The Helius solution.

There are two distinct arenas in the design of a tonearm. First is the easy one, to carefully optimise a plethora of minor, but important features such as tracking error, cables and internal wires, bearing design and counterweight.

These contribute to the overall quality of performance, but really represent the icing on the cake rather than constitute the  design fundementals.

A more important consideration is the stiffness of the tonearm structure to limit and damp resonance. In other words, the unwanted vibration of component parts within the arm, and secondly to control extraneous motion of the arm.

Energy has to go somewhere, and will always take the most direct path. In the case of the tonearm, this has to sink into the turntable subchassis.

This means that all mechanical energy has to pass through the arm. Starting with a journey from the cartridge, down the arm tube and out through the bearings.

To maintain both torsional stiffness and resistance to bending in resonance, it is important to increase the surface area of the structure on the path from the headshell to the bearings.

To control the pivoted motion of the arm at lower frequencies, Helius arms are damped by differential masses.

A little considered point is that record grooves are cut at an angle of 45 degrees relative to the bearings, ergo the stylus does not function specifically vertically or horizontally as the bearings would indicate they should.

By designing a differential resonance frequency between the vertical and horizontal planes, the cartridge perceives an insurmountable inertial resistance.  The cartridge sees an effective arm mass significantly higher than it is in real life, it cannot move in sympathy.

Dynamically, it therefore behaves as a rigid platform supporting the cartridge, and does not move dynamically to colour the sound.

The last thing a tonearm is, is a tube with a cartridge at one end, and a counterweight at the other !