CNF Isolation

The footers we make are modelled after the engineering concept of constant natural frequency (CNF) isolation. Metal spikes, such as brass or steel, on any audio gear on its own is not the best “isolator”. By definition an isolator must be a spring. Brass and steel are linear, high frequency isolators and do not change (meaning they do not readily compress) with a change in load (added noise).

In order for metal spikes to work you need to find the centre of gravity of the object being isolated and the stiffness of the metal has to be proportional to the weight of the load otherwise vibration can transmit any frequency below the natural resonant frequency of the metal – no matter how small the point of contact. In these instances metal behaves more like a coupler. Silicone is a nonlinear isolator and it has a very low natural frequency related to its low stiffness. Although it is highly compressible its stiffness increases with the change in load and that is important because, like shocks in a car, it can adapt to changes in the environment that require the isolator to be dynamic.

 Silicone’s functional range is also proportional to its ability to be compressed this results in an effective frequency isolation range of about 5 to 100 hertz. When silicone is used in conjunction with a metal like steel or brass the silicone’s functional range increases. Stiffness is gained without losing compressibility and this increases the functional range of the isolator. The natural frequencies of the 2 isolators (silicone & metal) are combined in series (1/Fn + 1/Fn). Therefore the natural frequency of the isolator remains constant irrespective of the change of the load.

In the simplest terms, the isolator is constantly adapting to changes in the environment so that nothing interferes with the quality of the audio signal. CNF isolators are used in skyscraper & bridge construction to prevent catastrophic failure from destructive resonance. CNF isolators are commercially available for industrial equipment and cost hundreds of dollars each. I have worked with silicone for over 16 years and I formulated this silicone to be the perfect audio isolator when combined with a rigid metal support. My metal components are all custom CNC precision milled. All the metal is then hand polished. The silicone is custom formulated and poured by hand into each metal cylinder.