To calculate the volume of a cone, use the formula: volume = (1/3) × π × r² × h, where r is the radius of the base and h is the height of the cone. Simply plug in the values for r and h to find the volume. You'll need to subrtact the small volume where the voice coil attaches for total accuracy, but it's negligible. Volume Displacement = Sd x Xmax Example: So (1) ultimax 18" = more than (3) RSS315HF