Most phono cartridges protect their generator mechanism (some combination of coils,
magnets, and suspension) inside a body or shell which also facilitates connection to the
tonearm’s headshell or mounting point. A quick survey of the market reveals a bewildering
array of cartridge body materials; from wood to metal alloys and even stone.
The body plays an unavoidable role in the sonic signature of a cartridge through its degree of resonance, i.e. its tendency to absorb energy and release it sometime later. Wood has often been selected for cartridge bodies, as well as for the arm wand of tonearms, because its resonant behaviour typically imparts a harmonically pleasing colouration to the music.
However, if one’s goal is the very highest audio fidelity, harder materials such as metal alloys are used for cartridge bodies. One example is Timet 1100 titanium alloy, chosen for its superior energy transfer properties, used in all Acoustical Systems phono cartridges, from the new Fideles MI design right through to the statement Palladian MC model.
The Acoustical Systems cartridges take things a step further with cartridge bodies which avoid parallel surfaces and feature liquid-filled internal voids designed to minimise and damp resonant frequencies. I am sure that you will grow tired of hearing it before I grow tired of saying it, but in vinyl record playback everything matters!
In this short essay, we have only skimmed the surface of phono cartridge design but pages could be written about things such as the length of the cantilever and the design details which influence its resonant frequency, the sonic contribution of the screws used to fasten the cartridge to the headshell of your favourite tonearm, matching cartridge and tonearm to achieve a desired resonant frequency, and even the type of magnets used in cartridges (neodymium, AlNiCo, platinum iron, etc).
Perhaps some of these topics will form the basis of future Dr Analogue articles…