Regarding material and thickness;
I have been using half inch chipboard, so just wondering?
Half inch chip board would be fine.....as long as you're using three or four layers.
With too flimsy a baffle, the driver can exert enough force on the baffle that the baffle itself will "color" the sound, almost like the baffle is another cone.
Mass, mass, mass.... and lots of it.
Some fellas have build baffles with cavities inside that can be filled with sand. This helps to "waste" the energy, and nullify it's effects.
I've heard talk of concrete used, but haven't see anybody actually use it. The common concern is that it would ring like a bell.
Maybe some concrete backer board laminated to a layer of wood with Green Glue in between. That should be dead enough.
Personally, two layers of 3/4" plywood glued together with "Titebond II" work well for me.
There's also some folks that believe a long, slow curve from the front face to the rear face of the baffle should be an exaggerated radius. Google the words "open baffle edge diffraction", you'll find more information than you can read in a single day.
Hope that helps.
Bob
