Fi BTL 18" N2 Box

[SubSam 21]

@ stang - I used to moderate the rockford forums for the better part of a decade, dishing out free CAD renderings of enclosure designs to anyone that asked nicely I bought my first pair of Q 15's a few months ago, and I've been real interested in Fi ever since. count me in for plenty of first and second-hand business, as I can't find a better value anywhere

[MikeMartel 64]

Can anyone anwser MY questions please? Im the op and it would be nice :S

[NDMstang65 403]

Alright, now i dont want to seem like i want everyone else to do my work for me, Iv just never built a box before... iv been trying to read up on how to measure the inside volume and the port ect. But I really dont understand it :S.. Now refering back to the suggested cut out sheet by Fi, i can keep all the dimensions the same except for the 22" height, the max i can make it is about 19". With that in mind how would i be able to change the box so i can keep it at the 7.00 cubic feet.. Sorry again, i dont want to seem lazy i just really cant wrap my head around it right now.

Give me a little bit to work out the math. It might be tomorrow evening before I can work it out and change the dimensions for you.

You don't have the sub yet..

Edit:

how wide and deep can you make the box and still fit in your car? I need those dimensions to go from there..because the box is already 40 1/2" wide..

I don't think you are going to fit that in your trunk.

[NDMstang65 403]

@ stang - I used to moderate the rockford forums for the better part of a decade, dishing out free CAD renderings of enclosure designs to anyone that asked nicely I bought my first pair of Q 15's a few months ago, and I've been real interested in Fi ever since. count me in for plenty of first and second-hand business, as I can't find a better value anywhere

Right on!

[MikeMartel 64]

Its a huge trunk ^^ Just to ball park it i have atleast 45" wide and PLENTY of depth, so you have alot of room to work with, thanks man.

[SubSam 21]

I can't tell you what an N218 sounds like, I don't think many could outside the Fi guys, but i caan yell you what winisd says

That's corresponding tuning @ 7 cubic for 28-32 Hz, its kind of your choice what you want the box to sound like... I was just fooling around over breakfast, I can make an enclosure design for you when I get out of work later today. My biggest question is how big is your trunk OPENING? Are you willing to build the box inside ur trunk if its too big to get in and out based on the opening size?

[MikeMartel 64]

Well, ill need to check that out, my opening size should be big enough for me to slide it in length ways then just turn it once its inside. But thanks a lot, this is a lot of help and i would have ended up screwing it up if i tried to get these dimensions myself.

[kirill007 52]

I can't tell you what an N218 sounds like, I don't think many could outside the Fi guys, but i caan yell you what winisd says

[img/img]

That's corresponding tuning @ 7 cubic for 28-32 Hz, its kind of your choice what you want the box to sound like... I was just fooling around over breakfast, I can make an enclosure design for you when I get out of work later today. My biggest question is how big is your trunk OPENING? Are you willing to build the box inside ur trunk if its too big to get in and out based on the opening size?

Remember that in a car you will never have that kind of respone, because of the car acoustics.

Sometimes you don't want a 'flat' frequency response.

[SubSam 21]

^^ he is 100% correct I should have said that actually lol sometimes I assume ppl know... anyways I promised to fix your design dilemma, so here goes

[SubSam 21]

First a rough outline of the box innards... bear with me this will take a couple posts

[SubSam 21]

A view outside

[SubSam 21]

I fully recommend 45's in all the corners, at a bare minimum these two corners, both being 5" long. You can go longer if you want, but no more than 5" in the port or you mis-tune it

[SubSam 21]

That's how I would do it

Did I mention the baffle is 1.5"?

[ssh 924]

Are you taking a picture of your screen? You can always press "PrtScn" on keyboard and paste image into mspaint, adobe ps, etc.

[SubSam 21]

So if you took off the top of the box this is what you should see after your 45's are in

So this particular design is 7.38 cubic NET @31.3 Hz after port displacement BEFORE sub and bracing displacement so once you brace it and throw the woofer in the volume drops to 7-6.91 cubic (depending how you choose to brace it) and the tuning crawls up just below 32 Hz. Hope this helps, if you want bracing tips I will gladly help you there as well

[SubSam 21]

Are you taking a picture of your screen? You can always press "PrtScn" on keyboard and paste image into mspaint, adobe ps, etc.

Lol don't worry I'm fully aware of prntscrn, but I'm sitting in my car with my laptop on the inverter in my center console and my 3G hotspot isn't working so I have to upload the pics off my phone.

I made my fiance go grocery shopping while I sit here and CAD a sub box she's the best in that regard

[ssh 924]

Are you taking a picture of your screen? You can always press "PrtScn" on keyboard and paste image into mspaint, adobe ps, etc.

Lol don't worry I'm fully aware of prntscrn, but I'm sitting in my car with my laptop on the inverter in my center console and my 3G hotspot isn't working so I have to upload the pics off my phone.

I made my fiance go grocery shopping while I sit here and CAD a sub box she's the best in that regard

Both of you sound like quite the best

Maybe I could pick your brain with an enclosure design sometime

[SubSam 21]

Center console wall sockets are so handy

[ssh 924]

your car is just full of surprises

[SubSam 21]

your car is just full of surprises

Lol yep got dual relays mounted under the inverter too... gotta keep those accessible until I finish the rest of the system... then I can flush the inverter in there and make it look pretty... don't worry, I will post a full build log when its done. Waiting for my N215 to arrive (Scott told me they ship out the 22nd), and I gotta finish by Dec. 2nd for an installation demo. Here's a sneak peak, haven't attached the baffle, tho I glassed it up good yesterday. Here's where the N2 is gonna sit:

And yes that triangular brace doubles as a mount for a triangular plexi window fiberglass corner bracing is a must also

[Duran 387]

Umm yeah, I fully support that design. I have a boner for enclosures with sufficient port area matched for the driver

Even more wouldn't hurt, but that's better than most people.

[SubSam 21]

Umm yeah, I fully support that design. I have a boner for enclosures with sufficient port area matched for the driver

Even more wouldn't hurt, but that's better than most people.

Yea I whipped up a dual 5" port design too, but I'm convinced he wouldn't be able to build it outside his trunk and get it in this design should be a good balance between ease-of-construction and proper enclosure performance, so I think...

Appreciate the thumbs up either way

[MikeMartel 64]

About those bracing tips . Haha. I'll need em

[MikeMartel 64]

About those bracing tips . Haha. I'll need em

[SubSam 21]

About those bracing tips . Haha. I'll need em

Sure man, you have several options, and if there's going to be no plexi window to see into the box then bracing should really be very simple and easy to accomplish. First, you have to just look at the box and see which areas have the longest unsupported regions. Just like you can't build a cantilever bridge that is too long without sagging, you can't have a long piece of .75" MDF without support. There is some volume absorbed in the bracing process, so if you are tight for volume its not clever to overkill the bracing.(I would say that you aren't tight for volume at all, but I know you want to stay close to 7 cubic, so lets be efficient with bracing here)

The style of brace depends on again how long an area needs support. Window braces, or the equivalent Y or H brace made from 1x1 or 2x2 lumber will serve you well for that long, unsupported length you have in the top piece of your box. You can use larger lumber, but I wouldn't use bigger than 2x3 for volume's sake. The left side of the box (as seen from the pictures) doesn't have the support of the right side as there is no port there, so you could use more bracing to prevent torsional flex not only from the bass but from driving forces. I would recommend cutting a few 45 degree cuts out of lumber to support it top/side and bottom/side. These cuts can be relatively short, if your window/H brace is wide enough.

If you made the 45's in each corner the way I recommended, those will serve as bracing as well, leading me to believe the last bracing you may want to add is to the baffle, tho its extra thick already, one 2x2 @ a 45 degree orientation from the bottom to baffle and top to baffle couldn't hurt, and the same goes for the back piece of the box.

Congrats. Your box should be braced well enough to run a car over it

Edited November 5, 2010 by SubSam