View Full Version : need ported dimensions ASAP
09-13-2003, 10:37 PM
:crying: I am planning to build a custom install in my car 2morrow, but I need to know the size of the box. I have a brand new e12k (flat cone) that I would like to put in a ported enclosure. These are the exact specs I want the box to be, can someone put my thoughts/wants into reality with actual dimensions.
I want the enclosure to be 2.0 cu ft. after displacement and port tuned @ 30 HZ. Can someone please figure out the dimension combinations that can make this possible. Please!!
09-14-2003, 11:19 AM
It makes things a lot easier when we know the dimensions of the space you want to work with. (Maybe a box that I may come up with would be too long or something.)
09-14-2003, 06:13 PM
after displacement. Height - 14" Width - 19' Depth - 18". That is 2.089 Ft^3.
for the port, it will be 2" wide and 12.5" long. the Port will be 31.56" long for 30hz. that will give u 25 in^3 of port area.
for the box, sides will be 12.5 x 18 Top and bottom will be 19 x 18 front and back will be 12.5 x 17.5
i did this all on http://www.eatel.net/~amptech/elecdisc/caraudio.htm it calculates everything for u
09-14-2003, 06:32 PM
2.089 ft^3 is GROSS VOLUME, not net volume :p
Vb = Vg - Dv - Dd - Db
Vb = Net Volume
Vg = Gross Volume
Dv = Vent Displacement
Dd = Driver Displacement
Db = Brace Displacement
the way i do it is i get the box dimensions and GROSS volume then plug the number into WinISD to get the port lengths and stuff. Im doing this right, right?
09-14-2003, 06:41 PM
Nope, because if you enter the gross volume into WinISD, it'll give you port sizes as if the gross volume were the net volume. So, let's say you have 2 ft^3 gross and it gives you a 4" round port that's 12" long for your tuning frequency of 33.6 Hz. Well, the typical 4" round port is about 4.5" in diameter (outside), so the port will displace 0.1 ft^3. Then let's say the driver displaces 0.1 ft^3 and you don't use any bracing.
So it turns out your enclosure is 1.8 ft^3 tuned to 35.4 Hz ...
i see, on the Eatel site it gives u gross volume and net volume. If i plugged in the Net volume into winISD then that would be right? because i dont see how u could get the displacement of the port before even figuring out the lengths and stuff ya kno.
09-14-2003, 06:57 PM
I just choose a length, find out what it's tuned to, then adjust port length accordingly to get optimal tuning. It's not as easy as one may think ...
Also, eatel.net's calculator isn't 100% accurate either. I can spot a few problems, especially with the Square Port calculator.
1) It only uses displacement as if it were a straight port.
2) It doesn't take into account material used to make the port (i.e. PVC or MDF) which does take up space, especially in the case of MDF.
3) The square port calculator isn't exactly accurate.
It's close to being accurate, but not quite ... I don't recommend it for tuning enclosures that use a slot port partially because the calculator is wrong, but also because if you curve your lost port, the only accurate way to find vent displacement I've found is to draw it out on paper and figure it out for yourself.
yea ur right it must not be too accurate cuz its giving me the same gross and net volume. thats why i didnt pay attention to it. Can i talk to u on AIM?
09-14-2003, 07:06 PM
i put Jmac279 on my yahoo buddy list my SN is Muchacho_28