Solid Wood Baffles with MDF/Ply boxes?

DaveFred

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.

jhollander

My hardwood baffle plus MDF boxes have been mostly removable baffles so no issues. I've done 3-4 others that are solid hardwood attached to MDF boxes and I've had no problems. Several were MDF boxes that were veneered. A seam develops at the hardwood to MDF joint but it's not noticeable as I typically use a round over on the front baffle.

I believe the MDF is more flexible than the hardwood so I've not seen split baffles like hardwood cross grain.  I'm also using glue only construction

dcibel

I'm in the middle of building a large cabinet with a hardwood baffle and MDF box. I plan to use a gasket and bolt the baffle on rather than gluing, I did this with a previous project using bamboo baffle successfully. The bamboo I think is more like a plywood, I haven't observed any movement over the past few years from the initial build.

Additionally, I plan to put a couple battens across the back of the baffle that will then be braced to the rear panel. The battens have the grain going perpendicular to the baffle to prevent warping, this is the standard construction for many hardwood table tops. I will also finish both sides of the board to ensure that it takes on moisture equally from both sides to prevent warping and splitting.

PVA glue does have some flex, but I can't say if that's enough. The risk of splitting has to do with a lot of factors like the type of wood used and grain pattern, your home climate, how much humidity changes over the seasons, how dry and acclimated the board was prior to cutting and installation..

squamishdroc

I have done a few builds with hardwood baffles - one was bolted on and the rest have been glued on to either mdf or ply and no split baffles yet. I also feel that with a piece of wood the size of a speaker baffle you will get less movement then compared to a table top or other piece of furniture.

PWRRYD

I have installed many solid hardwood baffles on MDF and plywood boxes.  I have never glued one on.  I always use foam gasket tape and fasteners.  I really haven't noticed any movement on mine.  And I've done up to 10.5" wide baffles.

PWRRYD

Here's a link to one of my build threads:

https://diy.midwestaudio.club/discussion/comment/15269#Comment_15269

ani_101

Removable baffles...

From Bill's images from IOWA 2019

rjj45

I have done several builds with hardwood baffles. Typically use Titebond II and dowels to secure the hardwood to a 12MM Baltic Birch Ply sub-baffle. No problems noted yet, figure that even if I get a crack, the plywood sub-baffle will keep the box sealed, and the dowels might help if the glue fails. I have also applied the same technique when I use hard solid hard wood on the top and/or bottom of a veneered plywood box. 

ani_101

rjj45 said:

I have done several builds with hardwood baffles. Typically use Titebond II and dowels to secure the hardwood to a 12MM Baltic Birch Ply sub-baffle. No problems noted yet, figure that even if I get a crack, the plywood sub-baffle will keep the box sealed, and the dowels might help if the glue fails. I have also applied the same technique when I use hard solid hard wood on the top and/or bottom of a veneered plywood box. 

what do you use to seal the hardwood/plywood structure?

rjj45

ani_101 said:

rjj45 said:

I have done several builds with hardwood baffles. Typically use Titebond II and dowels to secure the hardwood to a 12MM Baltic Birch Ply sub-baffle. No problems noted yet, figure that even if I get a crack, the plywood sub-baffle will keep the box sealed, and the dowels might help if the glue fails. I have also applied the same technique when I use hard solid hard wood on the top and/or bottom of a veneered plywood box. 

what do you use to seal the hardwood/plywood structure?

Umm, if I understand correctly, I always have bare solid hard wood to bare plywood and lately use Titebond II for that layer
For finishing, I will typically use shellac followed with either poly or wipe-on oil. I basically never seal the inside of the box.
Did I answer your question?
If  you lookup some of Javad Shadzi's builds on Facebook, he uses a similar method (which is where I got my process)

ani_101

rjj45 said:

Umm, if I understand correctly, I always have bare solid hard wood to bare plywood and lately use Titebond II for that layer

For finishing, I will typically use shellac followed with either poly or wipe-on oil. I basically never seal the inside of the box.
Did I answer your question?
If  you lookup some of Javad Shadzi's builds on Facebook, he uses a similar method (which is where I got my process)

thanks, yes you did.