ported clamshell help/build

[irpirate]

ok so i've been talking to 2000LaDe and he was nice enough to sketchup a 4th order for me

if the tweaking doesn't help enough this will probably be what i'll be doing.

[Colin - STAPUFT]

Kahblam! That is more or less what I was talking about in my post just a few back. From the vid, it looks like you have the space in front of you box. You could keep the part you already have and just build the front chamber. You could leave the clam ported (6th order) or seal it off (4th order). Also it would allow you to build the front chamber right up to your B Pillar where it would be better to seal it than on the glass.

[irpirate]

the reason im hesitant about tweaking the box so much is that for some reason i have it stuck in my head this box is effed and my design was crappy. (adding on another section to the front). in case doing a bit of tweaking and hoping for a miracle doesn't work, id honestly rather just build another box.

the box 2000LaDe drew up for a me would be 7.5 inches longer than what i have, would pretty much go all the way to the front seat (thanks for mentioning sealing at the b-pillar opposed to glass, didnt even think about that), and actually has some math/number/thought into the design. if my current box design is truly fucked, im just gonna use this current box as a table/scrap for building the 4th order.

im waiting for my friend to get back to me, need his garage and help moving the box so i start tweaking. ill see how removing the port extensions go today.

[irpirate]

didn't get a chance to do anything today. finals are coming up soon, group project deadlines as well. thing's are most likely going to go slow until the semesters over. i'll post updates when i have something worth posting

[irpirate]

so the more i listen to it the less i'm liking the sound. something about it just isn't right. i met some people today and got to hear someone else's subs for the first time in a while and it just further deepens my dislike for my clam. still haven't had a chance to work on it but i'm fairly sure i'm going to be building a 4th order.

2000LaDe was super nice and helped design and sketchup a 4th order for me at 3 or 4 am. the picture he posted above is the design

here are the numbers:

outer dimensions 59.5 depth. 33 height. 37.5 width

16 subs total.

qts - .46

Vas - 2.83 ft^3

Fs - 25

the sealed area will be 7.93871 per 8 subs. so Vr - 15.87742 cubic feet

ported area. Vf - 17.88276 cubic feet.

ported area tuning. Fb - 45. port will be 19.5x19.5. 3 inches deep. decided on a square port instead of the rectangular one.

I think he said that a 2:1 ported ratio is good but that's just not possible for me to do and that this design should work.

Not that i don't trust him or his designing abilities, but could someone please double check the numbers of the design? (he gave me the go ahead for second opinions). after this whole clam ordeal, i'd rather not be building too many boxes of this size.

I read an older thread on 4th orders, someone was planning for 16 12s as well and this was what he said about the design

1.25c sealed chamber

1cf ported chamber

25sqin of port

16.75" long

Just multiply that for the amount of subs.

So in this case it was:

20 cubes sealed

16cubes ported

400 sq in of port

16.75" long

which goes against what 2000LaDe said.

i'm still going to be messing with the clam a bit when i have the chance.

all help and input is greatly appreciated!!!

[irpirate]

dled winisd. modeling the box. anyone know how reliable this program is for 4th orders?

*edit - nvm, i effed up one of the t/s parameters cuz the unit. changing and ill re-edit.

*edit 2 - ok apparently i didnt mess anything up.

i modeled it to 2000LaDe's design. only discrepancy is the port length. winisd says it for a 19.5x19.5 port tuned to 45 the port needs to be 13.5 inches long. the gain graph goes something like this. peaks at 35-37. db gain from 30-31 up to around 57-58. i listen to almost all hiphop/rap/r&b. need looowwwwwsssss. this is for my daily/only driver. no interest in metering high or burping. going for groundpounderrrrr!!! so maybe tune lower? dont remember the term but the -3 db drop is at 27ish and 67 ish

anyone wanna help me figure out wtf im doing? lol =D

[irpirate]

winisd 45hz tuning

*edit

winisd 42hz tuning

sooo now i don't know what to do to figure this out myself lol. i'll continue my stupid amounts of googling/research/reading and see if i can understand these things better.

[audiofanaticz]

I kind of feel you where on track adding the port extensions that go off your top and bottom baffle (in the purple of your image) to achieve your lower tuning you desired, however I think you missed a very important step.

As it sits right now, you have the pieces acting as an extension of your port, however there is nothing guiding the air waves from the top champer out the clam, and the same from the bottom chamber out the clam.

The air pressure from the top and bottom chambers are meeting someplace in the middle and are just clashing with each other and creating a lot of cancellation. Im sure some air from the top is being forced to the bottom chamber and vice versa, and the opening of the clam between the chambers is just acting as a relief valve, but no where as it should.

yellow would be the moving air.

red would be where the waves are meeting and canceling each other out.

blue would be the minimum air pressure coming out of the port.

What you would of need to done to make this work somewhat properly is put a divider between the 2 (like a triangle)to direct the pressure out of the clam, and not into the adjacent chamber like so.

Same colors above represent the same things, green is just the divider (or triangle).

You would do the same thing whenever you end up building a common chamber box with a center port like this.

Also sealing the clam off from the rest of the vehicle will help tons!!!!!

Edit for link failage!

[irpirate]

i actually had asked about that in the beginning of the thread but this was posted

View Postirpirate, on 12 November 2010 - 07:00 PM, said:

another question, will i need to put something in the middle of the port against the back wall to angle and separate where the ports for the two chamber come together?

You could... I saw a write up once on someone who tested this with this type of "loaded" enclosure. They did it with nothing between, a small "v", and a larger "v" (presumably to help air flow). It was the loudest with nothing in there. Bigger the "v", the lower the SPL. I know that was his box and not yours- just saying. I would do it if it makes you happy- I intended to make one for mine and did not. I haven't noticed it as not being there.

yay ghetto quoting!

ima dumbass and forgot to 45 the corners. ill see what i can do in terms of adding the middle thing. i dont think i can pull the box apart at all. everything's attached pretty well. ill just have to hope i can crawl/reach in enough to be able to put a triangle thinger in. if not i may have to do just a straight board. then after that maybe pulling the port extensions off depending on how well that works.

honestly the box sounds kind of bad after listening to it for a while. the bass just sounds unnatural and boomy. it has no rumble to it and just sort of sloppily cuts off. does this mean that its too small? thats what my guess would be at least.

[shaggy]

Is each port half the size of the center opening? If it isn't that is your problem. This is why i asked if you have tested to see what the box is really tuned at. Get a cd with test tones on it. Start at 60hz and go down untill you see the sub almost stop moving and that will be your tuning.