Beaming will occur when the frequency wavelength is less than or equal to the diameter of the cone. Make sure your units are the same: wavelength(cm) = 34029 (cm) / frequency (hz), so: Beaming Frequency (hz) = 34029 (cm) / diameter from Sd in cm Sd being T/S value for surface area of cone. IE: Exodus ex-anarchy driver: Sd: 131cm^2, area circle = pi*radius^2, so squareroot(131/pi)=radius=6.457, radius*2=diameter, 6.457*2=12.9cm 34029 / 12.9 = 2638hz So this driver, or any other driver with the Sd in the same realm would start to beam around 2638hz. If you know the cone diameter in inches then you could also do 13397 / diameter(in). Ultimately you'd want to be using measurements for the cone, and not the overall diameter of the driver. IE: Exodus ex-anarchy driver cone diameter = ~5", and OD is ~7" 13397/5=2679hz, 13397/7=1913hz That's a significant difference. ------------------------------------------------------------------- So a rudimentary answer to 8" mid and 6.5" mid would be: 8" OD, so let's say the cone diameter is 7", 13397/7 = 1913hz 6.5" OD, ~5.5", 13397/5.5 = 2435hz