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Having problems with the port calculator and box design


Colton37

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I have an Xv2 15 on the way. I'm trying to figure out a box for my 08 cobalt. I dont have the exact dimensions possible for my vehicle yet but I can post when I get off work. I do know that 15 inches is the tallest I can fit through the trunk from inside the vehicle..(outside into the trunk is smaller) but the actually inside of the trunk is taller than 15. Just the metal lip behind the seats is 15 inches in height. So I could add a few baffles once the box is inside my vehicle closer to 18 or 19 to mount my sub. Or just put it half way together, slide it in then jus put it together the rest of the way inside Unless someone has a better idea.. Anyway when I use the port calculator I'm getting around 90 cu feet port area for an aero port on the calculator but when I go design the box on this website subbox.pro the port area they give me is way lower... like 28 sq ft port area.. please helpScreenshot_20200214-123621_Chrome.thumb.jpg.f87fcff76a283984ae0707a41a579f57.jpg

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triticums calculator is pretty good but it starts to break when you add a lot of power. you just cant get that much port area and keep the port length reasonable. i have also heard from competitors that they have gained on a meter with a slightly smaller than optimal port.

 

winISD is a great program to figure out port air speed if you know how to use it. i would suggest getting it and playing with it for a couple weeks modeling different boxes. Dont get hung up on port noise or "chuffing" too much. you have a trunk build so its going to be a tough road ahead of you if you want to get loud.

 

i have a trunk build too and as weird AL once said, ive been building and testing so long even ezekiel thinks my mind is gone

 

 

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23 minutes ago, strangeduck said:

triticums calculator is pretty good but it starts to break when you add a lot of power. you just cant get that much port area and keep the port length reasonable. i have also heard from competitors that they have gained on a meter with a slightly smaller than optimal port.

 

winISD is a great program to figure out port air speed if you know how to use it. i would suggest getting it and playing with it for a couple weeks modeling different boxes. Dont get hung up on port noise or "chuffing" too much. you have a trunk build so its going to be a tough road ahead of you if you want to get loud.

 

i have a trunk build too and as weird AL once said, ive been building and testing so long even ezekiel thinks my mind is gone

 

 

Haha that's a good one! Aero or slot? Which do you prefer? And louder with the sub facing into cabin? Mounted facing up to trunk? Or sub facing the back of trunk?

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in my trunk i found subs up port back is best. i might gain subs and port forward but you have to put in a ton of work to seal off the entire trunk 100% from the cabin to make it work. and if it doesnt work then that can be frustrating. 

 

keep in mind, my car is horrific to get loud. ive been trying for two years to figure out what works. So if you wanna put in that time and effort you will see gains. i enjoy the process. and dont let losses discourage me. just take in stride and move forward. dont be afraid to screw up and dont be afraid to toss a box in a fire its its bad. 

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10 hours ago, Colton37 said:

I have an Xv2 15 on the way. I'm trying to figure out a box for my 08 cobalt. I dont have the exact dimensions possible for my vehicle yet but I can post when I get off work. I do know that 15 inches is the tallest I can fit through the trunk from inside the vehicle..(outside into the trunk is smaller) but the actually inside of the trunk is taller than 15. Just the metal lip behind the seats is 15 inches in height. So I could add a few baffles once the box is inside my vehicle closer to 18 or 19 to mount my sub. Or just put it half way together, slide it in then jus put it together the rest of the way inside Unless someone has a better idea.. Anyway when I use the port calculator I'm getting around 90 cu feet port area for an aero port on the calculator but when I go design the box on this website subbox.pro

 

5 hours ago, bmwking said:

triticums

My .02... to me Triticums calc seems to be based on clamped power 1st off. A 5K amp on 2-12's... Figure rise and 81in2 of port (not 81ft3) for example should suffice in a 4.5ft3net /w/ 23-25mm excursion 1200w subs clamping 3K. Don't think if you got a 5K amp that automatically you'll see 5K.

Voltage, impedance rise, thermal losses and other factors all determine your actual power I've heard... Just keep your velocities around 80-110fps when taxing your sub with a slot port and 120-130fps if possible with an aeroport (flared... not just a round). Volume/tuning affects velocities as well so watch excursion on estimated power while sizing the port. And watch how filters can affect everything along the way... my .02... 😉

Either way... Model those subs on your power. Calcs are fine but not super accurate.

 

OP... a single 15" sub/6" aero?.... I'd sacrifice a touch of volume 1st before doing any other compromises, less volume means less port velocities usually and add filters and you'll probably be fine... model it up... lose a bit of depth and I'll bet that height you're working with will slide in there.

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On 2/15/2020 at 12:34 PM, Oldmang said:

A 6" aero would be better for a 12. I think an 8" or dual 6's would work well for that X.

It IS a hi-excursion 1500w underrated sub after all.

Well I tried to use a port calculator. If I use an 8 inch the length would have to put way longer than "big ass ports" make theirs. They only make them 21"   but if I do a 6 inch tuned to 30 hz I can do it because their ports come apart. I've actually had many people say 8 in but it just wont work according to the calculators. Maybe If I wanted to tune higher than 30 hz a 8 inch port would work...

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