Thanks, but what if I use 2 3" ports would you still not recommend three inch ports? 2 3" ports is bigger than 1 4" port.I would not use 3" ports at all. 4" or 6" and get the flared kind. model it in winISd and you will see what kind of port velocity you will get. anything over 100ft/sec and you WILL get port noise and port compression. neither are a good thing.