Quote Originally Posted by SOOTSHE View Post
Found these calculators on line & they seem to be accurate.

I worked backwards from what I want to achieve....so, I determined that the 620 cabinet box tuning is 40Hz by entering the slot dimensions & changing the tuning frequency until I got a slot length of 3/4".

Then I changed the slot dimensions until I got a slot length of 1&1/2".

From my calculations, with a front baffle 1&1/2" thick, I should need a slot of 11" x 3" to maintain the original 40Hz tuning.

The second attachment shows the results when using a round port.
For this you need 2 x 7.9cm ports 1.4" long......or 1 x 6.5" port 1.4" long.

I prefer to use the rectangular port option to maintain the original look of the cabinets.
1
Cheers.

Yes, for a vent depth doubling, it requires the vent opening area to be increased by 25% approx in order to keep the tuning same.
The shape and location changes it a little on both the sides, meaning +/-.

Yes, a rectangular port is quite reminiscing compared to a circular one.