Liutaio Mottola Stringed Instrument Design



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Tinozza Acoustic Bass Guitar

The acoustic bass guitar (ABG) is an interesting instrument. Although it has been around in one form or another for quite some time, the instrument in its present form became popular as a result of MTV and its Unplugged series of videos of generally electric bands playing with acoustic instruments. It has been popular for long enough now to be a standard instrument type. In general, ABGs are the least bass-y of acoustic bass instruments, owing to their generally (relative to, say, the double bass) small bodies and low mass plates and bridges. Similar in construction and size to the flattop acoustic guitar, the formant peaks of the ABG are similar and often identical to those of the guitar. This means the instruments have the characteristic sound of the guitar. As you probably know from reading other pages on this site, one of my overarching design goals is to replicate as much as possible the tone of the acoustic double bass in smaller instruments. Due to the ABG's relatively small size and low mass it is quite a challenge to coax upright-like tone from the instrument. Fortunately other factors play critical roles in shaping the tonal impression the instrument makes. The design of the Tinozza acoustic bass guitar exploits some of these other factors to produce an instrument with upright bass tonal qualities.

Last updated: Monday, November 04, 2013

About the Instrument

The Tinozza acoustic bass guitar is similar to most ABGs in size, construction and materials. The scale length is 34” and the neck meets the body at the 14th fret. Neck dimensions and string spacing follow the standards set by Fender electric basses. The fingerboard radius is 7.25”. The body is 18” wide at the lower bout. When it comes to bass tone bigger is always better for an ABG but bigger bodies make it increasingly more difficult for the player to get his or her arm around the body. Wood suitable for two piece plates is also not that easy to find for instruments much wider than this. At 6” the body is deeper than most ABGs. This means it encloses more mass and thus lowers the lowest resonance of the instrument somewhat closer to the ideal for bass instruments. One can't get too carried away with body depth for the same reasons of ergonomics that limit the width of the body – too deep and the player has trouble reaching around the instrument to play it.

The sides and back of the instrument shown are constructed from eastern soft maple. The top and internal braces are spruce. The mahogany neck has an adjustable trussrod and either steel or graphite composite stiffening bars. The fingerboard and fittings are made of Madagascar rosewood. The body of the instrument shown here is finished in an antique varnish and the neck is simply tung oiled. The fully removable neck is fitted to the body using two bolts, in the style of (older) Taylor guitars, and the fingerboard extension is bolted to the top using a lightweight nylon screw.

The top uses a simplified bracing pattern similar to that of the great sounding Tacoma ABGs. The Tinozza employs two longitudinal bars and two transverse bars – one heavy bar to support the end of the fingerboard and a thinner transverse bar just in front of the bridge. The sound hole is located in the upper bout. Most of the time when this sound hole position is used the claim is made that this increases the acoustic volume of the instrument by increasing the vibrating area of the top. Interestingly enough, there has never been any formal research to support this hypothesis. The sound hole is located here in the Tinozza bass primarily so the simplified bracing pattern can be used. This location also does lower the Helmholtz resonance a bit, too.

The tone of the instrument is closer to that of an acoustic upright bass than other ABGs. Spectrographic analysis of acoustic, electric, and electric upright basses has indicated that the key quality that distinguishes the tone of the acoustic double bass is damping of the higher harmonics. In the double bass, these harmonics decay much more quickly than they do in bass guitars, and this more than anything else is what makes an acoustic upright sound the way it does, when played pizzicato. The Tinozza acoustic bass guitar has a feature which make its harmonic damping profile more closely resemble that of the double bass. This instrument uses orchestral bass strings (¼ size) rather than the more commonly used electric or acoustic bass guitar strings. Orchestral strings feature a high degree of internal damping, and this contributes substantially to the uptight-like tone of the instrument. The use of orchestral strings required substantial variation from traditional ABG bridge construction and string anchoring facilities.

Since the strings are quite a bit longer than bass guitar strings they must be terminated in the body. This arrangement generally works best with the kind of floating bridge used in the violin family instruments. Unfortunately the breakover angle is too shallow for this style of bridge to be used. In the Tinozza bass the string anchor holes are placed so that each string bends horizontally at the bridge, providing a suitable 15 degree break aside angle. This couples string tension to the bridge saddle with enough force to prevent string rattling and provides good acoustic coupling to the bridge. This arrangement works particularly well with the bracing pattern used, which provides for good flexibility of the top perpendicular to the grain of the wood.

The word Tinozza is Italian for bathtub. Not the kind of thing most folks would name an instrument but I use it in homage to the American folk instrument, the washtub bass.

Construction

The downloadable copyrighted instrument plans are made available for non-commercial use only and may not be redistributed.

 Download Tinozza Acoustic Bass Guitar Plan (zip contains .dwg and .dxf)
CAD files.

 View or Download Full Size (36”x60”) Tinozza Acoustic Bass Guitar Plan (.pdf)
Use this plan if you have or have access to a large format printer.

 View or Download Tiled Tinozza Acoustic Bass Guitar Plan (.pdf)
This is a tiled version of the plan above.  It can be printed out on any printer and assembled into a full-sized plan.


Also included for this instrument are pictorial descriptions of construction. As the construction is pretty typical of any instrument of the flattop guitar class, these descriptions focus on those aspects of construction which are unique to this instrument.

Variations and Modifications

As mentioned making the instrument bigger can only improve its tone, but doing so carries ergonomic and materials availability penalties. About the only variation I have considered to date was to build a more conventional ABG version, one that uses standard bass guitar strings anchored at the bridge. The CAD files above include such a bridge, and the pdf files below show that bridge as well as frets. Note that this variation is untested. I would expect the tone of such a variation to be more guitar like, and less like that of the double bass. A useful modification to the basic design would be to add an access port to the butt end of the instrument. Large bodied guitars with sound holes in the upper bout make it impossible for all but those with very long and skinny arms to work inside the instrument once it has been assembled.

 View or Download Full Size (36”x60”) Tinozza Acoustic Bass Guitar Plan (.pdf) with frets and a bridge for use with standard bass guitar strings (untested).
Use this plan if you have or have access to a large format printer.

 View or Download Tiled Tinozza Acoustic Bass Guitar Plan (.pdf) with frets and a bridge for use with standard bass guitar strings (untested).
This is a tiled version of the plan above.  It can be printed out on any printer and assembled into a full-sized plan.

See What Others Have Built

This bass has been quite popular among bass builders, some of whom have come up with a number of interesting modifications to the basic plan. Doug Balzer did a beautiful job on a straight ahead version and put together a nice demonstration video. Check it out.