Is the tuning freqency of a box determined only by the port area, or also by the dimension of a port? For instance, If I had one port that was say 12" high x2" wide x 10" deep that caused a box to be tuned to 36hz that would be 240"^2 of port area. If I had a 10" high x 4" wide x 6" deep port also being 240"^2, would it still be tuning the SAME box to 36hz?

Thanks

the length and area must be consistant along with the volume of the box for it to be tuned the same. so the answer is no.
and 12x2 is not the same area as 10x4

Right. Tuning is a combination of box volume, vent diameter, and vent length. Changing any of the three alters tuning.

Ok lets see if I have this right here....

In addition to enclosure volume, the depth/length of the port MUST be constant too?

Also, if the port is say 10" tall by 2" wide, can I change it to 8" tall by 2.5" wide to keep the same tuning?

So basically the 3 constants here to follow are:
1)Enclosure net volume
2)Port surface area
3)Port Depth

...where every other dimension involved can be altered, correct?

This also puts my first assumption to death:

the AMOUNT of port volume doesn't determine tuning fq

it is the AMOUNT of depth and AMOUNT of surface area

Correct. Area and volume have a direct relationship - that means that as the vent gets bigger in area it also has to get longer.

To figure tuning of your current enclosure
Fb = 0.159*Sqrt[Av*1.84*10^8/(Vb*1728*(Lv+0.823*Sqrt(Av)))]

To figure the length needed to tune your enclosure to the desired frequency
Lv = Av*1.84*10^8/[Vb*1728*(Fb/0.159)^2] - 0.823*sqrt(Av)

Lv = Length of port in inches
Av = Port area in square inches
Vb = Net internal volume of enclosure in cubic feet
Fb = Tuning frequency of enclosure in hertz
Sqrt = Square root

[ August 27, 2004, 05:03 PM: Message edited by: Jmac ]

Thanks guys for the help.


Jmac, I will definitely use that forumula soon before building the box to make sure I am getting the correct Fb.

go here: http://www.carstereo.com/help2/Articles.cfm?id=17

also really helpful: http://www.carstereo.com/help/Articles.cfm?id=31