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Discussion Starter #1
so i have 2 t2d4 12" im needing to build a box for next summer.
the dimensions i have so far is 2 boxes 19.5" wide 18.5" deep and 19" high it will have a slot port 2" wide and the back wall of the port will be 10"
gives a chamber size of 15.25" wide 14.75" deep and 17" high with a volume of 2.21ft subs say they take .151 so with the sub in i would have 2.06cu ft of aispace. now if im right that would tune the box at about 33hrz right? im not sure on this and any help would be great i want the box tune to 33-35hrz last box i did was tuned to 44hrz and just wasnt deep enough.

the subs need 2.00cuft of airspace they are rockford dual vioce coil 4ohm 12"
thay do 1000rms 2000peak and i am using a t1500.1bd cp that does 1890 at 1ohm rms.

thanks in advance
 

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WinIsd. Download it
 

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Discussion Starter #3
not my computer and they dont want me downloading anything to it.

i am looking for help/advice on this if your not doing either or debating with others please do not post
 

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so i have 2 t2d4 12" im needing to build a box for next summer.
the dimensions i have so far is 2 boxes 19.5" wide 18.5" deep and 19" high it will have a slot port 2" wide and the back wall of the port will be 10"
gives a chamber size of 15.25" wide 14.75" deep and 17" high with a volume of 2.21ft subs say they take .151 so with the sub in i would have 2.06cu ft of aispace. now if im right that would tune the box at about 33hrz right? im not sure on this and any help would be great i want the box tune to 33-35hrz last box i did was tuned to 44hrz and just wasnt deep enough.

the subs need 2.00cuft of airspace they are rockford dual vioce coil 4ohm 12"
thay do 1000rms 2000peak and i am using a t1500.1bd cp that does 1890 at 1ohm rms.

thanks in advance
With the 15.25" wide, 14.75" deep, and 17" high and using 3/4" wood, that would put the chamber at 1.63cubic feet before displacement of the sub. So around 1.48cubic feet after displacement. Do you mean the port will be 10" high, or 10" in length? If you mean 10" high for the port and 2" wide, to get 33Hz at the 1.48cubic feet internal volume the port length would have to be 29.75" in length.

Your dimensions of 19.5" wide 18.5" deep and 19" high and using 3/4" wood would give you slightly over 3 cubic feet(3.01) before the port/displacement, or 2.86 after displacement. With that, your port at 10" high and 2" wide would have to be 13.61" in length to get the 33Hz tuning.

Hopefully I read your post right. If I didn't then just let me know.
 

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Discussion Starter #5
With the 15.25" wide, 14.75" deep, and 17" high and using 3/4" wood, that would put the chamber at 1.63cubic feet before displacement of the sub. So around 1.48cubic feet after displacement. Do you mean the port will be 10" high, or 10" in length? If you mean 10" high for the port and 2" wide, to get 33Hz at the 1.48cubic feet internal volume the port length would have to be 29.75" in length.

Your dimensions of 19.5" wide 18.5" deep and 19" high and using 3/4" wood would give you slightly over 3 cubic feet(3.01) before the port/displacement, or 2.86 after displacement. With that, your port at 10" high and 2" wide would have to be 13.61" in length to get the 33Hz tuning.

Hopefully I read your post right. If I didn't then just let me know.
the port will be 10" in lenght and 19" high subtract wood thickness of course. i did use the re audio box builder and it said it would actualy come out to 2.49cu ft tuned to 33.17hrz. the 19.5w x 19h x 18.5 is the outside of the box the port will be 2" wide 15" deep and will go along the back side of the box for 10" the height will be 17.75 if that helps clear any of it up. the inside of the box will be 18 wide 17 deep and 17.5 high giving it 3.09cuft the port will be taking up .52 giving it 2.57 and the sub takes .15 that drops it down to 2.42 then the walls for the port will be taking .19 putting it at 2.23 for the sub.
this would be easier if i had a sketch of what im talking about ill see if i can make one later.
 

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In my experience, the RE Audio Ported Box Calculator has been predictably close enough to use for normal listening. I have designed and built a number of enclosures using this program in combination with Bass Box Pro, and WinISD, and it has produced equally consistent results. To be quite honest with you, it will probably be very difficult to tell any difference if you are a tenth of a cube off when it comes out. Also be aware that tuning frequency of the port has little to do with in car tuning frequency. With the boxes I have built for my Focus 32-35Hz seems to do very well in terms of the compromises between output and low frequency extension. I guess what I what you to take from this is that your measurements look fine and will be plenty close enough. The car and box construction will have a greater impact on performance than any further design revisions at this point. Testing is the only way to really tell how it will do in your car. Go build it! Oh, and post pics when you do!
 

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Discussion Starter #7
In my experience, the RE Audio Ported Box Calculator has been predictably close enough to use for normal listening. I have designed and built a number of enclosures using this program in combination with Bass Box Pro, and WinISD, and it has produced equally consistent results. To be quite honest with you, it will probably be very difficult to tell any difference if you are a tenth of a cube off when it comes out. Also be aware that tuning frequency of the port has little to do with in car tuning frequency. With the boxes I have built for my Focus 32-35Hz seems to do very well in terms of the compromises between output and low frequency extension. I guess what I what you to take from this is that your measurements look fine and will be plenty close enough. The car and box construction will have a greater impact on performance than any further design revisions at this point. Testing is the only way to really tell how it will do in your car. Go build it! Oh, and post pics when you do!
i will actually be taking about.25" from the length need to make sure it will slide into the hatch, i will be making 2 of them 1 for each t2d412". will be making it sometime within the first week of july. gotta buy my mid range amp and then there is christmas and birthdays so my money is booked. none the less its only getting up to about 35 degrees up here. my work place is outside so that wont be working for now.
i will get picks of the subs in the box there in for now. just need to find the time. putting svt springs on the car today. [clap][clap] will actualy be my very first car with improved suspension in anyway at all.
 

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Ah, it makes sense with you being in Alaska now. I was wondering why you were making plans for a box you won't be building for almost a year. Why build 2 boxes instead of having them share the space? You could probably make up the volume difference by combining them into one chamber without using as much wood.
 

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Oh and for the suspension, good luck with the install! Definitely worth it for the difference it will make on driving the car. Upgrading the roll bars also make a huge difference in the balance of the car. The Eibach setup completely neutralized the under steer in the stock setup.
 

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Discussion Starter #10
well, didnt get to put the svt springs on today. was gonna do it at the shop my dad works at but they ended up taking a job do tires/brakes on some trunks for a local company so they dont have the open bay today. I plan on using 2 boxes instead of 1 so that the boxes will be stronger and flex less without using as much. also i will be needing to be able to take them out for the spare tire and jack. these subs are no joke on weight add in the box and you have got a monster of a system. subs way in at almost 60lbs a peice plus the box its a good 150-175lbs. id rather be able to just slide 1 out the way at a time if i get stuck with a flat in the dead of the winter.
 

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im getting some humming from subs to though. i think its my deck, i dont think the stock ground is good enough. gonna have to upgrade it. checked all the other ground and they are all good, i do still need to do the big 3 though. for that it will take a garage/warmer weather for.
 

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I've seen a lot of people just do a false floor, only raising it slightly, and mount some sliding hinges or whatever they are called (like sliding doors have) to the floor. A lot of people with hatchbacks seem to do that since it's so simple to do and makes it easy to access your spare tire, while not having to ever lift anything. Just get some that can lock and you just have to lay down your back seats for it to work. Or maybe they take the back seats out, not for sure lol. Either way it'd be worth looking into.

And for the box if you make one then you can just add bracing so it won't flex. They are always good to add no matter the size of the box. Just pick up a couple peices of the 2x2 sticks/rods of wood and cut to whatever size you need. Also do a double baffle at least with those since they are on the heavy side. If you're worried about changing the tuning of the box with the inside volume changing because of them, just take off the volume of the braces you add and recalculate it.
 

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Discussion Starter #13
yeah i know about all that but the focus might be getting sold here in about a year, so the boxes will also need to be smaller so that i can find a way to fit them in the replacement car. not sure what it might be so i want to keep the boxes smaller so that i wouldnt have to build more. with smaller boxes it will flex less and if there is enough room once the boxes are in the car for the test fitment i was gonna pull them out then add a second board to all possible sides. my hatch floor is raised by 1.5" already aswell i have 2 sheets of .75mdf to seperate from the floor better.

oh and im doing a 2" slot port because it calls for the back wall of the port to be longer for it to be within the range of 33-36 hrz while also adding support to the box.
 

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I was just mentioning that just in case you decide to do a single box or something. And just curious why your selling the fofo?
 

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Just from the measurements the OP has put up, it looks like his design has a port 19"x2", giving him 38 sq inches. Plenty for 2 cubes of box volume. If anythin, it might be a little too much. I also shoot for around 16 sq inches of port per cube of box volume, and it has served me pretty well.
 

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Gazooks had a good idea there for spare access with all that weight. Even with separate boxes, they will be 90- 100 lbs apiece. You could do a false floor with a long piano hinge at the rear and the box bolted to the floor, allowing you to just rock the whole thing back instead of having to lift it completely out of the car.
 

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Discussion Starter #19
well, my origanal plan was a single box with it sliding out of the way but i am not keeping the focus much longer. we have decided to either move to cali or to michigan and i would rather not drive seeing how it would take a whole lot longer. so the 2 boxes will be smaller and less issues shipping, easier to move incase i get stuck somewhere with a flat for some reason or another, little bit stronger to prevent flexing and will allow me to sell the fofo and put atleast 1 of them in the pontaic we have. keeping the pontaic up intell we move she might want to just ship it ( i wanna sell it lol ). might and might not buy another focus who knows. what i will be getting for sure when i move is a nissan 240sx somwhere between a 92-94. hatchback/fastback wichever you call it, ka24de turbo at about 14psi 300whp. working on the parts list for that. anyways back to the topic at hand, according to the re audio calc. its saying a box 19x18x18 is 2.19cuft and tuned to 34hrz so after subs it will be 2.04cuft so i guess thats the size box i will be going with. gonna hopefully measure this out in my trunk and if i can manage it all sides with space will be doubled wall making it .75" longer taller and wider ( 19.75x19.75x18.75 ) but the inside dimension will stay the same since i will add the extra mdf to the outside of the box
 

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I can see where the dual box approach might make sense for size if you plan to move it to a new car. However, something to think about if you aren't going to be building the box(es) until next summer anyway: consider the acoustics of the car it will be going into next. The same port tuning can sound very different when in different cars, so you may want to build the box more for the next car it will be in, considering the new box will only be in your focus for a couple months or so.
 
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