[Stereodude]

So, I have this brilliant idea rolling through my head to build a new sub that looks something like this.

The box is 25.5" x 25.5" x 30" made from 3/4" Baltic Birch. There is a 14" recessed hole in each of the four sides and a 20" hole recessed in the top.


I came up with something like this:

(Note three corner braces closest to the viewer are hidden)

Another view:

I do have some concerns about the feasibility of assembly and complicated design, but have really struggled to come up with a robust bracing solution that's much different.

Any suggestions on how better to brace the box or how to simplify the design without compromising the rigidity?

 

[asarose247]

this is coming from having read a few things about bracing ,here at AVS, the marty FAQ thread, other things that pop up when you google bracing
most agree that where the edges of the panels meet is already strong,
and BF has made some revealing comments too . .
is that enuf? I don't know but looking at things like that has tendency to see how smarter folks (real engineers) get to the simplicity of things, unlike the homegrown folk . . .


you're looking to stiffen panels away from the edges in a dimension of thirds, that makes sense, 8" is about the max


why not a simple piece ,cut with 45 angles that brace across the 1/3 dimension from panel to panel, I visualizeed 16
and for the bottom maybe 2 pieces of 1 by, 3" x 20'" on 8' centeres


may cut down on the work unless you can program a CNC


interested in how this come out


Is this an 18" with 4 PR's?

 

[asarose247]

those "simple pieces" maybe 2 1/2 wide. 2 kregs screws at each end/ attachment surface and, of course,
PL


might have to trim some of points/end wrt to fitting wrt to the mounted interior baffle brace


.02


subscribed

 

[Kubbie]

Double 3/4" BB glued/laminated together, all 6 sides of the box?
I really think 1.5" will be very stiff on it's own.

 

[rhodesj]

I don't know that those curved braces are going to do much. I'd just run dowels across from side to side at the edge of the woofer cutouts, at the 45 degree corners of the cutouts.

 

[OHMSEN]

I don't know that those curved braces are going to do much. I'd just run dowels across from side to side at the edge of the woofer cutouts, at the 45 degree corners of the cutouts.

Rods or dowels. May not need anything. How loud will you play it?

 

[Stereodude]

why not a simple piece ,cut with 45 angles that brace across the 1/3 dimension from panel to panel, I visualized 16
and for the bottom maybe 2 pieces of 1 by, 3" x 20'" on 8' centers

You mean something like this for the sides (but obviously with a bunch of them)?

interested in how this come out

You and me both.

Is this an 18" with 4 PR's?

No, 21" with 4 15" PR's.

After thinking about it more I think something like this will yield a stiffer box and be easier to make. I need to make sure the upper ones will clear the motor of the driver though they may need to move.

 

[Stereodude]

I don't know that those curved braces are going to do much. I'd just run dowels across from side to side at the edge of the woofer cutouts, at the 45 degree corners of the cutouts.

Yeah, I had the same thought about the arches and the rods / dowels.

 

[asarose247]

3 precious words; Some Assembly Required


decidedly easier looking . . .

 

[Stereodude]

How loud will you play it?

Good question, I'm not entirely sure. However, the goal is high output and am planning for 2400W of power on tap.

 

[HopefulFred]

That's what I would do - only I would ditch the corner braces and notch the cross braces so they locked together. There would basically be two window braces which you could then tie into the top and bottom.

 

[Stereodude]

Double 3/4" BB glued/laminated together, all 6 sides of the box?
I really think 1.5" will be very stiff on it's own.

That would certainly be simple, but probably end up heavier and I'm not sure how it would compare for stiffness with a well braced box.

Unfortunately, I'm not a mechanical engineer, nor do I have access to finite element analysis software.

 

[Stereodude]

That's what I would do - only I would ditch the corner braces and notch the cross braces so they locked together. There would basically be two window braces which you could then tie into the top and bottom.

You'd ditch all the stiffening ribs too?

There's very little material left on the top, so I'm not sure that the "window braces" could tie to the top.

They could tie to the bottom, but without the ability to tie the top and bottom together I don't think it would stiffen the bottom very much. I'd probably want to keep the stiffening ribs on the bottom to keep the bottom from flexing.

 

[HopefulFred]

I would - but I am not an engineer or anything.

 

[Stereodude]

I would - but I am not an engineer or anything.

I am, but not the right kind for the topics of bracing, panel stiffness, etc.

The two tick-tack-toe window braces, stiffening ribs on the bottom, and the double layer baffle should keep panel flex and resonance to a minimum.

 

[Mrkazador]

Are braces even needed for a design like this (brace the bottom panel only)? The bracing looks complicated, keep it simple stupid.

 

[Stereodude]

Are braces even needed for a design like this (brace the bottom panel only)? The bracing looks complicated, keep it simple stupid.

Why would you think this sort design is immune to panel flex?

 

[Mrkazador]

The PR is going to take up most of the space and there won't be much of a panel left to flex. The edges are going to be strong so theres no need to brace that area. I'm no expert in this, just my guess.

 

[Bill Fitzmaurice]

this is coming from having read a few things about bracing ,here at AVS, the marty FAQ thread, other things that pop up when you google bracing most agree that where the edges of the panels meet is already strong,

+1. The box corners are the strongest area of the cab, and don't need any bracing. The middle of panels is where flex is highest and where bracing is critical. Since this design has no middle of the panel per se there's nothing to brace. What I would do is run 1x1 braces connecting the opposing PR mounting screws. Four per PR pair should be sufficient. The top mounted driver not having an opposing driver I'd connect braces from its screw attachments to the bottom.

 

[genofive0]

Mc escher is loving this build :/