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View Full Version : Sealed Box for 8"...need direction...

Jazz
02-21-2008, 09:02 PM
Hi,
I posted this in the Subwoofer section by accident...it belongs here.:crap:

I designed this box to fit right behind my shock tower. It is as big as i can possibly make it...if i HAVE to go bigger, i cannot put it behind the shock tower where it will be out of my way. Space is a big issue.

I would like to know if in general this box will work out well or if it will be a total flop? I am willing to give up some performance in order to keep it out of my way.

I have not purchased a 8" sub yet ...still shopping around.
Obviously the box is not a perfect square, it is kind of trapezoid-ish.
http://i203.photobucket.com/albums/aa8/Mudkicker99/8box.jpg

IDSkoT
02-22-2008, 12:05 AM
Well, I did the math... it's .27177 cubic feet of air space.
So if you can find a sub that has a sealed air space of somewhere near there, it'll be fine.

Jazz
02-22-2008, 07:44 PM
Well, I did the math... it's .27177 cubic feet of air space.
So if you can find a sub that has a sealed air space of somewhere near there, it'll be fine.

The sub that i am looking at right now requires 0.3 cu.ft.

if i understand correctly, having the proper air space is more important than the actual "shape" of the box?

in order to get to 0.3 cu. ft. i can only go "upwards" and make the box taller. Would that be ok?

how did you calculate the cu.ft. from the drawing?

thanks
Jazz

skydeaner
02-22-2008, 10:35 PM
If you can figure out how to post those drawings you posted and cant figure out how to figure area in a non square area, you are lying.

Jazz
02-22-2008, 11:28 PM
If you can figure out how to post those drawings you posted and cant figure out how to figure area in a non square area, you are lying.

Why would i lie?

My brother made the drawings for me after i explained to him what i needed.

I dont know how to do the math with this one because it is not square.

Mostly i need to know how much of an impact an irregular shaped box will have on sound and performance.

Hope someone can help me out.

Thanks
Jazz

BrianChia
02-23-2008, 12:02 AM
If you can figure out how to post those drawings you posted and cant figure out how to figure area in a non square area, you are lying.

They don't teach area of a trapezoid in Canada :fyi:

Just messin, find the area of the trapezoid ((1/2 side1 + 1/2 side2) * height) and multiply area by depth to get volume.

IDSkoT
02-23-2008, 12:16 AM
You could definitely go higher. Going over or under will, of course, effect how it sounds. But, I'm not sure how big of a difference that would be. If you can, make it an inch or two taller. Should be okay from there.

Blove1991
02-23-2008, 12:52 AM

SPY
02-23-2008, 01:34 AM
1" taller would give you .3037 ft^3

Your sub needs .3 ft^3 but you have to subtract the displacement of the sub from your box and then still have .3 ft^3

If you psoted up the specs for the sub your looking at I'm sure we could all be a little more helpful.

Jazz
02-23-2008, 08:29 AM
1" taller would give you .3037 ft^3

Your sub needs .3 ft^3 but you have to subtract the displacement of the sub from your box and then still have .3 ft^3

If you psoted up the specs for the sub your looking at I'm sure we could all be a little more helpful.

Sure
here you go
http://manuals.harman.com/JBL/CAR/Boxes%20and%20Parameters/GTO%20804D.pdf

thanks for all the help BTW.
nobody really answered my question about how an irregular shaped box will affect the sound?

thanks
Jazz

savagebee
02-23-2008, 08:32 AM
in a sealed application, it wont
you'll be fine with that

SPY
02-23-2008, 04:01 PM
It looks like the .3 ft^3 includes the displacement so you should be good with just 1" taller.

As for the shape it doesn't really matter, some subs require a min distance from the rear of the sub to the rear of the box but I don't think you have to worry about it in this case.

IDSkoT
02-24-2008, 03:49 AM
x2

You should be fine. Good luck with the build, it'll probably be hard unless you have a table saw.
Post build pics.

BrianChia
02-24-2008, 03:54 AM
Shouldn't be too hard with a circular saw. Just draw straight lines and have a good sturdy angle adjustment on the boot.

IDSkoT
02-24-2008, 04:16 AM
Shouldn't be too hard with a circular saw. Just draw straight lines and have a good sturdy angle adjustment on the boot.

Eh, what about the angled cut he needs to do for the front? Unless you expect him to sand it down. :P

BrianChia
02-24-2008, 04:20 AM
"Good sturdy angle adjustment on the boot" FTW. ;)

Jazz
02-24-2008, 10:43 AM
I will have access to a table saw so it should no be too bad. for sure there will be some tricky cuts.

what about Polyfill? Do i need it? If so, what is it and what does it do? :crap:

Jazz
02-26-2008, 01:21 PM
The JBL manual does not specify how "deep" the box has to be. The mounting depth is 4 3/8 on this sub.
My box will be 9 1/4 inches "deep"...i had to shave off 3/4" off of the depth for better fitment.
Should it be ok?

thanks
Jazz