Double Check my Measurements Plz!

[Psyence 10+ year member]

Hi, Just built a box for my Alpine Type-R....

I have a total volume of 2.5 cft, and i was thinking about using a square vent, not a slot, but a perfect square...

I would like to tune to 36hz

I have come up with a 3.5"x3.5" port that I figure needs to be....

7.3" long...

Can someone that knows something about this double check my calculations?

Thanks.

Click to read more...

 

[PowerNaudio 10+ year member]

is that volume internal or external,

is that volume with or without the displacement of the port and sub.

what is the thickness of the mdf wood being used. are you using the same width of mdf for the port walls.

is there going to be any bracing used.

 

[Psyence 10+ year member]

That is the total internal volume including sub displacement.

3/4" MDF on port walls

No Bracing, that isnt accounted for already.

 

[PowerNaudio 10+ year member]

That is the total internal volume including sub displacement.
3/4" MDF on port walls

No Bracing, that isnt accounted for already.

did you account for the port

displacemet as well?

 

[Psyence 10+ year member]

No.

Also, check the dimentions again, i changed them slightly...

But this is the final measurements I came up with...

With the port @ 7.3" 5x5" external dimentions of the port...

would be 2.40

thus making hte port length required....

7.72"

Correct?

 

[PowerNaudio 10+ year member]

I have a total volume of 2.5 cft, and i was thinking about using a square vent, not a slot, but a perfect square...

I would like to tune to 36hz

I have come up with a 3.5"x3.5" port that I figure needs to be....

7.3" long....

that about right

did you take into consideration port noise?

 

[Psyence 10+ year member]

Well, I was going to round the edges of the port on both ends...

Anything else i can do?

 

[PowerNaudio 10+ year member]

Anything else i can do?

yes,

you can increase the port area by at least x3 . rounding the edges may help a hair, but sizing the port correctly will make the difference.

the port length is also going to increase so it makes sense to see how much available area you have for the box, since you may have to go with a bigger enclosure to fit the bigger port.

 

[Psyence 10+ year member]

Well...

Ive figured that if I go 2" x 10" x 8.6" slot type port...

I will have a reduced chance of port noise?

 

[PowerNaudio 10+ year member]

Well...
Ive figured that if I go 2" x 10" x 8.6" slot type port...

I will have a reduced chance of port noise?

that right there tunes it to like 40some Hz

whats the height of the enclosure? use that for the height of the port.

then do 4"~4.5" inches in width, then calculate the tuning off of that for the length.

 

[Psyence 10+ year member]

I cant do a concentional slot port... I have to have it in the middle of the top, because of angles, etc.

I was thinking to make the rectangle shape (the port) and fastening to the top in the middle...

I cant make it so that the port uses the back of the box as one side of the port.

 

[Psyence 10+ year member]

Well, now im just stumped....

Xmax = 18.1mm the manual says...

So I enter this into this calculator that i found giving dimentions for square ports... It says for that xmax @ 36hz I need the sides to be 6" or so

I enter that number into the port calculator, and it says 0" for the length...

If I leave it at the 6mm it has as default xmax for 'most subs' it says 3.42" for the dimentions...

So I dunno what to do //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

So basically, i need the square port dimention for the 2.4cuft box tuned to 36hz... and its gotta be somewhere around .... 7-8" in length...

This is the shape of the box, and you can see why I can not have a slot port. The sub is on the angled part facing forward, so the port has to go on that top piece.

 

[PowerNaudio 10+ year member]

OK after seeing the kind of enclosure. its a little different but still doable.

now

what is the height of that panel where the sub is going to be on?

are you using a 10" or 12" sub.

what is the width of the box?

and what is the total height of that box?

do you have a more clear pic of the box with some numeric dimensions.

i can help you calculate if i had a more detail drawing or picture of the enclosure.

btw that box looks pretty cool

 

[Psyence 10+ year member]

Okay... I ve decided... and it fits.

1.5" x 10" x 9.8" - Non Slot Port

This should be perfect.... Volume after port & sub displacement = 2.42cuft.

Word.

 

[PowerNaudio 10+ year member]

whats the tuning freq on that?