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Baltic Birch Expansion
Baltic Birch Expansion
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Old 16th December 2017, 05:46 PM   #11
scottjoplin is offline scottjoplin  Wales
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I can guarantee you that Baltic birch ply is dead. However, when you eat a raw carrot it is still alive
Woofer Assisted Wideband is the New Testament renounce the anachronistic acronym FAST
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Old 16th December 2017, 06:05 PM   #12
globalplayer is offline globalplayer  Germany
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If it`s dead why does it move?
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Old 16th December 2017, 08:13 PM   #13
DonVK is offline DonVK  Canada
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All wood will expand / contract with changes in humidity. There are info sources that provide the change you can expect (ie. Dimensional Stability & Flatness - Performance Panels). Its very likely the expansion rates for the birch and veneer are similar.

What kind of construction joint was used (butt, mitre, etc)
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Old 16th December 2017, 08:50 PM   #14
phase is offline phase  United States
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Yep, what he said.
That is why a mitre joint is used where it is desirable to not see any signs of the joint.
I wouldn’t have thought it would be visible either with a veneer over it the way you made yours, and would have done the same.

Is there any chance of carefully removing the veneer and sanding the offending parts a bit?
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Old 17th December 2017, 01:34 AM   #15
robert1111 is offline robert1111
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Butt joints. Seen so many butt joint builds, and never heard problems.

Yes it is possible to just sand it flat. Don't think I can remove the veneer any other way. That means, new veneer. Luckily it is super cheap, but takes a lot of time to apply and lacquer.

I'm a little bit afraid, that it might shrink or expand again. I should probably add screws to the construction.

Last edited by robert1111; 17th December 2017 at 01:41 AM.
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Old 17th December 2017, 02:41 AM   #16
benb is offline benb  United States
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Yes, the wood is dead, but the variation in humidity makes it grow and shrink, mostly in two of its three dimensions. Musical instrument makers know all about it.

You could put the future-cabinet wood in your living room or wherever these speakers will go for a few weeks/months before building, that should help. Then again, there's very low humidity in the dead of winter with central heat going, and high humidity on hot sunny days unless you use A/C. There's also Thanksgiving and Christmas eve/day and other big social holidays when all possible surfaces are cooking or have hot foods gassing off water vapor to fill the air with high humidity.

A company makes the "Dampp Chaser" system for pianos to stabilize humidity - it helps a lot with keeping the piano in tune longer, as well as extending the life of the piano itself. It's well worth the investment on all but junker pianos. This might be overkill for speaker cabinets, but then some will do anything for good sound (and good looking speakers).
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Old 17th December 2017, 02:43 AM   #17
DonVK is offline DonVK  Canada
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Butt joints are often used and they are strong but you get a change in grain pattern at the joint (side/edge).

The pics look like the top surface has its underlying front and back edges "telegraphing" through the veneer. It appears as it you can see those panel edges through the veneer. Does this occur in other areas were a panel "edge" is under the veneer?
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Old 17th December 2017, 03:23 AM   #18
paul burchell is offline paul burchell  Canada
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This reminds me of a earlier project done here where a tall multi driver speaker was constructed using stacks of ply laminated together, then steel rods where added down through the laminations and glued with apoxy. Soon after the stack cracked near the center of the stack.
Bb ply is very stable in its 2 large dimensions due to the cross lamination process but the thickness can slightly change due to humity and will telegraph throu thin commercial laminate. I would use a thicker resawen veneer to avoid this or miter the joints on the ply carcass.
Paul Burchell Fine Woodworking
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Old 17th December 2017, 06:20 AM   #19
simon7000 is offline simon7000  United States
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If you use a 45 degree miter on the corners as already mentioned, you will not have a problem. Hindsight is however not useful here. I would sand the top flat and apply another layer of vener. I suspect that the joint may still telegraph through and you may have to add a third layer.

The other issue is your Baltic birch made in Finland, Russia or China? Listed in order of quality!

Last edited by simon7000; 17th December 2017 at 06:23 AM.
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Old 17th December 2017, 08:24 AM   #20
basreflex is offline basreflex  Spain
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a true finish brand is koskisen, great stuff..
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