# Fi Q15 and Q18 box specs



## themerc (May 14, 2006)

Alright Fi recommends...

Q15:
Sealed box: 2-2.6 cuft
Ported box: 2.8-4 cuft @ 28-33Hz

Q18:
Sealed box: 4-8 cuft
Ported box: 6-10 cuft @ 28Hz

What would be the optimum box for a Q15 sealed? Q15 ported? Q18 sealed?

Thanks


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## Pitbullx (Jul 27, 2005)

anywhere within those ranges......


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## themerc (May 14, 2006)

Alright. I'm selling my two 400.1's and two cvr12's to my friend. I'm going to get a Sundown Audio SAE-1000D...

Q15 ported or Q18 sealed?


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## Brahma Brian (Nov 17, 2004)

> _Originally posted by themerc_@Sep 30 2007, 11:04 AM~8899718
> *Alright. I'm selling my two 400.1's and two cvr12's to my friend. I'm going to get a Sundown Audio SAE-1000D...
> 
> Q15 ported or Q18 sealed?
> *


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## themerc (May 14, 2006)

Okay. That 1000 watt amp and my 350 watt kicker amp should be fine with my single battery and big three upgrade correct?


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## draarong2004 (Feb 20, 2005)

> _Originally posted by themerc_@Sep 30 2007, 09:06 AM~8899724
> *Okay. That 1000 watt amp and my 350 watt kicker amp should be fine with my single battery and big three upgrade correct?
> *


might want to invest in a better alternator then stock down the road, or possibly a second battery, but it might handle it depending on how often you "crank" it


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## themerc (May 14, 2006)

Alright. It handled my two 400 watt amps and my 350 watt amp fine, I'm only adding about 200 watts.

I don't think I can fit a 15 ported with 4 cubes and keep my spare tire. I can probably do 2.8 cubes ported @ 33 Hz. Does that change your opinion about 15 vs. 18 Brian? I can probably do 5-5.5 cubes sealed with the 18.


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## Pitbullx (Jul 27, 2005)

> _Originally posted by themerc_@Sep 30 2007, 02:57 PM~8901107
> *I don't think I can fit a 15 ported with 4 cubes and keep my spare tire. I can probably do 2.8 cubes ported @ 33 Hz. Does that change your opinion about 15 vs. 18 Brian? I can probably do 5-5.5 cubes sealed with the 18.
> *


that makes no sense at all....


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## themerc (May 14, 2006)

> _Originally posted by Pitbullx_@Sep 30 2007, 04:31 PM~8901292
> *that makes no sense at all....
> *


Alright, I haven't gotten my measuring tape out in a while but I'm pretty sure my max dimensions are 37" wide, 21" tall, and 14" deep (to keep my spare standing up behind the box and the amp rack on the shelf). I'm pretty sure Fi recommended like 15-16 sq. inches of port per cube. To tune 4 cubes to 28 Hz, the port was around 45" in length, which made the port displacement for a slot vent huge. Plus the 15 has a sub displacement of .19 cubes.

But you're right about the 18 sealed. I can really only get like 4.75 cubes.


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## Pitbullx (Jul 27, 2005)

> _Originally posted by themerc_@Sep 30 2007, 03:37 PM~8901312
> *Alright, I haven't gotten my measuring tape out in a while but I'm pretty sure my max dimensions are 37" wide, 21" tall, and 14" deep (to keep my spare standing up behind the box and the amp rack on the shelf). I'm pretty sure Fi recommended like 15-16 sq. inches of port per cube. To tune 4 cubes to 28 Hz, the port was around 45" in length, which made the port displacement for a slot vent huge. Plus the 15 has a sub displacement of .19 cubes.
> *


actually the allround best tuning freq is 32-33hz and thats directly from Nick "4-millie" Morgan. Plus anywhere from 12.5-16in port per ^ft is good.


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## themerc (May 14, 2006)

Alright, I don't know if the port length is right, but I can do 3.25 cubes @ 33Hz with a port 2.5" wide, 18.5" tall, and 30" long (14.2 sq. inches per cube).









(20" tall)


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## themerc (May 14, 2006)

look good?


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## themerc (May 14, 2006)

Alright I'm going to increase the height by 1" so I can get some bracing in there from front to back and top to bottom... but I think it'll be just over 3.25 cubes... I may need to lengthen my port an inch or two because I'm increasing the height of the port an inch too... 2.5"x19.5"


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## themerc (May 14, 2006)

Some guys recommended I do 4 cubes if I can... how many sq. inches of port do those 4" flared aero ports have? because they have less port displacement so I'd have more volume to work with...


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## C-Bass (Jan 4, 2004)

I spent the better part of the day on the official Fi forum, and as you well know a few days trying to figure out all this porting nonsense .

Here's my observations so far:

-Math is not my forte
-Most of the guys running 18" subs are using big boxes. 6+ cuft (that's from my own observations)
-other than the 33Hz and 12-16sq.in. figures you are hard pressed to find any other info to go by. Seems like that figure applies to everything Fi, but is also a very generic figure when designing boxes
-There seems to be more people running the Qs (again my observations)
-The Qs seem to work well in all types of enclosures, but solid power is key

Here's something that's very interesting (to me anyway) and semi related

Fi does not recommend using the 15" SSD in a sealed box, but there is some dude out there with a 2cu.ft box and this very sub and the reports are that it sounds great.

There doesn't seem to be any "standard" configuration people are using for anything Fi

Personally...I'm leaning towards my box being sealed...fuck what Fi says, if that one cat with the 2 cube box can do it....shiiiiiiiit I got twice the volume

what's the worst that can happen :dunno:


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## themerc (May 14, 2006)

Yeah thanks for the reply man. I think I'm going to try a Q15 ported. My max dimensions are 37"x14"x21"... 

Well I want to do a double baffle, so my interior dimensions are 35.5" wide, 19.5" tall, and 11.75" deep. That's 4.71 cubes. Then I gotta subtract .19 cubes because of sub displacement. That's 4.52 cubes. Then I'm just anticipating bracing... and if I do a slot port the port displacement is a ton, so I'm thinking a 4" flared aero port would help me save volume... if it gives me enough port area. I emailed the company that makes them to find out the exact diameter of the outer flare.


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## C-Bass (Jan 4, 2004)

the precision port people have dimensions on their site. Not sure how that compares to the aero port but it can at least give you something to work with while you plan


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## themerc (May 14, 2006)

> _Originally posted by kannabis_@Oct 3 2007, 10:43 PM~8927557
> *the precision port people have dimensions on their site.  Not sure how that compares to the aero port but it can at least give you something to work with while you plan
> *


Okay sweet I found it. I couldn't find it earlier, thanks man.

OD of... 5.25" for 2" ports, 6.25" for 3" ports, 7.25" for 4" ports, and 9.25" for 6" ports.

I could do 2 3" ports, which would give me 61.36 sq. inches of port. If I did 4 cubes then it would be 15.35 sq. inches of port per cube.

I could do 1 6" port, which would give me 67.2 sq. inches of port. If I did 4 cubes then it would be 16.8 sq. inches of port per cube.


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## themerc (May 14, 2006)

I think 2 3" flared ports would be best. If I did my math right, that's only around .23 cubes of port displacement if they're around 8" long. That's perfect. I can even cut down my outer dimensions a little bit.


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## themerc (May 14, 2006)

But before I go ordering the ports, does everyone agree 4 cubes @ 33Hz is the best box?


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## Brahma Brian (Nov 17, 2004)

> _Originally posted by kannabis_@Oct 3 2007, 10:27 PM~8927440
> *I spent the better part of the day on the official Fi forum, and as you well know a few days trying to figure out all this porting nonsense .
> 
> Here's my observations so far:
> ...


It will sound fine back in the trunk, but you aren't going to be happy with the output at all...


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## themerc (May 14, 2006)

Wait, do flared ports just decrease port noise? Or do they add port area too?


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## Pitbullx (Jul 27, 2005)

> _Originally posted by themerc_@Oct 3 2007, 09:55 PM~8927675
> *I think 2 3" flared ports would be best. If I did my math right, that's only around .23 cubes of port displacement if they're around 8" long. That's perfect. I can even cut down my outer dimensions a little bit.
> *


nowhere near enough port area for that sub
slot port and round the edges over with a router



> _Originally posted by themerc_@Oct 3 2007, 10:08 PM~8927794
> *But before I go ordering the ports, does everyone agree 4 cubes @ 33Hz is the best box?
> *


you can go down to 3^ft net per sub ported but 4 is optimal


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## themerc (May 14, 2006)

> _Originally posted by Pitbullx_@Oct 4 2007, 05:31 PM~8932478
> *nowhere near enough port area for that sub
> slot port and round the edges over with a router
> you can go down to 3^ft net per sub ported but 4 is optimal
> *


Okay, today I unhooked the amps and subs and took it all out except the 350.2... then I made some more accurate measurements. I found that I can do 14" deep, 39" wide, and 21" tall (possibly taller, gotta get inside the trunk with the lid closed). I'll mess around with those numbers now.


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## themerc (May 14, 2006)

Okay. As of right now the new box's outer dimensions will be 39" wide, 14" deep, and 21" tall. The box in the picture is 39" wide, 14" deep, and 14" tall... so basically picture that box but 7" taller.

I'm going to stand the spare tire up behind the box. My old setup was very impractical and had I ever gotten a flat I would have had a spare and no way to get it without another person to help me get the box out.

Like I said, the depth of the new box will be the same, does that look like sufficient space in between the sub and the back wall?


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## themerc (May 14, 2006)

With my new dimensions I can do 3.75 cubes @ 33Hz with a port 2.5"x19.5"x25" long and have .13 ft3 left over for bracing.


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## themerc (May 14, 2006)

(21" tall)

3.75 cubes @33Hz... port is 2.5"x19.5"x25" long... I have .13 cubes left over I need to fill with bracing. How do you guys think I should brace it?


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## Sporty (Jan 26, 2006)

> _Originally posted by themerc_@Oct 5 2007, 03:51 PM~8939362
> *
> 
> 
> ...



easy way, or most efficient way?


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## themerc (May 14, 2006)

> _Originally posted by Sporty_@Oct 5 2007, 05:48 PM~8939678
> *easy way, or most efficient way?
> *


Most efficient under .13 cubes.


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## Pitbullx (Jul 27, 2005)

threaded rod

rope soaked in fiberglass resin


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## themerc (May 14, 2006)

> _Originally posted by Pitbullx_@Oct 5 2007, 11:11 PM~8941350
> *threaded rod
> 
> rope soaked in fiberglass resin
> *


Okay I can get 1/2" diameter, 6 foot long threaded plated steel rods for $7.99


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## themerc (May 14, 2006)

Well I can get 4 cubes if I use threaded rods and do a single baffle.


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## DARKJUGGERNAUT (Apr 14, 2004)

well after talkin to a few of my buddies back home they talked me into runnnin fi in my sq install in my jimmy-so i talked to the guys over a fi and we came up with a q 15 sealed in three feet with a g of like.712 which is s pretty damn close..so im goin sealed..on mine ..its only mdf if u dont like what it does rerbuild...


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## themerc (May 14, 2006)

What do you think? The 2x4's are there mostly to take up a little extra volume I had left over and needed to fill up. If there's a better way to place them, let me know. I figured I should put the four 1/2" diameter threaded rods from front to back positioned like a square around the sub. 

It came to exactly 3.9916 cubes after sub, port, and brace displacement.


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## themerc (May 14, 2006)

Well guys?


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## themerc (May 14, 2006)

Well I guess I'm going to go with that box. How should I do the threaded rods? Nuts inside and out? Washers? Recess nuts in second layer of baffle?


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