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evilsaint
11-06-2002, 12:02 AM
Ok, I've been into car audio for almost 5 years, and I know how to make the measurements for a box, cut the MDF, and all that, but I have no idea how to attach the separate pieces together. The box I'm going to make will be relatively simple (Sealed single chamber for 2 15"s), so it shouldn't be too much of a problem, but what's the best way of attaching all the panels together? Should some panels overlap others and have screws through the overlapping panel into the one underneath it? What should I use to seal the cracks between pieces? Wood glue, super glue, duct tape? :D
How do I brace the box well so it doesn't blow apart when i'm slammin these babies? I've built everything from lego buildings to chevy 350's but when it comes to this i'm blown away at how clueless I am. :confused:

Heresy
11-06-2002, 12:20 AM
A box can be held together with nothing but wood glue or liquid nails if you clamp it tight and let it dry. Screws are mainly used because they are faster than clamping everything together and then unclamping everything. There is no wait time and you could literally make the box in a few hours.

To seal the seams, either RTV silicon or fiberglass resin, IMO. If you do a good job with the gluing everything together you shouldn't even really need this but it is always a good idea to be extra sure.:p

Braces should be put where the box stresses most i.e. long spances of board that are away from the walls. For two 15s in a single chamber, 3 or 4 vertical braces should work. Also, running additional braces where the walls meet help as well.

I wish I could explain this all better. Here are a few websites that might help:
http://www.dancetech.com/aa_dt_new/pa/construction.CFM
http://sound.westhost.com/sp-boxes.htm

They aren't exactly sub boxes but they work.

evilsaint
11-06-2002, 12:47 AM
Ok, couple more questions, some of which are pretty dumb ones...

How much does 3/4" MDF cost approximately per square foot?

Does it matter what kind of screws I use?

What sort of order would you go in to glue the pieces together?

How would you clamp together two pieces that form a corner after they've been glued?

If I didn't bother glueing the pieces together, put in plenty of screws,and sealed the cracks with RTV, would it make any difference in sound or stability as opposed to glueing everything?

Would 3/4" MDF be okay for a somewhat high pressure enclosure of this sort? Should I make the braces with MDF too, or should I use something stronger?

Should I just have my friend build this for me? :crazy:

Thanks for all the help with this, 'cause i'm certainly going to need it.

Frraksurred
11-06-2002, 01:09 AM
You can get a sheet (4x8) of 3/4" MDF for about $15-$17.

1 1/2" Dry wall or wood screws work well, but you'll have to pre-drill and counter sink the holes. :D

Cut and test fit all the peices first. Draw center lines for where you want your subs. You can use one of the sub gaskets or a strap of wood with a nail in one end as a compass to draw your circles When every thing's cut and tested, glue (don't skip the glue, wood glue is cheap) and screw the bottom and one side to the front piece, then top and other side. Before putting back on use RTV to seal every seam or gap inside the box. Put the back on last and reach in thru the sub holes to seal it with RTV. If you don't use a terminal cup, then drill holes just big enough for your spkr wire to pass thru and you're done (more or less). Let it dry over night, wire and mount your subs and give it a test run! :)

Oh and have your friend help you, but do it yourself, you'll be much happier and it will mean a lot more to you.

God bless you!

Heresy
11-06-2002, 01:44 AM
Here in AZ, I think MDF is $18 for a 4x8 sheet. I would say drywall screws would be the best but you can use anything. I just have personally vendettas against deck screws and wood screws(don't ask why). Order of construction is a personal preference like everything else in this world. I personally like to make a right angle with the back and bottom of the enclosure then do the sides and finally the front and top. For a box holding two 15s, a good set of pipe clamps should work; they are only limited by the lengths of the pipes. If you mean how exactly you do it, it's basically try as hard as you can to get a 90 degree angle. If it is a lil off, the mdf will be able to flex enough to conform to the (hopefully correct) measurements that were made prior. One tip: USE GLUE, LIQUID NAILS, ANYTHING TO HOLD THE BOX TOGETHER. The adhesive is what holds the box together for the most part, not the screws. Although I am sure you can try, I would never use only screws.

Finally, 3/4 MDF should be fine as long as you brace it correctly. Also, you may want to double up the MDF on the front where the subs will actually be resting. The movement puts enormus stress on the panel and it should be have horizontal MDF bracing as well if you intend to use only a common chamber(which I don't recommend). Sub boxes aren't hard to build unless you screw up the measurements or cut corners. Check all the measurements three times and don't think that saving a few bucks now is gonna help you in the long run. Other than that, these things are easy to make if you have a basic knowledge of woodworking.

awalbert88
11-06-2002, 02:30 AM
I think I paid about $15 for two 2x6 3/4" MDF sheets at Home Depot. I used nails and wood glue (a whole **** bottle of the stuff) to build the box for my JL 12W7. I then sealed it with a small amount of expanding foam to ensure no air leakage through the cracks. Not really needed with the glue there, but I just wanted to make sure, since removing the box from my trunk is not possible without first removing the sub from it, which ain't easy when you have twelve screws to get out!

Corsica
11-06-2002, 01:25 PM
when would u carpet it though (if u so desire to do so???

J

evilsaint
11-06-2002, 01:26 PM
good question cors, also, what's the best way to attach the carpet? Glue? staples?

Corsica
11-06-2002, 01:37 PM
That I can answer. Glue works and is most commenly used but staples stay on longer.


J

Heresy
11-06-2002, 03:51 PM
I would carpet it or at least put something on it to cover up the ugly screw holes. Even if you counter-sink them, they look pretty ugly. Afterall, the whole point of carpet is to cover up the mistakes and blemishes of construction.

Personally I use contact cement. Any contact adhsive will work if you follow the directions. If you are taking your time, use contact adhesive of any type. The 3M stuff is more expensive but sets faster while regular contact cement takes longer but is more reliable IMO. After the contact cement is cured fully, nothing can take the stuff off. I have heard good things about the 3M stuff as well but I am stuck in my ways.:p

JDoggHSTX
11-06-2002, 04:39 PM
Yeah. Do like I'm doing with my new box for my 3 12w3's: Whole S***load of woodglue, screw it, and then seal it w/silicone. This is my first home built box, but it is gonna be BAAAD!! the 3/4 in. mdf cost me around $17 per sheet. This is a stinkin truck box and it took nearly two full 4x8 sheets. lol.

evilsaint
11-06-2002, 09:25 PM
What is counter-sinking and how do you do it? Also, another stupid question, what's a good way for someone who can't even cut in a straight line to cut the circular holes for the subs?

Heresy
11-06-2002, 11:26 PM
Don't make cuts yourself unless you have to. Have all the measurements ready when you buy the MDF and have the people at the store cut it on a wall saw. This will make sure that all the sides are straight and parallel. If you must do it at home, use a table saw. I have used a regular circular saw with large sheets and I personally never found it all that accurate or easy.

Counter sinking is driving the screw either flush with the surface or a little under it. This is accomplished with a special bit that costs maybe a buck by itself or you can get combination bits. They work faily well but if you are opting for carpet, I don't think countersinking is as important. Good idea but not entirely necessary.

evilsaint
11-06-2002, 11:48 PM
Do places like home depot charge to cut the MDF for you?

Heresy
11-07-2002, 03:56 AM
Nope, 100% free of charge.

evilsaint
11-07-2002, 04:03 AM
Free is always good. Well, thanks for all the help man, and wish me luck.

AFLAC
09-25-2004, 09:31 PM
im building a box.. do i deff need MDF?? can i juss use ref. 3/4 in wood?

Acidburn
09-26-2004, 03:19 AM
jesus h. christ, this thread is almost two years old, thanks for searching but check the date before you post

yes, use MDF