Hello
I built speakers few months ago. I made the cabinets out of moisture-proof 18 mm baltic birch plywood, Veneered and lacquered. It came out absolutely perfect. I did not use screws, only PVA glue. AND now, I noticed that the seams have expanded a bit. The front and rear plates have expanded, so the seams can be seen under correct lighting. Nothing too bad, just the perfect speakers are not perfect any more.
Is this a common problem?
How can I make sure it wont happen again with my future builds?
Thanks
I built speakers few months ago. I made the cabinets out of moisture-proof 18 mm baltic birch plywood, Veneered and lacquered. It came out absolutely perfect. I did not use screws, only PVA glue. AND now, I noticed that the seams have expanded a bit. The front and rear plates have expanded, so the seams can be seen under correct lighting. Nothing too bad, just the perfect speakers are not perfect any more.
Is this a common problem?
How can I make sure it wont happen again with my future builds?
Thanks
Do you mean the seams in the veneer? Pictures would help. I've not heard of the plys separating or expanding
I suggest gluing clamping then drive a 1 1/4" screw every 2 or 3 inches apart. I use ceramic coated robinson decking screws. Drywall screws bite well and surface flush without a countersink bit but I got tired of snapping them off.
Yes, can see the lines, are those dips or ridges? I'm thinking the glue has shrunk as it's dried and pulled the veneer down
It is not shrinking glue. I can see and feel that the front and back plate have expanded.
Gotcha, well, sorry I've never heard of that happening with Baltic birch ply, you are sure that's what it was, it had 13 plys?
Yes 13. This is probably best picture. Can clearly see, that the bottom panel is wider, and they were all flush in the beginning. They have been in the house, so no humid conditions, or temperature fluctuations. I did build them in a bit colder place, but took them inside for a week, before I veneered them, and they expanded suddenly after 2 months time, sitting at my desk.
Next time probably going to use screws, like suggested. But it sure is something that I did not expect to happen. It took me 40 hours to build them. So I´m quite disappointed.
Next time probably going to use screws, like suggested. But it sure is something that I did not expect to happen. It took me 40 hours to build them. So I´m quite disappointed.
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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
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)
What kind of construction joint was used (butt, mitre, etc)
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?
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?
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.
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.
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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).
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).
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?
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?
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.
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.
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!
The other issue is your Baltic birch made in Finland, Russia or China? Listed in order of quality!
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