Final Build

[jshak07]

Building my final box for my subs, with help of course, and want to know if I have a good design and any changes that I might possibly need to make. Here is the basic design.

[CVStroker]

I can't read the numbers on the picture, they're too small

[jshak07]

Here is some numbers I came up with, tell me what you think
Box Dimensions - these are external dimensions, I will be using 3/4" MDF wood
Height - 32.25 in
Width - 36.5 in
Depth - 13.5 in
Port Dimensions
Height - 1.75 in
Width - 34.25 in
Depth - 13.5 in

[CVStroker]

I wouldn't build the port like that, either re-design the port, or use round ports. It's sort of an unwritten rule, but never use a slot port with a height to width ratio of more than 9:1

Your current design is 10:1 (assuming you're using seperate chambers, otherwise it will be 20:1) That opens up a nice big can of worms bringing on skewed tuning, and hella port noise (that's right, I said hella)

[jshak07]

How would you build it? I am a little confused on what to do. What kind of dimensions would you use?

[CVStroker]

Just redesign the port so that the width to height ratio is less than 9:1. More or less, just make the port taller, and not as wide. Make sure you keep the same port area and depth, and it will work fine.

[jshak07]

How about port dimensions of
H 3 in
W 12 in
D 13.5
This is for each port, there will be separate chambers.

[CVStroker]

That will be fine, but you'll ahve to make your port about a inch and a half longer to compensate. If you make the port 3x12x15, you'll be sitting golden

the 3x12 port will make 36" of port area, the 1.75x17.125 port was roughly 30". You have to make the port a bit longer to compensate for the greater area to keep the tuning intact.

[jshak07]

The depth I cant really change because i want my box to be a rectangular shape. Unless I make the depth on the whole box 15 in instead of 13.5in. I could make it somewhere around 3in by 10in

[CVStroker]

You have to bend the port. It's not hard, just takes a little math, make sure that you maintain 3" all the way down.

[jshak07]

how do i do that?

[CVStroker]

Measure along the center of the port (1.5" from the outside walls) Measure from the opening to within 1.5" of the back wall, then, from that point, measure the final length you need.

Cut your first port piece 3" shorter than the inside dimention of the box (to account for the pot bending). Then measure how high off that you need to make the other piece to reach the end of the port.

The black lines are a cross section of the port, the red line is how you measure the port depth. When doing a properly designed slot port, bending the port is almost always necessary.

[jshak07]

Is this my basic box design? What you mean by the curve?

[CVStroker]

Bingo, that's it.

[jshak07]

So actually how big is my box going to be with the outer dimensions of:
Box -
Height - 32.25 in
Width - 36.5 in
Depth - 13.5 in
Port - (each separate port)
Height - 3 in
Width - 12 in
Depth - 15 in (bend effect)

After taking the volume of the box, and subtracting the volume of the port and the wood that will be used, I came up with around 6.5 cu ft. Am I close? Do I need to adjust any measurements before I start the build.
Would I be better off making the box to where I could aim the subs downward into the box and have the magnets facing up?

[CVStroker]

No, you should be just fine there. Have the subs bounce off the hatch of the car for the best performance.

[jshak07]

So actually how big is my box going to be with the outer dimensions of:
Box -
Height - 32.25 in
Width - 36.5 in
Depth - 13.5 in
Port - (each separate port)
Height - 3 in
Width - 12 in
Depth - 15 in (bend effect)

After taking the volume of the box, and subtracting the volume of the port and the wood that will be used, I came up with around 6.5 cu ft. Am I close? Do I need to adjust any measurements before I start the build.

[CVStroker]

If you're looking for each woofer to see 3.25 cubic feet net, then your measurements are about as close as you can get them without giving yourself an aneurism. You should be good to go . . . now, what materials are you using, and how are you holding them together?

[jshak07]

3/4" MDF wood, and hold it together with some 3" screws is what i was plannin on using and maybe using something to make sure all my creases are sealed.. such as caulk

[CVStroker]

Bump it down to 2 1/4" screws. 3" screws are too long, you majorly increase your risk of splitting the MDF using screws that long. Just make sure you get the ones that leave a smoothe shank 3/4" long from the head of the screw.

Your best bet is to use a high quality glue to do the work of holding the boards together and sealing the box. Go out and get yourself a small bottle of Gorilla Glue. Dampen the parts to be glued, apply a THIN line of Gorilla Glue, and put a screw about every 8-10 inches, just to hold the pieces together while the glue hardens. You don't need much because that glue expands a LOT. Once that stuff sets, it doesn't come off or break. The MDF will delaminate before that seam breaks.

[jshak07]

is this a good box design to use with a kicker 2500.1(what i am thinking about gettin)? It wont cause the subs to bottom out will it?

[CVStroker]

Honestly, a 1500 watts amp would be plenty. You're only going to notice about 1.5 dB worth of difference between 1500 and 2500, but the 2500 will cost about $300 more just for the components to keep the properly fed with power. Plus, with 1500 watts, you wont have to worry about over-excursion.

If you are set on the 2500 watt amp, then set a high pass filter of about 30 hz to prevent any over excursion

[jshak07]

There is someone selling an 08 model kicker zx2500.1 for $400 that is still covered under warranty is the only reason I ask. If I did get the amp, I would just want to slide the switch to the HPF instead of being off or on LPF?

[CVStroker]

No, that HPF makes the subwoofer play everything from ~200 hz up, you don't want that. You want to get a cheap crossover that has the ability to set a pass band of 30-90 hz.

It will just be easier to get a 1500 watt amp, and it will be cheaper too.

[jshak07]

Had some measurements that needed to change. Will this still work for me?
Box Dimensions (outer dimensions)
Height 16"
Width 24"
Depth 36"

Port Dimensions
Height 15"
Width 10.5"
Depth 2"

How do these dimensions look?