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Music is life
11-05-2009, 07:15 PM
How do I calculate a slot port?
The cab will be 3.7 cu ft tuned to 48 Hz and the width of the slot opening will be 16" wide. I want a slot port at the bottom of the cab, the full width across the bottom.

According to this place:
http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL%20Port%20lenth%201.htm
16" wide, 2.75" high = .43" deep (close to the thickness of 1/2" Baltic birch).
I'm surprised that this is so different from depth of the size of a regular port of the same square inches.
Do you think I can trust this calculation?

Thanks in advance.
billfitzmaurice
11-05-2009, 07:57 PM
Do you think I can trust this calculation?

Thanks in advance.I get about 8 inches.
Music is life
11-05-2009, 09:10 PM
I get about 8 inches.

Yes! (and thanks Bill for the input)
8.43" is the length of a square port.
But when the "Are You Using a Slotted Port?" button there is clicked "yes" it changes to .43". I don't think I trust this calculation.
I've used it for round ports and had very good results every time.
billfitzmaurice
11-05-2009, 10:27 PM
Yes! (and thanks Bill for the input)
8.43" is the length of a square port.
But when the "Are You Using a Slotted Port?" button there is clicked "yes" it changes to .43". I don't think I trust this calculation.
I've used it for round ports and had very good results every time.With very narrow slots the added friction of the air within the port will lessen the required length, but not from 8 inches to a half inch. I just tried that calculator and it gave a 7 inch length. I think that's a bit short, but at least within reason.
Chris Roemer
11-05-2009, 10:29 PM
Yes! (and thanks Bill for the input)
8.43" is the length of a square port.
But when the "Are You Using a Slotted Port?" button there is clicked "yes" it changes to .43". I don't think I trust this calculation.
I've used it for round ports and had very good results every time.

And WinISD ( beta - at www.linearteam.org ) gives me 6-3/4" long, if opening is 16" x 2.75". If it was only .43" long (same opening), it would tune the box to about 66 Hz.
Music is life
11-06-2009, 07:37 AM
Thanks very much the help Bill, and Chris.
I'll experiment in the 6 to 8 inch range before made permanent.
It will not be that hard to make replaceable pieces that fit in nice and tight but are interchangeable.