TragicMagic

Hey guys.

I need to have a box built for my wife's 12" Eclipse sub. I put together a ported box for her last year, but we have a baby on the way, and we're going to need that extra trunk space.
I'd like to keep the sealed box as compact as possible, while still allowing the amp to be mounted to the back. Right now, the amp is fastened to the back side of the rear passenger seats, but its not all that secure.
The concept I sketched up is the route I'd like to go. Nothing is to scale, and I haven't figured out the dimensions yet.
I need one question answered. How close can a hole be drilled to the edge of the MDF before it affects the structural integrity of the wood? I don't want the edge popping off at the screw. I think that changing the orientation of the mounting ring, will allow me to shrink the height of the box. Hope you see what I'm getting at in the image below.

When I built the ported box, I had the help and tools of my mom's boyfriend at the time. Now they've separated, and I don't have access to a carpenter grade table.
I was hoping once I've determined the dimensions, someone could cut all the pieces I need, and I can put the box together.

Thanks for your time.

If you see any flaws in the concept, please let me know.

Lord Huggington

iTrader: (1)

Which model Eclipse?

What ohm is it?

What amp are you using?

What are the maximum dimensions you can use?

Where will it be placed in the trunk, the direction?

A screw isn't going to pop out if you make the box correctly and even if it did wood glue is actually stronger than screws. If you want it ultra sturdy, use 1" MDF, .25" rabbit joints (locking corners), good wood glue, a bunch of screws, a +1" front for 2" total, and sink the woofer 1" so it's sitting on 1". You could take the screws out and it wouldn't fall apart.

Why is it being bolted to the floor, is your wife a crazy driver? It's not like it'll look clean if that's all that's happening.

I emailed Eclipse awhile ago about box size for the SW8200 12". They said 1.5cf3 = 35hz and 1.75cf3 = 30hz. The displacement is .12cf3. I've used the SW8200 in 1.25 cubes, it gets low but should be in 1.5-1.75 to ****.

You don't need to know the verticle dimensions of screw-to-screw. Draw out the bolt hole circle and use a rotozip. Why would the screws not be over the wood? It wouldn't screw into the box. Most 12" subs use a 11-11.15" mounting cutout. You can mount it flush. If the subs outside diameter is 12.5" than you can use that. 1 subwoofer in a sealed box isn't going to cause any structural damage. It'd be nice to leave 1" between the sides just so you can avoid putting screws into the other dimensions of the box, just if you take it out and put another in the wood doesn't get as messed up, so shoot for 14.5" height x width.

Sealed box calculator
Speaker Enclosure Volume Calculator

With 1" MDF, 14.5 x 14.5 x 19.92 = 1.62 cubes.

With .75" MDF a completely squared 1.622 cube box = 15.6 x 15.6 x 15.6.

Lord Huggington

iTrader: (1)

Changing the circular degree of mounting does not lessen box height because the outside diameter stays the same, d'oh!

TragicMagic

The woofer is the SW7200. 500WRMS.
Dual 4ohm, wired in parallel for a 2ohm amp load.
Amp is a 3 channel DLS, which delivers the 500W on that 2 ohm load.

I don't have maximum dimensions. But I'm trying to keep the box as compact as possible while still allowing for optimum woofer performance, and being able to mount the amplifier to the box. MR2NR has suggested that 1.35cft will be ideal for this woofer.
I'm aiming to place the box on the either side of the trunk and have it face across to the other side. May not provide the best result, but we're going to have a lot of baby crap to move around. So I need to keep it out of the way.

I think you may have misunderstood my concern. I'm not worried about screws popping out after the box in constructed. I need to know how close to the edge of the MDF the screw can be placed before it causes that area of wood to pop off the side... If I pre-drill all the holes that would be less of a concern.

No, my wife isn't a crazy driver. But happens. I don't want 40 lbs worth of subwoofer and amp slamming into the seat which has my baby on the other side, in case she's ever in an accident or has to make a sudden stop.

Denonite

iTrader: (1)

there's no exact answer, mdf can split and separate even if it's 1/2" from the edge, it all depends on the type of srews, the quality of the mdf, pre drilling with the right size hole, and screw torque and speed...using a drill on high power can cause it to split, for delicate areas hand tighten. Secondly, always secure anything that can become a projectile in a car...instead of the elaborate and tall cradle, why not use L brackets and bolt to the floor directly, make slits in the carpet to allow bracket sides through and bolt to the sides of the box. see below.

TragicMagic

The L brackets would work. And cost less. Maybe I'll go that route instead. I'll need to take a look at the floor in her trunk and see how easily I can find a place to fasten them.

Don't judge the height of the cradle by the diagram. It won't be that large. I figured, if done right, it could add a little style to an otherwise plain box. The box won't just sit in the cradle, the cradle and box will be fastened to one another. I though that .5" thick MDF runners on the underside of the carpet would be strong enough.

I've decided that the box will be 18" wide, 14" tall, and 13" deep. That will give me 1.373cft of internal space. Minus the woofer's displacement. Pretty close to MR2NR's suggested size.

Now I just need someone to build it for me. Any takers?

Lord Huggington

iTrader: (1)

Call Home Depot, get the wood cut, and buy some screws & glue. Use clamps.

TragicMagic

Our Home Depot's panel saw is out by a quarter inch. At least it was when they cut down the last board of MDF to smaller pieces for me.

But its a good suggestion. They should be able to cut exact pieces to size for me. Maybe I'll go that route.