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pj_chevy03
06-27-2004, 12:31 AM
i am going to make a box for 2 sony 10's. the airspace for both subs is going to be 2.46 before sub and port discplacement. anybody with a box tuning prog. plz see what size ports and length of the ports and number of ports i would need to tune the box to 32 hz. much thanx in advance

DBfan187
06-27-2004, 12:35 AM
got the max deminsions?

T/S parameters would help too!

pj_chevy03
06-27-2004, 01:33 AM
got the max deminsions?

T/S parameters would help too!

here's box dimensions (external)

height.....................14"
length.....................56"
top depth...............5 3/4"
bottom depth..........8 1/4"
correction on airspace as well.......its 2.16....sorry

T/S parameters
impedance..............4 ohms
d(mm)....................217
d(inch)....................8.5
Rdc(ohm sign).........2.4
Fs(Hz).....................29.7
Qts........................0.45
Qes.........................0.48
Qms........................6.62
Vas(Lit.).................36.6
Vas(Cu.ft)................1.29
Mms(g).....................149.2
Lvc(mH)......................0.9
Xmax(mm)..................7.9
Xmax(inch)................0.3
BL(Tm).......................11.8

whewwwww....hope my comp dont freeze up :(

DBfan187
06-27-2004, 02:31 AM
WHOA! Is this a truck box? If it is, could you draw out the box for me?

pj_chevy03
06-27-2004, 03:26 PM
i'll have pics of the box design tonite but i'm not real sure why u need a picture of the box design

pj_chevy03
06-27-2004, 08:23 PM
alright jus click on my gallery and it is the first pic.......and the top number is a lil blurry but it is........5 3/4
is that ALL u need to know cuz i'm kinda needin to know soon???????

DBfan187
06-27-2004, 08:52 PM
Make your port at the top of the box going straight down. 4" x 2" slot port for 32Hz.


edit* 7.62" long

pj_chevy03
06-27-2004, 09:19 PM
Make your port at the top of the box going straight down. 4" x 2" slot port for 32Hz.


edit* 7.62" long

whoa whoa.......what happened to pvc.....but i kinda like your idea better really. are you ABSOLUTLEY sure on those measurements cuz i do not want to make another box.
few questions as well
1. put port in middle of box?
2. include the 3/4" of thickness of wood at top of box in port length?
3. most slot ports i see are huge, why are these so small? is it because of the small size of the box?
4. why is the port length so short?
thanx

pj_chevy03
06-28-2004, 05:21 PM
any1 know the above questions????

packerfan
06-29-2004, 05:40 PM
Make your port at the top of the box going straight down. 4" x 2" slot port for 32Hz.


edit* 7.62" long

Dont do that, use 4" dia PVC pipe, make it 14" long for at tune of 32hz.

pj_chevy03
06-29-2004, 06:24 PM
now i'm confused........someone who knows what the hell they are doinn clear this up

DBfan187
06-29-2004, 08:23 PM
Dont do that, use 4" dia PVC pipe, make it 14" long for at tune of 32hz.
WinISD says your way is tuned to 30.76Hz.

Mine is tuned to 32Hz.

pj_chevy03
06-29-2004, 11:15 PM
so either way i go it will be tuned in the neighborhood of 30-33 hz
any1 wanna back db up cuz i want to make sure this is tuned rite

Trixter
06-30-2004, 01:58 PM
I get a box volume of 2.17cu'

For a 4" round port 12.3" long is 32Hz and for a 4" x 2" slot port 3.76" will produce 32Hz.

Use this very simple formula:

LV: vent length
R: radius of vent (Note: for a square vent R will be the sq.rt of A/Pi)
FB: tuning freq.
VB: box volume in cu"

4" round port:

LV = [(1.463 x 10^7 x R^2) / (FB^2 x VB)] - 1.463R

12.3 = [(58520000) / (3839754.24)] - 2.926

4" x 2" slot port:

LV = [(1.463 x 10^7 x 1.6) / (FB^2 x VB)] - (1.463 x 1.6)

3.76 = [(23408000) / (3839754.24)] - 2.3408

DBfan187
06-30-2004, 08:29 PM
I get a box volume of 2.17cu'

For a 4" round port 12.3" long is 32Hz and for a 4" x 2" slot port 3.76" will produce 32Hz.

Use this very simple formula:

LV: vent length
R: radius of vent (Note: for a square vent R will be the sq.rt of A/Pi)
FB: tuning freq.
VB: box volume in cu"

4" round port:

LV = [(1.463 x 10^7 x R^2) / (FB^2 x VB)] - 1.463R

12.3 = [(58520000) / (3839754.24)] - 2.926

4" x 2" slot port:

LV = [(1.463 x 10^7 x 1.6) / (FB^2 x VB)] - (1.463 x 1.6)

3.76 = [(23408000) / (3839754.24)] - 2.3408
Eh, nobody's perfect!:D

pj_chevy03
07-01-2004, 12:52 AM
so is trixter right.....
cuz there is a big *** difference between 3.76 and 7.62
and by the above comment db i'm geussin u agree with him

DBfan187
07-01-2004, 12:59 AM
so is trixter right.....
cuz there is a big *** difference between 3.76 and 7.62
and by the above comment db i'm geussin u agree with himWell, Trixter is the mathematician, he's got the math skillz so.......

I just posted what WinISD said, but both Trix and I don't like WinISD - but most people say it's accurate, so... Pick one! It's your box.

pj_chevy03
07-01-2004, 01:14 AM
well i have heard bad things about winisd so i'm gonna go with trixter......but why is the port so small.....it jus seems so small to everything else i have see.....is it because the 2" x 4" takes up more space than diamter wise than 4 " pvc

DBfan187
07-01-2004, 01:42 AM
yes, it also could be a fact that your box is so small...

pj_chevy03
07-01-2004, 02:04 AM
true dat....

Trixter
07-01-2004, 11:50 AM
I use different formulas to find different aspects of building boxes. There are so many calculators and they all produce different numbers. I figure this way is the most accurate. It make take a few minutes longer, but it's worth the piece of mind.

Your 4" round port has more port area than a 2" x 4" slot port. The more port area you have, the longer you need to make the port to provide the same amonut of wind resistance. The amount of wind resistance is what tunes the box.

Take a small coffee straw about 1" and blow through it. No take a big McDonalds straw about 1" long and blow through it; it's a lot easier. Now how long do you have to make the larger straw to be as hard to blow through as the coffee straw? Same thing here.

Trixter
07-01-2004, 11:51 AM
Dam double post!?!?!

pj_chevy03
07-01-2004, 05:00 PM
so why would u not jus use like a 1" diameter port and thenu would have a real short port?????or are there disadvantages to them being too small....i am very new to learning about tuning boxes.....

Trixter
07-01-2004, 06:33 PM
If the port is too small you will get port distortion. Almost like a whistle. You want a port big enough so that the air moves freely. Yet you want it small enough to still provide enough back pressure so the sub doesn't reach over excursion. I have heard people say that a good rule to fallow is to have a much port area as you have cone area. I don't believe that either. There's no way a single 10" sub should have a port of 78sq", unless it's in a really large box for comp. only, even then that's a lot. There is a formula to figure out min. port area but it kinda complex. If you really want it I could post it.

pj_chevy03
07-01-2004, 11:36 PM
o.k. i think i'm ready to build my first ported box....but first i gotta get the mdf and that means about 50 miles (no hardware stores around here carry it so off to lowes). i'll post pics when its done. could be about 2 weeks though

4DMAN00
07-02-2004, 10:11 AM
I get a box volume of 2.17cu'

For a 4" round port 12.3" long is 32Hz and for a 4" x 2" slot port 3.76" will produce 32Hz.

Use this very simple formula:

LV: vent length
R: radius of vent (Note: for a square vent R will be the sq.rt of A/Pi)
FB: tuning freq.
VB: box volume in cu"

4" round port:

LV = [(1.463 x 10^7 x R^2) / (FB^2 x VB)] - 1.463R

12.3 = [(58520000) / (3839754.24)] - 2.926

4" x 2" slot port:

LV = [(1.463 x 10^7 x 1.6) / (FB^2 x VB)] - (1.463 x 1.6)

3.76 = [(23408000) / (3839754.24)] - 2.3408


Have a question on this equation, for a square port why isn't the R squared? R = 1.6 and not R = 2.56. Because in my enclosure that make a big difference in port length about 20 inch difference.

Trixter
07-02-2004, 11:35 AM
Have a question on this equation, for a square port why isn't the R squared? R = 1.6 and not R = 2.56. Because in my enclosure that make a big difference in port length about 20 inch difference.

You are correct. The equation should read:

7.5 = (37452800 / 3839754.24) - 2.3408

Good catch. That makes a litte more sence now. I'm on pain killers for a pinched nerve in my back so my thinkin' isn't 100% there. That's why I like to show all my math so it can be checked.

Also remember to subtract 1/2 in the slot port's width if you using the wall of the box as a common wall. Here the port length would really turn out to be 6.5"...if the box wall was used.

pj_chevy03
07-02-2004, 03:21 PM
whoa so my port is supposed to be 6.5 in.... which length is it......and what do u mean by a common wall......i need a FINAL prt length....o.k wait is this correct??? common wall means u only use 3 other pieces of wood and use the back wall of the box as the forth wall of the port and in that case the port length would be 6.5......if i did not use the back wall as a wall of the port (and use 4 pieces of seperate wood for the port) then the length would be 7.5.....am i understanding this correct??????? so 6.5" port length with the box wall as a sie of the port???

Trixter
07-02-2004, 03:31 PM
Yes. More often than not a slot port uses one of the outter walls of the box. In this case you need to subtract 1/2 of the ports width from it's length. If you were to simply put in a square port who's four side were its own, and not shared by the box, then you would not need to do this.

In your case, your port needs to be 7.5" long. If you use the side of the box as a side of the port then it would be 6.5" long.

I'll see if I can find something about it....

pj_chevy03
07-03-2004, 12:55 AM
hey trixter could u help me on my thread "help me tune again" as well...thanx

pj_chevy03
07-05-2004, 01:25 AM
so 6.5" is the final answer?????

Trixter
07-05-2004, 11:02 AM
so 6.5" is the final answer?????

That's my final answer.