jmac, can i get a yes or no?

[req 5,000+ posts]

i made a thread a week or so ago trying to figure out what i should tune to. here is what i came up with (way to find my tuning)

the 12 volt's calculator page

my method was this;

1. insert your information into the "Port Length Calculator" to find the diamater and length of your port. (*note- you are not making a round port, this just gets us some numbers to work with.)

2. insert the resulting length and diamater into the "Volume Calculator - Tube/Cylinder Enclosures" to get your net port volume.

3. fiddle with the "Volume Calculator - Rectangular/Square Enclosures" parmaters - lengths\width\height - until your volume closely matched that of the cylander you just made. this will give you the lenth\width\height of your "port box" you now need to make, INCLUDING the thickness of your wood (*note 3\4" mdf = .375 inches) .

*NOTE* this is going to take alot of trial and error. dont forget to try and match the size of the port to the space limitations you have to work with - ie; your trunk. i wanted mine ~3" tall and ~10" long and ~20" deep. so use those as starting numbers, and add decimals and lower or raise the numbers until it is close to your space limitations.

//content.invisioncic.com/y282845/emoticons/patriotic.gif.b47a6e0394a3738334c387bdf79409f4.gif

so jmac;

will this result in a correct port?

my results are as follows;

1.2cuft box

37hz

height = 2.2

width = 10.2

depth = 17

cuft = 0.12886 (the round port calculator came up with 0.12872 cuft for 37hz internal volume of my cylander)

if this works. ill make a tutorial with screenshots so people will get it right.

as for now. im going to bed. its 4:30am. sigh. good night all.

Click to read more...

 

[req 5,000+ posts]

anyone have any comments?

 

[Nikuk 5,000+ posts]

1.2cuft box

37hz

height = 2.2

width = 10.2

depth = 17

cuft = 0.12886 (the round port calculator came up with 0.12872 cuft for 37hz internal volume of my cylander)

that is 12.2 right? these are internal volumes before cub & port?

 

[req 5,000+ posts]

that is 12.2 right? these are internal volumes before cub & port?

yea thats 12.2, sorry =) it was 4:30 and i was tired ... i proof read it a bunch of times to make sure it made sense, but i copied\pasted that part and i suppose i missed the number 1. heh.

well. whats cub & port mean?

and they are external dimensions, or so i believe. the site asked for a wood thickness, and i have 3\4" mdf, so i put in .375... so i think its for external dimensions.

does it sound right however? i have no basis of comparison.

by the way. you are in buffalo? thats cool, im in syracuse right now. well, about 10mins out of the city in the suburbs of liverpool (little north of the city near the carousell mall) you going to college there or somthing? UB, BU? //content.invisioncic.com/y282845/emoticons/wave.gif.002382ce7d7c19757ab945cc69819de1.gif

 

[Nikuk 5,000+ posts]

hmmm okay. i'm at work now using excel (all my fun programs are at home) so this isnt as exact as it could be.

if your box is: 10.2" x 12.2" x 17" internal then the box is 11.7 x 13.7 x 19.5 external w/ .75" mdf.

Based on internal values I get 1.224 cubes.

to tune 1.224 gross to 36.913 hz i get a 3" round port (1/8" thick wall) length of 9.625". This drops the gross vol to 1.182.

Subtract from 1.182 what ever your sub displaces and thats the net vol.

I really dont know if this is even what your asking but i hope it helps. If not, sorry....

Yep, live in Buffalo... working. Got a few friends in and from 'Cuse... friggin Orangmen... //content.invisioncic.com/y282845/emoticons/toast.gif.bc0657bf54b9ee653b6438524461341e.gif

 

[squeak9798 5,000+ posts]

Stupid question (I haven't look at the 12V page, just this thread).....3/4" MDF is .75", why did they have you use .375" (3/8")

 

[Nikuk 5,000+ posts]

Stupid question (I haven't look at the 12V page, just this thread).....3/4" MDF is .75", why did they have you use .375" (3/8")

yah ditto, didnt get that part. unless he's trying to calc a slot port in some wierd friggin way...

 

[req 5,000+ posts]

ok you guys are really confising me.

THE BOX IS FIBERGLASS, im trying to make the PORT.

that was a typo, im sorry, i mean 3\8inch.

is that port (my dimensions above) the correct size for a 1.2cuft box at 37hz. thats exactally what i wanna know. i THINK its correct. but im not sure.

 

[supa_c 5,000+ posts]

not a single post by Jmac.

 

[Nikuk 5,000+ posts]

THE BOX IS FIBERGLASS, im trying to make the PORT. that was a typo, im sorry, i mean 3\8inch.

is that port (my dimensions above) the correct size for a 1.2cuft box at 37hz. thats exactally what i wanna know. i THINK its correct. but im not sure.

2.2", 10.2", & 17"?

2.2" x 10.2" = 22.44 sq in of port. with a depth of 17" in a 1.2 cu ft enclosure yields ~54.33 hz.

1.45" x 9.45" = 13.7 sq in of port. with a depth of 17" in 1.2 cu ft enc = ~41.6 hz.

these are minus you 3/8" walls.

At this point, i have no idea what you're talking about.

//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif I give up.

 

[req 5,000+ posts]

sigh... i have no idea what im doing.

i am making a box that is 1.2cuft that is at 37hz. its going to be fiberglass.

mind filling me in on how you got those numbers njccbflo? or just tell me what will yield 37hz? thanks alot for your help in all this.

 

[Nikuk 5,000+ posts]

sigh... i have no idea what im doing.
i am making a box that is 1.2cuft that is at 37hz. its going to be fiberglass.

mind filling me in on how you got those numbers njccbflo? or just tell me what will yield 37hz? thanks alot for your help in all this.

Frequency=0.159*(((AV*(1.84*10^8))/(Vb*(LV + 0.823*(AV^0.5))))^0.5)

Thats the formula in Excel.

Okay, if your doing the RE SE10 in your sig i would suggest 15 sq in port minimum. But thats gonna be hella tough in a small enclosure.

If you have 1.2 cubes already. Subtract the driver displacement: 0.14 cubes.

Now you have 1.06 cubes. Tune that.

In short i can only come up with around 9sq in of port by ~22" for your enclosure. (1.5x6x 22.13 deep). Of course the port can bend and such but good luck fitting it in that enclosure (sight unseen). It'll leave you with a net volume around 0.78 cu ft. This is what your sub will see.

 

[Nikuk 5,000+ posts]

duh, and in this formula

Frequency=0.159*(((AV*(1.84*10^8))/(Vb*(LV + 0.823*(AV^0.5))))^0.5)

Av = Port Area

Vb = Box Volume ((LxWxH) - sub displacement - port displacement)

Lv = Port Length

I'm sure Jmac or one of the other gods can make this easier for you. I'm not the best teacher LoL

BTW- you can also run the port outside of the box too! That'll save you alot of volume in the box but may not be as pretty. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Fitz 10+ year member]

with the 1.06 cubes, figure out what you'd like for port, then subtract that from the volume and try the formula.. keep goin back and doing it until you get the tuning you want (unless you want to put the port outside the box) it's a jolly fun time, trust me

 

[OLD_SCHOOL 10+ year member]

i don't know if i can help at all other than offer moral support, but i the way i undersantd it is

you want to make a box and only can fit a 1.2 cube box

and now you want to put a port in it to tune it to a freq you choose

the problem however is that when you insert a port you change your internal volume thus chaning the freq is that what you got or am i totaly off

mat