Can someone double-check my math?

[geowick07]

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

Thanks in advance!



geo

[psych0ticnemes1]

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]

not to thread jack but i see all of you guys using sketchup..link where i can download please?

[geowick07]

just google sketchup.



geo

[geowick07]

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]

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]

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]

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]

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]

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]

Ahh....ok. What a n00b box designer I am! lol

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



geo