I've loaded a speaker driver into WinSL (which I'm completely new to) , the speaker database gave me the WinSL file to use so the numbers are ok .It's the Faital Pro 10FE200 8. 10" bass driver. I've entered "Vented" with a tuning of 30HZ to see the ports and I get results I don't understand. I always assumed that if you used two ports of the same diameter rather than one , they would be around half the length so that the volume of air they contain would remain the same. But I get double the length for two ports of 6.8cm diameter each than for one of 6.8cm diameter. It also offers a Cross Area that is half as big despite the port diameter remaining the same . And some figures are greyed out , is this simply because they are not for varying?
For a given Fb (tuning frequency) the larger the total duct CSA the longer it needs to be. The CSA WinISD is providing is a total when multiples are used. The greyed out figures are those calculated from the data input, so as-is you can't adjust them independently; they will vary depending on whatever other data you input.