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Exposed ply cabinet build
Exposed ply cabinet build
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Old 12th March 2019, 05:25 PM   #1
cdurocher is offline cdurocher  Canada
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Default Exposed ply cabinet build

Hello,

I need to build a 24L passive radiator cabinet for my next speaker project. I have this idea that I'm sure somebody else has tried before, but I'm having trouble finding example builds on the net... Causing me to think maybe this isn't such a hot idea after all.

My cabinet will be 9" deep, 13" wide, and 20" high. I'd like to cut 9 x (20"x13"x1") panels out of baltic birch, use a jigsaw to cut out the insides then glue those panels together. The front and back panels would have cutouts for the drivers and stuff and would have the BB veneer on the face. The sides, top, and bottom would be exposed ply.

I have a few questions:

1) Any big downsides to this approach besides wasting more wood?
2) Is the smoothness or shape of the inside of the cabinet important as long as I get the internal volume right? (I'm planning to have average 1" thick around for a sturdy build and I was thinking of cutting out an odd shape to defeat any standing waves. Does the inside have to be smooth?)
3) I imagine these looking great. Has anybody actually done this and found differently?
4) For the front baffle, I wanted to round-over the sides and top, which would expose the ply... Has anybody done this and does it look good? It's better for sound, but if the look isn't awesome, I would just go with a square edge instead.
5) tips on sealing the inside to prevent any leaks?

Thanks!

Colin
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Old 12th March 2019, 05:50 PM   #2
badman is online now badman  United States
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Search on translam, that's how it's normally described.

1) No
2) No need for smooth, varied surface is better but only slightly as the variation will be small relative to the wavelengths in-cab.
3) They can separate with humidity and other issues can occur, but aside from that, it's a darned attractive way to build a speaker.
4) Yup. Looks awesome.
5) Your layers should be well-glued to ensure no leaks, you can use diluted woodglue as a coating for extra sealing power.
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Old 12th March 2019, 05:59 PM   #3
planet10 is offline planet10  Canada
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Exposed ply cabinet build
I’m not sure what you are describing before the questions. A box as big as you are making should have at least a brace between the back & the baffle. We use full top-bottom holey braces for that baffle. We also take the opportunity to use that brace to distribute driver reactive force to the rest of the cabinet by fitting it tight to the driver magnet.

Click the image to open in full size.

25mm BB is overkill for a box this small. 18mm is more than sufficient. We have built bigger box (but with appropriate internal structure) out of 15mm.

There are lots of examples of natural plywood boxes… try looking on the FR Forum. You’ll find even more unfinished ply boxes as people hook them up to listen before finishing and they don’t get finished :^)

Can’t find any but i know they ar eout there.

I have seen corners flat, with roundover, and with chamfers (what we typically do).

If you cut the panels well you should have no leaks,

dave
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Old 12th March 2019, 06:05 PM   #4
planet10 is offline planet10  Canada
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Exposed ply cabinet build
Now, with badmans comment, i understand that you mean translam construction.

To my mind a huge waste of material and you end up using the ply in a direction in which it is not meant to be used — so have to have thicker walls. And i have seen them “break” more often than is comfortable.

It’s only advantage is the ability to “easily” build strange shapes — expect a whole lot of sanding.. If you are doing a rectangular box do yourself a favour and just use the ply it is meant to be used.

And yes, you will find natural ply translam boxes illustrated here.

dave
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Old 12th March 2019, 06:23 PM   #5
Charles Darwin is offline Charles Darwin  United Kingdom
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Quote:
Originally Posted by badman View Post
3) They can separate with humidity...
If you are worried about that you coul use marine ply.
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Old 12th March 2019, 07:26 PM   #6
boswald is offline boswald  United States
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Exposed ply cabinet build
When Dave says a whole lot of sanding, he isn't kidding.
And you're sanding a lot of glue, and power tools will have fun with all the grain directions(and clog media very quickly).
So a lot of that whole lot o'fun will be by hand.

But if you are willing and able, it can look very cool.

Have fun, show us pictures!

p.s. seal w/epoxy!
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Old 12th March 2019, 07:53 PM   #7
Cal Weldon is offline Cal Weldon  Canada
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Exposed ply cabinet build
Yes many have made them including moi. I too used the front to back laminates rather than stacking them and the purpose was for the funky shape. I cut them wavy on the inside thinking that would help with standing waves. Turns out to be incorrect
The inside leftovers I repurposed by cutting them into fish shapes and mounting them on a cruddy old wall in back that I painted first.
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Old 12th March 2019, 08:46 PM   #8
LineSource is offline LineSource  United States
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Troels Glavensen built his Ekta mk2 cabinet with a front baffle which uses the exposed side plys of Baltic Birch across the entire baffle width.

EKTA-mkII

======
Another idea with can also reduce baffle diffraction distortion is to stack up 2-thick front baffle boards, and cut (left, top, right) 45-degree edge bevels to expose the wood plys just along the outside edges. A grill cloth could be sized to still expose these side plys.
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Old 13th March 2019, 05:56 AM   #9
hollowboy is offline hollowboy  Australia
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The easiest way to get the exposed ply look is to simply buy it, as pictured.

Your access to this site has been limited
If the link doesn't work (they are rebuilding the website), look for "MAXI EDGE PLYWOOD PANELS"

The cheapest and least wasteful way to get the exposed ply look is to DIY it from a bunch of scraps and offcuts. I did exactly this for round-overs on a current build, see post 61:

pattern control below 400Hz

I agree with Badman's answers (post 2). To prevent the problem he mentions "They can separate with humidity"

a) use waterproof glue
b) "stitch" the layers together
-by hammering dowel "nails" into predrilled, glue filled holes
OR
-with normal screws
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Old 13th March 2019, 06:24 AM   #10
DPH is offline DPH  United States
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Think about using LVL or Parallam type products. You might be able to get your hands on a few beam cutoffs. Hope you've got some serious woodworking equipment to put them to good use, but they'd be anisotropic in strength like you're hoping plus a lot less likely to delam on you.
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