How does adsorption improve a loudspeaker?

When the loudspeaker cone moves backwards, the air in the box is compressed slightly. In a conventional loudspeaker this results in a pressure increase which acts to impede the movement of the cone. In an ACE system, the pressure increase is smaller because some of the air molecules are momentarily joined to the surface of the carbon granules (adsorbed). So the impedance to motion is significantly reduced. When the cone moves forwards the air molecules are desorbed by the resulting pressure decrease.

Technically, we can consider this as a reduction of air density. The acoustic compliance of air in the loudspeaker cabinet is given by

CA = VB / p c2
where VB is the nett enclosure volume
P is the density of air
c is the velocity of sound in air

Therefore a reduction in density produces an increase in compliance, equivalent to enlarging the enclosure. This stiffness reduction or Compliance Enhancement can be as much as four times or more under optimum conditions. Factors of 1.5 to 3 are readily achievable in practice.

next>>