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cpcg32
06-28-2006, 05:44 PM
I am using WinISD to design a ported box. I want two ports, one on each side of the box so it's symetrical. My dimensions of the port are going to be 13.5"(.343m)x4"(.102m). When I tell it I want 2 vents, it says the length needs to be 18.197ft. That is abusurdley wrong. If I say one port, it tells me 8.831ft. That seems a little more reasonable but still kinda long. It is going to be a 1.88ft^3 box tuned to 26hz. Can anyone help figure out what the length of each port needs to be? Should I raise the tuning frequency?

xluben
06-28-2006, 07:19 PM
Your ports are way too big, that's why it needs such a long length.

In a box that small and tuning that low you have way too much port area.

I think two ports is not a good idea. You'll end up having to make your box way bigger to make up for the port displacement.

I played a little with WinISD and it looks like you'd only need on 3" dia. round port, 13" long to get that tuning. So if you must to a square port, just look to match that port area, and the length should be similar.

cpcg32
06-28-2006, 07:37 PM
I really want 2 ports because I am going to mount the sub in the middle and have the box be symetrical. Any suggestions?

xluben
06-28-2006, 08:46 PM
little square ports?

if you really want two they're gonna have to be small.

just go to the 'rear port air velocity' tab of WinISD and make sure it doesn't get over 17.5 m/s

tRiGgEr
06-28-2006, 08:54 PM
you're planning on a 1.88ft^3 box for two subs??? And 108 cubic inches of port area is retarded and **** near impossible for a 1.88ft^3 box...

xluben
06-28-2006, 08:57 PM
i think it's only one sub, but the port area is still way to much for that size box (as winisd has shown you).

neonrt
06-28-2006, 09:01 PM
whats the sub?? if you want 2 ports go like 13.5" x 1" for each, i know thats out of the 1-8 ratio, but with 2 you should be fine. try that and see what length you come up with.

xluben
06-28-2006, 09:35 PM
whats the sub?? if you want 2 ports go like 13.5" x 1" for each, i know thats out of the 1-8 ratio, but with 2 you should be fine. try that and see what length you come up with.

seems reasonable, but two ports in the box just doesn't work well. with two 13.5 x 1 ports they'd have to be 55 inches long!

i'd have to say it's not possible to do without port noise and without 3+ foot long ports.

just go with 1 port, maybe 13.5 x 1 x 26 long and you're close to 16.5 m/s port air velocity (just under port noise, hopefully).

or go with a bigger box

or tune to 32 or something more reasonable

cpcg32
06-30-2006, 03:30 PM
I will give some details as to why I want to design the box like I am. I am going to mount the sub in the back of my Forrester which is 37" wide between the wheels. I want the box to occupy this whole space. I want to mount the sub in the middle of the box and have the face be atleast 27" as I am going to put plexi windows in the front (the yellow area in picture A). The other alternative I cam up with is to make a sealed box, again with the 27 " face but put "cut off" the corners as seen in picture B (top view) to bring the space down to about 1.2ft^3 and seal of the edges between the wheels with mdf. I am going purely for SQ, I am going to use 1 eD 13Ov.2.

SQBubble
06-30-2006, 08:33 PM
seems reasonable, but two ports in the box just doesn't work well. with two 13.5 x 1 ports they'd have to be 55 inches long!

i'd have to say it's not possible to do without port noise and without 3+ foot long ports.

just go with 1 port, maybe 13.5 x 1 x 26 long and you're close to 16.5 m/s port air velocity (just under port noise, hopefully).

or go with a bigger box

or tune to 32 or something more reasonable

well isnt it 55inch long both ports together with winISD, 55/2 = 27.5" each port?...

sry to jack but just wanna know, is there difference with 2slot port (13.5x1x26) vs 1slot port(13.5x2x52) when talking about SPL and SQ??

xluben
06-30-2006, 08:42 PM
wait, with winisd you have to divide the port length by the number of ports!

i've been designing my box all wrong then.

someone please confirm this.

SQBubble
06-30-2006, 08:45 PM
wait, with winisd you have to divide the port length by the number of ports!

i've been designing my box all wrong then.

someone please confirm this.



ya, wut box u designing?

xluben
06-30-2006, 10:36 PM
i'm trying to figure out a ported box for my two, 12" assassin's.

right now i have them in 1.25 ft^3 each, and i want more spl.

it's gonna go in the trunk of my accord so i'd like 32"W x 14"H x whatever depth needed (but I'd like to keep it around 20" max).

i was thinking two, 4" dia flared ports to get the most net box volume in that space. winisd was telling me 17", so i was thinking two 17" ports. is it really two ports that are 8.5"???

according to winisd that should be enough port area to avoid port noise, but what i've read online, i think i might just go with one big slot port.

SQBubble
06-30-2006, 10:53 PM
i'm trying to figure out a ported box for my two, 12" assassin's.

right now i have them in 1.25 ft^3 each, and i want more spl.

it's gonna go in the trunk of my accord so i'd like 32"W x 14"H x whatever depth needed (but I'd like to keep it around 20" max).

i was thinking two, 4" dia flared ports to get the most net box volume in that space. winisd was telling me 17", so i was thinking two 17" ports. is it really two ports that are 8.5"???

according to winisd that should be enough port area to avoid port noise, but what i've read online, i think i might just go with one big slot port.

why? there is disadvantage of doing 2slot ports?
ive been thinkin doing 2slot port for my 15inch arsenal and i figured it saves up good amount of space compared to 1slotport... im doing 3.8cu.ft NET @30hz, but wanna be 100% sure 2slot port are same thing as 1slotport , i dont know the difference and not lot of people does that i realize, dunno why... can someone clarify 2slotport and 1slotport thing and is it just half of 1big port or is there other calculation/things we should consider with 2slotport?
thx

xluben
06-30-2006, 11:15 PM
i'm pretty sure there's no way 2 slot ports are going to displace less than one large slot port (assuming they both tune the same), but i could be wrong.

i was just going to use one big slot port because:

more port area, gaurantee no port noise (my two 4" port idea might not be enough port area)
easy and cheap

SQBubble
07-01-2006, 12:58 PM
i'm pretty sure there's no way 2 slot ports are going to displace less than one large slot port (assuming they both tune the same), but i could be wrong.

i was just going to use one big slot port because:

more port area, gaurantee no port noise (my two 4" port idea might not be enough port area)
easy and cheap



alright, check these 2 plans i did...:

they have the exact same external dimensions,
width: 37"(35.5")
height: 16.5"(15")
depth: 18"(16.5")
wood thickness: .75"

but with 1 slot port i can make it only 3.3cu.ft NET(sub in the enclosure) @32hz with 40inch of effective port length
instead...
with 2 slot port, im able to squeeze 3.8cu.ft NET(sub in the enclosure) @30hz , each port having 20inch of effective lentgh
pics speaks for itself...

AND, i still have 60sq.inch of port area( (15x2)x2 )

only thing is I dont know any disadvantage of 2slotport, did someone already build a 2slot port enclosure and tell how was it, any port noise, weird sound out of it..etc?

thx yall

xluben
07-01-2006, 01:56 PM
equal port area and half the length just doesn't make sense to me.

it is my understanding that if winisd say 40" that is for each port, not total.

please correct my if i'm wrong.

SQBubble
07-01-2006, 02:05 PM
well generally when the port is smaller u need less length to tune lower... so it kinda make sense..

lets just wait for someone that know these stuff pretty good and could help us both and clarify this

SQBubble
07-01-2006, 06:49 PM
ttt, anyone?

xluben
07-01-2006, 06:52 PM
check out the second post of the thread:

http://www.caraudio.com/forum/showthread.php?t=168455

i think you'll better understand why you need two 40" ports.

basically boils down to, same total port area, same total length.

SQBubble
07-02-2006, 07:38 AM
check out the second post of the thread:

http://www.caraudio.com/forum/showthread.php?t=168455

i think you'll better understand why you need two 40" ports.

basically boils down to, same total port area, same total length.

well wut he says is that if u have double the port area then it needs to be much longer... me its the other way im doin' it.. half 1big port, therefore, I need less length to get lower tuning, beside that...

neonrt
07-03-2006, 02:05 PM
i am probally late in this post, but i am pretty sure that both ports would have to be the length win isd states, not the length divided by 2. not 100% though, never looked onto a dual port box.