Please Help with 4th order design - Better Higher tuned design on page 2

[scooter99]

So here's the deal. I've already got a plan for subs and a blow through. I have a design that will do a slot port through the cabin tuned to 34 hz and that would be fine. But I wanted to see if I could do a 4th order on it. What I have is a truck box that I'm going to enclose it all in. That's been the plan all along. What I don't want to do is cut the entire back wall of my truck out, which is basically what it's going to take to do it. So I thought i'd brainstorm a 4th order to be contained in this box. That way I only have to cut out the port area and it will save me some strength and integrity of the cabin and bed walls.

**Higher tuned better design on page 2**

Some history and data

Truck: 1994 Ford F350 Crew Cab w/ 8ft bed

Subs: 4 - DC Audio Level 4 12's (recommended 1cu ft sealed / 1.5 cu ft ported)

Power: 2 - Soundstream Rubicon RUB1.2500D's

Truck Box Dimensions: 64" wide x 29" deep x 18" tall

There is a 2 inch lip above the 18" box, that's what the lid goes over. This is relevant for the design, you'll see below.

Pics of the box:

In the truck

Now onto the design I did. This was just a quickie in sketchup I did today. Here are the torres numbers

First is sealed - The sealed chambers are split in two. So the Torres calcs you see need to be multiplied by two to give you the total. But in breakdown, EDIT: I had the displacement wrong and only for one sub. So the actual on this is .36 for displacement. So instead of it being 2.40 total like I thought it's only 2.22 per side which is only about 1.1 per sub. So not as much to play with as I thought.

Next up is the Ported Calcs. This was just the area, not including the port itself, and maybe that's not the way it's done. However when you see the design below you'll see why I did that. That being said, I am still learning so that's why I posted this up so I can be corrected. Ported section totals 9.70 cu ft which breaks down to 2.425 cu ft per sub.

Now the ported. I don't know how to do the ported sections on a 4th order. I thought it was the ported section you calculate, not sealed, and then I thought I read somewhere or was told by someone you do the whole enclosure, sealed and ported sections together to figure it out. I don't know but this is what I came up with. Between the sealed sections (remember they're divided) I end up with a max of 9.5" wide. Then the height is at 16.5" tall. So I did torres on the whole enclosure specs, and put that in and got 34.89 hz with it being 15" long. 3 of those inches are external.

So I'm not sure if that's done right or not but again, that's why I posted this to find out and learn. Onto the sketchup designs.

This is what you'd see if you were looking from the tail gate into the truck bed. Minus the actual truck box of course. The part on top, is a 3/4" piece of acrylic or plexi glass. That's where that lip on the box itself comes in handy. Cause that can go in that and just sit on top of the box so to speak. Obviously it has to be sealed etc, but I think you get the idea.

Back areal view. You can see the separated sealed compartments here. The sub motors will go into the sealed sections and the cones will face the ported back sections.

Front cabin areal view

Front Port view - this is where I was trying to get to. The port area is basically all that will be cut through the rear cabin wall and the truck bed wall.

Forgot to mention also, I'll be bracing it with all thread and nuts. I didn't know how to show that on sketch up.

Also this is what it'll look like inside the cabin with the amps.

So there it is, my design. Now my biggest question is, will it work? If not what's wrong with it, what should be changed, etc? Thanks guys for any help. I don't know much, if anything at all, about 4th orders other than what i've seen on here and around the net. So I'm hoping to learn something from this. I'm not in a huge rush to build at the moment, god knows I have my hands full already with the rest of the vehicle. But I'd like to get a design nailed down so I know what direction to go when it is time ti get started.

Edited June 2, 2012 by scooter99

[bassface]

That looks like its going to be a bitch to do.

[scooter99]

Why do you say that?

[Sanitarium]

i like it! do it!

[bassface]

Well you need to build a box inside of a steel box that probably doesnt have perfectly strait sides. then you will have to somehow screw in your subs from the top which may be easy or ridiculously hard. The whole front bottom and side of truck box will have to be padded somehow or it will be rattling the hell out of the bed. I mean it looks cool, very james bondy. Goodluck on it man, im just thinking it will be much more difficult to do then you may be thinking.

[OrionStang]

I like the design, but I don't know how the metal box will do acoustically. Will you have room to get the subs in and out?

[scooter99]

Those are all good points. I'm not so worried about degree of difficulty, honestly, I'm not planning to do this over and over again. So I'll be happy to take my time with it and get it in and done. I'm not worried about straight sides etc either. I'll make sure the wood is straight even if the box is not. I do have to figure out how to secure it to the box itself but we'll see how it all works. If I knew how to GOD DAMN WELD, I'd just cut the side out on the cabin side, build the box, slide that bitch in, and then weld it back on. Maybe I could do that anyway and instead of welding it, screw it back on and silicone the seams. I am planning to truck bed line it anyway. So maybe I can use some polyurethane or something weather proof and then smooth it out and spray it. Should be good I'd think.

Aside of the degree of difficulty, what do you think about the design part? That's what I'm most concerned about.

[Sanitarium]

padding will not be needed around the box if the box is built right, just saying. if the box is rattling the toolbox, then the box is vibrating and needs bracing.

[scooter99]

I like the design, but I don't know how the metal box will do acoustically. Will you have room to get the subs in and out?

I do agree, and my plan for that is to deaden the inside of it before anything goes in. Hopefully that'll help.

As for the subs, yes, there's 13" from the front of the sealed sections, where the subs screw into, and the upper lip of the box lid. The subs are only 6.75" deep if I remember correctly, hold please while I look that up........................ Que jeopardy music...............................What is 6.75"? THat is correct! So yes plenty of space to put the subs in, even with my big ass body. And they won't be screw in, but allen head bolts into threaded inserts. So that will help for sure.

Also my plan is to make this out of birch instead of MDF cause it would probably only be my ass to be able to get it in and out of there. I can see the conversation with my wife now, "honey can you help me take the box out of the truck?" Her- "I don't think so, you're the dumb ass who decided to put subs in there and make it heavy. You do it!" You guys think I'm playing don't you!?! Plus the box doesn't just slide through the bed. I have to lift it up and over the wheel wells and down. It does slide between the bed rails up and over the wells so that's a good thing but it is a pain in the ass, and back, if you do it full and by yourself. So lighter the better. Also another reason to keep the port removable so I know for sure it slides right into place with no problems.

[OrionStang]

So are the walls of the toolbox the walls of the box? Or is it a whole box inside the toolbox?

LOL