Box for 2 18" jl's

[Sleeklsc 5,000+ posts]

2 18w6's

I'll be building a box in the coming weeks. I have no way to haul a couple sheets of mdf home so I'll prob have lowes/hd/menards cut the wood for me. I want to stick around jl specs @ 1.75 per, can go up a little if I need to. I was gunna go 3/4 obv with a brace or 2 that I can make myself. I do have all the proper cutting/power tools to finish it up.

What kind of dimensions am I looking at? If 1 18" requires a 19x19x12.5 would a box for 2 be good at 40x20x12.5? How many cf is that?

Remember guys i'm a total noob at this box building nonsence. I've always been satisfied with prefab sealed in my past 20 setup's(I'm lazy, sealed is simple). But I want to do these right by putting in some time building a solid enclosure.

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[Moble Enclosurs 10+ year member]

if you have a few dollars to spend on a design, since you wanna do it right, I can design it for you. Pm me if your interested.

 

[Sleeklsc 5,000+ posts]

I'll let ya know.

The recommended 19x19x12.5 @ 1.75cf per is calculated using 1" mdf by JL.

Using 3/4", volume

38x19x12.5 @ 4.066

40x19x12.5 @ 4.288

40x20x12.5 @ 4.5

1"

38x19x12.5 @ 3.71

39x19x12.5 @ 3.82

39x20x12.5 @ 4.04

40x20x12.5 @ 4.15

Which would you guys pick out of the bunch? I would likely choose the 1" 38x19x12.5 @3.7cf or the 3/4" 38x19x12.5 @4.06cf the way I see it. What would the slightly bigger boxes offer me?

 

[Moble Enclosurs 10+ year member]

Sounds good!

 

[duanebro 10+ year member]

2 18w6's
I'll be building a box in the coming weeks. I have no way to haul a couple sheets of mdf home so I'll prob have lowes/hd/menards cut the wood for me. I want to stick around jl specs @ 1.75 per, can go up a little if I need to. I was gunna go 3/4 obv with a brace or 2 that I can make myself. I do have all the proper cutting/power tools to finish it up.

What kind of dimensions am I looking at? If 1 18" requires a 19x19x12 would a box for 2 be good at 40x20x12? How many cf is that?

Remember guys i'm a total noob at this box building nonsence. I've always been satisfied with prefab sealed in my past 20 setup's(I'm lazy, sealed is simple). But I want to do these right by putting in some time building a solid enclosure.

I have found that the saws at my HD are very good. Items get cut .25" off, and not square! I'd try having every thing cut big. And then cut it myself to the final size. If you put a like up to the specs on the drivers I will check there sizes if you want. To find box volume: h x w x d multiple these then divide by 1728. So 40*20*12 is 9600/1728 is about 5.56 cf. But this needs to be internal dimensions. so subtract 1.5 from all your sides and crunch the numbers again.

Duane

Woops, I see you are ahead of me! Sorry about that! LOL.

Can you find 1" MDF?

A bigger box will go lower, but with less power handling.

 

[Sleeklsc 5,000+ posts]

I edited my op cause the depth was actually 12.5 not 12. Either way I was using the 12volt.com Enclosure calculator to figure int volume. Is it still not right?

 

[duanebro 10+ year member]

That should work fine, small changes in box size don't make a huge diff in sealed boxes.

You should be able to build this out of one sheet of MDF. And those are big panels, make sure you brace than well.

Good luck,

Duane

 

[Sleeklsc 5,000+ posts]

I have no idea if I can find 1" or not yet, I'll prob just end up using 3/4" and brace it well. Good to know 1 sheet should do it though. If not I have a little over half a sheet at home to finish it if need be.

 

[Jroo 10+ year member]

I am very interested in what people will come up with in the next coming weeks for this woofer. JL was very clear that the 1.75 was what this sub liked and sounded best in. Over the next couple of weeks I know we are going to see crazy ported and bandpass designs for this. Just wonder how much improvement or killed 18" subs we are going to see?

 

[Sleeklsc 5,000+ posts]

I'm not looking to improve it per say. I'm just looking for the best size box in my limited space available. And from what people have said the miniscule diff in the 3/4" box sizes I listed won't be much of a deal. All I know Is I have to stay above 3.5cf for the 2 and below 40x20x12.5". That put's me from 4cf to 4.5cf, then factor in bracing/sub disp and that should get me between 3.5-4.0cf total.

 

[Joseph7195 10+ year member]

1" MDF gets kinda pricey, but it's well worth it. My local lumber yard ordered me a couple sheets and it totaled about $200.00 for both sheets. It may be cheaper or more expensive in different locations, but around $100.00 a sheet is a good estimate. I think with good bracing, you should be okay with 3/4 MDF though.

 

[Sleeklsc 5,000+ posts]

Ok, 1" is ruled out. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[duanebro 10+ year member]

I wonder why they dont rec. Ported boxes. It looks fine in a 3 cf tuned to 26 Hz.

 

[Sleeklsc 5,000+ posts]

Not sure. People have came up with boxes that look good.("on paper").

Ok, assuming each woofer has a displacement of .25, .50 cf total, I should prob lean towards the 4.5cf box 40x20x12.5 correct? - .5 sd= 4cf . If I put a couple 2x4 braces in there would that lower the total cf to 3.5ish?

Edit: Not to sure sd is a factor here considering jl prob factored in those #'s when building the recommending box.

 

[duanebro 10+ year member]

sounds good, have fun!

Duane