A question about Adhesives and enclosure bracing.  

For all my speaker boxes I always (you dont have to) screw and glue. I glue with elmers wood glue and counter sink holes for screws and you can build your box or boxes faster. I always also use silicon caulk for all seams on the inside just to make sure to be air tight. Also 1lb of fill for every cf of box area.

Oh by the way if you go thr glue and screw method the best filler for the holes is bondo. but make sure to get any of the sawdust in the holes with an air compressor. And avoid wood putty if you plan on doing any veneir. Standard wood putty has been known to work loos and cause bubbles.

The various wood glues are more than strong enough, but the poly glue (I use Gorilla Glue) will expand to fill gaps so you don't have to use caulk, sealer, etc. A pain to use compared to everything else, though, so as my cuts have gotten better (thanks to a table saw), I've gone back to Titebond or Elmers' for ease of use and cleanup. I don't use screws, just lots of clamps.
Stick some crossbraces in to tie opposite sides together, should be fine.

Poly glue (such as Gorilla or other brands) is great stuff. Applied properly you will have a strong joint for centuries.

A word of caution. . .Yes poly glue does expand (which can help fill joints), however it expands with significant force. If you go too crazy on the amount of glue or do not have your joints clamped or screwed firmly during set-up, the poly glue may actually force the joint apart as it sets-up and expands.

Bondo or a similar 2 part auto body filler makes a great filler on joints, screw holes, and various mistakes. It is quick and strong and most importantly, very easy to machine and sand smooth. Since you are going to laminate or paint the box you don't have to worry about tiny cosmetic boo-boos- that’s what the filler is for.

Handle the joints however you want. Screws (give square drive screws a try- it will make your life much easier) are great for putting the box together and holding while it sets. Remember that MDF is tricky and it is easy to 'strip out' screw holes. Be sure to pre-drill and counter sink. Sock down the screw enough to pull the joint tight but don't over tighten- the screw will pull the MDF apart around the hole. MDF is wonderfully strong, dense, and stable. It is, however, very weak when it comes to holding fasteners. (Give biscuit joining a try as you progress).

As for doubling up the front panel- go for it. If you double-up panels you can stagger-step the joints (sort of like rabbetting single panels) and get a much stronger joint. Be sure to leave some room around the driver so it can 'breath'. Lots of folks bevel the inside layer or cut the inside hole a bit large than the driver to give some room.

More important than just panel thickness is to cross brace as Jack suggested. A couple or 'shelf' braces or simple scraps across the inside adds a lot of strength.

Good luck and share your results.

yeah, just till the glue dries. These are my clamps, I could probably use a few more:

http://home.comcast.net/~tgilvey/IMG_0802.JPG

It's certainly cheaper to screw and glue, some of them weren't cheap and it probably wouldn't make sense for a single project.

Elmer's wood glue and sealant would be easier, I wouldn't bother using both Elmers and the poly.

liquid nail and screws has always worked best for me i use to build custom speaker boxes for car audio.

build your box first and then go back and seal the seams inside the box where the wood meets.make sure you cut the whole for the speaker before building the box.

Is it alright to use finishing nails instead of screws?

You can remove the screws after gluing if you are then going to use a router to round off the edges. After routing put the screws back in. Just a hint that I read elsewhere.

Bob

I would screw the box together first, making sure it all positions perfectly. Back the screws out, glue it up, then the screws go back in quickly and are just used as clamps really, holding it together while the glue dries.

Here's an example of shelf bracing from Dan Marx:

http://www.danmarx.org/audioinnovati...ics/Image7.jpg
It typically ties four sides together, and is not to be confused with braces for shelves. :)

Yeah - What Jack just posted is an excellent example of shelf bracing.

However, if that looks like too much work- don't worry. Even just using scraps of plywood (plywood do to its being constructed of mutliple layers with the grain running in different directions tends to be pretty stable- its just though to screw into the ends of it) or hardwood is better than no bracing (although its generally better to stick to the same material- the reasoning being then at least you should have similar rates of expansion and contraction due to humidity changes- but not a huge deal) .

Use MDF if you can but scraps of hardwood are good and even pine is better than nothing. It doesn't have to be pretty, just functional. The bracing is there to keep the walls of the box from flexing do to changes in internal pressure.


Metal 'L' brackets or metal corner braces won't do. For the same reasons I described above- its hard to fasten them into MDF. 'L' brackets are mainly designed to secure the joint. That shouldn't be a problem if you follow the advice posted by others. The joints (or corners) of your box won't be the problem. The weak point will be the big square or rectangular walls of the box. They will want to bow out under pressure, like blowing air into a milk carton (or a soymilk carton for us vegans). A simple pice of 1 x 4 going across the interior will probably provide more support than 10 metal corner braces. Four pieces of 1x4 (2 from front to back and 2 from side to side), glued and/or screwed to each other where the intersect at the center of the box is easy to do and will make a big improvement. The example posted by Jack is great but it would be just as good, instead of cutting the brace from a single piece of MDF, to glue it together with rectangular strips of MDF. It won't be quite as slick but it will do the job fine.

Remember to subtract the volume of the braces from the box volume when designing.

Tightbond glue worked a lot better forme.
I would apply the glue, fit the box up, clamp tight, then add additional screws to hold the box together because I didn't have enough clamps, and because I don't trust glued joints, regardless of what eveyone here says, and then let dry. Make sure you are doing this in a heated space right now.

Don't buy clear silcone sealant for inside. You won't be able to see it as you apply it. Trust me. :)

Don't use liquid nails, the multi purpose one doesn't fully harden and remains slightly flexible.

doatis' post says it all, the problem won't be the seams, it'll be the larger unsupported spans.

And screws are great as clamps if you don't have enough clamps. Once dried, a glued joint is stronger than the wood itself, so you can pull the screws out at the point if you need to (if you can't countersink).

I've built a few dozen boxes in the last 6 years or so and have always used liquid nails and brad nails. The brad nails holds the box together enough till the liquid nails dries and its worked great until the past few month, I started using titebond and elmer's. I like it a lot better, but I still bust out the liquid nails if I have a little extra gap. I've found that wood glue only works good if you box fits really close to perfect, anything beyond that, use liquid nails. Lots of people will tell you to use screws instead of nails, but the screws or nails don't hold the box together, the glud does.

A countersink drill bit from Lowes will run you about $5.

Do I have to cover all of the internal walls with some type of sealent or is it ok to just seal the seams?

Sealing the seams is only used when the woodworker makes errors in construction.
If you didn't error and sealed the seams anyways, then it's still ok but you are
just doing another step that you don't need. If you cut your wood straight and secure
it properly, the joint will be stronger than the wood itself.

To clarify, when you use yellow wood glue {Elmers, Tightbond, etc}, you apply
a generous amount and wipe off excess with a damp rag, use your finger to
clean the edge of the excess glue and it should be sweet.

If you use silicon, make absolutely sure it's completely cured before installing the driver. The fumes given off can act as a solvent.

With the two subs I've built so far, I have found this method to be very effective. It only works if your going the double wall, so I guess it doesn't apply for your project. When a guy applies the veneer (or some other covering) it adds to the integrity of the seal. I did glue the inside seems for extra measure though. It sure is a good feeling when you load the driver for the first time and push it in looking for resistance..That sounds kind of odd, but you'll understand:). The extra room around the driver sure comes in handy like mentioned, along with a extra 6-12" on your lead...a little wriggle-room makes adjusting the fill and getting at the driver much more pleasant.

Going extra thick on the baffle is a good idea.. you'll be glad you did.
You want a plunge router. I made the mistake of not getting the plunge and had to take it back. I just went with a RYOBI at HD...cheap but effective. If this is going to be a one time project?.. you could probably barrow one no?

Is this what you mean by flush then? ;) One more 1/2" panel was added to the baffle after the two 3/4" panels set up which is pictured.





http://i3.photobucket.com/albums/y75...n/100_0819.jpg

From experience, I'm not big on buying cheap tools. If you're really never going to use it again, see about renting. The Jasper jigs are great, great tools. I have all three models but the middle size never leaves my router:

http://home.comcast.net/~tgilvey/IMG_0809.JPG

The router's a DeWalt 621, which is a perfect plunge model for speaker-building (size, handling, dust-collection, power) and the compatibilty of which I made sure of with Jasper prior to purchase. There are other great ones, and you'll be glad you bought quality each time you use it.

Actually.. no it's not. Cone excursion will travel beyond, but you should be sitting pretty good. With me using the SS 15" RL-p D2 drivers, I added the third layer on the baffle more for strength.
A very good practice. It's not absolutely necessary, but it sure wont hurt. It'll only add to the integrity of the unit.
Looks like your getting close then. With overlapping the joints with your second layer, you should be pretty sealed up.
I can certainly understand that.