Joints for enclosures

[CrisTUFR]

Every time I see plans for making speaker cabinets, I feel as if people are using the most basic fastening methods around.

This is fine with me, since it's best to keep the woodworking as simple as possible to keep it open to those not totally comfortable with the tools and methods of cabinet making. Also, I haven't seen much discussion about which fastening methods are superior, etc.

I have access to the facilities to make dovetail joints, biscuit joints, standard glue/nail joints, dados, etc at my dad's woodworking shop. Also, most of the material I plan to use there is really high-quality stuff (3/4" Birch Veneer Ply, MDF, etc).

When starting my design for a cabinet, I just got stumped on what the absolute best method would be to fasten it all together. Since I have the tools/skills at my disposal, I'd love to take advantage of them!!!

Thanks,
Chris

 

[Ropie]

I suppose it depends on a few things:

do you want to be able to reopen the cabinet once it is sealed?
what angles are your joints at?
what size are your cabinets and how thick is the wood?
what design of speaker cabinet are you making; ie: transmission line, horn, bass reflex, sealed box, etc?

Personally, I butjoin and glue to make my cabinets, and I probably wouldn't do it any other way. I usually use plywood and I like to see the lined edge of the plywood.

Dovetailing may add a certain air of 'craftsmanship' (as long as you don't veneer over them!). Biscuit joins are popular because they are very strong and invisible, though basically it is just butjointing. Mitred joins are very tricky (believe me I've tried) even with good tools but the effect is nice and neat.

IMO screws are fine for joins as long as they are evenly spaced and secure though I personally don't like to see them on speaker cabinets.

 

[CrisTUFR]

I totally agree with the "look" of dovetails -- SO nice. Can you route plywood dovetail to a 1/4-round though? I've seen it done on hardwood, but would assume the plywood would chip to hell...

Biscuits *are* really strong. I don't plan on accessing them too much once they're DONE. So I will leave the rear baffle loose until I'm happy with the sound and then I'll weld 'em shut as best I can.

I really want to hear people's opinions on this stuff. My design right now will be totally sealed, but I'm curious what techniques are considered to have superior qualities over others...

Thanks,
Chris

 

[sreten]

No jointing method has any real advantage over another,
as in speakers rigidity may matter, strength of joint doesn't.

Performance of the caninet depends on design,
and there are a lot of options and opinions here.

Regarding joints you use the best /easiest for each application.

Bracing included in the cabinet makes most joint strengths
even more immaterial. The only real probem is the corners,
a locking mitred pattern is useful for good edge alignment.

sreten.

 

[Timn8ter]

For most projects I find that Dado joints are easy, strong and still allow you to do roundovers. I don't see a reason to make it more complicated than that. If you're using plywood and you don't want to see the layers just add a small piece of matching hardwood in the corner for your roundover. In the case of butt joints I usually add dowels.

 

[jjdche]

I just do glue and screw butt joints on everything I make. The way I see it is that the cabinets are never going to fall apart regardless of what type of joint you use (as long as you do it properly). I find it HIGHLY unlikely that the joint used will have even the slightest effect on the sound produced, so why not use the easiest one?

 

[markp]

I like to use a special router bit that does lock joints that are very strong and do not leak like straight joints can over time. It is a zig-zag kind of pattern that is used. I also use lots of 'figure 8' type braces spaced at uneven intervals. With the zig-zag bit there is no reason to use blocks in the corners.
My other favorite is to use octagonal cabinets with a 22degree router bit and biscuits. They are great because of reduced panel size and better resonance control. One day I'll post some photos.

 

[CrisTUFR]

I like to use a special router bit that does lock joints that are very strong and do not leak like straight joints can over time. It is a zig-zag kind of pattern that is used.

Do you have a model name, number, or picture for us?

Thanks,
Chris

 

[wharfrat]

IMO, simpler is better. MDF butt joints are more than strong enough for speaker cabinet joints; if you try to break a joint you will find that the MDF breaks before the glue joint. While dados, rabbets and biscuits are not generally necessary for structural reasons, they can be useful for aligning joints. Dovetails and the like don't make much sense in MDF, but with high quality plywood it can be done; the benefits are primarily aesthetic. Bottom line - use whatever technique you like, but even the simplest will work fine.

Larry M

 

[pjb]

mitre joints

I've found that if you're painting/lacquering the cabinets (as opposed to veneering) you'll certainly be best-served by
a mitre joint at the corners that doesn't expose a seam on a face.

 

[nubbins]

Just some food for thought...

Making Strong Wood Joints

 

[CrisTUFR]

Another interesting link if you are interested in building your speakers lock-miter style.

I think that the lock-miter technique is probably optimal with plywood, since you want to hide the ply at all costs.

If you lock miter, where do you do it? I'm assuming you build the "frame" (top, sides, bottom) that way, but there must be a different way to affix the front and rear baffles.

Any woodworking pros in the house?

 

[markp]

Do you have a model name, number, or picture for us?

Thanks,
Chris

Try http://www.rockler.com/ecom7/product_details.cfm?&offerings_id=2142

 

[Philo]

If you lock miter, where do you do it? I'm assuming you build the "frame" (top, sides, bottom) that way, but there must be a different way to affix the front and rear baffles.

Using a miter joint on a speaker is "do-able" but takes quite a bit of practice, set up and an occasional third hand to get it assembled with glue. If you look at the joint you can see the "direction" of assembly. Looking at the picture on the Rockler page, the left piece of the joint would be on all four sides of your top and bottom and on the vertical edges of the front and rear baffles. This is important as it will allow you to assemble in steps. At the corners of your baffles you are going to get a mismatch. You need to make a compound 45 degree notch cut across the corner where the two diferent patterns meet without cutting off any of the visable (after assembly) wood. This cut begins at the back of the board and goes 3/4-7/8 of the way through the board and looks like a dogeared page crease of a book. Make a few test boards and you'll see what I mean. You have to be close and accurate with this cut as it will leave a pocket in the joint if you cut out to much. Assemble the vertical sides first, clamp them snugly with two strap clamps, then put on the top and bottom. Clamp the top and bottom with bar or pipe clamps, then fully tighten the strap clamps. If you don't do your clamping in steps of pressure you'll rack the sides out of square and not get the top and bottom on before the glue sets.
Here are some other hints for miter lock joints:
1) USE A ROUTER TABLE with a tall fence or optional horizontal mount!!! Your joints with come out much much cleaner and better fitting. Feather boards are also a plus.
2) Use 45 deg bevel bit to remove some of the material before you use the miter joint. Your miter bit will last much longer and you get cleaner joints.
3) Once you get the router table properly set up for each cut make a setup sample to use as a guide for the next time. This is a major time saver in the future.
4) Do a FULL dry assembly first before you apply glue so you can check your joints. Use plenty of glue in corners for speakers as this needs to be airtight.

 

[markp]

The Rockler router bit makes panels that assemble very easily. They almost hold each other together which is why they are so airtight too. Large glueing surfaces create a bond that won't let go ever.
Take a look at their bevel router bits too to make multi-sided boxes that sound and look great compared to a cubish thing.
As a side note, don't dado in your braces as it weakens the panels structure. Just butt glue them in or use two or three small biscuits.