when a certain freq requires a port to be say 3" x 5" long , is that 5" measurement taken from BEHIND the speaker baffle board (usually made using 3/4" MDF) ? thus actually the port should be cut 5 3/4" long ?
OR exactly 5" in lenght of port itself no matter how thick the front baffle board is & NOT bother about that ?
When manufacturers tell you to make a certain port lenght , Does that mean they already predetermine freq & they have already accounted for that 3/4" baffleboard ?
There will be a 3/4" lenght difference so definately freq will differ - SO WHICH IS THE PROPER METHOD ?
I have searched several sites but nobody is really that specific about it .....
it should always be the interior dimensions of the port so if they say this slot port is 15 x 2 and 20 inches long the port will stop at 20 inches and the port should measure 15 x 2 on the inside
The port is 5" long. It doesn't matter where you mount it as long as the port is 5" long. If it is directly attached behind the mdf, the mdf would add 3/4" to the port. The PVC would only need to be 4 1/4". I wouldn't suggest attaching it like that though.