of two fan braces located on said treble side of said soundboard and three fan braces located on said bass side of said soundboard, the two of said treble-side fan braces and the one of said bass-side fan braces which is closest to said center line of said soundboard extending substantially the entire distance from said top main brace to said bottom main brace so that their upper ends are located adjacent said top main brace and their lower ends are located adjacent said bottom main brace, the other two of said bass-side fan braces having their lower ends spaced laterally farther from said center-line than the bass-side end of said bottom main brace.

18. A guitar having a body with a soundboard assembly, said soundboard assembly including a soundboard with generally planar interior and exterior surfaces and a sound opening passing therethrough, a bridge attached to said exterior surface of said soundboard below said sound opening, and bracing secured to said interior surface of said soundboard, said bracing including a top main brace arranged obliquely to the longitudinal center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said top main brace being located at a lower level than its bass-side end and within the vertical region defined by the lowermost extent of said sound opening and a lower limit located approximately at the level of said bridge, a bottom main brace also arranged obliquely to said vertical center line of said soundboard and extending across said soundboard from its bass side to its treble side, the treble-side end of said bottom main brace being located at approximately the level of said bridge and the bass-side end of said bottom main brace being located at a level considerably below that of said bridge, and a plurality of fan braces spaced relative to one another transversely of said soundboard and located between said top main brace and said bottom main brace, said fan braces consisting of three fan braces located on said treble side of said soundboard and three fan braces located on said bass side of said soundboard, the three of said treble-side fan braces and the one of said bass-side fan braces which is closest to said center-line of said soundboard extending substantially the entire distance from said top main brace to said bottom main brace so that their upper ends are located adjacent said top main brace and their lower ends are located adjacent said bottom main brace, the other two of said bass-side fan braces having their lower ends spaced laterally farther from said center-line than the bass-side end of said bottom main brace.

19. A guitar as defined in claim 18 further characterized by said soundboard assembly including a supplementary bottom brace arranged generally perpendicular to said bass-side fan braces and located near the lower ends of said bass-side fan braces.

21. A guitar as defined in claim 18 further characterized by said soundboard assembly including an upper supplementary brace located generally above said sound opening and extending between the bass side and the treble side of said soundboard.