# Double Dado joint with 1/2" plywood?



## Chris Curl (Feb 13, 2012)

Is a double dado joint strong in 1/2" thick baltic birch plywood for a sub-woofer, or should it only be done with thicker ply?

Or should it not be done with plywood at all?


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## Cherryville Chuck (Sep 28, 2010)

I'm not sure what you mean by a double dado joint. Are you talking about installing a partition inside the box or joining the edges?


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## jw2170 (Jan 24, 2008)

Chris Curl said:


> Is a double dado joint strong in 1/2" thick baltic birch plywood for a sub-woofer, or should it only be done with thicker ply?
> 
> Or should it not be done with plywood at all?


If you are referring to this joint, my test drawers were made from 12mm ply and seem to be strong enough... I think 1\2" ply would be strong enough for a sub-woofer box.


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## jschaben (Jun 21, 2009)

jw2170 said:


> If you are referring to this joint, my test drawers were made from 12mm ply and seem to be strong enough... I think 1\2" ply would be strong enough for a sub-woofer box.


Hi James, I've been building all my drawers with that joint lately but I have the end piece the other way, the outside is flush with the corner. Am I backwards on that. Don't see where it makes much difference either way, maybe a little bit of inside room.


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## jw2170 (Jan 24, 2008)

*my bad....*



jschaben said:


> Hi James, I've been building all my drawers with that joint lately but I have the end piece the other way, the outside is flush with the corner. Am I backwards on that. Don't see where it makes much difference either way, maybe a little bit of inside room.


Hi John,

Yes, the outside is supposed to be flush. I was not paying attention when I glued it up. :bad:

The other end is flush.

You are right in that for a drawer it is not significant, but for a box it is.....

I just used the joint that Bob & Rick use on many of their shows and I used the 1\4" Oak Park spacer fence.


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## GulfcoastGuy (Feb 27, 2012)

Not sure of your design but 1/2 inch ply will not be rigid enough for a good sub. The box will give and you'll probably lose a good bit definition. Also MDF is preferred as it it less resonant and more dimensional stable. 3/4" MDF minimum all around, with 3/4" MDF cross bracing. The exception is the baffle; minimum 1-1/2" MDF (2 x 3/4", with faces glued together). Check out some of the speaker designs Here for ideas. And don't forget the floor spikes. They will make a difference.

GCG


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## Cherryville Chuck (Sep 28, 2010)

My son has made many speaker boxes and he also only used 3/4 mdf. His favorite glue was either PL 400 or 500. Holds very well and seals all the joints as well. They are capable of bridging a 3/8" gap. He just used butt joints and screws and he never had one come apart.


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## iand (Jan 3, 2012)

I agree with using MDF - it worked great for my son's box


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## 57759 (Apr 8, 2011)

using plywood I would think the end of the one component would be real fragile, until glued and chip out may be a problem. With the drawer construction style of DD James supplied a pic of, not a problem.


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## GulfcoastGuy (Feb 27, 2012)

This may be of help, too.

Subwoofer Box Enclosure Design Calculator - Sealed Ported Bandpass Closed Vented

Just so you get the most from your labor.


GCG


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## Chris Curl (Feb 13, 2012)

thanks for the replys. i haven't seen them yet, but apparently the plans he has calls for baltic birch plywood. more when i see the plans he got.


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## Gene Howe (Jul 10, 2007)

To your original question: 1/2" BB is quite adequate for the joint you describe. As to it's use as a speaker enclosure, I'd think 3/4 MDF would be more suitable.


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