Flared port question

[falcott]

I'm about to build a version of Tim Forman's bipole voigt pipes using 4" RS 40-1197 drivers, which call for ports of 1.75" dia x 2" long. Is it worth having radiused/flared ends on the ports? I have read somewhere that radiused ends necessitate a change in port dimensions. Can anyone advise as to what to do here?
Cheers!

[Spiro007]

if you widen the port then you need to make it longer.
a good starting point would be to make sure at least the non flared section of the port is at least 2" long. if the tuning is too low then you can make the port shorter bit by bit until it sounds right.

[falcott]

Thanks. If I remember right (after I wrote the above), I read that the rule of thumb is that for a 1" radius, 1" needs to be added to the length. Another way of saying the same thing, but I think your explanation is clearer.
Cheers!