The Resonators
All resonators have four piezoelectric sensors located in the same positions. The first four resonators are conservative; all of them include wood soundboards supported by braces and a glued bridge, varying in their structure and materials. The last four resonators demonstrating more innovative designs: embedded springs, chamber and screws and using different connections, materials and boundary conditions.
No. 1
The first resonator is the simplest one; the soundboard was made from 3mm thick Sitka spruce, with a single support from flat mahogany in the back. The bridge was made from an ebony base and a bone top. The orientation and size of the support were defined after several modifications, in order to add stability to the resonator with a minimal surface. This is the only resonator that wasn’t arched in the milling process; the soundboard and the support, both flat, were glued in an arched mold. After the glue dried, the wood stayed arched and resisted string pressure. It was then finished and varnished to look modern and clean.
Impulse response: spectrum Impulse response: time envelope
No. 2
The second resonator was made from 4mm thick western red cedar. Unlike the first one, it was arched in the milling process. The support was oriented like the previous resonator, but instead of one glued wooden strip, here I glued two sculptured bars in order to test different support approaches. The lower part was made from ebony (to add stiffness). The bridge base was also made from ebony and the top was made out of bone. It was varnished in a heavier style, to give it a more traditional look.
No. 3
The third resonator was made from 4mm thick spruce, taken from an old, broken bridge in Vermont. This resonator was also arched in the milling process. The supports were designed in a different orientation than the previous resonators; one was made from rosewood and located underneath the bridge, while the other was sculpted from the resonator wood itself. The bridge was made entirely out of ebony. It was varnished to give an old, used, “antique” look.
Impulse response: spectrum Impulse response: time envelope
No. 5
This resonator was made from 4.5mm padouk wood. Padouk is very soft and rarely used for guitar-making. It was arched in the milling process, but unlike the previous resonators, here I use the laser cutter to create circular holes to be used as screw holders. The screws add mass and influence the vibration modes. They can also behave as a free element that vibrate and create noisy patterns that sound similar to the acoustic distortion of a clipped signal. By modifying the locations of the screws the user can tune the acoustic sound. The bridge was made from an ebony base with a bone top. It was varnished in a light style, to keep the original beauty of the wood.
Impulse response: spectrum Impulse response: time envelope
No. 6
This resonator was made from 4mm thickness purpleheart wood and western red cedar. The purpleheart is very stiff, does not need support, and was arched in a milling process. Part of the purpleheart surface was replaced with a free hanging cedar plate, connected with a cedar arm underneath the surface. The acoustic vibration patterns on the cedar plate, which contains a sensor, are expected to be different than in the case of a joint resonator. This plate can be easily manipulated by the player’s hand to get interesting sound effects. The bridge was made from an ebony base with a bone top. It was varnished in light style to keep the original beauty of the wood.
Impulse response: spectrum Impulse response: time envelope
No. 7
This resonator was made from 3mm thick mahogany. The top was milled arched, and has a single support made from mahogany and ebony. Two spring systems underneath the bridge add their physical resonance to the soundboard, causing a metallic, high frequency sound. The bridge was made from ebony alone. It was varnished in heavier style, to give it an old, used look.
Impulse response: spectrum Impulse response: time envelope
No. 8
This resonator was made from 3mm thick walnut, and a 3D printed plastic chamber. The chamber can be filled with liquids (water, oil) or other materials, such as sand or rice. Rice will create a crunchy sound when shaking the instrument and will add noisy acoustic patterns to the sound (“acoustic distortion”). The bridge was made from rosewood alone. It was varnished with wax and oil to give it a simple natural look.
Impulse response: spectrum Impulse response: time envelope
Impulse response: spectrum Impulse response: time envelope
Impulse response: spectrum Impulse response: time envelope
No. 4
This resonator was made from oak wood, 3mm thick, and it is the only one that wasn’t quartersawn. It was also arched in the milling process. Because oak is much stiffer than spruce or cedar, it was enough to use a single support from rosewood underneath the bridge. The bridge was also made from rosewood. It was varnished in light style, to keep the original beauty of the wood.
