Quick Box Question

[skirch56 10+ year member]

I want to put 4 RE re 8's in my explorer, and i want to go ported. How will sound quality be affected by either one big slot port verse two seperate chamber ported seperate? Also how many cubes should this box be, and how do i figure that in a ported box? How does the length of the port affect tuning?

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[skirch56 10+ year member]

anyone?

 

[skirch56 10+ year member]

still no answers

 

[slc72005 10+ year member]

I want to put 4 RE re 8's in my explorer, and i want to go ported. How will sound quality be affected by either one big slot port verse two seperate chamber ported seperate? Also how many cubes should this box be, and how do i figure that in a ported box? How does the length of the port affect tuning?

the only thing that i can see happening with 2 ports versus one is maybe a cause for a lttle more port noise.

the longer the port the lower the tuning freq.

example a 80sq port area that is 9 inches long in a 9cf box is about 39hz, if you go longer then 9 inches the tuning freq gets lower and lower. hope that makes sense

 

[yacob.naif 10+ year member]

all speakers should be an equal length from the port

so it may be easier to do it in 2 chambers

 

[Trixter 10+ year member]

all speakers should be an equal length from the port

what???

 

[slc72005 10+ year member]

as long as the subs arent firring directly into the port you will be fine.

meaning if you had the speaker mounted in the front of the box and the port is directly behind it on the rear of the box so the sub is unloading right into the port.

if they all had to equal distances from the port then why are there so many box's with the port on 1 side of the box then there are 2 subs next to the port? if people didnt have sucess with this design they wouldnt use it.

 

[Trixter 10+ year member]

if they all had to equal distances from the port then why are there so many box's with the port on 1 side of the box then there are 2 subs next to the port? if people didnt have sucess with this design they wouldnt use it.

umm...yeah...

 

[Trixter 10+ year member]

well, i guess i should reply that actually may be useful to the original poster....

first off i would do a single box for all 4 of them. i dont' have experience with the 8's so i have no idea what kind of volume thay require. your net volume is what we count. that is the internal volume minus the sub displacement and port displacement...even the material that the port is made of needs to be counted in the port's displacement. the tuning of the port comes from it's length, the shorter it is the highr the freq. and the longer it is the lower the freq. the more port area you have (the opening of it) the longer it needs to be to achieve a certain freq.

example: a port of 30sq" may need to 20"long to get 30Hz. but a port that has 60sq" may need to be 50" long.

the length of the port depende on three things: 1) the net box volume 2) the port's area 3) desired tuning freq.

if your good with numbers.....(i post this all the time)....

Lv = [(1.463 x 10^7 x R^2) / (Fb^2 x Vb)] - 1.463 R

Lv = port length

Fb = tuning freq.

Vb = box volume (cu")

R = radius of port (if using slot or square port then R = sq.rt of A/Pi)

you'll need to do the math, internal w/ sub displacement, to get the length of the the port. once you know the length, you'll need to find it's displacement (including materials of construction) and do the math again...subtracting the port displacement from the Vb...to get you actual number. (really you can keep going back and forth but the difference is so small it don't matter, once is enough.)

also, if the port shares a common wall with the box (most slot ports) you need to account for the port correction factor. this is done by adding 1/2 of the port's width to it's length.

 

[skirch56 10+ year member]

the box i drew up gives about a .65 ft^3 per sub befot their own displacement. It is divided into two chambers. I have a port on each end, which are about 20 inches long, and 2 inches wide.