Okay, I have to make 2 ported boxes for 2 pioneer TS-W1240C's to sell in order to be very close to placing my order for my first rl-p 15". I am having a problem with my calculations for port length. i used this formula:

x = cross sectional area of port (inches^2)

y = net volume of box after displacements (inches^3)

z = tuning frequency of port (hz)

PL= Port length (inches)

x[1.84 * 10^8]

_______________ - .823 * \/ x

PL = y[z\.159^2]

with x=52, y=3276, and z=33

i came out with a port length of 22368.8 in. Obviously thats not right. so help me out. where did i go wrong?

if no one wants to do the math then what do you think if i do a 13"highx14"deepx18"wide box with a 4x13 port that ends an inch a away from the back wall. so 13" long port. will it work? what will the frequency be?

gimme a few minutes...

what's wrong with the port dimensions i gave u over at ca.com? u don't trust me?? lol...but i will use the formula...

and in ur second post...u have to have the port at least as far away from the wall as it's width..if u do a 4x13 port, it has to be at least 4" away from the back(or whichever)wall...

be right back..lol..

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

if i remember correctly, ur wanting 1ft^3 tuned to 33 hz correct...ok..

u can't use a 4x13 port in that size box, the port would need to be over 102" long according to bass box 6 pro...

the way u have the formula written, i got a port length of over 2900"....

ur box is too small for a large port. ur going to need to tune higher, run a larger box or use a smaller port.....

using a box 13x14x18 (assuming 3/4 mdf is used), ur port can be 4x1.5x10.75 to get the wanted tuning freq.

hope that helps.....

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

Thanks mrray! i appreciate the help. i do believe i will be using those exact dimensions. the 13x14x18 is exactly what i wanted and using like 3 different calculators i somehow came up with a 4x13x11.5 port using 1" MDF but i will use yours instead. Sorry if i missed your help the first time. i try to keep track of my posts on ca.com but they dissapear so quick. Again, thanks for the help. if these end up looking the way i want them, they will be very impressive. I'll be posting pictures soon if i can figure out how to do it.

Wait a tick..... how do i make a 4x1.5x10.75 into a box that big... lemme see if i can draw the way i thought it would look and hopefully you can tell me how to change it.

--------------------------------------------

. [ ] o o o .

. [ ] o o .

. [ ] o o .

. [ ] o o .

. [ ] o o o o .

.-------------------------------------------

thats pretty much how i picture it, with the port going from the top board to the bottom board which would be 13" so how do i make it to your dimensions?

The picture isnt coming out the way it should but imagine the o's are making the outer rim of the sub and its closer to the right side than the port side. and the .'s are the right wall of the enclosure. i'm sure you get the idea, its your basic looking box...

the port will fit easily in the box.....

on the surface, it's 1.5" wide x 4" long and it's 10.75" deep...won't interfere with the sub at all..

the box is 13" tall x 14" long x 18" deep right? the sub will be on a side that is 13" x14" correct? if so, move the port to a side that is 13"x 18" or put the port facing up . either way will work, and not affect sq enuff for anyone to tell.

also, 1" mdf is overkill for these subs/boxes. 3/4" is plenty large and in all honesty 1/2" would work with a little bracing...

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

hmmmm.... i just got all the pieces cut at home depot yesterday and the dimensions are 18" wide 13" tall and 14" deep.

i expected it to look like this

http://gallery.caraudio.com/pp/showphoto.p...&sort=1&cat=all

will a port with the dimensions you gave me still work for a box this shape?

yeah, it'll work..

make sure u put the sub on a side that is 14x18..or it's going to be a tight fit...lol

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

Maybe I got lost somewhere on the way, but didn't you say that your going to use a RL-p 15"? How is the box going to 15.5" tall externally and 13" internally?

Another side note, you should place the hole for the sub as far away from the port as you can. (Port on right side and sub to the most left you can.)

I haven't crunched the numbers for the port, but I trust you guys got it by by now...with all the back and forth you've been doing.

FYI: use this in the future for port length:

Fb= tuning freq.

Lv= vent length

R= inside radius of vent (for slot/square vent use: sq. rt. of A/Pi to find R. A= vent area.)

Vb= box volume in sq. inches

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

I have used this formula a lot and it's correct. It's actually the same as the one on the JL web site but is broken down into simpler terms, and I find it a little more user friendly. I have not seen the formula you used. It kinda looks like the JL one but it has a few different numbers and is switch around a little....maybe why you got a funky number.

Maybe I got lost somewhere on the way, but didn't you say that your going to use a RL-p 15"? How is the box going to 15.5" tall externally and 13" internally?

Another side note, you should place the hole for the sub as far away from the port as you can. (Port on right side and sub to the most left you can.)

I haven't crunched the numbers for the port, but I trust you guys got it by by now...with all the back and forth you've been doing.

FYI: use this in the future for port length:

Fb= tuning freq.

Lv= vent length

R= inside radius of vent (for slot/square vent use: sq. rt. of A/Pi to find R. A= vent area.)

Vb= box volume in sq. inches

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

I have used this formula a lot and it's correct. It's actually the same as the one on the JL web site but is broken down into simpler terms, and I find it a little more user friendly. I have not seen the formula you used. It kinda looks like the JL one but it has a few different numbers and is switch around a little....maybe why you got a funky number.

..yep u got lost...hehe

the box i helped him design are for a 12" pioneer. he is going to build two seperate boxes for a pair of subs to sell individualy in order to buy the rl-p 15....hehe

help some?

i also like ur port formula....it is simpler to understand..

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

I think what you use to determine ports is much easier.

What is the conversion factor to make cubic feet into square inches?

multiply by 1728.....

It's finnally done!!! well kinda.... the box is completely built and the sub is in and hooked up. it sounds soooooo good. thanks for all the help. havent carpeted it yet but soon, maybe this weekend. i have some pics of the beginning of the build and i'll take some of the finished product and post them. the wiring was the biggest pain in the *** i've ever had but i know what i'm doing now. the only problems left are the head unit sticking out of the dash about half an inch and the remote wire needs to be longer but it works for now. In comparison to just about every decent set up out there, its probably not very loud but compared to the two TS-1240C's i had in a sealed box, this one by itself in a ported is so much more impressive. i can't wait to get started on building a box for an r-lp. its gonna be sweet! big thanks to mrray for the help with the box. hope y'all like it as much as i do...

multiply by 1728.....

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Thanks, i usually use some kind of calculator so i always forget

I think what you use to determine ports is much easier.

:ph34r:

agreed!! it's what i used to help him with the pioneer boxes..hehe as well as the ranger box i built a couple weeks ago!!

but it's also nice to know some "regular oldfashioned" math to make sure...or just to play around with!

but i like the "new" way better!

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

multiply by 1728.....

Thanks, i usually use some kind of calculator so i always forget

but that's to convert to cubic inches not square inches..

hopefully that's what u were after!

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee:slayer:

multiply by 1728.....

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Thanks, i usually use some kind of calculator so i always forget

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but that's to convert to cubic inches not square inches..

hopefully that's what u were after!

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee:slayer:

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Well, i was trying to get the Vb so it would have to be sq. in. right?

Vb=net internal volume of enclosure=cubic inches

so if u have the cuft u'd multiply by 1728 to get cubic inches or divide the cuin by 1728 to get cuft.

help ya some?

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

Vb=net internal volume of enclosure=cubic inches

so if u have the cuft u'd multiply by 1728 to get cubic inches or divide the cuin by 1728 to get cuft.

help ya some?

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

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oh, but everywhere i find that equation it says Vb=sq. inch So i always get confused

oh, but everywhere i find that equation it says Vb=sq. inch  So i always get confused

really? what equation? now i'm curious.....and confused

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

FYI: use this in the future for port length:

Fb= tuning freq.

Lv= vent length

R= inside radius of vent (for slot/square vent use: sq. rt. of A/Pi to find R. A= vent area.)

Vb= box volume in sq. inches

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

I have used this formula a lot and it's correct. It's actually the same as the one on the JL web site but is broken down into simpler terms, and I find it a little more user friendly. I have not seen the formula you used. It kinda looks like the JL one but it has a few different numbers and is switch around a little....maybe why you got a funky number.

<{POST_SNAPBACK}>

Here and sounddomain says the same thing

Vb= box volume in sq. inches

Here and sounddomain says the same thing 

ok...now i'm real confused. i'm going tro copy this and put it in the fabrication section. i don't believe this is correct. why? there isn't anyway possible that volume can be in square anything..as square is 2 dimensional..ie height x length...or length x width..those will give u square. my backyard is 10000ft^2...u add in the 4 ft tall fence and the volume of my yard is 40000ft^3......1200in*1200in*48in/1728.

does that make sense?

and away we go..

hehe

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

OK, hold up...that was a mistake on my part. It is cu" not sq". The JL equation is in cu'....mine is cu" because, like I said before, it's breaks it into simpler terms.

I think when you seen the Vb in sq", is was simply a misprint, like I did. If it was in sq" it would make no sence and not even come close to working out.