WinISD port length help

[cpcg32]

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?

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[xluben 10+ year member]

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]

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 10+ year member]

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 5,000+ posts]

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 10+ year member]

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 10+ year member]

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 10+ year member]

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]

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 10+ year member]

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 10+ year member]

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 10+ year member]

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 10+ year member]

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 10+ year member]

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 10+ year member]

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