In Search of the Missing Fundamental: by Richard K. Jones
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Historical Influence

With the arrival of the Industrial Age, it soon became possible for the percussive attack generally associated with timpani sound to evolve into a sound that was much more pitch and sustained oriented. Consequently, many innovations in the mechanical design of timpani, improvements in head production, and variations in stick design gradually began to appear that helped to improve not only the sound, but also the functionality of the instrument.

Significants change regarding improvements in sound occurred in central Europe during the first half of the nineteenth century. Around 1825, Berlioz’s favorite timpanist, Charies Poussard began using sponge-headed mallets to achieve a more blended sound especially for rolls. These baguettes d’éponges were soon popularized by the Leipzig timpanist Ernst Pfundt as schwammschlägel. In 1830 piano felt started to be used to cover timpani mallets. Thick blocks of piano felt could be sliced into different thickness and the timpanist could make numerous sticks of different hardness creating new sound palette.31

Simultaneously, there was also the ongoing refinement in head processing from Kalkflell to Glasfell. By 1850 a much thinner translucent head called Glasfell was produced by better mechanical and chemical processing (machine splitting and scraping devices) which produced a far better tone and many more vibrations, hence more head resonance.32

A truly seminal innovation in the physical anatomy of the instrument itself came circa 1836 when Johann Kasper Einbigler of Frankfurt-am-Main developed a system where there was no internal mechanism, the bowl was suspended from the top by an iron support ring and a new bowl shape (different from the standard of the time) was introduced. This drum was purported to be easier to tune and was said to have a superior tone quality.

Einbigler employed a threaded, vertical tuning crank pressing against a pivoted rocker-arm, which activated a spindle with vertical rods connected to the drumhead via a counterhoop. 33 For ergonomic and possibly aesthetic reasons, the plate (aka spider) that accepted the vertical rods at the bottom of the instrument was smaller than the drum itself. Consequently, the counterhoop was made larger than normal so that the vertical rods could easily be angled down to meet the plate. Whether intentional or not, the functional extended collar was born. Einbigler’s frame design became the standard for which most German timpani builders followed during the nineteenth century and is still in use today.

Original machine drums by Johann Einbigler (ca. 1840)
Cologne, Stadtmuseum Musikinstrumentensammlung

Why did Einbigler’s frame design have such an impact? Timpani with this design purportedly had a noticeable improvement in the quality of tone from previous designs. One significant improvement was the absence of an internal tensioning mechanism, which meant that there was nothing to interfere with, and consequently, influence the motion of the air inside of the bowl. This would also allow more energy to be used by the vibrating head, and not allow it to be lost as wasted mechanical energy to vibrations of the internal mechanism. The unimpeded motion of the air inside of the bowl helped to align the partials of the preferred modes into a more harmonic order resulting in a clearer and more discernible and sustaining pitch being emitted from the head.

Up until the time of Einbigler’s innovations, timpani generally had narrower collars than today’s modern instruments because the bowls had large brackets close-mounted on the sides to support the stress of the tension rods and the mechanics of the internal mechanism inside of the bowl. This included the hand-tuned drums of the period, which also needed close-mounted large brackets (often decorative) bowls to accommodate the tension of the thicker natural-skin heads. The narrower acute angle of the collar exacerbated the stiffness to shear of the membrane at the bearing edge, and  impeded the ability to center the head on the bowl creating a less defined boundary condition between the lip and the head. This limited the amount of pitch, resonance and sustain the head could produce.

Foto-3Copies of original Timpani the
Academy of Ancient Music Berlin from 1747

Courtesy of relinkbremen

One must also take into account the various types of stands in which the drums were held. All of the above factors impeded natural vibrations by the head because of energy loss to the bowl, tension lugs and stands. A bowl suspended from the top with a wider collar would allow the head to vibrate more freely thus adding a new element of audible resonance to the sound because of better centering of the head. The perception being that the tone was “rounder and fuller than previous models”34 and “…because of which the vibration is more significant and penetrating [and] voicing of the tone therefore becomes absolutely first rate.”35

Improvements in Einbigler’s design contributed to many aspects of how the bowl and frame affect the mechanics and geometries of the vibrating membrane. The external center pull spindle mechanism provided a uniform and stable method for tuning the drum, which helped keep the harmonicity of the pitch consistent through out the range of the drum. Because the bowl was being supported from an external iron support ring, improved machining processes meant the bearing edge of the suspended bowl could be kept more level and in-round creating a better boundary conditions or point of contact between the circular vibrating membrane and the bowl. The bearing edge could also be rolled to the outside of the bowl potentially increasing membrane vibrations.

Another advantage was that the amount of collar was increased slightly to accommodate the external frame and to help the tensioning rods to completely bypass the bowl. Since the tensioning rods did not need to be attached to the bowl, the flesh-hoop had more freedom to move with respect to keeping the head centered on the bowl, which helped focus the pitch and add resonance. A fleshhoop larger than the bowl also meant that the audible effects of a poorly tucked head would be more noticeable, and consequently rectified.

Since the bowl no longer need to support heavy external hardware, the copper could now be hammered to a more homogeneous thickness, which helped with thermal equilibrium between the internal and external air masses. Einbigler’s original design also used a smaller hemispheric shaped bowl, which would have affected the volume of air inside of the bowl impacting the alignment of the preferred modes adding more resonance and sustain to the head. It is interesting to note that the volume of air in this type of bowl configuration would have produced ample sound for a Schumann/Schubert sized orchestra, but not necessarily for the size of the larger Romantic orchestras, hence the later Pfundt/Hoffmann/Hentschel modifications.

Center pull spindle tuning mechanism, homogeneous suspended bowl, better heads, better collar, better bowl tolerances, better lip design, better methods for striking the membrane, better sticks; these factors yielded more vibrations from the head giving the perception that the drum was more resonant. Perhaps the greatest misconception in the newly found resonance was because Einbigler’s suspension system was believed to allow the bowl itself to “resonate more freely.” The energy from the membrane could be transmitted to the copper bowl causing it to vibrate audibly adding a new collateral color to the sound of the instrument. This is undoubtedly true to some extent, but not the primary reason for the new found volume and resonance.  At any rate, the suspended kettle mystique had been born and continues to this day, but what actually creates the resonance in timpani sound, bowl resonance, or sound radiation?

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