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Discussion Starter · #1 ·
I've sourced Baltic Birch Plywood as well as a millwork... seems like I have a friend in the buisness out here, so I may even be able to get a good deal on getting the wood, cuts, and possibly even some quartz, granite, corian, or similar countertop type of covering for the subwoofers. Otherwise I'll probably use Wilson Art Laminate (like last time) if other materials are too expensive...


It looks like I'm going to need (8) 4' x 8' sheets of Baltic Birch for this project.... Although I'm playing with the cuts on graph paper to see if I can reduce it to 6 or 7 sheets...


Anyway, does anyone here use anything other than gluing simple butt-ends? I have a millwork at my disposal so I am considering doing something more 'interlocking'... it has been about 6 years since I build my last subwoofer, so if anyone has suggetsions for something other than gluing simple butt' ends, that would be great... may as well put the millwork to use... I like to do the gluing and assembly, but I prefer to have precision cuts made by the millwork... saves a hell of a lot of time also...
 

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With modern glues it is not really necessary. (West Epoxy my usual) Butt ends are more challenging if you are painting. No issue if you are veneering. I try to miter for painted boxes on the edges I will see. Granted, I try and hide my subs. If you want it visible, all kinds of fun with the plywood edges and patterns can be had.
 

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Discussion Starter · #3 ·
I guess most people clamp only (no wood screws) these days?


Yea, I was entertaining tongue and grove or more complex joinery I guess... I forget what glue I used last, I think it was waterproof glue, something with a blue tip... It was wood glue, not Epoxy.


What glues do people use here?
 

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I bought a Sears pneumatic brad gun years ago. One of the best decisions I ever made. Still clamp, usually with webs.


I also use Titebond and Gorilla. Depends on what I am doing or if I am in a hurry. Subs I consider high stress due to weight, so I use WEST System. It has some give as it is designed for wooden boat building.
 

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If you're going to be covering the enclosure, you could use Aracuo plywood. It's just as light as baltic birch, virtually void free and very stiff. Alot of the pro builders use this stuff.


I just got finished building a horn with the 1/2" variety. Way more stiff than the 3/4" MDF I used to build my smaller 13 cu foot EBS/LLT last year.


As for glue. nothing beats PL Premium adhesive for air tight speaker enclosures.
 

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Quote:
Originally Posted by Fatawan /forum/post/17032081


Good article on how to set up lock miters

http://consultingwoodworker.com/yaho....177140004.pdf

I just did some routing with 22 1/2 bits free hand to get a 45 degree angle join last night. I also did some 90 degree ones. I purchased all the bits off ebay recently.


Router table would be nice but I had success last night!
 

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Discussion Starter · #10 ·
Good stuff. I like the lock mitre, I will definitly do that. Question: with a mitre (lock) cut, it looks like I will have to make the lengths of the cuts all equal to the outer dimension of the box (unlike but ends where some cuts are shorter by the thickness of the wood... correct? But wait, that seems to be good for ALL 4 WALLS, but how about the top and bottom?? How can you do a lock miter for the top and bottom once you have done all 4 of the walls??? do you have to make the top and bottom butt-end only?? (seems like you can do 4 out of 6 walls with this technique only...)


I have used titebond III, they have a blue tip version that says waterproof I think... Have not tried PL Premium. What is PL Premium?


I never used EPOXY since it seems to be less 'rigid' upon drying.
 

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WEB clamps. Basically belts that are easy to snug up. You can do just as well with rope and a dowel. They are a lot easier to store than piles of 3/4 inch black pipe!


Epoxy varies with its rigidity. You select the correct one for the use. Wood moves. Speakers vibrate. That is exactly why I like the WEST epoxy. That is why it is the ONLY glue I would use in a Morgan body frame. Titebond is very compliant when dry. It was designed for wood too. Old hide glue is very rigid. (brittle). That is why they use it to glue things that you may want to take apart. A shock will break it. If you glued a violin together with Titebond, you could never repair it!
 

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Quote:
Originally Posted by Health Nut /forum/post/17032588


Good stuff. I like the lock mitre, .

The lock miter is a good joint, just be aware that you will need a router table for the lock miter and the setup for the bit cut height/depth requires a lot of adjustment and test cuts.


Regards,


Dennis
 

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Quote:
the setup for the bit cut height/depth requires a lot of adjustment and test cuts.

Aint that the truth, I did it last night free hand with 45 degree joints
Its not perfect but the results are still good enough and I can sand down the problems.
 

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Quote:
Originally Posted by Erich H /forum/post/17035839


What about just using a biscuit joiner?

Biscuits are great for cabinet face frames and table tops, but to just keep a simple box in alignment while the glue sets, I found brads are easier. I also found biscuits have a habit of splitting MDF if you use a water based glue and cut in a parallel plane to the surface. At any angle, they work fine. OK in plywood. If I were using pre-veneered ply, they are a valid option. I have the DeWalt jointer. Even being careful, I have to make test joints.

For a big sub box, you could use pre-fixed cleats inside the box. Screw from the inside and still have a perfect exterior. I never use cleats, so whatever. It does not make sense to reinforce the strongest part of a box, yet some do.
 

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Quote:
Originally Posted by Health Nut /forum/post/17032588


Good stuff. I like the lock mitre, I will definitly do that. Question: with a mitre (lock) cut, it looks like I will have to make the lengths of the cuts all equal to the outer dimension of the box (unlike but ends where some cuts are shorter by the thickness of the wood... correct?

Right.

Quote:
But wait, that seems to be good for ALL 4 WALLS, but how about the top and bottom??

Same thing.

Quote:
How can you do a lock miter for the top and bottom once you have done all 4 of the walls??? do you have to make the top and bottom butt-end only?? (seems like you can do 4 out of 6 walls with this technique only...)

Cut the top and bottom of the sides flat on the table and all four edges of the top and bottom vertical against the fence. One pair of sides have their vertical edges cut against the table, the other against the fence.


Use a tall sub-fence.


Use double sided tape to stick a straight piece of scrap to the top of your work because the lock miter wastes the whole edge. Stick a sacrificial backing piece on to avoid blow-out. Use multiple passes.


Do not dry fit without having the driver hole cut-out because you won't get it apart to glue.


IMPORTANT: The lock miter joint is nearly air-tight and half end-grain in plywood. PVA sets up _real_ fast allegedly due to the moisture getting sucked right out in such situations. Even using a fresh bottle of Tite-Bond Extend. If each piece isn't square by the time you have all four sides together you'll be stuck.


I switched to epoxy after learning the hard way.



Quote:
I never used EPOXY since it seems to be less 'rigid' upon drying.

It's plenty rigid and doesn't creep like PVA. The down sides are that you get bigger glue lines, it soaks in more than PVA (you need to use tape to keep squeeze out off), it takes solvents to clean up (white vinegar actually works), you need to wear gloves, and it's not inexpensive.


The big wins are that it's structural across large gaps, takes no clamping pressure to form a strong bond, and can be had in any open time you want for complex glue ups (T-88 is about 45 minutes).
 

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Quote:
Originally Posted by djarchow /forum/post/17035204


The lock miter is a good joint, just be aware that you will need a router table for the lock miter and the setup for the bit cut height/depth requires a lot of adjustment and test cuts.

A little measuring and knowledge will let you get it right on the second try (provided your stock is of uniform thickness. The lock miter bit indexes off the bottom surface and what you see is relative to the top so it's sensitive that way)


Cut two pieces against the table, one face-up and one face-down.


If the short side is high the bit is too high. If the long side is high the bit is too low.


Measure material thickness with your dial calipers, measure again across the mated joint, take the difference, and divide by two. That's your bit height error. Correct.


Set the fence so that a flat surface laid across the top of your work intersects the bit edge at the fence. You can use the same method of adjustment if you need to. Moving only one fence end results in half the depth difference of how far you moved it. Clamp stop blocks to the router table top behind the fence and space it out using your feeler gauges or shim stock.
 

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Quote:
Originally Posted by Health Nut /forum/post/17029205


Anyway, does anyone here use anything other than gluing simple butt-ends?

This baffle and top are mated to birch lumber edging with a ship lap. The braces join in the center with an edge lap with an extra set of shoulders. Wood flour filled System Three epoxy forms the fillets. Everything else is T-88 epoxy. Observant people will note 3/4" lumber edging, 18mm plywood, and epoxy bridging the gap between plywood and brace - it's structural, and thixotropic epoxy adhesives (or straight epoxy plus additives like wood flour) don't flow out. I learned about box store birch on the baffle with its wafer thin face veneers, voids, and bad glue job (never again) and headed to the lumber yard for the rest.




The feet/baffle edges mate with lock miter joints. The blue tape is there to catch epoxy drips from the top I'd yet to glue on because epoxy soaks in and doesn't sand off. Seemed like a smart idea to verify that the tee-nuts were straight enough before I glued the top on.




Sides are joined with conventional 45 degree miters so I could trim them to fit flush with the feet/baffle after having alignment issues when I attempted to glue my perfect first two sets of sides. Using a sled you can saw to .005" precision although needing to was a mistake.




I learned that epoxy has a higher viscosity which can lead to larger glue lines on parts that mate perfectly dry although the corners look better in natural light. More clamping is needed - the places where I clamped tighter have glue lines that are close to what you'd get with PVA glues.


The big thing here is that I screwed up on figuring out assembly. If I'd thought more I'd have mated the feet to the sides and then trimmed off the excess feet thickness on the outside on my router table or with a vertical flush trim bit and then cut lock miters along the entire vertical edge instead of doing a precision cutting job to mate everything after the fact.


Obviously while I wanted a pair of sub-woofers for the bedroom, this was mostly an excuse to improve my router joinery skills and learn how to incorporate solid lumber.


 

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Quote:
Originally Posted by Health Nut /forum/post/17029442


I guess most people clamp only (no wood screws) these days?

It's nice not to fill screw holes, lets you route the results, and gives you an excuse to buy more things from the tool store that don't have power cords. What you don't see is clear packing tape on either side of the epoxy joints trimmed to fit with an X-acto knife. You can see right through it to line up joints, and once the epoxy cures you can pop it right off and not deal with squeeze-out


 

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I had my cabinetmaker overlap butt joints of 1" MDF for a 2" depth. The next cabinet he did, he just used butt joints with 2" MDF. No way to tell the two cabinets apart now that they're painted.
 
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