Air tight joints in Birch plywood?

[eyekode]

I have built speakers out of MDF before and used butt joints. If the edges are nice and straight the joints seem pretty air tight and strong (using just glue).

Can/should I use simple butt joints with Birch plywood? I don't plan on using any fasteners.

Another alternative I have is mitered joints with biscuits.

What is the recommended joint?

[Mike P.]

Butt joints are easier. Mitered joints look nicer. I'd only use mitered joints if the finish required it.

[eyekode]

Mike P. wrote:

Butt joints are easier. Mitered joints look nicer. I'd only use mitered joints if the finish required it.

So butt joints in plywood will seal well enough? I am concerned that the multiple plies will be leaky compared to MDF... I am also concerned that they will not be structurally sound (note that I prefer to not use screws, just glue which has worked fine for me with MDF).

Thanks!

[avaserfi]

With proper application of glue the seals will be air tight and structurally sound, but use of a biscuit joint as you previously mentioned would further increase strength. Is there a specific reason you are against use of screws? They will not harm the build in anyway and allow for an expedited process. Lastly, it should be noted that quality ply is actually lighter and more dense than traditional MDF.

[Mike P.]

How you built with MDF you can do with plywood. As long as the clamping time is long enough for the glue to dry, there won't be a problem.

[Geoff St. Germain]

avaserfi wrote:

Lastly, it should be noted that quality ply is actually lighter and more dense than traditional MDF.

Lighter and denser?

[eyekode]

avaserfi wrote:

Is there a specific reason you are against use of screws?

No screws because I want to leave the option of doing a stained finish. The edge of birch plywood can look interesting.

Thanks for the info!

[mgboy]

Geoff St. Germain wrote:

Lighter and denser?

I must have missed something in physics class.

[avaserfi]

Geoff St. Germain wrote:

Lighter and denser?

Sorry, lighter and more stiff. Apologies.

[a1161979]

eyekode wrote:

I have built speakers out of MDF before and used butt joints. If the edges are nice and straight the joints seem pretty air tight and strong (using just glue).

Can/should I use simple butt joints with Birch plywood? I don't plan on using any fasteners.

Another alternative I have is mitered joints with biscuits.

What is the recommended joint?

A butt join will be fine, just make sure you clamp them tight as they dry and if you want to run a bead of sealant along the interior joins. Providing you cuts are good (square) and it clamped well as it drys you wont have a problem with air leaking or strength

[aceinc]

I concur regarding using caulking, but then again for speakers I'm a belts & suspender kind o' guy. If you really want to go wild & crazy slosh some latex paint around the inside, and let 'er dry.

Paul

[Owen Bartley]

Yep, good square cuts, butt joints, glue, and lots of clamps. That should sort you out nicely with either MDF or plywood. And then as has been mentioned, it never hurts to run a bead of caulk or clue around the inside of all your corners, just to make 100% sure you're airtight.

[mdrake]

I always use liquid nails around all seems on the inside of my boxes.Just be sure the liquid nails is dry before making a spark.

Matt

[sparky77]

Regardless of the caulking you you to seal the enlosure, its a good idea not to instal the speakers for at least 48 hours as the vapors have been known to cause the adhesives in the speakers to let loose.

[eyekode]

mdrake wrote:

I always use liquid nails around all seems on the inside of my boxes.Just be sure the liquid nails is dry before making a spark.

Matt

I took this advice. Not sure I needed it, my edges were really clean this time (used a router to make sure they were all square). I used biscuits and wood glue. I also used a bead of liquid nails on the inside edge of each joint. I am pretty sure the seams are going to be the least of my air-leakage problems (cut a little too big of a cut-out for the driver ).