changable tuning.. port questions

[abrhino 10+ year member]

on carstereo.com, if i plug in

2 Ports

5.88t X 6.5w @ 45hz = 17.93in Port length

1 Port

5.88t X 6.5 @ 32hz = 17.6in port length

 

[abrhino 10+ year member]

this is how im trying to do mine.. this was built locally by a shop who has since went out of business. with 1 port plugged, it sounded great and low daily.. pull the plug out and it meters awesome, i saw that setup do 149 legal and peak at 48hz in an Explorer.. it has never metered below a 148

 

[RAM_Designs 5,000+ posts]

why is the12volt and carstereo.com port calculators so far off? I pluged in my current box on the12v and it it was 3hz off of carstereo's calculations
current box

is 4.99cuft before port displacement.. port is 14.5h X 5.5w x 16.75d which equals 40hz on Carstereo and 43hz on 12v

I actually came up with ~44hz with the carstereo.com calc, considering that you'll have 4.15ft^3 after port displacement. This is also assuming you have already taken into account the sub's displacement. If not, tuning will go up another 1hz.

 

[abrhino 10+ year member]

so my current box isnt tuned anywhere near 40hz?

is my 2port design close to 45 and 33hz?

 

[RAM_Designs 5,000+ posts]

is my 2port design close to 45 and 33hz?

Depends what box volume you want to use. You also have to take into account that when you plug that port, it's now acting as part of the box and adding volume to the box.

 

[abrhino 10+ year member]

I want my box volume 2.5-3.5 after displacement. not really picky. i think my 2port design falls into this catagory..

unless i am not doin sumthin right.. i can "show my work" if i need to. so you correct my messups

36w X 14t X 17d external measurements = 34.5w X12.5t X 15.5d = 6684.375.

6684.375/1728 = 3.87 cuft

i'll be using a port separator that .75. the port height will be 12.5-.75= 11.75in . two ports so 11.75/2= 5.88ea port height

port area 5.88t X 6.5w X17.75L =678.405 /1728 = 0.39 port displacement per port .39x2 = .78cuft of displacement

3.87- .78= 3.09cuft after port displacement

 

[abrhino 10+ year member]

bump

 

[abrhino 10+ year member]

i used this PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES

calculate your vent length

square port- YES slot port-YES

number of ports- 2

enclosure volume- 3.87

desired frequency- 45hz

port height- 5.87

port width- 6.5

LENGTH- 17.89

number of ports- 1

enclosure volume- 3.87

desired frequency- 32hz

port height- 5.87

port width- 6.5

LENGTH- 17.6

i figured it as plugging one port removes the port, and tried to find a common port length, which was 17.6in and 17.89. i figured tuning wouldnt wouldnt be affected to badly if i used an average of 17.75in length

 

[bubbagumper6 5,000+ posts]

You can't sue the same enclosure volume for both calculations because when you plug the end of one of the ports, the volume that that port normally occupies, now becomes part of the net volume.

 

[the Answer 10+ year member]

use winISD

 

[RAM_Designs 5,000+ posts]

Have you thought about doing two ports on separate sides, then plugging one for them? It's a good deal easier to work the numbers that way.

 

[abrhino 10+ year member]

Have you thought about doing two ports on separate sides, then plugging one for them? It's a good deal easier to work the numbers that way.

i thought it but i was scared that 2 separate ports would take up too much volume

You can't sue the same enclosure volume for both calculations because when you plug the end of one of the ports, the volume that that port normally occupies, now becomes part of the net volume.

how drastic will it affect tuning and volume. any chance that it will be negligable and little effect?

use winISD

i have no idea how, but i will tinker with it

 

[abrhino 10+ year member]

im not super worried about the box volume. the DC will work fine in 2-3.5cuft. i just want the Tuning as close to 43-46hz and 32-34hz as possible

 

[RAM_Designs 5,000+ posts]

i thought it but i was scared that 2 separate ports would take up too much volume

Maybe a few tenths more, but you have plenty of room in that magnum anyways.

 

[abrhino 10+ year member]

true, i have hella space back there

whats worst case scenerio, if i do the 2 ports 5.88t X 6.5w X 17.75L ? im sure box volume will be fine , but how drastically off are my calculations? its not like i HAVE to be pinpoint accurate, but i'd like to be at least 32-35hz 42-46hz range