Help with box for 2 x 12" SHOK

[OzzieComm]

Hi All,

I have space to house 2 subs for my car (Trunk) the dimensions of 900w x 450d x 420h measurements are in mm or Box in Inches are 34w x 17d 16h

Torres says this is 135ltrs or 4.23 cubic feet internal gross volume, so I think I have plenty of room to play with.

I'm wanting to run 2 x 12" Shok subs T/S specs below.

I've tried everything to get the required tuning for the subs, but just cant work it out, either the port area is too small or the tuning is too high.

Subs will get rated power or slightly more. ( Manufacture says 700 rms of clean power. )

Thoughts?

Thxs

Mike.

Triton 12″

re-7.6ohm
fs-34.925hz
qts-.578
qes-.650
qms-5.224
vas-1.495
sens-86.3dB SPL
mms-181.594
Mounting Depth : 162mm ( 6.4 inches)
Mounting Diameter : 280mm ( 11 inches)
2x 60 Oz motor,
3″ 4 layer copper coils

500 Watts rms

Recommended enclosure:

Sealed: 1 cubic feet

Ported: 2.2 cubic feet @ 33 hz

[philrab]

So, you have 4.23 cubes gross, without port or subwoofer displacement? Cause the port is going to eat into that quite a bit.

[OzzieComm]

Hmmm, good point, excluding port and sub(s) displacement.

Let me have a recheck in torres.

[philrab]

From memory (and I hate my memory, cause it lets me down all the time) when I built my last ported enclosure for an SA12 (2.12 cubes net, tuned to 33 hz) it started somewhere over 3 cubes gross before sub and port displacement (the port was 19" long or so, plus sub, plus bracing.) Just saying, you're right on the ragged edge for net airspace for those two subs ported, so if you need to eat into that for port displacement, you're gonna choke the subs to death fairly quickly.

Or, I'm misunderstanding you and you could be all good. Let us know what you come up with.

[OzzieComm]

Hmmm, just cant get it right, I can get the tuning to 33.74hz but the port ratio is at 1:8, port area is 32in sq
Net volume drops to 2.64 cubes
I'll try to get a pic up of torres.

[OzzieComm]

[philrab]

Maybe consider a passive radiator setup? That way the PR's won't eat up space like the port would.

Or, is there any way you can run an external port? Port through the back seat/ski hole/arm rest?

You know your vehicle man, gotta tell me if anyone of that sounds even remotely feasible, but I'm spitballing. I just don't see how a traditional ported box with those max dimensions is going to work well for two of those subs.

Unless, you would be satisfied running just one ported, or two sealed. Then we're talking a whole different situation.

[OzzieComm]

Morning... I have a ski hole where I could run an external port. I might sketch something up and see what I come up with.

Or.. What about aero port?

Thanks for your input btw, much appreciated.

[philrab]

An aero could be a smaller diameter, and by extension shorter, for the same tuning freq (aeros are more efficient, therefore can tolerate less port area without noise to a degree). They also take up less volume than a slot port.

All that said, if you can run an external port it'd help. Not sure how it would effect acoustics porting through the ski hole, or what direction you should face the sub if you go that route (I have a hatch). More research.

[OzzieComm]

I think my Woofer and Bracing was a bit large (Combined at 1cuft) so move them down. (Will need to confirm the area of the woofer)
This is with a standard round port, not flared at the end like an aero

In the below pic I have increased the port dia to 6" x 14.5" - This has increased the port area considerably to over 28 sq in
And net volume is 3.59 cu ft.

I think a round port might be the way to go.

Aero port http://www.parts-express.com/precision-port-6-flared-port-tube-kit--268-354 - for my reference