Ok so i did this write up for a guy on youtube that had asked how i design boxes. this box is for a sub up port back, and its for an url=http://www.audioque.com/aq/HDCSeries.htm]AQ 15" 15" subwoofer so i told him as follows:

"if your doing a box that is 5 cubes you take 16 x 5 which equals your port area. then you figure out how tall you want it to be. then you figure out the port height. i would say your going to want the box to be 17" tall then you minus the double baffle and the bottom plate. so 17-2.25 which equals 14.75 then you divide that by your port area. so (16 x 5)/14.75= 5.423728 so lets say your port will be 5.5 by 14.75. (this is for a sub up port back driver side box) then you type that into this calculator
http://www.carstereo.com/help/Articles.cfm?id=31
(bottom half)
so you type in 5 cubes square port, what you want your tuning to be say like 35 hz, make sure to check the slot port yes thing. then it gives you the number.

so your port will be 14.75 tall by 5.5" wide by 25.5 long. ok you have your tuning done.

now you just add your total port displacment with your sub displacment and then add the interior volume you want.

so... 5+.15(sub displacement)+ [(14.75x6.25x25.5)/1728)]=6.50 cubes total interior. (rounded)

you do the 6.25 wide because you need to incorperate the piece of wood that runs along side of it.

so you then take your 6.5 x 1728 (1ft^3=1728^3in) and you get 11232

then divide by 14.75 because thats how tall your box will be on the inside,

so you get 761.5 ish then you just decide how wide you want it or how deep you want it. dont forget this is internal volume. you need to accommodat the .75 wall thickness on each side of the box to fit where you want it to fit. so if you want the box to be 42 total outside then you minus 1.5 from that and then divide by that number.

so say thats what you want the box to be width wise, divide 761.49/40.5=18.8

so your total interior dims are 14.75 tall by 40.5 wide by 18.8 deep.

check all your math and times them numbers together and see how you came out. so 14.75x40.5x18.8=11230.65 then divide by 1728 and you get 6.4992187

very close to what you wanted! this is a good thing!

now if you think you need bracing just go and get some 1"dia round wooden dowels and put one or two in there. also put corner pieces in the corners. dont need it but it helps. yes these do remove some volume. but not enough to change the tuning too much.

now you build and enjoy the sweet sweet sound and poundage!"

i figured since i had it i would post it here since im always seeing a "how do i design my box" topics on this forum. is it perfect, no probly not. but it give you some of the thought behind the process of designing a box this is for one application, there is different ways to get the box tuned and designed properly.

If you have anything to add or want to just call me an idiot then please do.

Thanks for your Time,

Anton Miller

PS: Sorry if this is a repeat post, i searched but didnt find anything



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Too much port area.

lol its in your rule. and the website says that to use 16 sq in per cu ft and stay within 10% of that. oh well cant please everyone.

from your experience do you have anything to add?





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I sure do. I just like telling you that you have too much port area.

Anton Anton Anton...
What do you know about impedence rise? Or standing waves inside a box? Positioning of the box? Port parallel or perpendicular to the sub plane? Let's say I wanted 60 square inches of port. What would happen with that? What about 100? What if I wanted my box to be 3 cubes? 6 cubes? What differences would that make to anything? Slot or round port? Why wouldn't I tune it to 38 like Audioque says to?

he wanted the 35 hz tune and he said do it at like 5 cubes. plus this wasnt a design per say as it was a tutorial to teach him how to do it. he certainly can use this as a design because it will sound great. no port noise and it will pound like a bastard. alot better than the box he has now.

OK:

Impedence rise, i have no clue please explain

i do know that standing waves in a box causes less spl if thats what your wondering. but i addressed the waves by telling him to put the corner pieces in the box at every corner. i may not have said why but maybe i should have. i cant find it but from adding corner pieces in a subwoofer box a guy gained .8 db's and he put some tubing around the cornes of the OUTSIDE of his box and it gained him a little as well. however looking like crap. it just shoxs that if oyu have good fluent air flow through the ports and into the cabin you will always be louder.

positioning of the box depends on the car. in my car i like to keep if about 6 inches form the trunk lid. that way when the subwoofer is in phase with the car, (not sure if i phrased that right but w/e). it makes the wave nice and smooth throughout the car. but i dont know about other cars.

60 would result in port turbulance and port noise. however it could gain in the right application because it does create more velocity. but like i stated earlier its bad to have a turbulance effect. you always want nice flowing port. 100 is quite a bit of port but you wont have any port noise. just look at most of the spl vehicals out there, there ports are gigantic. im assuming its for good flow of the air form the port. but idk. i dont compete so idk what they make them so big for. also i dont see a problem with having a big port as long as you make it longenough to make the tuning you want. i owuldnt however suggest making a port with a total port displacement bigger than the box's internal volume just because it would most likely cause your sub to become free aired.

the smaller the box the better responce the bigger the box the better the lows.

slot or round no difference at all. the only difference is the placment of the round port should be atleast 1-2 diameters away from the walls of the box. what about a square port? same thing its just a way to tune oyur box. a ported enclosure is a ported enclosure.





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Bigger enclosures have less impedance rise, smaller have more. Impedence rise means that there's a big ol rise of impedence usually at your tuning frequency, and it drops below that.

Lanman31337 - Cavfire wrote:Bigger enclosures have less impedance rise, smaller have more. Impedence rise means that there's a big ol rise of impedence usually at your tuning frequency, and it drops below that.

elaborate alittle more. from what ive read in other forums on this topic it doesnt seem like a big deal and you really cant stop it unless you get a requlator of some sort.





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http://www.caraudiobook.com/

found this great website has alot of good information and diagrams!





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Lanman31337 - Cavfire wrote:Bigger enclosures have less impedance rise, smaller have more. Impedence rise means that there's a big ol rise of impedence usually at your tuning frequency, and it drops below that.

So basically your power out put drops at your tuning frequency and then increases above and below it?

Yes and no. It'll fluxuate in between frequencies. 30 hertz might be 3 ohm, 35 hertz might be 6 ohm, 40 hertz might be 12 ohm, 45 hertz might be 3 ohm, etc...