Liutaio Mottola Stringed Instrument Design



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Libellula Electric Upright Bass (EUB)

Just about every upright bass player I know owns an electric upright bass (EUB). The acoustic doghouse is just too big to haul around if you don't have to, and so the EUB gets used for all those rehearsals and gigs where the acoustic bass isn't mandatory. There is an amazing amount of variation in construction of electric uprights. This instrument adds more variation to the type. With this instrument I wanted to focus on three goals. The first is ergonomic. EUBs tend to have minimal bodies and so facilitating playing position has to be dealt with in some manner. One common way to deal with this is to simply mount the instrument on a rigid tripod. This presents the instrument to the player in a nice manner but the instrument cannot be moved around even a little while playing, so this mounting method comes with some compromises. The other common method is to mount the instrument on a pin just like that of an acoustic bass, and to provide some sort of extensions from the body that emulate the points where a player's body would normally contact the instrument. The best of these work very well, providing much of the feel of an acoustic upright. In the Libellula bass I didn't want to use either of these techniques, opting instead to make the instrument wearable, that is, hung from the player's body via a strap. The second goal for this instrument was to emulate as close as possible the tone of an acoustic upright. And the third goal was to make an EUB that could be played by a bass guitar player without a major learning effort. How these goals were realized in the design of the Libellula EUB is described below.

Initially appeared: January 2, 2005
Last updated: Saturday, August 15, 2015

About the Instrument

The Libellula Electric Upright Bass

The Libellula EUB is a solid body instrument using a piezo transducer in the bridge. This combination is pretty common among electric uprights. It is worn on the body using two standard guitar straps. The two straps' mounting locations (strap buttons) position the instrument very securely relative to the player's body. You can take your hands off the instrument and it will stay in place. The attitude of the instrument is more like that of an upright bass than a bass guitar when strapped to the player. The neck is in a very upright angle as can be seen in the photos. The body of the instrument is positioned away from the player's body by a wide, curved wing. This puts the strings at a distance from the player's body and at an angle that is similar to that of an upright bass. The curve of the wing also helps to maintain the stable playing position of the instrument. The place on the back of the body at which the wing mounts can be adjusted to accommodate players of differing height. More info on fitting the instrument to the player and how the straps work can be found here.

That the instrument is both wearable and positionally stable in relation to the player's body offers some unique ergonomic advantages. The player can move around on stage easily and the instrument maintains its playing position. It can easily be played in thumb position, although the neck/body is thin enough that thumb technique really isn't necessary. At 5½ lb The instrument is quite light and easy to handle.

The Libellula is a pizzicato only instrument with a 35" scale. It is pizz only because the fingerboard radius of 7.25" is too large, and the string spacing of 0.75" at the bridge is too narrow to support arco playing. The dimensions of the D neck and the scale are similar to those of a bass guitar and so the instrument can be easily played by the bass guitarist. This is another instrument that supports one of my goals of making the sound of the upright bass available to the bass guitarist.

The instrument shown is constructed from a single billet of mahogany and has a small but traditional pegbox and scroll. Bass guitar tuning machines are used. The neck has an adjustable trussrod and as mentioned is proportioned similarly to that of the bass guitar. The fingerboard is made of Madagascar rosewood, and the fittings are all of Indian rosewood. The bridge assembly is of hard maple.

Side view

The tone of the instrument is very similar to that of an acoustic upright bass. Spectrographic analysis of acoustic, electric, and electric upright basses has indicated that the key quality that distinguishes the tone of the acoustic bass is damping of the higher harmonics. In the acoustic, these harmonics decay much more quickly than they do in electric instruments, and this more than anything else is what makes an acoustic upright sound the way it does, when played pizzicato. The Libellula EUB features a high mass, high compliance bridge with a piezo transducer. The mass and compliance of the bridge increase damping of the high harmonics. This damping is further enhanced by the use of orchestral strings rather than the more commonly used jazz pizz type strings. (It is interesting and somewhat ironic that the low-internal-damping jazz pizz style of strings were developed to try to increase sustain of the acoustic bass when played pizzicato. When such strings are used on an EUB they tend to make the instrument sound less like an acoustic upright.)

A simple impedance matching preamplifier is used in the instrument shown. A single volume knob is the only control.

The word Libellula is Italian for dragonfly. With its narrow body and small round "head" at the bottom, along with its distinctive wing assembly it looks somewhat like an upside down dragonfly.

Construction

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


 Download Libellula Electric Upright Bass Plan (zip contains .dwg and .dxf)
CAD files.

 View or Download Full Size (24"x48") Libellula Electric Upright Bass Plan (.pdf)
Use this plan if you have or have access to a large format printer.

 View or Download Tiled Libellula Electric Upright Bass 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.


Back view

Also included for this instrument are pictorial descriptions of construction.

Part 1: Constructing the body/neck assembly

Part 2: Constructing the wing

Part 3: Constructing the piezo bridge

Part 4: Final construction

Variations and Modifications

Many different variations and modifications on this general design are possible and I expect to explore at least some of these in the future. Probably the most compelling variation would be a full ¾ size instrument. At 5½ lb for the current instrument, I estimate that a ¾ size instrument could be built that still came in at a weight which would be suitable for an instrument that is hung from straps. I've already determined that the geometry of the longer instrument would not adversely affect ergonomics.

Scroll and pegbox

Extending the length of the instrument below the bridge a couple of inches would eliminate the use of the metal string anchors and the need to cut the strings. At the current weight of 5½ lb this would not add appreciably to the weight of the instrument. This minor lengthening could also make the control cavities larger, making it easier to add more control circuitry if desired.

The line of threaded inserts up the back of the instrument provide ample mounting points for alternatives to the wing and strap mounting. Various end pin and bout substitute or drum stand type mounts could be used instead.

A number of minor variations also are apparent. Changes in finish and materials, and addition of more onboard control circuitry could readily be made as requested by individual players.

Beta (Untested) Plans for Libellula Variations

Lots of feedback on this instrument and a little downtime for me gave me the opportunity to work up beta plans for two variations on this instrument. The first is a slight lengthening of the body as described above, which provides for mounting of the strings without the use of the metal string anchors. This plan also has provisions for using standard extra long scale electric bass strings as an option. The body core ramps down below the bridge to a thinner saddle, this to maintain a reasonable breakover angle for the strings. The second variation is for a full ¾ size instrument, with fingerboard and bridge dimensions suitable for arco playing. This also has the ramped down body core. These beta plans are completely untested. I had originally offered them to folks via email, asking if they built instruments from these plans if they would get back to me with some feedback on them. Requests for these plans have been frequent. Rather than continue to email them I am offering them for download here. Please remember that these are untested beta plans.


 Download Libellula Electric Upright Bass Beta Plan variation (zip contains .dwg and .dxf)
CAD files.

 View or Download Full Size (24"x48") Libellula Electric Upright Bass Beta Plan variation (.pdf)
Use this plan if you have or have access to a large format printer.

 View or Download Tiled Libellula Electric Upright Bass Beta Plan variation (.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.



 Download Libellula Electric Upright Bass Beta Plan 3/4 size variation (zip contains .dwg and .dxf)
CAD files.

 View or Download Full Size (24"x48") Libellula Electric Upright Bass Beta Plan 3/4 size variation (.pdf)
Use this plan if you have or have access to a large format printer.

 View or Download Tiled Libellula Electric Upright Bass Beta 3/4 size Plan variation (.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.