Hello,
What have been peoples experiences/thoughts on combining solid wood baffles with sheet good (MDF or Ply) boxes?
My 30+ years of woodworking experience tells me that such a large cross grain joint is a bad idea that can only end with the baffle splitting. Yet, I have seen countless examples of such construction posted on the Interwebs.
I know one thing that would help for sure, and that is "ripping and flipping" the wood, so you end up with a quartersawn baffle (of all the lumber cuts quartersawn has the least amount of movement).
Are people getting lucky?
Is it that we live in climate controlled houses where the humidity is fairly constant?
Has anyone, for example built a pair of speakers in Nevada (low humidity) and then moved to Florida (high humidity)?
Is it that the modern PVA glues that we use have some "give" to them?
Are there any guidelines people have used for how wide a solid wood baffle they would on an MDF/ply box?
Does the thickness of the baffle matter?
Any failure examples where the baffle did crack?
What about where the baffles were a glue up of layers of plywood? With this type of baffle, you would think there would still be movement as the layers are not constrained in their "thickness", just in their width and length.
What are your thoughts?
Thank you,
David.
What have been peoples experiences/thoughts on combining solid wood baffles with sheet good (MDF or Ply) boxes?
My 30+ years of woodworking experience tells me that such a large cross grain joint is a bad idea that can only end with the baffle splitting. Yet, I have seen countless examples of such construction posted on the Interwebs.
I know one thing that would help for sure, and that is "ripping and flipping" the wood, so you end up with a quartersawn baffle (of all the lumber cuts quartersawn has the least amount of movement).
Are people getting lucky?
Is it that we live in climate controlled houses where the humidity is fairly constant?
Has anyone, for example built a pair of speakers in Nevada (low humidity) and then moved to Florida (high humidity)?
Is it that the modern PVA glues that we use have some "give" to them?
Are there any guidelines people have used for how wide a solid wood baffle they would on an MDF/ply box?
Does the thickness of the baffle matter?
Any failure examples where the baffle did crack?
What about where the baffles were a glue up of layers of plywood? With this type of baffle, you would think there would still be movement as the layers are not constrained in their "thickness", just in their width and length.
What are your thoughts?
Thank you,
David.
I'll give you a tip about solid wood slabs. When you prepare lumber for edge gluing you don't want the pieces to meet in the center. In other words, the edges are tapered like a "bow" so when you clamp, the center of the assembly needs all the pressure. [x(o)x(o)x(o)x]
"x" is each board "o" space between each board. When the wood slab is put into service, the ends will give off moisture. Since you have allowed for the shrinkage, with the bowed edges, the slab will just relax instead of splitting. The space need only be 1/16" give or take.
Now if you're going to lay this over another sub-panel, like plywood or MDF, you should only glue one spot like the center few inches. The lumber slab will still want to move and it can at both outside edges. To hold these edges to the sub-panel you want to use screws from behind .. so through the sub-panel into the lumber slab. The holes for the screws in the sub-panel need to be either slotted or larger so the screws can slide a bit. A fender washer under a panhead would work well. Now the lumber slab can move without distorting.
"x" is each board "o" space between each board. When the wood slab is put into service, the ends will give off moisture. Since you have allowed for the shrinkage, with the bowed edges, the slab will just relax instead of splitting. The space need only be 1/16" give or take.
Now if you're going to lay this over another sub-panel, like plywood or MDF, you should only glue one spot like the center few inches. The lumber slab will still want to move and it can at both outside edges. To hold these edges to the sub-panel you want to use screws from behind .. so through the sub-panel into the lumber slab. The holes for the screws in the sub-panel need to be either slotted or larger so the screws can slide a bit. A fender washer under a panhead would work well. Now the lumber slab can move without distorting.
Somewhat dependent on the baffle size. I made a pair of Zaph's Seas speakers using teak over MDF. I planed teak to 3/4" square and 'framed' the MDF panel, then glued resawn 1/4" teak to it. That allowed me to route a wide chamfer all around without exposing MDF.
That said, that baffle isn't very wide (the woofer is what? 7"?) If I did it on a wider baffle, I think I'd balance the baffle, by putting the hardwood on both sides of the MDF.
That said, that baffle isn't very wide (the woofer is what? 7"?) If I did it on a wider baffle, I think I'd balance the baffle, by putting the hardwood on both sides of the MDF.
There is a recent thread which talks about this very subject...
https://www.diyaudio.com/forums/multi-way/356039-wood-combination-3-speaker.html#post6243757
https://www.diyaudio.com/forums/multi-way/356039-wood-combination-3-speaker.html#post6243757
I think there are many threads here about this subject.
However I used once a solid wood baffle. The implementation was successfully, without cracks even after many years, and I ascribed this to two conditions:
- baffle was relatively small (some 20x30 cm),
- and more importantly, the baffle isn't glued but bolted to the enclosure, and made airtight with sealing tape.
Ralf
However I used once a solid wood baffle. The implementation was successfully, without cracks even after many years, and I ascribed this to two conditions:
- baffle was relatively small (some 20x30 cm),
- and more importantly, the baffle isn't glued but bolted to the enclosure, and made airtight with sealing tape.
Ralf