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IgnoreMe
11-14-2004, 02:17 PM
ok well im tryin to design a box for 2 15" sx's. its gonna be 7ft^3 @ 35 hz.
port is 17.5*6=105" sqr
17.5" high
39" wide
21" deep

pLV=21.5

21.5-11.5(any number like in my tutorial)=10 so 10" is the imaginary length of the 2nd wall

10*6.75*17.5/1728= .6835ft^3 (displacement of 2nd wall)

10-6=4 (so 1st wall imaginary length is 4")

4*6.75*17.5/1728=.2734ft^3 (displacement of 1st wall)

.6835+.2734+.36+7=8.3ft^3 (gross volume)

8.3*1728/(17.5*39)=21 (internal depth)

21-6= 15 (true 1st wall length)

now HERE is the kicker

21.5(plv)-22.5(interal depth+1.5)= -1

hmmm how do i get a wall length of -1 and how do i fix it? i checked over my math and REDID it about 3 times and come up with the same answer each time. any sugestions? if not i got a back up box @ 32hz so its all good but im still clueless as to why i get a negative number for the 2nd wall length

swimfreak26
11-14-2004, 09:40 PM
I do the calculations and get (assuming those are internal dimensions because you said port height was 17.5) 6.1 ft^3 after .2 ft displacement for each driver, and port displacement. I also get a 26" port to tune the box 35Hz.

IgnoreMe
11-15-2004, 01:48 AM
i just dont understand why i get that negative number. oh well i guess ill just tune to 32 hz.

swimfreak26
11-15-2004, 03:05 PM
Lol, 32Hz will sound great...I don't know why you got a negative number though either :waycrazy:

IgnoreMe
11-15-2004, 04:20 PM
yea im sure 32 will sound great its just that i wanted a higher tuning cause with 2000 watts and a 7 cubed box at 32 i go over xmax with about 24mm total while with 35hz i go to about 20.7mm. i bought the viper thinking i would be able to give the sx's more power without riskin them failin mechanically, and of course this is using winISD which is a program and it cant account for real world testing but it does give one an idea of how subs will react.

IgnoreMe
11-16-2004, 04:55 PM
21.5-11.5(any number like in my tutorial)=10 so 10" is the imaginary length of the 2nd wall

10*6.75*17.5/1728= .6835ft^3 (displacement of 2nd wall)

10-6=4 (so 1st wall imaginary length is 4")

if your talkin about this being 1 error it isnt. 10 was the number i used so in the first it is 10+1.5 and the answer just happens to be 10". then i use 10 and do not add 1.5" this time since im suppose to use internal depth and get 4" for the first wall length. im not actulally using that 10 that i got from the first equation in the second equation. of course that might not be what you were talkin about anyways lol. btw i see yoru computer is back up! awesome man

IgnoreMe
11-17-2004, 02:43 PM
nevermind i just redid it for the 4th time. maybe i should of quadruple checked my port length lol. that was off by a bit and threw everything else off. anyways got my 7ft^3@35hz box all calculated out and got my cutsheet written down. gonna go to the store and get all my mdf. hey anyone have a 98 explorer sport with 2 15" sx's in need of a free box plan lol. kinda limits who will be able to use it but what the hell ;)

IgnoreMe
11-19-2004, 01:51 AM
Still wrong ... ;)
i know lol. old_school kicked my *** a few times and showed me whats up. thanks for makin fun of my failures jmac :(