Number crunching

[Blu84Rex 10+ year member]

I am trying to figure out the math and I am getting stuck on the port length & tunning on a box for 2 12" type r's.

Outside measurements are 40" wide, 15" High, 15" deep.

Which brings the gross volume to 4.06ft^3 and after driver displacement 3.91ft^3.

The local stereo guy says that the port measurements should be

13.5" high

2.75" wide

15" deep

That would tune to 38hz

I would like to tune somewhere closer to 33hz. What would the length of the port have to be for that?

I also have a couple of math questions. How do I find out the displacement of the port and how do I measure the port? do I start from the outter face of the box and stop 2.75" from the back and start from the side and go over the remaining distance.

Click to read more...

 

[DBfan187 5,000+ posts]

Let me see here... I'm getting 33.3333 repeating of course.

 

[Blu84Rex 10+ year member]

Huh??

 

[phyphoestilic 5,000+ posts]

ur port length needs to be 33.33 inches to tune to 33hz

 

[DBfan187 5,000+ posts]

Let me see here... I'm getting 33.3333 repeating of course.

LEEEEEEEEERRRRRRRRRROOOOOOOYYYYYYY JEEEEEEEEEEEEEEEEEEEENNNNKKKKKKKKINNNNNNNNNNSSSSSS

 

[POLKAT 10+ year member]

Let me see here... I'm getting 33.3333 repeating of course.

Leeroy Jenkins? //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Sorry, but you have me on the math. I could prollly figure it out but I feel too lazy. A much easier thing to do is to click here: http://www.caraudio.com/forum/showthread.php?t=137804

and choose one of Moe Lester's stickied box plans. Scroll down to the ones that are 4 cu ft @ 33 hz or so and pic one.

edit: I guess some of the designs have broken links now.

 

[phyphoestilic 5,000+ posts]

LEEEEEEEEERRRRRRRRRROOOOOOOYYYYYYY JEEEEEEEEEEEEEEEEEEEENNNNKKKKKKKKINNNNNNNNNNSSSSSS

lol funny video. "Leroy u fu*ken as$hole"

 

[rpfuror 10+ year member]

Let me see here... I'm getting 33.3333 repeating of course.

ummm...

33" = 29.50 Hz on my calc.

23" = 32.90 Hz on my calc.

did you mis type?

 

[DBfan187 5,000+ posts]

ummm...
33" = 29.50 Hz on my calc.

23" = 32.90 Hz on my calc.

did you mis type?

 

[Blu84Rex 10+ year member]

I came up with 23" also for 33 hz but when I do it on carstereo.com i get 17.5" IS my math wrong? I would also Like to have the port in the center of the box . How would I go about that, would it have to be a T shape and how would I measure a T port ? The same as an L from center to center or different? Or would it just be better to have it on the side.