porting

Ok, just curious about something. If you have an enclosure that has a slot port in it and the person wants to change it due to tuning or port noise or what ever, or just wants to add more port to it, how would you come up with how to add in new ports? I know it would be easiest as far as adding ports to just use tubes, but just confused on how a person would come up with the proper size/length for the new ports when the box is already ported and tuned. Hope that makes sense to everyone!

If the enclosure uses a slot port it is usually easiest to build a new enclosure.  As far as calculating the effects of changing port geometry, use software like WinISD or BassBox Pro.

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If you add more port volume to the INSIDE of the box you are effectively taking away from driver's airspace.  So, if you want to modify an existing vented box...e.g. to lower the tuning freq...you could build more port structure onto the outside of the box.  But you can't very well change port opening size on a slotted box if the problem is port noise.  You would be, in effect, rebuilding the box...and it's much simpler to start anew.

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Yeah I didn't even think about the displacement of the ports. I figured that it wouldn't be anything worth messing with but had to ask to gain some more knowledge. Thanks for all the input!