obsidian subs

[dragonsage2008]

4 door blazer/jimmy... so i was thinking of a clam shell wall behind the back seat but much thinking im going to hold off.. cant do what i want to right now with the space... so i was thinking 4 obsidian 12s or 2 obsidian 18s... the 12s would be in a box 29D x 29H x 17D port 10x5 24 deep tuned around 29 hz subs firing up port back... the 18s would be in a box 38W x 25D x 17X port 10x5 and 20 deep tuned around 30... 12s on around 2k to 3k the 18s about 2k-2.4k.... i know the 18s have more cone area but would the 12s in this case be a better pic over 18s?

Edited May 8, 2012 by dragonsage2008

[john253a]

first thing first

download torres and play with it

now onto the problems with boxes

with 4x 12" box

29" deep x 29" width x 17" high = 6.8cuft gross your box is already to small before you even start

you need 1.75-2cuft net each thats 7-8cuft net required

if we use your second box for the 4x 12"

25" deep x 38" width 17" high = 7.7cuft gross (-0.16cuft each displacement) = 7.05, again to small, and once you take the port displacement, you'll be even smaller

10x5 port is too small also,. lets just say 15x5 (fits into the 12-16"sq recommendation's) box is 5.5 net @35hz or or 5 @33hz in 3/4mdf, way to small.

combine the 2 boxes

29" deepth x 38" width x 17" high = 9cuft gross in 3/4" if you use a slot port @35hz with either 1 or 2 common wall the best you can get is 6.3cuft net, still a bit shy but do-abull

but with 3 x 6" aero @ 22.25" you have 7.17cuft net @ 32.6hz (sub up port back)

now if you use the 2x 18 in the same box (29x38x17) ported will not fit(sealed yes, ported no) you need 5-7net each (10-14cuft net combined) unless you do them Iso-barik (read up on this, it may suit your needs)

so in the biggest box possible (29x38x17 given buy your dimensions) your options are

4 x 12" with 3x6" areo 22.25" long 7.17cuft net @32.6 hz (1.8 cuft net each)

4 x 12" with 3x6" areo 17.5" long 7.45cuft net @35 hz (1.86 cuft net each)

2 x 15" with 3x6" aero 22.25" long 7.43cuft net @32hz ( 3.7cuft net each)

1 x 18" with 3x6" aero 22.25" long 7.56cuft net @ 31.8hz

unless you want to go sealed but who want that

Edited May 8, 2012 by john253a

[john253a]

you could always chose different sub, witch will open up your options

[dragonsage2008]

ports will be fine and the 5 inch high 10 wide port will fit the 18s box i have all ready done all that stuff... boxes also fit the cuft factor... I AM NOT TUNING AT ALL THAT HIGH... no more then 33hz max....

[dragonsage2008]

nvm it will be 3/4 but there is still nuff room in both boxes also there is a factor of being able to invert if there isnt... monting depth on both from port to top will be 11.25" mounting depth. the 18s mount depth is 9" then the top will have a 3/4 mounted on top after its been made adding 3/4s to the 17" so that brings mounting up to 12" leaving 2inches bettween port and motor...

Edited May 8, 2012 by dragonsage2008

[john253a]

Build what you like, I don't care ant my box or my car

But 2x 18 in 5.5cuft net will sound like shit and make port noise like you never herd before,

What ask for advise if your not going to use it

There are some things you need to know when design a box

First what gross and net requirements for each sub

Port sizes, slot need to be 12-16"sq per cuft

Aero 9-13"sq per cuft

Now a 5x10 port is 50"sq that's that is for a box 3-4cuft net

That is why I suggest aero ports

2 resions

1 takes up less volume in box

2 requires less sqin per cuft and fits you box

[dragonsage2008]

cuz ur off on the math the 18s box with subs INVERTED net is 6.86 with subs in 6.36.. .25+.25=.50 6.86-.50=6.36..... that includes port displacement befor port its 7.69.. also if u think it will have port noise then tell me why is it i see builds with more 18s then that with port around 10x10 with out port noise??? and I WILL NOT GO AERO i dont like round ports i was forced to use a round port on my 10" type r box and i hate them allways will.... now i have seen builds of 18s in boxes of this size bigger 18s and sound grate... i have told u i have all ready checked all this math i have used soft ware also 6.86 DOSE NOT INCLUDE the added mdf to the face palate...

[Cadillac John]

Here is our buddy's blazer with 4 of their 15's

And space management and a loud system dont go together, so forget about the back seats..

[john253a]

Here we go I'll make it easy

25x38x17=7.69 cuft gross with 3/4(no bracing)

10x5x20 port will have a displacement of 11.5x5.75x 19.25=0.75

So your at 6.94cuft

Doesn't matter witch way you put subs for the 2 18 you looking at you still 4-7cuft short

And in a 7cuft box your port need to be 85-110"sq, and at 50sqin you only have 7"sq of port per foot

Once you lift the sqin of port up you take more volume away and you need a longer port also

If I were you down load Torres and play if it

[john253a]

another way you could look at doing it is to mold it into the seat like done here

http://www.newhilux.net/phpbb/viewtopic.php?f=41&t=8659

of a combination of both