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View Full Version : Can someone double-check my math?

geowick07
04-16-2009, 02:30 PM
I am in the process of designing a new enclosure for my 12" CVR. I have gotten to the point where I would like some confirmation. So, can someone please check my math for me, and see if this is correct?

Specs:
External dims - 22W x 14.5H x 18D
Port dims - 2W x 13H x 22.5L
Tuning - ~32Hz
Sub Displacement - .07 ft^3
Sub Xmax - 12.64mm

This is my first time designing an enclosure without using one of those online calculators, so be easy on me!
I would do a sketchup, but I have failed miserably the couple times I have attempted to use it :crap:

geo

psych0ticnemes1
04-16-2009, 02:36 PM
I'm assuming you want a net volume of 2 cubes? If so, your math is correct... HOWEVER, according to this calculator your port should be 29 inches long.

http://www.carstereo.com/help2/Articles.cfm?id=31

MikeCole89
04-16-2009, 02:39 PM
not to thread jack but i see all of you guys using sketchup..link where i can download please?

geowick07
04-16-2009, 02:40 PM

geo

geowick07
04-16-2009, 02:41 PM
I'm assuming you want a net volume of 2 cubes? If so, your math is correct... HOWEVER, according to this calculator your port should be 29 inches long.

http://www.carstereo.com/help2/Articles.cfm?id=31
Yeah, sorry. 2 ft^3 after all displacements.
Hmm...29"?

Gonna have to rerun my math, I guess.

Thanks for the reply!

geo

psych0ticnemes1
04-16-2009, 02:42 PM
Yeah, sorry. 2 ft^3 after all displacements.
Hmm...29"?

Gonna have to rerun my math, I guess.

Thanks for the reply!

geo

No problem. How did you calculate port length?

geowick07
04-16-2009, 02:45 PM
I used dimensions on another box I built, and just adjusted. I guess my adjustments were wrong!

But, if I lengthen the port, that would throw off the internal volume, no?

geo

psych0ticnemes1
04-16-2009, 02:50 PM
Yes. Your other dimensions would have to increase. I think if you bump your depth up to 18.75 or 19.0 you'll be set.

geowick07
04-16-2009, 02:54 PM
Ok.

Currently, my port pieces would be 14.5 x 13 x .75 and 8 x 13 x .75.
If I increased the second piece to 14.5 long also, that would make the port 29". Which would decrease my volume by .03 ft^3. That wouldn't be that much of a change, would it?

geo

psych0ticnemes1
04-16-2009, 03:01 PM
Your port pieces don't have to add up to the expected port length for the tuning to be correct. This is because port length is measured down the middle of the port, not along the port wall. Plus, the port extends 1/2 the width of the port past the second port piece.

geowick07
04-16-2009, 03:03 PM
Ahh....ok. What a n00b box designer I am! lol

Well, ok...back to the drawing board!

geo