box and port question

[animalbmx 10+ year member]

I have a question about box size and ports. So.. I figured out the dimensions I was going to use and it came out with 9.7 cuft(internal volume) I wanted to be tuned to 30hz. I used the online port calculator on CA.com It had me put my volume in so I put down 9.7cuft. The port length came out to be 23.5 in. My question though is after displacement of the port which comes out to be 1.7cuft I have 8 cuft of "usuable" airspace. Now would my box be considered 9.7 cuft tuned to 30hz or 8 cuft tuned to 30hz???

Strange question I know.

Click to read more...

 

[Immacomputer 10+ year member]

Net volume is what you use to calculate the port length. If the port takes up the airspace, it's no longer the net volume of the enclosure.

Take a look at this picture:

The red area is the NET area while the yellow area is the GROSS area. When trying to find the port length, you must use the net volume and not the gross volume.