I was trying to use some front chamber volume to smooth the response, so the 250CC was based on a guess that the average cone height is 1cm. For an Sd of 141cm I was approximating the "free" (as in I can't do anything about it except a phase plug) chamber volume at 150cc. I then added another 100cc based on a 1/4" (.75 cm) spacer.

What i didn't understand was you comment "so change it to around ~80cm^2 for a 6" driver". Wouldn't I still consider the entire cone area as contributing to the front chamber volume rather than just the area projected under the throat?

Thanks again.

Charlie