Bass Marimba


Photo by Will Gullette

 

The Harbor
Music by Cris Forster
Heidi Forster, Glassdance
Jacob Richards, Diamond Marimba
Benjamin Koscielak, Bass Marimba

 

Wild Flower
Music by Cris Forster

Cris Forster, Diamond Marimba
Benjamin Koscielak, Bass Marimba

 

Blue Nights
Music by Cris Forster

David Boyden, Bass Canon
Heidi Forster, Glassdance
Isabelle Jotterand, Just Keys
Benjamin Koscielak, Bass Marimba

Started:  1983, San Diego, California.
Finished:  1985–1986, San Francisco, California.
Dimensions: Total number of bars: 24.
Longest bar length: 44.0 in.
Shortest bar length: 19½ in.
Length of stand: 145.0 in.
Height of stand: 40.0 in.
Width of stand at wheels: 44.0 in.
Height to bars: 36.0 in.
Materials: Honduras rosewood bars. Birch, teak, mahogany,
Delrin, Kydex, Formica, cast acrylic, aluminum,
brass, and steel. HR-23 foam supports.
Range: From G1 (1/1) 49.0 cps to A3 (10/9) 217.8 cps.
Tuning: Just Intonation.

The Bass Marimba is by far the largest and most powerful instrument I have built. It is over 12 feet long, and all of the 24 exceptionally large bars are made of Honduras rosewood.

This instrument has 19 standard wavelength resonators and 5 cavity resonators. The reason for the cavity resonators is that extremely low frequencies require extremely long tubes, which in turn would require a high stand for the instrument and a high riser for the musician to stand on.

In all 24 bars on the Bass Marimba, I tuned the first three modes of vibration to produce exact harmonic ratios 1:4:8 in each bar. Therefore, above the fundamental or first mode of vibration, the second mode sounds the interval of the double-octave, frequency ratio 4/1; and the third mode sounds the interval of the triple-octave, frequency ratio 8/1. So, I tuned the lowest bar to G1, G3, and G4. I developed this tuning technique because in low-sounding bars the higher modes of vibration are clearly audible. Regarding the tuning of cavity resonators and the higher modes of vibration of bars, see Creative Aspects > Instrument Design Features.

Despite its enormous size, this instrument requires only a screwdriver to assemble. Hand knobs hold all the large structural components together.

The Chrysalis Foundation