What Is Dp?

[coit]

I am using AJ Vented Designer and one of the parameters is Dp in centimetres.I have searched the net to no avail.Can anyone help?
Also the Thiele/Small Database brings about a virus threat warning when it loads.
thanks
Paul

 

[coit]

Sorry,answered own question:it's port diameter.
Moderator please remove.
thanks
Paul