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View Full Version : 2 12"s or 3 12"s in only 7 cubic feet... could polyfill be the solution?



RSDXzec
06-20-2012, 02:48 AM
so i have 3 12"s and an amp that can take all 3, problem is i thought i'd have more room than i do. ideally i'd like 10cf, but i figured only 9cf would fit. After more considerations i'm left with 7cf external dimensions. I'm building this box for a hatchback and i'm really keen to have 3 12s in there but i'm not sure if it would work well. Would you guys recommend going for 3 12s or 2 12s in the same space, the box will have separate chambers for each sub and i'd be sending about 500wrms to them altogether either way.

The chambers will be tuned to 30hz.

My other thought was polyfill, if i put some of that in there would that theoretically increase the volume it sees? Hopefully i can get this closer to 9cf total.

Cheers.

subzero
06-20-2012, 04:12 AM
what does the amp do power wise with two subs only.? we need way more information. amp specs., sub specs

TaylorFade
06-20-2012, 04:18 AM
Since when is 7 cubes not enough for (most) (3) 12's?

And why seperate chambers? When using a common, you can get away with a bit smaller box.

RSDXzec
06-20-2012, 04:55 AM
what does the amp do power wise with two subs only.? we need way more information. amp specs., sub specs

subs are (soundstream) a single PCW-12 and two EG-12X, they both have exactly the same T/S parameters.
The amp is an audiopipe apsm-1500 which i should be getting in the mail next week so it's more than enough regardless of my setup choice, though i'll probably keep it at 500rms either way because my cars electrical isn't that great.


Since when is 7 cubes not enough for (most) (3) 12's?

And why seperate chambers? When using a common, you can get away with a bit smaller box.

Well the subs are about 5 years old, and they were bought separately on ebay so they would've been treated differently, so i assumed it was a bad idea, am i correct in saying that?

this sub is recommended between 1.25-3cf sealed, so i would've liked to go a little higher ported, i have been modeling them in winisd to get an idea of the response and keeping it under the excursion limits.

disturbed471985
06-20-2012, 05:02 AM
So ur gonna run different model subs in the same install????? Sounds great...

RSDXzec
06-20-2012, 05:08 AM
So ur gonna run different model subs in the same install????? Sounds great...

they have exactly the same T/S parameters, i think you missed that part, look exactly the same, they're just rebranded, the only difference is the letters on the back.
it's not like i'm running an L7 with a T6

this is an EG-12X
Soundstream EG-12X (eg12x) 12" Subwoofer - Sonic Electronix (http://www.sonicelectronix.com/item_5464_Soundstream-EG-12X.html)

PCW-12
Soundstream PCW-12 (pcw12) 12" High Performance Subwoofer (http://www.sonicelectronix.com/item_6343_Soundstream-PCW-12.html)

all of mine are the single voice coil versions, i'd like you to find the difference between them then tell me what i'm doing is wrong.

modelled the spl graph, and the cone excursion graph, red line is with 2 subs, and the excursion graph has been modelled as if they'd been in separate chambers, i also have the T/S specs in there. This is comparing 2 vs 3 in the 7cf enclosure tuned to 30hz.

http://i45.tinypic.com/2u9omly.png

disturbed471985
06-20-2012, 05:14 AM
hmmm like u said just rebranded old stock.. SS always on top of the cutting edge arent they..

subzero
06-20-2012, 06:11 AM
all three should work in a 2.5 cube sealed. 3 cube ported box.

RSDXzec
06-20-2012, 06:41 AM
all three should work in a 2.5 cube sealed. 3 cube ported box.

yeah no doubt they'd work in a much smaller box sealed, i'm just trying to get the most i can out of them ported. And when I look at the response curves i'm debating whether or not to have all 3 or just use 2.

subzero
06-20-2012, 06:58 AM
yeah no doubt they'd work in a much smaller box sealed, i'm just trying to get the most i can out of them ported. And when I look at the response curves i'm debating whether or not to have all 3 or just use 2.

notice they dont have recomeded spec on ported. do like I suggested. I used to have a pair or those tens. your guess is as good as anyone else. your not too far off RMS power. build it at sealed specs and add a port. andif it is too high, add fill. every cube, add one pound get 1/2 cube stimulation. then your still getting a 4 cube box with low tunning. just manipulate things and figure it out.