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jiggy2dmax
01-04-2005, 11:13 PM
I got a veryyyy nice box from a customer today but I have no idea what its ported to. The dimensions are

Width- 18"
Lenth- 12"
Height- 12"

The port opening is about 1 1/4 inch and each part of the port is 1 1/4 inches apart and are two pieces, 10 3/4 each.

bcarpenterfhl
01-05-2005, 12:42 AM
The port opening is about 1 1/4 inch and each part of the port is 1 1/4 inches apart and are two pieces, 10 3/4 each.

what?!?!? are you saying the port width is consistently 1 1/4 in., and the length is 10 3/4 in.? how tall is the port? does it make an "L" shape?

sumone
01-05-2005, 12:43 AM
is this an L-shaped port...hard to understand from your wording...

you don't say how the port is oriented...

if it is an l-shaped one...

1. figure out the port length = Lv

2. figure out & subtract the port displacement from the gross interior volume = Vb

3. figure out the port area (1.25 * whatever) = Av

Solve for Fb in

(Av*1.84*10^8)/(Vb*1728*(Fb/.159)^2) - 0.823*Sqrt[Av]

or

TunFreq[Av_, Vb_, PLen_] := Sqrt[1/(((PLen + 0.823*Sqrt[Av] )/(Av*1.84*10^8))*(Vb * 1728)) * .159^2]

jiggy2dmax
01-05-2005, 05:28 PM
ok sorry for the crappy a\$\$ explanation. The port lenth is 1 1/4 throught out. Its not a "L" port. It has two pieces of wood adjacent to each other forming the port and each is 10 3/4. The port is also 12inches high. Thanx guys.

negativezeroz
01-05-2005, 05:32 PM
you know how about you draw everyone a nice pic in paint ;)

jiggy2dmax
01-05-2005, 09:29 PM
well heres a pic:http://img.photobucket.com/albums/v343/jigga123/box.bmp

pwnt by pat
01-05-2005, 09:37 PM
That's freaking tiny, even at 640x480. To keep the size down, save as a JPG.

jiggy2dmax
01-05-2005, 09:37 PM
Sorry the pic didn;t come out very well. Basically the port is 1/ 14 inches wide, 12 inches long and not a L shape. It has two port boards that are 10 3/4 inches long.

supa_c
01-05-2005, 09:40 PM
Laberynth(sp?) port

mrray13
01-06-2005, 12:05 AM
if ur measurements are external and the box is 3/4mdf.....the tuning is close to 45hz

if the measurements are internal....the tuning is about 36hz

the port is about 24 5/8" long..

if i got the port length correct, those numbers were provided by bb6p

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee :peace:

Str8Up
01-06-2005, 05:29 AM
Hey,

What about a box with external dimensions 26"W x 17"H x 16"D using 3/4" wood.
And the vent is 31" x 15.5" x 2"....What is the box tuned too? Btw, take away .2 cubic feet because that's how much my sub displaces.

I'm hoping it'll be tuned around 31-33hz for my 15AE. I just don't know who I'll get to build it yet :confused:

mrray13
01-06-2005, 10:35 AM
tuned about in between 34-35hz, according to bb6p

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eee :peace:

Str8Up
01-06-2005, 04:01 PM
tuned about in between 34-35hz, according to bb6p

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eee :peace:

Thanx man. It's weird how different calculators tell different things. My calculator I use says between 32 and 33hz. O well, in-car it probably won't be 3db down until around 28hz or something anyway, which is fine.

Thanx again. :D

mrray13
01-06-2005, 05:42 PM
Thanx man. It's weird how different calculators tell different things. My calculator I use says between 32 and 33hz. O well, in-car it probably won't be 3db down until around 28hz or something anyway, which is fine.

Thanx again. :D

no problem..and ur pretty close either way.

i build boxes..pm me...

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee :peace:

jiggy2dmax
01-06-2005, 10:47 PM
dam 45hz, dats suxx. Anyway I can lower it, I would think by expanding the port lenth? If I can how much more port do I need to get it to about 33- 34 hz?

Raven
01-06-2005, 10:50 PM
You would have to make the port slightly smaller, area wise, not length. Just lengthening the port makes for less volume overall, which raises the tuning frequency of your port.

jiggy2dmax
01-07-2005, 12:06 AM
awww dam i guess its to the trash it goes.

sumone
01-07-2005, 02:04 AM
three choices:

by doing only ONE of the listed things...the effects are listed

1. increase port length
...however, increasing port length increases its displacement, thereby reducing the net volume Vb.

2. increase internal area (Vb)
- polyfill?

3. decrease port area.
- port displacement & Vb remain constant. I think this would be the most convenient of 'em all except if #2 works....