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SSS 18734
09-15-2005, 07:13 PM
I posted a thread about this a while back, but turns out I entered the wrong T-S parameters :blush: , and thanks to member PowerNAudio i've been making a lot of progress.

Heres a new graph. The response is relatively flat, and has a nice little peak around 32hz. I'm going less for flat response and more for low end here. Basically, I want it to rattle the sh*t out of the car. :)

Box will be ~1.5 cu.ft. per sub, tuned @33hz
Slot ported: 3" wide port, 10" tall, 40" length.
Response curve is like so:
http://img50.imageshack.us/img50/8416/untitled1copy4tw.jpg (http://imageshack.us)

Im trying to make this box as shallow as possible, with a divider in the center so both subs have seperate airspace, with both ports firing out of the middle of the box so it will be easier to make indented sides. Plenty of bracing also.

I've got a few questions.

1. Would the port I am planning on using be large enough to avoid port noise? Is port area calculated by figuring the entire area of the port througout its length, or just the area of the opening? also, during the design process, I may end up increasing the height of the port, giving me even more port area.

2. If possible, I'd like to have the subs firing upwards. However, making the port fire upwards would be completely unpractical, as I'd need one hell of a long port. Would I be likely to experience any cancellation having the subs fire upward, while having the port fire to the rear? anyone ever had any experience with this type of setup?

3. This box will likely weigh well over 100 lbs. My current one is pretty small and I can barely move it around as it is. Might I be better off making two seperate boxes? I take them in and out pretty often.

SSS 18734
09-15-2005, 07:52 PM
ttt

SSS 18734
09-15-2005, 08:36 PM
no one wants to help me out huh

FOSGATE JOE
09-15-2005, 09:08 PM
i take it your box is like 4.5cuft??why not go with a slot port

FOSGATE JOE
09-15-2005, 09:10 PM
never mine just reread your post

SSS 18734
09-15-2005, 09:10 PM
ok I probobally gave way too much info to have anyone interested in helping. so ill sum it up.

1. will a port that is ~3" wide, 10" tall, and 40" long be adequate to avoid port noise?

2. what is the chance of experiencing cancellation by firing the subs upward and the port to the rear in a station wagon?

FOSGATE JOE
09-15-2005, 09:23 PM
i think you need a new design that port is way to long.Go with more cuft for your box then try the port stuff agin

SSS 18734
09-15-2005, 09:31 PM
whats wrong with a long port? and I really cant make too big of a box, the subs are best suited for small boxes. and I dont want a massive peak near tuning.

SSS 18734
09-15-2005, 09:44 PM
if I increase box volume to 2 cu.ft., and raise the tuning to 35hz, I only need a port 27" long.

However, at maximum power the subs will reach full excursion before 30hz, which i'd like to avoid. The other box wont reach full excursion untill around 25.

FOSGATE JOE
09-15-2005, 09:48 PM
man 40inchs is crazy for 1.50cuft thats me thoe maybe go with a round port to cut down on port length?

SSS 18734
09-15-2005, 09:59 PM
how about this, using round ports?

2 cu.ft. :uhoh:
tuned to 35hz
two 4" tube ports, 25" in length.

or two 3.5" wide ports... 19" in length

Think that would have any port noise? i'm getting port noise right now with a single 4" by 6.5" tube port... not all that much though.

FOSGATE JOE
09-15-2005, 10:24 PM
ok how a bout this 4cuft with 5 x 10 x22.55 if i'm right will give you 35hz just make sure you brace!!

SSS 18734
09-15-2005, 10:26 PM
4 cubic feet is way too large. im putting two of these in my trunk, and those subs arent well-suited for large boxes. They reach excursion really quickly.

PowerNaudio
09-15-2005, 10:26 PM
use the rear port air velocity window, when changing port width and length and try to stay as close to the 17m/s or below as you can, since any thing above that speed makes port noise and also keep an eye at the freq that the peak of the curve is on, since that the freq when youre actually going to hear the port noise. if the freq is high then dont worry about it and if its below a freq youre sure youre never going to play on like 25hz or for sure 20hz and below then dont worry about it ether.
also, on the signal tab make sure you put on there the rms power youre going to be giving the particular sub or subs youre designing the box for since that will change how fast the air goes in and out off the port.

FOSGATE JOE
09-15-2005, 10:38 PM
ok well good luck with your box.I to will be building a ported box some time soon .

SSS 18734
09-15-2005, 10:43 PM
use the rear port air velocity window, when changing port width and length and try to stay as close to the 17m/s or below as you can, since any thing above that speed makes port noise and also keep an eye at the freq that the peak of the curve is on, since that the freq when youre actually going to hear the port noise. if the freq is high then dont worry about it and if its below a freq youre sure youre never going to play on like 25hz or for sure 20hz and below then dont worry about it ether.
also, on the signal tab make sure you put on there the rms power youre going to be giving the particular sub or subs youre designing the box for since that will change how fast the air goes in and out off the port.

holy moses that helps a ton. I checked out my plans and the graph was off the chart, at like 170. But I cant seem to keep the air velocity below about 60 with the box that im planning on...

best I came up with was

2.00 cu.ft. airspace
tuned to 35hz
a single 4" wide port, 10" tall, 40" long.

at tuning, I have an air velocity of 58 m/s...but thats about 3x less velocity than my current box... which doesnt have all that much noise and peaked at 190 m/s.

Should I be concerned with the 40" length?

PowerNaudio
09-15-2005, 10:54 PM
port length
the only problem is see with a 40" long port is being able to fit in the box, as long as you have tuned it right and port noise is under control if you can find a way to fit 40", lol , go for it.
you can always have the port out side the box.


at tuning, I have an air velocity of 58 m/s...but that's about 3x less velocity than my current box... which doesn't have all that much noise and peaked at 190 m/s.

check at what frequency is peaking at if its has a peak of 190 @ 90hz or 28hz and you don't usually play at those frequencies then its wont be a problem.

SSS 18734
09-15-2005, 11:20 PM
check at what frequency is peaking at if its has a peak of 190 @ 90hz or 28hz and you don't usually play at those frequencies then its wont be a problem.

maximum air velocity was at its tuning frequency, approx 48hz.

With the new box, the velocity is highest at 32hz, at around 58 m/s.

PowerNaudio
09-15-2005, 11:41 PM
maximum air velocity was at its tuning frequency, approx 48hz.

With the new box, the velocity is highest at 32hz, at around 58 m/s.

190m/s @ 48hz and you say the noise was minimal.

most likely the bass was drowning it from being super noticeable.

on one of my experimental boxes i stuck a 2" port 10" long tuned at 31hz or 32hz box was 1.12cu ft. for a 12" sub pushing it with a 300wrms amp, the port noise would peak at 65.9m/s at 25hz and i could hear port noise from like the 50hz~55hz down, gradually louder till like high 20s where all you could hear was port noise. lol.

i guess the position of the port in relation to driver will play a big factor in, if you hear it or not.

is the sub louder then the port noise and things, but if there is port noise then the port is just too small.

bigbangtheory
09-16-2005, 02:41 AM
Man after reading that I think I will stick to a sealed box for my 3004spls for now. It will be to complicated and to much money for a ported box. Glad I read this.

Spkrman
09-16-2005, 03:31 AM
4 cubic feet is way too large. im putting two of these in my trunk, and those subs arent well-suited for large boxes. They reach excursion really quickly.

actually a larger box will decrease excursion to a point, until you get TOO big.

Whats the breaking point? Gotta build and test :)

winisd means poop, just because it looks like that on paper doesn't mean its going to respond like that! Very littl of what actually effects response is taken into account with ISD.

FOSGATE JOE
09-16-2005, 08:39 PM
so true ^^^^^^^%#!