Technology - Surround
The surround is the part of the driver which connects the outer diameter of the cone with the basket.
It has 2 functions :
It's part of the suspension and alignment of the cone. So the cone can move in axial direction but limits movement in non-axial direction.
It prevents acoustical short-circuiting between cone and basket (with low frequency cancellation as a result).
In some drivers it also has the function of damping reflections in the cone itself. In our driver this function is not relevant as these resonances occur well beyond the operating range of our mid/bass.
In below measurements of our driver you see these resonances pop up at around 10Khz where our driver is filtered at 5Khz.
graph 1 : with rubber surround (0,5mm thickness)
graph 2 : without rubber surround
As explained in our section "electromagnetic suspension" a surround does have disadvantages with a negative effect to the music.
non-linearity = distortion
mechanical suspension = absorbtion of energy and loss of detail
Therefore we replaced the surround with an outer ring mounted to the cone in combination with a decompression chamber.
This decompression chamber absorbs the over-pressure when the cone is moving down en returns this over-pressure when the cone is creating under-pressure whilst moving up.
This way, our surroundless design does not suffer acoustic short circuit.
Eliminating nonlinear behavior
No energy absorption by surround
Possible to use lighter cone because there is no counterforce on the edge of the cone (as it lacks a surround). This results in less flex of the cone.