I have seen several C38 cabs on ebay with port tubes but I haven't seen any documentation in the library about this. The port in my C38 (sans tube is 4"), whilest one ebay auction describes 5". ?? Has anyone ever ever 'played' with these? Are these legit? Any experience with tuning a C38 cab?

http://cgi.ebay.com/JBL-BASS-TUNED-P...QQcmdZViewItem

http://http://cgi.ebay.com/JBL-TUNE-...QQcmdZViewItem