Help Fillin My Missing Numbers..

[n0ftInc 10+ year member]

So, tonight I ripped apart the old box and started to design the new one. The old one was a little too big and bulky for me, so for this one, I would like to downsize it a little bit. I worked out and figured on the dimentions of 12" x 36" x 18". Working with 3/4 MDF I am looking at 4.5ft^3 as external and 3.459ft^3 internal. This is before the driver (2 * .07) and port displacement ( ..?). I want to have the port along the 36" side, I am just having difficulty finding the correct length & width. I am aiming for 30

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[n0ftInc 10+ year member]

Quick Paint..

Port in Lime.

 

[Zerstorer 10+ year member]

if my math is correct, at 30hz, the port would be 12inches sq. and 7.5 inches long.

IE: opening: 6x2, 12x1, 24x.5, 3x4, etc. and 7.5 inches long. Depending on how you have it set up, the displacement will wiggle by a little. It will be at least .05 cubes tho.

JMac will have better and more accurate numbers by tomorrow, I bet. My #s are ballpark.

 

[Zerstorer 10+ year member]

Quick Paint..Port in Lime.

Having just now seen this, here are better #s:

36x1 or 18x2 at 26 inches deep for 30 hz

36x.5 or 18x1 at 12 inches deep for 30 hz

12x1 or 6x2 at 7.5 inches deep for 30hz

36x1 or 18x2 at 18 inches deep for 35hz

36x.5 or 18x1 at 8 inches deep for 35hz

12x1 or 6x2 at 4.75 inches deep for 35hz

Figure displacement from there and add a little to your OD to get it right.

Hope this helps!

 

[n0ftInc 10+ year member]

Thanks for the quick response. Wouldn't the port have to be 34.5" wide considering the .75" MDF? Also, if I were to make a port that had a small width (ie: 1"), would that give me port noise?

 

[bass maniak 10+ year member]

shouldnt give u more port noise as long as you have a reasonable overall port area //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[Zerstorer 10+ year member]

Thanks for the quick response. Wouldn't the port have to be 34.5" wide considering the .75" MDF? Also, if I were to make a port that had a small width (ie: 1"), would that give me port noise?

34.5... yes... well do one of the other options instead

 

[n0ftInc 10+ year member]

Alright, I have found a way to squeeze some more space. I have 4.29ft^3 to work with.. Same setup as before, just different values. This is with calculated speaker displacement. I still have the 36" and 12" in the new design. Therefore, I am going to have my port be 34.5" Wide & 1" Deep. What is left for filling is the Length. I am trying to achieve 31hz. //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif

 

[Zerstorer 10+ year member]

I'd wait for Jmac or a less newbish person than myself to make sure the math is right, but the port should be about 10-12" long

 

[LoneRanger 10+ year member]

first off, you're going to need more than 34.5 square inches of port for a pair of subs that need 4 cubes (i'm guessing a pair of 10's or 12's) i'd go for 1.5x34.5 or 1.75x34.5 for 10's or 12's respectively. If by chance you're using 15's, you could go as high as 2x34.5 or 2.25x34.5 depending on your application.

I'm not doing all the math for free, especially since I've been preaching on people to learn to do the formula themselves (IT'S SIMPLE ALGEBRA!!! IF YOU DON'T KNOW HOW TO DO IT BY NOW, IT'S ABOUT TIME YOU LEARNED!!) So the numbers I'm providing are quick calculations from WinISD Beta:

35hz

(1.5x34.5)x14.75

(1.75x34.5)x19.25

(2x34.5)x23.75

(2.25x34.5)x28.5

30hz

(1.5x34.5)x24.75

(1.75x34.5)x31

(2x34.5)x37.25

(2.25x34.5)x43.5

all of these calculations assume that the box is 4 cubes after all displacement. NEVER EVER EVER EVER figure the outside dimensions first. Figure out how much space you're going to need after all displacements are figured, then using the max dimensions of the place where the box will be mounted, come up with a combination of width, height and depth that equals 4 cubes + port and subwoofer displacement.

 

[Drowner 10+ year member]

I just ran the numbers using JL's formula and came up with...

4.29ft^3 @ 30hz: 34.5" x 1.5" x 30.1605725967"

Could someone verify this? //content.invisioncic.com/y282845/emoticons/nerd.gif.c6fa51ddf7ff75f1c0371fbc648f70ae.gif

 

[saywhat? 5,000+ posts]

and thats for a quality plan .......gnome audio is good too (lone ranger)

 

[LoneRanger 10+ year member]

Yeah, what Jmac said.

Either of us would be more than happy to draw you a nice set of plans with corrected port area/alignment and guaranteed extra wang for eight bones //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif