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area51
12-02-2009, 02:58 AM
I would like to build a box strictly to burp with, the so called "fart box" but I don't know how to design one. Is there a trick to designing it? I see that the port is external to the box. Is that a sealed box ported? I need help please. Maybe someone could design one and explain. I got PayPal.

This is for two DD 1508s in a '97 Accord.
Max dims are
32" width
18" depth
16.5" height

FurbiesAndBeans
12-02-2009, 03:02 AM
Here's a basic run down of how to design a "fart box"

Find out your car's peak frequency.
Build a big (for your 8s it might be around 3 cu ft) box for your subwoofers.
Tune it to your car's peak frequencies.

And idk on this one, but i think the bigger the port, the better...

thegreatestpenn
12-02-2009, 03:06 AM
a big box hurts power handling so if you plan on putting way too much power to your subs, you want to make your box smaller than normal. Figure out which direction the port needs to face for optimal scores. most-likely your best configuration is with the box all the way back against the trunk lid (back bumper) with sub and port facing the cabin. it might be sub facing cabin and port perpendicular though, you should test to find out.

basscort2009
12-02-2009, 03:47 AM
1 find out cars resonant freq.
2 tune a little below it (5-7 htz) so it peaks at that freq.
3. build box way smaller than recomended
4. send about 3 times rated power.
5 only do it for about 3 seconds

PV Audio
12-02-2009, 11:03 AM
As stated, you really want a box with a very high Q which is usually done by lowering the airspace, as it gives you a HUGE peak in output right around tuning frequency. Everywhere else, however, it will sound like absolute garbage.

t1990le
12-02-2009, 11:05 AM
Y do u desire this "fart box"?

DNick454
12-02-2009, 04:22 PM
Y do u desire this "fart box"?

Burp boxes have one purpose and one purpose only. Why would you even ask why he wants it :confused: Is there another use for them besides posting up high TL scores and being acoustically unpleasing to the ears?

area51
12-02-2009, 04:48 PM
Thanks for the help guys, I know how I need to design my box now. Now the next question is, you guessed right, "How do I figure out what my car's resonant freq is?"

DNick454
12-02-2009, 05:32 PM
Use a term lab, play a sweep frequency and see where your car peaks at.

area51
12-02-2009, 08:14 PM
Should this be done with a sealed box since a ported one has it's own peak freq?

soundstreamer
12-02-2009, 09:22 PM
Run a sweep with a sealed box. Find what frequency you are loudest at. Tune your new box about 4 hz below your peak. Build the box stout, smooth, and air tight.

I don't think 2x 8" subs will load up very well with too much port, so keep it under 30 cubic inches of port per cubic foot of box.

Moe Lester
12-02-2009, 10:40 PM
Should this be done with a sealed box since a ported one has it's own peak freq?

You got it, now get to work! :smash:

area51
12-03-2009, 02:50 AM
Alright, I think I got it guys, thanks. :thumbupw: Now got to put it to work. :D