US 3357291 A
Description (OCR text may contain errors)
ec. 12, 1967 Y w. CARMICHAEL HI FI AMPLIFICATION OF A 5ELF-CONTAINED AMPLIFIER FOR GUITAR Filed May 25, 1966 .1 IIIIV.
United States Patent 3,357,291 HI FI AMPLIFICATION OF A SELF-CONTAINED AMPLIFIER FOR GUITAR Edward W. Carmichael, Belmont, Calif. (926 Leighton Way, Sunnyvale, Calif. 94087) Filed May 25, 1966, Ser. No. 552,937 8 Claims. (Cl. 84-267) This invention relates to a speaker mount and more particularly to such a means for mounting a speaker within a conventional guitar. The present application is a continuation in part of my former application Ser. No. 490,488 filed in the United States Patent Office on Sept. 27, 1965.
In general the present invention contemplates the conversion of a conventional guitar into one in which a magnetic pickup and sound amplification system may be built into the instrument itself. Magnetic pickups in which vibrations of the strings of a guitar are imparted to an armature for the purposes of setting up small voltage disturbances therein are not broadly new. Such a pickup is shown and described in United States Letters patent No; 2,557,754 which issued June 19, 1951 to Gurnie EaMorrison. As illustrated in the Morrison patent such pickup equipped guitars do not rely on the sound box but rather on the hi fidelity circuitry for transmitting and amplifyingthe sound vibrations created by the strings. In other words, electrical guitars are constructed on a solid block body simulating the shape of a guitar and require plugs and cords connectable to a speaker unit which is remote from the instrumentitself.
It is an object of the present invention to provide, in a conventional guitar, a mounting for a speaker concealed within the sound box of the instrument and means for dampening the resonance of the speaker relative to the sound box yet affording full resonance of the sound within the sound box from a normal plucking of the strings in the usual manner.
It is another object of the invention to provide a conventional'guitar with sound amplification concealed within the sound box of the instrument and a speaker mount therein so constructed as to be independent of the normal operation of the sound created by the strings supplemental to the normal sound thereof.
These and other objects of the present invention will become apparent from a reading of the following description in the light of the drawing in which:
FIG. 1 is a plan view of the sound box of a conventional guitar having a magnetic pickup system embodied therein together with a built in speaker and mount therefor in accordance with the present invention.
FIG. 2 is a section through FIG. 1 taken along line 22 thereof.
FIG. 3 is an enlarged fragmentary section through FIG. 1 as seen along line 3-3 thereof.
FIG. 4 is a fragmentary perspective view of a portion of the sound box broken away to illustrate the speaker mount of the present invention.
Referring to the drawing a conventional guitar is shown as having a sound box 11 constructed in the usual manner. The fret arm 12 shown fragmentarily has the usual adjusting screws (not shown) at its head for tuning the strings 13 which are anchored as at 14 to a plate 15 mounted on the top panel 16 of the sound box 11. The sound box 11 has the usual circular opening 17 just beyond the inner end of the fret arm 12 and the instrument is played by plucking the strings to resonate the tone therefrom within the sound box in the usual manner.
The electrical and audio circuit 20 therefor includes the usual components such as a self contained source of electrical energy in the form of a dry cell battery 21; a magnetic pickup 22; a microelectric amplifier unit 23 Patented Dec. 12, 1967 of the transistor type, a switch 24 and a speaker 25. The components are mounted on and some are concealed within the sound box 11 so that an entire hi-fidelity amplification system is self contained on and in the guitar 1 The battery 21 and micro-electric unit 23 are each mounted securely in a replaceable manner within the sound box 11. The magnetic pick-up 22 may be mounted in any convenient place to pickup vibrations from the strings. In the present disclosure I have shown it mounted on the top panel 16 of the sound box with an independent magnet associated with each of the strings of the guitar in the usual manner. The switch 24 may be mounted on any wall of the guitar, as for example, thet top panel 16 in a zone thereof out of the way of normal playing area thereof.
The speaker 25 is preferably placed in a free area or zone of the instrument and mounted in such a manner as to be shielded from and to shield the sound box from any reflective reaction of the sound vibrations of each against the other. It is to this purpose that the speaker mount of the present invention is directed. I
The speaker mount of the present invention, generally designated 26, comprises a base board platform 27 fit solidly to the bottom or. back panel 28 of the sound box 11. The platform 27 is preferably a hard balsa wood strip or slab shaped to fit the contour of the back panel 28 of the sound box 11 and a cross rib 30 within the .box 11. The cross rib 30 may or may not be present in the conventional instrument. If none is present such'a rib 30 must be placed inthe manner shown for an abutment for the end 31 of the platform 27. The rib 30 is glued to the inner surface of the back panel 28 as is the platform 27 and the ends 31 and 31 of the latter are firmly glued to the rib 3i) and one end wall 29v of the guitar.
The base board platform 27 has a hole 27' bored therethrough to receive and support a tube32. The back panel 28 likewise has a hole 28' bored therethrough in alignment with the hole 27' in the platform 27 and the inner wall of the tube 32.
The diameter of the tube 32 is dictated by the size of the speaker 25. The platform 27 is of a width to support the tube or cylinder'32 which has an outside diameter such as to support the speaker 25. The tube 32 may be any suitable material such as paper, woodor plastic as desired. The platform 27 preferably extends parallel to the long axis of the instrument, i.e., lengthwise between the cross rib 30 and the wall 29 of the sound box.
The diameter of the speaker 25 is dictated by the area or zone available for its exposure through the top panel 16 of the sound box 11. The exposure is made throughan aperture 33 formed in the top panel 16 directly above the platform 27 and co-axially of holes 27'28' and the tube 32.
The tube or cylinder 32 is mounted within a round collar 34 of wood which fits tightly around the tube and the collar 34 is glued to the top surface 35 of the platform 27. The collar 34 is slightly higher than the thickness of the platform 27 and has its upper surface 36 spaced from the top end 37 of the tube 32. The collar 34 is coved away from its upper end 36 to a spread bottom adjacent the platform 27.
The top end 37 of the tube 32 is countersunk to conform to the cone shaped back wall 38 of the speaker 25 and is secured to the latter by suitable cement or glue to provide an infinite, absolute, sound sealed backing for the speaker. Neither the speaker nor any part of the speaker mount is in direct contact with the top panel 16 of the sound box 11. This is one of the most critical aspects of the present invention to assure against the resonant qualities of the top panel being eifected by sound vibrations from the speaker and vice versa.
To attain this purpose, the topsurface 39 of the speaker.
25 is set just beneath, but not touching the under surface of the top panel 16. It has been found that a clearance space of from .030 to .060 of an inch between the top surface 39 of the speaker and the under surface of the top panel 16 achieves best results. The top surface 39 of the speaker 25 is a solid metallic ring 40 circumscribing the fiexure cone 41 of the speaker. To assure insulation, non-touching, between the ring 40 and the top panel 16 of the sound box a suitable sound and vibration absorbing washer 41' may be inserted therebetween as shown. For purposes of the present invention a fiber sound ring 42 is set into the ring 40 and cemented thereto. This sound ring 42 is a hard paper or fiber cylinder which extends up through the aperture 33 in the top panel for a distance of approximately of an inch above the top surface of the top panel 16.
As best seen in FIGS. 2 and 3, a clearance space between the circular margin 43 'of the aperture 33 and the outer surface of the sound ring 42 must be provided. A clearance of .020 to .040 of an inch between the ring 42 and margin 43 of the aperture is considered best.
By the foregoing arrangement the speaker mount 26 provides a shield between the fiexure cone 41 of the speaker and the resonant effect of the top panel 16. Moreover, the entire speaker unit is supported from the back panel 28 of the sound box in a zone thereof remote from the resonant sound board effect of the sound box. The platform 27, tube 32 and collar 34 of the mount 26 all being firmly and securely attached to the back panel 28 assures against vibrations of the latter effecting that of the fiexure cone 41 of the speaker and vice versa.
The open bottom of the tube 32 as provided by the bore 27 in the platform and the bore 28' in the bottom panel of the guitar relieves any back pressure behind the speaker 25and thus assures clear tone from the fiexure cone 41 of the speaker without creating reverberation in the speaker body. A suitable screen 45 of fiber glass material or the like may be secured to the back panel 28 to cover the opening 28' therein and aneat trim collar 46 secured to-the back panel around the bore 28 serves to holdedges of the screen 45 in place.
While I have described the speaker amount for a conventional guitar in specific detail it will be appreciated that the same may be susceptible to variations, modifications and/ or alterations without departing from the spirit or scope of my invention. I therefore desire to avail myself of all variations, modifications and/or alterations as may fairly come within the purview of the appended claims.
What I claim as new and desire to protect by Letters Patent is:
1. The combination with a loud-speaker of an amplifier system built into the sound box of a conventional guitar having a top and a bottom panel spaced by an outer wall, a speaker mount comprising;
an aperture formed in such top panel in a zone thereof remote from the strings of the guitar and having a marginal edge slightly larger than the inner diameter of the outer rim of such speaker at the perimeter of the fiexure cone of the speaker,
a platform conforming to the contour of the inner surface of such bottom panel and secured thereto opposite the aperture formed in such top panel,
a cylinder having one end mounted on said platform and its opposite end secured to the back of the speaker for supporting the speaker concentric to and in spaced relation but close proximity to the aperture formed in such top panel, and
a sound ring secured to the outer rim of such speaker and in spaced concentric relation to the marginal edge of the aperture in such top panel.
2. The speaker mount in accordance with claim 1 in which said sound ring extends above the top surface of such top panel to shield the fiexure cone of said speaker from the vibrations of the strings of the guitar.
3. The speaker mount in accordance with claim 1 in which said platform and the bottom panel of the guitar each have a hole formed therethrough conforming substantially to and aligned with the inner wall of said cylinder.
4. The speaker mount in accordance with claim 1 including a sound and vibration absorbing collar between the outer rim of the speaker and the top panel of the guitar.
5. The speaker mount in accordance with claim 1 including a cross rib on the inner surface of the bottom panel of said guitar in spaced relation to one end of the outer wall thereof and in which said platform extends parallel to the long axis of the guitar and has its ends secured to said cross rib and to said end wall of the guitar.
6. The speaker mount in accordance with claim 3 including a sound and vibration absorbing collar disposed in the space between the outer rim of the speaker and the top panel of the guitar.
7. The speaker mount in accordance with claim 6 including a sound ring within the outer rim of the speaker and extending upwardly through the top panel and in spaced relation to the aperture in such top panel.
8. The speaker mount in accordance with claim 7 including a cross rib secured to the inner surface of the bottom panel of the guitar and in spaced relation to one end of the outer wall of the latter, and in which said platform is secured to said cross rib and to said one end wall of the guitar.
No references cited.
RICHARD B. WILKINSON, Primary Examiner.
CHARLES M. OVERBEY, Assistant Examiner.