Construction Vibraphone

1 construction

1.1 bars
1.2 resonators
1.3 damper mechanism
1.4 motors
1.5 frame
1.6 mallets

construction

the major components of vibraphone bars, resonators, damper mechanism, motor , frame. vibraphones played mallets.

bars

interior of vibes exposed, showing deep arch , tuning marks in bar bottom, resonators, disks, damper bar , pins holding bars.

vibraphone bars made aluminum bar stock, cut blanks of pre-determined length. holes drilled through width of bars can suspended cord. maximize sustain of bars, holes placed @ approximately nodal points of bar, i.e., points of minimum amplitude around bar vibrates. uniform bar, nodal points located 22.4% each end of bar.

material ground away underside of bars in arch shape lower pitch. allows lower-pitched bars manageable length. key mellow sound of vibraphone (and marimba, uses same deep arch) compared xylophone, uses shallower arch, , glockenspiel, has no arch @ all. vibrating rectangular bars have 3 primary modes of vibration. deep arch causes these modes align , create consonant arrangement of intervals: fundamental pitch, pitch 2 octaves above that, , third pitch octave , major third above second. f3 bar forms lowest note on vibraphone, there f3 fundamental, f5 first overtone , a6 second overtone. side effect, arch causes nodal points of fundamental vibration shift closer towards ends of bar.

after beveling or rounding edges, fine-tuning adjustments made. if bar flat, overall pitch structure can raised removing material ends of bar. once sharp bar created, secondary , tertiary tones can lowered removing material specific locations of bar. vibraphones tuned standard of a=442 hz or a=440 hz depending on manufacturer or in cases customer s preference.

vibraphones graduated (foreground) , ungraduated (background) bars

like marimbas, professional vibraphones have bars of graduated width. lower bars made wider stock, , higher notes narrower stock, balance volume , tone across range of instrument. bars anodized, typically in silver or gold color, after fine tuning, , may have smooth or brushed (matte) finish. these cosmetic features negligible effect on sound.

resonators

resonators thin-walled tubes, typically made of aluminum, suitably strong material do. open @ 1 end , closed @ other. each bar paired resonator diameter wider width of bar, , length closure one-quarter of wavelength of fundamental frequency of bar. resonator a3 (the lowest on vibraphone) approximately 15 inches long. when bar , resonator in tune each other, vibrating air beneath bar travels down resonator , reflected off closure @ bottom, returns top , reflected bar, on , over, creating stronger standing wave , increasing amplitude of fundamental frequency. resonators, beside raising upper end of vibraphone s dynamic range, affect overall tone of vibraphone, since amplify fundamental, not upper partials.

note difference in front resonator sets of 2 vibraphones. difference purely cosmetic. on locke s vibraphone (on right) resonators long need be, , cap in each tube near bottom. on hutcherson s vibraphone, resonators on high end longer need to produce arched front, seen in many instruments (the cap near top of tubes). both instruments include non-functional resonator tubes no corresponding bar above avoid gap-toothed look.

there trade-off between amplifying effect of resonators , length of sustain of ringing bar. energy in ringing bar comes initial mallet strike, , energy can either used make bar ring louder initially, or not loudly longer period of time. not issue marimbas , xylophones, natural sustain time of wooden bars short, vibraphone bars can ring many seconds after being struck, , effect highly desirable in many circumstances. therefore, resonators in vibraphone tuned off-pitch create balance between loudness , sustain.

a unique feature of vibraphone resonators shaft of rotating discs, commonly called fans, across top. when fans open (vertical) resonators have full function. when fans closed (horizontal) resonators partially occluded, reducing resonance of fundamental pitch. drive belt connects shafts electric motor (see below) beneath playing surface, , rotation of fans creates many people call vibrato effect; in actuality tremolo, i.e. periodic modulation of amplitude, not pitch. in 1970 deagan introduced model, electravibe, dispensed resonator tubes entirely , took signal directly off bars, adding tremolo in preamplifier. improved portability of instrument solving problem of miking bars evenly inherent in tuned mallet instruments.

damper mechanism

for first few years of production original leedy vibraphone did not include mechanism damping, or stopping, sustaining tones. in 1928 j.c. deagan company introduced pedal mechanism has not changed substantially since. rigid bar beneath center of instrument pressed upward adjustable spring, , engages long felt pad against sharps , naturals. foot pedal lowers bar , allows notes ring freely; releasing pedal engages damper , stops vibrating notes.

motors

vibraphones have electric motor , pulley assembly mounted on 1 side or other drive disks in resonators. vibraphones used motors intended power record player turntables, , had limited or no speed adjustment capabilities. whatever speed adjustments possible made moving drive belt among small number of pulleys (usually three) of varying diameters.

later, variable speed ac motors became available @ reasonable prices. these motors allow adjustment of rotating speed via potentiometer mounted on control panel near motor. typically support rotation rates 1–12 hz. these motors remained preferred solution until 1990s, , still in use.

during 1990s, manufacturers began using computer-controlled servo stepping motors. these motors capable of slower rotating speeds approaching 0 hz. computer control allows operations not possible analog motor, such ability synchronize rotation of 2 resonator sets , stop rotation @ desired state (all open, closed, half open, etc.).

frame

the vibraphone frame offers number of challenges designers. must sturdy enough endure torsional forces created damper/spring/pedal assembly , stresses of repeated transport , playing, while still being light enough easy transport. considering weight of bars alone, doesn’t leave left frame. also, bars must securely attached frame, not rigidly. each bar must have independent flex ring.

the motor attached frame @ 1 end. hinges damper bar attached @ each end, , spring assembly , pedal attached in middle. 2 banks of resonator tubes laid grooves in frame straddle damper bar. resonators not firmly fastened frame. ends of shafts gang disks attached drive of motor via drive belt similar o-ring.

a bed bars made laying 4 wooden rails onto pins on end blocks. resonators, these rails not firmly attach frame. each rail has series of pins rubber spacers support bars. bars arranged 2 groups, , soft cord passes through nodal holes in bars of each group. bars lay between support pins, cord hooking pins. pins on outside rails have u-shaped hooks , cord rests in bend. inside pins have hook grasps cord , holds bars in place against force of damper pad. 2 ends of cord attach spring @ 1 end provide tension , flex.

mallets

typical vibraphone mallets.

vibraphone mallets consist of rubber ball core wrapped in yarn or cord , attached narrow dowel, commonly made of rattan or birch , of fiberglass or nylon. mallets suitable vibraphone suitable marimba.

the specific mallets used can have great effect on tonal characteristics of sound produced, ranging bright metallic clang mellow ring no obvious initial attack. consequently, wide array of mallets available, offering variations in hardness, head size, weight, shaft length , flexibility.

classical players must carry wide range of mallet types accommodate changing demands of composers looking particular sounds. jazz players, on other hand, make use of multi-purpose mallets allow improvisation.