mustangowner

05-11-2005, 10:20 AM

when designing a slot ported box, do you include the port area in the volumn of the box? say you have 2 subs that need 1.25^3 per sub, so that equals 2.5^3. would i need to add the port area to that or would that include the port?

GCAdidas13

05-11-2005, 11:26 AM

No. It's really difficult in my opinion, on how boxes are calculated.

If you have a box that is one cubic foot, and 12" in every direction... and you have a 2"x2" port, you have to take the volume that the port displaces out of the NET volume.

12x12x12 would be 1728cubic inches GROSS

taking out a port that is 2"x2" and 10" long (after accounting for MDF too) would be 3.5x3.5x10, or 122.5cubic inches

1728 - 122.5 = 1605.5 cubic inches NET. which also = 0.93 cubic feet NET.

put it on paper, and use basic geometric shapes to find areas and volumes of the box.

then, when you have all your areas and dimensions figured out you can use the calculator to work it.

personally i like to design an entire box first. design the enclosure, and the port just by guessing. then you can plug all the numbers into a calculation (the one at the bottom of this post) and find out what frequency the box is tuned to.

all of your inputs have to be in INCHES, SQUARE INCHES, or CUBIC INCHES, and the output will be a single number, the TUNING FREQUENCY.

.159*sqrt((A*1.84*10^8)/(V*(L+.823*sqrt(A)))))

A = port area

V = volume of the box NET

L = port length

GOODLUCK