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View Full Version : I've never built a box.



roper
12-02-2008, 08:22 PM
As the thread states, I have never built a box. I am designing one for the trunk of my '94 BMW 325is, where I am putting two 10" JL Audio 10W1v2-4's.

I need someone to look this over though. I'm not sure if I did this correctly, but my basic process was this:

- First, I looked on the JL Audio website for recommended enclosure dimensions, and they were as follows for a JL Audio 10W1v2-4:
[ 18.0 in. x 13.25 in. x 13.5 in. ]

According to the JL Audio page (at the bottom of this post), the resulting values would be:
Volume (net int.): 1.00 cu. ft.
Tune to: 31.0 Hz.
F3: 28.8Hz
(While i'm on the topic, what is the difference between Tune to and F3?)

- Before going any further, I measured my trunk to see if two of these could fit side by side. Unfortunately, my trunk was only 33" wide, so I had to come up with an alternative solution. (2 subs = 2 x 18.0 in. width = 36.0 in. width.)

- I can honestly say I wasn't sure how to go about changing sizes, but I did so using the following...
I calculated 18.0 x 13.25 x 13.5 to be 3219.75 cu. in.

Using this number, I came up with some other possible dimensions that would produce the same answer, and got something like this:
18.5 in. x 14.25 in. x 14.25 in. = 3218.55 in.

The problem with this is, these are the external dimensions, not the internal dimensions. I wasn't sure if that would matter, as long as I kept outside volume the same, and so I began to draw up a plan for my box, going by the pictures and lengths they provided. Here are the two drawings I produced:

Front:
http://www.trportfolio.net/upload/uploads/733856measure1.png

Above:
http://www.trportfolio.net/upload/uploads/439128measure2.png

These images are drawn to scale and created using JL Audio's recommended External Volume, Slot Width, Slot Height, Slot Height, and Port Extension Length.

My questions are:

1. Did I mess up my calculations or would the internal volume of this box still be around 1.00 cu. ft.?
2. Would this box be alright if I was to design it exactly how I have drawn it?
3. If I were to use this box, what would the specs be of it incase I was asked? 1 cu. ft. @ 31.0 Hz?

For any information regarding the subs, view this link:
http://mobile.jlaudio.com/products_subs.php?series_id=15

THANK YOU!

bonesninja
12-02-2008, 08:26 PM
F3 is a -3db cutoff frequency
and that port is too narrow in relationship to its height...might get some port noise

Twisted_0912
12-02-2008, 08:28 PM
**** sorry man ill get back to u on that design

roper
12-02-2008, 08:32 PM
Twisted, thanks, I just figured i'd learn something in the mean time.

Bonesninja, the port specs were exactly what they recommend at their website, and that is why I chose those dimensions. Thanks for your criticism man :D

EDIT: Realized this might have sounded sarcastic, but I completely meant it... i'm doing this to learn, and your post was a helpful pointer.

bonesninja
12-02-2008, 08:34 PM
Twisted, thanks, I just figured i'd learn something in the mean time.

Bonesninja, the port specs were exactly what they recommend at their website, and that is why I chose those dimensions. Thanks for your criticism man :D

i've built a few W6 spec'd boxes before and got some port noise at higher volumes...its more noticable in a truck or SUV versus a trunk car but it still might cause some issues

Twisted_0912
12-02-2008, 08:52 PM
http://i451.photobucket.com/albums/qq238/Twisted_0912/boxforroper.jpg

ill pm u the cut list:D

roper
12-02-2008, 10:24 PM
Twisted has provided me with an excellent design, 2.0 ft^3 @ 31.0 Hz...

Thanks guys.